Sample records for magnetic field strength

  1. Dependence of Brownian and Néel relaxation times on magnetic field strength

    SciTech Connect (OSTI)

    Deissler, Robert J., E-mail: rjd42@case.edu; Wu, Yong; Martens, Michael A. [Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106 (United States)] [Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106 (United States)

    2014-01-15T23:59:59.000Z

    Purpose: In magnetic particle imaging (MPI) and magnetic particle spectroscopy (MPS) the relaxation time of the magnetization in response to externally applied magnetic fields is determined by the Brownian and Néel relaxation mechanisms. Here the authors investigate the dependence of the relaxation times on the magnetic field strength and the implications for MPI and MPS. Methods: The Fokker–Planck equation with Brownian relaxation and the Fokker–Planck equation with Néel relaxation are solved numerically for a time-varying externally applied magnetic field, including a step-function, a sinusoidally varying, and a linearly ramped magnetic field. For magnetic fields that are applied as a step function, an eigenvalue approach is used to directly calculate both the Brownian and Néel relaxation times for a range of magnetic field strengths. For Néel relaxation, the eigenvalue calculations are compared to Brown's high-barrier approximation formula. Results: The relaxation times due to the Brownian or Néel mechanisms depend on the magnitude of the applied magnetic field. In particular, the Néel relaxation time is sensitive to the magnetic field strength, and varies by many orders of magnitude for nanoparticle properties and magnetic field strengths relevant for MPI and MPS. Therefore, the well-known zero-field relaxation times underestimate the actual relaxation times and, in particular, can underestimate the Néel relaxation time by many orders of magnitude. When only Néel relaxation is present—if the particles are embedded in a solid for instance—the authors found that there can be a strong magnetization response to a sinusoidal driving field, even if the period is much less than the zero-field relaxation time. For a ferrofluid in which both Brownian and Néel relaxation are present, only one relaxation mechanism may dominate depending on the magnetic field strength, the driving frequency (or ramp time), and the phase of the magnetization relative to the applied magnetic field. Conclusions: A simple treatment of Néel relaxation using the common zero-field relaxation time overestimates the relaxation time of the magnetization in situations relevant for MPI and MPS. For sinusoidally driven (or ramped) systems, whether or not a particular relaxation mechanism dominates or is even relevant depends on the magnetic field strength, the frequency (or ramp time), and the phase of the magnetization relative to the applied magnetic field.

  2. Effects of magnetic field strength on the low frequency oscillation in Hall thrusters

    SciTech Connect (OSTI)

    Wang Chunsheng; Wei Liqiu; Ning Zhongxi; Yu Daren [Laboratory of Plasma Propulsion, Mail Box 458, Harbin Institute of Technology, Harbin 150001 (China)

    2011-01-15T23:59:59.000Z

    In order to study the effect of magnetic field strength on low frequency oscillation in Hall thrusters, experiments were carried out with different operating parameters. Experimental results show that the effect of magnetic field strength on the low frequency oscillation changes with operating parameters. In the decline zone of magnetoampere characteristic curve, low frequency oscillation increases with the increase of magnetic field strength at low mass flow rate, while decreases with the increase of magnetic field strength at high mass flow rate. With further experiments and numerical simulations, it is found that the change of electron current at low mass flow rate and the change of ion current at high mass flow rate account for the variations of low frequency oscillation. Finally, the physical analysis is performed.

  3. A simple model for the distribution of quiet Sun magnetic field strengths

    E-Print Network [OSTI]

    J. Sanchez Almeida

    2006-12-11T23:59:59.000Z

    We derive a first order linear differential equation describing the shape of the probability density function of magnetic field strengths in the quiet Sun (PDF). The modeling is very schematic. It considers convective motions which continuously supply and withdraw magnetic structures. In addition, a magnetic amplification mechanism increases the field strength up to a threshold that cannot be exceeded. These three basic ingredients provide PDFs in good agreement with the PDFs produced by realistic numerical simulations of magneto convection, as well as with quiet Sun PDFs inferred from observations. In particular, the distribution is approximately lognormal, and it produces an excess of magnetic fields (i.e., a 'hump' in the distribution) right before the maximum field strength. The success of this simple model may indicate that only a few basic ingredients shape the quiet Sun PDF. Our approach provides a concise parametric representation of the PDF, as required to develop automatic methods of diagnostics.

  4. On the Collective Magnetic Field Strength and Vector Structure of Dark Umbral Cores Measured by the Hinode Spectropolarimeter

    E-Print Network [OSTI]

    Schad, T A

    2015-01-01T23:59:59.000Z

    We study 7530 sunspot umbrae and pores measured by the Hinode Spectropolarimeter (SP) between November 2006 and November 2012. We primarily seek confirmation of the long term secular decrease in the mean magnetic field strength of sunspot umbrae found by Penn and Livingston (2011, IAU Symp. 273,126) between 1998 and 2011. The excellent SP photometric properties and full vector magnetic field determinations from full-Stokes Milne-Eddington inversions are used to address the interrelated properties of the magnetic field strength and brightness temperature for all umbral cores. We find non-linear relationships between magnetic field strength and umbral temperature (and continuum contrast), as well as between umbral radius and magnetic field strength. Using disambiguated vector data, we find that the azimuths measured in the umbral cores reflect an organization weakly influenced by Joy's law. The large selection of umbrae displays a log-normal size spectrum similar to earlier solar cycles. Influenced by the ampli...

  5. Radio emission from exoplanets: the role of the stellar coronal density and magnetic field strength

    E-Print Network [OSTI]

    M. Jardine; A. C. Cameron

    2008-08-21T23:59:59.000Z

    The search for radio emission from extra-solar planets has so far been unsuccessful. Much of the effort in modelling the predicted emission has been based on the analogy with the well-known emission from Jupiter. Unlike Jupiter, however, many of the targets of these radio searches are so close to their parent stars that they may well lie inside the stellar magnetosphere. For these close-in planets we determine which physical processes dominate the radio emission and compare our results to those for large-orbit planets that are immersed in the stellar wind. We have modelled the reconnection of the stellar and planetary magnetic fields. We calculate the extent of the planetary magnetosphere if it is in pressure balance with its surroundings and determine the conditions under which reconnection of the stellar and planetary magnetic fields could provide the accelerated electrons necessary for the predicted radio emission. We show that received radio fluxes of tens of mJy are possible for exoplanets in the solar neighbourhood that are close to their parent stars if their stars have surface field strengths above 1-10G. We show that for these close-in planets, the power of the radio emission depends principally on the ratio (Nc/B^{1/3})^2 where Nc is the density at the base of the stellar corona, and B is the stellar surface magnetic field strength. Radio emission is most likely to be detected from planets around stars with high-density coronae, which are therefore likely to be bright X-ray sources. The dependence of stellar coronal density on stellar rotation rate and effective temperature is crucial in predicting radio fluxes from exoplanets.

  6. Influence of magnetic field strength on potential well in the ionization stage of a double stage Hall thruster

    SciTech Connect (OSTI)

    Yu Daren; Song Maojiang; Liu Hui; Zhang Xu; Li Hong [Lab of Plasma Propulsion, Mail Box 458, Harbin Institute of Technology, Harbin 150001 (China)

    2012-07-15T23:59:59.000Z

    Similar to a single stage Hall thruster, the magnetic field, which controls electron trajectory and electric field distribution, is the most important factor determining the performance of a double stage Hall thruster. Especially, a potential well, which is helpful to reduce the ion loss on the thruster walls, is shaped in the ionization stage due to the existence of an annular magnetic field topology there. In this paper, the influence of magnetic field strength in the ionization stage on the potential well is researched with both experiments and particle-in-cell simulations. It is found that the depth of potential well increases with the magnetic field strength as a result of enhanced magnetic confinement and lowered electron conductivity. Consequently, the plasma density as well as the ion current entering the acceleration stage increases. However, an excessive magnetic field strength leads to an excess of ion loss on the walls of the acceleration stage. Therefore, there is an appropriate magnetic field strength in the ionization stage that results in a proper potential well and consequently an optimal performance of a double stage Hall thruster.

  7. Energy Spectrum of a Relativistic Two-dimensional Hydrogen-like Atom in a Constant Magnetic Field of arbitrary strength

    E-Print Network [OSTI]

    V. M. Villalba; R. Pino

    2001-01-23T23:59:59.000Z

    We compute, via a variational mixed-base method, the energy spectrum of a two dimensional relativistic atom in the presence of a constant magnetic field of arbitrary strength. The results are compared to those obtained in the non-relativistic and spinless case. We find that the relativistic spectrum does not present $s$ states.

  8. Monte Carlo characterization of skin doses in 6 MV transverse field MRI-linac systems: Effect of field size, surface orientation, magnetic field strength, and exit bolus

    SciTech Connect (OSTI)

    Oborn, B. M.; Metcalfe, P. E.; Butson, M. J.; Rosenfeld, A. B. [Illawarra Cancer Care Centre (ICCC), Wollongong, New South Wales 2500 (Australia) and Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, New South Wales 2500 (Australia); Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, New South Wales 2500 (Australia); Illawarra Cancer Care Centre (ICCC), Wollongong, New South Wales 2500 (Australia); Centre for Medical Radiation Physics (CMRP), University of Wollongong, Wollongong, New South Wales 2500 (Australia)

    2010-10-15T23:59:59.000Z

    Purpose: The main focus of this work is to continue investigations into the Monte Carlo predicted skin doses seen in MRI-guided radiotherapy. In particular, the authors aim to characterize the 70 {mu}m skin doses over a larger range of magnetic field strength and x-ray field size than in the current literature. The effect of surface orientation on both the entry and exit sides is also studied. Finally, the use of exit bolus is also investigated for minimizing the negative effects of the electron return effect (ERE) on the exit skin dose. Methods: High resolution GEANT4 Monte Carlo simulations of a water phantom exposed to a 6 MV x-ray beam (Varian 2100C) have been performed. Transverse magnetic fields of strengths between 0 and 3 T have been applied to a 30x30x20 cm{sup 3} phantom. This phantom is also altered to have variable entry and exit surfaces with respect to the beam central axis and they range from -75 deg. to +75 deg. The exit bolus simulated is a 1 cm thick (water equivalent) slab located on the beam exit side. Results: On the entry side, significant skin doses at the beam central axis are reported for large positive surface angles and strong magnetic fields. However, over the entry surface angle range of -30 deg. to -60 deg., the entry skin dose is comparable to or less than the zero magnetic field skin dose, regardless of magnetic field strength and field size. On the exit side, moderate to high central axis skin dose increases are expected except at large positive surface angles. For exit bolus of 1 cm thickness, the central axis exit skin dose becomes an almost consistent value regardless of magnetic field strength or exit surface angle. This is due to the almost complete absorption of the ERE electrons by the bolus. Conclusions: There is an ideal entry angle range of -30 deg. to -60 deg. where entry skin dose is comparable to or less than the zero magnetic field skin dose. Other than this, the entry skin dose increases are significant, especially at higher magnetic fields. On the exit side there is mostly moderate to high skin dose increases for 0.2-3 T with the only exception being large positive angles. Exit bolus of 1 cm thickness will have a significant impact on lowering such exit skin dose increases that occur as a result of the ERE.

  9. Permanent-magnet multipole with adjustable strength

    DOE Patents [OSTI]

    Halbach, K.

    1982-09-20T23:59:59.000Z

    Two or more magnetically soft pole pieces are symmetrically positioned along a longitudinal axis to provide a magnetic field within a space defined by the pole pieces. Two or more permanent magnets are mounted to an external magnetically-soft cylindrical sleeve which rotates to bring the permanent magnets into closer coupling with the pole pieces and thereby adjustably control the field strength of the magnetic field produced in the space defined by the pole pieces. The permanent magnets are preferably formed of rare earth cobalt (REC) material which has a high remanent magnetic field and a strong coercive force. The pole pieces and the permanent magnets have corresponding cylindrical surfaces which are positionable with respect to each other to vary the coupling there between. Auxiliary permanent magnets are provided between the pole pieces to provide additional magnetic flux to the magnetic field without saturating the pole pieces.

  10. Permanent magnet multipole with adjustable strength

    DOE Patents [OSTI]

    Halbach, Klaus (Berkeley, CA)

    1985-01-01T23:59:59.000Z

    Two or more magnetically soft pole pieces are symmetrically positioned along a longitudinal axis to provide a magnetic field within a space defined by the pole pieces. Two or more permanent magnets are mounted to an external magnetically-soft cylindrical sleeve which rotates to bring the permanent magnets into closer coupling with the pole pieces and thereby adjustably control the field strength of the magnetic field produced in the space defined by the pole pieces. The permanent magnets are preferably formed of rare earth cobalt (REC) material which has a high remanent magnetic field and a strong coercive force. The pole pieces and the permanent magnets have corresponding cylindrical surfaces which are positionable with respect to each other to vary the coupling therebetween. Auxiliary permanent magnets are provided between the pole pieces to provide additional magnetic flux to the magnetic field without saturating the pole pieces.

  11. The dependence of potential well formation on the magnetic field strength and electron injection current in a polywell device

    SciTech Connect (OSTI)

    Cornish, S., E-mail: cornish@physics.usyd.edu.au; Gummersall, D.; Carr, M.; Khachan, J. [School of Physics, The University of Sydney, Sydney, NSW 2006 (Australia)

    2014-09-15T23:59:59.000Z

    A capacitive probe has been used to measure the plasma potential in a polywell device in order to observe the dependence of potential well formation on magnetic field strength, electron injection current, and polywell voltage bias. The effectiveness of the capacitive probe in a high energy electron plasma was determined by measuring the plasma potential of a planar diode with an axial magnetic field. The capacitive probe was translated along the axis of one of the field coils of the polywell, and the spatial profile of the potential well was measured. The confinement time of electrons in the polywell was estimated with a simple analytical model which used the experimentally observed potential well depths, as well as a simulation of the electron trajectories using particle orbit theory.

  12. Can Images Obtained With High Field Strength Magnetic Resonance Imaging Reduce Contouring Variability of the Prostate?

    SciTech Connect (OSTI)

    Usmani, Nawaid, E-mail: Nawaid.Usmani@albertahealthservices.ca [Department of Radiation Oncology, Cross Cancer Institute, Edmonton, AB (Canada); Department of Oncology, University of Alberta, Edmonton, AB (Canada); Sloboda, Ron [Department of Oncology, University of Alberta, Edmonton, AB (Canada); Department of Medical Physics, Cross Cancer Institute, Edmonton, AB (Canada); Kamal, Wafa [Department of Radiation Oncology, Cross Cancer Institute, Edmonton, AB (Canada); Ghosh, Sunita [Department of Oncology, University of Alberta, Edmonton, AB (Canada); Department of Experimental Oncology, Cross Cancer Institute, Edmonton, AB (Canada); Pervez, Nadeem; Pedersen, John; Yee, Don; Danielson, Brita; Murtha, Albert; Amanie, John [Department of Radiation Oncology, Cross Cancer Institute, Edmonton, AB (Canada); Department of Oncology, University of Alberta, Edmonton, AB (Canada); Monajemi, Tara [Department of Medical Physics, Cross Cancer Institute, Edmonton, AB (Canada)

    2011-07-01T23:59:59.000Z

    Purpose: The objective of this study is to determine whether there is less contouring variability of the prostate using higher-strength magnetic resonance images (MRI) compared with standard MRI and computed tomography (CT). Methods and Materials: Forty patients treated with prostate brachytherapy were accrued to a prospective study that included the acquisition of 1.5-T MR and CT images at specified time points. A subset of 10 patients had additional 3.0-T MR images acquired at the same time as their 1.5-T MR scans. Images from each of these patients were contoured by 5 radiation oncologists, with a random subset of patients repeated to quantify intraobserver contouring variability. To minimize bias in contouring the prostate, the image sets were placed in folders in a random order with all identifiers removed from the images. Results: Although there was less interobserver contouring variability in the overall prostate volumes in 1.5-T MRI compared with 3.0-T MRI (p < 0.01), there was no significant differences in contouring variability in the different regions of the prostate between 1.5-T MRI and 3.0-T MRI. MRI demonstrated significantly less interobserver contouring variability in both 1.5-T and 3.0-T compared with CT in overall prostate volumes (p < 0.01, p = 0.01), with the greatest benefits being appreciated in the base of the prostate. Overall, there was less intraobserver contouring variability than interobserver contouring variability for all of the measurements analyzed. Conclusions: Use of 3.0-T MRI does not demonstrate a significant improvement in contouring variability compared with 1.5-T MRI, although both magnetic strengths demonstrated less contouring variability compared with CT.

  13. The influence of magnetic field strength in ionization stage on ion transport between two stages of a double stage Hall thruster

    SciTech Connect (OSTI)

    Yu Daren; Song Maojiang; Li Hong; Liu Hui; Han Ke [Lab of Plasma Propulsion, Mail Box 458, Harbin Institute of Technology, Harbin 150001 (China)

    2012-11-15T23:59:59.000Z

    It is futile for a double stage Hall thruster to design a special ionization stage if the ionized ions cannot enter the acceleration stage. Based on this viewpoint, the ion transport under different magnetic field strengths in the ionization stage is investigated, and the physical mechanisms affecting the ion transport are analyzed in this paper. With a combined experimental and particle-in-cell simulation study, it is found that the ion transport between two stages is chiefly affected by the potential well, the potential barrier, and the potential drop at the bottom of potential well. With the increase of magnetic field strength in the ionization stage, there is larger plasma density caused by larger potential well. Furthermore, the potential barrier near the intermediate electrode declines first and then rises up while the potential drop at the bottom of potential well rises up first and then declines as the magnetic field strength increases in the ionization stage. Consequently, both the ion current entering the acceleration stage and the total ion current ejected from the thruster rise up first and then decline as the magnetic field strength increases in the ionization stage. Therefore, there is an optimal magnetic field strength in the ionization stage to guide the ion transport between two stages.

  14. Heat treatment and Magnetic Field Procedure A 32mm diameter bore resistive magnet with a 33T maximum field strength at the National High

    E-Print Network [OSTI]

    Cambridge, University of

    -heating coil set-up has been designed to heat and cool the specimen while inside the bore of the magnetC/s to the annealing temperature. A 3-minute hold at 1000ºC was performed to fully transform the initial microstructure for the field to reach 30T. Specimen cooling was controlled via feedback loop such that by decreasing power

  15. Magnetic Field Safety Magnetic Field Safety

    E-Print Network [OSTI]

    McQuade, D. Tyler

    Magnetic Field Safety Training #12;Magnetic Field Safety Strong Magnetic Fields exist around energized magnets. High magnetic fields alone are a recognized hazard only for personnel with certain medical conditions such as pacemakers, magnetic implants, or embedded shrapnel. In addition, high magnetic

  16. Ion kinetic energy conservation and magnetic field strength constancy in multi-fluid solar wind Alfv\\'enic turbulence

    E-Print Network [OSTI]

    Matteini, L; Pantellini, F; Velli, M; Schwartz, S J

    2015-01-01T23:59:59.000Z

    We investigate properties of the plasma fluid motion in the large amplitude low frequency fluctuations of highly Alfv\\'enic fast solar wind. We show that protons locally conserve total kinetic energy when observed from an effective frame of reference comoving with the fluctuations. For typical properties of the fast wind, this frame can be reasonably identified by alpha particles, which, owing to their drift with respect to protons at about the Alfv\\'en speed along the magnetic field, do not partake in the fluid low frequency fluctuations. Using their velocity to transform proton velocity into the frame of Alfv\\'enic turbulence, we demonstrate that the resulting plasma motion is characterized by a constant absolute value of the velocity, zero electric fields, and aligned velocity and magnetic field vectors as expected for unidirectional Alfv\\'enic fluctuations in equilibrium. We propose that this constraint, via the correlation between velocity and magnetic field in Alfv\\'enic turbulence, is at the origin of ...

  17. Sco X-1 and Cyg X-1: Determination of Strength and Structure of Magnetic Field in the Nearest Environment of Accreting Compact Stars

    E-Print Network [OSTI]

    Yu. N. Gnedin; N. A. Silant'ev; L. G. Titarchuk

    2002-07-30T23:59:59.000Z

    We estimated the magnetic field strength of compact stars in X-ray binaries Sco X-1 and Cyg X-1, via various methods of determination of magnetic fields. For Sco X-1 we used three independent methods. One of them is based on the correct account of the Faraday rotation of polarization plane in the process of electron scattering of X-rays from accreting neutron stars. Numerical calculations are made with use of first X-rays polarimetric data presented by Long et al. (1979). Other original method of determing the magnetic field developed by Titarchuk at al. (2001) is based on observed quasi-periodic oscillations (QPO) frequencies in X-ray binaries that can be considered as magnetoacoustic oscillations of boundary layer near a neutron star. The optical polarimetric data obtained in 70-th have been also used for estimation of magnetic field of the neutron star in Sco X-1 and of nearest environment around the black hole in Cyg X-1.

  18. Performance of a static-anode/flat-panel x-ray fluoroscopy system in a diagnostic strength magnetic field: A truly hybrid x-ray/MR imaging system

    SciTech Connect (OSTI)

    Fahrig, R.; Wen, Z.; Ganguly, A.; DeCrescenzo, G.; Rowlands, J.A.; Stevens, G.M.; Saunders, R.F.; Pelc, N.J. [Department of Radiology, Stanford University, Stanford, California 94305 (United States); Department of Radiology and Department of Physics, Stanford University, Stanford, California 94305 (United States); Department of Radiology, Stanford University, Stanford, California 94305 (United States); Sunnybrook and Women's Health Sciences Center and Medical Biophysics, University of Toronto, 2075 Bayview Avenue, Toronto, Ontario M4N 3M5 (Canada); GE Healthcare, Schenectady, Wisconsin (United States); Department of Radiology, Stanford University, Stanford, California 94305 (United States)

    2005-06-15T23:59:59.000Z

    Minimally invasive procedures are increasing in variety and frequency, facilitated by advances in imaging technology. Our hybrid imaging system (GE Apollo{sup TM} flat panel, custom Brand x-ray static anode x-ray tube, GE Lunar high-frequency power supply and 0.5 T Signa SP{sup TM}) provides both x-ray and MR imaging capability to guide complex procedures without requiring motion of the patient between two distant gantries. The performance of the x-ray tube in this closely integrated system was evaluated by modeling and measuring both the response of the filament to an externally applied field and the behavior of the electron beam for field strengths and geometries of interest. The performance of the detector was assessed by measuring the slanted-edge modulation transfer function (MTF) and when placed at zero field and at 0.5 T. Measured resonant frequencies of filaments can be approximated using a modified vibrating beam model, and were at frequencies well below the 25 kHz frequency of our generator for our filament geometry. The amplitude of vibration was not sufficient to cause shorting of the filament during operation within the magnetic field. A simple model of electrons in uniform electric and magnetic fields can be used to estimate the deflection of the electron beam on the anode for the fields of interest between 0.2 and 0.5 T. The MTF measured at the detector and the DQE showed no significant difference inside and outside of the magnetic field. With the proper modifications, an x-ray system can be fully integrated with a MR system, with minimal loss of image quality. Any x-ray tube can be assessed for compatibility when placed at a particular location within the field using the models. We have also concluded that a-Si electronics are robust against magnetic fields. Detailed knowledge of the x-ray system installation is required to provide estimates of system operation.

  19. Optical sensor of magnetic fields

    DOE Patents [OSTI]

    Butler, M.A.; Martin, S.J.

    1986-03-25T23:59:59.000Z

    An optical magnetic field strength sensor for measuring the field strength of a magnetic field comprising a dilute magnetic semi-conductor probe having first and second ends, longitudinally positioned in the magnetic field for providing Faraday polarization rotation of light passing therethrough relative to the strength of the magnetic field. Light provided by a remote light source is propagated through an optical fiber coupler and a single optical fiber strand between the probe and the light source for providing a light path therebetween. A polarizer and an apparatus for rotating the polarization of the light is provided in the light path and a reflector is carried by the second end of the probe for reflecting the light back through the probe and thence through the polarizer to the optical coupler. A photo detector apparatus is operably connected to the optical coupler for detecting and measuring the intensity of the reflected light and comparing same to the light source intensity whereby the magnetic field strength may be calculated.

  20. Bipolar pulse field for magnetic refrigeration

    DOE Patents [OSTI]

    Lubell, Martin S. (Oak Ridge, TN)

    1994-01-01T23:59:59.000Z

    A magnetic refrigeration apparatus includes first and second steady state magnets, each having a field of substantially equal strength and opposite polarity, first and second bodies made of magnetocaloric material disposed respectively in the influence of the fields of the first and second steady state magnets, and a pulsed magnet, concentric with the first and second steady state magnets, and having a field which cycles between the fields of the first and second steady state magnets, thereby cyclically magnetizing and demagnetizing and thus heating and cooling the first and second bodies. Heat exchange apparatus of suitable design can be used to expose a working fluid to the first and second bodies of magnetocaloric material. A controller is provided to synchronize the flow of working fluid with the changing states of magnetization of the first and second bodies.

  1. Bipolar pulse field for magnetic refrigeration

    DOE Patents [OSTI]

    Lubell, M.S.

    1994-10-25T23:59:59.000Z

    A magnetic refrigeration apparatus includes first and second steady state magnets, each having a field of substantially equal strength and opposite polarity, first and second bodies made of magnetocaloric material disposed respectively in the influence of the fields of the first and second steady state magnets, and a pulsed magnet, concentric with the first and second steady state magnets, and having a field which cycles between the fields of the first and second steady state magnets, thereby cyclically magnetizing and demagnetizing and thus heating and cooling the first and second bodies. Heat exchange apparatus of suitable design can be used to expose a working fluid to the first and second bodies of magnetocaloric material. A controller is provided to synchronize the flow of working fluid with the changing states of magnetization of the first and second bodies. 2 figs.

  2. Fluorescent lamp with static magnetic field generating means

    DOE Patents [OSTI]

    Moskowitz, P.E.; Maya, J.

    1987-09-08T23:59:59.000Z

    A fluorescent lamp wherein magnetic field generating means (e.g., permanent magnets) are utilized to generate a static magnetic field across the respective electrode structures of the lamp such that maximum field strength is located at the electrode's filament. An increase in efficacy during operation has been observed. 2 figs.

  3. Magnetic Field Measurement System

    SciTech Connect (OSTI)

    Kulesza, Joe; Johnson, Eric; Lyndaker, Aaron; Deyhim, Alex; Waterman, Dave; Blomqvist, K. Ingvar [Advanced Design Consulting USA, 126 Ridge Road, P.O. Box 187, Lansing, NY 14882 (United States); Dunn, Jonathan Hunter [MAX-lab, SE-221 00 Lund (Sweden)

    2007-01-19T23:59:59.000Z

    A magnetic field measurement system was designed, built and installed at MAX Lab, Sweden for the purpose of characterizing the magnetic field produced by Insertion Devices (see Figure 1). The measurement system consists of a large granite beam roughly 2 feet square and 14 feet long that has been polished beyond laboratory grade for flatness and straightness. The granite precision coupled with the design of the carriage yielded minimum position deviations as measured at the probe tip. The Hall probe data collection and compensation technique allows exceptional resolution and range while taking data on the fly to programmable sample spacing. Additional flip coil provides field integral data.

  4. Discovery of magnetic fields in hot subdwarfs

    E-Print Network [OSTI]

    S. J. O'Toole; S. Jordan; S. Friedrich; U. Heber

    2005-03-10T23:59:59.000Z

    We present polarisation measurements of sdB and sdO stars using FORS1 on the VLT. The observations were made as part of a project to determine whether magnetic fields in two super-metal-rich stars can explain their extreme abundance peculiarities. Field strengths of up to ~1.5 kG have been measured at varying levels of significance in each of our six targets, however no clear evidence was found between apparently normal subdwarfs and the metal-rich objects. The origin of the magnetic fields is unknown. We also discuss the implications of our measurements for magnetic flux conservation in late stages of stellar evolution.

  5. Magnetic field measurements on the sun and implications for stellar magnetic field observations

    SciTech Connect (OSTI)

    Sun, W.H.; Giampapa, M.S.; Worden, S.P.

    1987-01-01T23:59:59.000Z

    Results of solar magnetic field measurements in plages, sunspot umbrae, and sunspot penumbrae using high spectral resolution, unpolarized infrared H band spectral data are presented. A Fourier deconvolution analysis scheme similar to that utilized for stellar magnetic field measurements is adopted. As an example, a field strength of 3240 + or - 450 G is determined in a sunspot umbra combined with a value of 2000 + or - 180 G in the associated penumbra. These values are compared with a direct measurement of the spot umbra and penumbra field strengths based on the observed separation of the Zeeman components of the magnetically sensitive lines. Possible origins for the discrepancy between the results inferred by these two different techniques are discussed. The Fourier analysis results confirm the widespread occurrence of kilogauss level fields in the solar photosphere. The implications of the solar results for stellar magnetic field measurements are considered. 45 references.

  6. Low field magnetic resonance imaging

    DOE Patents [OSTI]

    Pines, Alexander (Berkeley, CA); Sakellariou, Dimitrios (Billancourt, FR); Meriles, Carlos A. (Fort Lee, NJ); Trabesinger, Andreas H. (London, GB)

    2010-07-13T23:59:59.000Z

    A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.

  7. Discovery of magnetic fields in hot subdwarfs

    E-Print Network [OSTI]

    S. J. O'Toole; S. Jordan; S. Friedrich; U. Heber

    2004-10-02T23:59:59.000Z

    We present initial results of a project to measure mean longitudinal magnetic fields in a group of sdB/OB/O stars. The project was inspired by the discovery of three super-metal-rich sdOB stars, each having metals (e.g. Ti, V) enhanced by factors of 10^3 to 10^5. Similar behaviour is observed in chemically peculiar A stars, where strong magnetic fields are responsible for the enrichment. With this in mind, we obtained circularly polarised spectra of two of the super-metal-rich sdOBs, two "normal" sdBs and two sdOs using FORS1 on the ESO/VLT. By examining circular polarisation in the hydrogen Balmer lines and in helium lines, we have detected magnetic fields with strengths of 1-2 kG in most of our targets. This suggests that such fields are relatively common in hot subdwarfs.

  8. Fast superconducting magnetic field switch

    DOE Patents [OSTI]

    Goren, Yehuda (Mountain View, CA); Mahale, Narayan K. (The Woodlands, TX)

    1996-01-01T23:59:59.000Z

    The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles.

  9. Exposure guidelines for magnetic fields

    SciTech Connect (OSTI)

    Miller, G.

    1987-12-01T23:59:59.000Z

    The powerful magnetic fields produced by a controlled fusion experiment at Lawrence Livermore National Laboratory (LLNL) necessitated the development of personnel-exposure guidelines for steady magnetic fields. A literature search and conversations with active researchers showed that it is currently possible to develop preliminary exposure guidelines for steady magnetic fields. An overview of the results of past research into the bioeffects of magnetic fields was compiled, along with a discussion of hazards that may be encountered by people with sickle-cell anemia or medical electronic and prosthetic implants. The LLNL steady magnetic-field exposure guidelines along with a review of developments concerning the safety of time-varying fields were also presented in this compilation. Guidelines developed elsewhere for time varying fields were also given. Further research is needed to develop exposure standards for both steady or time-varying fields.

  10. Magnetic-field-dosimetry system

    DOE Patents [OSTI]

    Lemon, D.K.; Skorpik, J.R.; Eick, J.L.

    1981-01-21T23:59:59.000Z

    A device is provided for measuring the magnetic field dose and peak field exposure. The device includes three Hall-effect sensors all perpendicular to each other, sensing the three dimensional magnetic field and associated electronics for data storage, calculating, retrieving and display.

  11. High magnetic field processing of liquid crystalline polymers

    DOE Patents [OSTI]

    Smith, Mark E. (Los Alamos, NM); Benicewicz, Brian C. (Los Alamos, NM); Douglas, Elliot P. (Los Alamos, NM)

    1998-01-01T23:59:59.000Z

    A process of forming bulk articles of oriented liquid crystalline thermoset material, the material characterized as having an enhanced tensile modulus parallel to orientation of an applied magnetic field of at least 25 percent greater than said material processed in the absence of a magnetic field, by curing a liquid crystalline thermoset precursor within a high strength magnetic field of greater than about 2 Tesla, is provided, together with a resultant bulk article of a liquid crystalline thermoset material, said material processed in a high strength magnetic field whereby said material is characterized as having a tensile modulus parallel to orientation of said field of at least 25 percent greater than said material processed in the absence of a magnetic field.

  12. High magnetic field processing of liquid crystalline polymers

    DOE Patents [OSTI]

    Smith, M.E.; Benicewicz, B.C.; Douglas, E.P.

    1998-11-24T23:59:59.000Z

    A process of forming bulk articles of oriented liquid crystalline thermoset material, the material characterized as having an enhanced tensile modulus parallel to orientation of an applied magnetic field of at least 25 percent greater than said material processed in the absence of a magnetic field, by curing a liquid crystalline thermoset precursor within a high strength magnetic field of greater than about 2 Tesla, is provided, together with a resultant bulk article of a liquid crystalline thermoset material, said material processed in a high strength magnetic field whereby said material is characterized as having a tensile modulus parallel to orientation of said field of at least 25 percent greater than said material processed in the absence of a magnetic field.

  13. Magnetic fields of the W4 superbubble

    E-Print Network [OSTI]

    Gao, X Y; Reich, P; Han, J L; Kothes, R

    2015-01-01T23:59:59.000Z

    Superbubbles and supershells are the channels for transferring mass and energy from the Galactic disk to the halo. Magnetic fields are believed to play a vital role in their evolution. We study the radio continuum and polarized emission properties of the W4 superbubble to determine its magnetic field strength. New sensitive radio continuum observations were made at 6 cm, 11 cm, and 21 cm. The total intensity measurements were used to derive the radio spectrum of the W4 superbubble. The linear polarization data were analysed to determine the magnetic field properties within the bubble shells. The observations show a multi-shell structure of the W4 superbubble. A flat radio continuum spectrum that stems from optically thin thermal emission is derived from 1.4 GHz to 4.8 GHz. By fitting a passive Faraday screen model and considering the filling factor fne , we obtain the thermal electron density ne = 1.0/\\sqrt{fne} (\\pm5%) cm^-3 and the strength of the line-of-sight component of the magnetic field B// = -5.0/\\sq...

  14. Developments in deep brain stimulation using time dependent magnetic fields

    SciTech Connect (OSTI)

    Crowther, L.J.; Nlebedim, I.C.; Jiles, D.C.

    2012-03-07T23:59:59.000Z

    The effect of head model complexity upon the strength of field in different brain regions for transcranial magnetic stimulation (TMS) has been investigated. Experimental measurements were used to verify the validity of magnetic field calculations and induced electric field calculations for three 3D human head models of varying complexity. Results show the inability for simplified head models to accurately determine the site of high fields that lead to neuronal stimulation and highlight the necessity for realistic head modeling for TMS applications.

  15. Measurements of magnetic field alignment

    SciTech Connect (OSTI)

    Kuchnir, M.; Schmidt, E.E.

    1987-11-06T23:59:59.000Z

    The procedure for installing Superconducting Super Collider (SSC) dipoles in their respective cryostats involves aligning the average direction of their field with the vertical to an accuracy of 0.5 mrad. The equipment developed for carrying on these measurements is described and the measurements performed on the first few prototypes SSC magnets are presented. The field angle as a function of position in these 16.6 m long magnets is a characteristic of the individual magnet with possible feedback information to its manufacturing procedure. A comparison of this vertical alignment characteristic with a magnetic field intensity (by NMR) characteristic for one of the prototypes is also presented. 5 refs., 7 figs.

  16. Magnetic Fields in Molecular Cloud Cores

    E-Print Network [OSTI]

    Shantanu Basu

    2004-10-22T23:59:59.000Z

    Observations of magnetic field strengths imply that molecular cloud fragments are individually close to being in a magnetically critical state, even though both magnetic field and column density measurements range over two orders of magnitude. The turbulent pressure also approximately balances the self-gravitational pressure. These results together mean that the one-dimensional velocity dispersion $\\sigv$ is proportional to the mean \\Alf speed of a cloud $\\va$. Global models of MHD turbulence in a molecular cloud show that this correlation is naturally satisfied for a range of different driving strengths of the turbulence. For example, an increase of turbulent driving causes a cloud expansion which also increases $\\va$. Clouds are in a time averaged balance but exhibit large oscillatory motions, particularly in their outer rarefied regions. We also discuss models of gravitational fragmentation in a sheet-like region in which turbulence has already dissipated, including the effects of magnetic fields and ion-neutral friction. Clouds with near-critical mass-to-flux ratios lead to subsonic infall within cores, consistent with some recent observations of motions in starless cores. Conversely, significantly supercritical clouds are expected to produce extended supersonic infall.

  17. Confining potential from interacting magnetic and torsion fields

    E-Print Network [OSTI]

    Patricio Gaete; José A. Helaÿel-Neto

    2009-05-29T23:59:59.000Z

    Adopting the gauge-invariant but path-dependent variables formalism, we study the coupling of torsion fields with photons in the presence of an external background electromagnetic. We explicitly show that, in the case of a constant electric field strength expectation value, the static potential remains Coulombic, while in the case of a constant magnetic field strength expectation value a confining potential is obtained. This result displays a marked qualitative departure from the usual coupling of axionlike particles with photons in the presence of an external magnetic field.

  18. Dust-Plasma Sheath in an Oblique Magnetic Field

    SciTech Connect (OSTI)

    Foroutan, G.; Mehdipour, H. [Physics Department, Faculty of Science, Sahand University of Technology, Tabriz (Iran, Islamic Republic of)

    2008-09-07T23:59:59.000Z

    Using numerical simulations of the multi fluid equations the structure of the magnetized sheath near a plasma boundary is studied in the presence of charged dust particles. The dependence of the electron, ion, and dust densities as well as the electrostatic potential, dust charge, and ion normal velocity, on the magnetic field strength and the edge dust number density is investigated.

  19. Are Cluster Magnetic Fields Primordial ?

    E-Print Network [OSTI]

    Robi Banerjee; Karsten Jedamzik

    2004-09-07T23:59:59.000Z

    We present results of a detailed and fully non-linear numerical and analytical investigation of magnetic field evolution from the very earliest cosmic epochs to the present. We find that, under reasonable assumptions concerning the efficiency of a putative magnetogenesis era during cosmic phase transitions, surprisingly strong magnetic fields 10^{-13} - 10^{-11} Gauss, on comparatively small scales 100 pc - 10 kpc may survive to the present. Building on prior work on the evolution of magnetic fields during the course of gravitational collapse of a cluster, which indicates that pre-collapse fields of 4\\times 10^{-12} Gauss extant on small scales may suffice to produce clusters with acceptable Faraday rotation measures, we question the widely hold view that cluster magnetic fields may not be entirely of primordial origin.

  20. The Magnetic Fields of Classical T Tauri Stars

    E-Print Network [OSTI]

    Christopher M. Johns-Krull

    2007-04-23T23:59:59.000Z

    We report new magnetic field measurements for 14 classical T Tauri stars (CTTSs). We combine these data with one previous field determination in order to compare our observed field strengths with the field strengths predicted by magnetospheric accretion models. We use literature data on the stellar mass, radius, rotation period, and disk accretion rate to predict the field strength that should be present on each of our stars according to these magnetospheric accretion models. We show that our measured field values do not correlate with the field strengths predicted by simple magnetospheric accretion theory. We also use our field strength measurements and literature X-ray luminosity data to test a recent relationship expressing X-ray luminosity as a function of surface magnetic flux derived from various solar feature and main sequence star measurements. We find that the T Tauri stars we have observed have weaker than expected X-ray emission by over an order of magnitude on average using this relationship. We suggest the cause for this is actually a result of the very strong fields on these stars which decreases the efficiency with which gas motions in the photosphere can tangle magnetic flux tubes in the corona.

  1. Determination of Electric-Field, Magnetic-Field, and Electric...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Electric-Field, Magnetic-Field, and Electric-Current Distributions of Infrared Optical Antennas: A Near-Field Determination of Electric-Field, Magnetic-Field, and Electric-Current...

  2. Mitigated-force carriage for high magnetic field environments

    DOE Patents [OSTI]

    Ludtka, Gerard M; Ludtka, Gail M; Wilgen, John B; Murphy, Bart L

    2014-05-20T23:59:59.000Z

    A carriage for high magnetic field environments includes a first work-piece holding means for holding a first work-piece, the first work-piece holding means being disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla. The first work-piece holding means is further disposed in operable connection with a second work-piece holding means for holding a second work-piece so that, as the first work-piece is inserted into the magnetic field, the second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.

  3. An exact Lagrangian integral for the Newtonian gravitational field strength

    E-Print Network [OSTI]

    Thomas Buchert

    2006-01-23T23:59:59.000Z

    An exact expression for the gravitational field strength in a self-gravitating dust continuum is derived within the Lagrangian picture of continuum mechanics. From the Euler-Newton system a transport equation for the gravitational field strength is formulated and then integrated along trajectories of continuum elements. The resulting integral solves one of the Lagrangian equations of the corresponding Lagrange-Newton system in general. Relations to known exact solutions without symmetry in Newtonian gravity are discussed. The presented integral may be employed to access the non-perturbative regime of structure formation in Newtonian cosmology, and to apply iterative Lagrangian schemes to solve the Lagrange-Newton system.

  4. SOLAR MAGNETIC FIELD SIGNATURES IN HELIOSEISMIC SPLITTING COEFFICIENTS

    SciTech Connect (OSTI)

    Baldner, Charles S.; Basu, Sarbani [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT, 06520-8101 (United States); Antia, H. M. [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Larson, Timothy P., E-mail: charles.baldner@yale.ed [Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305-4085 (United States)

    2009-11-10T23:59:59.000Z

    Normal modes of oscillation of the Sun are useful probes of the solar interior. In this work, we use the even-order splitting coefficients to study the evolution of magnetic fields in the convection zone over solar cycle 23, assuming that the frequency splitting is only due to rotation and a large-scale magnetic field. We find that the data are best fit by a combination of a poloidal field and a double-peaked near-surface toroidal field. The toroidal fields are centered at r {sub 0} = 0.999 R {sub sun} and r = 0.996 R {sub sun} and are confined to the near-surface layers. The poloidal field is a dipole field. The peak strength of the poloidal field is 124 +- 17 G. The toroidal field peaks at 380 +- 30 G and 1.4 +- 0.2 kG for the shallower and deeper fields, respectively. The field strengths are highly correlated with surface activity. The toroidal field strength shows a hysteresis-like effect when compared to the global 10.7 cm radio flux. The poloidal field strength shows evidence of saturation at high activity.

  5. Extragalactic Magnetic Field and the Highest Energy Cosmic Rays

    E-Print Network [OSTI]

    Sangjin Lee; Angela Olinto; Guenter Sigl

    1995-08-21T23:59:59.000Z

    The strength and spectrum of the extragalactic magnetic field are still unknown. Its measurement would help answer the question of whether galactic fields are purely a primordial relic or were dynamically enhanced from a much smaller cosmological seed field. In this letter, we show that the composition, spectrum, and directional distribution of extragalactic ultrahigh energy cosmic rays with energies above $\\simeq 10^{18}\\ev$ can probe the large scale component of the extragalactic magnetic field below the present observational upper limit of $10^{-9}$ Gauss. Cosmic ray detectors under construction or currently in the proposal stage should be able to test the existence of the extragalactic magnetic fields on scales of a few to tens of Mpc and strengths in the range $\\simeq 10^{-10} - 10^{-9}$ Gauss.

  6. Nematic order of model goethite nanorods in a magnetic field

    E-Print Network [OSTI]

    H. H. Wensink; G. J. Vroege

    2005-01-18T23:59:59.000Z

    We explore the nematic order of model goethite nanorods in an external magnetic field within Onsager-Parsons density functional theory. The goethite rods are represented by monodisperse, charged spherocylinders with a permanent magnetic moment along the rod main axis, forcing the particles to align parallel to the magnetic field at low field strength. The intrinsic diamagnetic susceptibility anisometry of the rods is negative which leads to a preferred perpendicular orientation at higher field strength. It is shown that these counteracting effects may give rise to intricate phase behavior, including a pronounced stability of biaxial nematic order and the presence of reentrant phase transitions and demixing phenomena. The effect of the applied field on the nematic-to-smectic transition will also be addressed.

  7. Magnetic Resonance Imaging System Based on Earth's Magnetic Field

    E-Print Network [OSTI]

    Stepi?nik, Janez

    Magnetic Resonance Imaging System Based on Earth's Magnetic Field Ales Mohoric,1,* Gorazd Planinsic magnetic field can be partly compensated by the receiving coil design and shielding of electromagnetic pick and must be monitored accurately.[8­ 10] The importance of NMR in a non-uniform magnetic field

  8. Magnetic helicity evolution in a periodic domain with imposed field

    E-Print Network [OSTI]

    Axel Brandenburg; William H. Matthaeus

    2004-05-24T23:59:59.000Z

    In helical hydromagnetic turbulence with an imposed magnetic field (which is constant in space and time) the magnetic helicity of the field within a periodic domain is no longer an invariant of the ideal equations. Alternatively, there is a generalized magnetic helicity that is an invariant of the ideal equations. It is shown that this quantity is not gauge invariant and that it can therefore not be used in practice. Instead, the evolution equation of the magnetic helicity of the field describing the deviation from the imposed field is shown to be a useful tool. It is demonstrated that this tool can determine steady state quenching of the alpha-effect. A simple three-scale model is derived to describe the evolution of the magnetic helicity and to predict its sign as a function of the imposed field strength. The results of the model agree favorably with simulations.

  9. Thermalization in External Magnetic Field

    E-Print Network [OSTI]

    Ali-Akbari, Mohammad

    2012-01-01T23:59:59.000Z

    In the AdS/CFT framework meson thermalization in the presence of a constant external magnetic field in a strongly coupled gauge theory has been studied. In the gravitational description the thermalization of mesons corresponds to the horizon formation on the flavour D7-brane which is embedded in the AdS_5 x S^5 background in the probe limit. The apparent horizon forms due to the time-dependent change in the baryon number chemical potential, the injection of baryons in the gauge theory. We will numerically show that the thermalization happens even faster in the presence of the magnetic field on the probe brane. We observe that this reduction in the thermalization time sustains up to a specific value of the magnetic field.

  10. Accretion Discs with Strong Toroidal Magnetic Fields

    E-Print Network [OSTI]

    M. C. Begelman; J. E. Pringle

    2006-12-12T23:59:59.000Z

    Simulations and analytic arguments suggest that the turbulence driven by magnetorotational instability (MRI) in accretion discs can amplify the toroidal (azimuthal) component of the magnetic field to a point at which magnetic pressure exceeds the combined gas + radiation pressure in the disc. Arguing from the recent analysis by Pessah and Psaltis, and other MRI results in the literature, we conjecture that the limiting field strength for a thin disc is such that the Alfven speed roughly equals the geometric mean of the Keplerian speed and the gas sound speed. We examine the properties of such magnetically-dominated discs, and show that they resolve a number of outstanding problems in accretion disc theory. The discs would be thicker than standard (Shakura-Sunyaev) discs at the same radius and accretion rate, and would tend to have higher colour temperatures. If they transport angular momentum according to an alpha-prescription, they would be stable against the thermal and viscous instabilities that are found in standard disc models. In discs fuelling active galactic nuclei, magnetic pressure support could also alleviate the restriction on accretion rate imposed by disc self-gravity.

  11. Need for development of higher strength cryogenic structural materials for fusion magnet

    SciTech Connect (OSTI)

    Nishimura, Arata [ITER Organization, Route de Vinon sur Verdon, 13115 St Paul Lez Durance (France)

    2014-01-27T23:59:59.000Z

    A prototype fusion reactor is targeted as a beyond ITER project which is so called DEMO. Several conceptual designs have been carried out. Recently, in order to recognize practical aspects on maintenance of the prototype reactor, the replacement procedure of in-vessel components was focused and “sector process” was proposed. The process is that the reactor consists of sectors and all sectors will be drowned and replaced in a short time. The slim coil which generated higher magnetic field is required to realize the sector process. From the point of coil design, the occupancy of the structural material on the cross section of the coil increases with an increase of magnetic field. To realize the slim coil, the cryogenic structural material with higher yield strength and the proper toughness is desired.

  12. Chiral Magnetic Effect in Protoneutron Stars and Magnetic Field Spectral Evolution

    E-Print Network [OSTI]

    Sigl, Günter

    2015-01-01T23:59:59.000Z

    We investigate the evolution of the chiral magnetic instability in a protoneutron star and compute the resulting magnetic power and helicity spectra. The instability may act during the early cooling phase of the hot protoneutron star after supernova core collapse, where it can contribute to the buildup of magnetic fields of strength up to the order of $10^{14}$ G. The maximal field strengths generated by this instability, however, depend considerably on the temperature of the protoneutron star, on density fluctuations and turbulence spectrum of the medium. At the end of the hot cooling phase the magnetic field tends to be concentrated around the submillimeter to cm scale, where it is subject to slow resistive damping.

  13. Engineering Weyl nodes in Dirac semimetals by a magnetic field

    E-Print Network [OSTI]

    E. V. Gorbar; V. A. Miransky; I. A. Shovkovy

    2013-10-07T23:59:59.000Z

    We study the phase diagram of a Dirac semimetal in a magnetic field at a nonzero charge density. It is shown that there exists a critical value of the chemical potential at which a first-order phase transition takes place. At subcritical values of the chemical potential the ground state is a gapped state with a dynamically generated Dirac mass and a broken chiral symmetry. The supercritical phase is the normal (gapless) phase with a nontrivial chiral structure: it is a Weyl semimetal with a pair of Weyl nodes for each of the original Dirac points. The nodes are separated by a dynamically induced chiral shift. The direction of the chiral shift coincides with that of the magnetic field and its magnitude is determined by the quasiparticle charge density, the strength of the magnetic field, and the strength of the interaction. The rearrangement of the Fermi surface accompanying this phase transition is described.

  14. FURMAN NMR SAFETY INFORMATION Standard safety guidelines have been put in place for work around the high-field magnets, and all users

    E-Print Network [OSTI]

    Earth's magnetic field 6.0 x 10-5 T at the equator Refrigerator Magnet .0100-.0150 T MRI Medical the high-field magnets, and all users must take proper precautions to prevent expensive instrument damage and serious personal injury, including death. NMR Magnetic Field Strength · Remember: The magnetic field

  15. EMF in your environment. Magnetic field measurements of everyday electrical devices

    SciTech Connect (OSTI)

    Not Available

    1992-12-01T23:59:59.000Z

    The publication compares the strength of 60 hertz magnetic fields produced by common electrical items and shows you how their strength diminishes as you move farther away from them. The information presented here has to do with the strength of the magnetic field; however, the authors aren't certain that the strength of the field is the only important consideration. It may turn out that other factors are also important. Future research is likely to reveal that the information given in the publication is only part of the story.

  16. Dual AC Dipole Excitation for the Measurement of Magnetic Multipole Strength from Beam Position Monitor Data

    SciTech Connect (OSTI)

    M. Spata, G.A. Krafft

    2011-09-01T23:59:59.000Z

    An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a technique for characterizing the nonlinear fields of the beam transport system. Two air-core dipole magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the electron beam. Fourier decomposition of beam position monitor data was then used to measure the amplitude of these frequencies at different positions along the beamline. For a purely linear transport system one expects to find solely the frequencies that were applied to the dipoles with amplitudes that depend on the phase advance of the lattice. In the presence of nonlinear fields one expects to also find harmonics of the driving frequencies that depend on the order of the nonlinearity. The technique was calibrated using one of the sextupole magnets in a CEBAF beamline and then applied to a dipole to measure the sextupole and octupole strength of the magnet. A comparison is made between the beam-based measurements, results from TOSCA and data from our Magnet Measurement Facility.

  17. HIGH-FIELD SUPERCONDUCTING ACCELERATOR MAGNETS

    E-Print Network [OSTI]

    Taylor, C.

    2011-01-01T23:59:59.000Z

    D. C. 'Niobium-Titanium Superconducting Material s ', in S.14, 1982 HIGH-FIELD SUPERCONDUCTING ACCELERATOR MAGNETS C.SUMAG-68 HIGH-FIELD SUPERCONDUCTING ACCELERATOR MAGNETS* C.

  18. Magnetic Fields and the Triaxiality of Molecular Cloud Cores

    E-Print Network [OSTI]

    Shantanu Basu

    2000-08-16T23:59:59.000Z

    We make the hypothesis that molecular cloud fragments are triaxial bodies with a large scale magnetic field oriented along the short axis. While consistent with theoretical expectations, this idea is supported by magnetic field strength data, which show strong evidence for flattening along the direction of the mean magnetic field. It is also consistent with early submillimeter polarization data, which show that the projected direction of the magnetic field is often slightly misaligned with the projected minor axis of a molecular cloud core, i.e., the offset angle $\\Psi$ is nonzero. We calculate distributions of $\\Psi$ for various triaxial bodies, when viewed from a random set of viewing angles. The highest viewing probability always corresponds to $\\Psi=0^{\\circ}$, but there is a finite probability of viewing all nonzero $\\Psi$, including even $\\Psi =90^{\\circ}$; the average offset typically falls in the range $10^{\\circ}-30^{\\circ}$ for triaxial bodies most likely to satisfy observational and theoretical constraints.

  19. Primordial magnetic fields and formation of molecular hydrogen

    E-Print Network [OSTI]

    Shiv K Sethi; Biman B. Nath; Kandaswamy Subramanian

    2008-04-22T23:59:59.000Z

    We study the implications of primordial magnetic fields for the thermal and ionization history of the post-recombination era. In particular we compute the effects of dissipation of primordial magnetic fields owing to ambipolar diffusion and decaying turbulence in the intergalactic medium (IGM) and the collapsing halos and compute the effects of the altered thermal and ionization history on the formation of molecular hydrogen. We show that, for magnetic field strengths in the range $2 \\times 10^{-10} {\\rm G} \\la B_0 \\la 2 \\times 10^{-9} {\\rm G}$, the molecular hydrogen fraction in IGM and collapsing halo can increase by a factor 5 to 1000 over the case with no magnetic fields. We discuss the implication of the increased molecular hydrogen fraction on the radiative transfer of UV photons and the formation of first structures in the universe.

  20. Turbulence and Magnetic Fields in Clouds

    E-Print Network [OSTI]

    Shantanu Basu

    2004-11-15T23:59:59.000Z

    We discuss several categories of models which may explain the IMF, including the possible role of turbulence and magnetic fields.

  1. CORONAL MAGNETIC FIELD MEASUREMENTS THROUGH GYRORESONANCE EMISSION

    E-Print Network [OSTI]

    White, Stephen

    Chapter 5 CORONAL MAGNETIC FIELD MEASUREMENTS THROUGH GYRORESONANCE EMISSION Stephen M. White This article reviews the use of gyroresonance emission at radio wavelengths to measure coronal magnetic fields. Keywords: Sun, solar corona, solar magnetic fields, solar radio emission Introduction Since the realization

  2. Magnetic monopole and the nature of the static magnetic field

    E-Print Network [OSTI]

    Xiuqing Huang

    2008-12-10T23:59:59.000Z

    We investigate the factuality of the hypothetical magnetic monopole and the nature of the static magnetic field. It is shown from many aspects that the concept of the massive magnetic monopoles clearly is physically untrue. We argue that the static magnetic field of a bar magnet, in fact, is the static electric field of the periodically quasi-one-dimensional electric-dipole superlattice, which can be well established in some transition metals with the localized d-electron. This research may shed light on the perfect unification of magnetic and electrical phenomena.

  3. Transient horizontal magnetic fields in solar plage regions

    E-Print Network [OSTI]

    R. Ishikawa; S. Tsuneta; K. Ichimoto; H. Isobe; Y. Katsukawa; B. W. Lites; S. Nagata; T. Shimizu; R. A. Shine; Y. Suematsu; T. D. Tarbell; A. M. Title

    2008-02-13T23:59:59.000Z

    We report the discovery of isolated, small-scale emerging magnetic fields in a plage region with the Solar Optical Telescope aboard Hinode. Spectro-polarimetric observations were carried out with a cadence of 34 seconds for the plage region located near disc center. The vector magnetic fields are inferred by Milne-Eddington inversion. The observations reveal widespread occurrence of transient, spatially isolated horizontal magnetic fields. The lateral extent of the horizontal magnetic fields is comparable to the size of photospheric granules. These horizontal magnetic fields seem to be tossed about by upflows and downflows of the granular convection. We also report an event that appears to be driven by the magnetic buoyancy instability. We refer to buoyancy-driven emergence as type1 and convection-driven emergence as type2. Although both events have magnetic field strengths of about 600 G, the filling factor of type1 is a factor of two larger than that of type2. Our finding suggests that the granular convection in the plage regions is characterized by a high rate of occurrence of granular-sized transient horizontal fields.

