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they are not comprehensive nor are they the most current set.
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1

Molecular gyroscopes and biological effects of weak ELF magnetic fields  

E-Print Network (OSTI)

Extremely-low-frequency magnetic fields are known to affect biological systems. In many cases, biological effects display `windows' in biologically effective parameters of the magnetic fields: most dramatic is the fact that relatively intense magnetic fields sometimes do not cause appreciable effect, while smaller fields of the order of 10--100 $\\mu$T do. Linear resonant physical processes do not explain frequency windows in this case. Amplitude window phenomena suggest a nonlinear physical mechanism. Such a nonlinear mechanism has been proposed recently to explain those `windows'. It considers quantum-interference effects on protein-bound substrate ions. Magnetic fields cause an interference of ion quantum states and change the probability of ion-protein dissociation. This ion-interference mechanism predicts specific magnetic-field frequency and amplitude windows within which biological effects occur. It agrees with a lot of experiments. However, according to the mechanism, the lifetime $\\Gamma^{-1}$ of ion ...

Savin, A V

2002-01-01T23:59:59.000Z

2

Bayesian inference of solar and stellar magnetic fields in the weak-field approximation  

E-Print Network (OSTI)

The weak-field approximation is one of the simplest models that allows us to relate the observed polarization induced by the Zeeman effect with the magnetic field vector present on the plasma of interest. It is usually applied for diagnosing magnetic fields in the solar and stellar atmospheres. A fully Bayesian approach to the inference of magnetic properties in unresolved structures is presented. The analytical expression for the marginal posterior distribution is obtained, from which we can obtain statistically relevant information about the model parameters. The role of a-priori information is discussed and a hierarchical procedure is presented that gives robust results that are almost insensitive to the precise election of the prior. The strength of the formalism is demonstrated through an application to IMaX data. Bayesian methods can optimally exploit data from filter-polarimeters given the scarcity of spectral information as compared with spectro-polarimeters. The effect of noise and how it degrades ou...

Ramos, A Asensio

2011-01-01T23:59:59.000Z

3

BAYESIAN INFERENCE OF SOLAR AND STELLAR MAGNETIC FIELDS IN THE WEAK-FIELD APPROXIMATION  

SciTech Connect

The weak-field approximation is one of the simplest models that allows us to relate the observed polarization induced by the Zeeman effect with the magnetic field vector present on the plasma of interest. It is usually applied for diagnosing magnetic fields in the solar and stellar atmospheres. A fully Bayesian approach to the inference of magnetic properties in unresolved structures is presented. The analytical expression for the marginal posterior distribution is obtained, from which we can obtain statistically relevant information about the model parameters. The role of a priori information is discussed and a hierarchical procedure is presented that gives robust results that are almost insensitive to the precise election of the prior. The strength of the formalism is demonstrated through an application to IMaX data. Bayesian methods can optimally exploit data from filter polarimeters given the scarcity of spectral information as compared with spectro-polarimeters. The effect of noise and how it degrades our ability to extract information from the Stokes profiles is analyzed in detail.

Asensio Ramos, A., E-mail: aasensio@iac.es [Instituto de Astrofisica de Canarias, 38205, La Laguna, Tenerife (Spain); Departamento de Astrofisica, Universidad de La Laguna, E-38205 La Laguna, Tenerife (Spain)

2011-04-10T23:59:59.000Z

4

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

E-Print Network (OSTI)

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.

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

2009-04-07T23:59:59.000Z

5

Enhanced collective focusing of intense neutralized ion beam pulses in the presence of weak solenoidal magnetic fields  

Science Conference Proceedings (OSTI)