  4. The Stability of Magnetized Rotating Plasmas with Superthermal Fields

    E-Print Network [OSTI]

    Martin E. Pessah; Dimitrios Psaltis

    2005-04-13T23:59:59.000Z

    During the last decade it has become evident that the magnetorotational instability is at the heart of the enhanced angular momentum transport in weakly magnetized accretion disks around neutron stars and black holes. In this paper, we investigate the local linear stability of differentially rotating, magnetized flows and the evolution of the magnetorotational instability beyond the weak-field limit. We show that, when superthermal toroidal fields are considered, the effects of both compressibility and magnetic tension forces, which are related to the curvature of toroidal field lines, should be taken fully into account. We demonstrate that the presence of a strong toroidal component in the magnetic field plays a non-trivial role. When strong fields are considered, the strength of the toroidal magnetic field not only modifies the growth rates of the unstable modes but also determines which modes are subject to instabilities. We find that, for rotating configurations with Keplerian laws, the magnetorotational instability is stabilized at low wavenumbers for toroidal Alfven speeds exceeding the geometric mean of the sound speed and the rotational speed. We discuss the significance of our findings for the stability of cold, magnetically dominated, rotating fluids and argue that, for these systems, the curvature of toroidal field lines cannot be neglected even when short wavelength perturbations are considered. We also comment on the implications of our results for the validity of shearing box simulations in which superthermal toroidal fields are generated.

  5. Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization

    DOE Patents [OSTI]

    Doughty, Frank C. (Plano, TX); Spencer, John E. (Plano, TX)

    2000-12-19T23:59:59.000Z

    In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.

  6. Magnetic fluid flow phenomena in DC and rotating magnetic fields

    E-Print Network [OSTI]

    Rhodes, Scott E. (Scott Edward), 1981-

    2004-01-01T23:59:59.000Z

    An investigation of magnetic fluid experiments and analysis is presented in three parts: a study of magnetic field induced torques in magnetorheological fluids, a characterization and quantitative measurement of properties ...

  7. Discovery of magnetic fields in CPNs

    E-Print Network [OSTI]

    S. Jordan; K. Werner; S. J. O'Toole

    2004-10-21T23:59:59.000Z

    For the first time we have directly detected magnetic fields in central stars of planetary nebulae by means of spectro-polarimetry with FORS1 at the VLT. In all four objects of our sample we found kilogauss magnetic fields, in NGC 1360 and LSS1362 with very high significance, while in Abell36 and EGB5 the existence of a magnetic field is probable but with less certainty. This discovery supports the hypothesis that the non-spherical symmetry of most planetary nebulae is caused by magnetic fields in AGB stars. Our high discovery rate demands mechanisms to prevent full conservation of magnetic flux during the transition to white dwarfs.

  8. Baryon onset in a magnetic field

    E-Print Network [OSTI]

    Alexander Haber; Florian Preis; Andreas Schmitt

    2014-12-19T23:59:59.000Z

    The critical baryon chemical potential for the onset of nuclear matter is a function of the vacuum mass and the binding energy. Both quantities are affected by an external magnetic field. We show within two relativistic mean-field models - including magnetic catalysis, but omitting the anomalous magnetic moment - that a magnetic field increases both the vacuum mass and the binding energy. For sufficiently large magnetic fields, the effect on the vacuum mass dominates and as a result the critical baryon chemical potential is increased.

  9. Transient magnetic field and temperature modeling in large magnet applications

    SciTech Connect (OSTI)

    Gurol, H.; Hardy, G.E.; Peck, S.D.; Leung, E. (General Dynamics Corp., San Diego, CA (USA). Space Systems Div.)

    1989-07-01T23:59:59.000Z

    This paper discusses a coupled magnetic/thermal model developed to study heat and magnetic field diffusion in conducting materials subject to time-varying external fields. There are numerous applications, both military and commercial. These include: energy storage devices, pulsed power transformers, and electromagnetic launchers. The time scales of interest may range from a magnetic field pulse of a microsecond in an electromagnetic launcher, to hundreds of seconds in an energy storage magnet. The problem can be dominated by either the magnetic field or heat diffusion, depending on the temperature and the material properties of the conductor. In general, heat diffuses much more rapidly in high electrical conductivity materials of cryogenic temperatures. The magnetic field takes longer to diffuse, since screening currents can be rapidly set up which shield the interior of the material from further magnetic field penetration. Conversely, in high resistivity materials, the magnetic field diffuses much more rapidly. A coupled two-dimensional thermal/magnetic model has been developed. The results of this model, showing the time and spatial variation of the magnetic field and temperature, are discussed for the projectile of an electromagnetic launcher.

  10. Effects of geometry and impurities on quantum rings in magnetic fields RID D-3014-2009

    E-Print Network [OSTI]

    Aichinger, M.; Chin, Siu A.; Krotscheck, E.; Rasanen, E.

    2006-01-01T23:59:59.000Z

    We investigate the effects of impurities and changing ring geometry on the energetics of quantum rings under different magnetic field strengths. We show that as the magnetic field and/or the electron number are/is increased, both the quasiperiodic...

  11. New limits on extragalactic magnetic fields from rotation measures

    E-Print Network [OSTI]

    Pshirkov, Maxim S; Urban, Federico R

    2015-01-01T23:59:59.000Z

    We take advantage of the wealth of rotation measures data contained in the NVSS catalogue to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. We simulate the extragalactic contribution to the rotation measures for a given field strength and correlation length, by assuming that the electron density follows the distribution of Lyman-$\\alpha$ clouds. Based on the observation that rotation measures from low-luminosity distant radio sources do not exhibit any trend with redshift, while the extragalactic contribution instead grows with distance, we constrain fields with Mpc coherence length to be below 1.2 nG at the $2\\sigma$ level, and fields coherent across the entire observable Universe below 0.5 nG. These limits do not depend on the particular origin of these cosmological fields.

  12. Brushed permanent magnet DC MLC motor operation in an external magnetic field

    SciTech Connect (OSTI)

    Yun, J.; St Aubin, J.; Rathee, S.; Fallone, B. G. [Department of Physics, University of Alberta, 11322-89 Avenue, Edmonton, Alberta T6G 2G7 (Canada) and Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada) and Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Department of Physics, University of Alberta, 11322-89 Avenue, Edmonton, Alberta T6G 2G7 (Canada); Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada) and Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada)

    2010-05-15T23:59:59.000Z

    Purpose: Linac-MR systems for real-time image-guided radiotherapy will utilize the multileaf collimators (MLCs) to perform conformal radiotherapy and tumor tracking. The MLCs would be exposed to the external fringe magnetic fields of the linac-MR hybrid systems. Therefore, an experimental investigation of the effect of an external magnetic field on the brushed permanent magnet DC motors used in some MLC systems was performed. Methods: The changes in motor speed and current were measured for varying external magnetic field strengths up to 2000 G generated by an EEV electromagnet. These changes in motor characteristics were measured for three orientations of the motor in the external magnetic field, mimicking changes in motor orientations due to installation and/or collimator rotations. In addition, the functionality of the associated magnetic motor encoder was tested. The tested motors are used with the Varian 120 leaf Millennium MLC (Maxon Motor half leaf and full leaf motors) and the Varian 52 leaf MKII MLC (MicroMo Electronics leaf motor) including a carriage motor (MicroMo Electronics). Results: In most cases, the magnetic encoder of the motors failed prior to any damage to the gearbox or the permanent magnet motor itself. This sets an upper limit of the external magnetic field strength on the motor function. The measured limits of the external magnetic fields were found to vary by the motor type. The leaf motor used with a Varian 52 leaf MKII MLC system tolerated up to 450{+-}10 G. The carriage motor tolerated up to 2000{+-}10 G field. The motors used with the Varian 120 leaf Millennium MLC system were found to tolerate a maximum of 600{+-}10 G. Conclusions: The current Varian MLC system motors can be used for real-time image-guided radiotherapy coupled to a linac-MR system, provided the fringe magnetic fields at their locations are below the determined tolerance levels. With the fringe magnetic fields of linac-MR systems expected to be larger than the tolerance levels determined, some form of magnetic shielding would be required.

  13. Magnetic field topology of accreting white dwarfs

    E-Print Network [OSTI]

    Klaus Reinsch; Fabian Euchner; Klaus Beuermann; Stefan Jordan

    2003-02-04T23:59:59.000Z

    We report first results of our systematic investigation of the magnetic field structure of rotating single magnetic white dwarfs and of white dwarfs in magnetic cataclysmic variables. The global magnetic field distributions on the isolated white dwarf HE1045-0908 and the accreting white dwarfs in EF Eri and CP Tuc have been derived from phase-resolved flux and polarization spectra obtained with FORS1 at the ESO VLT using the systematic method of Zeeman tomography.

  14. Measurement of Resistance and Strength of Conductor Splices in the MICE Coupling Magnets

    SciTech Connect (OSTI)

    Xu, Feng Yu; Pan, Heng; Wu, Hong; Lui, X. K.; Li, E.; Dietderich, Dan; Higley, Hugh; Tam, D. G.; Trillaud, Fredric; Wang, Li; Green, M.A.

    2009-08-19T23:59:59.000Z

    The superconducting magnets for the Muon Ionization Cooling Experiment [1] (MICE) use a copper based Nb-Ti conductor with un-insulated dimensions of 0.95 by 1.60 mm. There may be as many as twelve splices in one MICE superconducting coupling coil. These splices are to be wound in the coil. The conductor splices produce Joule heating, which may cause the magnet to quench. A technique of making conductor splices was developed by ICST. Two types of 1-meter long of soldered lap-joints have been tested. Side-by-side splices and up-down one splices were studied theoretically and experimentally using two types of soft solder made of eutectic tin-lead solder and tin-silver solder. The resistances of the splices made by ICST were tested at LBNL at liquid helium temperatures over a range of magnetic fields up to 5 T. The breaking strength of 250 mm long splices was also measured at room temperature and liquid nitrogen temperature.

  15. DC-based magnetic field controller

    DOE Patents [OSTI]

    Kotter, D.K.; Rankin, R.A.; Morgan, J.P.

    1994-05-31T23:59:59.000Z

    A magnetic field controller is described for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a Hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage. 1 fig.

  16. DC-based magnetic field controller

    DOE Patents [OSTI]

    Kotter, Dale K. (Shelley, ID); Rankin, Richard A. (Ammon, ID); Morgan, John P,. (Idaho Falls, ID)

    1994-01-01T23:59:59.000Z

    A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.

  17. Torsional Oscillations of Relativistic Stars with Dipole Magnetic Fields

    E-Print Network [OSTI]

    H. Sotani; K. D. Kokkotas; N. Stergioulas

    2007-10-11T23:59:59.000Z

    We present the formalism and numerical results for torsional oscillations of relativistic stars endowed with a strong dipole magnetic field. We do a systematic search of parameter space by computing torsional mode frequencies for various values of the harmonic index $\\ell$ and for various overtones, using an extended sample of models of compact stars, varying in mass, high-density equation of state and crust model. We show that torsional mode frequencies are sensitive to the crust model if the high-density equation of state is very stiff. In addition, torsional mode frequencies are drastically affected by a dipole magnetic field, if the latter has a strength exceeding roughly $10^{15}$G and we find that the magnetic field effects are sensitive to the adopted crust model. Using our extended numerical results we derive empirical relations for the effect of the magnetic field on torsional modes as well as for the crust thickness. We compare our numerical results to observed frequencies in SGRs and find that certain high-density EoS and mass values are favored over others in the non-magnetized limit. On the other hand, if the magnetic field is strong, then its effect has to be taken into account in attempts to formulate a theory of asteroseismology for magnetars.

  18. Primordial Magnetic Fields in False Vacuum Inflation

    E-Print Network [OSTI]

    A. C. Davis; K. Dimopoulos

    1996-10-25T23:59:59.000Z

    We show that, during false vacuum inflation, a primordial magnetic field can be created, sufficiently strong to seed the galactic dynamo and generate the observed galactic magnetic fields. Considering the inflaton dominated regime, our field is produced by the Higgs-field gradients, resulting from a grand unified phase transition. The evolution of the field is followed from its creation through to the epoch of structure formation, subject to the relevant constraints. We find that it is possible to create a magnetic field of sufficient magnitude, provided the phase transition occurs during the final 5 e-foldings of the inflationary period.

  19. Enhancement of accelerating field of microwave cavities by magnetic insulation

    SciTech Connect (OSTI)

    Stratakis, D.; Gallardo, J.; Palmer, R.B.

    2011-04-15T23:59:59.000Z

    Limitations on the maximum achievable accelerating gradient of microwave cavities can strongly influence the performance, length, and cost of particle accelerators. Gradient limitations are widely believed to be initiated by electron emission from the cavity surfaces. Here, we show that the deleterious effects of field emission are effectively suppressed by applying a tangential magnetic field to the cavity walls. With the aid of numerical simulations we compute the field strength required to insulate an 805 MHz cavity and estimate the cavity's tolerances to typical experimental errors such as magnet misalignments and positioning errors. Then, we review an experimental program, currently under progress, to further study the concept. Finally, we report on two specific examples that illustrate the feasibility of magnetic insulation into prospective particle accelerator applications.

  20. Magnetic fields in anisotropic relativistic stars

    E-Print Network [OSTI]

    Vladimir Folomeev; Vladimir Dzhunushaliev

    2015-02-28T23:59:59.000Z

    Relativistic, spherically symmetric configurations consisting of a gravitating magnetized anisotropic fluid are studied. For such configurations, we obtain static equilibrium solutions with an axisymmetric, poloidal magnetic field produced by toroidal electric currents. The presence of such a field results in small deviations of the shape of the configuration from spherical symmetry. This in turn leads to the modification of an equation for the current and correspondingly to changes in the structure of the internal magnetic field for the systems supported by the anisotropic fluid, in contrast to the case of an isotropic fluid, where such deviations do not affect the magnetic field.

  1. Generation of the magnetic field in jets

    E-Print Network [OSTI]

    V. Urpin

    2006-05-22T23:59:59.000Z

    We consider dynamo action under the combined influence of turbulence and large-scale shear in sheared jets. Shear can stretch turbulent magnetic field lines in such a way that even turbulent motions showing mirror symmetry become suitable for generation of a large-scale magnetic field. We derive the integral induction equation governing the behaviour of the mean field in jets. The main result is that sheared jets may generate a large-scale magnetic field if shear is sufficiently strong. The generated mean field is mainly concentrated in a magnetic sheath surrounding the central region of a jet, and it exhibits sign reversals in the direction of the jet axis. Typically, the magnetic field in a sheath is dominated by the component along the jet that can reach equipartition with the kinetic energy of particles, The field in the central region of jets has a more disordered structure.

  2. Relationship Between Solar Wind Speed and Coronal Magnetic Field Properties

    E-Print Network [OSTI]

    Fujiki, Ken'ichi; Iju, Tomoya; Hakamada, Kazuyuki; Kojima, Masayoshi

    2015-01-01T23:59:59.000Z

    We have studied the relationship between the solar-wind speed $[V]$ and the coronal magnetic-field properties (a flux expansion factor [$f$] and photospheric magnetic-field strength [$B_{\\mathrm{S}}$]) at all latitudes using data of interplanetary scintillation and solar magnetic field obtained for 24 years from 1986 to 2009. Using a cross-correlation analyses, we verified that $V$ is inversely proportional to $f$ and found that $V$ tends to increase with $B_{\\mathrm{S}}$ if $f$ is the same. As a consequence, we find that $V$ has extremely good linear correlation with $B_{\\mathrm{S}}/f$. However, this linear relation of $V$ and $B_{\\mathrm{S}}/f$ cannot be used for predicting the solar-wind velocity without information on the solar-wind mass flux. We discuss why the inverse relation between $V$ and $f$ has been successfully used for solar-wind velocity prediction, even though it does not explicitly include the mass flux and magnetic-field strength, which are important physical parameters for solar-wind accele...

  3. Cyclotron dynamics of interacting bosons in artificial magnetic fields

    E-Print Network [OSTI]

    Xiaopeng Li; S. Das Sarma

    2014-06-24T23:59:59.000Z

    We study theoretically quantum dynamics of interacting bosons in artificial magnetic fields as engineered in recent ultracold atomic experiments, where quantum cyclotron orbital motion has been observed. With exact numerical simulations and perturbative analyses, we find that interactions induce damping in the cyclotron motion. The damping time is found to be dependent on interaction and tunneling strengths monotonically, while its dependence on magnetic flux is non-monotonic. Sufficiently strong interactions would render bosons dynamically localized inhibiting the cyclotron motion. The damping predicted by us can be construed as an interaction-induced quantum decoherence of the cyclotron motion.

  4. Graphene Nanoribbon in Sharply Localized Magnetic Fields

    E-Print Network [OSTI]

    Abdulaziz D. Alhaidari; Hocine Bahlouli; Abderrahim El Mouhafid; Ahmed Jellal

    2013-03-20T23:59:59.000Z

    We study the effect of a sharply localized magnetic field on the electron transport in a strip (ribbon) of graphene sheet, which allows to give results for the transmission and reflection probability through magnetic barriers. The magnetic field is taken as a single and double delta type localized functions, which are treated later as the zero width limit of gaussian fields. For both field configurations, we evaluate analytically and numerically their transmission and reflection coefficients. The possibility of spacial confinement due to the inhomogeneous field configuration is also investigated.

  5. Tunable dynamic response of magnetic gels: impact of structural properties and magnetic fields

    E-Print Network [OSTI]

    Mitsusuke Tarama; Peet Cremer; Dmitry Y. Borin; Stefan Odenbach; Hartmut Löwen; Andreas M. Menzel

    2014-09-24T23:59:59.000Z

    Ferrogels and magnetic elastomers feature mechanical properties that can be reversibly tuned from outside through magnetic fields. Here we concentrate on the question how their dynamic response can be adjusted. The influence of three factors on the dynamic behavior is demonstrated using appropriate minimal models: first, the orientational memory imprinted into one class of the materials during their synthesis; second, the structural arrangement of the magnetic particles in the materials; and third, the strength of an external magnetic field. To illustrate the latter point, structural data are extracted from a real experimental sample and analyzed. Understanding how internal structural properties and external influences impact the dominant dynamical properties helps to design materials that optimize the requested behavior.

  6. Method for the detection of a magnetic field utilizing a magnetic vortex

    DOE Patents [OSTI]

    Novosad, Valentyn (Chicago, IL); Buchanan, Kristen (Batavia, IL)

    2010-04-13T23:59:59.000Z

    The determination of the strength of an in-plane magnetic field utilizing one or more magnetically-soft, ferromagnetic member, having a shape, size and material whereas a single magnetic vortex is formed at remanence in each ferromagnetic member. The preferred shape is a thin circle, or dot. Multiple ferromagnetic members can also be stacked on-top of each other and separated by a non-magnetic spacer. The resulting sensor is hysteresis free. The sensor's sensitivity, and magnetic saturation characteristics may be easily tuned by simply altering the material, size, shape, or a combination thereof to match the desired sensitivity and saturation characteristics. The sensor is self-resetting at remanence and therefore does not require any pinning techniques.

  7. Permanent magnet edge-field quadrupole

    DOE Patents [OSTI]

    Tatchyn, Roman O. (Mountain View, CA)

    1997-01-01T23:59:59.000Z

    Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis.

  8. Faraday Rotation Observations of Magnetic Fields in galaxy Clusters

    E-Print Network [OSTI]

    Tracy E. Clarke

    2004-12-10T23:59:59.000Z

    The presence of magnetic fields in the intracluster medium in clusters of galaxies has been revealed through several different observational techniques. These fields may be dynamically important in clusters as they will provide additional pressure support to the intracluster medium as well as inhibit transport mechanisms such as thermal conduction. Here, we review the current observational state of Faraday rotation measure studies of the cluster fields. The fields are generally found to be a few to 10 microG in non-cooling core clusters and ordered on scales of 10-20 kpc. Studies of sources at large impact parameters show that the magnetic fields extend from cluster cores to radii of at least 500 kpc. In central regions of cooling core systems the field strengths are often somewhat higher (10-40 microG) and appear to be ordered on smaller scales of a few to 10 kpc. We also review some of the recent work on interpreting Faraday rotation measure observations through theory and numerical simulations. These techniques allow us to build up a much more detailed view of the strength and topology of the fields.

  9. Magnetic fields in Neutron Stars

    E-Print Network [OSTI]

    Viganò, Daniele; Miralles, Juan A; Rea, Nanda

    2015-01-01T23:59:59.000Z

    Isolated neutron stars show a diversity in timing and spectral properties, which has historically led to a classification in different sub-classes. The magnetic field plays a key role in many aspects of the neutron star phenomenology: it regulates the braking torque responsible for their timing properties and, for magnetars, it provides the energy budget for the outburst activity and high quiescent luminosities (usually well above the rotational energy budget). We aim at unifying this observational variety by linking the results of the state-of-the-art 2D magneto-thermal simulations with observational data. The comparison between theory and observations allows to place two strong constraints on the physical properties of the inner crust. First, strong electrical currents must circulate in the crust, rather than in the star core. Second, the innermost part of the crust must be highly resistive, which is in principle in agreement with the presence of a novel phase of matter so-called nuclear pasta phase.

  10. Magnetic monopole field exposed by electrons

    E-Print Network [OSTI]

    Béché, A; Van Tendeloo, G; Verbeeck, J

    2013-01-01T23:59:59.000Z

    Magnetic monopoles have provided a rich field of study, leading to a wide area of research in particle physics, solid state physics, ultra-cold gases, superconductors, cosmology, and gauge theory. So far, no true magnetic monopoles were found experimentally. Using the Aharonov-Bohm effect, one of the central results of quantum physics, shows however, that an effective monopole field can be produced. Understanding the effects of such a monopole field on its surroundings is crucial to its observation and provides a better grasp of fundamental physical theory. We realize the diffraction of fast electrons at a magnetic monopole field generated by a nanoscopic magnetized ferromagnetic needle. Previous studies have been limited to theoretical semiclassical optical calculations of the motion of electrons in such a monopole field. Solid state systems like the recently studied 'spin ice' provide a constrained system to study similar fields, but make it impossible to separate the monopole from the material. Free space ...

  11. External-field-free magnetic biosensor

    SciTech Connect (OSTI)

    Li, Yuanpeng; Wang, Yi; Klein, Todd; Wang, Jian-Ping, E-mail: jpwang@umn.edu [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2014-03-24T23:59:59.000Z

    In this paper, we report a magnetic nanoparticle (MNP) detection scheme without the presence of any external magnetic field. The proposed magnetic sensor uses a patterned groove structure within the sensor so that no external magnetic field is needed to magnetize the MNPs. An example is given based on a giant magnetoresistance (GMR) sensing device with a spin valve structure. For this structure, the detection of MNPs located inside the groove and near the free layer is demonstrated under no external magnetic field. Micromagnetic simulations are performed to calculate the signal to noise level of this detection scheme. A maximum signal to noise ratio (SNR) of 18.6?dB from one iron oxide magnetic nanoparticle with 8?nm radius is achieved. As proof of concept, this external-field-free GMR sensor with groove structure of 200?nm?×?200?nm is fabricated using a photo and an electron beam integrated lithography process. Using this sensor, the feasibility demonstration of the detection SNR of 9.3?dB is achieved for 30??l magnetic nanoparticles suspension (30?nm iron oxide particles, 1?mg/ml). This proposed external-field-free sensor structure is not limited to GMR devices and could be applicable to other magnetic biosensing devices.

  12. Enhanced density and magnetic fields in interstellar OH masers

    E-Print Network [OSTI]

    Vincent L. Fish; Mark J. Reid; Karl M. Menten; Thushara Pillai

    2006-08-04T23:59:59.000Z

    Aims: We have observed the 6030 and 6035 MHz transitions of OH in high-mass star-forming regions to obtain magnetic field estimates in both maser emission and absorption. Methods: Observations were taken with the Effelsberg 100 m telescope. Results: Our observations are consistent with previous results, although we do detect a new 6030 MHz maser feature near -70 km/s in the vicinity of W3(OH). In absorption we obtain a possible estimate of -1.1 +/- 0.3 mG for the average line-of-sight component of the magnetic field in the absorbing OH gas in K3-50 and submilligauss upper limits for the line-of-sight field strength in DR 21 and W3. Conclusions: These results indicate that the magnetic field strength in the vicinity of OH masers is higher than that of the surrounding, non-masing material, which in turn suggests that the density of masing OH regions is higher than that of their surroundings.

  13. Colour superconductivity in a strong magnetic field

    E-Print Network [OSTI]

    Efrain J. Ferrer; Vivian de la Incera; Cristina Manuel

    2005-11-30T23:59:59.000Z

    We explore the effects of an applied strong external magnetic field in a three flavour massless colour superconductor. The long-range component of the B field that penetrates the superconductor enhances some quark condensates, leading to a different condensation pattern. The external field also reduces the flavour symmetries in the system, and thus it changes drastically the corresponding low energy physics. Our considerations are relevant for the study of highly magnetized compact stars.

  14. First experiments probing the collision of parallel magnetic fields using laser-produced plasmas

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Rosenberg, M. J.; Li, C. K.; Fox, W.; Igumenshchev, I.; Seguin, F. H.; Town, R. P.; Frenje, J. A.; Stoeckl, C.; Glebov, V.; Petrasso, R. D.

    2015-04-01T23:59:59.000Z

    Novel experiments to study the strongly-driven collision of parallel magnetic fields in ?~10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell (PIC) simulations predict a stronger flux compressionmore »and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.« less

  15. First experiments probing the collision of parallel magnetic fields using laser-produced plasmas

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Rosenberg, M. J. [Plasma Science and Fusion Center and Massachusetts Institute of Technology, Cambridge, MA (United States); Li, C. K. [Plasma Science and Fusion Center and Massachusetts Institute of Technology, Cambridge, MA (United States); Fox, W. [Princeton Plasma Physics Laboratory, Princeton, NJ (United States)] (ORCID:000000016289858X); Igumenshchev, I. [University of Rochester, NY (United States). Laboratory for Laser Energetics; Seguin, F. H. [Plasma Science and Fusion Center and Massachusetts Institute of Technology, Cambridge, MA (United States); Town, R. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Frenje, J. A. [Plasma Science and Fusion Center and Massachusetts Institute of Technology, Cambridge, MA (United States)] (ORCID:0000000168460378); Stoeckl, C. [University of Rochester, NY (United States). Laboratory for Laser Energetics; Glebov, V. [University of Rochester, NY (United States). Laboratory for Laser Energetics; Petrasso, R. D. [Plasma Science and Fusion Center and Massachusetts Institute of Technology, Cambridge, MA (United States)] (ORCID:0000000258834054)

    2015-04-01T23:59:59.000Z

    Novel experiments to study the strongly-driven collision of parallel magnetic fields in ?~10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell (PIC) simulations predict a stronger flux compression and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.

  16. First experiments probing the collision of parallel magnetic fields using laser-produced plasmas

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Rosenberg, M. J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts (United States); Li, C. K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; Fox, W. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA] (ORCID:000000016289858X); Igumenshchev, I. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA; S??guin, F. H. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; Town, R. P. [Lawrence Livermore National Laboratory, Livermore, California 94550, USA; Frenje, J. A. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA] (ORCID:0000000168460378); Stoeckl, C. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA; Glebov, V. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA; Petrasso, R. D. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA] (ORCID:0000000258834054)

    2015-04-01T23:59:59.000Z

    Novel experiments to study the strongly-driven collision of parallel magnetic fields in ß~10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell (PIC) simulations predict a stronger flux compression and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.

  17. Measuring Magnetic Fields Near and Far with the SKA via the Zeeman Effect

    E-Print Network [OSTI]

    Robishaw, Timothy; Surcis, Gabriele; Vlemmings, Wouter; Richards, A M S; Etoka, Sandra; Bourke, Tyler; Fish, Vincent; Gray, Malcolm; Imai, Hiroshi; Kramer, Busaba; McBride, James; Momjian, Emmanuel; Sarma, Anuj; Zijlstra, Albert

    2015-01-01T23:59:59.000Z

    The measurement of Zeeman splitting in spectral lines---both in emission and absorption---can provide direct estimates of the magnetic field strength and direction in atomic and molecular clouds, both in our own Milky Way and in external galaxies. This method will probe the magnetic field in the warm and cold neutral components of the interstellar medium, providing a complement to the extensive SKA Faraday studies planning to probe the field in the ionized components.

  18. Electron-Positron Pair Production by an Electron in a Magnetic Field Near the Process Threshold

    E-Print Network [OSTI]

    O. P. Novak; R. I. Kholodov; P. I. Fomin

    2011-01-13T23:59:59.000Z

    The electron-positron pair production by an electron in a strong magnetic field near the process threshold is considered. The process is shown to be more probable if the spin of the initial electron is oriented along the field. In this case, the probability of the process is $\\sim10^{13} s^{-1}$ when the magnetic field strength is $H=4\\cdot 10^{12}$ G.

  19. ECE 390 Electric & Magnetic Fields Catalog Description: Static and quasi-static electric and magnetic fields.

    E-Print Network [OSTI]

    Engineering Magnetics, ECE 593 Structure: Three 80-minute lectures per week Instructors: A. Weisshaar (primaryECE 390 ­ Electric & Magnetic Fields Catalog Description: Static and quasi-static electric and magnetic fields. Credits: 4 Terms Offered: Fall Prerequisites: MTH 255, ENGR 203 (concurrent enrollment

  20. Apparatus and method for magnetically processing a specimen

    DOE Patents [OSTI]

    Ludtka, Gerard M; Ludtka, Gail M; Wilgen, John B; Kisner, Roger A; Jaramillo, Roger A

    2013-09-03T23:59:59.000Z

    An apparatus for magnetically processing a specimen that couples high field strength magnetic fields with the magnetocaloric effect includes a high field strength magnet capable of generating a magnetic field of at least 1 Tesla and a magnetocaloric insert disposed within a bore of the high field strength magnet. A method for magnetically processing a specimen includes positioning a specimen adjacent to a magnetocaloric insert within a bore of a magnet and applying a high field strength magnetic field of at least 1 Tesla to the specimen and to the magnetocaloric insert. The temperature of the specimen changes during the application of the high field strength magnetic field due to the magnetocaloric effect.

  1. Cryogenic properties of dispersion strengthened copper for high magnetic fields

    SciTech Connect (OSTI)

    Toplosky, V. J.; Han, K.; Walsh, R. P. [National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States); Swenson, C. A. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)

    2014-01-27T23:59:59.000Z

    Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.

  2. Biaxial testing of high strength carbon fiber composite cylinders for pulsed magnet reinforcement

    E-Print Network [OSTI]

    Garmestani, Hamid

    envelope) of composite materials. This methodology was applied to two different carbon/epoxy basedBiaxial testing of high strength carbon fiber composite cylinders for pulsed magnet reinforcement N A methodology is introduced to test carbon-fiber-reinforced, hoop-wound composite cylinders for their biaxial

  3. About the global magnetic fields of stars

    E-Print Network [OSTI]

    Bychkov, V D; Madej, J

    2013-01-01T23:59:59.000Z

    We present a review of observations of the stellar longitudinal (effective) magnetic field ($B_e$) and its properties. This paper also discusses contemporary views on the origin, evolution and structure of $B_e$.

  4. Lunar magnetic field measurements with a cubesat

    E-Print Network [OSTI]

    Garrick-Bethell, Ian

    We have developed a mission concept that uses 3-unit cubesats to perform new measurements of lunar magnetic fields, less than 100 meters above the Moon’s surface. The mission calls for sending the cubesats on impact ...

  5. HIGH-FIELD SUPERCONDUCTING ACCELERATOR MAGNETS

    E-Print Network [OSTI]

    Taylor, C.

    2011-01-01T23:59:59.000Z

    D. C. 'Niobium-Titanium Superconducting Material s ', in S.Nb -Ti and Nb3Sn superconductors. , •• ,""" s. S. Clamp, Tie14, 1982 HIGH-FIELD SUPERCONDUCTING ACCELERATOR MAGNETS C.

  6. Magnetic field imaging with atomic Rb vapor

    E-Print Network [OSTI]

    Eugeniy E. Mikhailov; I. Novikova; M. D. Havey; F. A. Narducci

    2009-07-27T23:59:59.000Z

    We demonstrate the possibility of dynamic imaging of magnetic fields using electromagnetically induced transparency in an atomic gas. As an experimental demonstration we employ an atomic Rb gas confined in a glass cell to image the transverse magnetic field created by a long straight wire. In this arrangement, which clearly reveals the essential effect, the field of view is about 2 x 2 mm^2 and the field detection uncertainty is 0.14 mG per 10 um x 10 um image pixel.

  7. Laminated magnet field coil sheath

    DOE Patents [OSTI]

    Skaritka, J.R.

    1987-05-15T23:59:59.000Z

    A method for manufacturing a magnetic cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible substrate sheath, with the trim coil pattern precisely location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator. 1 fig.

  8. Laminated magnet field coil sheath

    DOE Patents [OSTI]

    Skaritka, John R. (Coram, NY)

    1987-12-01T23:59:59.000Z

    a method for manufacturing a magnet cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible sheath, with the trim coil pattern precisely positioned thereon, is accurately positioned at a precise location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator.

  9. Particle decay in Ising field theory with magnetic field

    E-Print Network [OSTI]

    Gesualdo Delfino

    2007-03-30T23:59:59.000Z

    The scaling limit of the two-dimensional Ising model in the plane of temperature and magnetic field defines a field theory which provides the simplest illustration of non-trivial phenomena such as spontaneous symmetry breaking and confinement. Here we discuss how Ising field theory also gives the simplest model for particle decay. The decay widths computed in this theory provide the obvious test ground for the numerical methods designed to study unstable particles in quantum field theories discretized on a lattice.

  10. Magnetic nanoparticles for applications in oscillating magnetic field

    SciTech Connect (OSTI)

    Peeraphatdit, Chorthip

    2010-12-15T23:59:59.000Z

    Enzymatic and thermochemical catalysis are both important industrial processes. However, the thermal requirements for each process often render them mutually exclusive: thermochemical catalysis requires high temperature that denatures enzymes. One of the long-term goals of this project is to design a thermocatalytic system that could be used with enzymatic systems in situ to catalyze reaction sequences in one pot; this system would be useful for numerous applications e.g. conversion of biomass to biofuel and other commodity products. The desired thermocatalytic system would need to supply enough thermal energy to catalyze thermochemical reactions, while keeping the enzymes from high temperature denaturation. Magnetic nanoparticles are known to generate heat in an oscillating magnetic field through mechanisms including hysteresis and relaxational losses. We envisioned using these magnetic nanoparticles as the local heat source embedded in sub-micron size mesoporous support to spatially separate the particles from the enzymes. In this study, we set out to find the magnetic materials and instrumental conditions that are sufficient for this purpose. Magnetite was chosen as the first model magnetic material in this study because of its high magnetization values, synthetic control over particle size, shape, functionalization and proven biocompatibility. Our experimental designs were guided by a series of theoretical calculations, which provided clues to the effects of particle size, size distribution, magnetic field, frequency and reaction medium. Materials of theoretically optimal size were synthesized, functionalized, and their effects in the oscillating magnetic field were subsequently investigated. Under our conditions, the materials that clustered e.g. silica-coated and PNIPAM-coated iron oxides exhibited the highest heat generation, while iron oxides embedded in MSNs and mesoporous iron oxides exhibited the least bulk heating. It is worth noting that the specific loss power of PNIPAM-coated Fe{sub 3}O{sub 4} was peculiarly high, and the heat loss mechanism of this material remains to be elucidated. Since thermocatalysis is a long-term goal of this project, we also investigated the effects of the oscillating magnetic field system for the synthesis of 7-hydroxycoumarin-3-carboxylic acid. Application of an oscillating magnetic field in the presence of magnetic particles with high thermal response was found to effectively increase the reaction rate of the uncatalyzed synthesis of the coumarin derivative compared to the room temperature control.

  11. Do Magnetic Fields Prevent Hydrogen from Accreting onto Cool Metal-line White Dwarf Stars?

    E-Print Network [OSTI]

    S. Friedrich; S. Jordan; D. Koester

    2004-10-21T23:59:59.000Z

    It is generally assumed that metals detected in the spectra of a few cool white dwarfs cannot be of primordial origin and must be accreted from the interstellar medium. However, the observed abundances of hydrogen, which should also be accreted from the interstellar medium, are lower than expected from metal accretion. Magnetic fields are thought to be the reason for this discrepancy. We have therefore obtained circular polarization spectra of the helium-rich white dwarfs GD40 and L745-46A, which both show strong metal lines as well as hydrogen. Whereas L745-46A might have a magnetic field of about -6900 G, which is about two times the field strength of 3000G necessary to repell hydrogen at the Alfen radius, only an upper limit for the field strength of GD40 of 4000G (with 99% confidence) can be set which is far off the minimum field strength of 144000G to repell hydrogen.

  12. Small-scale primordial magnetic fields and anisotropies in the cosmic microwave background radiation

    SciTech Connect (OSTI)

    Jedamzik, Karsten [Laboratoire de Univers et Particules, UMR5299-CNRS, Université de Montpellier II, F-34095 Montpellier (France); Abel, Tom, E-mail: karsten.jedamzik@um2.fr, E-mail: tabel@slac.stanford.edu [Kavli Institute for Particle Astrophysics and Cosmology, SLAC/Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025 (United States)

    2013-10-01T23:59:59.000Z

    It is shown that small-scale magnetic fields present before recombination induce baryonic density inhomogeneities of appreciable magnitude. The presence of such inhomogeneities changes the ionization history of the Universe, which in turn decreases the angular scale of the Doppler peaks and increases Silk damping by photon diffusion. This unique signature could be used to (dis)prove the existence of primordial magnetic fields of strength as small as B ? 10{sup ?11} Gauss by cosmic microwave background observations.

  13. Radio frequency sheaths in an oblique magnetic field

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Myra, James R.; D'Ippolito, Daniel A.

    2015-06-01T23:59:59.000Z

    The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle ? with the surface. A set of one-dimensional equations is developed that describe the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle, ? assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numericallymore »to obtain the rectified (dc) voltage, the rf voltage across the sheath and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall.« less

  14. Height variation of the vector magnetic field in solar spicules

    E-Print Network [OSTI]

    Suarez, D Orozco; Bueno, J Trujillo

    2015-01-01T23:59:59.000Z

    Proving the magnetic configuration of solar spicules has hitherto been difficult due to the lack of spatial resolution and image stability during off-limb ground-based observations. We report spectropolarimetric observations of spicules taken in the He I 1083 nm spectral region with the Tenerife Infrared Polarimeter II at the German Vacuum Tower Telescope of the Observatorio del Teide (Tenerife; Canary Islands; Spain). The data provide the variation with geometrical height of the Stokes I, Q, U, and V profiles whose encoded information allows the determination of the magnetic field vector by means of the HAZEL inversion code. The inferred results show that the average magnetic field strength at the base of solar spicules is about 80 gauss and then it decreases rapidly with height to about 30 gauss at a height of 3000 km above the visible solar surface. Moreover, the magnetic field vector is close to vertical at the base of the chromosphere and has mid inclinations (about 50 degree) above 2 Mm height.

  15. Plasma heating in a variable magnetic field

    SciTech Connect (OSTI)

    Kichigin, G. N., E-mail: king@iszf.irk.ru [Russian Academy of Sciences, Institute of Solar-Terrestrial Physics (Russian Federation)

    2013-05-15T23:59:59.000Z

    The problem of particle acceleration in a periodically variable magnetic field that either takes a zero value or passes through zero is considered. It is shown that, each time the field [0]passes through zero, the particle energy increases abruptly. This process can be regarded as heating in the course of which plasma particles acquire significant energy within one field period. This mechanism of plasma heating takes place in the absence of collisions between plasma particles and is analogous to the mechanism of magnetic pumping in collisional plasma considered by Alfven.

  16. Hyperon bulk viscosity in strong magnetic fields

    E-Print Network [OSTI]

    Monika Sinha; Debades Bandyopadhyay

    2009-06-06T23:59:59.000Z

    We study the bulk viscosity of neutron star matter including $\\Lambda$ hyperons in the presence of quantizing magnetic fields. Relaxation time and bulk viscosity due to both the non-leptonic weak process involving $\\Lambda$ hyperons and direct Urca processes are calculated here. In the presence of a strong magnetic field of $10^{17}$ G, the hyperon bulk viscosity coefficient is reduced whereas bulk viscosity coefficients due to direct Urca processes are enhanced compared with their field free cases when many Landau levels are populated by protons, electrons and muons.

  17. Dose response of selected ion chambers in applied homogeneous transverse and longitudinal magnetic fields

    SciTech Connect (OSTI)

    Reynolds, M. [Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Fallone, B. G. [Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Departments of Oncology and Physics, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Rathee, S. [Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada)

    2013-04-15T23:59:59.000Z

    Purpose: The magnetic fields of an integrated MR-Linac system will alter the paths of electrons that produce ions in the ionization chambers. The dose response of selected ion chambers is evaluated in the presence of varying transverse and longitudinal magnetic fields. The investigation is useful in calibration of therapeutic x-ray beams associated with MR-Linac systems. Methods: The Monte Carlo code PENELOPE was used to model the irradiation of NE2571, and PR06C ionization chambers in the presence of a transverse and longitudinal (with respect to the photon beam) magnetic fields of varying magnitude. The long axis of each chamber was simulated both parallel and perpendicular to the incident photon beam for each magnetic field case. The dose deposited in each chamber for each case was compared to the case with zero magnetic field by means of a ratio. The PR06C chamber's response was measured in the presence of a transverse magnetic field with field strengths ranging from 0.0 to 0.2 T to compare to simulated results. Results: The simulations and measured data show that in the presence of a transverse magnetic field there is a considerable dose response (maximum of 11% near 1.0 T in the ion chambers investigated, which depends on the magnitude of magnetic field, and relative orientation of the magnetic field, radiation beam, and ion chamber. Measurements made with the PR06C chamber verify these results in the region of measurement. In contrast, a longitudinal magnetic field produces only a slight increase in dose response (2% at 1.5 T) that rises slowly with increasing magnetic field and is seemingly independent of chamber orientation. Response trends were similar for the two ion chambers and relative orientations considered, but slight variations are present from chamber to chamber. Conclusions: Care must be taken when making ion chamber measurements in a transverse magnetic field. Ion chamber responses vary not only with transverse field strength, but with chamber orientation and type, and can be considerable. Longitudinal magnetic fields influence ion chamber responses relatively little (2% at 1.5 T), and only at field strengths in excess of 1.0 T.

  18. Quasi-TEM electromagnetic modes of a plasma waveguide with a nonsimply connected cross section in an external magnetic field

    SciTech Connect (OSTI)

    Kartashov, I. N., E-mail: igorkartashov@mail.ru; Kuzelev, M. V., E-mail: kuzelev@mail.ru [Moscow State University, Physics Department (Russian Federation)

    2014-12-15T23:59:59.000Z

    Electromagnetic modes of a plasma waveguide with a nonsimply connected cross section in an external magnetic field are investigated. The existence of quasi-TEM modes in a finite-strength magnetic field is demonstrated. It is shown that, in the limits of infinitely strong and zero magnetic fields, this mode transforms into a true TEM mode. The possibility of excitation of such modes by an electron beam in the regime of the anomalous Doppler effect is analyzed.

  19. Materials Physics Applications: The National High Magnetic Field...

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Pulsed Magnetic Field Laboratory of the NHMFL in the form of a 1.4 GVA inertial storage motor-generator for high field pulsed magnets. In addition to the 60 Tesla Long Pulse Magnet...

  20. High magnetic field ohmically decoupled non-contact technology

    DOE Patents [OSTI]

    Wilgen, John (Oak Ridge, TN) [Oak Ridge, TN; Kisner, Roger (Knoxville, TN) [Knoxville, TN; Ludtka, Gerard (Oak Ridge, TN) [Oak Ridge, TN; Ludtka, Gail (Oak Ridge, TN) [Oak Ridge, TN; Jaramillo, Roger (Knoxville, TN) [Knoxville, TN

    2009-05-19T23:59:59.000Z

    Methods and apparatus are described for high magnetic field ohmically decoupled non-contact treatment of conductive materials in a high magnetic field. A method includes applying a high magnetic field to at least a portion of a conductive material; and applying an inductive magnetic field to at least a fraction of the conductive material to induce a surface current within the fraction of the conductive material, the surface current generating a substantially bi-directional force that defines a vibration. The high magnetic field and the inductive magnetic field are substantially confocal, the fraction of the conductive material is located within the portion of the conductive material and ohmic heating from the surface current is ohmically decoupled from the vibration. An apparatus includes a high magnetic field coil defining an applied high magnetic field; an inductive magnetic field coil coupled to the high magnetic field coil, the inductive magnetic field coil defining an applied inductive magnetic field; and a processing zone located within both the applied high magnetic field and the applied inductive magnetic field. The high magnetic field and the inductive magnetic field are substantially confocal, and ohmic heating of a conductive material located in the processing zone is ohmically decoupled from a vibration of the conductive material.

  1. The Evolution of Cosmic Magnetic Fields: From the Very Early Universe, to Recombination, to the Present

    E-Print Network [OSTI]

    Robi Banerjee; Karsten Jedamzik

    2004-10-01T23:59:59.000Z

    (abridged) A detailed examination of the evolution of stochastic magnetic fields between high cosmic temperatures and the present epoch is presented. A simple analytical model matching the results of the 3D MHD simulations allows for the prediction of present day magnetic field correlation lengths and energy. Our conclusions are multi fold. (a) Initial primordial fields with only a small amount of helicity are evolving into maximally helical fields. (b) There exists a correlation between the strength of the magnetic field, B, at the peak of it's spectrum and the location of the peak, given at the present epoch by: B ~ 5x10^{-12} (L/kpc) Gauss, where L is the correlation length determined by the initial magnetic field. (c) Concerning studies of generation of cosmic microwave background (CMBR) anisotropies due to primordial magnetic fields of B~10^{-9} Gauss on ~ 10 Mpc scales, such fields are not only impossible to generate in early causal magnetogenesis scenarios but also seemingly ruled out by distortions of the CMBR spectrum due to magnetic field dissipation on smaller scales and the overproduction of cluster magnetic fields. (d) The most promising detection possibility of CMBR distortions due to primordial magnetic fields may be on much smaller scales at higher multipoles l~10^6 where the signal is predicted to be the strongest. (e) It seems possible that magnetic fields in clusters of galaxies are entirely of primordial origin, without invoking dynamo amplification. Such fields would be of (pre-collapse) strength 10^{-12} - 10^{-11} Gauss with correlation lengths in the kpc range, and would also exist in voids of galaxies.

  2. Computing nonlinear force free coronal magnetic fields

    E-Print Network [OSTI]

    T. Wiegelmann; T. Neukirch

    2008-01-21T23:59:59.000Z

    Knowledge of the structure of the coronal magnetic field is important for our understanding of many solar activity phenomena, e.g. flares and CMEs. However, the direct measurement of coronal magnetic fields is not possible with present methods, and therefore the coronal field has to be extrapolated from photospheric measurements. Due to the low plasma beta the coronal magnetic field can usually be assumed to be approximately force free, with electric currents flowing along the magnetic field lines. There are both observational and theoretical reasons which suggest that at least prior to an eruption the coronal magnetic field is in a nonlinear force free state. Unfortunately the computation of nonlinear force free fields is way more difficult than potential or linear force free fields and analytic solutions are not generally available. We discuss several methods which have been proposed to compute nonlinear force free fields and focus particularly on an optimization method which has been suggested recently. We compare the numerical performance of a newly developed numerical code based on the optimization method with the performance of another code based on an MHD relaxation method if both codes are applied to the reconstruction of a semi-analytic nonlinear force-free solution. The optimization method has also been tested for cases where we add random noise to the perfect boundary conditions of the analytic solution, in this way mimicking the more realistic case where the boundary conditions are given by vector magnetogram data. We find that the convergence properties of the optimization method are affected by adding noise to the boundary data and we discuss possibilities to overcome this difficulty.

  3. MAGNETIC FIELDS FROM QCD PHASE TRANSITIONS

    SciTech Connect (OSTI)

    Tevzadze, Alexander G. [Faculty of Exact and Natural Sciences, Javakhishvili Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi 0128 (Georgia); Kisslinger, Leonard; Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Brandenburg, Axel, E-mail: aleko@tevza.org [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

    2012-11-01T23:59:59.000Z

    We study the evolution of QCD phase transition-generated magnetic fields (MFs) in freely decaying MHD turbulence of the expanding universe. We consider an MF generation model that starts from basic non-perturbative QCD theory and predicts stochastic MFs with an amplitude of the order of 0.02 {mu}G and small magnetic helicity. We employ direct numerical simulations to model the MHD turbulence decay and identify two different regimes: a 'weakly helical' turbulence regime, when magnetic helicity increases during decay, and 'fully helical' turbulence, when maximal magnetic helicity is reached and an inverse cascade develops. The results of our analysis show that in the most optimistic scenario the magnetic correlation length in the comoving frame can reach 10 kpc with the amplitude of the effective MF being 0.007 nG. We demonstrate that the considered model of magnetogenesis can provide the seed MF for galaxies and clusters.

  4. Concerning the existence of a 'turbulent' magnetic field in the quiet Sun

    E-Print Network [OSTI]

    R. Manso Sainz; E. Landi Degl'Innocenti; J. Trujillo Bueno

    2004-08-19T23:59:59.000Z

    We report on the a5F-y5F* multiplet of Ti I and its interest for the study of 'turbulent' magnetic fields in the quiet solar photosphere. In particular, we argue that the sizable scattering polarization signal of the 4536 \\AA line (whose lower and upper levels have Land\\'e factors equal to zero), relative to the rest of the lines in the multiplet, gives direct evidence for the existence of an ubiquitous, unresolved magnetic field. We cannot determine precisely the strength of the magnetic field, but its very existence is evidenced by the differential Hanle effect technique that this Ti I multiplet provides.

  5. Nonlinear Evolution of Cosmic Magnetic Fields and Cosmic Microwave Background Anisotropies

    E-Print Network [OSTI]

    Hiroyuki Tashiro; Naoshi Sugiyama; Robi Banerjee

    2006-01-14T23:59:59.000Z

    In this work we investigate the effects of the primordial magnetic fields on cosmic microwave background anisotropies (CMB). Based on cosmological magnetohydrodynamic (MHD) simulations we calculate the CMB anisotropy spectra and polarization induced by fluid fluctuations (Alfv\\'en modes) generated by primordial magnetic fields. The strongest effect on the CMB spectra comes from the transition epoch from a turbulent regime to a viscous regime. The balance between magnetic and kinetic energy until the onset of the viscous regime provides a one to one relation between the comoving coherence length $L$ and the comoving magnetic field strength $B$, such as $L \\sim 30 (B/10^{-9}{\\rm G})^3 \\rm pc$. The resulting CMB temperature and polarization anisotropies are somewhat different from the ones previously obtained by using linear perturbation theory. Our calculation gives a constraint on the magnetic field strength in the intermediate scale of CMB observations. Upper limits are set by WMAP and BOOMERANG results for comoving magnetic field strength of $B 0.7 \\rm Mpc$ for the most extreme case, or $B 0.8 \\rm Mpc$ for the most conservative case.

  6. Periodicity of the solar full-disk magnetic fields

    SciTech Connect (OSTI)

    Xiang, N. B.; Qu, Z. N.; Zhai, Q. [National Astronomical Observatories/Yunnan Observatory, CAS, Kunming 650011 (China)

    2014-07-01T23:59:59.000Z

    A full-disk solar magnetogram has been measured each day since 1970 January 19, and the daily Magnetic Plage Strength Index (MPSI) and the daily Mount Wilson Sunspot Index (MWSI) were calculated for each magnetogram at the Mount Wilson Observatory. The MPSI and MWSI are used to investigate the periodicity of the solar full-disk magnetic activity through autocorrelation analyses. Just two periods, the solar cycle and the rotation cycle, are determined in both the MPSI (the solar full-disk weak magnetic field activity) and MWSI (the solar full-disk strong magnetic field activity) with no annual signal found. The solar cycle for MPSI (10.83 yr) is found to be obviously longer than that for MWSI (9.77 yr). The rotation cycle is determined to be 26.8 ± 0.63 sidereal days for MPSI and 27.4 ± 2.4 sidereal days for MWSI. The rotation cycle length for MPSI is found to fluctuate around 27 days within a very small amplitude, but for MWSI it obviously temporally varies with a rather large amplitude. The rotation cycle for MWSI seems longer near solar minimum than at solar maximum. Cross-correlation analyses of daily MPSI and MWSI are carried out, and it is inferred that the MPSI components partly come from relatively early MWSI measurements.

  7. THE MAGNETIC FIELD IN TAURUS PROBED BY INFRARED POLARIZATION

    SciTech Connect (OSTI)

    Chapman, Nicholas L.; Goldsmith, Paul F.; Pineda, Jorge L.; Li Di [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 301-429, Pasadena, CA 91109 (United States); Clemens, D. P. [Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Krco, Marko, E-mail: nchapman@u.northwestern.edu [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)

    2011-11-01T23:59:59.000Z

    We present maps of the plane-of-sky magnetic field within two regions of the Taurus molecular cloud: one in the dense core L1495/B213 filament and the other in a diffuse region to the west. The field is measured from the polarization of background starlight seen through the cloud. In total, we measured 287 high-quality near-infrared polarization vectors in these regions. In L1495/B213, the percent polarization increases with column density up to A{sub V} {approx} 9 mag, the limits of our data. The radiative torques model for grain alignment can explain this behavior, but models that invoke turbulence are inconsistent with the data. We also combine our data with published optical and near-infrared polarization measurements in Taurus. Using this large sample, we estimate the strength of the plane-of-sky component of the magnetic field in nine subregions. This estimation is done with two different techniques that use the observed dispersion in polarization angles. Our values range from 5 to 82 {mu}G and tend to be higher in denser regions. In all subregions, the critical index of the mass-to-magnetic flux ratio is sub-unity, implying that Taurus is magnetically supported on large scales ({approx}2 pc). Within the region observed, the B213 filament takes a sharp turn to the north and the direction of the magnetic field also takes a sharp turn, switching from being perpendicular to the filament to becoming parallel. This behavior can be understood if we are observing the rim of a bubble. We argue that it has resulted from a supernova remnant associated with a recently discovered nearby gamma-ray pulsar.

  8. 600-T Magnetic Fields due to Cold Electron Flow in a simple Cu-Coil irradiated by High Power Laser pulses

    E-Print Network [OSTI]

    Zhu, Baojun; Yuan, Dawei; Li, Yanfei; Li, Fang; Liao, Guoqian; Zhao, Jiarui; Zhong, Jiayong; Xue, Feibiao; Wei, Huigang; Zhang, Kai; Han, Bo; Pei, Xiaoxing; Liu, Chang; Zhang, Zhe; Wang, Weimin; Zhu, Jianqiang; Zhao, Gang; Zhang, Jie

    2015-01-01T23:59:59.000Z

    A new simple mechanism due to cold electron flow to produce strong magnetic field is proposed. A 600-T strong magnetic field is generated in the free space at the laser intensity of 5.7x10^15 Wcm^-2. Theoretical analysis indicates that the magnetic field strength is proportional to laser intensity. Such a strong magnetic field offers a new experimental test bed to study laser-plasma physics, in particular, fast-ignition laser fusion research and laboratory astrophysics.

  9. Electric-Field Control of Magnetism Intrinsic magnetoelectric coupling describes the microscopic interaction between magnetic and

    E-Print Network [OSTI]

    Maroncelli, Mark

    Electric-Field Control of Magnetism Intrinsic magnetoelectric coupling describes the microscopic interaction between magnetic and electric polarization in a single-phase material. The control of the magnetic of the two interactions. Moderate biaxial compression precipitates local magnetic competition

  10. Sensor for detecting changes in magnetic fields

    DOE Patents [OSTI]

    Praeg, W.F.

    1980-02-26T23:59:59.000Z

    A sensor is described for detecting changes in the magnetic field of the equilibrium-field coil of a Tokamak plasma device that comprises a pair of bifilar wires disposed circumferentially, one inside and one outside the equilibrium-field coil. Each is shorted at one end. The difference between the voltages detected at the other ends of the bifilar wires provides a measure of changing flux in the equilibrium-field coil. This difference can be used to detect faults in the coil in time to take action to protect the coil.

  11. Sensor for detecting changes in magnetic fields

    DOE Patents [OSTI]

    Praeg, Walter F. (Palos Park, IL)

    1981-01-01T23:59:59.000Z

    A sensor for detecting changes in the magnetic field of the equilibrium-field coil of a Tokamak plasma device comprises a pair of bifilar wires disposed circumferentially, one inside and one outside the equilibrium-field coil. Each is shorted at one end. The difference between the voltages detected at the other ends of the bifilar wires provides a measure of changing flux in the equilibrium-field coil. This difference can be used to detect faults in the coil in time to take action to protect the coil.

  12. Superconducting Magnet Division

    E-Print Network [OSTI]

    Gupta, Ramesh

    Superconducting Magnet Division Permanent Magnet Designs with Large Variations in Field Strength the residual field of the magnetized bricks by concentrating flux lines at the iron pole. Low Field Design Medium Field Design Superconducting Magnet Division Dipole and Quadrupole Magnets for RHIC e

  13. Fast field mapping device for cyclotron magnets

    SciTech Connect (OSTI)

    Berkes, B.; Brombach, D.; Szavits, O.

    1981-09-01T23:59:59.000Z

    The Swiss S.I.N. ring injector cyclotron has four sector magnets. For fast and accurate magnetic field measurements a new type of measuring system has been developed. The magnetic field of the sector magnets is measured in polar coordinates. The standard field map covers a range in radial direction from 240 to 3800 mm and in azimuthal direction from -47 deg. to +47 deg. in steps of 20 mm and 1/4 deg., respectively. Two Hall probes are mounted on a carriage which follows a meandric track. The data are taken in the ''flying'' mode, i.e. two fast DVM's read the values while the carriage is moving at an average speed of approx. 25 cm/sec. The measuring procedure is controlled on line by a small computer and is carried through automatically within roughly 2/one-half/ hr. The process control software contains diagnostic routines for surveying the operation as well as for a smoothing check of the measured data which are written on a magnetic tape at the end of each radial track. 3 refs.

  14. Magnetic fields and density functional theory

    SciTech Connect (OSTI)

    Salsbury Jr., Freddie

    1999-02-01T23:59:59.000Z

    A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susceptibilities. There are the first such functionals ever proposed. These parameters have been studied by constructing functionals for the current density and then using the Biot-Savart equations to obtain the responses. In order to examine the advantages and disadvantages of the local functionals, they were tested numerically on some small molecules.

  15. Magnetic field-line lengths inside interplanetary magnetic flux ropes

    E-Print Network [OSTI]

    Hu, Qiang; Krucker, Sam

    2015-01-01T23:59:59.000Z

    We report on the detailed and systematic study of field-line twist and length distributions within magnetic flux ropes embedded in Interplanetary Coronal Mass Ejections (ICMEs). The Grad-Shafranov reconstruction method is utilized together with a constant-twist nonlinear force-free (Gold-Hoyle) flux rope model to reveal the close relation between the field-line twist and length in cylindrical flux ropes, based on in-situ Wind spacecraft measurements. We show that the field-line twist distributions within interplanetary flux ropes are inconsistent with the Lundquist model. In particular we utilize the unique measurements of magnetic field-line lengths within selected ICME events as provided by Kahler et al. (2011) based on energetic electron burst observations at 1 AU and the associated type III radio emissions detected by the Wind spacecraft. These direct measurements are compared with our model calculations to help assess the flux-rope interpretation of the embedded magnetic structures. By using the differen...

  16. Circular polarization of obliquely propagating whistler wave magnetic field

    SciTech Connect (OSTI)

    Bellan, P. M. [Applied Physics, Caltech, Pasadena California 91125 (United States)] [Applied Physics, Caltech, Pasadena California 91125 (United States)

    2013-08-15T23:59:59.000Z

    The circular polarization of the magnetic field of obliquely propagating whistler waves is derived using a basis set associated with the wave partial differential equation. The wave energy is mainly magnetic and the wave propagation consists of this magnetic energy sloshing back and forth between two orthogonal components of magnetic field in quadrature. The wave electric field energy is small compared to the magnetic field energy.

  17. Measurement of Magnetic Field Using Collaborative AUVs

    E-Print Network [OSTI]

    Idaho, University of

    Measurement of Magnetic Field Using Collaborative AUVs Jesse Pentzer, Brendan Crosbie, Thomas Bean, tests using multiple types of AUVs to individually sample bathymetric data and water mass properties, salinity, and temperature data was reported [2]. In 2007, an AUV was equipped to measure water properties

  18. Electro-Mechanical Resonant Magnetic Field Sensor

    E-Print Network [OSTI]

    Temnykh, A B; Temnykh, Alexander B.; Lovelace, Richard V. E.

    2002-01-01T23:59:59.000Z

    We describe a new type of magnetic field sensor which is termed an Electro-Mechanical Resonant Sensor (EMRS). The key part of this sensor is a small conductive elastic element with low damping rate and therefore a high Q fundamental mode of frequency $f_1$. An AC current is driven through the elastic element which, in the presence of a magnetic field, causes an AC force on the element. When the frequency of the AC current matches the resonant frequency of the element, maximum vibration of the element occurs and this can be measured precisely by optical means. We have built and tested a model sensor of this type using for the elastic element a length of copper wire of diameter 0.030 mm formed into a loop shape. The wire motion was measured using a light emitting diode photo-transistor assembly. This sensor demonstrated a sensitivity better than 0.001G for an applied magnetic field of $ \\sim 1$G and a good selectivity for the magnetic field direction. The sensitivity can be easily improved by a factor of $\\sim ...

  19. Generation of large-scale magnetic fields from inflation in teleparallelism

    SciTech Connect (OSTI)

    Bamba, Kazuharu [Kobayashi-Maskawa Institute for the Origin of Particles and the Universe, Nagoya University, Nagoya 464-8602 (Japan); Geng, Chao-Qiang; Luo, Ling-Wei, E-mail: bamba@kmi.nagoya-u.ac.jp, E-mail: geng@phys.nthu.edu.tw, E-mail: d9622508@oz.nthu.edu.tw [Department of Physics, National Tsing Hua University, Hsinchu, 300, Taiwan (China)

    2012-10-01T23:59:59.000Z

    We explore the generation of large-scale magnetic fields from inflation in teleparallelism, in which the gravitational theory is described by the torsion scalar instead of the scalar curvature in general relativity. In particular, we examine the case that the conformal invariance of the electromagnetic field during inflation is broken by a non-minimal gravitational coupling between the torsion scalar and the electromagnetic field. It is shown that for a power-law type coupling, the magnetic field on 1 Mpc scale with its strength of ? 10{sup ?9} G at the present time can be generated.

  20. General relativistic simulations of black hole-neutron star mergers: Effects of magnetic fields

    E-Print Network [OSTI]

    Zachariah B. Etienne; Yuk Tung Liu; Vasileios Paschalidis; Stuart L. Shapiro

    2012-05-15T23:59:59.000Z

    As a neutron star (NS) is tidally disrupted by a black hole (BH) companion at the end of a BH-NS binary inspiral, its magnetic fields will be stretched and amplified. If sufficiently strong, these magnetic fields may impact the gravitational waveforms, merger evolution and mass of the remnant disk. Formation of highly-collimated magnetic field lines in the disk+spinning BH remnant may launch relativistic jets, providing the engine for a short-hard GRB. We analyze this scenario through fully general relativistic, magnetohydrodynamic (GRMHD) BHNS simulations from inspiral through merger and disk formation. Different initial magnetic field configurations and strengths are chosen for the NS interior for both nonspinning and moderately spinning (a/M=0.75) BHs aligned with the orbital angular momentum. Only strong interior (Bmax~10^17 G) initial magnetic fields in the NS significantly influence merger dynamics, enhancing the remnant disk mass by 100% and 40% in the nonspinning and spinning BH cases, respectively. However, detecting the imprint of even a strong magnetic field may be challenging for Advanced LIGO. Though there is no evidence of mass outflows or magnetic field collimation during the preliminary simulations we have performed, higher resolution, coupled with longer disk evolutions and different initial magnetic field configurations, may be required to definitively assess the possibility of BHNS binaries as short-hard GRB progenitors.

  1. Zeeman tomography of magnetic white dwarfs, I. Reconstruction of the field geometry from synthetic spectra

    E-Print Network [OSTI]

    F. Euchner; S. Jordan; K. Beuermann; B. T. Gaensicke; F. V. Hessmann

    2002-05-21T23:59:59.000Z

    We have computed optical Zeeman spectra of magnetic white dwarfs for field strengths between 10 and 200MG and effective temperatures between 8000 and 40000K. They form a database containing 20628 sets of flux and circular polarization spectra. A least-squares optimization code based on an evolutionary strategy can recover relatively complex magnetic field topologies from phase-resolved synthetic Zeeman spectra of rotating magnetic white dwarfs. We consider dipole and quadrupole components which are non-aligned and shifted off-centre. The model geometries include stars with a single high-field spot and with two spots separated by approx. 90 degrees. The accuracy of the recovered field structure increases with the signal-to-noise ratio of the input spectra and is significantly improved if circular polarization spectra are included in addition to flux spectra. We discuss the strategies proposed so far to unravel the field geometries of magnetic white dwarfs.

  2. The Magnificent Seven: Nearby Isolated Neutron Stars with strong Magnetic Fields

    E-Print Network [OSTI]

    F. Haberl

    2005-10-17T23:59:59.000Z

    Although the true origin of the broad absorption lines in X-ray spectra of thermal isolated neutron stars is not clear yet, our current knowledge about the "magnificent seven" strongly suggests that they are highly magnetized ($10^{13} - 10^{14}$ G), slowly rotating cooling neutron stars. Further timing studies would be very useful to obtain more independent estimates of the magnetic field strength (as they currently only exist from RX J0720.4-3125).

  3. The measurement and analysis of the magnetic field of a synchrotron light source magnet 

    E-Print Network [OSTI]

    Graf, Udo Werner

    1994-01-01T23:59:59.000Z

    In this thesis a unique system is used to measure the magnetic field of a superconducting synchrotron light source magnet. The magnet measured is a superferric dipole C-magnet designed to produce a magnetic field up to 3 Tesla in magnitude. Its...

  4. Primordial magnetic field amplification from turbulent reheating

    SciTech Connect (OSTI)

    Calzetta, Esteban [Departamento de Física, FCEyN-UBA and IFIBA-CONICET, Cdad. Universitaria, Buenos Aires (Argentina); Kandus, Alejandra, E-mail: calzetta@df.uba.ar, E-mail: kandus@uesc.br [LATO - DCET - UESC. Rodovia Ilhéus-Itabuna, km 16 s/n, CEP: 45662-900, Salobrinho, Ilhéus-BA (Brazil)

    2010-08-01T23:59:59.000Z

    We analyze the possibility of primordial magnetic field amplification by a stochastic large scale kinematic dynamo during reheating. We consider a charged scalar field minimally coupled to gravity. During inflation this field is assumed to be in its vacuum state. At the transition to reheating the state of the field changes to a many particle/anti-particle state. We characterize that state as a fluid flow of zero mean velocity but with a stochastic velocity field. We compute the scale-dependent Reynolds number Re(k), and the characteristic times for decay of turbulence, t{sub d} and pair annihilation t{sub a}, finding t{sub a} << t{sub d}. We calculate the rms value of the kinetic helicity of the flow over a scale L and show that it does not vanish. We use this result to estimate the amplification factor of a seed field from the stochastic kinematic dynamo equations. Although this effect is weak, it shows that the evolution of the cosmic magnetic field from reheating to galaxy formation may well be more complex than as dictated by simple flux freezing.

  5. Journal of Magnetism and Magnetic Materials 281 (2004) 272275 Effects of high magnetic field annealing on texture and

    E-Print Network [OSTI]

    Garmestani, Hamid

    Journal of Magnetism and Magnetic Materials 281 (2004) 272­275 Effects of high magnetic field annealing on texture and magnetic properties of FePd D.S. Lia, *, H. Garmestania , Shi-shen Yanb , M China c National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Drive

  6. Magnetic susceptibility and magnetization properties of asymmetric nuclear matter under a strong magnetic field

    E-Print Network [OSTI]

    A. Rabhi; M. A. Pérez-García; C. Providência; I. Vidaña

    2014-10-10T23:59:59.000Z

    We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields $B \\sim 10^{16} - 10^{17}$ G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for $B > 10^{16}$ G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.

  7. Magnetic Fields in Population III Star Formation

    SciTech Connect (OSTI)

    Turk, Matthew J.; Oishi, Jeffrey S.; Abel, Tom; Bryan, Greg

    2012-02-22T23:59:59.000Z

    We study the buildup of magnetic fields during the formation of Population III star-forming regions, by conducting cosmological simulations from realistic initial conditions and varying the Jeans resolution. To investigate this in detail, we start simulations from identical initial conditions, mandating 16, 32 and 64 zones per Jeans length, and studied the variation in their magnetic field amplification. We find that, while compression results in some amplification, turbulent velocity fluctuations driven by the collapse can further amplify an initially weak seed field via dynamo action, provided there is sufficient numerical resolution to capture vortical motions (we find this requirement to be 64 zones per Jeans length, slightly larger than, but consistent with previous work run with more idealized collapse scenarios). We explore saturation of amplification of the magnetic field, which could potentially become dynamically important in subsequent, fully-resolved calculations. We have also identified a relatively surprising phenomena that is purely hydrodynamic: the higher-resolved simulations possess substantially different characteristics, including higher infall-velocity, increased temperatures inside 1000 AU, and decreased molecular hydrogen content in the innermost region. Furthermore, we find that disk formation is suppressed in higher-resolution calculations, at least at the times that we can follow the calculation. We discuss the effect this may have on the buildup of disks over the accretion history of the first clump to form as well as the potential for gravitational instabilities to develop and induce fragmentation.

  8. Advances in Zero-Field Nuclear Magnetic Resonance Spectroscopy

    E-Print Network [OSTI]

    Theis, Thomas

    2012-01-01T23:59:59.000Z

    systems: fully labeled acetonitrile Comparable strength offor fully labeled acetonitrile Significance of near-zero-near-zero-field spectra for acetonitrile-2 ( 13 CH 3 CN) are

  9. Control of stochasticity in magnetic field lines

    E-Print Network [OSTI]

    Cristel Chandre; Michel Vittot; Guido Ciraolo; Philippe Ghendrih; Ricardo Lima

    2005-11-03T23:59:59.000Z

    We present a method of control which is able to create barriers to magnetic field line diffusion by a small modification of the magnetic perturbation. This method of control is based on a localized control of chaos in Hamiltonian systems. The aim is to modify the perturbation locally by a small control term which creates invariant tori acting as barriers to diffusion for Hamiltonian systems with two degrees of freedom. The location of the invariant torus is enforced in the vicinity of the chosen target. Given the importance of confinement in magnetic fusion devices, the method is applied to two examples with a loss of magnetic confinement. In the case of locked tearing modes, an invariant torus can be restored that aims at showing the current quench and therefore the generation of runaway electrons. In the second case, the method is applied to the control of stochastic boundaries allowing one to define a transport barrier within the stochastic boundary and therefore to monitor the volume of closed field lines.

  10. Axion production and CMB spectral distortion in cosmological tangled magnetic field

    E-Print Network [OSTI]

    Damian Ejlli

    2015-04-01T23:59:59.000Z

    Axion production due to photon-axion mixing in tangled magnetic field(s) prior to recombination epoch and magnetic field damping can generate cosmic microwave background (CMB) spectral distortions. In particular, contribution of both processes to CMB $\\mu$ distortion in the case of resonant photon-axion mixing is studied. Assuming that magnetic field power spectrum is approximated by a power law $P_B(k)\\propto k^n$ with spectral index $n$, it is shown that for magnetic field cut-off scales $172.5$ pc $\\leq \\lambda_B\\leq 4\\times 10^3$ pc, axion contribution to CMB $\\mu$ distortion is subdominant in comparison with magnetic field damping in the cosmological plasma. Using COBE upper limit on $\\mu$ and for magnetic field scale $\\lambda_B\\simeq 415$ pc, weaker limit in comparison with other studies on the magnetic field strength ($B_0\\leq 8.5\\times 10^{-8}$ G) up to a factor 10 for the DFSZ axion model and axion mass $m_a\\geq 2.6\\times 10^{-6}$ eV is found. A forecast for the expected sensitivity of PIXIE/PRISM on $\\mu$ is also presented.

  11. Axion production and CMB spectral distortion in cosmological tangled magnetic field

    E-Print Network [OSTI]

    Ejlli, Damian

    2015-01-01T23:59:59.000Z

    Axion production due to photon-axion mixing in tangled magnetic field(s) prior to recombination epoch and magnetic field damping can generate cosmic microwave background (CMB) spectral distortions. In particular, contribution of both processes to CMB $\\mu$ distortion in the case of resonant photon-axion mixing is studied. Assuming that magnetic field power spectrum is approximated by a power law $P_B(k)\\propto k^n$ with spectral index $n$, it is shown that for magnetic field cut-off scales $172.5$ pc $\\leq \\lambda_B\\leq 4\\times 10^3$ pc, axion contribution to CMB $\\mu$ distortion is subdominant in comparison with magnetic field damping in the cosmological plasma. Using COBE upper limit on $\\mu$ and for magnetic field scale $\\lambda_B\\simeq 415$ pc, weaker limit in comparison with other studies on the magnetic field strength ($B_0\\leq 8.5\\times 10^{-8}$ G) up to a factor 10 for the DFSZ axion model and axion mass $m_a\\geq 2.6\\times 10^{-6}$ eV is found. A forecast for the expected sensitivity of PIXIE/PRISM on...

  12. Solar magnetic fields and terrestrial climate

    E-Print Network [OSTI]

    Georgieva, Katya; Kirov, Boian

    2014-01-01T23:59:59.000Z

    Solar irradiance is considered one of the main natural factors affecting terrestrial climate, and its variations are included in most numerical models estimating the effects of natural versus anthropogenic factors for climate change. Solar wind causing geomagnetic disturbances is another solar activity agent whose role in climate change is not yet fully estimated but is a subject of intense research. For the purposes of climate modeling, it is essential to evaluate both the past and the future variations of solar irradiance and geomagnetic activity which are ultimately due to the variations of solar magnetic fields. Direct measurements of solar magnetic fields are available for a limited period, but can be reconstructed from geomagnetic activity records. Here we present a reconstruction of total solar irradiance based on geomagnetic data, and a forecast of the future irradiance and geomagnetic activity relevant for the expected climate change.

  13. Localized Magnetic Fields in Arbitrary Directions Using Patterned Nanomagnets

    E-Print Network [OSTI]

    Dunin-Borkowski, Rafal E.

    with the option of applying electric fields, for example, to move a quantum dot between regions where the magnetic magnetic films have a long history, for example, in bubble memory,6 but on scales required for spintronic electric fields, for example, to move a quantum dot between regions where the magnetic-field direction

  14. Mapping the magnetic field vector in a fountain clock

    SciTech Connect (OSTI)

    Gertsvolf, Marina; Marmet, Louis [National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada)

    2011-12-15T23:59:59.000Z

    We show how the mapping of the magnetic field vector components can be achieved in a fountain clock by measuring the Larmor transition frequency in atoms that are used as a spatial probe. We control two vector components of the magnetic field and apply audio frequency magnetic pulses to localize and measure the field vector through Zeeman spectroscopy.

  15. The Use of Small Coolers in a Magnetic Field

    SciTech Connect (OSTI)

    Green, Michael A.; Witte, Holger

    2007-07-25T23:59:59.000Z

    Small 4 K coolers are used to cool superconducting magnets.These coolers are usually used with high temperature suerconductor (HTS)leads. In most cases, magnet is shielded with iron or active shieldcoils. Thus the field at the cooler is low. There are instances when thecooler must be in a magnetic field. Gifford McMahon (GM) coolers or pulsetube coolers are commercially available to cool the magnets. This paperwill discuss how the two types of coolers are affected by the straymagnetic field. Strategies for using coolers on magnets that generatestray magnetic fields are discussed.

  16. On the control of solidification using magnetic fields and magnetic field Baskar Ganapathysubramanian and Nicholas Zabaras1

    E-Print Network [OSTI]

    Zabaras, Nicholas J.

    On the control of solidification using magnetic fields and magnetic field gradients Baskar and Aerospace Engineering, 188 Frank H.T. Rhodes Hall, Cornell University, Ithaca, NY 14853-3801, USA Abstract solidified material can be suitably affected. Most of the magnetic field approaches to melt flow control rely

  17. Magnetic helicity generation from the cosmic axion field

    SciTech Connect (OSTI)

    Campanelli, L.; Giannotti, M. [Dipartimento di Fisica, Universita di Ferrara, I-44100 Ferrara (Italy); INFN-Sezione di Ferrara, I-44100 Ferrara (Italy)

    2005-12-15T23:59:59.000Z

    The coupling between a primordial magnetic field and the cosmic axion field generates a helical component of the magnetic field around the time in which the axion starts to oscillate. If the energy density of the seed magnetic field is comparable to the energy density of the universe at that time, then the resulting magnetic helicity is about vertical bar H{sub B} vertical bar {approx_equal}(10{sup -20}G){sup 2} kpc and remains constant after its generation. As a corollary, we find that the standard properties of the oscillating axion remain unchanged even in the presence of very strong magnetic fields.

  18. Magnetic Helicity Generation from the Cosmic Axion Field

    E-Print Network [OSTI]

    L. Campanelli; M. Giannotti

    2005-12-12T23:59:59.000Z

    The coupling between a primordial magnetic field and the cosmic axion field generates a helical component of the magnetic field around the time in which the axion starts to oscillate. If the energy density of the seed magnetic field is comparable to the energy density of the universe at that time, then the resulting magnetic helicity is about |H_B| \\simeq (10^{-20} G)^2 kpc and remains constant after its generation. As a corollary, we find that the standard properties of the oscillating axion remain unchanged even in the presence of very strong magnetic fields.

  19. Stationary components of HeI in strong magnetic fields - a tool to identify magnetic DB white dwarfs

    E-Print Network [OSTI]

    S. Jordan; P. Schmelcher; W. Becken

    2001-06-29T23:59:59.000Z

    In only three of the 61 known magnetic white dwarfs helium has been identified unambiguously while about 20% of all non-magnetic stars of this class are known to contain HeI or HeII. Until recently, data for HeI data were available only for magnetic fields below 20MG. This changed with the publication of extensive data by the group in Heidelberg. The corresponding calculations have now been completed for the energetically lowest five states of singlet and triplet symmetry for the subspaces with |m| <= 3; selected calculations have been performed for even higher excitations. In strongly magnetized white dwarfs only line components are visible whose wavelengths vary slowly with respect to the magnetic field, particularly stationary components which have a wavelength minimum or maximum in the range of the magnetic fields strengths on the stellar surface. In view of the many ongoing surveys finding white dwarfs we want to provide the astronomical community with a tool to identify helium in white dwarfs for fields up to 5.3GG. To this end we present all calculated helium line components whose wavelengths in the UV, optical, and near IR vary slowly enough with respect to the field strength to produce visible absorption features. We also list all stationary line components in this spectral range. Finally, we find series of minima and maxima which occur as a result of series of extremal transitions to increasingly higher excitations. We estimated the limits for 8 series which can possibly give rise to additional absorption in white dwarf spectra; one strong absorption feature in GD229 which is yet unexplained by stationary components is very close to two estimated series limits.

  20. Magnetic Field Evolution in Superconducting Neutron Stars

    E-Print Network [OSTI]

    Graber, Vanessa; Glampedakis, Kostas; Lander, Samuel K

    2015-01-01T23:59:59.000Z

    The presence of superconducting and superfluid components in the core of mature neutron stars calls for the rethinking of a number of key magnetohydrodynamical notions like resistivity, the induction equation, magnetic energy and flux-freezing. Using a multi-fluid magnetohydrodynamics formalism, we investigate how the magnetic field evolution is modified when neutron star matter is composed of superfluid neutrons, type-II superconducting protons and relativistic electrons. As an application of this framework, we derive an induction equation where the resistive coupling originates from the mutual friction between the electrons and the vortex/fluxtube arrays of the neutron and proton condensates. The resulting induction equation allows the identification of two timescales that are significantly different from those of standard magnetohydrodynamics. The astrophysical implications of these results are briefly discussed.

  1. MAGNETIC FIELD STRUCTURE IN A HIGH-MASS OUTFLOW/DISK SYSTEM

    SciTech Connect (OSTI)

    Beuther, H. [Max-Planck-Institute for Astronomy, Koenigstuhl 17, 69117 Heidelberg (Germany); Vlemmings, W. H. T. [Argelander Institute for Astronomy, University of Bonn, Auf dem Huegel 71, 53121 Bonn (Germany); Rao, R. [Academia Sinica, Institute of Astronomy and Astrophysics, Taipei, Taiwan (China); Van der Tak, F. F. S., E-mail: beuther@mpia.d, E-mail: wouter@astro.uni-bonn.d, E-mail: rrao@sma.hawaii.ed, E-mail: vdtak@sron.n [SRON Netherlands Institute for Space Research, Landleven 12, 9747 AD Groningen (Netherlands)

    2010-11-20T23:59:59.000Z

    To characterize the magnetic field structure of the outflow and core region within a prototypical high-mass star-forming region, we analyzed polarized CO(3-2)-for the first time observed with the Submillimeter Array-as well as 880 {mu}m submillimeter continuum emission from the high-mass outflow/disk system IRAS 18089-1732. Both emission features with polarization degrees at a few percent level indicate that the magnetic field structure is largely aligned with the outflow/jet orientation from small core scales to larger outflow scales. Although quantitative estimates are crude, the analysis indicates that turbulent energy dominates over magnetic energy. The data also suggest a magnetic field strength increase from the lower-density envelope to the higher-density core.

  2. Exploring Ultrahigh Magnetic Field Processing of Materials for Developing Customized Microstructures and Enhanced Performance

    SciTech Connect (OSTI)

    Ludtka, GERALD M.

    2005-03-31T23:59:59.000Z

    Thermodynamic calculations based on Gibbs free energy in the magnetization-magnetic intensity-temperature (M-H-T) magnetic equation of state space demonstrate that significantly different phase equilibria may result for those material systems where the product and parent phases exhibit different magnetization responses. These calculations show that the Gibbs free energy is changed by a factor equal to -MdH, where M and H are the magnetization and applied field strength, respectively. Magnetic field processing is directly applicable to a multitude of alloys and compounds for dramatically influencing phase stability and phase transformations. This ability to selectively control microstructural stability and alter transformation kinetics through appropriate selection of the magnetic field strength promises to provide a very robust mechanism for developing and tailoring enhanced microstructures (and even nanostructures through accelerated kinetics) with superior properties for a broad spectrum of material applications. For this Industrial Materials for the Future (IMF) Advanced Materials for the Future project, ferrous alloys were studied initially since this alloy family exhibits ferromagnetism over part of its temperature range of stability and therefore would demonstrate the maximum impact of this novel processing mechanism. Additionally, with these ferrous alloys, the high-temperature parent phase, austenite, exhibits a significantly different magnetization response from the potential product phases, ferrite plus carbide or martensite; and therefore, the solid-state transformation behavior of these alloys will be dramatically influenced by the presence of ultrahigh magnetic fields. Finally, a thermodynamic calculation capability (within ThermoCalc for example) was developed during this project to enable parametric studies to be performed to predict the magnitude of the influence of magnetic processing variables on the phase stability (phase diagrams) in ferromagnetic materials of relevance to the Industries of the Future (IOF).

  3. The origin, evolution and signatures of primordial magnetic fields

    E-Print Network [OSTI]

    Subramanian, Kandaswamy

    2015-01-01T23:59:59.000Z

    The universe is magnetized on all scales probed so far. On the largest scales, galaxies and galaxy clusters host magnetic fields at the micro Gauss level coherent on scales up to ten kpc. Recent observational evidence suggests that even the intergalactic medium in voids could host a weak $\\sim 10^{-16}$ Gauss magnetic field, coherent on Mpc scales. An intriguing possibility is that these observed magnetic fields are a relic from the early universe, albeit one which has been subsequently amplified and maintained by a dynamo in collapsed objects. We review here the origin, evolution and signatures of primordial magnetic fields. After a brief summary of magnetohydrodynamics in the expanding universe, we turn to magnetic field generation during inflation and other phase transitions. We trace the linear and nonlinear evolution of the generated primordial fields through the radiation era, including viscous effects. Sensitive observational signatures of primordial magnetic fields on the cosmic microwave background, ...

  4. Graphene transparency in weak magnetic fields

    E-Print Network [OSTI]

    David Valenzuela; Saúl Hernández-Ortiz; Marcelo Loewe; Alfredo Raya

    2014-10-20T23:59:59.000Z

    We carry out an explicit calculation of the vacuum polarization tensor for an effective low-energy model of monolayer graphene in the presence of a weak magnetic field of intensity $B$ perpendicularly aligned to the membrane. By expanding the quasiparticle propagator in the Schwinger proper time representation up to order $(eB)^2$, where $e$ is the unit charge, we find an explicitly transverse tensor, consistent with gauge invariance. Furthermore, assuming that graphene is radiated with monochromatic light of frequency $\\omega$ along the external field direction, from the modified Maxwell's equations we derive the intensity of transmitted light and the angle of polarization rotation in terms of the longitudinal ($\\sigma_{xx}$) and transverse ($\\sigma_{xy}$) conductivities. Corrections to these quantities, both calculated and measured, are of order $(eB)^2/\\omega^4$. Our findings generalize and complement previously known results reported in literature regarding the light absorption problem in graphene from the experimental and theoretical points of view, with and without external magnetic fields.

  5. Rotating-frame gradient fields for magnetic resonance imaging and nuclear magnetic resonance in low fields

    DOE Patents [OSTI]

    Bouchard, Louis-Serge; Pines, Alexander; Demas, Vasiliki

    2014-01-21T23:59:59.000Z

    A system and method for Fourier encoding a nuclear magnetic resonance (NMR) signal is disclosed. A static magnetic field B.sub.0 is provided along a first direction. An NMR signal from the sample is Fourier encoded by applying a rotating-frame gradient field B.sub.G superimposed on the B.sub.0, where the B.sub.G comprises a vector component rotating in a plane perpendicular to the first direction at an angular frequency .omega.in a laboratory frame. The Fourier-encoded NMR signal is detected.

  6. Magnetic fields in relativistic collisionless shocks

    SciTech Connect (OSTI)

    Santana, Rodolfo; Kumar, Pawan [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Barniol Duran, Rodolfo, E-mail: santana@astro.as.utexas.edu, E-mail: pk@astro.as.utexas.edu, E-mail: rbarniol@phys.huji.ac.il [Racah Institute for Physics, The Hebrew University, Jerusalem 91904 (Israel)

    2014-04-10T23:59:59.000Z

    We present a systematic study on magnetic fields in gamma-ray burst (GRB) external forward shocks (FSs). There are 60 (35) GRBs in our X-ray (optical) sample, mostly from Swift. We use two methods to study ? {sub B} (fraction of energy in magnetic field in the FS): (1) for the X-ray sample, we use the constraint that the observed flux at the end of the steep decline is ? X-ray FS flux; (2) for the optical sample, we use the condition that the observed flux arises from the FS (optical sample light curves decline as ?t {sup –1}, as expected for the FS). Making a reasonable assumption on E (jet isotropic equivalent kinetic energy), we converted these conditions into an upper limit (measurement) on ? {sub B} n {sup 2/(p+1)} for our X-ray (optical) sample, where n is the circumburst density and p is the electron index. Taking n = 1 cm{sup –3}, the distribution of ? {sub B} measurements (upper limits) for our optical (X-ray) sample has a range of ?10{sup –8}-10{sup –3} (?10{sup –6}-10{sup –3}) and median of ?few × 10{sup –5} (?few × 10{sup –5}). To characterize how much amplification is needed, beyond shock compression of a seed magnetic field ?10 ?G, we expressed our results in terms of an amplification factor, AF, which is very weakly dependent on n (AF?n {sup 0.21}). The range of AF measurements (upper limits) for our optical (X-ray) sample is ?1-1000 (?10-300) with a median of ?50 (?50). These results suggest that some amplification, in addition to shock compression, is needed to explain the afterglow observations.

  7. Optical pumping magnetic resonance in high magnetic fields: Characterization of nuclear relaxation during pumping

    E-Print Network [OSTI]

    Augustine, Mathew P.

    Optical pumping magnetic resonance in high magnetic fields: Characterization of nuclear relaxation during pumping Matthew P. Augustine and Kurt W. Zilm Department of Chemistry, Yale University, New Haven exchange with optically pumped Rb vapor is investigated in high magnetic field. Operation in a high field

  8. A New Radio - X-Ray Probe of Galaxy Cluster Magnetic Fields

    E-Print Network [OSTI]

    T. E. Clarke; P. P. Kronberg; H. Boehringer

    2000-11-14T23:59:59.000Z

    Results are presented of a new VLA-ROSAT study that probes the magnetic field strength and distribution over a sample of 16 ``normal'' low redshift (z = 5-10 (l/10 kpc)^{-1/2} microGauss, where l is the field correlation length. These results lead to a global estimate of the total magnetic energy in clusters, and give new insight into the ultimate energy origin, which is likely gravitational. These results also shed some light on the cluster evolutionary conditions that existed at the onset of cooling flows.

  9. Goos-Hänchen like Shifts for Graphene Barrier in Constant Magnetic Field

    E-Print Network [OSTI]

    Ahmed Jellal; Miloud Mekkaoui; Youness Zahidi

    2014-04-22T23:59:59.000Z

    We consider a system of Dirac fermions in graphene submitted to a constant perpendicular magnetic field and scattered by a barrier potential. We show that our system can be used to establish a link with quantum optics through the Goos-H\\"{a}nchen shifts. This can be done by evaluating the corresponding transmission probability and shift phase. We obtain Goos-H\\"{a}nchen like shifts in terms of different physical parameters such as energy, electrostatic potential strength and magnetic field. On the light of this relation, we discuss the obtained results and make comparison with literature.

  10. Magnetic Fields and the Polarization of Astrophysical Maser Radiation: A Review

    E-Print Network [OSTI]

    William D. Watson

    2008-11-10T23:59:59.000Z

    Basic aspects of the relationship between the magnetic field and polarized maser radiation are described with the emphasis on interpreting the observed spectra. Special attention is given to three issues--the limitations on the applicability of the classic solutions of Goldreich, Keeley & Kwan (1973), inferring the strength of the magnetic field from the circular polarization when the Zeeman splitting is much less than the spectral linebreadth (especially for SiO masers), and the significance of the absence of components of the Zeeman triplet in the spectra of OH masers in regions of star formation.

  11. The onset of ion heating during magnetic reconnection with a strong guide field

    SciTech Connect (OSTI)

    Drake, J. F., E-mail: drake@umd.edu [Space Science Laboratory, University of California, Berkeley, California 94720 (United States); Swisdak, M., E-mail: swisdak@umd.edu [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States)

    2014-07-15T23:59:59.000Z

    The onset of the acceleration of ions during magnetic reconnection is explored via particle-in-cell simulations in the limit of a strong ambient guide field that self-consistently and simultaneously follow the motions of protons and ? particles. Heating parallel to the local magnetic field during reconnection with a guide field is strongly reduced compared with the reconnection of anti-parallel magnetic fields. The dominant heating of thermal ions during guide field reconnection results from pickup behavior of ions during their entry into reconnection exhausts and dominantly produces heating perpendicular rather than parallel to the local magnetic field. Pickup behavior requires that the ion transit time across the exhaust boundary (with a transverse scale of the order of the ion sound Larmor radius) be short compared with the ion cyclotron period. This translates into a threshold in the strength of reconnecting magnetic field that favors the heating of ions with high mass-to-charge. A simulation with a broad initial current layer produces a reconnecting system in which the amplitude of the reconnecting magnetic field just upstream of the dissipation region increases with time as reconnection proceeds. The sharp onset of perpendicular heating when the pickup threshold is crossed is documented. A comparison of the time variation of the parallel and perpendicular ion heating with that predicted based on the strength of the reconnecting field establishes the scaling of ion heating with ambient parameters both below and above the pickup threshold. The relevance to observations of ion heating in the solar corona is discussed.

  12. Large-scale magnetic field of the G8 dwarf xi Bootis A

    E-Print Network [OSTI]

    P. Petit; J. -F. Donati; M. Auriere; J. D. Landstreet; F. Lignieres; S. Marsden; D. Mouillet; F. Paletou; N. Toque; G. A. Wade

    2005-05-20T23:59:59.000Z

    We investigate the magnetic geometry of the active G8 dwarf xi Bootis A, from spectropolarimetric observations obtained in 2003 with the MuSiCoS echelle spectropolarimeter at the Telescope Bernard Lyot (Observatoire du Pic du Midi, France). We repeatedly detect a photospheric magnetic field, with periodic variations consistent with rotational modulation. Circularly polarized (Stokes V) line profiles present a systematic asymmetry, showing up as an excess in amplitude and area of the blue lobe of the profiles. A direct modeling of Stokes V profiles suggests that the global magnetic field is composed of two main components, with an inclined dipole and a large-scale toroidal field. We derive a dipole intensity of about 40 G, with an inclination of 35 degrees of the dipole with respect to the rotation axis. The toroidal field strength is of order of 120 G. A noticeable evolution of the field geometry is observed over the 40 nights of our observing window and results in an increase of the field strength and of the dipole inclination. This study is the first step of a long-term monitoring of xi Bootis A and other active solar-type stars, with the aim to investigate secular fluctuations of stellar magnetic geometries induced by activity cycles.

  13. Large-scale magnetic fields in the inflationary universe

    E-Print Network [OSTI]

    Kazuharu Bamba; Misao Sasaki

    2006-11-22T23:59:59.000Z

    The generation of large-scale magnetic fields is studied in inflationary cosmology. We consider the violation of the conformal invariance of the Maxwell field by dilatonic as well as non-minimal gravitational couplings. We derive a general formula for the spectrum of large-scale magnetic fields for a general form of the coupling term and the formula for the spectral index. The result tells us clearly the (necessary) condition for the generation of magnetic fields with sufficiently large amplitude.

  14. Magnetic fields in the nearby spiral galaxy IC 342: A multifrequency radio polarization study

    E-Print Network [OSTI]

    Beck, Rainer

    2015-01-01T23:59:59.000Z

    The total and polarized radio continuum emission of IC 342 was observed in four wavelength bands with the Effelsberg and VLA telescopes. The frequency-dependent radial scalelength of the diffuse radio synchrotron disk is indicative of propagation of cosmic-ray electrons via the streaming instability. The equipartition strength of the total magnetic field is typically 15 muG, that of the ordered field 5 muG. Faraday rotation reveals an underlying regular field of only about 0.5 muG strength with an axisymmetric spiral pattern, signature of a mean-field dynamo, and an about 10x stronger field that fluctuates on scales of a few 100 pc. The magnetic field around the bar in the central region of IC 342 resembles that of large barred galaxies; its regular spiral field is directed outwards, opposite to that in the disk. The polarized emission in the disk is concentrated in: (1) a narrow arm of about 300 pc width, displaced inwards with respect to the eastern arm by about 200 pc, indicating magnetic fields compressed...

  15. Magnetic Fields in Quasar Cores II

    E-Print Network [OSTI]

    G. B. Taylor

    1999-11-22T23:59:59.000Z

    Multi-frequency polarimetry with the Very Long Baseline Array (VLBA) telescope has revealed absolute Faraday Rotation Measures (RMs) in excess of 1000 rad/m/m in the central regions of 7 out of 8 strong quasars studied (e.g., 3C 273, 3C 279, 3C 395). Beyond a projected distance of ~20 pc, however, the jets are found to have |RM| < 100 rad/m/m. Such sharp RM gradients cannot be produced by cluster or galactic-scale magnetic fields, but rather must be the result of magnetic fields organized over the central 1-100 pc. The RMs of the sources studied to date and the polarization properties of BL Lacs, quasars and galaxies are shown to be consistent so far with the predictions of unified schemes. The direct detection of high RMs in these quasar cores can explain the low fractional core polarizations usually observed in quasars at centimeter wavelengths as the result of irregularities in the Faraday screen on scales smaller than the telescope beam. Variability in the RM of the core is reported for 3C 279 between observations taken 1.5 years apart, indicating that the Faraday screen changes on that timescale, or that the projected superluminal motion of the inner jet components samples a new location in the screen with time. Either way, these changes in the Faraday screen may explain the dramatic variability in core polarization properties displayed by quasars.

  16. Improving magnet designs with high and low field regions

    E-Print Network [OSTI]

    Bjørk, R; Smith, A; Pryds, N

    2014-01-01T23:59:59.000Z

    A general scheme for increasing the difference in magnetic flux density between a high and a low magnetic field region by removing unnecessary magnet material is presented. This is important in, e.g., magnetic refrigeration where magnet arrays has to deliver high field regions in close proximity to low field regions. Also, a general way to replace magnet material with a high permeability soft magnetic material where appropriate is discussed. As an example these schemes are applied to a two dimensional concentric Halbach cylinder design resulting in a reduction of the amount of magnet material used by 42% while increasing the difference in flux density between a high and a low field region by 45%.

  17. On the Influence of Weak Magnetic and Electric Fields on the Fluctuations of Ionic Electric Currents in Blood Circulation

    E-Print Network [OSTI]

    Zakirjon Kanokov; Juern W. P. Schmelzer; Avazbek K. Nasirov

    2009-04-07T23:59:59.000Z

    An analysis of a variety of existing experimental data leads to the conclusion on the existence of a resonance mechanism allowing weak magnetic fields to affect biological processes. These fields may either be static magnetic fields comparable in magnitude with the magnetic field of the earth or weak ultra-low frequency time-dependent fields. So far, a generally accepted theoretical model allowing one to understand the effect of magnetic and electric fields on biological processes is not available. By this reason, it is not clear which characteristics of the fields, like magnetic and electric field strength, frequency of change of the field, shape of the electromagnetic wave, the duration of the magnetic or electric influence or some particular combination of them, are responsible for the biological effect. In the present analysis it is shown that external time-independent magnetic fields may cause a resonance amplification of ionic electric currents in biological tissues and, in particular, in the vasculature system due to a Brownian motion of charges. These resonance electric currents may cause necrotic changes in the tissues or blood circulation and in this way significantly affect the biological organism. The magnitude of the magnetic fields leading to resonance effects is estimated, it is shown that it depends significantly on the radius of the blood capillaries.

  18. Neutron scattering in magnetic fields (*) W. C. Koehler

    E-Print Network [OSTI]

    Boyer, Edmond

    691 Neutron scattering in magnetic fields (*) W. C. Koehler Solid State Division, Oak Ridge. Abstract 2014 The use of magnetic fields in neutron scattering experimentation is reviewed briefly. Two of the scattering sample ; in the second the field acts on the neutron itself. Several examples are discussed

  19. Magnetic Propulsion of Intense Lithium Streams in a Tokamak Magnetic Field

    E-Print Network [OSTI]

    Zakharov, Leonid E.

    Magnetic Propulsion of Intense Lithium Streams in a Tokamak Magnetic Field Leonid E. Zakharov the theory of magnetic propulsion of liquid lithium streams and their stability in tokamaks takes into account the propulsion e#11;ect, viscosity and the drag force due to magnetic pumping

  20. Baryon magnetic moments in the background field method

    E-Print Network [OSTI]

    Lee, F X; Zhou, L; Wilcox, W

    2005-01-01T23:59:59.000Z

    We present a calculation of the magnetic moments for the baryon octet and decuplet using the background-field method and standard Wilson gauge and fermion actions in the quenched approximation of lattice QCD. Progressively smaller static magnetic fields are introduced on a $24^4$ lattice at beta=6.0 and the pion mass is probed down to about 500 MeV. Magnetic moments are extracted from the linear response of the masses to the background field.

  1. Baryon magnetic moments in the external field method

    E-Print Network [OSTI]

    Lee, F X; Zhou, L; Wilcox, W

    2005-01-01T23:59:59.000Z

    We present a calculation of the magnetic moments of the baryon octet and decuplet using the external field method and standard Wilson gauge and fermion actions in the quenched approximation. Progressively smaller static magnetic fields are introduced on a $24^4$ latticeat beta=6.0 and the pion mass is probed down to about 500 MeV. Magnetic moments are extracted from the linear response of the masses to the external field.

  2. Temperature compensated current sensor using reference magnetic field

    DOE Patents [OSTI]

    Yakymyshyn, Christopher Paul (Seminole, FL); Brubaker, Michael Allen (Loveland, CO); Yakymyshyn, Pamela Jane (Seminole, FL)

    2007-10-09T23:59:59.000Z

    A method is described to provide temperature compensation and self-calibration of a current sensor based on a plurality of magnetic field sensors positioned around a current carrying conductor. A reference magnetic field generated within the current sensor housing is detected by a separate but identical magnetic field sensor and is used to correct variations in the output signal due to temperature variations and aging.

  3. The Stückelberg Holographic Superconductors in Constant External Magnetic Field

    E-Print Network [OSTI]

    Jian-Pin Wu

    2010-07-08T23:59:59.000Z

    We investigate the St\\"{u}ckelberg holographic superconductor in present of the constant external magnetic field. We observe that a critical value of magnetic field exists as the cases in usual holographic superconductor. Furthermore, we find that the applied magnetic field strongly influence the phase transition of this model and have a jump in the condensate at the critical temperature even for $c_{4}=1$.

  4. A simple method for characterization of the magnetic field in an ion trap using Be+ ions

    E-Print Network [OSTI]

    Jianwei Shen; Andrii Borodin; Stephan Schiller

    2014-10-06T23:59:59.000Z

    We demonstrate a simple method for the determination of the magnetic field in an ion trap using laser-cooled Be+ ions. The method is not based on magnetic resonance and thus does not require delivering radiofrequency (RF) radiation to the trap. Instead, stimulated Raman spectroscopy is used, and only an easily generated optical sideband of the laser cooling wave is required. The d.c. magnetic vector, averaged over the Be+ ion ensemble, is determined. Furthermore, the field strength can be minimized and an upper limit for the field gradient can be determined. The resolution of the method is 0.04 G at present. The relevance for precision rovibrational spectroscopy of molecular hydrogen ions is briefly discussed.

  5. VLBA Observations of G5.89-0.39: OH masers and magnetic field structure

    E-Print Network [OSTI]

    D. P. Stark; W. M. Goss; E. Churchwell; V. L. Fish; I. M. Hoffman

    2006-10-05T23:59:59.000Z

    We present VLBA observations of 1667 MHz OH maser emission from the massive star formation region G5.89-0.39. The observations were phase referenced allowing the absolute positions of the masers to be obtained. The 1667 MHz masers have radial velocities that span ~50 km/s but show little evidence of tracing the bipolar molecular outflow, as has been claimed in previous studies. We identify 23 Zeeman pairs through comparison of masers in left and right circular polarization. Magnetic field strengths range from -2 mG to +2 mG, and an ordered reversal in magnetic field direction is observed toward the southern region of the UC HII region. We suggest that the velocity and magnetic field structure of the 1667 MHz masers can be explained in the context of a model in which the masers arise in a neutral shell just outside a rapidly exanding ionized shell.

  6. Static magnetic field concentration and enhancement using magnetic materials with positive permeability

    E-Print Network [OSTI]

    Sun, F

    2013-01-01T23:59:59.000Z

    In this paper a novel compressor for static magnetic fields is proposed based on finite embedded transformation optics. When the DC magnetic field passes through the designed device, the magnetic field can be compressed inside the device. After it passes through the device, one can obtain an enhanced static magnetic field behind the output surface of the device (in a free space region). We can also combine our compressor with some other structures to get a higher static magnetic field enhancement in a free space region. In contrast with other devices based on transformation optics for enhancing static magnetic fields, our device is not a closed structure and thus has some special applications (e.g., for controlling magnetic nano-particles for gene and drag delivery). The designed compressor can be constructed by using currently available materials or DC meta-materials with positive permeability. Numerical simulation verifies good performance of our device.

  7. Electrostatic and Magnetic Fields in Bilayer Graphene

    E-Print Network [OSTI]

    Ahmed Jellal; Ilham Redouani; Hocine Bahlouli

    2014-11-14T23:59:59.000Z

    We compute the transmission probability through rectangular potential barriers and p-n junctions in the presence of a magnetic and electric fields in bilayer graphene taking into account the full four bands of the energy spectrum. For energy E higher than the interlayer coupling $\\gamma_1 (E>\\gamma_1)$ two propagation modes are available for transport giving rise to four possible ways for transmission and reflection probabilities. However, when the energy is less then the height of the barrier the Dirac fermions exhibits transmission resonances and only one mode of propagation is available. We study the effect of the interlayer electrostatic potential $\\delta$ and the different geometry parameters of the barrier on the transmission probability.

  8. Microstructural Modification of a Cast Iron by Magnetic Field Processing

    SciTech Connect (OSTI)

    Kenik, Edward A [ORNL; Ludtka, Gail Mackiewicz- [ORNL; Ludtka, Gerard Michael [ORNL; Wilgen, John B [ORNL; Kisner, Roger A [ORNL

    2010-01-01T23:59:59.000Z

    The current study deals with the microstructural modification of a nodular cast iron during solidification under the influence of high magnetic fields (up to 18 tesla).

  9. Heat pulse propagation in chaotic three-dimensional magnetic fields

    SciTech Connect (OSTI)

    Del-Castillo-Negrete, Diego [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Blazevski, Daniel [Institute for Mechanical Systems, ETH, Zurich (Switzerland)

    2014-06-01T23:59:59.000Z

    Heat pulse propagation in three-dimensional chaotic magnetic fields is studied by numerically solving the parallel heat transport equation using a Lagrangian Green's function (LG) method. The main two problems addressed are: the dependence of the radial transport of heat pulses on the level of magnetic field stochasticity (controlled by the amplitude of the magnetic field perturbation, ?), and the role of reversed shear magnetic field configurations on heat pulse propagation. The role of separatrix reconnection of resonant modes in the shear reversal region, and the role of shearless Cantori in the observed phenomena are also discussed.

  10. Coulomb law and energy levels in a superstrong magnetic field

    E-Print Network [OSTI]

    Vysotsky, M I

    2012-01-01T23:59:59.000Z

    Analytical expression for the Coulomb potential in the presence of superstrong magnetic field is derived. Structure of hydrogen levels originating from LLL is analyzed.

  11. Entanglement of two-qubit photon beam by magnetic field

    E-Print Network [OSTI]

    A. D. Levin; D. M. Gitman; R. C. Castro

    2014-09-05T23:59:59.000Z

    We have studied the possibility of affecting the entanglement measure of 2-qubit system consisting of two photons with different fixed frequencies but with two arbitrary linear polarizations, moving in the same direction, by the help of an applied external magnetic field. The interaction between the magnetic field and the photons in our model is achieved through intermediate electrons that interact with both the photons and the magnetic field. The possibility of exact theoretical analysis of this scheme is based on known exact solutions that describe the interaction of an electron subjected to an external magnetic field (or a medium of electrons not interacting with each other) with a quantized field of two photons. We adapt these exact solutions to the case under consideration. Using explicit wave functions for the resulting electromagnetic field, we calculate the entanglement measure of the photon beam as a function of the applied magnetic field and parameters of the electron medium.

  12. Development and applications of NMR (nuclear magnetic resonance) in low fields and zero field

    SciTech Connect (OSTI)

    Bielecki, A.

    1987-05-01T23:59:59.000Z

    This dissertation is about nuclear magnetic resonance (NMR) spectroscopy in the absence of applied magnetic fields. NMR is usually done in large magnetic fields, often as large as can be practically attained. The motivation for going the opposite way, toward zero field, is that for certain types of materials, particularly powdered or polycrystalline solids, the NMR spectra in zero field are easier to interpret than those obtained in high field. 92 refs., 60 figs., 1 tab.

  13. Bounds on QCD axion mass and primordial magnetic field from CMB $?$-distortion

    E-Print Network [OSTI]

    Damian Ejlli

    2014-11-19T23:59:59.000Z

    The oscillation of the CMB photons into axions can cause CMB spectral distortion in the presence of large scale magnetic field. With the COBE limit on the $\\mu$ parameter and a homogeneous magnetic field with strength $B\\lesssim 3.2$ nG at the horizon scale, stronger lower limit on the axion mass in comparison with the limit of the ADMX experiment is found to be, $4.8\\times 10^{-5}$ eV $\\lesssim m_a$ for the KSVZ axion model. On the other hand, using the experimental limit on the axion mass $3.5\\times 10^{-6}$ eV $\\lesssim m_a$ from the ADMX experiment together with the COBE bound on $\\mu$, is found $B\\lesssim 53$ nG for the KSVZ axion model and $B\\lesssim 141$ nG for DFSZ axion model, for a homogeneous magnetic field with coherence length at the present epoch $\\lambda_B\\sim 1.3$ Mpc. Limits on $B$ and $m_a$ for PIXIE/PRISM expected sensitivity on $\\mu$ are derived. If CMB $\\mu$ distortion would be detected by the future space missions PIXIE/PRISM and assuming that the strength of the large scale magnetic field is close to its canonical value, $B\\sim 1-3$ nG, axions in the mass range $2\\, \\mu$eV - $3\\, \\mu$eV would be potential candidates of CMB $\\mu$-distortion.

  14. Observation of low magnetic field density peaks in helicon plasma

    SciTech Connect (OSTI)

    Barada, Kshitish K.; Chattopadhyay, P. K.; Ghosh, J.; Kumar, Sunil; Saxena, Y. C. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)

    2013-04-15T23:59:59.000Z

    Single density peak has been commonly observed in low magnetic field (<100 G) helicon discharges. In this paper, we report the observations of multiple density peaks in low magnetic field (<100 G) helicon discharges produced in the linear helicon plasma device [Barada et al., Rev. Sci. Instrum. 83, 063501 (2012)]. Experiments are carried out using argon gas with m = +1 right helical antenna operating at 13.56 MHz by varying the magnetic field from 0 G to 100 G. The plasma density varies with varying the magnetic field at constant input power and gas pressure and reaches to its peak value at a magnetic field value of {approx}25 G. Another peak of smaller magnitude in density has been observed near 50 G. Measurement of amplitude and phase of the axial component of the wave using magnetic probes for two magnetic field values corresponding to the observed density peaks indicated the existence of radial modes. Measured parallel wave number together with the estimated perpendicular wave number suggests oblique mode propagation of helicon waves along the resonance cone boundary for these magnetic field values. Further, the observations of larger floating potential fluctuations measured with Langmuir probes at those magnetic field values indicate that near resonance cone boundary; these electrostatic fluctuations take energy from helicon wave and dump power to the plasma causing density peaks.

  15. Measuring and shimming the magnetic field of a 4 Tesla MRI magnet

    E-Print Network [OSTI]

    Kyriazis, Georgios

    1993-01-01T23:59:59.000Z

    The Biomedical Magnetic Resonance Laboratory (BMRL) of the University of Illinois at Urbana-Champaign (UIUC) has ordered from the Texas Accelerator Center (TAC) a superconducting, self-shielded, solenoidal magnet with a maximum field of 4 Tesla...

  16. Magnetic field-induced phase transformation & power harvesting capabilities in magnetic shape memory alloys

    E-Print Network [OSTI]

    Basaran, Burak

    2011-02-22T23:59:59.000Z

    Magnetic Shape Memory Alloys (MSMAs) combine shape-change/deformationrecovery abilities of heat driven conventional shape memory alloys (SMA) and magnetic field driven magnetostrictives through martensitic transformation. They are promising...

  17. Understanding magnetic field reversal mechanisms in mesoscopic magnetic multilayer ring structures

    E-Print Network [OSTI]

    Ng, Bryan

    2008-01-01T23:59:59.000Z

    Patterned pseudo spin-valve rings show great promise for device applications due to their non-volatility and variety of stable magnetic states. However, the magnetic reversal of these elements under an applied field is ...

  18. Nuclear magnetic absorption line widths in weak magnetic fields with a Robinson oscillator

    E-Print Network [OSTI]

    Flugum, Timothy Lee

    1987-01-01T23:59:59.000Z

    NUCLEAR MAGNETIC ABSORPTION LINE WIDTHS IN WEAK MAGNETIC FIELDS WITH A ROBINSON OSCILLATOR A Thesis by TIMOTHY LEE FLUGUM Subnntted to the Graduate College of Texas ARM University in partial fulfillment of the requirement for the degree... of MASTER OF SCIENCE August 19SI Major Subject: Physics NUCLEAR MAGNETIC ABSORPTION LINE WIDTHS IN WEAK MAGNETIC FIELDS WITH A ROBINSON OSCILLATOR A Thesis TIMOTHY LEE FLUGUM Approved as to style and content by: Nelson M. Duller (Chairman...

  19. Development of magnetic separation methods of analysis: magnetic field flow fractionation

    E-Print Network [OSTI]

    Garcia-Ramirez, Jaime

    1980-01-01T23:59:59.000Z

    DEVELOPMENT OF MAGNETIC SEPARATION METHODS OF ANALYSIS: MAGNETIC FIELD FLOW FRACTIONATION A Thesis by JAIME GARCIA-RAMIREZ Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree... of MASTER OF SCIENCE August 1980 Major Subject: Chemistry DEVELOPMENT OF MAGNETIC SEPARATION METHODS OF ANALYSIS: MAGNETIC FIELD FLOW FRACTIONATION A Thesis by JAIME GARCIA-RAMIREZ Approved as to style and content by: (Chairman of Committee) 1...

  20. Including stereoscopic information in the reconstruction of coronal magnetic fields

    E-Print Network [OSTI]

    T. Wiegelmann; T. Neukirch

    2008-01-23T23:59:59.000Z

    We present a method to include stereoscopic information about the three dimensional structure of flux tubes into the reconstruction of the coronal magnetic field. Due to the low plasma beta in the corona we can assume a force free magnetic field, with the current density parallel to the magnetic field lines. Here we use linear force free fields for simplicity. The method uses the line of sight magnetic field on the photosphere as observational input. The value of $\\alpha$ is determined iteratively by comparing the reconstructed magnetic field with the observed structures. The final configuration is the optimal linear force solution constrained by both the photospheric magnetogram and the observed plasma structures. As an example we apply our method to SOHO MDI/EIT data of an active region. In the future it is planned to apply the method to analyse data from the SECCHI instrument aboard the STEREO mission.

  1. Magnetic-field-induced antiferromagnetism in the Kondo lattice

    E-Print Network [OSTI]

    Beach, Kevin S. D. (Kevin Stuart David), 1975-

    2004-01-01T23:59:59.000Z

    The half-filled Kondo lattice model, augmented by a Zeeman term, serves as a useful model of a Kondo insulator in an applied magnetic field. A variational mean field analysis of this system on a square lattice, backed up ...

  2. Field quality measurements of a 2-Tesla transmission line magnet

    SciTech Connect (OSTI)

    Velev, G.V.; Foster, W.; Kashikhin, V.; Mazur, P.; Oleck, A.; Piekarz, H.; Schlabach, P.; Sylvester, C.; /Fermilab; Wake, M.; /KEK, Tsukuba

    2005-09-01T23:59:59.000Z

    A prototype 2-Tesla superconducting transmission line magnet for future hadron colliders was designed, built and tested at Fermilab. The 1.5 m long, combined-function gradient-dipole magnet has a vertical pole aperture of 20 mm. To measure the magnetic field quality in such a small magnet aperture, a specialized rotating coil of 15.2 mm diameter, 0.69 m long was fabricated. Using this probe, a program of magnetic field quality measurements was successfully performed. Results of the measurements are presented and discussed.