The design of ion drivers for warm dense matter and high energy density physics applications and heavy ion fusion involves transverse focusing and longitudinal compression of intense ion beams to a small spot size on the target. To facilitate the process, the compression occurs in a long drift section filled with a dense background plasma, which neutralizes the intense beam self-fields. Typically, the ion bunch charge is better neutralized than its current, and as a result a net self-pinching (magnetic) force is produced. The self-pinching effect is of particular practical importance, and is used in various ion driver designs in order to control the transverse beam envelope. In the present work we demonstrate that this radial self-focusing force can be significantly enhanced if a weak (B {approx} 100 G) solenoidal magnetic field is applied inside the neutralized drift section, thus allowing for substantially improved transport. It is shown that in contrast to magnetic self-pinching, the enhanced collective self-focusing has a radial electric field component and occurs as a result of the overcompensation of the beam charge by plasma electrons, whereas the beam current becomes well-neutralized. As the beam leaves the neutralizing drift section, additional transverse focusing can be applied. For instance, in the neutralized drift compression experiments (NDCX) a strong (several Tesla) final focus solenoid is used for this purpose. In the present analysis we propose that the tight final focus in the NDCX experiments may possibly be achieved by using a much weaker (few hundred Gauss) magnetic lens, provided the ion beam carries an equal amount of co-moving neutralizing electrons from the preceding drift section into the lens. In this case the enhanced focusing is provided by the collective electron dynamics strongly affected by a weak applied magnetic field.

Dorf, Mikhail A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Davidson, Ronald C.; Kaganovich, Igor D.; Startsev, Edward A. [Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2012-05-15T23:59:59.000Z

6

Searching for a link between the presence of chemical spots on the surface of HgMn stars and their weak magnetic fields  

E-Print Network (OSTI)

We present the results of mapping the HgMn star AR Aur using the Doppler Imaging technique for several elements and discuss the obtained distributions in the framework of a magnetic field topology.

Savanov, I S; González, J F; Schöller, M

2009-01-01T23:59:59.000Z

7

Anomalous skin effects in relativistic parallel propagating weakly magnetized electron plasma waves  

SciTech Connect

Fully relativistic analysis of anomalous skin effects for parallel propagating waves in a weakly magnetized electron plasma is presented and general expressions for longitudinal and transverse permittivites are derived. It is found that the penetration depth for R- and L-waves increases as we move from non-relativistic to highly relativistic regime. The ambient magnetic field reduces/enhances the skin effects for R-wave/L-wave as the strength of the field is increased. In general, the weak magnetic field effects are pronounced for the weakly relativistic regime as compared with other relativistic cases. The results are also graphically illustrated. On switching off the magnetic field, previous results for field free case are retrieved [A. F. Alexandrov, A. S. Bogdankevich, and A. A. Rukhadze, Priniples of Plasma Electrodynamics (Springer-Verlag, Berlin, Heidelberg, 1984), Vol. 9, p. 106].

Abbas, Gohar; Bashir, M. F. [Salam Chair in Physics, G. C. University, Lahore 54000 (Pakistan); Department of Physics, G. C. University, Lahore 54000 (Pakistan); Murtaza, G. [Salam Chair in Physics, G. C. University, Lahore 54000 (Pakistan)

2011-10-15T23:59:59.000Z

8

Perpendicular propagating modes for weakly magnetized relativistic degenerate plasma  

SciTech Connect

Using the Vlasov-Maxwell system of equations, the dispersion relations for the perpendicular propagating modes (i.e., X-mode, O-mode, and upper hybrid mode) are derived for a weakly magnetized relativistic degenerate electron plasma. By using the density (n{sub 0}=p{sub F}{sup 3}/3{pi}{sup 2} Planck-Constant-Over-Two-Pi {sup 3}) and the magnetic field values for different relativistic degenerate environments, the propagation characteristics (i.e., cutoff points, resonances, dispersions, and band widths in k-space) of these modes are examined. It is observed that the relativistic effects suppress the effect of ambient magnetic field and therefore the cutoff and resonance points shift towards the lower frequency regime resulting in enhancement of the propagation domain. The dispersion relations of these modes for the non-relativistic limit (p{sub F}{sup 2} Much-Less-Than m{sub 0}{sup 2}c{sup 2}) and the ultra-relativistic limit (p{sub F}{sup 2} Much-Greater-Than m{sub 0}{sup 2}c{sup 2}) are also presented.

Abbas, Gohar; Bashir, M. F. [Salam Chair in Physics, G. C. University Lahore, Punjab 54000 (Pakistan); Department of Physics, G. C. University Lahore, Punjab 54000 (Pakistan); Murtaza, G. [Salam Chair in Physics, G. C. University Lahore, Punjab 54000 (Pakistan)

2012-07-15T23:59:59.000Z

9

Direct observation of dynamics of single spinning dust grains in weakly magnetized complex plasma  

SciTech Connect

The rotational dynamics of single dust grains in a weak magnetic field is investigated on a kinetic level. Experiments reveal spin-up of spherical dust grains and alignment of their magnetic moments parallel to the magnetic induction vector. The angular velocity of spinning prolate grains varies as magnetic induction increases to 250 G. Spinning dust grains are found to flip over only when the magnetic field magnitude is changing. The results demonstrate that dusty plasma has paramagnetic properties. Qualitative interpretations are proposed to explain newly discovered phenomena.

Dzlieva, E. S.; Karasev, V. Yu., E-mail: plasmadust@yandex.ru [St. Petersburg State University, Institute of Physics (Russian Federation); Petrov, O. F. [Russian Academy of Sciences, Institute for High Energy Densities, Joint Institute for High Temperatures (Russian Federation)

2012-01-15T23:59:59.000Z

10

Magnetic field generator  

DOE Patents (OSTI)

A magnetic field generating device provides a useful magnetic field within a specific retgion, while keeping nearby surrounding regions virtually field free. By placing an appropriate current density along a flux line of the source, the stray field effects of the generator may be contained. One current carrying structure may support a truncated cosine distribution, and it may be surrounded by a current structure which follows a flux line that would occur in a full coaxial double cosine distribution. Strong magnetic fields may be generated and contained using superconducting cables to approximate required current surfaces.

Krienin, Frank (Shoreham, NY)

1990-01-01T23:59:59.000Z

11

Giant magnetic effects and oscillations in antiferromagnetic Josephson weak links  

SciTech Connect

Josephson junctions with an antiferromagnetic metal as a link are described. The junction can be switched off by a relatively small magnetic field. The amplitude of the current oscillates as a function of the field.

Gorkov, L.; Kresin, Vladimir

2001-04-01T23:59:59.000Z

12

Traveling-wave tubes and backward-wave oscillators with weak external magnetic fields T. M. Abu-elfadl, G. S. Nusinovich, A. G. Shkvarunets, Y. Carmel, and T. M. Antonsen, Jr.  

E-Print Network (OSTI)

Research, University of Maryland at College Park, College Park, Maryland 20742-3511 D. Goebel Boeing EDD electrons and the axial electric field of the wave. Applying such a strong magnetic field requires heavy

Nusinovich, Gregory S.

13

The solar magnetic field  

E-Print Network (OSTI)

The magnetic field of the Sun is the underlying cause of the many diverse phenomena combined under the heading of solar activity. Here we describe the magnetic field as it threads its way from the bottom of the convection zone, where it is built up by the solar dynamo, to the solar surface, where it manifests itself in the form of sunspots and faculae, and beyond into the outer solar atmosphere and, finally, into the heliosphere. On the way it, transports energy from the surface and the subsurface layers into the solar corona, where it heats the gas and accelerates the solar wind.

Solanki, Sami K; Schüssler, Manfred; 10.1088/0034-4885/69/3/R02

2010-01-01T23:59:59.000Z

14

Astrophysical weak-interaction processes and nuclear effective field theory  

E-Print Network (OSTI)

Low-energy nuclear weak-interaction processes play important roles in many astrophysical contexts, and effective field theory is believed to be a highly useful framework for describing these processes in a model-independent manner. I present a brief account of the basic features of the nuclear effective theory approach, and some examples of actual calculations carried out in this method.

K. Kubodera

2004-04-09T23:59:59.000Z

15

Low field magnetic resonance imaging  

DOE Patents (OSTI)

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.