  3. Comparison of transient horizontal magnetic fields in a plage region and in the quiet Sun

    E-Print Network [OSTI]

    Ryohko Ishikawa; Saku Tsuneta

    2008-12-09T23:59:59.000Z

    Properties of transient horizontal magnetic fields (THMFs) in both plage and quiet Sun regions are obtained and compared. Spectro-polarimetric observations with the Solar Optical Telescope (SOT) on the Hinode satellite were carried out with a cadence of about 30 seconds for both plage and quiet regions located near disk center. We select THMFs that have net linear polarization (LP) higher than 0.22%, and an area larger than or equal to 3 pixels, and compare their occurrence rates and distribution of magnetic field azimuth. We obtain probability density functions (PDFs) of magnetic field strength and inclination for both regions.The occurrence rate in the plage region is the same as for the quiet Sun. The vertical magnetic flux in the plage region is ~8 times larger than in the quiet Sun. There is essentially no preferred orientation for the THMFs in either region. However, THMFs in the plage region with higher LP have a preferred direction consistent with that of the plage-region's large-scale vertical field pattern. PDFs show that there is no difference in the distribution of field strength of horizontal fields between the quiet Sun and the plage regions when we avoid the persistent large vertical flux concentrations for the plage region. The similarity of the PDFs and of the occurrence rates in plage and quiet regions suggests that a local dynamo process due to the granular motion may generate THMFs all over the sun. The preferred orientation for higher LP in the plage indicates that the THMFs are somewhat influenced by the larger-scale magnetic field pattern of the plage.

  4. Earth's Magnetic Field Measurements for the LCLS Undulators

    SciTech Connect (OSTI)

    Hacker, Kirsten

    2010-12-13T23:59:59.000Z

    Measurements of the earth's magnetic field at several locations at SLAC were conducted to determine the possible field error contribution from tuning the undulators in a location with a different magnetic field than that which will be found in the undulator hall. An average difference of 0.08 {+-} 0.04 Gauss has been measured between the downward earth's field components in the test facility and SLAC tunnel locations.

  5. Sidewall containment of liquid metal with vertical alternating magnetic fields

    DOE Patents [OSTI]

    Lari, Robert J. (Aurora, IL); Praeg, Walter F. (Palos Park, IL); Turner, Larry R. (Naperville, IL); Battles, James E. (Oak Forest, IL); Hull, John R. (Hinsdale, IL); Rote, Donald M. (Lagrange, IL)

    1990-01-01T23:59:59.000Z

    An apparatus for containing molten metal using a magnet producing vertical alternating magnetic field positioned adjacent the area in which the molten metal is to be confined. This invention can be adapted particularly to the casting of metal between counter-rotating rollers with the vertical alternating magnetic field used to confine the molten metal at the edges of the rollers. Alternately, the vertical alternating magnetic field can be used as a flow regulator in casting molten metal from an opening in a channel.

  6. Dynamical Electron Mass in a Strong Magnetic Field

    E-Print Network [OSTI]

    S. -Y. Wang

    2008-01-28T23:59:59.000Z

    Motivated by recent interest in understanding properties of strongly magnetized matter, we study the dynamical electron mass generated through approximate chiral symmetry breaking in QED in a strong magnetic field. We reliably calculate the dynamical electron mass by numerically solving the nonperturbative Schwinger-Dyson equations in a consistent truncation within the lowest Landau level approximation. It is shown that the generation of dynamical electron mass in a strong magnetic field is significantly enhanced by the perturbative electron mass that explicitly breaks chiral symmetry in the absence of a magnetic field.

  7. Submillimeter Polarimetry and the Galactic Center Magnetic Field

    E-Print Network [OSTI]

    Novak, Giles

    Submillimeter Polarimetry and the Galactic Center Magnetic Field D.T. Chuss NASA Goddard Space Flight Center C.D. Dowell Jet Propulsion Laboratory R.H. Hildebrand University of Chicago G. Novak that of the magnetic field. In addition, we present new Hertz data on the Dust Ridge, an arched structure

  8. Magnetic field modulated dust streams from Jupiter in Interplanetary space

    E-Print Network [OSTI]

    Hamilton, Douglas P.

    Magnetic field modulated dust streams from Jupiter in Interplanetary space Alberto Flandes Ciencias´es-Galicia Ciencias Espaciales, Instituto de Geof´isica, UNAM, M´exico. Linda Spilker Jet Propulsion Laboratory is sufficient to allow the planet's magnetic field to accelerate them away from the planet where

  9. Complementary bowtie aperture for localizing and enhancing optical magnetic field

    E-Print Network [OSTI]

    Xu, Xianfan

    Complementary bowtie aperture for localizing and enhancing optical magnetic field Nan Zhou, Edward, 2011 Nanoscale bowtie antenna and bowtie aperture antenna have been shown to generate strongly enhanced. In this Letter, we discuss the enhancement of magnetic field intensity of nanoscale complementary bowtie aperture

  10. Use of High Magnetic Fields to Improve Material Properties for Hydraulics, Automotive and Truck Components

    SciTech Connect (OSTI)

    Ludtka, Gerard Michael [ORNL; Ludtka, Gail Mackiewicz- [ORNL; Wilgen, John B [ORNL; Kisner, Roger A [ORNL; Ahmad, Aquil [Eaton Corporation

    2010-08-01T23:59:59.000Z

    In this CRADA, research and development activities were successfully conducted on magnetic processing effects for the purpose of manipulating microstructure and the application specific performance of three alloys provided by Eaton (alloys provided were: carburized steel, plain low carbon steel and medium carbon spring steel). Three specific industrial/commercial application areas were considered where HMFP can be used to provide significant energy savings and improve materials performance include using HMFP to: 1.) Produce higher material strengths enabling higher torque bearing capability for drive shafts and other motor components; 2.) Increase the magnetic response in an iron-based material, thereby improving its magnetic permeability resulting in improved magnetic coupling and power density, and 3.) Improve wear resistance. The very promising results achieved in this endeavor include: 1.) a significant increase in tensile strength and a major reduction in volume percent retained austenite for the carburized alloy, and 2.) a substantial improvement in magnetic perm respect to a no-field processed sample (which also represents a significant improvement over the nominal conventional automotive condition of no heat treatment). The successful completion of these activities has resulted in the current 3-year CRADA No. NFE-09-02522 Prototyping Energy Efficient ThermoMagnetic and Induction Hardening for Heat Treat and Net Shape Forming Applications .

  11. Plasma-satellite interaction driven magnetic field perturbations

    SciTech Connect (OSTI)

    Saeed-ur-Rehman, E-mail: surehman@ualberta.ca [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada); Theoretical Physics Division, PINSTECH, Nilore Islamabad 44000 (Pakistan); Marchand, Richard, E-mail: Richard.Marchand@ualberta.ca [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada)

    2014-09-15T23:59:59.000Z

    We report the first fully kinetic quantitative estimate of magnetic field perturbations caused by the interaction of a spacecraft with space environment. Such perturbations could affect measurements of geophysical magnetic fields made with very sensitive magnetometers on-board satellites. Our approach is illustrated with a calculation of perturbed magnetic fields near the recently launched Swarm satellites. In this case, magnetic field perturbations do not exceed 20 pT, and they are below the sensitivity threshold of the on-board magnetometers. Anticipating future missions in which satellites and instruments would be subject to more intense solar UV radiation, however, it appears that magnetic field perturbations associated with satellite interaction with space environment, might approach or exceed instruments' sensitivity thresholds.

  12. Exchange and correlation energies of ground states of atoms and molecules in strong magnetic fields

    E-Print Network [OSTI]

    Schmelcher, P; Becken, W

    1999-01-01T23:59:59.000Z

    Using a Hartree-Fock mesh method and a configuration interaction approach based on a generalized Gaussian basis set we investigate the behaviour of the exchange and correlation energies of small atoms and molecules, namely th e helium and lithium atom as well as the hydrogen molecule, in the presence of a magnetic field covering the regime B=0-100a.u. In general the importance of the exchange energy to the binding properties of at oms or molecules increases strongly with increasing field strength. This is due to the spin-flip transitions and in particular due to the contributions of the tightly bound hydrogenic state s which are involved in the corresponding ground states of different symmetries. In contrast to the exchange energy the correlation energy becomes less relevant with increasing field strength. This holds for the individual configurations constituting the ground state and for the crossovers of the global ground state.

  13. Plasma expansion in the presence of a dipole magnetic field

    SciTech Connect (OSTI)

    Winske, D.; Omidi, N. [Applied Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); SciberNet, Inc., Solana Beach, California 92075 (United States)

    2005-07-15T23:59:59.000Z

    Simulations of the initial expansion of a plasma injected into a stationary magnetized background plasma in the presence of a dipole magnetic field are carried out in two dimensions with a kinetic ion, massless fluid electron (hybrid) electromagnetic code. For small values of the magnetic dipole, the injected ions have large gyroradii compared to the scale length of the dipole field and are essentially unmagnetized. As a result, these ions expand, excluding the ambient magnetic field and plasma to form a diamagnetic cavity. However, for stronger magnetic dipoles, the ratio of the gyroradii of the injected ions to the dipole field scale length is small so that they remain magnetized, and hence trapped in the dipole field, as they expand. The trapping and expansion then lead to additional plasma currents and resulting magnetic fields that not only exclude the background field but also interact with the dipole field in a more complex manner that stretches the closed dipole field lines. A criterion to distinguish between the two regimes is derived and is then briefly discussed in the context of applying the results to the plasma sail scheme for the propulsion of small spacecraft in the solar wind.

  14. Faraday rotation: effect of magnetic field reversals

    E-Print Network [OSTI]

    Melrose, D B

    2010-01-01T23:59:59.000Z

    The standard formula for the rotation measure, RM, which determines the position angle, $\\psi={\\rm RM}\\lambda^2$, due to Faraday rotation, includes contributions only from the portions of the ray path where the natural modes of the plasma are circularly polarized. In small regions of the ray path where the projection of the magnetic field on the ray path reverses sign (called QT regions) the modes are nearly linearly polarized. The neglect of QT regions in estimating RM is not well justified at frequencies below a transition frequency where mode coupling changes from strong to weak. By integrating the polarization transfer equation across a QT region in the latter limit, I estimate the additional contribution $\\Delta\\psi$ needed to correct this omission. In contrast with a result proposed by \\cite{BB10}, $\\Delta\\psi$ is small and probably unobservable. I identify a new source of circular polarization, due to mode coupling in an asymmetric QT region. I also identify a new circular-polarization-dependent correc...

  15. FARADAY ROTATION: EFFECT OF MAGNETIC FIELD REVERSALS

    SciTech Connect (OSTI)

    Melrose, D. B. [SIfA, School of Physics, University of Sydney, NSW 2006 (Australia)

    2010-12-20T23:59:59.000Z

    The standard formula for the rotation measure (RM), which determines the position angle, {psi} = RM{lambda}{sup 2}, due to Faraday rotation, includes contributions only from the portions of the ray path where the natural modes of the plasma are circularly polarized. In small regions of the ray path where the projection of the magnetic field on the ray path reverses sign (called QT regions) the modes are nearly linearly polarized. The neglect of QT regions in estimating RM is not well justified at frequencies below a transition frequency where mode coupling changes from strong to weak. By integrating the polarization transfer equation across a QT region in the latter limit, I estimate the additional contribution {Delta}{psi} needed to correct this omission. In contrast with a result proposed by Broderick and Blandford, {Delta}{psi} is small and probably unobservable. I identify a new source of circular polarization, due to mode coupling in an asymmetric QT region. I also identify a new circular-polarization-dependent correction to the dispersion measure at low frequencies.

  16. Cosmic Acceleration and Anisotropic models with Magnetic field

    E-Print Network [OSTI]

    S. K. Tripathy; K. L. Mahanta

    2014-12-10T23:59:59.000Z

    Plane symmetric cosmological models are investigated with or without any dark energy components in the field equations. Keeping an eye on the recent observational constraints concerning the accelerating phase of expansion of the universe, the role of magnetic field is assessed. In the absence of dark energy components, magnetic field can favour an accelerating model even if we take a linear relationship between the directional Hubble parameters. In presence of dark energy components in the form of a time varying cosmological constant, the influence of magnetic field is found to be limited.

  17. Magnetic-field sensing coil embedded in ceramic for measuring ambient magnetic field

    DOE Patents [OSTI]

    Takahashi, Hironori

    2004-02-10T23:59:59.000Z

    A magnetic pick-up coil for measuring magnetic field with high specific sensitivity, optionally with an electrostatic shield (24), having coupling elements (22) with high winding packing ratio, oriented in multiple directions, and embedded in ceramic material for structural support and electrical insulation. Elements of the coil are constructed from green ceramic sheets (200) and metallic ink deposited on surfaces and in via holes of the ceramic sheets. The ceramic sheets and the metallic ink are co-fired to create a monolithic hard ceramic body (20) with metallized traces embedded in, and placed on exterior surfaces of, the hard ceramic body. The compact and rugged coil can be used in a variety of environments, including hostile conditions involving ultra-high vacuum, high temperatures, nuclear and optical radiation, chemical reactions, and physically demanding surroundings, occurring either individually or in combinations.

  18. Magnetic fields, spots and weather in chemically peculiar stars

    E-Print Network [OSTI]

    O. Kochukhov

    2007-11-30T23:59:59.000Z

    New observational techniques and sophisticated modelling methods has led to dramatic breakthroughs in our understanding of the interplay between the surface magnetism, atomic diffusion and atmospheric dynamics in chemically peculiar stars. Magnetic Doppler images, constructed using spectropolarimetric observations of Ap stars in all four Stokes parameters, reveal the presence of small-scale field topologies. Abundance Doppler mapping has been perfected to the level where distributions of many different chemical elements can be deduced self-consistently for one star. The inferred chemical spot structures are diverse and do not always trace underlying magnetic field geometry. Moreover, horizontal chemical inhomogeneities are discovered in non-magnetic CP stars and evolving chemical spots are observed for the first time in the bright mercury-manganese star alpha And. These results show that in addition to magnetic fields, another important non-magnetic structure formation mechanism acts in CP stars.

  19. Observation of Dirac Monopoles in a Synthetic Magnetic Field

    E-Print Network [OSTI]

    Ray, M W; Kandel, S; Möttönen, M; Hall, D S

    2014-01-01T23:59:59.000Z

    Magnetic monopoles --- particles that behave as isolated north or south magnetic poles --- have been the subject of speculation since the first detailed observations of magnetism several hundred years ago. Numerous theoretical investigations and hitherto unsuccessful experimental searches have followed Dirac's 1931 development of a theory of monopoles consistent with both quantum mechanics and the gauge invariance of the electromagnetic field. The existence of even a single Dirac magnetic monopole would have far-reaching physical consequences, most famously explaining the quantization of electric charge. Although analogues of magnetic monopoles have been found in exotic spin-ices and other systems, there has been no direct experimental observation of Dirac monopoles within a medium described by a quantum field, such as superfluid helium-3. Here we demonstrate the controlled creation of Dirac monopoles in the synthetic magnetic field produced by a spinor Bose-Einstein condensate. Monopoles are identified, in b...

  20. Spectropolarimetric diagnostics of unresolved magnetic fields in the quiet solar photosphere

    E-Print Network [OSTI]

    Shchukina, Nataliya

    2012-01-01T23:59:59.000Z

    A few years before the Hinode space telescope was launched, an investigation based on the Hanle effect in atomic and molecular lines indicated that the bulk of the quiet solar photosphere is significantly magnetized, due to the ubiquitous presence of an unresolved magnetic field with an average strength = 130 G. It was pointed out also that this "hidden" field must be much stronger in the intergranular regions of solar surface convection than in the granular regions, and it was suggested that this unresolved magnetic field could perhaps provide the clue for understanding how the outer solar atmosphere is energized. In fact, the ensuing magnetic energy density is so significant that the energy flux estimated using the typical value of 1 km/s for the convective velocity (thinking in rising magnetic loops) or the Alfven speed (thinking in Alfven waves generated by magnetic reconnection) turns out to be substantially larger than that required to balance the chromospheric energy losses. Here we present a brief re...

  1. Consistent generation of magnetic fields in axion inflation models

    E-Print Network [OSTI]

    Fujita, Tomohiro; Tada, Yuichiro; Takeda, Naoyuki; Tashiro, Hiroyuki

    2015-01-01T23:59:59.000Z

    There has been a growing evidence for the existence of magnetic fields in the extra-galactic regions, while the attempt to associate their origin with the inflationary epoch alone has been found extremely challenging. We therefore take into account the consistent post-inflationary evolution of the magnetic fields that are originated from vacuum fluctuations during inflation. In the model of our interest, the electromagnetic (EM) field is coupled to a pseudo-scalar inflaton $\\phi$ through the characteristic term $\\phi F\\tilde F$, breaking the conformal invariance. This interaction dynamically breaks the parity and enables a continuous production of only one of the polarization states of the EM field through tachyonic instability. The produced magnetic fields are thus helical. We find that the dominant contribution to the observed magnetic fields in this model comes from the modes that leave the horizon near the end of inflation, further enhanced by the tachyonic instability right after the end of inflation. Th...

  2. Magnetic field effects on the thermonuclear combustion front of Chandrasekhar mass white dwarfs

    E-Print Network [OSTI]

    Cristian R. Ghezzi; Elisabete M. de Gouveia Dal Pino; Jorge E. Horvath

    2000-12-06T23:59:59.000Z

    The explosion of a type Ia supernova starts in a white dwarf as a laminar deflagration at the center of the star and soon several hydrodynamic instabilities, in particular, the Rayleigh-Taylor instability, begin to act. A cellular stationary combustion and a turbulent combustion regime are rapidly achieved by the flame and maintained up to the end of the so-called flamelet regime when the transition to detonation is believed to occur. The burning velocity at these regimes is well described by the fractal model of combustion. Using a semi-analytic approach, we describe the effect of magnetic fields on the fractalization of the front considering a white dwarf with a nearly dipolar magnetic field. We find an intrinsic asymmetry on the velocity field that may be maintained up to the free expansion phase of the remnant. Considering the strongest values inferred for a white dwarf's magnetic fields with strengths up to $10^{8}-10^{9}$ G at the surface and assuming that the field near the centre is roughly 10 times greater, asymmetries in the velocity field higher than $10-20 %$ are produced between the magnetic polar and the equatorial axis of the remnant which may be related to the asymmetries found from recent spectropolarimetric observations of very young SN Ia remnants. Dependence of the asymmetry with white dwarf composition is also analyzed.

  3. Magnetic field in holographic superconductor with dark matter sector

    E-Print Network [OSTI]

    Nakonieczny, L; Wysokinski, K I

    2015-01-01T23:59:59.000Z

    Based on the analytical technique the effect of the static magnetic field on the s-wave holographic superconductor with dark matter sector of U(1)-gauge field type coupled to the Maxwell field has been examined. In the probe limit, we obtained the mean value of the condensation operator. The nature of the condensate in an external magnetic field as well as the behaviour of the critical field close to the transition temperature has been revealed. The obtained upturn of the critical field curves as a function of temperature, both in four and five spacetime dimensions, is a fingerprint of the strong coupling approach.

  4. On Possible Light-Torsion Mixing in Background Magnetic Field

    E-Print Network [OSTI]

    S. I. Kruglov

    2009-07-10T23:59:59.000Z

    The interaction of the light with propagating axial torsion fields in the presence of an external magnetic field has been investigated. Axial torsion fields appearing in higher derivative quantum gravity possess two states, with spin one and zero, with different masses. The torsion field with spin-0 state is a ghost that can be removed if its mass is infinite. We investigate the possibility when the light mixes with the torsion fields resulting in the effect of vacuum birefringence and dichroism. The expressions for ellipticity and the rotation of light polarization axis depending on the coupling constant and the external magnetic field have been obtained.

  5. Bose Glass of Quasiparticles in Doped Quantum Magnet Gregory S. Boebinger, National High Magnetic Field Laboratory

    E-Print Network [OSTI]

    Weston, Ken

    Bose Glass of Quasiparticles in Doped Quantum Magnet Gregory S. Boebinger, National High Magnetic. This BEC can localize in the presence of disorder caused by Br- doping to form a Bose Glass. The BEC-Bose Glass (BEC-BG) transition can be carefully controlled by magnetic field, allowing us to sensitively

  6. Magnetic anisotropy in Fe-25Cr-12Co-1Si alloy induced by external magnetic field

    E-Print Network [OSTI]

    Qin, Lu-Chang

    Magnetic anisotropy in Fe-25Cr-12Co-1Si alloy induced by external magnetic field ZHEN Liang( )1 of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China; 2. Department 27599-3255, USA Received 29 June 2006; accepted 15 January 2007 Abstract: Structural and magnetic

  7. Wouthuysen-Field coupling strength and application to high-redshift 21 cm radiation

    E-Print Network [OSTI]

    Christopher M. Hirata

    2005-12-05T23:59:59.000Z

    The first UV sources in the universe are expected to have coupled the HI spin temperature to the gas kinetic temperature via scattering in the Lyman-alpha resonance [the Wouthuysen-Field (WF) effect]. By establishing an HI spin temperature different from the temperature of the CMB, the WF effect should allow observations of HI during the reionization epoch in the redshifted 21 cm line. This paper investigates four mechanisms that can affect the strength of the WF effect that were not previously considered: (1) Photons redshifting into the HI Lyman resonances may excite an H atom and result in a radiative cascade terminating in two-photon 2s->1s emission, rather than always degrading to Lyman-alpha as usually assumed. (2) The fine structure of the Lyman-alpha resonance alters the photon frequency distribution and leads to a suppression of the scattering rate. (3) The spin-flip scatterings change the frequency of the photon and cause the photon spectrum to relax not to the kinetic temperature of the gas but to a temperature between the kinetic and spin temperatures, effectively reducing the strength of the Wouthuysen-Field coupling. (4) Near line centre, a photon can change its frequency by several times the line width in a single scattering event, thus potentially invalidating the usual calculation of the Lyman-alpha spectral distortion based on the diffusion approximation. It is shown that (1) suppresses the WF coupling strength by a factor of up to ~2, while (2) and (3) are important only at low kinetic temperatures. Effect (4) has a =2K. If the pre-reionization IGM was efficiently heated by X-rays, only effect (1) is important. Fitting formulae are provided for the range of T_k>=2K and Gunn-Peterson optical depth 10^5--10^7. [ABRIDGED

  8. Color superconductivity in a strong external magnetic field

    E-Print Network [OSTI]

    Cristina Manuel

    2006-07-26T23:59:59.000Z

    We explore the effects of an applied strong external magnetic field in a three flavor massless color superconductor. The long-range component of the B field that penetrates the superconductor enhances some quark condensates, leading to a different condensation pattern. The external field also reduces the flavor symmetries in the system, and thus it changes drastically the corresponding low energy physics. Our considerations are relevant for the study of highly magnetized compact stars.

  9. Relation between photospheric flow fields and the magnetic field distribution on the solar surface

    SciTech Connect (OSTI)

    Simon, G.W.; Title, A.M.; Topka, K.P.; Tarbell, T.D.; Shine, R.A.

    1988-04-01T23:59:59.000Z

    Using the technique of local correlation tracking on a 28 minute time sequence of white-light images of solar granulation, the horizontal flow field on the solar surface is measured. The time series was obtained by the Solar Optical Universal Polarimeter (SOUP) on Spacelab 2 (Space Shuttle flight 51-F) and is free from atmospheric blurring and distortion. The SOUP flow fields have been compared with carefully aligned magnetograms taken over a nine hour period at the Big Bear Solar Observatory before, during, and after the SOUP images. The flow field and the magnetic field agree in considerable detail: vectors which define the flow of the white-light intensity pattern (granulation) point toward magnetic field regions, magnetic fields surround flow cells, and magnetic features move along the flow arrows. The projected locations of free particles (corks) in the measured flow field congregate at the same locations where the magnetic field is observed. 31 references.

  10. Constraining primordial magnetic fields with future cosmic shear surveys

    SciTech Connect (OSTI)

    Fedeli, C. [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Moscardini, L., E-mail: cosimo.fedeli@astro.ufl.edu, E-mail: lauro.moscardini@unibo.it [Dipartimento di Astronomia, Università di Bologna, Via Ranzani 1, 40127 Bologna (Italy)

    2012-11-01T23:59:59.000Z

    The origin of astrophysical magnetic fields observed in galaxies and clusters of galaxies is still unclear. One possibility is that primordial magnetic fields generated in the early Universe provide seeds that grow through compression and turbulence during structure formation. A cosmological magnetic field present prior to recombination would produce substantial matter clustering at intermediate/small scales, on top of the standard inflationary power spectrum. In this work we study the effect of this alteration on one particular cosmological observable, cosmic shear. We adopt the semi-analytic halo model in order to describe the non-linear clustering of matter, and feed it with the altered mass variance induced by primordial magnetic fields. We find that the convergence power spectrum is, as expected, substantially enhanced at intermediate/small angular scales, with the exact amplitude of the enhancement depending on the magnitude and power-law index of the magnetic field power spectrum. Specifically, for a fixed amplitude, the effect of magnetic fields is larger for larger spectral indices. We use the predicted statistical errors for a future wide-field cosmic shear survey, on the model of the ESA Cosmic Vision mission Euclid, in order to forecast constraints on the amplitude of primordial magnetic fields as a function of the spectral index. We find that the amplitude will be constrained at the level of ? 0.1 nG for n{sub B} ? ?3, and at the level of ? 10{sup ?7} nG for n{sub B} ? 3. The latter is at the same level of lower bounds coming from the secondary emission of gamma-ray sources, implying that for high spectral indices Euclid will certainly be able to detect primordial magnetic fields, if they exist. The present study shows how large-scale structure surveys can be used for both understanding the origins of astrophysical magnetic fields and shedding new light on the physics of the pre-recombination Universe.

  11. Magnetic Fields above the Surface of aSuperconductor with Internal Magnetism

    SciTech Connect (OSTI)

    Bluhm, Hendrik; /Stanford U., Phys. Dept. /SLAC, SSRl

    2007-06-26T23:59:59.000Z

    The author presents a method for calculating the magnetic fields near a planar surface of a superconductor with a given intrinsic magnetization in the London limit. He computes solutions for various magnetic domain boundary configurations and derives relations between the spectral densities of the magnetization and the resulting field in the vacuum half space, which are useful if the magnetization can be considered as a statistical quantity and its features are too small to be resolved individually. The results are useful for analyzing and designing magnetic scanning experiments. Application to existing data from such experiments on Sr{sub 2}RuO{sub 4} show that a domain wall would have been detectable, but the magnetic field of randomly oriented small domains and small defects may have been smaller than the experimental noise level.

  12. NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSVOLUME 12 N0. 1 2005

    E-Print Network [OSTI]

    Weston, Ken

    , and Geochemistry 14 MAGNET SCIENCE & TECHNOLOGY Engineering Materials, Instrumentation, and Magnet Technology Magnet Science & Technology 42 7 including Engineering Materials, Instrumentation, and Magnet TechnologyNATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSVOLUME 12 · N0. 1 · 2005 OPERATED BY: FLORIDA STATE

  13. Magnetic Helicity and the Relaxation of Fossil Fields

    E-Print Network [OSTI]

    Avery E. Broderick; Ramesh Narayan

    2007-10-22T23:59:59.000Z

    In the absence of an active dynamo, purely poloidal magnetic field configurations are unstable to large-scale dynamical perturbations, and decay via reconnection on an Alfvenic timescale. Nevertheless, a number of classes of dynamo-free stars do exhibit significant, long-lived, surface magnetic fields. Numerical simulations suggest that the large-scale poloidal field in these systems is stabilized by a toroidal component of the field in the stellar interior. Using the principle of conservation of total helicity, we develop a variational principle for computing the structure of the magnetic field inside a conducting sphere surrounded by an insulating vacuum. We show that, for a fixed total helicity, the minimum energy state corresponds to a force-free configuration. We find a simple class of axisymmetric solutions, parametrized by angular and radial quantum numbers. However, these solutions have a discontinuity in the toroidal magnetic field at the stellar surface which will exert a toroidal stress on the surface of the star. We then describe two other classes of solutions, the standard spheromak solutions and ones with fixed surface magnetic fields, the latter being relevant for neutron stars with rigid crusts. We discuss the implications of our results for the structure of neutron star magnetic fields, the decay of fields, and the origin of variability and outbursts in magnetars.

  14. The small scale dynamo and the amplification of magnetic fields in massive primordial haloes

    E-Print Network [OSTI]

    Latif, M A; Schmidt, W; Niemeyer, J

    2012-01-01T23:59:59.000Z

    While our present standard model of cosmology yields no clear prediction for the initial magnetic field strength, efficient dynamo action may compensate for initially weak seed fields via rapid amplification. In particular, the small-scale dynamo is expected to exponentially amplify any weak magnetic field in the presence of turbulence. We explore whether this scenario is viable using cosmological magneto-hydrodynamics simulations modeling the formation of the first galaxies, which are expected to form in so-called atomic cooling halos with virial temperatures $\\rm T_{vir} \\geq 10^{4}$ K. As previous calculations have shown that a high Jeans resolution is needed to resolve turbulent structures and dynamo effects, our calculations employ resolutions of up to 128 cells per Jeans length. The presence of the dynamo can be clearly confirmed for resolutions of at least 64 cells per Jeans length, while saturation occurs at approximate equipartition with turbulent energy. As a result of the large Reynolds numbers in ...

  15. Modeling spin magnetization transport in a spatially varying magnetic field

    E-Print Network [OSTI]

    Rico A. R. Picone; Joseph L. Garbini; John A. Sidles

    2014-08-13T23:59:59.000Z

    We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment. A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation.

  16. Magnetic Field Geometry in "Red" and "Blue" BL Lacs

    E-Print Network [OSTI]

    P. Kharb; D. C. Gabuzda; P. Shastri

    2003-01-06T23:59:59.000Z

    We compare the systematics of the magnetic field geometry in the "red" low-energy peaked BL Lacs (LBLs) and "blue" high-energy peaked BL Lacs (HBLs) using VLBI polarimetric images. The LBLs are primarily "radio--selected" BL Lacs and the HBLs are primarily "X-ray selected". In contrast to the LBLs, which show predominantly transverse jet magnetic fields, the HBLs show predominantly longitudinal fields. Thus, while the SED peaks of core-dominated quasars, LBLs and HBLs form a sequence of increasing frequency, the magnetic field geometry does not follow an analogous sequence. We briefly investigate possible connections between the observed parsec-scale magnetic field structures and circular polarization measurements in the literature on various spatial scales.

  17. Electromagnetic Waves Reflectance of Graphene -- Magnetic Semiconductor Superlattice in Magnetic Field

    E-Print Network [OSTI]

    Kuzmin, Dmitry A; Shavrov, Vladimir G

    2014-01-01T23:59:59.000Z

    Electrodynamic properties of the graphene - magnetic semiconductor - graphene superlattice placed in magnetic field have been investigated theoretically in Faraday geometry with taking into account dissipation processes. Frequency and field dependences of the reflectance, transmittance and absorbtance of electromagnetic waves by such superlattice have been calculated for different numbers of periods of the structure and different sizes of the periods with using a transfer matrix method. The possibility of efficient control of electrodynamic properties of graphene - magnetic semiconductor - graphene superlattice has been shown.

  18. Neutrino magnetic moment in a magnetized plasma

    E-Print Network [OSTI]

    N. V. Mikheev; E. N. Narynskaya

    2010-11-08T23:59:59.000Z

    The contribution of a magnetized plasma to the neutrino magnetic moment is calculated. It is shown that only part of the additional neutrino energy in magnetized plasma connecting with its spin and magnetic field strength defines the neutrino magnetic moment. It is found that the presence of magnetized plasma does not lead to the considerable increase of the neutrino magnetic moment in contrast to the results presented in literature previously.

  19. Effects of non-radial magnetic field on measuring magnetic helicity transport across solar photosphere

    E-Print Network [OSTI]

    Song, Yongliang

    2015-01-01T23:59:59.000Z

    It is generally believed that the evolution of magnetic helicity has a close relationship with solar activity. Before the launch of SDO, earlier studies have mostly used MDI/SOHO line of sight magnetograms and assumed that magnetic fields are radial when calculating magnetic helicity injection rate from photospheric magnetograms. However, this assumption is not necessarily true. Here we use the vector magnetograms and line of sight magnetograms, both taken by HMI/SDO, to estimate the effects of non-radial magnetic field on measuring magnetic helicity injection rate. We find that: 1) The effect of non-radial magnetic field on estimating tangential velocity is relatively small; 2) On estimating magnetic helicity injection rate, the effect of non-radial magnetic field is strong when active regions are observed near the limb and is relatively small when active regions are close to disk center; 3) The effect of non-radial magnetic field becomes minor if the amount of accumulated magnetic helicity is the only conce...

  20. Heat pipes for use in a magnetic field

    DOE Patents [OSTI]

    Werner, R.W.; Hoffman, M.A.

    1983-07-19T23:59:59.000Z

    A heat pipe configuration for use in a magnetic field environment of a fusion reactor is disclosed. Heat pipes for operation in a magnetic field when liquid metal working fluids are used are optimized by flattening of the heat pipes having an unobstructed annulus which significantly reduces the adverse side region effect of the prior known cylindrically configured heat pipes. The flattened heat pipes operating in a magnetic field can remove 2--3 times the heat as a cylindrical heat pipe of the same cross sectional area. 4 figs.

  1. Universality of critical magnetic field in holographic superconductor

    E-Print Network [OSTI]

    D. Momeni; R. Myrzakulov

    2015-02-11T23:59:59.000Z

    In this letter we study aspects of the holographic superconductors analytically in the presence of a constant external magnetic field. We show that the critical temperature and critical magnetic field can be calculated at nonzero temperature. We detect the Meissner effect in such superconductors. A universal relation between black hole mass $ M$ and critical magnetic field $H_c$ is proposed as $\\frac{H_c}{M^{2/3}}\\leq 0.687365$. We discuss some aspects of phase transition in terms of black hole entropy and the Bekenstein's entropy to energy upper bound.

  2. Development of active regions: flows, magnetic-field patterns and bordering effect

    E-Print Network [OSTI]

    Getling, A V; Buchnev, A A

    2015-01-01T23:59:59.000Z

    A qualitative analysis is given to the data on the full magnetic and velocity vector fields in a growing sunspot group, recorded nearly simultaneously with the Solar Optical Telescope on the Hinode satellite. Observations of a young bipolar subregion developing within AR 11313 were carried out on 9-10 October 2011. Our aim was to form am idea about the consistency of the observed pattern with the well-known rising-tube model of the formation of bipolar acrive regions and sunspot groups. We find from our magnetograms that the distributions of the vertical [B_v] and the horizontal [B_h] component of the magnetic field over the area of the magnetic subregion are spatially well correlated; in contrast, the rise of a flux-tube loop would result in a qualitatively different pattern, with the maxima of the two magnetic-field components spatially separated: the vertical field would be the strongest where either spot emerges, while the maximum horizontal-field strengths would be reached in between them. A specific fea...

  3. A new magnetic field integral measurement system

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    measurements. b. Second field integral (horizontal and vertical) measurements. c. Multipole components of first field integral measurements. 2. Translation Coil a. Multipole...

  4. Impact of Dynamic Magnetic fields on the CLIC Main Beam

    E-Print Network [OSTI]

    Snuverink, J; Jach, C; Jeanneret, JB; Schulte, D; Stulle, F

    2010-01-01T23:59:59.000Z

    The Compact Linear Collider (CLIC) accelerator has strong precision requirements on the position of the beam. The beam position will be sensitive to external dynamic magnetic fields (stray fields) in the nanotesla regime. The impact of these fields on the CLIC main beam has been studied by performing simulations on the lattices and tolerances have been determined. Several mitigation techniques will be discussed.

  5. Magnetic Field Confinement in the Corona: The Role of Magnetic Helicity Accumulation

    E-Print Network [OSTI]

    Mei Zhang; Natasha Flyer; Boon Chye Low

    2006-03-01T23:59:59.000Z

    A loss of magnetic field confinement is believed to be the cause of coronal mass ejections (CMEs), a major form of solar activity in the corona. The mechanisms for magnetic energy storage are crucial in understanding how a field may possess enough free energy to overcome the Aly limit and open up. Previously, we have pointed out that the accumulation of magnetic helicity in the corona plays a significant role in storing magnetic energy. In this paper, we investigate another hydromagnetic consequence of magnetic-helicity accumulation. We propose a conjecture that there is an upper bound on the total magnetic helicity that a force-free field can contain. This is directly related to the hydromagnetic property that force-free fields in unbounded space have to be self-confining. Although a mathematical proof of this conjecture for any field configuration is formidable, its plausibility can be demonstrated with the properties of several families of power-law, axisymmetric force-free fields. We put forth mathematical evidence, as well as numerical, indicating that an upper bound on the magnetic helicity may exist for such fields. Thus, the accumulation of magnetic helicity in excess of this upper bound would initiate a non-equilibrium situation, resulting in a CME expulsion as a natural product of coronal evolution.

  6. Detection of a magnetic field on HD108: clues to extreme magnetic braking and the Of?p phenomenon

    E-Print Network [OSTI]

    Martins, F; Marcolino, W L F; Bouret, J -C; Wade, G A; Escolano, C; Howarth, I D

    2010-01-01T23:59:59.000Z

    We report the detection of a magnetic field on the Of?p star HD108. Spectropolarimetric observations conducted in 2007, 2008 and 2009 respectively with NARVAL@TBL and ESPaDOnS@CFHT reveal a clear Zeeman signature in the average Stokes V profile, stable on timescales of days to months and slowly increasing in amplitude on timescales of years. We speculate that this timescale is the same as that on which Ha emission is varying and is equal to the rotation period of the star. The corresponding longitudinal magnetic field, measured during each of the three seasons, increases slowly from 100 to 150G, implying that the polar strength of the putatively-dipolar large-scale magnetic field of HD108 is at least 0.5kG and most likely of the order of 1-2 kG. The stellar and wind properties are derived through a quantitative spectroscopic analysis with the code CMFGEN. The effective temperature is difficult to constrain because of the unusually strong HeI4471 and HeI5876 lines. Values in the range 33000-37000 K are preferr...

  7. Influence of primordial magnetic fields on 21 cm emission

    E-Print Network [OSTI]

    Dominik R. G. Schleicher; Robi Banerjee; Ralf S. Klessen

    2008-12-17T23:59:59.000Z

    Magnetic fields in the early universe can significantly alter the thermal evolution and the ionization history during the dark ages. This is reflected in the 21 cm line of atomic hydrogen, which is coupled to the gas temperature through collisions at high redshifts, and through the Wouthuysen-Field effect at low redshifts. We present a semi-analytic model for star formation and the build-up of a Lyman alpha background in the presence of magnetic fields, and calculate the evolution of the mean 21 cm brightness temperature and its frequency gradient as a function of redshift. We further discuss the evolution of linear fluctuations in temperature and ionization in the presence of magnetic fields and calculate the effect on the 21 cm power spectrum. At high redshifts, the signal is increased compared to the non-magnetic case due to the additional heat input into the IGM from ambipolar diffusion and the decay of MHD turbulence. At lower redshifts, the formation of luminous objects and the build-up of a Lyman alpha background can be delayed by a redshift interval of 10 due to the strong increase of the filtering mass scale in the presence of magnetic fields. This tends to decrease the 21 cm signal compared to the zero-field case. In summary, we find that 21 cm observations may become a promising tool to constrain primordial magnetic fields.

  8. Dredging-induced near-field resuspended sediment concentrations and source strengths. Final report

    SciTech Connect (OSTI)

    Collins, M.A.

    1995-08-01T23:59:59.000Z

    Dredging in riverine, lacustrine, and estuarine environments introduces bottom sediments into overlying waters because of imperfect entrainment and incomplete capture of sediments resuspended during the dredging process and the spillage or leakage of sediments during subsequent transportation and disposal of the dredged sediments. Resuspension of bottom sediments and resulting dispersal may pose water quality problems in waters near dredging operations. Interest in this issue increases when the sediment being dredged is highly contaminated. Resuspension of sediments by dredging is affected by dredge characteristics, dredge operating conditions, properties of bottom and suspended sediments, and site-specific conditions such as bottom topography, ambient current, and depth. This report summarizes field studies conducted by the U.S. Army Corps of Engineers to assess the suspended sediment concentrations in the water column in the vicinity of various dredge types. These concentration data are combined with conceptual models for resuspended sediment source strength geometries and velocity patterns to estimate sediment source strengths for cutterhead and clamshell dredges. Although unverified, these models provide a starting point for a more thorough analytical evaluation of the entire resuspension, transport, and deposition process.

  9. Magnetic Fields in Blazar Pc-scale Jets - Possible connection to Spin Rates of Black holes ?

    E-Print Network [OSTI]

    P. Kharb; M. L. Lister; P. Shastri

    2008-03-06T23:59:59.000Z

    We re-examine the differences observed in the pc-scale magnetic field geometry of high and low optical polarization Quasars (HPQs, LPRQs) using the MOJAVE sample. We find that, as previously reported, HPQ jets exhibit predominantly transverse B fields while LPRQ jets tend to display longitudinal B fields. We attempt to understand these results along with the different B field geometry observed in the low and high energy peaked BL Lacs (LBLs, HBLs) using a simple picture wherein the spinning central black holes in these AGNs influence the speed and strength of the jet components (spine, sheath). Higher spin rates in HPQs compared to LPRQs and LBLs compared to HBLs could explain the different total radio powers, VLBI jet speeds, and the observed B field geometry in these AGN classes.

  10. 1 Magnetic Fields and Solar This article describesthe relationshipbetweenmagnetic

    E-Print Network [OSTI]

    reconnection. The free magnetic energy is con- verted to thermal and non- thermal energy to power solar ares, which create thermal emissions and accel- eration of non-thermal particles. The total energy1 Magnetic Fields and Solar Flares This article describesthe relationshipbetweenmagnetic elds

  11. November 18, 2005 Chandra Observations of Magnetic Fields and Relativistic

    E-Print Network [OSTI]

    Schwartz, Daniel

    November 18, 2005 Chandra Observations of Magnetic Fields and Relativistic Beaming in Four Quasar microwave background. If particles and magnetic #12;elds are near minimum energy density 1 Harvard CSIRO Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia 4 Jet Propulsion

  12. Terahertz radiation detection by field effect transistor in magnetic field S. Boubanga-Tombet,1,a

    E-Print Network [OSTI]

    Levelut, Claire

    Terahertz radiation detection by field effect transistor in magnetic field S. Boubanga-Tombet,1,a M; accepted 30 July 2009; published online 19 August 2009 We report on terahertz radiation detection with In

  13. The Stability of Magnetized Rotating Plasmas with Superthermal Fields

    E-Print Network [OSTI]

    Pessah, M E

    2004-01-01T23:59:59.000Z

    During the last decade it has become evident that the magnetorotational instability is at the heart of the enhanced angular momentum transport in weakly magnetized accretion disks around neutron stars and black holes. In this paper, we investigate the local linear stability of differentially rotating, magnetized flows and the evolution of the magnetorotational instability beyond the weak-field limit. We show that, when superthermal toroidal fields are considered, both compressibility and magnetic tension terms, related to the curvature of toroidal field lines, should be taken fully into account. We demonstrate that, contrary to the results of most previous investigations, the presence of a toroidal component in the magnetic field plays a crucial role not only in the growth rates of the unstable modes but also in determining which modes are subject to instabilities. We find that, for rotationally supported configurations, the magnetorotational instability is stabilized at low wavenumbers for toroidal Alfven sp...

  14. Magnetic Fields in High-Density Stellar Matter

    E-Print Network [OSTI]

    German Lugones

    2005-04-20T23:59:59.000Z

    I briefly review some aspects of the effect of magnetic fields in the high density regime relevant to neutron stars, focusing mainly on compact star structure and composition, superconductivity, combustion processes, and gamma ray bursts.

  15. Low-field classroom nuclear magnetic resonance system

    E-Print Network [OSTI]

    Zimmerman, Clarissa Lynette

    2010-01-01T23:59:59.000Z

    The goal of this research was to develop a Low-field Classroom NMR system that will enable hands-on learning of NMR and MRI concepts in a Biological-Engineering laboratory course. A permanent magnet system, designed using ...

  16. Ferrofluid surface and volume flows in uniform rotating magnetic fields

    E-Print Network [OSTI]

    Elborai, Shihab M. (Shihab Mahmoud), 1977-

    2006-01-01T23:59:59.000Z

    Ferrofluid surface and volume effects in uniform dc and rotating magnetic fields are studied. Theory and corroborating measurements are presented for meniscus shapes and resulting surface driven flows, spin-up flows, and ...

  17. A Holographic Superconductor in an External Magnetic Field

    E-Print Network [OSTI]

    Tameem Albash; Clifford V. Johnson

    2008-09-24T23:59:59.000Z

    We study a system of a complex charged scalar coupled to a Reissner-Nordstrom black hole in 3+1 dimensional anti-de Sitter spacetime, neglecting back-reaction. With suitable boundary conditions, the cases of a neutral and purely electric black hole have been studied in various limits and were shown to yield key elements of superconductivity in the dual 2+1 dimensional field theory, forming a condensate below a critical temperature. By adding magnetic charge to the black hole, we immerse the superconductor into an external magnetic field. We show that a family of condensates can form and we examine their structure. For finite magnetic field, they are localized in one dimension with a profile that is exactly solvable, since it maps to the quantum harmonic oscillator. As the magnetic field increases, the condensate shrinks in size, which is reminiscent of the Meissner effect.

  18. Error field and magnetic diagnostic modeling for W7-X

    SciTech Connect (OSTI)

    Lazerson, Sam A. [PPPL; Gates, David A. [PPPL; NEILSON, GEORGE H. [PPPL; OTTE, M.; Bozhenkov, S.; Pedersen, T. S.; GEIGER, J.; LORE, J.

    2014-07-01T23:59:59.000Z

    The prediction, detection, and compensation of error fields for the W7-X device will play a key role in achieving a high beta (? = 5%), steady state (30 minute pulse) operating regime utilizing the island divertor system [1]. Additionally, detection and control of the equilibrium magnetic structure in the scrape-off layer will be necessary in the long-pulse campaign as bootstrapcurrent evolution may result in poor edge magnetic structure [2]. An SVD analysis of the magnetic diagnostics set indicates an ability to measure the toroidal current and stored energy, while profile variations go undetected in the magnetic diagnostics. An additional set of magnetic diagnostics is proposed which improves the ability to constrain the equilibrium current and pressure profiles. However, even with the ability to accurately measure equilibrium parameters, the presence of error fields can modify both the plasma response and diverter magnetic field structures in unfavorable ways. Vacuum flux surface mapping experiments allow for direct measurement of these modifications to magnetic structure. The ability to conduct such an experiment is a unique feature of stellarators. The trim coils may then be used to forward model the effect of an applied n = 1 error field. This allows the determination of lower limits for the detection of error field amplitude and phase using flux surface mapping. *Research supported by the U.S. DOE under Contract No. DE-AC02-09CH11466 with Princeton University.

  19. Parallel heat flux and flow acceleration in open field line plasmas with magnetic trapping

    SciTech Connect (OSTI)

    Guo, Zehua; Tang, Xian-Zhu; McDevitt, Chris [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

    2014-10-15T23:59:59.000Z

    The magnetic field strength modulation in a tokamak scrape-off layer (SOL) provides both flux expansion next to the divertor plates and magnetic trapping in a large portion of the SOL. Previously, we have focused on a flux expander with long mean-free-path, motivated by the high temperature and low density edge anticipated for an absorbing boundary enabled by liquid lithium surfaces. Here, the effects of magnetic trapping and a marginal collisionality on parallel heat flux and parallel flow acceleration are examined. The various transport mechanisms are captured by kinetic simulations in a simple but representative mirror-expander geometry. The observed parallel flow acceleration is interpreted and elucidated with a modified Chew-Goldberger-Low model that retains temperature anisotropy and finite collisionality.

  20. Warm inflation in the presence of magnetic fields

    E-Print Network [OSTI]

    Gabriella Piccinelli; Angel Sanchez; Alejandro Ayala; Ana Julia Mizher

    2014-09-08T23:59:59.000Z

    We study the effects of primordial magnetic fields on the inflationary potential in the context of a warm inflation scenario. The model, based on global supersymmetry with a new-inflation-type potential and a coupling between the inflaton and a heavy intermediate superfield, is already known to preserve the flatness required for slow-roll conditions even after including thermal contributions. Here we show that the magnetic field makes the potential even flatter, retarding the transition and rendering it smoother.

  1. GUT Cosmic Magnetic Fields in a Warm Inflationary Universe

    E-Print Network [OSTI]

    Arjun Berera; Thomas W. Kephart; Stuart D. Wick

    1998-11-03T23:59:59.000Z

    Sources of magnetic fields from grand unified theories are studied in the warm inflation regime. A ferromagnetic Savvidy vacuum scenario is presented that yields observationally interesting large scale magnetic fields. As an intermediate step, a general analysis is made of defect production at the onset of warm inflation and monopole constraints are obtained. Many features of this Savvidy vacuum scenario are applicable within a supercooled inflation regime and these points are discussed.

  2. One-way Ponderomotive Barrier in a Uniform Magnetic Field

    SciTech Connect (OSTI)

    I.Y. Dodin; N.J. Fisch

    2005-02-14T23:59:59.000Z

    The possibility of an asymmetric ponderomotive barrier in a nonuniform dc magnetic field by high-frequency radiation near the cyclotron resonance for selected plasma species was contemplated in Physics of Plasmas 11 (November 2004) 5046-5064. Here we show that a similar one-way barrier, which reflects particles incident from one side while transmitting those incident from the opposite side, can be produced also in a uniform magnetic field, entirely due to inhomogeneity of high-frequency drive.

  3. Propellantless propulsion in magnetic fields by partially shielded current

    E-Print Network [OSTI]

    Bergamin, L; Pinchook, A

    2006-01-01T23:59:59.000Z

    A new device for propellantless propulsion in presence of a magnetic field is discussed. The functional principle shares some features with electrodynamic tethers. However, the tether structure is replaced by a closed wire, which is partially shielded from the magnetic field by means of a superconductor. Therefore, it does not depend on the presence of a plasma. We show that even a relatively small device can yield interesting propulsivet forces for drag compensation or for orbital transfers.

  4. Phase-field simulation of electric-field-induced in-plane magnetic domain switching in magnetic/ferroelectric layered heterostructures

    E-Print Network [OSTI]

    Chen, Long-Qing

    ). An alternative approach to engineering low electric- field-induced magnetic domain switching at room temperaPhase-field simulation of electric-field-induced in-plane magnetic domain switching in magnetic. Phys. Lett. 99, 182510 (2011) Quantum tunneling of the Bloch point in a magnetic film with strong

  5. Prospects for x-ray polarimetry measurements of magnetic fields in magnetized liner inertial fusion plasmas

    SciTech Connect (OSTI)

    Lynn, Alan G., E-mail: lynn@ece.unm.edu; Gilmore, Mark [Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2014-11-15T23:59:59.000Z

    Magnetized Liner Inertial Fusion (MagLIF) experiments, where a metal liner is imploded to compress a magnetized seed plasma may generate peak magnetic fields ?10{sup 4} T (100 Megagauss) over small volumes (?10{sup ?10}m{sup 3}) at high plasma densities (?10{sup 28}m{sup ?3}) on 100 ns time scales. Such conditions are extremely challenging to diagnose. We discuss the possibility of, and issues involved in, using polarimetry techniques at x-ray wavelengths to measure magnetic fields under these extreme conditions.

  6. Parsec-scale Investigation of the Magnetic Field Structure of Several AGN Jets

    E-Print Network [OSTI]

    Shane P. O'Sullivan; Denise C. Gabuzda

    2008-01-31T23:59:59.000Z

    Multi-frequency (4.6, 5, 5.5, 8, 8.8, 13, 15, 22 & 43 GHz) polarization observations of 6 "blazars" were obtained on the American Very Long Baseline Array (VLBA) over a 24-hr period on 2 July 2006. Observing at several frequencies, separated by short and long intervals, enabled reliable determination of the distribution of Faraday Rotation on a range of scales. In all cases the magnitude of the RM increases in the higher frequency observations, implying that the electron density and/or magnetic field strength is increasing as we get closer to the central engine. After correcting for Faraday rotation, the polarization orientation in the jet is either parallel or perpendicular to the jet direction. A transverse Rotation Measure (RM) gradient was detected in the jet of 0954+658, providing evidence for the presence of a helical magnetic field surrounding the jet. For three of the sources (0954+658, 1418+546, 2200+420), the sign of the RM in the core region changes in different frequency-intervals, indicating that the line-of-sight component of the magnetic field is changing with distance from the base of the jet. We suggest an explanation for this in terms of bends in a relativistic jet surrounded by a helical magnetic field; where there is no clear evidence for pc-scale bends, the same effect can be explained by an accelerating/decelerating jet.

  7. Torsional Oscillations of Relativistic Stars with Dipole Magnetic Fields II. Global Alfvén Modes

    E-Print Network [OSTI]

    H. Sotani; K. D. Kokkotas; N. Stergioulas; M. Vavoulidis

    2006-11-21T23:59:59.000Z

    We investigate torsional Alfv\\'{e}n modes of relativistic stars with a global dipole magnetic field. It has been noted recently (Glampedakis et al. 2006) that such oscillation modes could serve as as an alternative explanation (in contrast to torsional crustal modes) for the SGR phenomenon, if the magnetic field is not confined to the crust. We compute global Alfv\\'{e}n modes for a representative sample of equations of state and magnetar masses, in the ideal MHD approximation and ignoring $\\ell \\pm 2$ terms in the eigenfunction. We find that the presence of a realistic crust has a negligible effect on Alfv\\'{e}n modes for $B > 4\\times 10^{15}$ G. Furthermore, we find strong avoided crossings between torsional Alfv\\'{e}n modes and torsional crust modes. For magnetar-like magnetic field strengths, the spacing between consecutive Alfv\\'{e}n modes is of the same order as the gap of avoided crossings. As a result, it is not possible to identify modes of predominantly crustal character and all oscillations are predominantly Alfv\\'{e}n-like. Interestingly, we find excellent agreement between our computed frequencies and observed frequencies in two SGRs, for a maximum magnetic field strenght in the range of (0.8--1.2)$\\times 10^{16}$ G.

  8. Plasma control by modification of helicon wave propagation in low magnetic fields

    SciTech Connect (OSTI)

    Lafleur, T.; Charles, C.; Boswell, R. W. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, Australian National University, Canberra, Australian Capital Territory 0200 (Australia)

    2010-07-15T23:59:59.000Z

    By making use of nonuniform magnetic fields, it is shown experimentally that control of helicon wave propagation can be achieved in a low pressure (0.08 Pa) expanding plasma. The m=1 helicon waves are formed during a direct capacitive to wave mode transition that occurs in a low diverging magnetic field (B{sub 0}<3 mT). In this initial configuration, waves are prevented from reaching the downstream region, but slight modifications to the magnetic field allows the axial distance over which waves can propagate to be controlled. By changing the effective propagation distance in this way, significant modification of the density and plasma potential profiles can be achieved, showing that the rf power deposition can be spatially controlled as well. Critical to the modification of the wave propagation behavior is the magnetic field strength (and geometry) near the exit of the plasma source region, which gives electron cyclotron frequencies close to the wave frequency of 13.56 MHz.

  9. Collisionless Shocks -- Magnetic Field Generation and Particle Acceleration

    E-Print Network [OSTI]

    J. Trier Frederiksen; C. B. Hededal; T. Haugboelle; A. Nordlund

    2003-03-16T23:59:59.000Z

    We present numerical results from plasma particle simulations of collisionless shocks and ultra-relativistic counter-streaming plasmas. We demonstrate how the field-particle interactions lead to particle acceleration behind the shock-front. Further, we demonstrate how ultra relativistic counter-streaming plasmas create large scale patchy magnetic field structures and that these field structures propagate down-stream of the shock front. These results may help explain the origin of the magnetic fields and accelerated electrons responsible for afterglow synchrotron radiation from gamma ray bursts.

  10. Magnetic Fields via Polarimetry: Progress of Grain Alignment Theory

    E-Print Network [OSTI]

    A. Lazarian

    2002-08-28T23:59:59.000Z

    Most astrophysical systems, e.g. stellar winds, the diffuse interstellar medium, molecular clouds, are magnetized with magnetic fields that influence almost all of their properties. One of the most informative techniques of magnetic field studies is based on the use of starlight polarization and polarized emission arising from aligned dust. How reliable the interpretation of the polarization maps in terms of magnetic fields is the issue that the grain alignment theory addresses. Although grain alignment is a problem of half a century standing, recent progress achieved in the field makes us believe that we are approaching the solution of this mystery. I review basic physical processes involved in grain alignment and discuss the niches for different alignment mechanisms. I show why mechanisms that were favored for decades do not look so promising right now, while the radiative torque mechanism ignored for more than 20 years looks so attractive. I define the observational tests and outline the circumstances when grain alignment theory predicts that new yet untapped information of magnetic field structure is available through polarimetry. In particular, I touch upon mapping magnetic fields in circumstellar regions, interplanetary space and in comet comae.