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

16

THE GALACTIC MAGNETIC FIELD  

Science Conference Proceedings (OSTI)

With this Letter, we complete our model of the Galactic magnetic field (GMF), by using the WMAP7 22 GHz total synchrotron intensity map and our earlier results to obtain a 13-parameter model of the Galactic random field, and to determine the strength of the striated random field. In combination with our 22-parameter description of the regular GMF, we obtain a very good fit to more than 40,000 extragalactic Faraday rotation measures and the WMAP7 22 GHz polarized and total intensity synchrotron emission maps. The data call for a striated component to the random field whose orientation is aligned with the regular field, having zero mean and rms strength Almost-Equal-To 20% larger than the regular field. A noteworthy feature of the new model is that the regular field has a significant out-of-plane component, which had not been considered earlier. The new GMF model gives a much better description of the totality of data than previous models in the literature.

Jansson, Ronnie; Farrar, Glennys R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY 10003 (United States)

2012-12-10T23:59:59.000Z

17

Giant magnetic effects and oscillations in antiferromagnetic Josephson weak links  

Science Conference Proceedings (OSTI)

Josephson junctions with an antiferromagnetic metal as a link are described. An especially interesting case is provided by a barrier built on a giant magnetoresistance multilayer or by using doped manganites in the metallic A-phase. Such a junction is predicted to display unusual properties. The junction can be switched off by a relatively small magnetic field. In addition, the amplitude of the Josephson current rapidly oscillates as a function of the field. {copyright} 2001 American Institute of Physics.

Gor {close_quote}kov, L.; Kresin, V.

2001-06-04T23:59:59.000Z

18

Fast superconducting magnetic field switch  

DOE Patents (OSTI)

The superconducting magnetic switch or fast kicker magnet is employed with an 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 than 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. Magnetic switches and particularly fast kicker magnets are used in the accelerator industry to quickly deflect particle beams into and out of various transport lines, storage rings, dumps, and specifically to differentially route individual bunches of particles from a train of bunches which are injected or ejected from a given ring.

Goren, Y.; Mahale, N.K.

1995-12-31T23:59:59.000Z

19

Fast superconducting magnetic field switch  

DOE Patents (OSTI)

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.

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

1996-01-01T23:59:59.000Z

20

Evolution of twisted magnetic fields  

SciTech Connect

The magnetic field of the solar corona evolves quasistatically in response to slowly changing photospheric boundary conditions. The magnetic topology is preserved by the low resistivity of the solar atmosphere. We show that a magnetic flux coordinate system simplifies the problem of calculating field evolution with invariant topology. As an example, we calculate the equilibrium of a thin magnetic flux tube with small twist per unit length.

Zweibel, E.G.; Boozer, A.H.

1985-02-01T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

MAGNETIC FIELDS FROM QCD PHASE TRANSITIONS  

SciTech Connect

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.

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

22

Magnetic-field-dosimetry system  

DOE Patents (OSTI)

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.

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

1981-01-21T23:59:59.000Z

23

Magnetic response to applied electrostatic field in external magnetic field  

E-Print Network (OSTI)

We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an applied electrostatic field. Referring to a simple example of a spherically-symmetric applied field, the nonlinearly induced current and its magnetic field are found explicitly throughout the space, the pattern of lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics.

T. C. Adorno; D. M. Gitman; A. E. Shabad

2013-11-16T23:59:59.000Z

24

Measurements of magnetic field alignment  

Science Conference Proceedings (OSTI)

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.

Kuchnir, M.; Schmidt, E.E.

1987-11-06T23:59:59.000Z

25

Cluster magnetic fields from active galactic nuclei  

E-Print Network (OSTI)

Active galactic nuclei (AGN) found at the centers of clusters of galaxies are a possible source for weak cluster-wide magnetic fields. To evaluate this scenario, we present 3D adaptive mesh refinement MHD simulations of a cool-core cluster that include injection of kinetic, thermal, and magnetic energy via an AGN-powered jet. Using the MHD solver in FLASH 2, we compare several sub-resolution approaches that link the estimated accretion rate as measured on the simulation mesh to the accretion rate onto the central black hole and the resulting feedback. We examine the effects of magnetized outflows on the accretion history of the black hole and discuss the ability of these models to magnetize the cluster medium.

Sutter, P M; Yang, H -Y

2009-01-01T23:59:59.000Z

26

Low-magnetic-field magnetars  

E-Print Network (OSTI)

It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these `magnetar candidates' exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (~4.4E+13 G). The recent discovery of fully-qualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarize the observational status of the low-magnetic-field magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.