  11. The influence of the magnetic field on the performance of an active magnetic regenerator (AMR)

    E-Print Network [OSTI]

    Bjørk, R

    2014-01-01T23:59:59.000Z

    The influence of the time variation of the magnetic field, termed the magnetic field profile, on the performance of a magnetocaloric refrigeration device using the active magnetic regeneration (AMR) cycle is studied for a number of process parameters for both a parallel plate and packed bed regenerator using a numerical model. The cooling curve of the AMR is shown to be almost linear far from the Curie temperature of the magnetocaloric material. It is shown that a magnetic field profile that is 10% of the cycle time out of sync with the flow profile leads to a drop in both the maximum temperature span and the maximum cooling capacity of 20-40\\% for both parallel plate and packed bed regenerators. The maximum cooling capacity is shown to depend very weakly on the ramp rate of the magnetic field. Reducing the temporal width of the high field portion of the magnetic field profile by 10% leads to a drop in maximum temperature span and maximum cooling capacity of 5-20%. An increase of the magnetic field from 1 T t...

  12. Influence of Time-Varying External Magnetic Fields on Trapped Fields in Bulk Superconductors

    E-Print Network [OSTI]

    Zou, Jin; Ainslie, Mark D.; Hu, Di; Cardwell, David A.

    2014-12-12T23:59:59.000Z

    Large, single-grain bulk high-temperature superconductors (HTS) can trap magnetic fields over 17 T below 30 K and up to 3 T at 77 K, and have significant potential to replace permanent magnets, the fields from which are limited to significantly less...

  13. Study of HTS Wires at High Magnetic Fields

    SciTech Connect (OSTI)

    Turrioni, D.; Barzi, E.; Lamm, M.J.; Yamada, R.; Zlobin, A.V.; Kikuchi, A.; /Fermilab

    2009-01-01T23:59:59.000Z

    Fermilab is working on the development of high field magnet systems for ionization cooling of muon beams. The use of high temperature superconducting (HTS) materials is being considered for these magnets using Helium refrigeration. Critical current (I{sub c}) measurements of HTS conductors were performed at FNAL and at NIMS up to 28 T under magnetic fields at zero to 90 degree with respect to the sample face. A description of the test setups and results on a BSCCO-2223 tape and second generation (2G) coated conductors are presented.

  14. Fluorescent lamp unit with magnetic field generating means

    DOE Patents [OSTI]

    Grossman, M.W.; George, W.A.

    1989-08-08T23:59:59.000Z

    A fluorescent lamp unit having a magnetic field generating means for improving the performance of the fluorescent lamp is disclosed. In a preferred embodiment the fluorescent lamp comprises four longitudinally extending leg portions disposed in substantially quadrangular columnar array and joined by three generally U-shaped portions disposed in different planes. In another embodiment of the invention the magnetic field generating means comprises a plurality of permanent magnets secured together to form a single columnar structure disposed within a centrally located region defined by the shape of lamp envelope. 4 figs.

  15. Tuning magnetic disorder in diluted magnetic semiconductors using high fields to 89 Tesla

    SciTech Connect (OSTI)

    Crooker, Scott A [Los Alamos National Laboratory; Samarth, Nitin [PENN STATE U

    2008-01-01T23:59:59.000Z

    We describe recent and ongoing studies at the National High Magnetic Field Laboratory at Los Alamos using the new '100 Tesla Multi-Shot Magnet', which is presently delivering fields up to {approx}89 T during its commissioning. We discuss the first experiments performed in this magnet system, wherein the linewidth of low-temperature photoluminescence spectra was used to directly reveal the degree of magnetic alloy disorder 'seen' by excitons in single Zn{sub 0.80}Cd{sub 0.22}Mn{sub 0.08}Se quantum wells. The magnetic potential landscape in II-VI diluted magnetic semiconductors (DMS) is typically smoothed when the embedded Mn{sup 2+} spins align in an applied field. However, an important (but heretofore untested) prediction of current models of compositional disorder is that magnetic alloy fluctuations in many DMS compounds should increase again in very large magnetic fields approaching 100 T. We observed precisely this increase above {approx}70 T, in agreement with a simple model of magnetic alloy disorder.

  16. Three-dimensional simulations of molecular cloud fragmentation regulated by magnetic fields and ambipolar diffusion

    E-Print Network [OSTI]

    Takahiro Kudoh; Shantanu Basu; Youichi Ogata; Takashi Yabe

    2007-06-19T23:59:59.000Z

    We employ the first fully three-dimensional simulation to study the role of magnetic fields and ion-neutral friction in regulating gravitationally-driven fragmentation of molecular clouds. The cores in an initially subcritical cloud develop gradually over an ambipolar diffusion time while the cores in an initially supercritical cloud develop in a dynamical time. The infall speeds on to cores are subsonic in the case of an initially subcritical cloud, while an extended (\\ga 0.1 pc) region of supersonic infall exists in the case of an initially supercritical cloud. These results are consistent with previous two-dimensional simulations. We also found that a snapshot of the relation between density (rho) and the strength of the magnetic field (B) at different spatial points of the cloud coincides with the evolutionary track of an individual core. When the density becomes large, both relations tend to B \\propto \\rho^{0.5}.

  17. Patterning of hydrogenated microcrystalline silicon growth by magnetic field

    SciTech Connect (OSTI)

    Fejfar, A.; Stuchlik, J.; Mates, T.; Ledinsky, M.; Honda, S.; Kocka, J. [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 53 Prague 6 (Czech Republic)

    2005-07-04T23:59:59.000Z

    A way of influencing growth of silicon films by magnetic field is demonstrated. Permanent magnet(s) placed under the substrate influenced the discharge in a mixture of silane and hydrogen and led to formation of microcrystalline regions in otherwise amorphous film. The pattern of microcrystalline regions varied with the orientation of the magnetic field. Microscopic study by atomic force microscopy and by micro-Raman spectroscopy revealed that the microcrystalline regions resulted from a higher density of crystalline grain nuclei, increased at the locations where the magnetron effect could be expected. This phenomenon could be used to study the transition between amorphous and microcrystalline growth. Moreover, we suggest it as a kind of 'magnetic lithography' for the preparation of predefined microcrystalline patterns in otherwise amorphous silicon films.

  18. Mechanical design of a high field common coil magnet

    SciTech Connect (OSTI)

    Caspi, S.; Chow, K.; Dietderich, D.; Gourlay, S.; Gupta, R.; McInturff, A.; Millos, G.; Scanlan, R.

    1999-03-18T23:59:59.000Z

    A common coil design for high field 2-in-1 accelerator magnets has been previously presented as a 'conductor-friendly' option for high field magnets applicable for a Very Large Hadron Collider. This paper presents the mechanical design for a 14 tesla 2-in-1 dipole based on the common coil design approach. The magnet will use a high current density Nb{sub 3}Sn conductor. The design addresses mechanical issues particular to the common coil geometry: horizontal support against coil edges, vertical preload on coil faces, end loading and support, and coil stresses and strains. The magnet is the second in a series of racetrack coil magnets that will provide experimental verification of the common coil design approach.

  19. Localized Axion Photon States in a Strong Magnetic Field

    E-Print Network [OSTI]

    E. I. Guendelman

    2008-01-04T23:59:59.000Z

    We consider the axion field and electromagnetic waves with rapid time dependence, coupled to a strong time independent, asymptotically approaching a constant at infinity "mean" magnetic field, which takes into account the back reaction from the axion field and electromagnetic waves with rapid time dependence in a time averaged way. The direction of the self consistent mean field is orthogonal to the common direction of propagation of the axion and electromagnetic waves with rapid time dependence and parallel to the polarization of these electromagnetic waves. Then, there is an effective U(1) symmetry mixing axions and photons. Using the natural complex variables that this U(1) symmetry suggests we find localized planar soliton solutions. These solutions appear to be stable since they produce a different magnetic flux than the state with only a constant magnetic field, which we take as our "ground state". The solitons also have non trivial U(1) charge defined before, different from the uncharged vacuum.

  20. SOLAR MAGNETIC ACTIVITY CYCLES, CORONAL POTENTIAL FIELD MODELS AND ERUPTION RATES

    SciTech Connect (OSTI)

    Petrie, G. J. D. [National Solar Observatory, Tucson, AZ 85719 (United States)

    2013-05-10T23:59:59.000Z

    We study the evolution of the observed photospheric magnetic field and the modeled global coronal magnetic field during the past 3 1/2 solar activity cycles observed since the mid-1970s. We use synoptic magnetograms and extrapolated potential-field models based on longitudinal full-disk photospheric magnetograms from the National Solar Observatory's three magnetographs at Kitt Peak, the Synoptic Optical Long-term Investigations of the Sun vector spectro-magnetograph, the spectro-magnetograph and the 512-channel magnetograph instruments, and from Stanford University's Wilcox Solar Observatory. The associated multipole field components are used to study the dominant length scales and symmetries of the coronal field. Polar field changes are found to be well correlated with active fields over most of the period studied, except between 2003 and 2006 when the active fields did not produce significant polar field changes. Of the axisymmetric multipoles, only the dipole and octupole follow the poles whereas the higher orders follow the activity cycle. All non-axisymmetric multipole strengths are well correlated with the activity cycle. The tilt of the solar dipole is therefore almost entirely due to active-region fields. The axial dipole and octupole are the largest contributors to the global field except while the polar fields are reversing. This influence of the polar fields extends to modulating eruption rates. According to the Computer Aided CME Tracking, Solar Eruptive Event Detection System, and Nobeyama radioheliograph prominence eruption catalogs, the rate of solar eruptions is found to be systematically higher for active years between 2003 and 2012 than for those between 1997 and 2002. This behavior appears to be connected with the weakness of the late-cycle 23 polar fields as suggested by Luhmann. We see evidence that the process of cycle 24 field reversal is well advanced at both poles.

  1. Apparatus for storing high magnetic fields having reduced mechanical forces and reduced magnetic pollution

    DOE Patents [OSTI]

    Prueitt, M.L.; Mueller, F.M.; Smith, J.L.

    1991-04-09T23:59:59.000Z

    The present invention identifies several configurations of conducting elements capable of storing extremely high magnetic fields for the purpose of energy storage or for other uses, wherein forces experienced by the conducting elements and the magnetic field pollution produced at locations away from the configuration are both significantly reduced over those which are present as a result of the generation of such high fields by currently proposed techniques. It is anticipated that the use of superconducting materials will both permit the attainment of such high fields and further permit such fields to be generated with vastly improved efficiency. 15 figures.

  2. Apparatus for storing high magnetic fields having reduced mechanical forces and reduced magnetic pollution

    DOE Patents [OSTI]

    Prueitt, Melvin L. (Los Alamos, NM); Mueller, Fred M. (Los Alamos, NM); Smith, James L. (Los Alamos, NM)

    1991-01-01T23:59:59.000Z

    The present invention identifies several configurations of conducting elements capable of storing extremely high magnetic fields for the purpose of energy storage or for other uses, wherein forces experienced by the conducting elements and the magnetic field pollution produced at locations away from the configuration are both significantly reduced over those which are present as a result of the generation of such high fields by currently proposed techniques. It is anticipated that the use of superconducting materials will both permit the attainment of such high fields and further permit such fields to be generated with vastly improved efficiency.

  3. ALIGNMENT BETWEEN FLATTENED PROTOSTELLAR INFALL ENVELOPES AND AMBIENT MAGNETIC FIELDS

    SciTech Connect (OSTI)

    Chapman, Nicholas L.; Matthews, Tristan G.; Novak, Giles [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Davidson, Jacqueline A. [School of Physics, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Goldsmith, Paul F. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 264-782, Pasadena, CA 91109 (United States); Houde, Martin [Department of Physics and Astronomy, University of Western Ontario, London, ON (Canada); Kwon, Woojin; Looney, Leslie W. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Li Zhiyun [Astronomy Department, University of Virginia, Charlottesville, VA 22904 (United States); Matthews, Brenda [Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Peng Ruisheng [Caltech Submillimeter Observatory, 111 Nowelo Street, Hilo, HI 96720 (United States); Vaillancourt, John E. [SOFIA Science Center, Universities Space Research Association, NASA Ames Research Center, MS 232-11, Moffett Field, CA 94035-0001 (United States); Volgenau, Nikolaus H. [California Institute of Technology, Owens Valley Radio Observatory, Big Pine, CA 93513 (United States)

    2013-06-20T23:59:59.000Z

    We present 350 {mu}m polarization observations of four low-mass cores containing Class 0 protostars: L483, L1157, L1448-IRS2, and Serp-FIR1. This is the second paper in a larger survey aimed at testing magnetically regulated models for core-collapse. One key prediction of these models is that the mean magnetic field in a core should be aligned with the symmetry axis (minor axis) of the flattened young stellar object inner envelope (aka pseudodisk). Furthermore, the field should exhibit a pinched or hourglass-shaped morphology as gravity drags the field inward toward the central protostar. We combine our results for the four cores with results for three similar cores that were published in the first paper from our survey. An analysis of the 350 {mu}m polarization data for the seven cores yields evidence of a positive correlation between mean field direction and pseudodisk symmetry axis. Our rough estimate for the probability of obtaining by pure chance a correlation as strong as the one we found is about 5%. In addition, we combine together data for multiple cores to create a source-averaged magnetic field map having improved signal-to-noise ratio, and this map shows good agreement between mean field direction and pseudodisk axis (they are within 15 Degree-Sign ). We also see hints of a magnetic pinch in the source-averaged map. We conclude that core-scale magnetic fields appear to be strong enough to guide gas infall, as predicted by the magnetically regulated models. Finally, we find evidence of a positive correlation between core magnetic field direction and bipolar outflow axis.

  4. The National High Magnetic Field Laboratory

    E-Print Network [OSTI]

    Weston, Ken

    of Contents Table of contents cHaPTeR 1 The Year in Review 6 cHaPTeR 3 Magnets & Materials 44 cHaPTeR 4 User The year in Review cHaPTeR 1 The Year in Review by Gregory Boebinger, MagLab Director 2012: Another

  5. Dynamics of molecular superrotors in external magnetic field

    E-Print Network [OSTI]

    Korobenko, Aleksey

    2015-01-01T23:59:59.000Z

    We excite diatomic oxygen and nitrogen to high rotational states with an optical centrifuge and study their dynamics in external magnetic field. Ion imaging is employed to directly visualize, and follow in time, the rotation plane of molecular superrotors. The two different mechanisms of interaction between the magnetic field and the molecular angular momentum in paramagnetic oxygen and non-magnetic nitrogen lead to the qualitatively different behaviour. In nitrogen, we observe the precession of the molecular angular momentum around the field vector. In oxygen, strong spin-rotation coupling results in faster and richer dynamics, encompassing the splitting of the rotation plane in three separate components. As the centrifuged molecules evolve with no significant dispersion of the molecular wave function, the observed magnetic interaction presents an efficient mechanism for controlling the plane of molecular rotation.

  6. Cyclic behavior of solar inter-network magnetic field

    E-Print Network [OSTI]

    Jin, Chunlan

    2015-01-01T23:59:59.000Z

    Solar inter-network magnetic field is the weakest component of solar magnetism, but contributes most of the solar surface magnetic flux. The study on its origin has been constrained by the inadequate tempo-spatial resolution and sensitivity of polarization observations. With dramatic advances in spatial resolution and detective sensitivity, solar spectro-polarimetry provided by the Solar Optical Telescope aboard Hinode in an interval from solar minimum to maximum of cycle 24 opens an unprecedented opportunity to study the cyclic behavior of solar inter-network magnetic field. More than 1000 Hinode magnetograms observed from 2007 January to 2014 August are selected in the study. It has been found that there is a very slight correlation between sunspot number and magnetic field at the inter-network flux spectrum. From solar minimum to maximum of cycle 24, the flux density of solar inter-network field is invariant, which is 10$\\pm1$ G. The observations suggest that the inter-network magnetic field does not arise...

  7. Quiet Sun internetwork magnetic fields from the inversion of Hinode measurements

    E-Print Network [OSTI]

    D. Orozco Suarez; L. R. Bellot Rubio; J. C. del Toro Iniesta; S. Tsuneta; B. W. Lites; K. Ichimoto; Y. Katsukawa; S. Nagata; T. Shimizu; R. A. Shine; Y. Suematsu; T. D. Tarbell; A. M. Title

    2007-10-07T23:59:59.000Z

    We analyze Fe I 630 nm observations of the quiet Sun at disk center taken with the spectropolarimeter of the Solar Optical Telescope aboard the Hinode satellite. A significant fraction of the scanned area, including granules, turns out to be covered by magnetic fields. We derive field strength and inclination probability density functions from a Milne-Eddington inversion of the observed Stokes profiles. They show that the internetwork consists of very inclined, hG fields. As expected, network areas exhibit a predominance of kG field concentrations. The high spatial resolution of Hinode's spectropolarimetric measurements brings to an agreement the results obtained from the analysis of visible and near-infrared lines.

  8. Magnetic Propulsion of Intense Lithium Streams in a Tokamak Magnetic Field

    SciTech Connect (OSTI)

    Leonid E. Zakharov

    2002-03-13T23:59:59.000Z

    The paper gives the theory of magnetic propulsion of liquid lithium streams and their stability in tokamaks. In the approximation of a thin flowing layer the MHD equations are reduced to one integro-differential equation which takes into account the propulsion effect, viscosity and the drag force due to magnetic pumping and other interactions with the magnetic field. A criterion is obtained for the stabilization of the ''sausage'' instability of the streams by centrifugal force.

  9. Quantum field theory in a magnetic field: From quantum chromodynamics to graphene and Dirac semimetals

    E-Print Network [OSTI]

    Miransky, Vladimir A

    2015-01-01T23:59:59.000Z

    A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chira...

  10. Locked modes and magnetic field errors in MST

    SciTech Connect (OSTI)

    Almagri, A.F.; Assadi, S.; Prager, S.C.; Sarff, J.S.; Kerst, D.W.

    1992-06-01T23:59:59.000Z

    In the MST reversed field pinch magnetic oscillations become stationary (locked) in the lab frame as a result of a process involving interactions between the modes, sawteeth, and field errors. Several helical modes become phase locked to each other to form a rotating localized disturbance, the disturbance locks to an impulsive field error generated at a sawtooth crash, the error fields grow monotonically after locking (perhaps due to an unstable interaction between the modes and field error), and over the tens of milliseconds of growth confinement degrades and the discharge eventually terminates. Field error control has been partially successful in eliminating locking.

  11. Potential formation in a collisionless plasma produced in an open magnetic field in presence of volume negative ion source

    SciTech Connect (OSTI)

    Phukan, Ananya, E-mail: ananya.phukan26@gmail.com; Goswami, K. S.; Bhuyan, P. J. [Centre of Plasma Physics, Institute for Plasma Research Sonapur, Kamrup (M), Assam 782402 (India)

    2014-08-15T23:59:59.000Z

    The electric potential near a wall for a multi-species plasma with volume produced negative ions in presence of axially varying magnetic field is studied following an analytical-numerical approach. A constant negative ion source is assumed throughout the plasma volume, along with finite temperature positive ions and Boltzmann electrons. The particles are assumed to be guided by an open magnetic field that has its maximum at the centre, and field strength decreasing towards the walls. The one dimensional (1D) Poisson equation is derived using an analytical approach, and then solved numerically to study the potential profiles. Effect of (a) negative ion production rate, (b) magnetic field profile, and (c) negative ion temperature on the potential profile has been investigated. A potential peak appears near the wall when the negative ion temperature and density are sufficiently high. Also, the presence of negative ions further decreases the potential in the plasma region for a finite Debye Length (?{sub D})

  12. Magnetic field diffusion modeling of a small enclosed firing system

    SciTech Connect (OSTI)

    Warne, L.K.; Merewether, K.O.

    1996-01-01T23:59:59.000Z

    Intense magnetic fields exist in the immediate vicinity of a lightning strike (and near power lines). Conducting barriers increase the rise time (and thus decrease the rise rate) interior to the barrier, but typically do not prevent penetration of the magnetic field, since the lightning current fall time may be larger than the barrier diffusion time. Thus, substantial energy is present in the interior field, although the degradation of rise rate makes it more difficult to couple into electrical circuits. This report assesses the threat posed by the diffusive magnetic field to interior components and wire loops (where voltages are induced). Analytical and numerical bounding analyses are carried out on a pill box shaped conducting barrier to develop estimates for the worst case magnetic field threats inside the system. Worst case induced voltages and energies are estimated and compared with threshold charge voltages and energies on the output capacitor of the system. Variability of these quantities with respect to design parameters are indicated. The interior magnetic field and induced voltage estimates given in this report can be used as excitations for more detailed interior and component models.

  13. Photon and Axion Splitting in an Inhomogeneous Magnetic Field

    E-Print Network [OSTI]

    E. I. Guendelman

    2008-02-03T23:59:59.000Z

    The axion photon system in an external magnetic field, when the direction of propagation of axions and photons is orthogonal to the direction of the external magnetic field, displays a continuous axion-photon duality symmetry in the limit the axion mass is neglected. The conservation law that follow in this effective 2+1 dimensional theory from this symmetry is obtained. The magnetic field interaction is seen to be equivalent to first order to the interaction of a complex charged field with an external electric potential, where this ficticious "electric potential" is proportional to the external magnetic field. This allows one to solve for the scattering amplitudes using already known scalar QED results. From the scalar QED analog the axion and the photon are symmetric and antisymmetric combinations of particle and antiparticle. If one considers therefore scattering experiments in which the two spatial dimensions of the effective theory are involved non trivially, one observes that both particle and antiparticle components of photons and axions are preferentially scattered in different directions, thus producing the splitting or decomposition of the photon and axion into their particle and antiparticle components in an inhomogeneous magnetic field. This observable in principle effect is of first order in the axion photon coupling, unlike the "light shining through a wall phenomena ", which is second order.

  14. Magnetic Fields of Uranus and Neptune: Metallic Fluid Hydrogen

    E-Print Network [OSTI]

    Nellis, W J

    2015-01-01T23:59:59.000Z

    The magnetic fields of the Ice Giant Planets Uranus and Neptune (U/N) are unique in the solar system. Based on a substantial database measured on Earth for representative planetary fluids at representative dynamic pressures up to 200 GPa (2 Mbar) and a few 1000 K, the complex magnetic fields of U/N are (i) probably made primarily by degenerate metallic fluid H (MFH) at or near the crossover from the H-He envelopes to Ice cores at ~100 GPa (Mbar) pressures and normalized radii of ~90% of the radii of U/N; (ii) because those magnetic fields are made relatively close to the surfaces of U/N, non-dipolar fields can be expected; (iii) the Ice cores are most probably a heterogeneous fluid mixture of H, N, O, C, Fe/Ni and silicate-oxides and their mutual reaction products at high pressures and temperatures; (iv) the shapes of the magnetic fields are probably caused by weak coupling between rotational motions of U/N and convective motions of conducting fluids in dynamos that make those magnetic fields. Ironically, the...

  15. Properties of an axially periodic magnetic field in a betatron

    SciTech Connect (OSTI)

    Zvontsov, A.A.; Filinova, V.A.; Chakhlov, V.L.

    1983-07-01T23:59:59.000Z

    It is shown by solving an equation for the vector potential A (r, z) of the magnetic field that under appropriate conditions the focusing properties of a betatron magnetic field are periodic with respect to the z coordinate. Under these conditions there may be several equilibrium orbits lying in parallel planes z = 0, z = z/sub 01/ xxx, z = mz/sub 01/ in the accelerator. An equation is derived for the distance z/sub 01/ between the equilibrium orbit planes for a given orbit radius r/sub 0/ and field decay exponent n/sub 0/. The operation of such accelerators is described.

  16. Primordial Magnetic Fields from the Post-Inflationary Universe

    E-Print Network [OSTI]

    Takeshi Kobayashi

    2014-05-28T23:59:59.000Z

    We explore cosmological magnetogenesis in the post-inflationary universe, when the inflaton oscillates around its potential minimum and the universe is effectively dominated by cold matter. During this epoch prior to reheating, large-scale magnetic fields can be significantly produced by the cosmological background. By considering magnetogenesis both during and after inflation, we demonstrate that magnetic fields stronger than 10^{-15} G can be generated on Mpc scales without having strong couplings in the theory, or producing too large electric fields that would dominate the universe.

  17. Primordial Magnetic Fields from the Post-Inflationary Universe

    E-Print Network [OSTI]

    Kobayashi, Takeshi

    2014-01-01T23:59:59.000Z

    We explore cosmological magnetogenesis in the post-inflationary universe, when the inflaton oscillates around its potential minimum and the universe is effectively dominated by cold matter. During this epoch prior to reheating, large-scale magnetic fields can be significantly produced by the cosmological background. By considering magnetogenesis both during and after inflation, we demonstrate that magnetic fields stronger than 10^{-15} G can be generated on Mpc scales without having strong couplings in the theory, or producing too large electric fields that would dominate the universe.

  18. Treating Cancer with Strong Magnetic Fields and Ultrasound

    E-Print Network [OSTI]

    Dr. Friedwardt Winterberg

    2009-06-03T23:59:59.000Z

    It is proposed to treat cancer by the combination of a strong magnetic field with intense ultrasound. At the low electrical conductivity of tissue the magnetic field is not frozen into the tissue, and oscillates against the tissue which is brought into rapid oscillation by the ultrasound. As a result, a rapidly oscillating electric field is induced in the tissue, strong enough to disrupt cancer cell replication. Unlike radio frequency waves, which have been proposed for this purpose, ultrasound can be easily focused onto the regions to be treated. This method has the potential for the complete eradication of the tumor.

  19. Simple basis for hydrogenic atoms in magnetic fields

    SciTech Connect (OSTI)

    Gallas, J.A.C.

    1984-01-01T23:59:59.000Z

    A field-dependent hydrogenic basis is used to obtain the evolution of the energy spectrum of atoms in strong (approx.10/sup 8/ G) and uniform magnetic fields. The basis allows results to be derived analytically. Numerical values for the first 13 excited states of hydrogen are found to be in very good agreement with much more elaborate calculations of Smith et al. and of Brandi. In addition, the possibility of having a remnant type of degeneracy in the presence of the magnetic field is investigated.

  20. Magnetic Fields in Quantum Degenerate Systems and in Vacuum

    E-Print Network [OSTI]

    H. Perez Rojas; E. Rodriguez Querts

    2006-12-28T23:59:59.000Z

    We consider self-magnetization of charged and neutral vector bosons bearing a magnetic moment in a gas and in vacuum. For charged vector bosons (W bosons) a divergence of the magnetization in both the medium and the electroweak vacuum occurs for the critical field B=B_{wc}=m_{w}^{2}/e. For B>B_{wc} the system is unstable. This behavior suggests the occurrence of a phase transition at B=B_{c}, where the field is self-consistently maintained. This mechanism actually prevents $B$ from reaching the critical value B_{c}. For virtual neutral vector bosons bearing an anomalous magnetic moment, the ground state has a similar behavior for B=B_{nbc}=m_{nb}^{2}/q . The magnetization in the medium is associated to a Bose-Einstein condensate and we conjecture a similar condensate occurs also in the case of vacuum. The model is applied to virtual electron-positron pairs bosonization in a magnetic field B \\sim B_{pc}\\lesssim 2m_{e}^{2}/e, where m_e is the electron mass. This would lead also to vacuum self-magnetization in QED, where in both cases the symmetry breaking is due to a condensate of quasi-massless particles.

  1. Equilibrium and stability studies of plasmas confined in a dipole magnetic field using magnetic measurements

    E-Print Network [OSTI]

    Karim, Ishtak

    2007-01-01T23:59:59.000Z

    The Levitated Dipole Experiment (LDX) is the first experiment of its kind to use a levitated current ring to confine a plasma in a dipole magnetic field. Unlike most other confinement devices, plasma compressibility ...

  2. Magnetic field re-arrangement after prominence eruption

    SciTech Connect (OSTI)

    Kopp, R.A.; Poletto, G.

    1986-01-01T23:59:59.000Z

    It has long been known that magnetic reconnection plays a fundamental role in a variety of solar events. Although mainly invoked in flare problems, large-scale loops interconnecting active regions, evolving coronal hole boundaries, the solar magnetic cycle itself, provide different evidence of phenomena which involve magnetic reconnection. A further example might be given by the magnetic field rearrangement which occurs after the eruption of a prominence. Since most often a prominence reforms after its disappearance and may be observed at about the same position it occupied before erupting, the magnetic field has to undergo a temporary disruption to relax back, via reconnection, to a configuration similar to the previous one. The above sequence of events is best observable in the case of two-ribbon (2-R) flares but most probably is associated with all filament eruptions. Even if the explanation of the magnetic field rearrangement after 2-R flares in terms of reconnection is generally accepted, the lack of a three-dimensional model capable of describing the field reconfiguration, has prevented, up to now, a thorough analysis of its topology as traced by H..cap alpha../x-ray loops. The purpose of the present work is to present a numerical technique which enables one to predict and visualize the reconnected configuration, at any time t, and therefore allows one to make a significant comparison of observations and model predictions throughout the whole process. 5 refs., 3 figs.

  3. Coil Winding for the Series-Connected Hybrid Magnet Mark D. Bird, National High Magnetic Field Laboratory

    E-Print Network [OSTI]

    Weston, Ken

    Coil Winding for the Series-Connected Hybrid Magnet Mark D. Bird, National High Magnetic Field will produce for MagLab users magnetic fields of 36T featuring unprecedented (1ppm) homogeneity. Winding of the superconducting coil, the largest component of the magnet windings, is well underway. The superconducting coil

  4. Electric power high-voltage transmission lines: Design options, cost, and electric and magnetic field levels

    SciTech Connect (OSTI)

    Stoffel, J.B.; Pentecost, E.D.; Roman, R.D.; Traczyk, P.A.

    1994-11-01T23:59:59.000Z

    This report provides background information about (1) the electric and magnetic fields (EMFs) of high-voltage transmission lines at typical voltages and line configurations and (2) typical transmission line costs to assist on alternatives in environmental documents. EMF strengths at 0 {+-} 200 ft from centerline were calculated for ac overhead lines, and for 345 and 230-kV ac underground line and for a {+-}450-kV dc overhead line. Compacting and height sensitivity factors were computed for the variation in EMFs when line conductors are moved closer or raised. Estimated costs for the lines are presented and discussed so that the impact of using alternative strategies for reducing EMF strengths and the implications of implementing the strategies can be better appreciated.

  5. Memorandum Approval of a Permanenet Variance Regarding Static Magnetic Fields at Brookhaven National Laboratory (Variance 1021)

    Broader source: Energy.gov [DOE]

    Approval of a Permanenet Variance Regarding Static Magnetic Fields at Brookhaven National Laboratory (Variance 1021)

  6. Proposal for study of $\\pi^{-}$ nucleur collisions in nuclear emulsion exposed in a pulsed magnetic field

    E-Print Network [OSTI]

    CERN. Geneva. SPS Experiments Committee

    1980-01-01T23:59:59.000Z

    Proposal for study of $\\pi^{-}$ nucleur collisions in nuclear emulsion exposed in a pulsed magnetic field

  7. Electrostatic waves in carbon nanotubes with an axial magnetic field

    SciTech Connect (OSTI)

    Abdikian, Alireza [Department of Physics, Malayer University, Malayer 65719-95863 (Iran, Islamic Republic of)] [Department of Physics, Malayer University, Malayer 65719-95863 (Iran, Islamic Republic of); Bagheri, Mehran [Laser and Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran 19835-63113 (Iran, Islamic Republic of)] [Laser and Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran 19835-63113 (Iran, Islamic Republic of)

    2013-10-15T23:59:59.000Z

    Based on a linearized hydrodynamic model and within the quasi-static approximation, the dispersion relation of electrostatic waves propagating through single-walled carbon nanotubes subject to an axial magnetic field is theoretically explored. In the classical limit, we obtain two main possible waves which in turn are divided into two branches, a low-frequency acoustical and a high-frequency optical plasmon branch. In the quantum case, we have found that the dispersion relation is substantially modified when the electron wavelength becomes large enough compared to the propagation wavelength of the electrostatic waves in the quantum plasma. We also show that the axial magnetic field manifest itself on the perturbed electron density through the quantum term and gives rise to the propagation of the electrostatic waves within the quantum plasma. As a result, the effect of the magnetic field is pronounced in the plasma dispersion relations in such a way that their curves approach to zero when the magnetic field is weak; and for the strong magnetic field, they asymptotically meet the constant lines.

  8. Potts models with magnetic field: arithmetic, geometry, and computation

    E-Print Network [OSTI]

    Shival Dasu; Matilde Marcolli

    2014-12-26T23:59:59.000Z

    We give a sheaf theoretic interpretation of Potts models with external magnetic field, in terms of constructible sheaves and their Euler characteristics. We show that the polynomial countability question for the hypersurfaces defined by the vanishing of the partition function is affected by changes in the magnetic field: elementary examples suffice to see non-polynomially countable cases that become polynomially countable after a perturbation of the magnetic field. The same recursive formula for the Grothendieck classes, under edge-doubling operations, holds as in the case without magnetic field, but the closed formulae for specific examples like banana graphs differ in the presence of magnetic field. We give examples of computation of the Euler characteristic with compact support, for the set of real zeros, and find a similar exponential growth with the size of the graph. This can be viewed as a measure of topological and algorithmic complexity. We also consider the computational complexity question for evaluations of the polynomial, and show both tractable and NP-hard examples, using dynamic programming.

  9. The Cost of Superconducting Magnets as a Function of Stored Energy and Design Magnetic Induction Times the Field Volume

    SciTech Connect (OSTI)

    Green, Mike; Green, M.A.; Strauss, B.P.

    2007-08-27T23:59:59.000Z

    By various theorems one can relate the capital cost of superconducting magnets to the magnetic energy stored within that magnet. This is particularly true for magnet where the cost is dominated by the structure needed to carry the magnetic forces. One can also relate the cost of the magnet to the product of the magnetic induction and the field volume. The relationship used to estimate the cost the magnet is a function of the type of magnet it is. This paper updates the cost functions given in two papers that were published in the early 1990 s. The costs (escalated to 2007 dollars) of large numbers of LTS magnets are plotted against stored energy and magnetic field time field volume. Escalated costs for magnets built since the early 1990 s are added to the plots.

  10. Magnetic Backgrounds and Noncommutative Field Theory

    E-Print Network [OSTI]

    Richard J. Szabo

    2004-02-09T23:59:59.000Z

    This paper is a rudimentary introduction, geared at non-specialists, to how noncommutative field theories arise in physics and their applications to string theory, particle physics and condensed matter systems.

  11. A MATHEMATICAL MODEL FOR AN HOURGLASS MAGNETIC FIELD

    SciTech Connect (OSTI)

    Ewertowski, Bartek; Basu, Shantanu, E-mail: basu@uwo.ca [Department of Physics and Astronomy, Western University, London, Ontario N6A 3K7 (Canada)] [Department of Physics and Astronomy, Western University, London, Ontario N6A 3K7 (Canada)

    2013-04-10T23:59:59.000Z

    Starting with a mathematical boundary value problem for the magnetic vector potential in an axisymmetric cylindrical coordinate system, we derive a general solution for any arbitrary current distribution using the method of Green's functions. We use this to derive an analytic form for an hourglass magnetic field pattern created by electrical currents that are concentrated near (but not confined within) the equatorial plane of a cylindrical coordinate system. Our solution is not characterized by a cusp at the equatorial plane, as in previous solutions based on a current sheet. The pattern we derive provides a very good fit to hourglass magnetic field patterns emerging from three-dimensional numerical simulations of core formation, and can in principle be used for source-fitting of observed magnetic hourglass patterns.

  12. MAGNET ENGINEERING AND TEST RESULTS OF THE HIGH FIELD MAGNET R AND D PROGRAM AT BNL.

    SciTech Connect (OSTI)

    COZZOLINO,J.; ANERELLA,M.; ESCALLIER,J.; GANETIS,G.; GHOSH,A.; GUPTA,R.; HARRISON,M.; JAIN,A.; MARONE,A.; MURATORE,J.; PARKER,B.; SAMPSON,W.; SOIKA,R.; WANDERER,P.

    2002-08-04T23:59:59.000Z

    The Superconducting Magnet Division at Brookhaven National Laboratory (BNL) has been carrying out design, engineering, and technology development of high performance magnets for future accelerators. High Temperature Superconductors (HTS) play a major role in the BNL vision of a few high performance interaction region (IR) magnets that would be placed in a machine about ten years from now. This paper presents the engineering design of a ''react and wind'' Nb{sub 3}Sn magnet that will provide a 12 Tesla background field on HTS coils. In addition, the coil production tooling as well as the most recent 10-turn R&D coil test results will be discussed.

  13. The measurement and analysis of the magnetic field of a synchrotron light source magnet

    E-Print Network [OSTI]

    Graf, Udo Werner

    1994-01-01T23:59:59.000Z

    section of the magnet shows the symmetric distribution of the coils about the center line of the magnet. The iron yolk which surrounds the conductors is thermally insulated to enhance the efficiency of the cooling system. The entire magnet assembly... of charged particles in a 21 conductor that are exposed to an electric and a magnetic field. The force experienced by these particles is characterized by the Lorentz Equation, F=q(E+vxB) (3) The conductor used for the Hall probe has the shape of a...

  14. Conceptual Design of the 45 T Hybrid Magnet at the Nijmegen High Field Magnet Laboratory

    E-Print Network [OSTI]

    Wiegers, SAJ; Bird, M D; Rook, J; Perenboom, J A A J; Wiegers, S A J; Bonito-Oliva, A; den Ouden, A

    2010-01-01T23:59:59.000Z

    A 45 T Hybrid Magnet System is being developed at the Nijmegen High Field Magnet Laboratory as part of the Nijmegen Center for Advanced Spectroscopy. The 45 T Hybrid Magnet System will be used in combination with far-infra-red light produced by a Free Electron Laser under construction directly adjacent to the High Field Magnet Laboratory. The superconducting outsert magnet will consist of three CICC coils wound on a single coil form, using Nb3Sn strands. A test program for strand and cable qualification is underway. The CICC will carry 13 kA and the coils will produce 12 T on axis field in a 600 mm warm bore. The nominal operating temperature will be 4.5 K maintained with forced-flow supercritical helium. The insert magnet will produce 33 T at 40 kA in a 32 mm bore consuming 20 MW, and will consist of four coils. The insert magnet will be galvanically and mechanically isolated from the outsert magnet. Complete system availability for users is expected in 2014. In this paper we will report on the conceptual de...

  15. Solar nebula magnetic fields recorded in the Semarkona meteorite

    E-Print Network [OSTI]

    Fu, Roger R.; Weiss, Benjamin P.; Lima, Eduardo A.; Harrison, Richard J.; Bai, Xue-Ning; Desch, Steven J.; Ebel, Denton S.; Suavet, Clement; Wang, Huapei; Glenn, David; Le Sage, David; Kasama, Takeshi; Walsworth, Ronald L.; Kuan, Aaron T.

    2014-11-13T23:59:59.000Z

    images of all three vector 492   components of the magnetic field produced by the sample in the plane of NV sensors using 493   optically-detected magnetic resonance (ODMR) spectroscopy. In this technique, described by 494   Le Sage et al. (74...   Figure 1. Dusty olivine-bearing chondrules from the Semarkona meteorite. (A) Optical 224   photomicrograph of chondrule DOC4 showing the location of dusty olivine grains. Image taken 225   in reflected light with crossed polarizers. (B) Annular...

  16. Development of fast cooling pulsed magnets at the Wuhan National High Magnetic Field Center

    SciTech Connect (OSTI)

    Peng, Tao; Sun, Quqin; Zhao, Jianlong; Jiang, Fan; Li, Liang; Xu, Qiang [Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan (China)] [Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan (China); Herlach, Fritz [Department of Physics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)] [Department of Physics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2013-12-15T23:59:59.000Z

    Pulsed magnets with fast cooling channels have been developed at the Wuhan National High Magnetic Field Center. Between the inner and outer sections of a coil wound with a continuous length of CuNb wire, G10 rods with cross section 4 mm × 5 mm were inserted as spacers around the entire circumference, parallel to the coil axis. The free space between adjacent rods is 6 mm. The liquid nitrogen flows freely in the channels between these rods, and in the direction perpendicular to the rods through grooves provided in the rods. For a typical 60 T pulsed magnetic field with pulse duration of 40 ms, the cooling time between subsequent pulses is reduced from 160 min to 35 min. Subsequently, the same technology was applied to a 50 T magnet with 300 ms pulse duration. The cooling time of this magnet was reduced from 480 min to 65 min.

  17. Semiclassical circular strings in AdS{sub 5} and 'long' gauge field strength operators

    SciTech Connect (OSTI)

    Park, I.Y.; Tirziu, A.; Tseytlin, A.A. [Department of Physics, Ohio State University, Columbus, Ohio 43210 (United States)

    2005-06-15T23:59:59.000Z

    We consider circular strings rotating with equal spins S{sub 1}=S{sub 2}=S in two orthogonal planes in AdS{sub 5} and suggest that they may be dual to long gauge-theory operators built out of self-dual components of gauge field strength. As was found in hep-th/0404187, the one-loop anomalous dimensions of the such gauge-theory operators are described by an antiferromagnetic XXX{sub 1} spin chain and scale linearly with length L>>1. We find that in the case of rigid rotating string both the classical energy E{sub 0} and the 1-loop string correction E{sub 1} depend linearly on the spin S (within the stability region of the solution). This supports the identification of the rigid rotating string with the gauge-theory operator corresponding to the maximal-spin (ferromagnetic) state of the XXX{sub 1} spin chain. The energy of more general rotating and pulsating strings also happens to scale linearly with both the spin and the oscillation number. Such solutions should be dual to other lower-spin states of the spin chain, with the antiferromagnetic ground state presumably corresponding to the string pulsating in two planes with no rotation.

  18. COMPLEX SCATTERED RADIATION FIELDS AND MULTIPLE MAGNETIC FIELDS IN THE PROTOSTELLAR CLUSTER IN NGC 2264

    SciTech Connect (OSTI)

    Kwon, Jungmi; Tamura, Motohide; Kandori, Ryo; Kusakabe, Nobuhiko; Hashimoto, Jun; Nakajima, Yasushi; Nakamura, Fumitaka [National Astronomical Observatory of Japan, Tokyo 181-8588 (Japan); Nagayama, Takahiro [Department of Astrophysics, Nagoya University, Nagoya 464-8602 (Japan); Nagata, Tetsuya [Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan); Hough, James H. [Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Herts AL10 9AB (United Kingdom); Werner, Michael W. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Teixeira, Paula S., E-mail: jungmi.kwon@nao.ac.jp [European Southern Observatory, D-85748 Garching bei Muenchen (Germany)

    2011-11-01T23:59:59.000Z

    Near-infrared imaging polarimetry in the J, H, and K{sub s} bands has been carried out for the protostellar cluster region around NGC 2264 IRS 2 in the Monoceros OB1 molecular cloud. Various infrared reflection nebula clusters (IRNCs) associated with NGC 2264 IRS 2 and the IRAS 12 S1 core, as well as local infrared reflection nebulae (IRNe), were detected. The illuminating sources of the IRNe were identified with known or new near- and mid-infrared sources. In addition, 314 point-like sources were detected in all three bands and their aperture polarimetry was studied. Using a color-color diagram, reddened field stars and diskless pre-main-sequence stars were selected to trace the magnetic field (MF) structure of the molecular cloud. The mean polarization position angle of the point-like sources is 81 Degree-Sign {+-} 29 Degree-Sign in the cluster core, and 58 Degree-Sign {+-} 24 Degree-Sign in the perimeter of the cluster core, which is interpreted as the projected direction on the sky of the MF in the observed region of the cloud. The Chandrasekhar-Fermi method gives a rough estimate of the MF strength to be about 100 {mu}G. A comparison with recent numerical simulations of the cluster formation implies that the cloud dynamics is controlled by the relatively strong MF. The local MF direction is well associated with that of CO outflow for IRAS 12 S1 and consistent with that inferred from submillimeter polarimetry. In contrast, the local MF direction runs roughly perpendicular to the Galactic MF direction.

  19. Towards Integrated Design and Modeling of High Field Accelerator Magnets

    SciTech Connect (OSTI)

    Caspi, S.; Ferracin, P.

    2006-06-01T23:59:59.000Z

    The next generation of superconducting accelerator magnets will most likely use a brittle conductor (such as Nb{sub 3}Sn), generate fields around 18 T, handle forces that are 3-4 times higher than in the present LHC dipoles, and store energy that starts to make accelerator magnets look like fusion magnets. To meet the challenge and reduce the complexity, magnet design will have to be more innovative and better integrated. The recent design of several high field superconducting magnets have now benefited from the integration between CAD (e.g. ProE), magnetic analysis tools (e.g. TOSCA) and structural analysis tools (e.g. ANSYS). Not only it is now possible to address complex issues such as stress in magnet ends, but the analysis can be better detailed an extended into new areas previously too difficult to address. Integrated thermal, electrical and structural analysis can be followed from assembly and cool-down through excitation and quench propagation. In this paper we report on the integrated design approach, discuss analysis results and point out areas of future interest.

  20. Observation of Dirac Monopoles in a Synthetic Magnetic Field

    E-Print Network [OSTI]

    M. W. Ray; E. Ruokokoski; S. Kandel; M. Möttönen; D. S. Hall

    2014-08-13T23:59:59.000Z

    Magnetic monopoles --- particles that behave as isolated north or south magnetic poles --- have been the subject of speculation since the first detailed observations of magnetism several hundred years ago. Numerous theoretical investigations and hitherto unsuccessful experimental searches have followed Dirac's 1931 development of a theory of monopoles consistent with both quantum mechanics and the gauge invariance of the electromagnetic field. The existence of even a single Dirac magnetic monopole would have far-reaching physical consequences, most famously explaining the quantization of electric charge. Although analogues of magnetic monopoles have been found in exotic spin-ices and other systems, there has been no direct experimental observation of Dirac monopoles within a medium described by a quantum field, such as superfluid helium-3. Here we demonstrate the controlled creation of Dirac monopoles in the synthetic magnetic field produced by a spinor Bose-Einstein condensate. Monopoles are identified, in both experiments and matching numerical simulations, at the termini of vortex lines within the condensate. By directly imaging such a vortex line, the presence of a monopole may be discerned from the experimental data alone. These real-space images provide conclusive and long-awaited experimental evidence of the existence of Dirac monopoles. Our result provides an unprecedented opportunity to observe and manipulate these quantum-mechanical entities in a controlled environment.

  1. Electric and magnetic fields and field derivatives from lightning stepped leaders and first return strokes measured at distances

    E-Print Network [OSTI]

    Florida, University of

    Electric and magnetic fields and field derivatives from lightning stepped leaders and first return; published 5 September 2008. [1] Using electric and magnetic field and field derivative sensors arrayed over-peak width of the stepped-leader/return-stroke electric field waveform; the stepped-leader electric field

  2. New dynamo pattern revealed by solar helical magnetic fields

    E-Print Network [OSTI]

    Zhang, Hongqi; Pevtsov, A; Gao, Yu; Xu, Haiqing; Sokoloff, D D; Kuzanyan, K

    2009-01-01T23:59:59.000Z

    Previously unobservable mirror asymmetry of the solar magnetic field -- a key ingredient of the dynamo mechanism which is believed to drive the 11-year activity cycle -- has now been measured. This was achieved through systematic monitoring of solar active regions carried out for more than 20 years at observatories in Mees, Huairou, and Mitaka. In this paper we report on detailed analysis of vector magnetic field data, obtained at Huairou Solar Observing Station in China. Electric current helicity (the product of current and magnetic field component in the same direction) was estimated from the data and a latitude-time plot of solar helicity during the last two solar cycles has been produced. We find that like sunspots helicity patterns propagate equatorwards but unlike sunspot polarity helicity in each solar hemisphere does not change sign from cycle to cycle - confirming the theory. There are, however, two significant time-latitudinal domains in each cycle when the sign does briefly invert. Our findings she...

  3. Electron vortex beams in a magnetic field and spin filter

    E-Print Network [OSTI]

    Debashree Chowdhury; Banasri Basu; Pratul Bandyopadhyay

    2015-02-25T23:59:59.000Z

    We investigate the propagation of electron vortex beams in a magnetic field. It is pointed out that when electron vortex beams carrying orbital angular momentum propagate in a magnetic field, the Berry curvature associated with the scalar electron moving in a cyclic path around the vortex line is modified from that in free space. This alters the spin-orbit interaction, which affects the propagation of nonparaxial beams. The electron vortex beams with tilted vortex lead to spin Hall effect in free space. In presence of a magnetic field in time space we have spin filtering such that either positive or negative spin states emerge in spin Hall currents with clustering of spin $\\frac{1}{2}$ states.

  4. Holographic non-Fermi liquid in a background magnetic field

    SciTech Connect (OSTI)

    Basu, Pallab; He Jianyang; Mukherjee, Anindya; Shieh, Hsien-Hang [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, B.C. V6T 1Z1 (Canada)

    2010-08-15T23:59:59.000Z

    We study the effects of a nonzero magnetic field on a class of 2+1 dimensional non-Fermi liquids, recently found in [Hong Liu, John McGreevy, and David Vegh, arXiv:0903.2477.] by considering properties of a Fermionic probe in an extremal AdS{sup 4} black hole background. Introducing a similar fermionic probe in a dyonic AdS{sup 4} black hole geometry, we find that the effect of a magnetic field could be incorporated in a rescaling of the probe fermion's charge. From this simple fact, we observe interesting effects like gradual disappearance of the Fermi surface and quasiparticle peaks at large magnetic fields and changes in other properties of the system. We also find Landau level like structures and oscillatory phenomena similar to the de-Haas-van Alphen effect.

  5. Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field

    SciTech Connect (OSTI)

    Oikawa, Kohei, E-mail: oikawa@ecei.tohoku.ac.jp; Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira [Department of Electrical Engineering, Tohoku University, Sendai 980-8579 (Japan)] [Department of Electrical Engineering, Tohoku University, Sendai 980-8579 (Japan)

    2014-02-15T23:59:59.000Z

    Uniform axial magnetic field of about 70 G is applied to a radiofrequency (rf) hydrogen ion source by arrays of permanent magnets. The plasma density and electron temperature downstream of the source and near the magnetic filter are compared with those in the previously described ion source, where the axial field has been applied by two solenoids. The source is operated at ?350 kHz and above 10 kW rf power with a field-effect-transistor-based invertor power supply in 1.5 Pa hydrogen. The results show that the plasma density of ?10{sup 19} m{sup ?3} near the source exit and ?10{sup 18} m{sup ?3} near the magnetic filter can be obtained, which are higher than those with the solenoids.

  6. Heating of magnetic fluid systems driven by circularly polarized magnetic field

    E-Print Network [OSTI]

    Atalar, Ergin

    . Introduction Hyperthermia, as a treatment of cancer, has recently attracted the attention of many researchers and frequencies. The extent of this issue is examined by Atkinson et al. [4] and it is concluded that the product limitation is nerve stimulation threshold which similarly restricts the field strength and frequency [5

  7. Polarizable vacuum analysis of electric and magnetic fields

    E-Print Network [OSTI]

    Xing-Hao Ye

    2009-08-22T23:59:59.000Z

    The electric and magnetic fields are investigated on the basis of quantum vacuum. The analysis of the electromagnetic energy and force indicates that an electric field is a polarized distribution of the vacuum virtual dipoles, and that a magnetic field in vacuum is a rearrangement of the vacuum polarization. It means that an electromagnetic wave is a successional changing of the vacuum polarization in space. Also, it is found that the average half length of the virtual dipoles around an elementary charge is a=2.8 *10^(-15)m. The result leads to the step distribution of the field energy around an electron, the relation between the fine structure constant and the vacuum polarization distribution, and an extremely high energy density of the electromagnetic field.

  8. Quantum field theory in a magnetic field: From quantum chromodynamics to graphene and Dirac semimetals

    E-Print Network [OSTI]

    Vladimir A. Miransky; Igor A. Shovkovy

    2015-03-02T23:59:59.000Z

    A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chiral magnetic and separation effects, we also review their possible phenomenological implications in heavy-ion collisions and compact stars. We also discuss the application of the magnetic catalysis ideas for the description of the quantum Hall effect in monolayer and bilayer graphene, and conclude that the generalized magnetic catalysis, including both the magnetic catalysis condensates and the quantum Hall ferromagnetic ones, lies at the basis of this phenomenon. We also consider how an external magnetic field affects the underlying physics in a class of three-dimensional quasirelativistic condensed matter systems, Dirac semimetals. While at sufficiently low temperatures and zero density of charge carriers, such semimetals are expected to reveal the regime of the magnetic catalysis, the regime of Weyl semimetals with chiral asymmetry is realized at nonzero density...

  9. Quantum field theory in a magnetic field: From quantum chromodynamics to graphene and Dirac semimetals

    E-Print Network [OSTI]

    Vladimir A. Miransky; Igor A. Shovkovy

    2015-04-10T23:59:59.000Z

    A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chiral magnetic and separation effects, we also review their possible phenomenological implications in heavy-ion collisions and compact stars. We also discuss the application of the magnetic catalysis ideas for the description of the quantum Hall effect in monolayer and bilayer graphene, and conclude that the generalized magnetic catalysis, including both the magnetic catalysis condensates and the quantum Hall ferromagnetic ones, lies at the basis of this phenomenon. We also consider how an external magnetic field affects the underlying physics in a class of three-dimensional quasirelativistic condensed matter systems, Dirac semimetals. While at sufficiently low temperatures and zero density of charge carriers, such semimetals are expected to reveal the regime of the magnetic catalysis, the regime of Weyl semimetals with chiral asymmetry is realized at nonzero density...

  10. A new probe of magnetic fields during high-mass star formation: Zeeman splitting of 6.7 GHz methanol masers

    E-Print Network [OSTI]

    W. H. T. Vlemmings

    2008-04-07T23:59:59.000Z

    Context: The role of magnetic fields during high-mass star formation is a matter of fierce debate, yet only a few direct probes of magnetic field strengths are available. Aims: The magnetic field is detected in a number of massive star-forming regions through polarization observations of 6.7 GHz methanol masers. Although these masers are the most abundant of the maser species occurring during high-mass star formation, most magnetic field measurements in the high-density gas currently come from OH and H2 O maser observations. Methods: The 100-m Effelsberg telescope was used to measure the Zeeman splitting of 6.7 GHz methanol masers for the first time. The observations were performed on a sample of 24 bright northern maser sources. Results: Significant Zeeman splitting is detected in 17 of the sources with an average magnitude of 0.56 m/s . Using the current best estimate of the 6.7 GHz methanol maser Zeeman splitting coefficient and a geometrical correction, this corresponds to an absolute magnetic field strength of 23 mG in the methanol maser region. Conclusions: The magnetic field is dynamically important in the dense maser regions. No clear relation is found with the available OH maser magnetic field measurements. The general sense of direction of the magnetic field is consistent with other Galactic magnetic field measurements, although a few of the masers display a change of direction between different maser features. Due to the abundance of methanol masers, measuring their Zeeman splitting provides the opportunity to construct a comprehensive sample of magnetic fields in high-mass star-forming regions.

  11. Planck intermediate results. XXXV. Probing the role of the magnetic field in the formation of structure in molecular clouds

    E-Print Network [OSTI]

    Ade, P A R; Alves, M I R; Arnaud, M; Arzoumanian, D; Ashdown, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartolo, N; Battaner, E; Benabed, K; Benoît, A; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bock, J J; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Boulanger, F; Bracco, A; Burigana, C; Calabrese, E; Cardoso, J -F; Catalano, A; Chiang, H C; Christensen, P R; Colombo, L P L; Combet, C; Couchot, F; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Dickinson, C; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Falgarone, E; Ferrière, K; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Ghosh, T; Giard, M; Gjerløw, E; González-Nuevo, J; Górski, K M; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Guillet, V; Harrison, D L; Helou, G; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Holmes, W A; Hornstrup, A; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kisner, T S; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Levrier, F; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maino, D; Mandolesi, N; Mangilli, A; Maris, M; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Netterfield, C B; Noviello, F; Novikov, D; Novikov, I; Oppermann, N; Oxborrow, C A; Pagano, L; Pajot, F; Paladini, R; Paoletti, D; Pasian, F; Perotto, L; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Ponthieu, N; Pratt, G W; Prunet, S; Puget, J -L; Rachen, J P; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Rossetti, M; Roudier, G; Rubiño-Martín, J A; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Savini, G; Scott, D; Soler, J D; Stolyarov, V; Sudiwala, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Umana, G; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; Ysard, N; Yvon, D; Zonca, A

    2015-01-01T23:59:59.000Z

    Within ten nearby (d < 450 pc) Gould Belt molecular clouds we evaluate statistically the relative orientation between the magnetic field projected on the plane of sky, inferred from the polarized thermal emission of Galactic dust observed by Planck at 353 GHz, and the gas column density structures, quantified by the gradient of the column density, $N_H$. The relative orientation is evaluated pixel by pixel and analyzed in bins of column density using the novel statistical tool Histogram of Relative Orientations. Within most clouds we find that the relative orientation changes progressively with increasing $N_H$ from preferentially parallel or no preferred orientation to preferentially perpendicular. In simulations of magnetohydrodynamic turbulence in molecular clouds this trend in relative orientation is a signature of Alfv\\'enic or sub-Alfv\\'enic turbulence, implying that the magnetic field is significant for the gas dynamics at the scales probed by Planck. We compare the deduced magnetic field strength w...