Turolla, R

2013-01-01T23:59:59.000Z

27

Residential Transient Magnetic Field Research  

Science Conference Proceedings (OSTI)

Residential populations are exposed, in some measure, to transient magnetic fields. Such fields result from virtually all electric and electronic switching operations that may occur within the residence or external to the residence. This report presents the first phase of a study to better characterize these fields and, ultimately, describe their relationship to utility wiring configurations.

1994-03-01T23:59:59.000Z

28

BE condensates of weakly interacting bosons in gravity fields  

E-Print Network (OSTI)

The Bose-Einstein (BE) condensates of weakly interacting bosons in a strong gravity field, such as AGN (Active Galactic Nuclei), BHs (black holes) and neutron stars, are discussed. Being bound systems in gravity fields, these are stable reservoirs for the Higgs bosons, and vector bosons of Z and W as well as supersymmetric bosons. Upon gravitational disturbances, such as a gravitational collapse, these objects are relieved from the BE condensate bound states and decay or interact with each other freely. Using the repulsive nature of gravity at short distances which was obtained by the present author as quantum corrections to gravity, the particles produced by the decays or interactions of the bosons liberated from BE condensates can be emitted outside the horizon for our observation. It is suggested that the recently observed gamma ray peak at 129.8 +- 2.4 GeV from FERMI Large Area Telescope may be evidence for the existence of the Higgs boson condensates. The BE condensates of supersymmetric bosons are the most likely sources for the gamma rays from DMP (dark matter particle) and anti-DMP collisions. It is shown that the said process from DMPs spread in the galaxy is too small for the incident DMP with the intensity of the cosmic ray energy spectrum.

Yukio Tomozawa

2012-11-21T23:59:59.000Z

29

High Field Magnetic Resonance Facility  

NLE Websites -- All DOE Office Websites (Extended Search)

HFMRF Overview HFMRF Overview Section 2-3-1 High Field Magnetic Resonance Facility The High Field Magnetic Resonance Facility (HFMRF) focuses a significant portion of its research on developing a fundamental, molecular-level understanding of biochemical and biological systems and their response to environmental effects. A secondary focus is materials science, including catalysis and chemical mechanisms and processes. Staff and science consultants within this facility offer expertise in the areas of structural biology, solid-state materials characterization, and magnetic resonance imaging (MRI) techniques. Research activities in the HFMRF include: * structure determination of large molecular assemblies such as protein-DNA (normal and damaged DNA) and protein-RNA complexes

30

Magnetic Fields in Population III Star Formation  

DOE Green Energy (OSTI)

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.

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

2012-02-22T23:59:59.000Z

31

DISCIPLE-1: interactive apprentice system in weak theory fields  

Science Conference Proceedings (OSTI)

The paper presents an interactive approach to learning apprentice systems for weak theory domains. The approach consists of a combination of teaming by analogy and learning by generalizing instances. One main point of this approach is that it uses the ...

Yves Kodratoff; Gheorghe Tecuci

1987-08-01T23:59:59.000Z

32

Magnetic Vortex Core Reversal by Low-Field Excitations  

NLE Websites -- All DOE Office Websites (Extended Search)

Magnetic Vortex Core Reversal by Magnetic Vortex Core Reversal by Low-Field Excitations Magnetic Vortex Core Reversal by Low-Field Excitations Print Wednesday, 28 March 2007 00:00 In micrometer-sized magnetic thin films, the magnetization typically adopts an in-plane, circular configuration known as a magnetic vortex. At the vortex core, the magnetization turns sharply out of the plane, pointing either up or down. Magnetic data storage based on this binary phenomenon is an intriguing concept, but it would require the ability to flip the vortex cores on demand. Because these structures are highly stable, very strong magnetic fields of around half a tesla (approximately one-third the field of the strongest permanent magnet) were previously thought to be necessary to accomplish this. At the ALS, a team of researchers from Germany, Belgium, and the U.S. has used time-resolved scanning transmission x-ray microscopy (STXM) to observe vortex motion and demonstrate the feasibility of using weak magnetic fields as low as 1.5 millitesla (mT) to reverse the direction of a vortex core. The observed switching mechanism, which can be understood within the framework of micromagnetic theory, gives insights into basic magnetization dynamics and their possible application to data storage technologies.

33

High Field Magnet R&D |Superconducting Magnet Division  

NLE Websites -- All DOE Office Websites (Extended Search)

High Field Magnet R&D High Field Magnet R&D The Superconducting Magnet Division is developing advanced magnet designs and magnet-related technologies for high field accelerator magnets. We are currently working on magnets for three inter-related programs: High Field Magnets for Muon Collider Papers, Presentations Common Coil Magnets Papers, Presentations Interaction Region Magnets Papers, Presentations High Temperature Superconductor (HTS) Magnets Papers, Presentations This is part of a multi-lab superconducting magnet development program for new accelerator facilities that would be part of the U.S. High Energy Physics program. These programs (@BNL, @FNAL, @LBNL) are quite complimentary to each other, so that magnet designs and technologies developed at one laboratory can be easily transferred to another. The BNL

34

Magnetic Vortex Core Reversal by Low-Field Excitations  

NLE Websites -- All DOE Office Websites (Extended Search)

Magnetic Vortex Core Reversal by Low-Field Excitations Print Magnetic Vortex Core Reversal by Low-Field Excitations Print In micrometer-sized magnetic thin films, the magnetization typically adopts an in-plane, circular configuration known as a magnetic vortex. At the vortex core, the magnetization turns sharply out of the plane, pointing either up or down. Magnetic data storage based on this binary phenomenon is an intriguing concept, but it would require the ability to flip the vortex cores on demand. Because these structures are highly stable, very strong magnetic fields of around half a tesla (approximately one-third the field of the strongest permanent magnet) were previously thought to be necessary to accomplish this. At the ALS, a team of researchers from Germany, Belgium, and the U.S. has used time-resolved scanning transmission x-ray microscopy (STXM) to observe vortex motion and demonstrate the feasibility of using weak magnetic fields as low as 1.5 millitesla (mT) to reverse the direction of a vortex core. The observed switching mechanism, which can be understood within the framework of micromagnetic theory, gives insights into basic magnetization dynamics and their possible application to data storage technologies.

35

Magnetic Vortex Core Reversal by Low-Field Excitations  

NLE Websites -- All DOE Office Websites (Extended Search)

Magnetic Vortex Core Reversal by Low-Field Excitations Print Magnetic Vortex Core Reversal by Low-Field Excitations Print In micrometer-sized magnetic thin films, the magnetization typically adopts an in-plane, circular configuration known as a magnetic vortex. At the vortex core, the magnetization turns sharply out of the plane, pointing either up or down. Magnetic data storage based on this binary phenomenon is an intriguing concept, but it would require the ability to flip the vortex cores on demand. Because these structures are highly stable, very strong magnetic fields of around half a tesla (approximately one-third the field of the strongest permanent magnet) were previously thought to be necessary to accomplish this. At the ALS, a team of researchers from Germany, Belgium, and the U.S. has used time-resolved scanning transmission x-ray microscopy (STXM) to observe vortex motion and demonstrate the feasibility of using weak magnetic fields as low as 1.5 millitesla (mT) to reverse the direction of a vortex core. The observed switching mechanism, which can be understood within the framework of micromagnetic theory, gives insights into basic magnetization dynamics and their possible application to data storage technologies.

36

Magnetic Vortex Core Reversal by Low-Field Excitations  

NLE Websites -- All DOE Office Websites (Extended Search)

Magnetic Vortex Core Reversal by Low-Field Excitations Print Magnetic Vortex Core Reversal by Low-Field Excitations Print In micrometer-sized magnetic thin films, the magnetization typically adopts an in-plane, circular configuration known as a magnetic vortex. At the vortex core, the magnetization turns sharply out of the plane, pointing either up or down. Magnetic data storage based on this binary phenomenon is an intriguing concept, but it would require the ability to flip the vortex cores on demand. Because these structures are highly stable, very strong magnetic fields of around half a tesla (approximately one-third the field of the strongest permanent magnet) were previously thought to be necessary to accomplish this. At the ALS, a team of researchers from Germany, Belgium, and the U.S. has used time-resolved scanning transmission x-ray microscopy (STXM) to observe vortex motion and demonstrate the feasibility of using weak magnetic fields as low as 1.5 millitesla (mT) to reverse the direction of a vortex core. The observed switching mechanism, which can be understood within the framework of micromagnetic theory, gives insights into basic magnetization dynamics and their possible application to data storage technologies.