  12. Transmit field pattern control for high field magnetic resonance imaging with integrated RF current sources 

    E-Print Network [OSTI]

    Kurpad, Krishna Nagaraj

    2005-11-01T23:59:59.000Z

    The primary design criterion for RF transmit coils for MRI is uniform transverse magnetic (B1) field. Currently, most high frequency transmit coils are designed as periodic, symmetric structures that are resonant at the ...

  13. Electric and Magnetic Fields (EMF) RAPID Engineering Program, Project 7: Development of Field Exposure Models

    SciTech Connect (OSTI)

    Bracken, T.D.; Rankin, R.F.; Wiley, J.A.

    1999-05-01T23:59:59.000Z

    The purpose of this project was to develop a conceptual model for estimating magnetic field (EMF) personal exposure (PE) of individuals or groups and construct a working model using existing data.

  14. Homogenous BSCCO-2212 Round Wires for Very High Field Magnets

    SciTech Connect (OSTI)

    Dr. Scott Campbell

    2012-06-30T23:59:59.000Z

    The performance demands on modern particle accelerators generate a relentless push towards higher field magnets. In turn, advanced high field magnet development places increased demands on superconducting materials. Nb3Sn conductors have been used to achieve 16 T in a prototype dipole magnet and are thought to have the capability for {approx}18 T for accelerator magnets (primarily dipoles but also higher order multipole magnets). However there have been suggestions and proposals for such magnets higher than 20 T. The High Energy Physics Community (HEP) has identified important new physics opportunities that are enabled by extremely high field magnets: 20 to 50 T solenoids for muon cooling in a muon collider (impact: understanding of neutrinos and dark matter); and 20+ T dipoles and quadrupoles for high energy hadron colliders (impact: discovery reach far beyond present). This proposal addresses the latest SBIR solicitation that calls for grant applications that seek to develop new or improved superconducting wire technologies for magnets that operate at a minimum of 12 Tesla (T) field, with increases up to 15 to 20 T sought in the near future (three to five years). The long-term development of accelerator magnets with fields greater than 20 T will require superconducting wires having significantly better high-field properties than those possessed by current Nb{sub 3}Sn or other A15 based wires. Given the existing materials science base for Bi-2212 wire processing, we believe that Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (Bi-2212) round wires can be produced in km-long piece lengths with properties suitable to meet both the near term and long term needs of the HEP community. The key advance will be the translation of this materials science base into a robust, high-yield wire technology. While the processing and application of A15 materials have advanced to a much higher level than those of the copper oxide-based, high T{sub c} (HTS) counterparts, the HTS materials have the very significant advantage of an extremely high H{sub c2}. For this reason, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (Bi-2212, or 2212) in the form of a multifilamentary Ag alloy matrix composite is beginning to attract the interest of the magnet community for future extremely high-field magnets or magnet-insert coils for 4.2K operation. Fig. 1 shows an example of excellent JE (engineering current density) in Bi-2212 round wire at fields up to 45 T, demonstrating the potential for high field applications of this material. For comparison, the Nb{sub 3}Sn wires used in magnets in the 16-18 T range typically perform with J{sub E} in the range 200-500 A/mm{sup 2}; the Bi-2212 wire retains this level of performance to fields at least as high as 45 T, and probably significantly higher. Bi-2212 conductors have in fact been used to generate a 25 T field in a superconducting insert magnet. These two factors- the very high field critical current performance of Bi-2212, and the already demonstrated capability of this material for high field magnets up to 25 T, strongly suggest this material as a leading contender for the next generation high field superconducting (HFS) wire. This potential was recognized by the US Academy of Science's Committee on Opportunities in High Magnetic Field Science. Their report of the same name specifically calls out the high field potential for this material, and suggests that 30 T magnets appear feasible based on the performance of 2212. There are several requirements for HFS conductors. The most obvious is J{sub E} (B, T), the engineering current density at the field and temperature of operation. As shown in Fig. 1, Bi-2212 excels in this regard. Stability requirements for magnets dictate that the effective filament diameter should be less than 30 micrometers, something that Bi-2212 multifilamentary wire can uniquely satisfy among the HFS superconducting wire technologies. Additional requirements include mechanical properties that prevent stress limitation of J{sub E} at the operating conditions, resistive transition index (n-value) suffic

  15. Ultra-low field nuclear magnetic resonance and magnetic resonance imaging to discriminate and identify materials

    DOE Patents [OSTI]

    Kraus, Robert H. (Los Alamos, NM); Matlashov, Andrei N. (Los Alamos, NM); Espy, Michelle A. (Los Alamos, NM); Volegov, Petr L. (Los Alamos, NM)

    2010-03-30T23:59:59.000Z

    An ultra-low magnetic field NMR system can non-invasively examine containers. Database matching techniques can then identify hazardous materials within the containers. Ultra-low field NMR systems are ideal for this purpose because they do not require large powerful magnets and because they can examine materials enclosed in conductive shells such as lead shells. The NMR examination technique can be combined with ultra-low field NMR imaging, where an NMR image is obtained and analyzed to identify target volumes. Spatial sensitivity encoding can also be used to identify target volumes. After the target volumes are identified the NMR measurement technique can be used to identify their contents.

  16. On collisional diffusion in a stochastic magnetic field

    SciTech Connect (OSTI)

    Abdullaev, S. S. [Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung - Plasmaphysik, EURATOM Association, 52425 Jülich (Germany)] [Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung - Plasmaphysik, EURATOM Association, 52425 Jülich (Germany)

    2013-08-15T23:59:59.000Z

    The effect of particle collisions on the transport in a stochastic magnetic field in tokamaks is investigated. The model of resonant magnetic perturbations generated by external coils at the plasma edge is used for the stochastic magnetic field. The particle collisions are simulated by a random walk process along the magnetic field lines and the jumps across the field lines at the collision instants. The dependencies of the local diffusion coefficients on the mean free path ?{sub mfp}, the diffusion coefficients of field lines D{sub FL}, and the collisional diffusion coefficients, ?{sub ?} are studied. Based on these numerical data and the heuristic arguments, the empirical formula, D{sub r}=?{sub ?}+v{sub ||}D{sub FL}/(1+L{sub c}/?{sub mfp}), for the local diffusion coefficient is proposed, where L{sub c} is the characteristic length of order of the connection length l{sub c}=?qR{sub 0}, q is the safety factor, R{sub 0} is the major radius. The formula quite well describes the results of numerical simulations. In the limiting cases, the formula describes the Rechester-Rosenbluth and Laval scalings.

  17. Heat pulse propagation in chaotic 3-dimensional magnetic fields

    E-Print Network [OSTI]

    D. del-Castillo-Negrete; D. Blazevski

    2014-09-10T23:59:59.000Z

    Heat pulse propagation in $3$-D chaotic magnetic fields is studied by solving the parallel heat transport equation using a Lagrangian-Green's function (LG) method. The LG method provides an efficient and accurate technique that circumvents limitations of finite elements and finite difference methods. The main two problems addressed are: (i) The dependence of the radial transport on the magnetic field stochasticity (controlled by the amplitude of the perturbation, $\\epsilon$); and (ii) The role of reversed shear configurations on pulse propagation. In all the cases considered there are no magnetic flux surfaces. However, radial transport is observed to depend strongly on $\\epsilon$ due to the presence of high-order magnetic islands and Cantori that act as quasi-transport barriers that preclude the radial penetration of heat pulses within physically relevant time scale. The dependence of the magnetic field connection length, $\\ell_B$, on $\\epsilon$ is studied in detail. The decay rate of the temperature maximum, $\\langle T \\rangle_{max}(t)$, the time delay of the temperature response as function of the radius, $\\tau$, and the radial heat flux $\\langle {{\\bf q}\\cdot {\\hat e}_\\psi} \\rangle$, are also studied as functions of the magnetic field stochasticity and $\\ell_B$. In all cases, the scaling of $\\langle T \\rangle_{max}$ with $t$ transitions from sub-diffusive, $\\langle T \\rangle_{max} \\sim t^{-1/4}$, at short times ($\\chi_\\parallel t 10^5$). A strong dependence on $\\epsilon$ is also observed on $\\tau$ and $\\langle {{\\bf q}\\cdot {\\hat e}_\\psi} \\rangle$. The radial propagation of pulses in fully chaotic fields considerably slows down in the shear reversal region and, as a result, $\\tau$, in reversed shear configurations is an order of magnitude longer than the one in monotonic $q$-profiles.

  18. Formation of magnetic discontinuities through superposition of force-free magnetic fields: Periodic boundaries

    SciTech Connect (OSTI)

    Kumar, Dinesh; Bhattacharyya, R. [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India)] [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India); Smolarkiewicz, P. K. [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)] [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)

    2013-11-15T23:59:59.000Z

    In ideal magnetohydrodynamics characterized by an infinite electrical conductivity, the magnetic flux across an arbitrary fluid surface is conserved in time. The magnetofluid then can be partitioned into contiguous subvolumes of fluid, each of which entraps its own subsystem of magnetic flux. During dynamical evolution of the magnetofluid, these subvolumes press into each other; and in the process, two such subvolumes may come into direct contact while ejecting a third interstitial subvolume. Depending on the orientations of magnetic fields of the two interacting subvolumes, the magnetic field at the common surface of interaction may become discontinuous and a current sheet is formed there. This process of current sheet formation and their subsequent decay is believed to be a plausible mechanism for coronal heating and may also be responsible for various eruptive phenomena at the solar corona. In this work, we explore this theoretical concept through numerical simulations of a viscous, incompressible magnetofluid characterized by infinite electrical conductivity. In particular, we show that if the initial magnetic field is prescribed by superposition of two linear force-free fields with different torsion coefficients, then formation of current sheets are numerically realizable in the neighborhood of magnetic nulls.

  19. Kinetic models of current sheets with a sheared magnetic field

    SciTech Connect (OSTI)

    Mingalev, O. V.; Mingalev, I. V.; Mel'nik, M. N. [Russian Academy of Sciences, Polar Geophysical Institute, Cola Science Center (Russian Federation); Artemyev, A. V.; Malova, H. V.; Popov, V. Yu. [Russian Academy of Sciences, Space Research Institute (Russian Federation); Chao, Shen [Chinese Academy of Sciences, Center for Space Science and Applied Research (China); Zelenyi, L. M. [Russian Academy of Sciences, Space Research Institute (Russian Federation)

    2012-04-15T23:59:59.000Z

    Thin current sheets, whose existence in the Earth's magnetotail is confirmed by numerous spacecraft measurements, are studied analytically and numerically. The thickness of such sheets is on the order of the ion Larmor radius, and the normal component of the magnetic field (B{sub z}) in the sheet is almost constant, while the tangential (B{sub x}) and shear (B{sub y}) components depend on the transverse coordinate z. The current density in the sheet also has two self-consistent components (j{sub x} and j{sub y}, respectively), and the magnetic field lines are deformed and do not lie in a single plane. To study such quasi-one-dimensional current configurations, two kinetic models are used, in particular, a numerical model based on the particle-in-cell method and an analytical model. The calculated results show that two different modes of the self-consistent shear magnetic field B{sub y} and, accordingly, two thin current sheet configurations can exist for the same input parameters. For the mode with an antisymmetric z profile of the B{sub y} component, the magnetic field lines within the sheet are twisted, whereas the profiles of the plasma density, current density component j{sub y}, and magnetic field component B{sub x} differ slightly from those in the case of a shearless magnetic field (B{sub y} = 0). For the symmetric B{sub y} mode, the magnetic field lines lie in a curved surface. In this case, the plasma density in the sheet varies slightly and the current sheet is two times thicker. Analysis of the dependence of the current sheet structure on the flow anisotropy shows that the sheet thickness decreases significantly with decreasing ratio between the thermal and drift plasma velocities, which is caused by the dynamics of quasi-adiabatic ions. It is shown that the results of the analytical and numerical models are in good agreement. The problems of application of these models to describe current sheets at the magnetopause and near magnetic reconnection regions are discussed.

  20. Fielding the magnetically applied pressure-shear technique on the Z accelerator (completion report for MRT 4519).

    SciTech Connect (OSTI)

    Alexander, C. Scott; Haill, Thomas A.; Dalton, Devon Gardner; Rovang, Dean Curtis; Lamppa, Derek C.

    2013-09-01T23:59:59.000Z

    The recently developed Magnetically Applied Pressure-Shear (MAPS) experimental technique to measure material shear strength at high pressures on magneto-hydrodynamic (MHD) drive pulsed power platforms was fielded on August 16, 2013 on shot Z2544 utilizing hardware set A0283A. Several technical and engineering challenges were overcome in the process leading to the attempt to measure the dynamic strength of NNSA Ta at 50 GPa. The MAPS technique relies on the ability to apply an external magnetic field properly aligned and time correlated with the MHD pulse. The load design had to be modified to accommodate the external field coils and additional support was required to manage stresses from the pulsed magnets. Further, this represents the first time transverse velocity interferometry has been applied to diagnose a shot at Z. All subsystems performed well with only minor issues related to the new feed design which can be easily addressed by modifying the current pulse shape. Despite the success of each new component, the experiment failed to measure strength in the samples due to spallation failure, most likely in the diamond anvils. To address this issue, hydrocode simulations are being used to evaluate a modified design using LiF windows to minimize tension in the diamond and prevent spall. Another option to eliminate the diamond material from the experiment is also being investigated.

  1. SQUID-Detected Magnetic Resonance Imaging in MicroteslaFields

    SciTech Connect (OSTI)

    Moessle, Michael; Hatridge, Michael; Clarke, John

    2006-08-14T23:59:59.000Z

    Magnetic resonance imaging (MRI) has developed into a powerful clinical tool for imaging the human body (1). This technique is based on nuclear magnetic resonance (NMR) of protons (2, 3) in a static magnetic field B{sub 0}. An applied radiofrequency pulse causes the protons to precess about B{sub 0} at their Larmor frequency {nu}{sub 0} = ({gamma}/2{pi})B{sub 0}, where {gamma} is the gyromagnetic ratio; {gamma}/2{pi} = 42.58 MHz/tesla. The precessing protons generate an oscillating magnetic field and hence a voltage in a nearby coil that is amplified and recorded. The application of three-dimensional magnetic field gradients specifies a unique magnetic field and thus an NMR frequency in each voxel of the subject, so that with appropriate encoding of the signals one can acquire a complete image (4). Most clinical MRI systems involve magnetic fields generated by superconducting magnets, and the current trend is to higher magnetic fields than the widely used 1.5-T systems (5). Nonetheless, there is ongoing interest in the development of less expensive imagers operating at lower fields. Commercially available 0.2-T systems based on permanent magnets offer both lower cost and a more open access than their higher-field counterparts, at the expense of signal-to-noise-ratio (SNR) and spatial resolution. At the still lower field of 0.03 mT maintained by a conventional, room-temperature solenoid, Connolly and co-workers (6, 7) obtain good spatial resolution and signal-to-noise ratio (SNR) by prepolarizing the protons in a field B{sub p} of 0.3 T. Prepolarization (8) enhances the magnetic moment of an ensemble of protons over that produced by the lower precession field; after the polarizing field is removed, the higher magnetic moment produces a correspondingly larger signal during its precession in B{sub 0}. Using the same method, Stepisnik et al. (9) obtained MR images in the Earth's magnetic field ({approx} 50 {micro}T). Alternatively, one can enhance the signal amplitude in MRI using laser polarized noble gases such as {sup 3}He or {sup 129}Xe (10-12). Hyperpolarized gases were used successfully to image the human lung in fields on the order of several mT (13-15). To overcome the sensitivity loss of Faraday detection at low frequencies, ultrasensitive magnetometers based on the Superconducting QUantum Interference Device (SQUID) (16) are used to detect NMR and MRI signals (17-24). Recently, SQUID-based MRI systems capable of acquiring in vivo images have appeared. For example, in the 10-mT system of Seton et al. (18) signals are coupled to a SQUID via a superconducting tuned circuit, while Clarke and coworkers (22, 25, 26) developed a system at 132 {micro}T with an untuned input circuit coupled to a SQUID. In a quite different approach, atomic magnetometers have been used recently to detect the magnetization (27) and NMR signal (28) of hyperpolarized gases. This technique could potentially be used for low-field MRI in the future. The goal of this review is to summarize the current state-of-the-art of MRI in microtesla fields detected with SQUIDs. The principles of SQUIDs and NMR are briefly reviewed. We show that very narrow NMR linewidths can be achieved in low magnetic fields that are quite inhomogeneous, with illustrative examples from spectroscopy. After describing our ultralow-field MRI system, we present a variety of images. We demonstrate that in microtesla fields the longitudinal relaxation T{sub 1} is much more material dependent than is the case in high fields; this results in a substantial improvement in 'T{sub 1}-weighted contrast imaging'. After outlining the first attempts to combine microtesla NMR with magnetoencephalography (MEG) (29), we conclude with a discussion of future directions.

  2. Collective modes and Kosterlitz-Thouless transition in a magnetic field in the planar Nambu--Jona-Lasino model

    E-Print Network [OSTI]

    Gaoqing Cao; Lianyi He; Pengfei Zhuang

    2014-09-16T23:59:59.000Z

    It is known that a constant magnetic field is a strong catalyst of dynamical chiral symmetry breaking in 2+1 dimensions, leading to generating dynamical fermion mass even at weakest attraction. In this work we investigate the collective modes associated with the dynamical chiral symmetry breaking in a constant magnetic field in the (2+1)-dimensional Nambu--Jona-Lasinio model with continuous U(1) chiral symmetry. We introduce a self-consistent scheme to evaluate the propagators of the collective modes at the leading order in 1/N. The contributions from the vacuum and from the magnetic field are separated such that we can employ the well-established regularization scheme for the case of vanishing magnetic field. The same scheme can be applied to the study of the next-to-leading order correction in 1/N. We show that the sigma mode is always a lightly bound state with its mass being twice the dynamical fermion mass for arbitrary strength of the magnetic field. Since the dynamics of the collective modes is always 2+1 dimensional, the finite temperature transition should be of the Kosterlitz-Thouless (KT) type. We determine the KT transition temperature $T_{\\rm KT}$ as well as the mass melting temperature $T^*$ as a function of the magnetic field. It is found that the pseudogap domain $T_{\\rm KT}catalysis of the KT transition temperature in 2+1 dimensions. The inverse magnetic catalysis behavior is actually the de Haas--van Alphen oscillation induced by the interplay between the magnetic field and the Fermi surface.

  3. Screening magnetic fields by superconductors: A simple model

    SciTech Connect (OSTI)

    Caputo, J.-G., E-mail: caputo@insa-rouen.fr [Laboratoire de Mathématiques, INSA de Rouen, Avenue de l'Université, 76801 Saint-Etienne du Rouvray (France); Gozzelino, L.; Laviano, F.; Ghigo, G.; Gerbaldo, R. [Department of Applied Science and Technology, Politecnico di Torino, 10129, Torino (Italy); Noudem, J.; Thimont, Y.; Bernstein, P. [CRISMAT/LUSAC, Physics Department, Université de Caen (France)

    2013-12-21T23:59:59.000Z

    We introduce a simple approach to evaluate the magnetic field distribution around superconducting samples, based on the London equations; the elementary variable is the vector potential. This procedure has no adjustable parameters, only the sample geometry and the London length, ?, determine the solution. This approach was validated by comparing the induction field calculated to the one measured above MgB{sub 2} disks of different diameters, at 20?K and for applied fields lower than 0.4?T. The model can be applied if the flux line penetration inside the sample can be neglected when calculating the induction field distribution outside the superconductor. We conclude by showing on a cup-shape geometry how one can design a magnetic shield satisfying a specific constraint.

  4. MISALIGNMENT OF MAGNETIC FIELDS AND OUTFLOWS IN PROTOSTELLAR CORES

    SciTech Connect (OSTI)

    Hull, Charles L. H.; Plambeck, Richard L.; Bower, Geoffrey C.; Heiles, Carl; Meredith Hughes, A. [Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720-3411 (United States); Bolatto, Alberto D.; Jameson, Katherine; Mundy, Lee; Pound, Marc W. [Astronomy Department and Laboratory for Millimeter-wave Astronomy, University of Maryland, College Park, MD 20742 (United States); Carpenter, John M.; Lamb, James W.; Pillai, Thushara [Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., MC 249-17, Pasadena, CA 91125 (United States); Crutcher, Richard M.; Hakobian, Nicholas S.; Kwon, Woojin; Looney, Leslie W. [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W Green Street, Urbana, IL 61801 (United States); Fiege, Jason D.; Franzmann, Erica [Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2 (Canada); Houde, Martin [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Matthews, Brenda C., E-mail: chat@astro.berkeley.edu [Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Rd., Victoria, BC V8P 5C2 (Canada); and others

    2013-05-10T23:59:59.000Z

    We present results of {lambda}1.3 mm dust-polarization observations toward 16 nearby, low-mass protostars, mapped with {approx}2.''5 resolution at CARMA. The results show that magnetic fields in protostellar cores on scales of {approx}1000 AU are not tightly aligned with outflows from the protostars. Rather, the data are consistent with scenarios where outflows and magnetic fields are preferentially misaligned (perpendicular), or where they are randomly aligned. If one assumes that outflows emerge along the rotation axes of circumstellar disks, and that the outflows have not disrupted the fields in the surrounding material, then our results imply that the disks are not aligned with the fields in the cores from which they formed.

  5. Dynamics of Mesoscale Magnetic Field in Diffusive Shock Acceleration

    E-Print Network [OSTI]

    P. H. Diamond; M. A. Malkov

    2006-05-15T23:59:59.000Z

    We present a theory for the generation of mesoscale ($kr_{g}\\ll 1$, where $r_{g}$ is the cosmic ray gyroradius) magnetic fields during diffusive shock acceleration. The decay or modulational instability of resonantly excited Alfven waves scattering off ambient density perturbations in the shock environment naturally generates larger scale fields. For a broad spectrum of perturbations, the physical mechanism of energy transfer is random refraction, represented by diffusion of Alfven wave packet in $k-$space. The scattering field can be produced directly by the decay instability or by the Drury instability, a hydrodynamic instability driven by the cosmic ray pressure gradient. This process is of interest to acceleration since it generates waves of longer wavelength, and so enables the confinement and acceleration of higher energy particles. This process also limits the intensity of resonantly generated turbulent magnetic field on $r_{g}$ scales.

  6. MAGNETIC FIELD TOPOLOGY AND THE THERMAL STRUCTURE OF THE CORONA OVER SOLAR ACTIVE REGIONS

    SciTech Connect (OSTI)

    Schrijver, Carolus J.; DeRosa, Marc L.; Title, Alan M., E-mail: schryver@lmsal.co [Lockheed Martin Advanced Technology Center, Palo Alto, CA 94304 (United States)

    2010-08-20T23:59:59.000Z

    Solar extreme ultraviolet (EUV) images of quiescent active-region coronae are characterized by ensembles of bright 1-2 MK loops that fan out from select locations. We investigate the conditions associated with the formation of these persistent, relatively cool, loop fans within and surrounding the otherwise 3-5 MK coronal environment by combining EUV observations of active regions made with TRACE with global source-surface potential-field models based on the full-sphere photospheric field from the assimilation of magnetograms that are obtained by the Michelson Doppler Imager (MDI) on SOHO. We find that in the selected active regions with largely potential-field configurations these fans are associated with (quasi-)separatrix layers (QSLs) within the strong-field regions of magnetic plage. Based on the empirical evidence, we argue that persistent active-region cool-loop fans are primarily related to the pronounced change in connectivity across a QSL to widely separated clusters of magnetic flux, and confirm earlier work that suggested that neither a change in loop length nor in base field strengths across such topological features are of prime importance to the formation of the cool-loop fans. We discuss the hypothesis that a change in the distribution of coronal heating with height may be involved in the phenomenon of relatively cool coronal loop fans in quiescent active regions.

  7. Nuclear magnetic resonances in weak fields

    E-Print Network [OSTI]

    Mitchell, Richard Warren

    1953-01-01T23:59:59.000Z

    ' The snalInr 30. voltages necessary in this case would allow the use of parallel banks of batteries, which should increase the stability of the cux xwnt. Lf batteries are used as a ycwsr source, no. 6 wire should be a convenient siss for prodcci...&g fields uy to 106 gauss in a sole noid of the dinensions used here. Pour banks of batterissx each bank containing five batteries in serissx should pxxxvide ~te stabili RIGDIILATTOM FXELUi 'Ae two wain difficulties with the pxesent nodulation scheme...

  8. Ground-state magnetic phase diagram of bow-tie graphene nanoflakes in external magnetic field

    SciTech Connect (OSTI)

    Sza?owski, Karol, E-mail: kszalowski@uni.lodz.pl, E-mail: kszalowski@wp.pl [Department of Solid State Physics, Faculty of Physics and Applied Informatics, University of ?ód?, ul. Pomorska 149/153, 90-236 ?ód? (Poland)

    2013-12-28T23:59:59.000Z

    The magnetic phase diagram of a ground state is studied theoretically for graphene nanoflakes of bow-tie shape and various sizes in external in-plane magnetic field. The tight-binding Hamiltonian supplemented with Hubbard term is used to model the electronic structure of the systems in question. The existence of the antiferromagnetic phase with magnetic moments localized at the sides of the bow-tie is found for low field and a field-induced spin-flip transition to ferromagnetic state is predicted to occur in charge-undoped structures. For small nanoflake doped with a single charge carrier, the low-field phase is ferrimagnetic and a metamagnetic transition to ferromagnetic ordering can be forced by the field. The critical field is found to decrease with increasing size of the nanoflake. The influence of diagonal and off-diagonal disorder on the mentioned magnetic properties is studied. The effect of off-diagonal disorder is found to be more important than that of diagonal disorder, leading to significantly widened distribution of critical fields for disordered population of nanoflakes.

  9. Plasma Equilibrium in a Magnetic Field with Stochastic Regions

    SciTech Connect (OSTI)

    J.A. Krommes and Allan H. Reiman

    2009-04-23T23:59:59.000Z

    The nature of plasma equilibrium in a magnetic field with stochastic regions is examined. It is shown that the magnetic differential equation that determines the equilibrium Pfirsch-Schluter currents can be cast in a form similar to various nonlinear equations for a turbulent plasma, allowing application of the mathematical methods of statistical turbulence theory. An analytically tractable model, previously studied in the context of resonance-broadening theory, is applied with particular attention paid to the periodicity constraints required in toroidal configurations. It is shown that even a very weak radial diffusion of the magnetic field lines can have a significant effect on the equilibrium in the neighborhood of the rational surfaces, strongly modifying the near-resonant Pfirsch-Schluter currents. Implications for the numerical calculation of 3D equilibria are discussed

  10. Ferrofluid aggregates phase transitions in the planar magnetic field

    E-Print Network [OSTI]

    V. F. Kovalenko; M. V. Petrychuk; B. M. Tanygin; S. I. Shulyma

    2014-04-21T23:59:59.000Z

    The influence of the cyclic heating and cooling on properties of the aggregates (aka "ferrofluid clusters") in a ferrofluid, which made on the basis of magnetite nanoparticles, are investigated. The heating of the ferrofluid layer with such aggregates leads to equalization of the concentration between high- and low-concentrated phases. The temperature of the equalization of the phase concentrations was determined at different values of an external constant magnetic field, which was applied parallel to the layer of the ferrofluid. The temperature of the destruction of a periodic structure of the magnetic aggregates, which were formed during cooling of a homogeneous phase of the ferrofluid, was obtained at the different values of the applied external magnetic field.

  11. Localization of disordered bosons and magnets in random fields

    SciTech Connect (OSTI)

    Yu, Xiaoquan, E-mail: yuxq2008@gmail.com [International School for Advanced Studies (SISSA), via Bonomea 265, 34136 Trieste (Italy) [International School for Advanced Studies (SISSA), via Bonomea 265, 34136 Trieste (Italy); New Zealand Institute for Advanced Study, Centre for Theoretical Chemistry and Physics, Massey University, Auckland 0745 (New Zealand); Müller, Markus, E-mail: markusm@ictp.it [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151 Trieste (Italy)] [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151 Trieste (Italy)

    2013-10-15T23:59:59.000Z

    We study localization properties of disordered bosons and spins in random fields at zero temperature. We focus on two representatives of different symmetry classes, hard-core bosons (XY magnets) and Ising magnets in random transverse fields, and contrast their physical properties. We describe localization properties using a locator expansion on general lattices. For 1d Ising chains, we find non-analytic behavior of the localization length as a function of energy at ?=0, ?{sup ?1}(?)=?{sup ?1}(0)+A|?|{sup ?}, with ? vanishing at criticality. This contrasts with the much smoother behavior predicted for XY magnets. We use these results to approach the ordering transition on Bethe lattices of large connectivity K, which mimic the limit of high dimensionality. In both models, in the paramagnetic phase with uniform disorder, the localization length is found to have a local maximum at ?=0. For the Ising model, we find activated scaling at the phase transition, in agreement with infinite randomness studies. In the Ising model long range order is found to arise due to a delocalization and condensation initiated at ?=0, without a closing mobility gap. We find that Ising systems establish order on much sparser (fractal) subgraphs than XY models. Possible implications of these results for finite-dimensional systems are discussed. -- Highlights: •Study of localization properties of disordered bosons and spins in random fields. •Comparison between XY magnets (hard-core bosons) and Ising magnets. •Analysis of the nature of the magnetic transition in strong quenched disorder. •Ising magnets: activated scaling, no closing mobility gap at the transition. •Ising order emerges on sparser (fractal) support than XY order.

  12. Ohmic Decay of Magnetic Fields due to non-spherical accretion in the Crusts of Neutron Stars

    E-Print Network [OSTI]

    Mikael Sahrling

    1998-04-04T23:59:59.000Z

    We consider magnetic field evolution of neutron stars during polar-cap accretion. The size of the polar cap increases as the field decays, and is set by the last open field line before the accretion disk. Below the polar cap we find the temperature to be so high that electron-phonon scattering dominates the resistivity. Outside the polar cap region, the temperature is such the resistivity is dominated by temperature independent impurity scattering which can be a few orders of magnitude larger than the electron- phonon resistivity. The time-scale for field decay is therefore initially given by impurity scattering dominated resistivity. When the field strength has been reduced to $\\sim 10^8 gauss$ the accretion is spherical and the time scale for field decay is given by the smaller electron-phonon scattering resistivity. The field strength is now reduced rapidly compared to before and this could be a reason for there being no pulsars known with field strengths below $10^8 gauss$. We also investigate the evolution of multipoles at the neutron star surface. We find that contribution from higher-order multipoles are at most 30% to that of the dipole mode.

  13. Mean-field analysis of ground state and low-lying electric dipole strength in $^{22}$C

    E-Print Network [OSTI]

    Tsunenori Inakura; W. Horiuchi; Y. Suzuki; T. Nakatsukasa

    2014-05-30T23:59:59.000Z

    Properties of neutron-rich $^{22}$C are studied using the mean-field approach with Skyrme energy density functionals. Its weak binding and large total reaction cross section, which are suggested by recent experiments, are simulated by modifying the central part of Skyrme potential. Calculating $E1$ strength distribution by using the random-phase approximation, we investigate developments of low-lying electric dipole ($E1$) strength and a contribution of core excitations of $^{20}$C. As the neutron Fermi level approaches the zero energy threshold ($\\varepsilon_F >\\sim -1$ MeV), we find that the low-lying $E1$ strength exceeds the energy-weighted cluster sum rule, which indicates an importance of the core excitations with the $1d_{5/2}$ orbit.

  14. Lesson Summary Students will learn about the magnetic fields of

    E-Print Network [OSTI]

    Mojzsis, Stephen J.

    Lesson Summary Students will learn about the magnetic fields of the Sun and Earth. This activity if they have learned them in another context and you can remind them about those lessons in this activity minutes 1. Read and review the lesson plan 2. Gather required materials 3. Form student teams Exploring

  15. Energy Eigenvalues of Kemmer Equation for a Homogeneous Magnetic Field

    E-Print Network [OSTI]

    A. Havare; K. Sogut

    2002-07-10T23:59:59.000Z

    This article illustrates a completely algebraic method to obtain the energy levels of a massive spin-1 particle moving in a constant magnetic field. In the process to obtain the energy levels the wave function was written by harmonic oscillator solutions.

  16. Universal formulae for thermoelectric transport with magnetic field and disorder

    E-Print Network [OSTI]

    Andrea Amoretti; Daniele Musso

    2015-02-09T23:59:59.000Z

    We obtain explicit expressions for the thermoelectric transport coefficients of a strongly coupled, planar medium in the presence of an orthogonal magnetic field and disorder. The computations are performed within the gauge/gravity framework, however we propose and argue for a possible universal relevance of the results relying on comparisons and extensions of previous hydrodynamical analyses and experimental data.

  17. A linear helicon plasma device with controllable magnetic field gradient

    SciTech Connect (OSTI)

    Barada, Kshitish K.; Chattopadhyay, P. K.; Ghosh, J.; Kumar, Sunil; Saxena, Y. C. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat 382428 (India)

    2012-06-15T23:59:59.000Z

    Current free double layers (CFDLs) are localized potential structures having spatial dimensions - Debye lengths and potential drops of more than local electron temperature across them. CFDLs do not need a current for them to be sustained and hence they differ from the current driven double layers. Helicon antenna produced plasmas in an expanded chamber along with an expanding magnetic field have shown the existence of CFDL near the expansion region. A helicon plasma device has been designed, fabricated, and installed in the Institute for Plasma Research, India to study the role of maximum magnetic field gradient as well as its location with respect to the geometrical expansion region of the chamber in CFDL formation. The special feature of this machine consisting of two chambers of different radii is its capability of producing different magnetic field gradients near the physical boundary between the two chambers either by changing current in one particular coil in the direction opposite to that in other coils and/or by varying the position of this particular coil. Although, the machine is primarily designed for CFDL experiments, it is also capable of carrying out many basic plasma physics experiments such as wave propagation, wave coupling, and plasma instabilities in a varying magnetic field topology. In this paper, we will present the details of the machine construction, its specialties, and some preliminary results about the production and characterization of helicon plasma in this machine.

  18. Massive disk outflows mediated by extreme magnetic fields

    E-Print Network [OSTI]

    Shiber, Sagiv; Soker, Noam

    2015-01-01T23:59:59.000Z

    We argue that magnetic fields amplified within a very high accretion-rate disk around main sequence stars can lead to the formation of massive bipolar outflows that can remove most of the disk's mass and energy. This efficient directional removal of energy and mass allows the high accretion-rate disk to be built. We construct thick disks where the magnetic fields are amplified by an Alpha-Omega dynamo in the disk, bringing the fluctuating components of the magnetic field to be much stronger than the large-scale component. By examining the possible activity of the magnetic fields we conclude that main sequence stars can accrete mass at very high rates, up to 0.01Mo/yr for solar type stars, and up to 1Mo/yr for very massive stars. Such energetic outflows can account for the powering of some eruptive objects, such as merging main sequence stars, major eruptions of luminous blue variables, such as the Great Eruption of Eta Carinae, and other intermediate luminosity optical transients (ILOTs; Red Novae; Red Transi...

  19. Triggering for Magnetic Field Measurements of the LCLS Undulators

    SciTech Connect (OSTI)

    Hacker, Kirsten

    2010-12-13T23:59:59.000Z

    A triggering system for magnetic field measurements of the LCLS undulators has been built with a National Instruments PXI-1002 and a Xylinx FPGA board. The system generates single triggers at specified positions, regardless of encoder sensor jitter about a linear scale.

  20. Constraining Cosmic Magnetic Fields by a Measurement of

    E-Print Network [OSTI]

    Erdmann, Martin

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 7 Energy-Energy-Correlations 51 7.1 Definition of Energy-EnergyConstraining Cosmic Magnetic Fields by a Measurement of Energy-Energy-Correlations with the Pierre Ultra High Energy Cosmic Rays 3 2.1 Cosmic Rays with Energies below 4 Ee

  1. Mathematical Modeling of Magnetic Field Profiles in Superconductors

    E-Print Network [OSTI]

    Wetton, Brian

    Mathematical Modeling of Magnetic Field Profiles in Superconductors Michael Lindstrom, Brian Wetton, Rob Kiefl March 1, 2011 Abstract One of the defining characteristics of a superconductor is the Meiss results. 1 Introduction to the Problem and the Model Superconductors are materials which exhibit a phase

  2. Universal formulae for thermoelectric transport with magnetic field and disorder

    E-Print Network [OSTI]

    Amoretti, Andrea

    2015-01-01T23:59:59.000Z

    We obtain explicit expressions for the thermoelectric transport coefficients of a strongly coupled, planar medium in the presence of an orthogonal magnetic field and disorder. The computations are performed within the gauge/gravity framework, however we propose and argue for a possible universal relevance of the results relying on comparisons and extensions of previous hydrodynamical analyses and experimental data.

  3. Photon-Axion conversions in transversely inhomogeneous magnetic fields

    E-Print Network [OSTI]

    Javier Redondo

    2010-03-01T23:59:59.000Z

    We compute the photon-axion conversion probability in an external magnetic field with a strong transverse gradient in the eikonal approximation for plane waves. We find it typically smaller than a comparable uniform case. Some insights into the phenomenon of photon-axion splitting are given.

  4. Spin flip probability of electron in a uniform magnetic field

    SciTech Connect (OSTI)

    Hammond, Richard T. [Department of Physics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina and Army Research Office, Research Triangle Park, North Carolina 27703 (United States)

    2012-03-19T23:59:59.000Z

    The probability that an electromagnetic wave can flip the spin of an electron is calculated. It is assumed that the electron resides in a uniform magnetic field and interacts with an incoming electromagnetic pulse. The scattering matrix is constructed and the time needed to flip the spin is calculated.

  5. LOCAL STUDY OF ACCRETION DISKS WITH A STRONG VERTICAL MAGNETIC FIELD: MAGNETOROTATIONAL INSTABILITY AND DISK OUTFLOW

    SciTech Connect (OSTI)

    Bai, Xue-Ning; Stone, James M., E-mail: xbai@cfa.harvard.edu [Department of Astrophysical Sciences, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States)

    2013-04-10T23:59:59.000Z

    We perform three-dimensional, vertically-stratified, local shearing-box ideal MHD simulations of the magnetorotational instability (MRI) that include a net vertical magnetic flux, which is characterized by midplane plasma {beta}{sub 0} (ratio of gas to magnetic pressure). We have considered {beta}{sub 0} = 10{sup 2}, 10{sup 3}, and 10{sup 4}, and in the first two cases the most unstable linear MRI modes are well resolved in the simulations. We find that the behavior of the MRI turbulence strongly depends on {beta}{sub 0}: the radial transport of angular momentum increases with net vertical flux, achieving {alpha} {approx} 0.08 for {beta} = 10{sup 4} and {alpha} {approx}> 1.0 for {beta}{sub 0} = 100, where {alpha} is the height-integrated and mass-weighted Shakura-Sunyaev parameter. A critical value lies at {beta}{sub 0} {approx} 10{sup 3}: for {beta}{sub 0} {approx}> 10{sup 3}, the disk consists of a gas pressure dominated midplane and a magnetically dominated corona. The turbulent strength increases with net flux, and angular momentum transport is dominated by turbulent fluctuations. The magnetic dynamo that leads to cyclic flips of large-scale fields still exists, but becomes more sporadic as net flux increases. For {beta}{sub 0} {approx}< 10{sup 3}, the entire disk becomes magnetically dominated. The turbulent strength saturates, and the magnetic dynamo is fully quenched. Stronger large-scale fields are generated with increasing net flux, which dominates angular momentum transport. A strong outflow is launched from the disk by the magnetocentrifugal mechanism, and the mass flux increases linearly with net vertical flux and shows sign of saturation at {beta}{sub 0} {approx}< 10{sup 2}. However, the outflow is unlikely to be directly connected to a global wind: for {beta}{sub 0} {approx}> 10{sup 3}, the large-scale field has no permanent bending direction due to dynamo activities, while for {beta}{sub 0} {approx}< 10{sup 3}, the outflows from the top and bottom sides of the disk bend towards opposite directions, inconsistent with a physical disk wind geometry. Global simulations are needed to address the fate of the outflow.

  6. Current induced perpendicular-magnetic-anisotropy racetrack memory with magnetic field assistance

    SciTech Connect (OSTI)

    Zhang, Y.; Klein, J.-O.; Chappert, C.; Ravelosona, D. [IEF, University of Paris-Sud, Orsay 91405 (France); UMR8622, CNRS, Orsay 91405 (France); Zhao, W. S., E-mail: weisheng.zhao@u-psud.fr [IEF, University of Paris-Sud, Orsay 91405 (France); UMR8622, CNRS, Orsay 91405 (France); Electronics and Information Engineering School, University of Beihang, Beijing 100191 (China)

    2014-01-20T23:59:59.000Z

    High current density is indispensable to shift domain walls (DWs) in magnetic nanowires, which limits the using of racetrack memory (RM) for low power and high density purposes. In this paper, we present perpendicular-magnetic-anisotropy (PMA) Co/Ni RM with global magnetic field assistance, which lowers the current density for DW motion. By using a compact model of PMA RM and 40?nm design kit, we perform mixed simulation to validate the functionality of this structure and analyze its density potential. Stochastic DW motion behavior has been taken into account and statistical Monte-Carlo simulations are carried out to evaluate its reliability performance.

  7. Development of high temperature superconductors for magnetic field applications

    SciTech Connect (OSTI)

    Larbalestier, D.C.

    1991-12-31T23:59:59.000Z

    The key requirement for magnetic field applications of high temperature superconductor (HTS) materials is to have conductors with high transport critical current density available for magnet builders. After 3 or 4 years of being without any such object, conductor makers have had recent success in producing simple conductor prototypes. These have permitted the construction of simple HTS magnets having self fields exceeding 1 tesla at 4K. Thus the scientific feasibility of making powerful HTS magnets has been demonstrated. Attention to the technological aspects of making HTS conductors for magnets with strong flux pinning and reduced superconducting granularity is now sensible and attractive. However, extrinsic defects such as filament sausaging, cracking, misaligned grains and other perturbation to long range current flow must be controlled at a low level if the benefit of intrinsic improvements to the critical current density is to be maintained in the conductor form. Due to the great complexity of the HTS materials, there is sometimes confusion as to whether a given sample has an intrinsically or extrinsically limited critical current density. Systematic microstructure variation experiments and resistive transition analysis are shown to be particularly helpful in this phase of conductor development.

  8. Noninvasive valve monitor using constant magnetic and/or DC electromagnetic field

    DOE Patents [OSTI]

    Casada, Donald A. (Knoxville, TN); Haynes, Howard D. (Knoxville, TN)

    1993-01-01T23:59:59.000Z

    One or more sources of steady magnetic field are carefully located on the outside of a valve body. The constant magnetic field is transmitted into the valve body and valve internals. A magnetic field detector carefully located on the outside of the valve body detects the intensity of the magnetic field at its location. As the position of a valve internal part is changed, there is an alteration in the magnetic field in the valve, and a consequent change in the detected magnetic field. Changes in the detected signal provide an indication of the position and motion of the valve internals.

  9. Apparatus for unilateral generation of a homogeneous magnetic field

    DOE Patents [OSTI]

    Fukushima, E.; Rath, A.R.; Roeder, S.B.W.

    1984-05-01T23:59:59.000Z

    An apparatus for unilaterally producing a substantially homogeneous magnetic field. The apparatus includes two circular electromagnet coils, a small coil and a large coil, which are coaxial with one another and which are separated by a distance equal to one-half the difference in the radius of the two coils. By appropriate selection of electrical currents, which are passed through the coils in opposite directions, a region of homogeneous magnetic field is formed. This region is centered on the common axis of the two coils, at a point on the axis which is at a distance from the small coil equal to one-half the radius of the small coil, and which is on the opposite side of the small coil from the large coil. The apparatus has particular application in the field of diagnostic medical NMR and other NMR applications.

  10. Apparatus for unilateral generation of a homogeneous magnetic field

    DOE Patents [OSTI]

    Fukushima, Eiichi (Los Alamos, NM); Rath, Alan R. (San Diego, CA); Roeder, Stephen B. W. (La Mesa, CA)

    1988-01-01T23:59:59.000Z

    An apparatus for unilaterally producing a substantially homogeneous magnetic field. The apparatus includes two circular electromagnet coils, a small coil and a large coil, which are coaxial with one another and which are separated by a distance equal to one-half the difference in the radius of the two coils. By appropriate selection of electrical currents, which are passed through the coil in opposite directions, a region of homogeneous magnetic field is formed. This region is centered on the common axis of the two coils, at a point on the axis which is at a distance from the small coil equal to one-half the radius of the small coil, and which is on the opposite side of the small coil from the large coil. The apparatus has particular application in the field of diagnostic medical NMR and other NMR applications.

  11. Anisotropies in magnetic field evolution and local Lyapunov exponents

    SciTech Connect (OSTI)

    Tang, X.Z.; Boozer, A.H.

    2000-01-13T23:59:59.000Z

    The natural occurrence of small scale structures and the extreme anisotropy in the evolution of a magnetic field embedded in a conducting flow is interpreted in terms of the properties of the local Lyapunov exponents along the various local characteristic (un)stable directions for the Lagrangian flow trajectories. The local Lyapunov exponents and the characteristic directions are functions of Lagrangian coordinates and time, which are completely determined once the flow field is specified. The characteristic directions that are associated with the spatial anisotropy of the problem, are prescribed in both Lagrangian and Eulerian frames. Coordinate transformation techniques are employed to relate the spatial distributions of the magnetic field, the induced current density, and the Lorentz force, which are usually followed in Eulerian frame, to those of the local Lyapunov exponents, which are naturally defined in Lagrangian coordinates.

  12. Anisotropies in magnetic field evolution and local Lyapunov exponents

    SciTech Connect (OSTI)

    Tang, X. Z. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Boozer, A. H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)] [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

    2000-04-01T23:59:59.000Z

    The natural occurrence of small scale structures and the extreme anisotropy in the evolution of a magnetic field embedded in a conducting flow is interpreted in terms of the properties of the local Lyapunov exponents along the various local characteristic (un)stable directions for the Lagrangian flow trajectories. The local Lyapunov exponents and the characteristic directions are functions of Lagrangian coordinates and time, which are completely determined once the flow field is specified. The characteristic directions that are associated with the spatial anisotropy of the problem, are prescribed in both Lagrangian and Eulerian frames. Coordinate transformation techniques are employed to relate the spatial distributions of the magnetic field, the induced current density, and the Lorentz force, which are usually followed in Eulerian frame, to those of the local Lyapunov exponents, which are naturally defined in Lagrangian coordinates. (c) 2000 American Institute of Physics.

  13. Revisiting the Rigidly Rotating Magnetosphere model for $\\sigma$ Ori E - II. Magnetic Doppler imaging, arbitrary field RRM, and light variability

    E-Print Network [OSTI]

    Oksala, M E; Krticka, J; Townsend, R H D; Wade, G A; Prvak, M; Mikulasek, Z; Silvester, J; Owocki, S P

    2015-01-01T23:59:59.000Z

    The initial success of the Rigidly Rotating Magnetosphere (RRM) model application to the B2Vp star sigma OriE by Townsend, Owocki & Groote (2005) triggered a renewed era of observational monitoring of this archetypal object. We utilize high-resolution spectropolarimetry and the magnetic Doppler imaging (MDI) technique to simultaneously determine the magnetic configuration, which is predominately dipolar, with a polar strength Bd = 7.3-7.8 kG and a smaller non-axisymmetric quadrupolar contribution, as well as the surface distribution of abundance of He, Fe, C, and Si. We describe a revised RRM model that now accepts an arbitrary surface magnetic field configuration, with the field topology from the MDI models used as input. The resulting synthetic Ha emission and broadband photometric observations generally agree with observations, however, several features are poorly fit. To explore the possibility of a photospheric contribution to the observed photometric variability, the MDI abundance maps were used to ...

  14. Spin Chain in Magnetic Field: Limitations of the Large-N Mean-Field Theory

    DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)

    Wohlfeld, K.; Chen, Cheng-Chien; van Veenendaal, M.; Devereaux, T.P.

    2015-02-01T23:59:59.000Z

    Motivated by the recent success in describing the spin and orbital spectrum of a spin-orbital chain using a large-N mean-field approximation [Phys. Rev. B 91, 165102 (2015)], we apply the same formalism to the case of a spin chain in the external magnetic field. It occurs that in this case, which corresponds to N=2 in the approximation, the large-N mean-field theory cannot qualitatively reproduce the spin excitation spectra at high magnetic fields, which polarize more than 50% of the spins in the magnetic ground state. This, rather counterintuitively, shows that the physics of a spin chain can under some circumstancesmore »be regarded as more complex than the physics of a spin-orbital chain.« less

  15. Rayleigh-Taylor instabilities with sheared magnetic fields

    SciTech Connect (OSTI)

    Ruderman, M. S. [Solar Physics and Space Plasma Research Centre (SP2RC), University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Terradas, J.; Ballester, J. L. [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

    2014-04-20T23:59:59.000Z

    Magnetic Rayleigh-Taylor (MRT) instabilities may play a relevant role in many astrophysical problems. In this work the effect of magnetic shear on the growth rate of the MRT instability is investigated. The eigenmodes of an interface and a slab model under the presence of gravity are analytically calculated assuming that the orientation of the magnetic field changes in the equilibrium, i.e., there is magnetic shear. We solve the linearized magnetohydrodynamic equations in the incompressible regime. We find that the growth rate is bounded under the presence of magnetic shear. We have derived simple analytical expressions for the maximum growth rate, corresponding to the most unstable mode of the system. These expressions provide the explicit dependence of the growth rate on the various equilibrium parameters. For small angles the growth time is linearly proportional to the shear angle, and in this regime the single interface problem and the slab problem tend to the same result. On the contrary, in the limit of large angles and for the interface problem the growth time is essentially independent of the shear angle. In this regime we have also been able to calculate an approximate expression for the growth time for the slab configuration. Magnetic shear can have a strong effect on the growth rates of the instability. As an application of the results found in this paper we have indirectly determined the shear angle in solar prominence threads using their lifetimes and the estimation of the Alfvén speed of the structure.

  16. Tokamak with mechanical compression of toroidal magnetic field

    DOE Patents [OSTI]

    Ohkawa, Tihiro (La Jolla, CA)

    1981-01-01T23:59:59.000Z

    A tokamak apparatus includes a pressure vessel for defining a reservoir and confining liquid therein. A collapsible toroidal liner disposed within the pressure vessel defines a toroidal space within the liner. Liquid metal fills the reservoir outside said liner. A toroidal magnetic field is developed within the toroidal space about the major axis thereof. A toroidal plasma is developed within the toroidal space about the major axis thereof. Pressure is applied to the liquid metal to collapse the liner and reduce the volume of the toroidal space, thereby increasing the toroidal magnetic flux density therein.

  17. Quantum Mechanics with a Momentum-Space Artificial Magnetic Field

    E-Print Network [OSTI]

    Hannah M. Price; Tomoki Ozawa; Iacopo Carusotto

    2014-11-19T23:59:59.000Z

    The Berry curvature is a geometrical property of an energy band which acts as a momentum space magnetic field in the effective Hamiltonian describing single-particle quantum dynamics. We show how this perspective may be exploited to study systems directly relevant to ultracold gases and photonics. Given the exchanged roles of momentum and position, we demonstrate that the global topology of momentum space is crucially important. We propose an experiment to study the Harper-Hofstadter Hamiltonian with a harmonic trap that will illustrate the advantages of this approach and that will also constitute the first realization of magnetism on a torus.

  18. Use of High Magnetic Field to Control Microstructural Evolution in Metallic and Magnetic Materials

    SciTech Connect (OSTI)

    Ludtka, G.M.; Mackiewicz- Ludtka, G.; Wilgen, J.B.; Kisner, R.A.

    2010-06-27T23:59:59.000Z

    The Amendment 1, referred to as Phase 2, to the original CRADA NFE-06-00414 added tasks 3 through 7 to the original statement of work that had two main tasks that were successfully accomplished in Phase 1 of this project. In this Phase 2 CRADA extension, extensive research and development activities were conducted using high magnetic field processing effects for the purpose of manipulating microstructure in the SAE 5160 steel to refine grain size isothermally and to develop nanocrystalline spacing pearlite during continuous cooling, and to enhance the formability/forgability of the non-ferrous precipitation hardening magnesium alloy AZ90 by applying a high magnetic field during deformation processing to investigate potential magnetoplasticity in this material. Significant experimental issues (especially non-isothermal conditions evolving upon insertion of an isothermal sample in the high magnetic field) were encountered in the isothermal phase transformation reversal experiments (Task 4) that later were determined to be due to various condensed matter physics phenomenon such as the magnetocaloric (MCE) effect that occurs in the vicinity of a materials Curie temperature. Similarly the experimental deformation rig had components for monitoring deformation/strain (Task 3) that were susceptible to the high magnetic field of the ORNL Thermomagnetic Processing facility 9-T superconducting magnet that caused electronic components to fail or record erroneous (very noisy) signals. Limited experiments on developing nanocrystalline spacing pearlite were not sufficient to elucidate the impact of high magnetic field processing on the final pearlite spacing since significant statistical evaluation of many pearlite colonies would need to be done to be conclusive. Since extensive effort was devoted to resolving issues for Tasks 3 and 7, only results for these focused activities are included in this final CRADA report along with those for Task 7 (described in the Objectives Section of this report).

  19. Formation of Moving Magnetic Features and Penumbral Magnetic Fields with Hinode/SOT

    E-Print Network [OSTI]

    Masahito Kubo; Kiyoshi Ichimoto; Toshifumi Shimizu; Saku Tsuneta; Yoshinori Suematsu; Yukio Katsukawa; Shin'ichi Nagata; Theodore D Tarbell; Richard A Shine; Alan M Title; Zoe A Frank; Bruce W Lites; David Elmore

    2007-09-12T23:59:59.000Z

    Vector magnetic fields of moving magnetic features (MMFs) are well observed with the Solar Optical Telescope (SOT) aboard the Hinode satellite. We focus on the evolution of three MMFs with the SOT in this study. We found that an MMF having relatively vertical fields with polarity same as the sunspot is detached from the penumbra around the granules appeared in the outer penumbra. This suggests that granular motions in the outer penumbra are responsible for the disintegration of the sunspot. Two MMFs with polarity opposite to the sunspot are located around the outer edge of horizontal fields extending from the penumbra. This is an evidence that the MMFs with polarity opposite to the sunspot are prolongation of penumbral horizontal fields. Radshifts larger than sonic velocity in the photosphere are detected for some of the MMFs with polarity opposite to the sunspot.

  20. Magnetic Reconnection in the MST Reversed Field Pinch

    SciTech Connect (OSTI)

    Crocker, N.E.

    2001-06-01T23:59:59.000Z

    Magnetic field line reconnection is a process whereby magnetic field lines which are otherwise topologically preserved by, and frozen into, a plasma can break and reconnect to form field lines with different topologies. It plays a significant role in a wide variety of plasmas, including stellar, space and laboratory plasmas. The focus of this dissertation is the underlying dynamics of reconnection in one particular kind of laboratory plasma: the Reversed Field Pinch (RFP). Specifically, this dissertation reports measurements, made using a pair of insertable diagnostics in conjunction with arrays of magnetic sensing coils positioned near the plasma surface, of the spatial structure of the magnetic and parallel current density fluctuations associated with reconnection in the edge of MST. At least 4 significant results are obtained form such measurements. First we observe direct evidence of reconnection which takes the form of tearing modes in an RFP. Specifically we measure a (radial) magnetic field fluctuation that causes reconnection in the so-called reversal surface, or q = 0 surface, in the edge of MST. Notably this evidence of reconnection at the reversal surface is the first of its kind in an RFP. Second, we measure the radial width of the associated current sheet, or fluctuation in the component of the current density parallel to the equilibrium magnetic field. Such current sheets are a characteristic feature of the reconnection process but their radial widths are sensitive to the specific effects that allow reconnection to occur sometimes call non-ideal effects because reconnection is forbidden by ideal MHD. We compare the observed width to those expected from models of reconnection that incorporate different non-ideal effects in Ohm's law. In particular we see that the observed width is significantly larger than those expected form resistivity in the context of linearly unstable tearing modes and electron inertia. It is a factor of a few larger than the width expected form the electron pressure gradient effect. It is significantly smaller than the width expected from the ion inertia, but this width is not expected to be relevant to a strongly magnetized plasma such as an RFP. Notably it is comparable to the width of the magnetic island produced by the associated tearing mode. This is consistent with expectation for saturated or fully developed resistive tearing modes such as MST is believed to exhibit. It is also consistent with the broadening of a smaller width current sheet through current transport due to parallel streaming of charge carriers (along the field lines of the associated island). Third we obtain estimates of the radial charge transport or radial current density due to streaming charge of carriers along magnetic field lines that results from reconnection in the edge of MST. We find that in contradiction with the theoretical expectation for isolated tearing modes it is non-vanishing and in fact large enough to imply both the existence of another charge transport mechanism to maintain charge neutrality and a significant difference in the radial ion and electron particle fluxes due to parallel streaming of particles. Fourth we interpret the flux surface average of j and b as a J x B force density on the plasma. We observe in agreement with theory and observation for interacting tearing modes in an RFP that the radial structure of the force density during sawtooth crashes is such as to flatten the equilibrium radial gradient in toroidal velocity. We observe also that it is sufficiently large as to imply the existence of other force densities on the plasma.