37

Separation of magnetic field lines  

SciTech Connect

The field lines of magnetic fields that depend on three spatial coordinates are shown to have a fundamentally different behavior from those that depend on two coordinates. Unlike two-coordinate cases, a flux tube in a magnetic field that depends on all three spatial coordinates that has a circular cross section at one location along the tube characteristically has a highly distorted cross section at other locations. In an ideal evolution of a magnetic field, the current densities typically increase. Crudely stated, if the current densities increase by a factor {sigma}, the ratio of the long to the short distance across a cross section of a flux tube characteristically increases by e{sup 2{sigma}}, and the ratio of the longer distance to the initial radius increases as e{sup {sigma}}. Electron inertia prevents a plasma from isolating two magnetic field structures on a distance scale shorter than c/{omega}{sub pe}, which is about 10 cm in the solar corona, and reconnection must be triggered if {sigma} becomes sufficiently large. The radius of the sun, R{sub Circled-Dot-Operator }=7 Multiplication-Sign 10{sup 10}cm is about e{sup 23} times larger, so when {sigma} Greater-Than-Or-Equivalent-To 23, two lines separated by c/{omega}{sub pe} at one location can be separated by the full scale of any magnetic structures in the corona at another. The conditions for achieving a large exponentiation, {sigma}, are derived, and the importance of exponentiation is discussed.

Boozer, Allen H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

2012-11-15T23:59:59.000Z

38

More about the hypothesis of a new weak interaction of electromagnetic field in the hidden sector  

E-Print Network (OSTI)

New hypothetical field equations (Eqs. (1) and (2)) are further discussed, unifying Maxwell's equations of the Standard Model (after the electroweak symmetry is spontaneously broken) with the dynamics of hidden sector (expected to be responsible for the cold dark matter). The hidden sector is represented by sterile spin-1/2 Dirac fermions ("sterinos") and sterile spin-0 bosons ("sterons") whose masses are spontaneously generated by a nonzero vacuum expectation value of the steron field, while sterino and steron interactions are mediated by sterile spin-1 quanta of an antisymmetric-tensor field with a large mass scale ("A bosons"). These interactions are presumed to be weak, but stronger than the universal gravity. Beside sterinos and sterons, the Standard-Model photons are included into the source of sterile A bosons and so, they become a link between the hidden and Standard-Model sectors ("photonic portal" to the hidden sector). The relativistic structure of antisymmetric-tensor field of sterile A bosons can be split into a vector and an axial three-dimensional fields (of spin 1 and parities - and +) in such a way that the Standard-Model electric and magnetic fields become involved separately in the sources of these two kinds of sterile A-boson radiation, respectively.

Wojciech Krolikowski

2009-03-30T23:59:59.000Z

39

Topological constraints in magnetic field relaxation  

E-Print Network (OSTI)

Stability and reconnection of magnetic fields play a fundamental role in natural and man-made plasma. In these applications the field's topology determines the stability of the magnetic field. Here I will describe the importance of one topology quantifier, the magnetic helicity, which impedes any free decay of the magnetic energy. Further constraints come from the fixed point index which hinders the field to relax into the Taylor state.

Candelaresi, Simon

2013-01-01T23:59:59.000Z

40

Active molecular plasma in a magnetic field  

SciTech Connect

The propagation of electromagnetic oscillations in an active molecules plasma in a constant external magnetic field is investigated. (AIP)

Kovtun, V.P.