  1. Structure and Dynamics of the Sun's Open Magnetic Field

    E-Print Network [OSTI]

    S. K. Antiochos; C. R. DeVore; J. T. Karpen; Z. Mikic

    2007-05-30T23:59:59.000Z

    The solar magnetic field is the primary agent that drives solar activity and couples the Sun to the Heliosphere. Although the details of this coupling depend on the quantitative properties of the field, many important aspects of the corona - solar wind connection can be understood by considering only the general topological properties of those regions on the Sun where the field extends from the photosphere out to interplanetary space, the so-called open field regions that are usually observed as coronal holes. From the simple assumptions that underlie the standard quasi-steady corona-wind theoretical models, and that are likely to hold for the Sun, as well, we derive two conjectures on the possible structure and dynamics of coronal holes: (1) Coronal holes are unique in that every unipolar region on the photosphere can contain at most one coronal hole. (2) Coronal holes of nested polarity regions must themselves be nested. Magnetic reconnection plays the central role in enforcing these constraints on the field topology. From these conjectures we derive additional properties for the topology of open field regions, and propose several observational predictions for both the slowly varying and transient corona/solar wind.

  2. Magnetic Field Created by Tile Permanent R. Ravaud, G. Lemarquand, V. Lemarquand

    E-Print Network [OSTI]

    Boyer, Edmond

    , the most common shape for a permanent magnet in electrical engineering11 is certainly the tile, which can1 Magnetic Field Created by Tile Permanent Magnets R. Ravaud, G. Lemarquand, V. Lemarquand Abstract1 This paper presents the analytical calculation of the three components of the magnetic field

  3. Transport of Magnetic Fields in Convective, Accreting Supernova Cores

    E-Print Network [OSTI]

    Christopher Thompson; Norman Murray

    2001-05-24T23:59:59.000Z

    We consider the amplification and transport of a magnetic field in the collapsed core of a massive star, including both the region between the neutrinosphere and the shock, and the central, opaque core. An analytical argument explains why rapid convective overturns persist within a newly formed neutron star for roughly 10 seconds ($> 10^3$ overturns), consistent with recent numerical models. A dynamical balance between turbulent and magnetic stresses within this convective layer corresponds to flux densities in excess of $10^{15}$G. Material accreting onto the core is heated by neutrinos and also becomes strongly convective. We compare the expected magnetic stresses in this convective `gain layer' with those deep inside the neutron core. Buoyant motions of magnetized fluid are greatly aided by the intense neutrino flux. We calculate the transport rate through a medium containing free neutrons protons, and electrons, in the limiting cases of degenerate or non-degenerate nucleons. Fields stronger than $\\sim 10^{13}$ G are able to rise through the outer degenerate layers of the neutron core during the last stages of Kelvin-Helmholtz cooling (up to 10 seconds post-collapse), even though these layers have become stable to convection. We also find the equilibrium shape of a thin magnetic flux rope in the dense hydrostatic atmosphere of the neutron star, along with the critical separation of the footpoints above which the rope undergoes unlimited expansion against gravity. The implications of these results for pulsar magnetism are summarized, and applied to the case of late fallback over the first 1,000-10,000 s of the life of a neutron star

  4. Charge-Transfer Induced Magnetic Field Effects of Nano-Carbon Heterojunctions

    E-Print Network [OSTI]

    Qin, Wei; Gong, Maogang; Shastry, Tejas; Hersam, Mark C.; Ren, Shenqiang

    2014-08-22T23:59:59.000Z

    Room temperature magnetic field effects have not been definitively observed in either single-walled carbon nanotubes (SWCNTs) or C60 under a small magnetic field due to their weak hyperfine interaction and slight difference of g-factor between...

  5. Double Barriers and Magnetic Field in Bilayer Graphene

    E-Print Network [OSTI]

    Ilham Redouani; Ahmed Jellal; Hocine Bahlouli

    2015-05-21T23:59:59.000Z

    We study the transmission probability in an AB-stacked bilayer graphene of Dirac fermions scattered by a double barrier structure in the presence of a magnetic field. We take into account the full four bands of the energy spectrum and use the boundary conditions to determine the transmission probability. Our numerical results show that for energies higher than the interlayer coupling, four ways for transmission probabilities are possible while for energies less than the height of the barrier, Dirac fermions exhibits transmission resonances and only one transmission channel is available. We show that, for AB-stacked bilayer graphene, there is no Klein tunneling at normal incident. We find that the transmission displays sharp peaks inside the transmission gap around the Dirac point within the barrier regions while they are absent around the Dirac point in the well region. The effect of the magnetic field, interlayer electrostatic potential and various barrier geometry parameters on the transmission probabilities are also discussed.

  6. Circuitry, systems and methods for detecting magnetic fields

    DOE Patents [OSTI]

    Kotter, Dale K. (Shelley, ID) [Shelley, ID; Spencer, David F. (Idaho Falls, ID) [Idaho Falls, ID; Roybal, Lyle G. (Idaho Falls, ID) [Idaho Falls, ID; Rohrbaugh, David T. (Idaho Falls, ID) [Idaho Falls, ID

    2010-09-14T23:59:59.000Z

    Circuitry for detecting magnetic fields includes a first magnetoresistive sensor and a second magnetoresistive sensor configured to form a gradiometer. The circuitry includes a digital signal processor and a first feedback loop coupled between the first magnetoresistive sensor and the digital signal processor. A second feedback loop which is discrete from the first feedback loop is coupled between the second magnetoresistive sensor and the digital signal processor.

  7. NEUTRINO SPIN AND FLAVOUR CONVERSION AND OSCILLATIONS IN MAGNETIC FIELD

    E-Print Network [OSTI]

    A. M. Egorov; G. G. Likhachev; A. I. Studenikin

    1995-06-09T23:59:59.000Z

    A review of the neutrino conversion and oscillations among the two neutrino species (active and sterile) induced by strong twisting magnetic field is presented and implications to neutrinos in neutron star, supernova, the Sun and interstellar galactic media are discussed. The ``cross-boundary effect" (CBE) (i.e., a possible conversion of one half of neutrinos of the bunch from active into sterile specie) at the surface of neutron star is also studied for a realistic neutron star structure.

  8. Adiabatic expansion and magnetic fields in AGN jets

    E-Print Network [OSTI]

    A. B. Pushkarev; Y. Y. Kovalev; A. P. Lobanov

    2008-12-25T23:59:59.000Z

    Results of high-resolution simultaneous multi-frequency 8.1-15.4 GHz VLBA polarimetric observations of relativistic jets in active galactic nuclei (the MOJAVE-2 project) are analyzed. We compare characteristics of VLBI features with jet model predictions and test if adiabatic expansion is a dominating mechanism for the evolution of relativistic shocks in parsec-scale AGN jets. We also discuss magnetic field configuration, both predicted by the model and deduced from electric vector position angle measurements.

  9. Conference Summary: The Cosmic Agitator - Magnetic Fields in the Galaxy

    E-Print Network [OSTI]

    T. H. Troland; C. Heiles; A. P. Sarma; G. J. Ferland; R. M. Crutcher; C. L. Brogan

    2008-04-21T23:59:59.000Z

    We present a summary of the conference "The Cosmic Agitator: Magnetic Fields in the Galaxy" held in Lexington KY in 2008 Mar 26-29. The presentation draws primarily from material in the slides prepared for the Conference Summary by one of us (Carl Heiles). Interested readers may navigate to the conference web site given in the paper to view the posted presentations in detail.

  10. Ballistic dynamics of Dirac particles in electro-magnetic fields

    E-Print Network [OSTI]

    Josef Mehringer; Edgardo Stockmeyer

    2014-11-21T23:59:59.000Z

    Investigating properties of two-dimensional Dirac operators coupled to an electric and a magnetic field (perpendicular to the plane) requires in general unbounded (vector-) potentials. If the system has a certain symmetry, the fields can be described by one-dimensional potentials $V$ and $A$. Assuming that $|A|<|V|$ outside some arbitrary large ball, we show that absolutely continuous states of the effective Dirac operators spread ballistically. These results are based on well-known methods in spectral dynamics together with certain new Hilbert-Schmidt bounds. We use Lorentz boosts to derive these new estimates.

  11. Planck 2015 results. XIX. Constraints on primordial magnetic fields

    E-Print Network [OSTI]

    Ade, P A R; Arnaud, M; Arroja, F; Ashdown, M; Aumont, J; Baccigalupi, C; Ballardini, M; Banday, A J; Barreiro, R B; Bartolo, N; Battaner, E; Benabed, K; Benoît, A; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Bucher, M; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Catalano, A; Chamballu, A; Chiang, H C; Chluba, J; Christensen, P R; Church, S; Clements, D L; Colombi, S; Colombo, L P L; Combet, C; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Désert, F -X; Diego, J M; Dolag, K; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Fergusson, J; Finelli, F; Florido, E; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Giard, M; Giraud-Héraud, Y; Gjerløw, E; González-Nuevo, J; Górski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Hansen, F K; Hanson, D; Harrison, D L; Helou, G; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kim, J; Kisner, T S; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lähteenmäki, A; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leahy, J P; Leonardi, R; Lesgourgues, J; Levrier, F; Liguori, M; Lilje, P B; Linden-Vørnle, M; López-Caniego, M; Lubin, P M; Macías-Pérez, J F; Maggio, G; Maino, D; Mandolesi, N; Mangilli, A; Martin, P G; Martínez-González, E; Masi, S; Matarrese, S; Mazzotta, P; McGehee, P; Meinhold, P R; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Mitra, S; Miville-Deschênes, M -A; Molinari, D; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Moss, A; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Natoli, P; Netterfield, C B; Nørgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Oppermann, N; Oxborrow, C A; Paci, F; Pagano, L; Pajot, F; Paoletti, D; Pasian, F; Patanchon, G; Perdereau, O; Perotto, L; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Popa, L; Pratt, G W; Prézeau, G; Prunet, S; Puget, J -L; Rachen, J P; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Rosset, C; Rossetti, M; Roudier, G; Rubiño-Martín, J A; Ruiz-Granados, B; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Savini, G; Scott, D; Seiffert, M D; Shellard, E P S; Shiraishi, M; Spencer, L D; Stolyarov, V; Stompor, R; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Umana, G; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; Yvon, D; Zacchei, A; Zonca, A

    2015-01-01T23:59:59.000Z

    We predict and investigate four types of imprint of a stochastic background of primordial magnetic fields (PMFs) on the cosmic microwave background (CMB) anisotropies: the impact of PMFs on the CMB spectra; the effect on CMB polarization induced by Faraday rotation; magnetically-induced non-Gaussianities; and the magnetically-induced breaking of statistical isotropy. Overall, Planck data constrain the amplitude of PMFs to less than a few nanogauss. In particular, individual limits coming from the analysis of the CMB angular power spectra, using the Planck likelihood, are $B_{1\\,\\mathrm{Mpc}}< 4.4$ nG (where $B_{1\\,\\mathrm{Mpc}}$ is the comoving field amplitude at a scale of 1 Mpc) at 95% confidence level, assuming zero helicity, and $B_{1\\,\\mathrm{Mpc}}< 5.6$ nG when we consider a maximally helical field. For nearly scale-invariant PMFs we obtain $B_{1\\,\\mathrm{Mpc}}<2.1$ nG and $B_{1\\,\\mathrm{Mpc}}<0.7$ nG if the impact of PMFs on the ionization history of the Universe is included in the analysis...

  12. Magnetic field gradients in solar wind plasma and geophysics periods

    E-Print Network [OSTI]

    A. Bershadskii

    2006-11-16T23:59:59.000Z

    Using recent data obtained by Advanced Composition Explorer (ACE) the pumping scale of the magnetic field gradients of the solar wind plasma has been calculated. This pumping scale is found to be equal to 24h $\\pm$ 2h. The ACE spacecraft orbits at the L1 libration point which is a point of Earth-Sun gravitational equilibrium about 1.5 million km from Earth. Since the Earth's magnetosphere extends into the vacuum of space from approximately 80 to 60,000 kilometers on the side toward the Sun the pumping scale cannot be a consequence of the 24h-period of the Earth's rotation. Vise versa, a speculation is suggested that for the very long time of the coexistence of Earth and of the solar wind the weak interaction between the solar wind and Earth could lead to stochastic synchronization between the Earth's rotation and the pumping scale of the solar wind magnetic field gradients. This synchronization could transform an original period of the Earth's rotation to the period close to the pumping scale of the solar wind magnetic field gradients.

  13. How are Forbush decreases related with interplanetary magnetic field enhancements ?

    E-Print Network [OSTI]

    Arunbabu, K P; Dugad, S R; Gupta, S K; Hayashi, Y; Kawakami, S; Mohanty, P K; Oshima, A; Subramanian, P

    2015-01-01T23:59:59.000Z

    Aims. Forbush decrease (FD) is a transient decrease followed by a gradual recovery in the observed galactic cosmic ray intensity. We seek to understand the relationship between the FDs and near-Earth interplanetary magnetic field (IMF) enhancements associated with solar coronal mass ejections (CMEs). Methods. We use muon data at cutoff rigidities ranging from 14 to 24 GV from the GRAPES-3 tracking muon telescope to identify FD events. We select those FD events that have a reasonably clean profile, and magnitude > 0.25%. We use IMF data from ACE/WIND spacecrafts. We look for correlations between the FD profile and that of the one hour averaged IMF. We ask if the diffusion of high energy protons into the large scale magnetic field is the cause of the lag observed between the FD and the IMF. Results. The enhancement of the IMF associated with FDs occurs mainly in the shock-sheath region, and the turbulence level in the magnetic field is also enhanced in this region. The observed FD profiles look remarkably simil...

  14. Electric Fields and Chiral Magnetic Effect in Cu + Au Collisions

    E-Print Network [OSTI]

    Wei-Tian Deng; Xu-Guang Huang

    2015-02-16T23:59:59.000Z

    The non-central Cu + Au collisions can create strong out-of-plane magnetic fields and in-plane electric fields. By using the HIJING model, we study the general properties of the electromagnetic fields in Cu + Au collisions at 200 GeV and their impacts on the charge-dependent two-particle correlator $\\gamma_{q_1q_2}=$ (see main text for definition) which was used for the detection of the chiral magnetic effect (CME). Compared with Au + Au collisions, we find that the in-plane electric fields in Cu + Au collisions can strongly suppress the two-particle correlator or even reverse its sign if the lifetime of the electric fields is long. Combining with the expectation that if $\\gamma_{q_1q_2}$ is induced by elliptic-flow driven effects we would not see such strong suppression or reversion, our results suggest to use Cu + Au collisions to test CME and understand the mechanisms that underlie $\\gamma_{q_1q_2}$.

  15. The influence of a magnetic field on turbulent heat transfer of a high Prandtl number fluid

    SciTech Connect (OSTI)

    Nakaharai, H. [Department of Advanced Energy Engineering Science, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga-kouen 6-1, Kasuga, Fukuoka 816-8580 (Japan); Takeuchi, J.; Morley, N.B.; Abdou, M.A. [Mechanical and Aerospace Engineering Department, University of California, Los Angeles, CA 90095-1597 (United States); Yokomine, T. [Faculty of Energy Engineering Science, Kyushu University, Kasuga-kouen 6-1, Kasuga, Fukuoka 816-8580 (Japan); Kunugi, T. [Department of Nuclear Engineering, Kyoto University, Yoshida, Sakyo, Kyoto 606-8501 (Japan); Satake, S. [Department of Applied Electronics, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)

    2007-10-15T23:59:59.000Z

    The influence of a transverse magnetic field on the local and average heat transfer of an electrically conducting, turbulent fluid flow with high Prandtl number was studied experimentally. The mechanism of heat transfer modification due to magnetic field is considered with aid of available numerical simulation data for turbulent flow field. The influence of the transverse magnetic field on the heat transfer was to suppress the temperature fluctuation and to steepen the mean temperature gradient in near-wall region in the direction parallel to the magnetic field. The mean temperature gradient is not influenced compared to the temperature fluctuation in the direction vertical to the magnetic field. (author)

  16. Strongest non-destructive magnetic field: world record set at 100-tesla level

    E-Print Network [OSTI]

    - 1 - Strongest non-destructive magnetic field: world record set at 100-tesla level March 22, 2012), the scientists achieved a whopping 100.75 tesla--a magnetic field nearly 100 times more powerful than a junkyard and insulators. The 100-tesla level is roughly equivalent to 2 million times Earth's magnetic field. #12;- 2

  17. Compressing magnetic fields with high-energy lasersa... J. P. Knauer,1,b

    E-Print Network [OSTI]

    Compressing magnetic fields with high-energy lasersa... J. P. Knauer,1,b O. V. Gotchev,1,2,3 P. Y, Rochester, New York 14623, USA 3 Department of Mechanical Engineering, University of Rochester, 250 East-driven magnetic-field compression producing a magnetic field of tens of megaGauss is reported for the first time

  18. Temperature compensated and self-calibrated current sensor using reference magnetic field

    DOE Patents [OSTI]

    Yakymyshyn, Christopher Paul (Seminole, FL); Brubaker, Michael Allen (Loveland, CO); Yakymyshyn, Pamela Jane (Seminole, FL)

    2007-10-09T23:59:59.000Z

    A method is described to provide temperature compensation and self-calibration of a current sensor based on a plurality of magnetic field sensors positioned around a current carrying conductor. A reference magnetic field generated within the current sensor housing is detected by the magnetic field sensors and is used to correct variations in the output signal due to temperature variations and aging.

  19. Spectral Mapping of Protein Torsion Angles National High Magnetic Field Laboratory

    E-Print Network [OSTI]

    Weston, Ken

    Spectral Mapping of Protein Torsion Angles National High Magnetic Field Laboratory NMR Spectroscopy spectra. #12;Spectral Mapping of Protein Torsion Angles National High Magnetic Field Laboratory NMR, in recording signals that are dependent on the orientation of the atoms with respect to the magnetic field, we

  20. Limits on guiding center and gyrokinetic plasma models in 3D magnetic fields

    E-Print Network [OSTI]

    D field: magnetic field torsion and coordinate system twisting · GC higher order validity and global, as seen when moving in that direction. ­ Magnetic field torsion ^b · × ^b is the twisting of the field.) ­ Torsion also introduces twisting of the local field-tied orthogonal coordinate sys- tem, R = (^e1)·^e2

  1. Linear metric and temperature fluctuations of a charged plasma in a primordial magnetic field

    E-Print Network [OSTI]

    Haba, Z

    2015-01-01T23:59:59.000Z

    We discuss tensor metric perturbations in a magnetic field around the homogeneous Juttner equilibrium of massless particles in an expanding universe. We solve the Liouville equation and derive the energy-momentum tensor up to linear terms in the metric and in the magnetic field.The term linear in the magnetic field is different from zero if the total charge of the primordial plasma is non-zero. We obtain an analytic formula for temperature fluctuations treating the tensor metric perturbations and the magnetic field as independent random variables. Assuming a cutoff on large momenta of the magnetic spectral function we show that the presence of the magnetic field can discriminate only low multipoles in the multipole expansion of temperature fluctuations. In such a case the term linear in the magnetic field can be more important than the quadratic one (corresponding to the fluctuations of the pure magnetic field).

  2. High-precision description and new properties of a spin-1 particle in a magnetic field

    E-Print Network [OSTI]

    Alexander J. Silenko

    2014-06-09T23:59:59.000Z

    The exact Foldy-Wouthuysen Hamiltonian is derived for a pointlike spin-1 particle with a normal magnetic moment in a nonuniform magnetic field. For a uniform magnetic field, it is exactly separated into terms linear and quadratic in spin. New unexpected properties of a particle with an anomalous magnetic moment are found. Spin projections of a particle moving in a uniform magnetic field are not integer and the tensor polarization is asymmetric in the plane orthogonal to the field. Previously described spin-tensor effects caused by the tensor magnetic polarizability exist not only for nuclei but also for pointlike particles.

  3. Force-free field modeling of twist and braiding-induced magnetic energy in an active-region corona

    SciTech Connect (OSTI)

    Thalmann, J. K. [Institute of Physics/IGAM, University of Graz, Universitätsplatz 5, A-8010 Graz (Austria); Tiwari, S. K.; Wiegelmann, T., E-mail: julia.thalmann@uni-graz.at [Max Plank Institute for Solar System Research, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany)

    2014-01-01T23:59:59.000Z

    The theoretical concept that braided magnetic field lines in the solar corona may dissipate a sufficient amount of energy to account for the brightening observed in the active-region (AR) corona has only recently been substantiated by high-resolution observations. From the analysis of coronal images obtained with the High Resolution Coronal Imager, first observational evidence of the braiding of magnetic field lines was reported by Cirtain et al. (hereafter CG13). We present nonlinear force-free reconstructions of the associated coronal magnetic field based on Solar Dynamics Observatory/Helioseismic and Magnetic Imager vector magnetograms. We deliver estimates of the free magnetic energy associated with a braided coronal structure. Our model results suggest (?100 times) more free energy at the braiding site than analytically estimated by CG13, strengthening the possibility of the AR corona being heated by field line braiding. We were able to appropriately assess the coronal free energy by using vector field measurements and we attribute the lower energy estimate of CG13 to the underestimated (by a factor of 10) azimuthal field strength. We also quantify the increase in the overall twist of a flare-related flux rope that was noted by CG13. From our models we find that the overall twist of the flux rope increased by about half a turn within 12 minutes. Unlike another method to which we compare our results, we evaluate the winding of the flux rope's constituent field lines around each other purely based on their modeled coronal three-dimensional field line geometry. To our knowledge, this is done for the first time here.

  4. HE0241-0155 - Evidence for a large scale homogeneous field in a highly magnetic white dwarf

    E-Print Network [OSTI]

    Dieter Reimers; Stefan Jordan; Norbert Christlieb

    2003-11-04T23:59:59.000Z

    In the course of the Hamburg/ESO survey we have discovered a white dwarf whose spectrum exhibits many similarities with the prototype of magnetic white dwarfs Grw+70$^{\\circ}$8247. In particular several stationary line components indicative for magnetic fields between about 150 and 400 MG are found in both objects. However, the features between 5000 and 5500 \\AA in the spectrum of HE0241-0155 cannot be explained by stationary line components and demand a relatively homogeneous magnetic field with clustering around 200 MG. For this reason a pure dipole model failed to reproduce this spectral region.An offset-dipole configuration led to some improvement in the fit but a good agreement was only possible for a geometry -- described by an expansion into spherical harmonics -- where most of the surface is covered with magnetic field strengths strongly clustered around 200 MG. This may indicate the presence of a large magnetic spot whose presence could be tested with time resolved spectro-polarimetry.

  5. Stellar coronal magnetic fields and star-planet interaction

    E-Print Network [OSTI]

    Lanza, A F

    2009-01-01T23:59:59.000Z

    Evidence of magnetic interaction between late-type stars and close-in giant planets is provided by the observations of stellar hot spots rotating synchronously with the planets and showing an enhancement of chromospheric and X-ray fluxes. We investigate star-planet interaction in the framework of a magnetic field model of a stellar corona, considering the interaction between the coronal field and that of a planetary magnetosphere moving through the corona. The energy budget of the star-planet interaction is discussed assuming that the planet may trigger a release of the energy of the coronal field by decreasing its relative helicity. The observed intermittent character of the star-planet interaction is explained by a topological change of the stellar coronal field, induced by a variation of its relative helicity. The model predicts the formation of many prominence-like structures in the case of highly active stars owing to the accumulation of matter evaporated from the planet inside an azimuthal flux rope in ...

  6. Extra-galactic magnetic fields and the second knee in the cosmic-ray spectrum

    E-Print Network [OSTI]

    Martin Lemoine

    2005-04-04T23:59:59.000Z

    Recent work suggests that the cosmic ray spectrum may be dominated by Galactic sources up to ~10^{17.5} eV, and by an extra-Galactic component beyond, provided this latter cuts off below the transition energy. Here it is shown that this cut-off could be interpreted in this framework as a signature of extra-galactic magnetic fields with equivalent average strength B and coherence length l_c such that B\\sqrt{l_c} ~ 2-3.10^{-10} G.Mpc^{1/2}, assuming l_c flux is suppressed below 10^{17} eV as the diffusive propagation time from the source to the detector becomes larger than the age of the Universe.

  7. Extra-galactic magnetic fields and the second knee in the cosmic-ray spectrum

    E-Print Network [OSTI]

    Lemoine, M

    2004-01-01T23:59:59.000Z

    Recent work suggests that the cosmic ray spectrum may be dominated by Galactic sources up to ~10^{17.5} eV, and by an extra-Galactic component beyond, provided this latter cuts off below the transition energy. Here it is shown that this cut-off could be interpreted as a signature of extra-galactic magnetic fields with equivalent average strength B and coherence length l_c such that B\\sqrt{l_c}~2.10^{-10} G.Mpc^{1/2}, assuming l_c flux is suppressed below 10^{17} eV as the diffusive propagation time from the source to the detector becomes larger than the age of the Universe.

  8. Anisotropic nanostructured magnets by magnetic-field-assisted processing Chuan-bing Rong, Van Vuong Nguyen, and J. Ping Liua

    E-Print Network [OSTI]

    Liu, J. Ping

    . In this paper, we report our recent work in preparing anisotropic bonded magnets consisting of SmCo5 nanocrystalline particles. The work involved synthesis of nanocrystalline hard magnetic SmCo5 particles by ball of the c-axis of the SmCo5 grains upon the magnetic-field-assisted ball milling, while the grain size

  9. Effect of primordial magnetic fields on the ionization history

    E-Print Network [OSTI]

    Chluba, Jens; Finelli, Fabio; Rubino-Martin, Jose-Alberto

    2015-01-01T23:59:59.000Z

    Primordial magnetic fields (PMF) damp at scales smaller than the photon diffusion and free-streaming scale. This leads to heating of ordinary matter (electrons and baryons), which affects both the thermal and ionization history of our Universe. Here, we study the effect of heating due to ambipolar diffusion and decaying magnetic turbulence. We find that changes to the ionization history computed with recfast are significantly overestimated when compared with CosmoRec. The main physical reason for the difference is that the photoionization coefficient has to be evaluated using the radiation temperature rather than the matter temperature. A good agreement with CosmoRec is found after changing this aspect. Using Planck 2013 data and considering only the effect of PMF-induced heating, we find an upper limit on the r.m.s. magnetic field amplitude of B0 < 1.1 nG (95% c.l.) for a stochastic background of PMF with a nearly scale-invariant power spectrum. We also discuss uncertainties related to the approximations ...

  10. Electromagnetic waves reflection, transmission and absorption by graphene - magnetic semiconductor - graphene sandwich-structure in magnetic field: Faraday geometry

    E-Print Network [OSTI]

    Kuzmin, Dmitry A; Shavrov, Vladimir G

    2014-01-01T23:59:59.000Z

    Electrodynamic properties of the graphene - magnetic semiconductor - graphene sandwich-structure have been investigated theoretically with taking into account the dissipation processes. Influence of graphene layers on electromagnetic waves propagation in graphene - semi-infinte magnetic semiconductor and graphene - magnetic semiconductor - graphene sandwich-structure has been analyzed. Frequency and field dependences of the reflectance, transmittance and absorbtance of electromagnetic waves by such structure have been calculated. The size effects associated with the thickness of the structure have been analyzed. The possibility of efficient control of electrodynamic properties of graphene - magnetic semiconductor - graphene sandwich structure by an external magnetic field has been shown.

  11. Effects of chiral imbalance and magnetic field on pion superfluidity and color superconductivity

    E-Print Network [OSTI]

    Cao, Gaoqing

    2015-01-01T23:59:59.000Z

    The effects of chiral imbalance and external magnetic field on pion superfluidity and color superconductivity are investigated in extended Nambu--Jona-Lasinio models. We take Schwinger approach to treat the interaction between charged pion condensate and magnetic field at finite isospin density and include simultaneously the chiral imbalance and magnetic field at finite baryon density. For the superfluidity, the chiral imbalance and magnetic field lead to catalysis and inverse catalysis effects, respectively. For the superconductivity, the chiral imbalance enhances the critical baryon density, and the magnetic field results in a de Haas--van Alphan oscillation on the phase transition line.

  12. Strong magnetic fields and inhomogeneity in the solar corona

    SciTech Connect (OSTI)

    White, S.M.; Kundu, M.R.; Gopalswamy, N. (Maryland Univ., College Park (USA))

    1991-01-01T23:59:59.000Z

    It is shown that fields of 1800 G can exist in the corona based on observations of gyroresonance emission at 15 GHz at coronal temperatures. The strong fields occur in a small source radiating in the extraordinary (x) mode over the penumbra of a large symmetric sunspot. The optically-thin ordinary mode emission from the region shows a nearby peak at only 36,000 K which may be due to a sunspot plume, and a hole over the umbra consistent with the expected low-density material there. The x-mode source is highly asymmetric, despite the apparent symmetry of the sunspot, and its appearance and location imply that the strongest magnetic fields in the corona are localized in a compact flux tube. 21 refs.

  13. Evolution of Crustal Magnetic Fields in Isolated Neutron Stars : Combined Effects of Cooling and Curvature of Space-time

    E-Print Network [OSTI]

    Sujan Sengupta

    1998-01-29T23:59:59.000Z

    The ohmic decay of magnetic fields confined within the crust of neutron stars is considered by incorporating both the effect of neutron star cooling and the effect of space-time curvature produced by the intense gravitational field of the star. For this purpose a stationary and static gravitational field has been considered with the standard as well as the accelerated cooling models of neutron stars. It is shown that general relativistic effect reduces the magnetic field decay rate substantially. At the late stage of evolution when the field decay is mainly determined by the impurity-electron scattering, the effect of space-time curvature suppresses the role of the impurity content significantly and reduces the decay rate by more than an order of magnitude. Even with a high impurity content the decay rate is too low to be of observational interest if the accelerated cooling model along with the effect of space-time curvature is taken into account. It is, therefore, pointed out that if a decrease in the magnetic field strength by more than two orders of magnitude from its initial value is detected by observation then the existence of quark in the core of the neutron star would possibly be ruled out.

  14. Laser-induced magnetic fields in ICF capsules, Final Report, DE-FG02-08ER85128, Phase 1

    SciTech Connect (OSTI)

    Lindman, Erick L

    2009-11-05T23:59:59.000Z

    Laser-induced magnetic fields in ICF capsules Final Report, DE-FG02-08ER85128, Phase 1 E. L. LINDMAN, Otowi Technical Services, Los Alamos, NM. The performance of an inertial-confinement-fusion (ICF) capsule can be improved by inserting a magnetic field into it before compressing it [Kirkpatrick, et al., Fusion Technol. 27, 205 (1995)]. To obtain standoff in an ICF power generator, a method of inserting the field without the use of low-inductance leads attached to the capsule is desired. A mechanism for generating such a field using a laser was discovered in Japan [Sakagami, et al., Phys. Rev. Lett. 42, 839 (1979), Kolodner and Yablonovitch, Phys. Rev. Lett. 43, 1402 (1979)] and studied at Los Alamos in the 1980s [M. A. Yates, et al., Phys. Rev. Lett. 49, 1702 (1982); Forslund and Brackbill, Phys. Rev. Lett. 48, 1614 (1982)]. In this mechanism, a p-polarized laser beam strikes a solid target producing hot electrons that are accelerated away from the target surface by resonant absorption. An electric field is created that returns the hot electrons to the target. But, they do not return to the target along the same trajectory on which they left. The resulting current produces a toroidal magnetic field that was observed to spread over a region outside the hot spot with a radius of a millimeter. No experimental measurements of the magnetic field strength were performed. Estimates from computer simulation suggest that field strengths in the range of 1 to 10 Mega gauss (100 to 1000 Tesla) were obtained outside of the laser spot. To use this mechanism to insert a magnetic field into an ICF capsule, the capsule must be redesigned. In one approach, a central conductor is added, a toroidal gap is cut in the outer wall and the DT fuel is frozen on the inner surface of the capsule. The capsule is dropped into the reaction chamber and struck first with the laser that generates the magnetic field. The laser hot spot is positioned at the center of the toroidal gap. As the magnetic field spreads from the hot spot over the surface that contains the toroidal gap, it will propagate through the gap and set up a steady state in the capsule. The main compression is then initiated. First, it closes the gap and crow-bars the field, then it compresses the fuel to ignition. In addition to this application, we discuss the use of this mechanism to induce Mega-gauss fields in laboratory apparatus for measurements of the effects of large magnetic fields on material samples. A preliminary target design for this purpose is presented. It is made of high-density material with no hydrogen surface contamination to minimize fast ion losses and to minimize x-ray preheat of the sample (the material, whose magnetic properties are to be measured). In it, the gap is designed to allow the magnetic field to move into the interior of the target while minimizing the flow of hot electrons into the interior. By adjusting the size of the gap as well as its configuration, the hot electron effects can be minimized. Since the strength of the magnetic field depends on the radial distance to the sample from the center of the conductor carrying the return current, the sample is located at a point of minimum conductor radius. This location also minimizes the effects on the measurement of any hot electrons that flow into the interior. Useful experiments can be accomplished with the “seed” field alone in this geometry. Compressing the capsule after the insertion of the seed field may allow experiments with even larger magnetic fields. We have used computer-simulation techniques to address a number of issues. Our conclusions include: • This magnetic-field generating mechanism is a viable method for generating magnetic fields in ICF targets and for laboratory experiments. • Useful experiments on material samples can be done with the seed field of 1 to10 Mega gauss (100 to 1000 Tesla) and higher magnetic fields can be obtained by subsequently compressing the capsule. • The results reported here can be studied experimentally with a modest CO2 laser that emits 4.5 J of ene

  15. THE INTERPLAY OF TURBULENCE AND MAGNETIC FIELDS IN STAR-FORMING REGIONS: SIMULATIONS AND OBSERVATIONS

    SciTech Connect (OSTI)

    Kirk, Helen; Johnstone, Doug [Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1 (Canada); Basu, Shantanu [Department of Physics and Astronomy, University of Western Ontario, 1151 Richmond Street, London, ON, N6A 3K7 (Canada)], E-mail: hkirk@uvastro.phys.uvic.ca

    2009-07-10T23:59:59.000Z

    We analyze a suite of thin-sheet magnetohydrodynamical simulations based on the formulation of Basu, Ciolek, Dapp, and Wurster. These simulations allow us to examine the observational consequences to a star-forming region of varying the input level of turbulence (between thermal and a Mach number of 4) and the initial magnetic field strength corresponding to a range of mass to flux ratios between subcritical ({mu}{sub 0} = 0.5) and supercritical ({mu}{sub 0} = 10). The input turbulence is allowed to decay over the duration of the simulation. We compare the measured observable quantities with those found from surveying the Perseus molecular cloud. We find that only the most turbulent of simulations (high Mach number and weak magnetic field) have sufficient large-scale velocity dispersion (at {approx}1 pc) to match that observed across extinction regions in Perseus. Generally, the simulated core ({approx}0.02 pc) and line-of-sight velocity dispersions provide a decent match to observations. The motion between the simulated core and its local environment, however, is far too large in simulations with high large-scale velocity dispersion.

  16. Proper Motions of OH Masers and Magnetic Fields in Massive Star-Forming Regions

    E-Print Network [OSTI]

    Vincent L. Fish; Mark J. Reid

    2007-08-08T23:59:59.000Z

    We present data of proper motions of OH masers in the massive star-forming regions ON 1, K3-50, and W51 Main/South. OH maser motions in ON 1 are consistent with expansion at approximately 5 km/s, likely tracing the expanding ultracompact H II region. Motions in K3-50 are faster and may be indicating the final stages of OH maser emission in the source, before the OH masers turn off as the H II region transitions from the ultracompact to the compact phase. W51 South shows indications of aspherical expansion, while motions in W51 Main are more difficult to interpret. Nevertheless, it appears that the relative projected separation between W51 Main and W51 South is decreasing, corresponding to an estimate of enclosed mass of at least 1500 solar masses, consistent with estimates derived from millimeter-wavelength dust emission. We confirm the ~20 mG magnetic fields previously seen in W51 Main, which may represent the upper end of the density range allowable for 1665 MHz maser emission. Magnetic field strengths and directions, obtained from Zeeman splitting, in each source are consistent with values obtained in the first epoch four to nine years ago.

  17. Collective Modes of Chiral Kinetic Theory in Magnetic Field

    E-Print Network [OSTI]

    Mikhail Stephanov; Ho-Ung Yee; Yi Yin

    2014-12-31T23:59:59.000Z

    We study collective excitations in systems described by chiral kinetic theory in external magnetic field. We consider high-temperature weak-coupling plasma, as well as high-density Landau Fermi liquid with interaction not restricted to be weak. We show that chiral magnetic wave (CMW) emerges in hydrodynamic regime (at frequencies smaller than collision relaxation rate) and the CMW velocity is determined by thermodynamic properties only. We find that in a plasma of opposite chiralities, at frequencies smaller than the chirality-flipping rate, the CMW excitation turns into a vector-like diffusion mode. In the interacting Fermi liquid, the CMW turns into the Landau zero sound mode in the high-frequency collisionless regime.

  18. Collective Modes of Chiral Kinetic Theory in Magnetic Field

    E-Print Network [OSTI]

    Stephanov, Mikhail; Yin, Yi

    2015-01-01T23:59:59.000Z

    We study collective excitations in systems described by chiral kinetic theory in external magnetic field. We consider high-temperature weak-coupling plasma, as well as high-density Landau Fermi liquid with interaction not restricted to be weak. We show that chiral magnetic wave (CMW) emerges in hydrodynamic regime (at frequencies smaller than collision relaxation rate) and the CMW velocity is determined by thermodynamic properties only. We find that in a plasma of opposite chiralities, at frequencies smaller than the chirality-flipping rate, the CMW excitation turns into a vector-like diffusion mode. In the interacting Fermi liquid, the CMW turns into the Landau zero sound mode in the high-frequency collisionless regime.

  19. Magnetic-field dependent trap loss of ultracold metastable helium

    E-Print Network [OSTI]

    J. S. Borbely; R. van Rooij; S. Knoop; W. Vassen

    2011-11-24T23:59:59.000Z

    We have experimentally studied the magnetic-field dependence of the decay of a Bose-Einstein condensate of metastable 4He atoms confined in an optical dipole trap, for atoms in the m=+1 and m=-1 magnetic substates, and up to 450 G. Our measurements confirm long-standing calculations of the two-body loss rate coefficient that show an increase above 50 G. We demonstrate that for m=-1 atoms, decay is due to three-body recombination only, with a three-body loss rate coefficient of 6.5(0.4)(0.6)10^(-27)cm^6s^(-1), which is interesting in the context of universal few-body theory. We have also searched for a recently-predicted d-wave Feshbach resonance, but did not observe it.

  20. Thermal and high magnetic field treatment of materials and associated apparatus

    DOE Patents [OSTI]

    Kisner, Roger A.; Wilgen, John B.; Ludtka, Gerard M.; Jaramillo, Roger A.; Mackiewicz-Ludtka, Gail

    2010-06-29T23:59:59.000Z

    An apparatus and method for altering characteristics, such as can include structural, magnetic, electrical, optical or acoustical characteristics, of an electrically-conductive workpiece utilizes a magnetic field within which the workpiece is positionable and schemes for thermally treating the workpiece by heating or cooling techniques in conjunction with the generated magnetic field so that the characteristics of the workpiece are effected by both the generated magnetic field and the thermal treatment of the workpiece.

  1. Thermal and high magnetic field treatment of materials and associated apparatus

    DOE Patents [OSTI]

    Kisner, Roger A.; Wilgen, John B.; Ludtka, Gerard M.; Jaramillo, Roger A.; Mackiewicz-Ludtka, Gail

    2007-01-09T23:59:59.000Z

    An apparatus and method for altering characteristics, such as can include structural, magnetic, electrical, optical or acoustical characteristics, of an electrically-conductive workpiece utilizes a magnetic field within which the workpiece is positionable and schemes for thermally treating the workpiece by heating or cooling techniques in conjunction with the generated magnetic field so that the characteristics of the workpiece are effected by both the generated magnetic field and the thermal treatment of the workpiece.

  2. Low pressure arc discharge lamp apparatus with magnetic field generating means

    DOE Patents [OSTI]

    Grossman, M.W.; George, W.A.; Maya, J.

    1987-10-06T23:59:59.000Z

    A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25 C. 3 figs.

  3. Weak magnetic field effects on chiral critical temperature in a nonlocal Nambu--Jona-Lasinio model

    E-Print Network [OSTI]

    M. Loewe; F. Marquez; C. Villavicencio; R. Zamora

    2014-10-27T23:59:59.000Z

    In this article we study the nonlocal Nambu--Jona-Lasinio model with a Gaussian regulator in the chiral limit. Finite temperature effects and the presence of a homogeneous magnetic field are considered. The magnetic evolution of the critical temperature for chiral symmetry restoration is then obtained. Here we restrict ourselves to the case of low magnetic field values, being this a complementary discussion to the exisiting analysis in nonlocal models in the strong magnetic field regime.

  4. BTA Magnet Field Map Archive and MAD Model

    SciTech Connect (OSTI)

    Glenn,J.W.

    2008-04-01T23:59:59.000Z

    This note publishes some and information that has resided in private files. The attached tables were provided by Joseph Skelly from his archives. They show magnetic field measurements versus excitation current for the Booster to AGS transfer line quadrupoles and dipoles based on field measurements [we believe] were done by the Magnet Division. Also given are Ed Blesser's fifth order fits of field versus current. The results are given in 'Tesla' or T-M/M. These tables are attached to provide an archive of this data. The MAD model of the BTA line does have the same values as shown in the attached fits so the transfer was correct. MAD uses as its 'gradient' for quads Tesla per meter normalized to rigidity [B-rho]. The model of the BTA line in use uses the T-M/M given in the tables divided by the length to give T M which is then normalized by Brho. Thus, the input to the model appears to be correct. The original model is also attached as part of a memo by Skelly describing it.

  5. An observational test of magnetospheric magnetic field mapping

    SciTech Connect (OSTI)

    Weiss, L.A.; Thomsen, M.F.; Reeves, G.D.; Hones, E.W.; McComas, D.J.

    1994-07-01T23:59:59.000Z

    The distortion of the geomagnetic field is a key signature of the response of the magnetosphere to the solar wind input. A number of empirical models have been devised to estimate the magnetic field direction and magnitude at any point within the magnetosphere under a variety of conditions. We describe a technique whereby the field-line mapping predicted by such models is tested by matching measurements of magnetospheric plasma energy spectra obtained by Los Alamos instruments at geosynchronous orbit with spectra obtained by instruments on the polar-orbiting DMSP satellites (at an altitude of about 800 km) at times when the two satellites are in approximate magnetic conjugacy. With up to three geosynchronous satellites and as many as four DMSP satellites in operation at any given time, there are a very large number of such two-satellite conjunctions, allowing the model mappings to be tested under a wide range of local times and geomagnetic activity. Preliminary results from the application of this technique are presented for one week of data from March, 1991.

  6. Ultrasensitive magnetic field detection using a single artificial atom

    E-Print Network [OSTI]

    Mustafa Bal; Chunqing Deng; Jean-Luc Orgiazzi; Florian Ong; Adrian Lupascu

    2013-01-04T23:59:59.000Z

    Efficient detection of magnetic fields is central to many areas of research and has important practical applications ranging from materials science to geomagnetism. High sensitivity detectors are commonly built using direct current-superconducting quantum interference devices (DC-SQUIDs) or atomic systems. Here we use a single artificial atom to implement an ultrahigh sensitivity magnetometer with a size in the micron range. The artificial atom is a superconducting two-level system at low temperatures, operated in a way similar to atomic magnetometry. The high sensitivity results from quantum coherence combined with strong coupling to magnetic field. By employing projective measurements, we obtain a sensitivity of $2.7\\, \\t{pT}/\\sqrt{\\t{Hz}}$ at 10 MHz. We discuss feasible improvements that will increase the sensitivity by over one order of magnitude. The intrinsic sensitivity of this method to AC fields in the 100 kHz - 10 MHz range compares favourably with DC-SQUIDs and atomic magnetometers of equivalent spatial resolution. This result illustrates the potential of artificial quantum systems for sensitive detection and related applications.

  7. Perfect 2-d quadrupole fields from permanent magnets

    SciTech Connect (OSTI)

    Lee, E.P.; Vella, M. [Lawrence Berkeley National Lab., CA (United States). Accelerator and Fusion Research Div.

    1996-04-01T23:59:59.000Z

    Consider the 13-beam channel array shown in Figure 1. It is asserted that, under mathematically ideal assumptions, a pure quadrupole field is centered in each of the 13 beam channel boxes. An identical quadrupole field (for {bar H}, not {bar B}) is also centered in each of the 4 boxes containing 4 magnetic wedges located near the center of the system. An iron yoke ({mu} = {infinity}) with the displayed zig-zag shape provides a boundary condition (H{sub {parallel}} = 0) that makes the 13 channels equivalent to a portion of an infinite array. A similar array can be readily drawn for any number of beams. The quadrupole gradient in the beam channels is B{prime} = M{sub o}/2b, where M{sub o} is the remnant field of the magnetic wedges, and the channel diameter (wedge-to-wedge) is 2b. Note that a unit cell of the array, containing one beam, has diameter 2{radical}2 b (viewed from 45{degree} tilt) so its area is 8 b{sup 2}. A significant advantage of this design over those using dipolar blocks is the large fraction of cross section devoted to beam channels (50% vs 25%). Application to a heavy ion fusion driver is discussed.

  8. VELOCITY AND MAGNETIC FIELD DISTRIBUTION IN A FORMING PENUMBRA

    SciTech Connect (OSTI)

    Romano, P.; Guglielmino, S. L. [INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95125 Catania (Italy); Frasca, D.; Zuccarello, F. [Dipartimento di Fisica e Astronomia-Sezione Astrofisica, Universita di Catania, Via S. Sofia 78, I-95125 Catania (Italy); Ermolli, I. [INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone (Italy); Tritschler, A.; Reardon, K. P., E-mail: prom@oact.inaf.it [National Solar Observatory/Sacramento Peak, P.O. Box 62, Sunspot, NM 88349-0062 (United States)

    2013-07-01T23:59:59.000Z

    We present results from the analysis of high-resolution spectropolarimetric and spectroscopic observations of the solar photosphere and chromosphere, obtained shortly before the formation of a penumbra in one of the leading polarity sunspots of NOAA active region 11490. The observations were performed at the Dunn Solar Telescope of the National Solar Observatory on 2012 May 28, using the Interferometric Bidimensional Spectrometer. The data set is comprised of a 1 hr time sequence of measurements in the Fe I 617.3 nm and Fe I 630.25 nm lines (full Stokes polarimetry) and in the Ca II 854.2 nm line (Stokes I only). We perform an inversion of the Fe I 630.25 nm Stokes profiles to derive magnetic field parameters and the line-of-sight (LOS) velocity at the photospheric level. We characterize chromospheric LOS velocities by the Doppler shift of the centroid of the Ca II 854.2 nm line. We find that, before the formation of the penumbra, an annular zone of 3''-5'' width is visible around the sunspot. In the photosphere, we find that this zone is characterized by an uncombed structure of the magnetic field although no visible penumbra has formed yet. We also find that the chromospheric LOS velocity field shows several elongated structures characterized by downflow and upflow motions in the inner and outer parts of the annular zone, respectively.

  9. Analysis of Biological Effects and Limits of Exposure to Weak Magnetic Fields

    E-Print Network [OSTI]

    Halgamuge, Malka N.

    to weak magnetic fields and geomagnetic field to elucidate the main points of contention. Most of the weak excitation and cardio stimulation can be caused due to the current induced in the body from high power fields [2]. The energy absorption rate of these high power magnetic fields is measured by the specific

  10. Tokamak with in situ magnetohydrodynamic generation of toroidal magnetic field

    DOE Patents [OSTI]

    Schaffer, Michael J. (San Diego, CA)

    1986-01-01T23:59:59.000Z

    A tokamak apparatus includes an electrically conductive metal pressure vessel for defining a chamber and confining liquid therein. A liner disposed within said chamber defines a toroidal space within the liner and confines gas therein. The metal vessel provides an electrically conductive path linking the toroidal space. Liquid metal is forced outwardly through the chamber outside of the toroidal space to generate electric current in the conductive path and thereby generate a toroidal magnetic field within the toroidal space. Toroidal plasma is developed within the toroidal space about the major axis thereof.

  11. Confined System with Rashba Coupling in Constant Magnetic Field

    E-Print Network [OSTI]

    Mohammed El Bouziani; Rachid Houca; Ahmed Jellal

    2012-04-30T23:59:59.000Z

    We study a two dimensional system of electrons with Rashba coupling in the constant magnetic field $B$ and confining potential. We algebraically diagonalize the corresponding Hamiltonian to end up with the solutions of the energy spectrum. In terms of two kinds of operator we construct two symmetries and discuss the filling of the shells with electrons for strong and weak $B$. Subsequently, we show that our system is sharing some common features with quantum optics where the exact operator solutions for the basics Jaynes-Cummings variables are derived from our results. An interesting limit is studied and the corresponding quantum dynamics is recovered.

  12. System having unmodulated flux locked loop for measuring magnetic fields

    DOE Patents [OSTI]

    Ganther, Jr., Kenneth R. (Olathe, KS); Snapp, Lowell D. (Blue Springs, MO)

    2006-08-15T23:59:59.000Z

    A system (10) for measuring magnetic fields, wherein the system (10) comprises an unmodulated or direct-feedback flux locked loop (12) connected by first and second unbalanced RF coaxial transmission lines (16a, 16b) to a superconducting quantum interference device (14). The FLL (12) operates for the most part in a room-temperature or non-cryogenic environment, while the SQUID (14) operates in a cryogenic environment, with the first and second lines (16a, 16b) extending between these two operating environments.

  13. Microparticles in a Collisional Rf Plasma Sheath under Hypergravity Conditions as Probes for the Electric Field Strength and the Particle Charge

    SciTech Connect (OSTI)

    Beckers, J.; Stoffels, W. W.; Dijk, J. van; Kroesen, G. M. W. [Eindhoven University of Technology, Department of Applied Physics P.O. Box 513, 5600 MB, Eindhoven (Netherlands); Ockenga, T.; Wolter, M.; Kersten, H. [Institut fuer Experimentelle und Angewandte Physik, Christian-Albrechts-Universitaet Kiel, Olshausenstrasse 40-60, 24098 Kiel (Germany)

    2011-03-18T23:59:59.000Z

    We used microparticles under hypergravity conditions, induced by a centrifuge, in order to measure nonintrusively and spatially resolved the electric field strength as well as the particle charge in the collisional rf plasma sheath. The measured electric field strengths demonstrate good agreement with the literature, while the particle charge shows decreasing values towards the electrode. We demonstrate that it is indeed possible to measure these important quantities without changing or disturbing the plasma.

  14. Magnetic Field Clumping in Massive Star-Forming Regions as Determined from Excited-State OH Absorption and Maser Emission

    E-Print Network [OSTI]

    Vincent L. Fish; Mark J. Reid; Karl M. Menten

    2005-01-10T23:59:59.000Z

    We have observed six high-mass star-forming regions in the 2 Pi 3/2, J = 7/2 lines of OH using the GBT in order to investigate whether the magnetic field, and hence the density, measured in absorption differs from that implied by maser Zeeman splitting. We detect absorption in both the 13441 and 13434 MHz main lines in all six sources. Zeeman splitting in the F = 3-3 absorption line in W3(OH) implies a line-of-sight magnetic field strength of 3.0 +/- 0.3 mG. This is significantly less than full magnetic field strengths detected from OH maser Zeeman splitting, suggesting that OH maser regions may be denser than the non-masing OH material by a factor of several. Zeeman splitting is not detected in other sources, but we are able to place upper limits on B_parallel of 1.2 mG in G10.624-0.385 and 2.9 mG in K3-50. These results are consistent with a density enhancement of the masers, but other explanations for the lower magnetic field in absorption compared to maser emission are possible for these two sources. Absorption in one or both of the 13442 and 13433 MHz satellite lines is also seen in four sources. This is the very first detection of the 2 Pi 3/2, J = 7/2 satellite lines. Ratios of satellite-line to main-line absorption suggest enhancement of the satellite lines from local thermodynamic equilibrium values. Masers are seen in the F = 4-4 and 3-3 transitions of W3(OH) and the 4-4 transition of ON 1. A previously undetected 4-4 maser is seen near -44.85 km/s in W3(OH).

  15. NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSVOLUME 11 N0.1 2004

    E-Print Network [OSTI]

    Weston, Ken

    NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSVOLUME 11 · N0.1 · 2004 OPERATED BY: FLORIDA STATE R E V I E W BIOLOGY BIOCHEMISTRY CHEMISTRY CRYOGENICS ENGINEERING MATERIALS GEOCHEMISTRY INSTRUMENTATION KONDO/HEAVY FERMION SYSTEMS MAGNET TECHNOLOGY MAGNETIC RESONANCE TECHNIQUES MAGNETISMAND MAGNETIC

  16. Phase-field simulation of strain-induced domain switching in magnetic thin films

    E-Print Network [OSTI]

    Chen, Long-Qing

    Phase-field simulation of strain-induced domain switching in magnetic thin films Jia-Mian Hu, G of the Bloch point in a magnetic film with strong uniaxial magnetic anisotropy Low Temp. Phys. 37, 690 (2011) Evolution of magnetic bubble domains in manganite films Appl. Phys. Lett. 99, 042503 (2011) 360° domain wall

  17. NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSSPECIAL EDITION VOLUME 13 N0. 1 2006

    E-Print Network [OSTI]

    Weston, Ken

    , and Geochemistry 16 MAGNET SCIENCE & TECHNOLOGY Engineering Materials, Instrumentation, and Magnet Technology 20NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSSPECIAL EDITION VOLUME 13 · N0. 1 · 2006 SUPPORTED HIGHLIGHTS FROM Life Sciences Chemistry Magnet Science & Technology Condensed Matter Page 15 #12;NHMFLREPORTS

  18. Torsional oscillations of a magnetar with a tangled magnetic field

    E-Print Network [OSTI]

    Link, Bennett

    2015-01-01T23:59:59.000Z

    We propose a scenario for the quasi-periodic oscillations observed in magnetar flares wherein a tangled component of the stellar magnetic field introduces nearly isotropic stress that gives the fluid core of the star an effective shear modulus. In a simple, illustrative model of constant density, the tangled field eliminates the problematic Alfv\\'en continuum that would exist in the stellar core for an organized field. For a tangled field energy density comparable to that inferred from the measured dipole fields of $\\sim 10^{15}$ G in SGRs 1806-20 and 1900+14, torsional modes exist with fundamental frequencies of about 20 Hz, and mode spacings of $\\sim 10$ Hz. For fixed stellar mass and radius, the model has only one free parameter, and can account for {\\em every} observed QPO under 160 Hz to within 3 Hz for both SGRs 1806-20 and 1900+14. The combined effects of stratification and crust stresses generally decrease the frequencies of torsional oscillations by $<10$% for overtones and increase the lowest-fre...

  19. NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSVOLUME 11 N0.2 2004

    E-Print Network [OSTI]

    Weston, Ken

    , recognized as the world leader in magnet science, engineering, and experimental infrastructureNATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSVOLUME 11 · N0.2 · 2004 OPERATED BY: FLORIDA STATE: National High Magnetic Field Laboratory 1800 East Paul Dirac Drive Tallahassee, Florida 32310-3706 Tel: 850

  20. LDRD final report on confinement of cluster fusion plasmas with magnetic fields.

    SciTech Connect (OSTI)

    Argo, Jeffrey W.; Kellogg, Jeffrey W.; Headley, Daniel Ignacio; Stoltzfus, Brian Scott; Waugh, Caleb J.; Lewis, Sean M.; Porter, John Larry, Jr.; Wisher, Matthew; Struve, Kenneth William; Savage, Mark Edward; Quevedo, Hernan J.; Bengtson, Roger

    2011-11-01T23:59:59.000Z

    Two versions of a current driver for single-turn, single-use 1-cm diameter magnetic field coils have been built and tested at the Sandia National Laboratories for use with cluster fusion experiments at the University of Texas in Austin. These coils are used to provide axial magnetic fields to slow radial loss of electrons from laser-produced deuterium plasmas. Typical peak field strength achievable for the two-capacitor system is 50 T, and 200 T for the ten-capacitor system. Current rise time for both systems is about 1.7 {mu}s, with peak current of 500 kA and 2 MA, respectively. Because the coil must be brought to the laser, the driver needs to be portable and drive currents in vacuum. The drivers are complete but laser-plasma experiments are still in progress. Therefore, in this report, we focus on system design, initial tests, and performance characteristics of the two-capacitor and ten-capacitors systems. The questions of whether a 200 T magnetic field can retard the breakup of a cluster-fusion plasma, and whether this field can enhance neutron production have not yet been answered. However, tools have been developed that will enable producing the magnetic fields needed to answer these questions. These are a two-capacitor, 400-kA system that was delivered to the University of Texas in 2010, and a 2-MA ten-capacitor system delivered this year. The first system allowed initial testing, and the second system will be able to produce the 200 T magnetic fields needed for cluster fusion experiments with a petawatt laser. The prototype 400-kA magnetic field driver system was designed and built to test the design concept for the system, and to verify that a portable driver system could be built that delivers current to a magnetic field coil in vacuum. This system was built copying a design from a fixed-facility, high-field machine at LANL, but made to be portable and to use a Z-machine-like vacuum insulator and vacuum transmission line. This system was sent to the University of Texas in Austin where magnetic fields up to 50 T have been produced in vacuum. Peak charge voltage and current for this system have been 100 kV and 490 kA. It was used this last year to verify injection of deuterium and surrogate clusters into these small, single-turn coils without shorting the coil. Initial test confirmed the need to insulate the inner surface of the coil, which requires that the clusters must be injected through small holes in an insulator. Tests with a low power laser confirmed that it is possible to inject clusters into the magnetic field coils through these holes without destroying the clusters. The university team also learned the necessity of maintaining good vacuum to avoid insulator, transmission line, and coil shorting. A 200-T, 2 MA system was also constructed using the experience from the first design to make the pulsed-power system more robust. This machine is a copy of the prototype design, but with ten 100-kV capacitors versus the two used in the prototype. It has additional inductance in the switch/capacitor unit to avoid breakdown seen in the prototype design. It also has slightly more inductance at the cable connection to the vacuum chamber. With this design we have been able to demonstrate 1 MA current into a 1 cm diameter coil with the vacuum chamber at air pressure. Circuit code simulations, including the additional inductance with the new design, agree well with the measured current at a charge voltage of 40 kV with a short circuit load, and at 50 kV with a coil. The code also predicts that with a charge voltage of 97 kV we will be able to get 2 MA into a 1 cm diameter coil, which will be sufficient for 200 T fields. Smaller diameter or multiple-turn coils will be able to achieve even higher fields, or be able to achieve 200-T fields with lower charge voltage. Work is now proceeding at the university under separate funding to verify operation at the 2-MA level, and to address issues of debris mitigation, measurement of the magnetic field, and operation in vacuum. We anticipate operation at full current with single

  1. Proton radiography of magnetic field produced by ultra-intense laser irradiating capacity-coil target

    E-Print Network [OSTI]

    Wang, W W; Chen, J; Cai, H B; He, S K; Zhou, W M; Shan, L Q; Lu, F; Wu, Y C; Hong, W; Liu, D X; Bi, B; Zhang, F; Xue, F B; Li, B Y; Zhang, B; He, Y L; He, W; Jiao, J L; Dong, K G; Zhang, F Q; Deng, Z G; Zhang, Z M; Cui, B; Han, D; Zhou, K N; Wang, X D; Zhao, Z Q; Cao, L F; Zhang, B H; He, X T; Gu, Y Q

    2014-01-01T23:59:59.000Z

    Ultra-intense ultra-short laser is firstly used to irradiate the capacity-coil target to generate magnetic field. The spatial structure and temporal evolution of huge magnetic fields were studied with time-gated proton radiography method. A magnetic flux density of 40T was measured by comparing the proton deflection and particle track simulations. Although the laser pulse duration is only 30fs, the generated magnetic field can last for over 100 picoseconds. The energy conversion efficiency from laser to magnetic field can reach as high as ~20%. The results indicate that tens of tesla (T) magnetic field could be produced in many ultra intense laser facilities around the world, and higher magnetic field could be produced by picosecond lasers.

  2. Molten metal feed system controlled with a traveling magnetic field

    DOE Patents [OSTI]

    Praeg, Walter F. (Palos Park, IL)

    1991-01-01T23:59:59.000Z

    A continuous metal casting system in which the feed of molten metal is controlled by means of a linear induction motor capable of producing a magnetic traveling wave in a duct that connects a reservoir of molten metal to a caster. The linear induction motor produces a traveling magnetic wave in the duct in opposition to the pressure exerted by the head of molten metal in the reservoir so that p.sub.c =p.sub.g -p.sub.m where p.sub.c is the desired pressure in the caster, p.sub.g is the gravitational pressure in the duct exerted by the force of the head of molten metal in the reservoir, and p.sub.m is the electromagnetic pressure exerted by the force of the magnetic field traveling wave produced by the linear induction motor. The invention also includes feedback loops to the linear induction motor to control the casting pressure in response to measured characteristics of the metal being cast.

  3. Thermoelectric Conductivities at Finite Magnetic Field and the Nernst Effect

    E-Print Network [OSTI]

    Keun-Young Kim; Kyung Kiu Kim; Yunseok Seo; Sang-Jin Sin

    2015-03-17T23:59:59.000Z

    We study electric, thermoelectric, and thermal conductivities of a strongly correlated system in the presence of magnetic field by gauge/gravity duality. We consider a general class of Einstein-Maxwell-Dilaton theory with axion fields imposing momentum relaxation. Analytic general formulas for DC conductivities and the Nernst signal are derived in terms of the black hole horizon data. For an explicit model study we analyse in detail the dyonic black hole modified by momentum relaxation. In this model, the Nernst signal shows a typical vortex-liquid effect when momentum relaxation effect is comparable to chemical potential. We compute all AC electric, thermoelectric, and thermal conductivities by numerical analysis and confirms that their zero frequency limits precisely reproduce our analytic formulas, which is a non-trivial consistency check of our methods. We discuss the momentum relaxation effect on conductivities including cyclotron resonance poles.

  4. Ferrofluid nucleus phase transitions in an external uniform magnetic field

    E-Print Network [OSTI]

    B. M. Tanygin; S. I. Shulyma; V. F. Kovalenko; M. V. Petrychuk

    2015-02-18T23:59:59.000Z

    Phase transition between massive dense phase and diluted superparamagnetic phase is studied by means of direct molecular dynamics simulation. Equilibrium structures of ferrofluid aggregate nucleus are obtained for different values of temperature and external magnetic field magnitude. For the ferrofluid phase diagram (coordinates "field-temperature"): approximate match of experiment and simulation is shown. Obtained phase coexistence curve has opposite trend compare to some of known theoretical results. This contradiction is related to postulating and comparing of the free energy of only simplest ferrofluid structures: diluted superparamagnetic phase, linear chains of the particles, and dense globes. The present results provide more fine structure of transition from "linear chains" to "dense globes" phase, e.g. through the ring assembly structure.

  5. Thermoelectric Conductivities at Finite Magnetic Field and the Nernst Effect

    E-Print Network [OSTI]

    Kim, Keun-Young; Seo, Yunseok; Sin, Sang-Jin

    2015-01-01T23:59:59.000Z

    We study electric, thermoelectric, and thermal conductivities of a strongly correlated system in the presence of magnetic field by gauge/gravity duality. We consider a general class of Einstein-Maxwell-Dilaton theory with axion fields imposing momentum relaxation. Analytic general formulas for DC conductivities and the Nernst signal are derived in terms of the black hole horizon data. For an explicit model study we analyse in detail the Dyonic black hole modified by momentum relaxation effect. In this model, the Nernst signal shows a typical vortex-liquid effect when momentum relaxation effect is comparable to chemical potential. We compute all AC electric, thermal, and thermal conductivities by numerical analysis and confirms that their zero frequency limits precisely reproduce our analytic formulas, which is a non-trivial consistency check of our methods. We discuss the momentum relaxation effect on conductivities including cyclotron frequencies.

  6. Magnetic field induced third order susceptibility of third order harmonic generation in a ZnMgSe strained quantum well

    SciTech Connect (OSTI)

    Mark, J. Abraham Hudson, E-mail: a.john.peter@gmail.com; Peter, A. John, E-mail: a.john.peter@gmail.com [Dept. of Physics, SSM Institute of Engineering and Technology, Dindigul-624002 (India)

    2014-04-24T23:59:59.000Z

    Third order susceptibility of third order harmonic generation is investigated in a Zn{sub 0.1}Mg{sub 0.9}Se/Zn{sub 0.8}Mg{sub 0.2}Se/Zn{sub 0.1}Mg{sub 0.9}Se quantum well in the presence of magnetic field strength. The confinement potential is considered as the addition of energy offsets of the conduction band (or valence band) and the strain-induced potential in our calculations. The material dependent effective mass is followed throughout the computation because it has a high influence on the electron energy levels in low dimensional semiconductor systems.

  7. Magnetohydrodynamic turbulent cascade of coronal loop magnetic fields

    SciTech Connect (OSTI)

    Rappazzo, A. F. [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States); Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Delaware 19716 (United States); Velli, M. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)

    2011-06-15T23:59:59.000Z

    The Parker model for coronal heating is investigated through a high resolution simulation. An inertial range is resolved where fluctuating magnetic energy E{sub M}(k{sub perpendicular}){proportional_to}k{sub perpendicular}{sup -2.7} exceeds kinetic energy E{sub K}(k{sub perpendicular}){proportional_to}k{sub perpendicular}{sup -0.6}. Increments scale as {delta}b{sub l}{approx_equal}l{sup -0.85}and {delta}u{sub l}{approx_equal}l{sup +0.2} with velocity increasing at small scales, indicating that magnetic reconnection plays a prime role in this turbulent system. We show that spectral energy transport is akin to standard magnetohydrodynamic (MHD) turbulence even for a system of reconnecting current sheets sustained by the boundary. In this new MHD turbulent cascade, kinetic energy flows are negligible while cross-field flows are enhanced, and through a series of ''reflections'' between the two fields, cascade more than half of the total spectral energy flow.

  8. Field-Theoretical Treatment of Neutrino Oscillations The Strength of the Canonical Oscillation Formula

    E-Print Network [OSTI]

    Grimus, Walter; Stockinger, P

    1999-01-01T23:59:59.000Z

    We discuss conceptual aspects of neutrino oscillations with the main emphasis on the field-theoretical approach. This approach includes the neutrino source and detector processes and allows to obtain the neutrino transition or survival probabilities as cross sections derived from the Feynman diagram of the combined source - detection process. In this context, the neutrinos which are supposed to oscillate appear as propagators of the neutrino mass eigenfields, connecting the source and detection processes. We consider also the question why the canonical neutrino oscillation formula is so robust against corrections and discuss the nature of the oscillating neutrino state emerging in the field-theoretical approach.

  9. Field-Theoretical Treatment of Neutrino Oscillations: The Strength of the Canonical Oscillation Formula

    E-Print Network [OSTI]

    W. Grimus; S. Mohanty; P. Stockinger

    1999-09-13T23:59:59.000Z

    We discuss conceptual aspects of neutrino oscillations with the main emphasis on the field-theoretical approach. This approach includes the neutrino source and detector processes and allows to obtain the neutrino transition or survival probabilities as cross sections derived from the Feynman diagram of the combined source - detection process. In this context, the neutrinos which are supposed to oscillate appear as propagators of the neutrino mass eigenfields, connecting the source and detection processes. We consider also the question why the canonical neutrino oscillation formula is so robust against corrections and discuss the nature of the oscillating neutrino state emerging in the field-theoretical approach.

  10. Magnetic Fields in Star-Forming Molecular Clouds. V. Submillimeter Polarization of the Barnard 1 Dark Cloud

    E-Print Network [OSTI]

    Brenda C. Matthews; Christine D. Wilson

    2002-05-20T23:59:59.000Z

    We present 850 micron polarimetry from the James Clerk Maxwell Telescope toward several dense cores within the dark cloud Barnard 1 in Perseus. Significant polarized emission is detected from across the mapped area and is not confined to the locations of bright cores. This indicates the presence of aligned grains and hence a component of the magnetic field in the plane of the sky. Polarization vectors detected away from bright cores are strongly aligned at a position angle of ~ 90 degrees (east of north), while vectors associated with bright cores show alignments of varying orientations. There is no direct correlation between the polarization angles measured in earlier optical polarimetry toward Perseus and the polarized submillimeter thermal emission. Depolarization toward high intensities is exhibited, but toward the brightest core reaches a threshold beyond which no further decrease in polarization percentage is measured. The polarized emission data from the interior envelope are compared with previously published OH Zeeman data to estimate the total field strength and orientation under the assumption of a uniform and non-uniform field component in the region. These results are rough estimates only due to the single independent detection of Zeeman splitting toward Barnard 1. The uniform field component is thus calculated to be B(0) = 31 microGauss [+/- (0.52 (north) - 0.01 (east)) - 0.86 (l.o.s.)] in the case where we have assumed the ratio of the dispersion of the line-of-sight field to the field strength to be 0.2.

  11. High Magnetic Field Multipoles Generated by Superconductor Magnetization within a Set of Nested Superconducting Correction Coils

    E-Print Network [OSTI]

    Green, M.A.

    2011-01-01T23:59:59.000Z

    magnetization of the superconductor in the long correctorsMultipoles Generated by Superconductor Magnetization WithinMULTIPOLES GENERATED BY SUPERCONDUCTOR MAGNETIZATION WITHIN

  12. Theory of "Jitter" Radiation from Small-Scale Random Magnetic Fields and Prompt Emission from Gamma-Ray Burst Shocks

    E-Print Network [OSTI]

    Mikhail V. Medvedev

    2000-05-02T23:59:59.000Z

    Abridged.-- We demonstrate that the radiation emitted by ultrarelativistic electrons in highly nonuniform, small-scale magnetic fields is different from synchrotron radiation if the electron's transverse deflections in these fields are much smaller than the beaming angle. A quantitative analytical theory of this radiation, which we refer to as jitter radiation, is developed. It is shown that the emergent spectrum is determined by statistical properties of the magnetic field. As an example,we then use the model of a magnetic field in internal shocks of GRBs. The spectral power distribution of radiation produced by the power-law electrons is well described by a sharply broken power-law with indices 1 and -(p-1)/2 and the jitter break frequency is independent of the field strength but depends on the electron density in the ejecta. Since large-scale fields may also be present in the ejecta, we construct a two-component, jitter+synchrotron spectral model of the prompt $\\gamma$-ray emission. Quite surprisingly, this model seems to be readily capable of explaining several properties of time-resolved spectra of some GRBs, such as (i) the violation of the constraint on the low-energy spectral index called the synchrotron ``line of death'', (ii) the sharp spectral break at the peak frequency, inconsistent with the broad synchrotron bump, (iii) the evidence for two spectral sub-components, and (iv) possible existence of emission features called ``GRB lines''. We believe these facts strongly support both the existence of small-scale magnetic fields and the proposed radiation mechanism from GRB shocks. As an example, we use the composite model to analyze GRB 910503 which has two spectral peaks.

  13. Memorandum, Approval of a Permanent Variance Regarding Static Magnetic Fields at Brookhaven National Laboratory (Variance 102 1)

    Broader source: Energy.gov [DOE]

    Approval of a Permanenet Variance Regarding Static Magnetic Fields at Brookhaven National Laboratory (Variance 1021)

  14. Zeeman tomography of magnetic white dwarfs IV. The complex field structure of the polars EF Eri, BL Hyi, and CP Tuc

    E-Print Network [OSTI]

    K. Beuermann; F. Euchner; K. Reinsch; S. Jordan; B. T. Gaensicke

    2006-10-26T23:59:59.000Z

    The magnetic fields of the accreting white dwarfs (WDs) in magnetic cataclysmic variables (mCVs) determine the accretion geometries, the emission properties, and the secular evolution of these objects. We determine the structure of the surface magnetic fields of the WDs primaries in magnetic CVs using Zeeman tomography. Our study is based on orbital-phase resolved optical flux and circular polarization spectra of the polars EF Eri, BL Hyi, and CP Tuc obtained with FORS1 at the ESO VLT. An evolutionary algorithm is used to synthesize best fits to these spectra from an extensive database of pre-computed Zeeman spectra. The general approach has been described in previous papers of this series. The results achieved with simple geometries as centered or offset dipoles are not satisfactory. Significantly improved fits are obtained for multipole expansions that are truncated at degree l(max)=3 or 5 and include all tesseral and sectoral components with 0<=m<=l. The most frequent field strengths of 13, 18, and 10MG for EF Eri, BL Hyi, CP Tuc and the ranges of field strength covered are similar for the dipole and multipole models, but only the latter provide access to accreting matter at the right locations on the WD. The results suggest that the field geometries of the WDs in short-period mCVs are quite complex with strong contributions from multipoles higher than the dipole in spite of a typical age of the WDs in CVs in excess of 1 Gyr. It is feasible to derive the surface field structure of an accreting WD from phase-resolved low-state circular spectropolarimetry of sufficiently high signal-to-noise ratio. The fact that independent information is available on the strength and direction of the field in the accretion spot from high-state observations helps in unraveling the global field structure.

  15. Magnetic resonance studies of cement based materials in inhomogeneous magnetic fields

    SciTech Connect (OSTI)

    Boguszynska, Joanna [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, Poznan (Poland); Brown, Marc C.A. [School of Physical Sciences, University of Kent, Canterbury, Kent, CT2 7NR (United Kingdom); McDonald, Peter J. [School of Electronics and Physical Sciences, University of Surrey, Surrey, GU2 7XH (United Kingdom)]. E-mail: p.mcdonald@surrey.ac.uk; Mitchell, Jonathan [School of Electronics and Physical Sciences, University of Surrey, Surrey, GU2 7XH (United Kingdom); Mulheron, Mike [School of Engineering, University of Surrey, Surrey, GU2 7XH (United Kingdom); Tritt-Goc, Jadwiga [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, Poznan (Poland); Verganelakis, Dimitris A. [Department of Chemical Engineering, University of Cambridge, Cambridge, CB2 3RA (United Kingdom)

    2005-10-01T23:59:59.000Z

    Single-sided magnets give hope that Nuclear Magnetic Resonance (NMR) might in future be used for in situ characterisation of hydration and water transport in the surface layers of concrete slabs. Towards that end, a portable NMR-MOUSE (MObile Universal Surface Explorer) has been used to follow the hydration of gypsum based plaster, a Portland cement paste and concrete mortar. The results compare favourably to those obtained using a standard laboratory bench-top spectrometer. Further, stray field imaging (STRAFI) based methods have been used with embedded NMR detector coils to study water transport across a mortar/topping interface. The measured signal amplitudes are found to correlate with varying sample conditions.

  16. Turbulent magnetic fields in the quiet Sun: implications of Hinode observations and small-scale dynamo simulations

    E-Print Network [OSTI]

    Jonathan Pietarila Graham; Sanja Danilovic; Manfred Schuessler

    2009-03-11T23:59:59.000Z

    Using turbulent MHD simulations (magnetic Reynolds numbers up to 8000) and Hinode observations, we study effects of turbulence on measuring the solar magnetic field outside active regions. Firstly, from synthetic Stokes V profiles for the FeI lines at 630.1 and 630.2 nm, we show that a peaked probability distribution function (PDF) for observationally-derived field estimates is consistent with a monotonic PDF for actual vertical field strengths. Hence, the prevalence of weak fields is greater than would be naively inferred from observations. Secondly, we employ the fractal self-similar geometry of the turbulent solar magnetic field to derive two estimates (numerical and observational) of the true mean vertical unsigned flux density. We also find observational evidence that the scales of magnetic structuring in the photosphere extend at least down to an order of magnitude smaller than 200 km: the self-similar power-law scaling in the signed measure from a Hinode magnetogram ranges (over two decades in length scales and including the granulation scale) down to the 200 km resolution limit. From the self-similar scaling, we determine a lower bound for the true quiet-Sun mean vertical unsigned flux density of ~50 G. This is consistent with our numerically-based estimates that 80% or more of the vertical unsigned flux should be invisible to Stokes-V observations at a resolution of 200 km owing to the cancellation of signal from opposite magnetic polarities. Our estimates significantly reduce the order-of-magnitude discrepancy between Zeeman- and Hanle-based estimates.

  17. High Field Magnetization measurements of uranium dioxide single crystals (P08358- E003-PF)

    SciTech Connect (OSTI)

    K. Gofryk; N. Harrison; M. Jaime

    2014-12-01T23:59:59.000Z

    Conclusions: Our preliminary high field magnetic measurements of UO2 are consistent with a complex nature of the magnetic ordering in this material, compatible with the previously proposed non-collinear 3-k magnetic structure. Further extensive magnetic studies on well-oriented (<100 > and <111>) UO2 crystals are planned to address the puzzling behavior of UO2 in both antiferromagnetic and paramagnetic states at high fields.

  18. Electric Field Control of Ferromagnetism and Magnetic Devices Using Multiferroics

    E-Print Network [OSTI]

    Heron, John Thomas

    2013-01-01T23:59:59.000Z

    deplete holes from a magnetic semiconductor (InMnAs) using aof holes in the magnetic semiconductor while the black arrowto investigate magnetic semiconductors in his group. I had

  19. Chiral and parity symmetry breaking for planar fermions: Effects of a heat bath and uniform external magnetic field

    SciTech Connect (OSTI)

    Ayala, Alejandro [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, Mexico Distrito Federal 04510 (Mexico); Bashir, Adnan; Gutierrez, Enif; Raya, Alfredo [Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio C-3, Ciudad Universitaria, Morelia, Michoacan 58040 (Mexico); Sanchez, Angel [Instituto de Fisica y Matematicas, Universidad Michoacana de San Nicolas de Hidalgo, Edificio C-3, Ciudad Universitaria, Morelia, Michoacan 58040 (Mexico); Department of Physics, University of Texas at El Paso, El Paso, Texas 79968 (United States)

    2010-09-01T23:59:59.000Z

    We study chiral symmetry breaking for relativistic fermions, described by a parity-violating Lagrangian in 2+1-dimensions, in the presence of a heat bath and a uniform external magnetic field. Working within their four-component formalism allows for the inclusion of both parity-even and -odd mass terms. Therefore, we can define two types of fermion antifermion condensates. For a given value of the magnetic field, there exist two different critical temperatures which would render one of these condensates identically zero, while the other would survive. Our analysis is completely general: it requires no particular simplifying hierarchy among the energy scales involved, namely, bare masses, field strength, and temperature. However, we do reproduce some earlier results, obtained or anticipated in literature, corresponding to special kinematical regimes for the parity conserving case. Relating the chiral condensate to the one-loop effective Lagrangian, we also obtain the magnetization and the pair production rate for different fermion species in a uniform electric field through the replacement B{yields}-iE.

  20. Testing a Solar Coronal Magnetic Field Extrapolation Code with the Titov-Demoulin Magnetic Flux Rope Model

    E-Print Network [OSTI]

    Jiang, Chaowei

    2015-01-01T23:59:59.000Z

    In the solar corona, magnetic flux rope is believed to be a fundamental structure accounts for magnetic free energy storage and solar eruptions. Up to the present, the extrapolation of magnetic field from boundary data is the primary way to obtain fully three-dimensional magnetic information of the corona. As a result, the ability of reliable recovering coronal magnetic flux rope is important for coronal field extrapolation. In this paper, our coronal field extrapolation code (CESE-MHD-NLFFF, Jiang & Feng 2012) is examined with an analytical magnetic flux rope model proposed by Titov & Demoulin (1999), which consists of a bipolar magnetic configuration holding an semi-circular line-tied flux rope in force-free equilibrium. By using only the vector field in the bottom boundary as input, we test our code with the model in a representative range of parameter space and find that the model field is reconstructed with high accuracy. Especially, the magnetic topological interfaces formed between the flux rop...

  1. Collisionless magnetic reconnection in the presence of a sheared velocity field

    SciTech Connect (OSTI)

    Faganello, M. [Ecole Polytechnique, LPP, Palaiseau, 91128 (France); Pegoraro, F.; Califano, F. [Department of Physics, University of Pisa and CNISM, Pisa, 56127 (Italy); Marradi, L. [Department of Physics, University of Pisa and CNISM, Pisa, 56127 (Italy)] [Universite de Nice Sophia Antipolis, CNRS, Observatoire de la Cote d'Azur, 06304 Nice (France)

    2010-06-15T23:59:59.000Z

    The linear theory of magnetic field lines reconnection in a two-dimensional configuration in the presence of a (Kelvin-Helmholtz stable) sheared velocity field is investigated within a single fluid model, where the onset of magnetic field line reconnection is made possible by the effect of electron inertia in the so called large DELTA{sup '} regime.

  2. NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSSPRING EDITION VOLUME 13 N0. 2 2006

    E-Print Network [OSTI]

    Weston, Ken

    NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSSPRING EDITION VOLUME 13 · N0. 2 · 2006 SUPPORTED BY OF FLORIDA · LOS ALAMOS NATIONAL LABORATORY Pulsed Field Facility: Heat caPacity in tHe 20 t dilution ReFRigeRatoR tRiPle Resonance PRobe #12;NHMFLREPORTS C O N T E N T S Published by: National High Magnetic Field

  3. High Field Magnet R&D in the USA

    E-Print Network [OSTI]

    Gourlay, S.A.

    2011-01-01T23:59:59.000Z

    beam instmmentation, accelerator physics shIdies, and designShldy in terms of accelerator physics and magnet design.magnet technology and accelerator physics and approach the

  4. artificial magnetic fields: Topics by E-print Network

    Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

    Galea 2003-02-10 74 Magnetic anisotropy of elongated thin ferromagnetic nano-islands for artificial spin ice arrays Physics Websites Summary: Magnetic anisotropy of elongated thin...

  5. Gravitational waves interacting with a spinning charged particle in the presence of a uniform magnetic field

    E-Print Network [OSTI]

    D. B. Papadopoulos

    2003-12-23T23:59:59.000Z

    The equations which determine the response of a spinning charged particle moving in a uniform magnetic field to an incident gravitational wave are derived in the linearized approximation to general relativity. We verify that 1) the components of the 4-momentum, 4-velocity and the components of the spinning tensor, both electric and magnetic moments, exhibit resonances and 2) the co-existence of the uniform magnetic field and the GW are responsible for the resonances appearing in our equations. In the absence of the GW, the magnetic field and the components of the spin tensor decouple and the magnetic resonances disappear.

  6. On the delayed gas breakdown in a ringing theta-pinch with bias magnetic field

    SciTech Connect (OSTI)

    Meeks, Warner C.; Rovey, Joshua L. [Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409-0050 (United States)

    2012-05-15T23:59:59.000Z

    A single particle model and particle-in-cell simulations are used to elucidate the breakdown physics in a ringing theta-pinch with a bias magnetic field. Previous experimental results show that gas breakdown occurs when the bias magnetic field is nullified by the theta-pinch magnetic field. The analyses presented here agree with the experimental results and show that electron kinetic energy does not exceed the ionization threshold of deuterium until the net magnetic field is approximately zero. Despite the presence of a strong electric field, the gyromotion of electrons within the bias magnetic field prevents them from gaining energy necessary to ionize the gas. Parametric analysis of the peak electron energy as a function of the bias and pre-ionization magnetic fields reveals that: (1) when the bias magnetic field is Almost-Equal-To 97% of the pre-ionization magnetic field, peak electron energies are highly erratic resulting in poor overall ionization, and (2) full ionization with repeatable behavior requires a pre-ionization to bias magnetic field ratio of approximately 2 to 1 or higher.

  7. Assessing human exposure to power-frequency electric and magnetic fields

    SciTech Connect (OSTI)

    Kaune, W.T. [EM Factors, Richland, WA (United States)

    1993-12-01T23:59:59.000Z

    This paper reviews published literature and current problems relating to the assessment of occupational and residential human exposures to power-frequency electric and magnetic fields. Available occupational exposure data suggest that the class of job titles known as electrical workers may be an effective surrogate for time-weighted-average (TWA) magnetic-field (but not electric-field) exposure. Current research in occupational-exposure assessment is directed to the construction of job-exposure matrices based on electric- and magnetic-field measurements and estimates of worker exposures to chemicals and other factors of interest. Recent work has identified five principal sources of residential magnetic fields: electric power transmission lines, electric power distribution lines, ground currents, home wiring, and home appliances. Existing residential-exposure assessments have used one or more of the following techniques: questionnaires, wiring configuration coding, theoretical field calculations, spot electric- and magnetic-field measurements, fixed-site magnetic-field recordings, personal-exposure measurements, and geomagnetic-field measurements. Available normal-power magnetic-field data for residences differ substantially between studies. It is not known if these differences are due to geographical differences, differences in measurement protocols, or instrumentation differences. Available data suggest, but are far from proving, that spot measurements may be more effective than wire codes as predictors of long-term historical magnetic-field exposure. Two studies find that away-from-home TWA magnetic-field exposures are less variable than at home exposures. The importance of home appliances as contributors to total residential magnetic-field exposure is not known at this time. It also is not known what characteristics (if any) of residential electric and magnetic fields are determinants of human health effects. 41 refs., 9 figs., 10 tabs.

  8. NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSSUMMER EDITION VOLUME 13 N0. 3 2006

    E-Print Network [OSTI]

    Weston, Ken

    UPPort scientists neWs FroM tHe dc FieLd FaciLitY: QUantUM HaLL eFFect in graPHene at HigH Magnetic FieLds ed NEARING COMPLETION 14 NEWS FROM THE DC FIELD FACILITY QuantuM Hall effect In grapHene at HIgH MagnetIc f

  9. Apparatus and method for generating a magnetic field by rotation of a charge holding object

    DOE Patents [OSTI]

    Gerald, II, Rex E. (Brookfield, IL); Vukovic, Lela (Westchester, IL); Rathke, Jerome W. (Homer Glenn, IL)

    2009-10-13T23:59:59.000Z

    A device and a method for the production of a magnetic field using a Charge Holding Object that is mechanically rotated. In a preferred embodiment, a Charge Holding Object surrounding a sample rotates and subjects the sample to one or more magnetic fields. The one or more magnetic fields are used by NMR Electronics connected to an NMR Conductor positioned within the Charge Holding Object to perform NMR analysis of the sample.

  10. The Dependence of the Strength and Thickness of Field-Aligned Currents on Solar Wind and Ionospheric Parameters

    SciTech Connect (OSTI)

    Johnson, Jay R. [PPPL; Wing, Simon [Johns Hopkins University

    2014-08-01T23:59:59.000Z

    Sheared plasma flows at the low-latitude boundary layer correlate well with early afternoon auroral arcs and #12;eld-aligned currents [Sonnerup, 1980; Lundin and Evans, 1985]. We present a simple analytic model that relates solar wind and ionospheric parameters to the strength and thickness of field-aligned currents in a region of sheared velocity, such as the low latitude boundary layer. We compare the predictions of the model with DMSP observations and #12;nd remarkably good scaling of the currents with solar wind and ionospheric parameters. The sheared boundary layer thickness is inferred to be around 3000km consistent with observational studies. The analytic model provides a simple way to organize data and to infer boundary layer structures from ionospheric data.

  11. SU-E-J-233: A Facility for Radiobiological Experiments in a Large Magnetic Field

    SciTech Connect (OSTI)

    Carlone, M; Heaton, R; Keller, H [Princess Margaret Hospital, Toronto, ON (Canada); University of Toronto, Toronto, ON (Canada); Wouters, B [Ontario Cancer Institute, Toronto, ON (Canada); University of Toronto, Toronto, ON (Canada); Jaffray, D [Princess Margaret Hospital, Toronto, ON (Canada); Ontario Cancer Institute, Toronto, ON (Canada); University of Toronto, Toronto, ON (Canada)

    2014-06-01T23:59:59.000Z

    Purpose: There is considerable interest in developing medical linear accelerators with integrated image guidance by MRI. Less work has been done on the fundamental biology of cell survival in the presence of a strong magnetic field. The purpose of this work is to describe an experimental system capable of measuring cell survival response in the types of MRI-linac systems currently under development. Methods: We have integrated a cobalt irradiator with a solenoid magnet. The solenoid magnet has inner diameter of 10 cm. To enable measurement of the biological effects as a function of depth, we are utilizing the sliced gel technique, in which cells are embedded and fixed within a gelatin matrix. Irradiated cells at defined positions (sub mm resolution) can subsequently be recovered and assessed for cell survival or other biological effects. Results: The magnetic field profile in the solenoid has a peak magnetic field 36 cm below the top edge of the magnet bore and can be placed at and SAD of 100 cm. At a solenoid current of 35 A, the peak magnetic field is 0.25 T. The dose rate of the cobalt irradiator is 16 cGy/min at 100 cm SAD. EBT3 film was used to demonstrate the system functionality. It was irradiated at 1 cm depth at 100 cm SSD with a 4×4 field to 1.5 Gy in a 0.25 T magnetic field. The dose profile was similar between this film and the control exposure without magnetic field. Conclusion: Integrating a cobalt irradiator with a high field magnet is demonstrated. The magnetic field at the cobalt defining head was minimal and did not interfere with the functioning of this unit. Cell survival experiments can be reproduced exactly in the presence or absence of a magnetic field since a resistive magnet is used.

  12. Path Integral Confined Dirac Fermions in a Constant Magnetic Field

    E-Print Network [OSTI]

    Abdeldjalil Merdaci; Ahmed Jellal; Lyazid Chetouani

    2014-04-17T23:59:59.000Z

    We consider Dirac fermion confined in harmonic potential and submitted to a constant magnetic field. The corresponding solutions of the energy spectrum are obtained by using the path integral techniques. For this, we begin by establishing a symmetric global projection, which provides a symmetric form for the Green function. Based on this, we show that it is possible to end up with the propagator of the harmonic oscillator for one charged particle. After some transformations, we derive the normalized wave functions and the eigenvalues in terms of different physical parameters and quantum numbers. By interchanging quantum numbers, we show that our solutions possed interesting properties. The density of current and the non-relativistic limit are analyzed where different conclusions are obtained.

  13. Formation of current filaments and magnetic field generation in a quantum current-carrying plasma

    SciTech Connect (OSTI)

    Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of)] [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Taghadosi, M. R.; Majedi, S.; Khorashadizadeh, S. M. [Physics Department, University of Birjand, Birjand (Iran, Islamic Republic of)] [Physics Department, University of Birjand, Birjand (Iran, Islamic Republic of)

    2013-09-15T23:59:59.000Z

    The nonlinear dynamics of filamentation instability and magnetic field in a current-carrying plasma is investigated in the presence of quantum effects using the quantum hydrodynamic model. A new nonlinear partial differential equation is obtained for the spatiotemporal evolution of the magnetic field in the diffusion regime. This equation is solved by applying the Adomian decomposition method, and then the profiles of magnetic field and electron density are plotted. It is shown that the saturation time of filamentation instability increases and, consequently, the instability growth rate and the magnetic field amplitude decrease in the presence of quantum effects.

  14. Spectroscopic Determination of the Magnetic Fields in Exploding Wire and X-pinch Plasmas

    SciTech Connect (OSTI)

    Hammer, David A.

    2013-12-19T23:59:59.000Z

    In this report, we summarize the progress that was made toward developing a new magnetic field diagnostic known as Zeeman Broadening for current carrying high energy density plasmas.

  15. Origin of the resonant dependence of the instability current in a magnetic field

    SciTech Connect (OSTI)

    Nevirkovets, I.P.; Rudenko, E.M.

    1985-05-01T23:59:59.000Z

    The instability current in the case of Sn--I--Sn tunnel junctions in weak magnetic fields is investigated in detail. (AIP)

  16. Phase Transition in Ferromagnetic Ising Models with Non-Uniform External Magnetic Fields

    E-Print Network [OSTI]

    Rodrigo Bissacot; Leandro Cioletti

    2010-03-29T23:59:59.000Z

    In this article we study the phase transition phenomenon for the Ising model under the action of a non-uniform external magnetic field. We show that the Ising model on the hypercubic lattice with a summable magnetic field has a first-order phase transition and, for any positive (resp. negative) and bounded magnetic field, the model does not present the phase transition phenomenon whenever $\\liminf h_i> 0$, where ${\\bf h} = (h_i)_{i \\in \\Z^d}$ is the external magnetic field.

  17. MAGNETIC FIELD IN THE ISOLATED MASSIVE DENSE CLUMP IRAS 20126+4104

    SciTech Connect (OSTI)

    Shinnaga, Hiroko; Phillips, Thomas G. [California Institute of Technology Submillimeter Observatory, 111 Nowelo Street, Hilo, HI 96720 (United States); Novak, Giles [Department of Physics and Astronomy, Northwestern University, 633 Clark Street Evanston, IL 60208 (United States); Vaillancourt, John E. [Stratospheric Observatory for Infrared Astronomy, Universities Space Research Association, NASA Ames Research Center, Moffet Field, CA 94035 (United States); Machida, Masahiro N. [Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581 (Japan); Kataoka, Akimasa [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Tomisaka, Kohji [National Astronomical Observatory of Japan and Department of Astronomy, School of Physical Sciences, Graduate University for Advanced Studies (SOKENDAI), Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Davidson, Jacqueline; Houde, Martin [School of Physics, University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Perth (Australia); Dowell, C. Darren [Jet Propulsion Laboratory, California Institute of Technology, MS 169-506, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Leeuw, Lerothodi [SETI Institute, 515 North Whisman Avenue, Mountain View, CA 94043 (United States)

    2012-05-10T23:59:59.000Z

    We measured polarized dust emission at 350 {mu}m toward the high-mass star-forming massive dense clump IRAS 20126+4104 using the SHARC II Polarimeter, SHARP, at the Caltech Submillimeter Observatory. Most of the observed magnetic field vectors agree well with magnetic field vectors obtained from a numerical simulation for the case when the global magnetic field lines are inclined with respect to the rotation axis of the dense clump. The results of the numerical simulation show that rotation plays an important role on the evolution of the massive dense clump and its magnetic field. The direction of the cold CO 1-0 bipolar outflow is parallel to the observed magnetic field within the dense clump as well as the global magnetic field, as inferred from optical polarimetry data, indicating that the magnetic field also plays a critical role in an early stage of massive star formation. The large-scale Keplerian disk of the massive (proto)star rotates in an almost opposite sense to the clump's envelope. The observed magnetic field morphology and the counterrotating feature of the massive dense clump system provide hints to constrain the role of magnetic fields in the process of high-mass star formation.

  18. Dispersion relation and growth rate in a Cherenkov free electron laser: Finite axial magnetic field

    SciTech Connect (OSTI)

    Kheiri, Golshad; Esmaeilzadeh, Mahdi [Department of Physics, Iran University of Science and Technology, Tehran 16844 (Iran, Islamic Republic of)] [Department of Physics, Iran University of Science and Technology, Tehran 16844 (Iran, Islamic Republic of)

    2013-12-15T23:59:59.000Z

    A theoretical analysis is presented for dispersion relation and growth rate in a Cherenkov free electron laser with finite axial magnetic field. It is shown that the growth rate and the resonance frequency of Cherenkov free electron laser increase with increasing axial magnetic field for low axial magnetic fields, while for high axial magnetic fields, they go to a saturation value. The growth rate and resonance frequency saturation values are exactly the same as those for infinite axial magnetic field approximation. The effects of electron beam self-fields on growth rate are investigated, and it is shown that the growth rate decreases in the presence of self-fields. It is found that there is an optimum value for electron beam density and Lorentz relativistic factor at which the maximum growth rate can take place. Also, the effects of velocity spread of electron beam are studied and it is found that the growth rate decreases due to the electron velocity spread.

  19. Electron-cyclotron damping of helicon waves in low diverging magnetic fields

    SciTech Connect (OSTI)

    Lafleur, T.; Charles, C.; Boswell, R. W. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia)

    2011-04-15T23:59:59.000Z

    Particle-in-cell simulations are performed to investigate wave propagation and absorption behavior of low-field (B{sub 0}<5 mT) helicon waves in the presence of a diverging magnetic field. The 1D electromagnetic simulations, which include experimental external magnetic field profiles, provide strong evidence for electron-cyclotron damping of helicon waves in the spatially decaying nonuniform magnetic field. For a dipole-type magnetic field configuration, the helicon waves are absence in the downstream (lower field) region of the plasma and are observed to be completely absorbed. As the magnetic field is changed slightly however, wave damping decreases, and waves are able to propagate freely downstream, confirming previous experimental measurements of this phenomenon.

  20. Helium gas bubble trapped in liquid helium in high magnetic field

    SciTech Connect (OSTI)

    Bai, H., E-mail: bai@magnet.fsu.edu; Hannahs, S. T.; Markiewicz, W. D.; Weijers, H. W. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States)

    2014-03-31T23:59:59.000Z

    High magnetic field magnets are used widely in the area of the condensed matter physics, material science, chemistry, geochemistry, and biology at the National High Magnetic Field Laboratory. New high field magnets of state-of-the-art are being pursued and developed at the lab, such as the current developing 32?T, 32?mm bore fully superconducting magnet. Liquid Helium (LHe) is used as the coolant for superconducting magnets or samples tested in a high magnetic field. When the magnetic field reaches a relatively high value the boil-off helium gas bubble generated by heat losses in the cryostat can be trapped in the LHe bath in the region where BzdBz/dz is less than negative 2100 T{sup 2}/m, instead of floating up to the top of LHe. Then the magnet or sample in the trapped bubble region may lose efficient cooling. In the development of the 32?T magnet, a prototype Yttrium Barium Copper Oxide coil of 6 double pancakes with an inner diameter of 40?mm and an outer diameter of 140?mm was fabricated and tested in a resistive magnet providing a background field of 15?T. The trapped gas bubble was observed in the tests when the prototype coil was ramped up to 7.5?T at a current of 200?A. This letter reports the test results on the trapped gas bubble and the comparison with the analytical results which shows they are in a good agreement.

  1. Arrangement for measuring the field angle of a magnetic field as a function of axial position within a magnet bore tube

    DOE Patents [OSTI]

    Pidcoe, Stephen V. (Bonita, CA); Zink, Roger A. (Desoto, TX); Boroski, William N. (Aurora, IL); McCaw, William R. (Burr Ridge, IL)

    1993-01-01T23:59:59.000Z

    An arrangement for measuring the field angle of a magnetic field as a function of axial position within a magnet bore tube of a magnet such as is used with the Superconducting Super Collider (SSC). The arrangement includes a magnetic field alignment gauge that is carried through the magnet bore tube by a positioning shuttle in predetermined increments. The positioning shuttle includes an extensible body assembly which is actuated by an internal piston arrangement. A pair of spaced inflatable cuffs are carried by the body assembly and are selectively actuated in cooperation with pressurizing of the piston to selectively drive the positioning shuttle in an axial direction. Control of the shuttle is provided by programmed electronic computer means located exteriorly of the bore tube and which controls valves provided pressurized fluid to the inflatable cuss and the piston arrangement.

  2. Chiral dynamics in a magnetic field from the functional renormalization group

    E-Print Network [OSTI]

    Kazuhiko Kamikado; Takuya Kanazawa

    2014-03-13T23:59:59.000Z

    We investigate the quark-meson model in a magnetic field using the exact functional renormalization group equation beyond the local-potential approximation. Our truncation of the effective action involves anisotropic wave function renormalization for mesons, which allows us to investigate how the magnetic field distorts the propagation of neutral mesons. Solving the flow equation numerically, we find that the transverse velocity of mesons decreases with the magnetic field at all temperatures, which is most prominent at zero temperature. The meson screening masses and the pion decay constants are also computed. The constituent quark mass is found to increase with magnetic field at all temperatures, resulting in the crossover temperature that increases monotonically with the magnetic field. This tendency is consistent with most model calculations but not with the lattice simulation performed at the physical point. Our work suggests that the strong anisotropy of meson propagation may not be the fundamental origin of the inverse magnetic catalysis.

  3. Flavoured Large N Gauge Theory on a Compact Space with an External Magnetic Field

    E-Print Network [OSTI]

    Veselin G. Filev; Matthias Ihl

    2014-06-22T23:59:59.000Z

    The phase structure of flavoured N=2 SYM on a three sphere in an external magnetic field is studied. The pairing effect of the magnetic field competes with the dissociating effect of the Casimir free energy, leading to an interesting phase structure of confined and deconfined phases separated by a critical curve of a first order quantum phase transition. At vanishing magnetic field the phase transition is of a third order. For sufficiently strong magnetic field, the only stable phase is the confined phase and magnetic catalysis of chiral symmetry breaking is realized. The meson spectra of the theory exhibit Zeeman splitting and level crossing and feature a finite jump at the phase transition between the confined and deconfined phases. At strong magnetic field the ground state has a massless mode corresponding to the Goldstone boson associated with the spontaneously broken U(1) R-symmetry analogous to the eta' meson in QCD.

  4. Study of the electric field formation in a multi-cusped magnetic field

    SciTech Connect (OSTI)

    Liu, Hui, E-mail: hlying@gmail.com; Yu, Daren, E-mail: yudaren@hit.edu.cn [Lab of Plasma Propulsion, Mail Box 458, Harbin Institute of Technology (HIT), Harbin 150001 (China); Wu, Huan; Zhao, Yinjian; Ma, Chengyu; Wang, Di; Wei, Haoyu [School of Energy Science and Engineering, Harbin Institute of Technology (HIT), Harbin 150001 (China)

    2014-09-15T23:59:59.000Z

    The multi-cusped field thruster is a kind of electric thruster adopting a cusped magnetic field to achieve a potentially longer lifetime. It is observed in some experiments that the main electric potential drop forms near the exhaust plane, but the formation mechanism of the electric field in this kind of thrusters is not fully clear yet. Based on the analysis of the electron movement, a 2D Particle-in-Cell plus Monte Carlo model is built to reveal the difference of the constraint to electrons between the central leak path and the lateral region of the thruster. Electron trajectories from cathode are analyzed furthermore. It is found that the central leak path inside the discharge channel may play a significant role in the formation of the main electric potential drop near the exhaust plane.

  5. The spectral variability and magnetic field characteristics of the Of?p star HD 148937

    E-Print Network [OSTI]

    Wade, G A; Graefener, G; Howarth, I D; Martins, F; Petit, V; Vink, J S; Bagnulo, S; Folsom, C P; Nazé, Y; Walborn, N R; Townsend, R H D; Evans, C J

    2011-01-01T23:59:59.000Z

    We reportmagnetic and spectroscopic observations and modeling of the Of?p star HD 148937 within the context of theMagnetism in Massive Stars (MiMeS) Large Program at the Canada-France-Hawaii Telescope. Thirty-two high signal-to-noise ratio circularly polarised (Stokes V) spectra and 13 unpolarised (Stokes I) spectra of HD 148937 were acquired in 2009 and 2010. A definite detection of a Stokes V Zeeman signature is obtained in the grand mean of all observations (in both Least-Squares Deconvolved (LSD) mean profiles and individual spectral lines). The longitudinalmagnetic field inferred from the Stokes V LSD profiles is consistently negative, in contrast to the essentially zero field strength measured from the diagnostic null profiles. A period search of new and archival equivalent width measurements confirms the previously-reported 7.03 d variability period. The variation of equivalent widths is not strictly periodic: we present evidence for evolution of the amount or distribution of circumstellar plasma. Inte...

  6. Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma

    DOE Patents [OSTI]

    Woolley, Robert D. (Hillsborough, NJ)

    1998-01-01T23:59:59.000Z

    A method and apparatus for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring. A strain gauge is mounted on the first spring, and electronic means to continually monitor strain gauge resistance variations is provided. Electronic means for providing a known current pulse waveform to be periodically injected into each coil to create a time-varying torque on the rotor assembly in the toroidal direction causes mechanical strain variations proportional to the torque in the mounting means and springs so that strain gauge measurement of the variation provides periodic magnetic field measurements independent of the magnetic field measured by the electronic integrators.

  7. Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma

    DOE Patents [OSTI]

    Woolley, R.D.

    1998-09-08T23:59:59.000Z

    A method and apparatus are disclosed for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring. A strain gauge is mounted on the first spring, and electronic means to continually monitor strain gauge resistance variations is provided. Electronic means for providing a known current pulse waveform to be periodically injected into each coil to create a time-varying torque on the rotor assembly in the toroidal direction causes mechanical strain variations proportional to the torque in the mounting means and springs so that strain gauge measurement of the variation provides periodic magnetic field measurements independent of the magnetic field measured by the electronic integrators. 6 figs.

  8. Dynamics of the O(N) model in a strong magnetic background field as a modified noncommutative field theory

    SciTech Connect (OSTI)

    Jafari Salim, Amir [Department of Physics, Sharif University of Technology, P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of); Sadooghi, Neda [Institute for Studies in Theoretical Physics and Mathematics (IPM), School of Physics, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)

    2006-03-15T23:59:59.000Z

    In the presence of a strong magnetic field, the effective action of a composite scalar field in a scalar O(N) model is derived using two different methods. First, in the framework of world-line formalism, the 1PI n-point vertex function for the composites is determined in the limit of a strong magnetic field. Then, the n-point effective action of the composites is calculated in the regime of lowest Landau level dominance. It is shown that in the limit of a strong magnetic field, the results coincide and an effective field theory arises which is comparable with the conventional noncommutative field theory. In contrast to the ordinary case, however, the UV/IR mixing is absent in this modified noncommutative field theory.

  9. Nanoscale Diffusion Studies of Lipid Membranes National High Magnetic Field Laboratory

    E-Print Network [OSTI]

    Weston, Ken

    Magnetic Resonance Imaging & Spectroscopy User Facility, University of Florida Chemical Engineering We haveNanoscale Diffusion Studies of Lipid Membranes National High Magnetic Field Laboratory Advanced for the facility's future use. This will serve to enhance infrastructure for research and education at the Magnet

  10. SUMMERVOLUME 14 No.31 SUMMER 2007 VOLUME 14 NO. 3 NATIONAL HIGH MAGNETIC FIELD LABORATORY

    E-Print Network [OSTI]

    Weston, Ken

    a team of engineers capable of pushing magnetic fields to new highs? you already know the answer to announce that a key person who helped lead the magnet engineering team to world prominence no longer has of the Magnet Science & Technology group, as well as its chief engineer. In addition to keeping many balls

  11. THE BOUNDARY RIGIDITY PROBLEM IN THE PRESENCE OF A MAGNETIC FIELD

    E-Print Network [OSTI]

    Uhlmann, Gunther

    of reversible systems 36 6.4. Generic local boundary rigidity 38 Appendix A. Geometry of magnetic systems 42 A.1. Santal´o's formula 45 A.5. Index form of a magnetic geodesic 46 Appendix B. Study of a certain classTHE BOUNDARY RIGIDITY PROBLEM IN THE PRESENCE OF A MAGNETIC FIELD NURLAN S. DAIRBEKOV, GABRIEL P

  12. Cosmic rays and the magnetic field of the nearby starburst galaxy NGC 253

    E-Print Network [OSTI]

    V. Heesen; R. -J. Dettmar; M. Krause; R. Beck

    2008-01-23T23:59:59.000Z

    Using radio polarimetry we study the connection between the transport of cosmic rays (CR's), the three-dimensional magnetic field structure, and features of other ISM phases in the halo of NGC 253. We present a new sensitive radio continuum map of NGC 253 obtained from combined VLA and Effelsberg observations at lambda 6.2 cm. We find a prominent radio halo with a scaleheight of the thick radio disk of 1.7 kpc. The linear dependence between the local scaleheight of the vertical continuum emission and the cosmic ray electron (CRE) lifetime requires a vertical CR bulk speed of 270 km s^-1. The magnetic field structure of NGC 253 resembles an ``X''-shaped configuration where the orientation of the large-scale magnetic field is plane-parallel only in the inner regions of the disk and at small distances from the galactic midplane. At larger galactocentric radii and further away from the midplane the vertical component becomes important. This is most clearly visible at the location of the ``radio spur'' southeast of the nucleus, where the magnetic field orientation is almost vertical. We made a simple model for the dominant toroidal (r,phi) magnetic field component using a spiral magnetic field with prescribed inclination and pitch angle. The residual poloidal (r,phi,z) magnetic field component which was revealed by subtracting the model from the observations shows a distinct ``X''-shaped magnetic field orientation centered on the nucleus. The orientation angle of the poloidal magnetic field is consistent with a magnetic field transport described by the superposition of the vertical CR bulk speed and the rotation velocity. Hence, we propose a disk wind which transports cosmic rays, magnetic field, and (partially) ionized gas from the disk into the halo.

  13. ON THE AMPLIFICATION OF MAGNETIC FIELD BY A SUPERNOVA BLAST SHOCK WAVE IN A TURBULENT MEDIUM

    SciTech Connect (OSTI)

    Guo Fan; Li Shengtai; Li Hui; Li, David [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Giacalone, Joe; Jokipii, J. R. [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721 (United States)

    2012-03-10T23:59:59.000Z

    We have performed extensive two-dimensional magnetohydrodynamic simulations to study the amplification of magnetic fields when a supernova blast wave propagates into a turbulent interstellar plasma. The blast wave is driven by injecting high pressure in the simulation domain. The interstellar magnetic field can be amplified by two different processes, occurring in different regions. One is facilitated by the fluid vorticity generated by the 'rippled' shock front interacting with the background turbulence. The resulting turbulent flow keeps amplifying the magnetic field, consistent with earlier work. The other process is facilitated by the growth of the Rayleigh-Taylor instability at the contact discontinuity between the ejecta and the shocked medium. This can efficiently amplify the magnetic field and tends to produce the highest magnetic field. We investigate the dependence of the amplification on numerical parameters such as grid-cell size and on various physical parameters. We show that the magnetic field has a characteristic radial profile such that the downstream magnetic field gets progressively stronger away from the shock. This is because the downstream magnetic field needs a finite time to reach the efficient amplification, and will get further amplified in the Rayleigh-Taylor region. In our simulation, we do not observe a systematic strong magnetic field within a small distance to the shock. This indicates that if the magnetic-field amplification in supernova remnants indeed occurs near the shock front, other processes such as three-dimensional instabilities, plasma kinetics, and/or cosmic ray effect may need to be considered to explain the strong magnetic field in supernova remnants.

  14. Nonideal evolution of nonaxisymmetric, force-free magnetic fields in a magnetar

    E-Print Network [OSTI]

    Mastrano, Alpha

    2008-01-01T23:59:59.000Z

    Recent numerical magnetohydrodynamic calculations by Braithwaite and collaborators support the `fossil field' hypothesis regarding the origin of magnetic fields in compact stars and suggest that the resistive evolution of the fossil field can explain the reorganisation and decay of magnetar magnetic fields. Here, these findings are modelled analytically by allowing the stellar magnetic field to relax through a quasistatic sequence of nonaxisymmetric, force-free states, by analogy with spheromak relaxation experiments, starting from a random field. Under the hypothesis that the force-free modes approach energy equipartition in the absence of resistivity, the output of the numerical calculations is semiquantitatively recovered: the field settles down to a linked poloidal-toroidal configuration, which inflates and becomes more toroidal as time passes. A qualitatively similar (but not identical) end state is reached if the magnetic field evolves by exchanging helicity between small and large scales according to a...

  15. Nanoscale magnetic field mapping with a single spin scanning probe magnetometer

    SciTech Connect (OSTI)

    Rondin, L.; Tetienne, J.-P.; Spinicelli, P.; Roch, J.-F.; Jacques, V. [Laboratoire de Photonique Quantique et Moleculaire, Ecole Normale Superieure de Cachan and CNRS UMR 8537, 94235 Cachan Cedex (France); Dal Savio, C.; Karrai, K. [Attocube systems AG, Koeniginstrasse 11A RGB, Munich 80539 (Germany); Dantelle, G. [Laboratoire de Physique de la Matiere Condensee, Ecole Polytechnique and CNRS UMR 7643, 91128 Palaiseau (France); Thiaville, A.; Rohart, S. [Laboratoire de Physique des Solides, Universite Paris-Sud and CNRS UMR 8502, 91405 Orsay (France)

    2012-04-09T23:59:59.000Z

    We demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique on the electron spin resonance frequency of a single nitrogen-vacancy defect placed at the apex of an atomic force microscope tip. In addition, we report an all-optical magnetic imaging technique which is sensitive to large off-axis magnetic fields, thus extending the operation range of diamond-based magnetometry. Both techniques are illustrated by using a magnetic hard disk as a test sample. Owing to the non-perturbing and quantitative nature of the magnetic probe, this work should open up numerous perspectives in nanomagnetism and spintronics.

  16. Nonlinear force-free modeling of the solar coronal magnetic field

    E-Print Network [OSTI]

    T. Wiegelmann

    2008-01-18T23:59:59.000Z

    The coronal magnetic field is an important quantity because the magnetic field dominates the structure of the solar corona. Unfortunately direct measurements of coronal magnetic fields are usually not available. The photospheric magnetic field is measured routinely with vector magnetographs. These photospheric measurements are extrapolated into the solar corona. The extrapolated coronal magnetic field depends on assumptions regarding the coronal plasma, e.g. force-freeness. Force-free means that all non-magnetic forces like pressure gradients and gravity are neglected. This approach is well justified in the solar corona due to the low plasma beta. One has to take care, however, about ambiguities, noise and non-magnetic forces in the photosphere, where the magnetic field vector is measured. Here we review different numerical methods for a nonlinear force-free coronal magnetic field extrapolation: Grad-Rubin codes, upward integration method, MHD-relaxation, optimization and the boundary element approach. We briefly discuss the main features of the different methods and concentrate mainly on recently developed new codes.

  17. Effect of the terrestrial magnetic field on direct-current measurements in underground pipelines

    SciTech Connect (OSTI)

    Dzhala, R.M.; Dikmarova, L.P.; Kornienko, V.Yu.

    1995-12-01T23:59:59.000Z

    The effect of the secondary field of an underground pipeline, magnetized by the terrestrial magnetic field, on noncontacting measurements of direct current flowing in it is discussed. The systematic errors of three known measurement methods are compared. A method based on the measurement of the difference between the field components parallel to the terrestrial field component orthogonal to the pipline is identified as the most accurate. 5 refs., 3 figs.

  18. Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields

    DOE Patents [OSTI]

    Epstein, Arthur J. (Columbus, OH); Morin, Brian G. (Columbus, OH)

    1998-01-01T23:59:59.000Z

    The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors.

  19. Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields

    DOE Patents [OSTI]

    Epstein, A.J.; Morin, B.G.

    1998-10-13T23:59:59.000Z

    The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors. 21 figs.

  20. Presented by the National High Magnetic Field Laboratory

    E-Print Network [OSTI]

    Weston, Ken

    ! Cooling holes on the Bitter plates let cold water run through the magnet so it doesn't get too hot. l magnets found in houses. The answers will fit into the crossword puzzle below. ACROSS Where you store milk