1981-05-01T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Primordial magnetic field limits from cosmological data  

SciTech Connect

We study limits on a primordial magnetic field arising from cosmological data, including that from big bang nucleosynthesis, cosmic microwave background polarization plane Faraday rotation limits, and large-scale structure formation. We show that the physically relevant quantity is the value of the effective magnetic field, and limits on it are independent of how the magnetic field was generated.

Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Department of Physics, Laurentian University, Ramsey Lake Road, Sudbury, Ontario P3E 2C (Canada); Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Tevzadze, Alexander G. [Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Faculty of Exact and Natural Sciences, Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi, GE-0128 (Georgia); Sethi, Shiv K. [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Pandey, Kanhaiya [Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Ratra, Bharat [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States)

2010-10-15T23:59:59.000Z

42

The Solar Coronal Magnetic Field Measurements With SOLARC  

E-Print Network (OSTI)

Direct solar coronal magnetic field measurements have become possible since recent development of high-sensitivity infrared detection technology. The SOLARC instrument installed on Mt. Haleakala is such a polarimetric coronagraph that was designed for routinely observing Stokes parameter profiles in near infrared (NIR) wavelengthes. The Fe$^{+12}$ 1075 nm forbidden coronal emission line (CEL) is potential for weak coronal magnetic field detection. As a first step the potential field model has been used to compare with the SOLARC observation in the Fe$^{+12}$ 1075 nm line (Liu and Lin 2008). It's found that the potential fields can be a zeroth-order proxy for approaching the observed coronal field above a simple stable sunspot. In this paper we further discuss several nodi that are hampering the progress for reconstructing the real coronal magnetic field structures. They include the well-known Van Vleck effect in linear polarization signals, ignorance of the information of the NIR emission sources (i.e., inversion problem of coronal magnetic fields), a fat lot of global non-linear force-free field tools available for better modeling coronal magnetic fields, and so on.

Y. Liu; H. Lin

2008-09-04T23:59:59.000Z

43

Parallel heat transport in integrable and chaotic magnetic fields  

Science Conference Proceedings (OSTI)

The study of transport in magnetized plasmas is a problem of fundamental interest in controlled fusion, space plasmas, and astrophysics research. Three issues make this problem particularly challenging: (i) The extreme anisotropy between the parallel (i.e., along the magnetic field), {chi}{sub ||} , and the perpendicular, {chi}{sub Up-Tack }, conductivities ({chi}{sub ||} /{chi}{sub Up-Tack} may exceed 10{sup 10} in fusion plasmas); (ii) Nonlocal parallel transport in the limit of small collisionality; and (iii) Magnetic field lines chaos which in general complicates (and may preclude) the construction of magnetic field line coordinates. Motivated by these issues, we present a Lagrangian Green's function method to solve the local and non-local parallel transport equation applicable to integrable and chaotic magnetic fields in arbitrary geometry. The method avoids by construction the numerical pollution issues of grid-based algorithms. The potential of the approach is demonstrated with nontrivial applications to integrable (magnetic island), weakly chaotic (Devil's staircase), and fully chaotic magnetic field configurations. For the latter, numerical solutions of the parallel heat transport equation show that the effective radial transport, with local and non-local parallel closures, is non-diffusive, thus casting doubts on the applicability of quasilinear diffusion descriptions. General conditions for the existence of non-diffusive, multivalued flux-gradient relations in the temperature evolution are derived.

Castillo-Negrete, D. del; Chacon, L. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-8071 (United States)

2012-05-15T23:59:59.000Z

44

Neutron-Diffraction Evidence for the Ferrimagnetic Ground State of a Molecule-Based Magnet with Weakly Coupled Sublattices  

SciTech Connect

The diruthenium compound [Ru2(O2CMe)4]3[Cr(CN)6] contains two weakly coupled, ferrimag- netically ordered sublattices occupying the same volume. The magnetic field Hc 800 Oe required to align the two sublattice moments is proportional to the antiferromagnetic dipolar interaction Kc B Hc 5 10 3 meV between sublattices. Powder neutron-diffraction measurements on a deuterated sample reveal that the sublattice moments are restricted by the anisotropy of the diruthenium paddle-wheel complexes to the cubic diagonals. Those measurements also suggest that the quantum corrections to the ground state are significant.

Fishman, Randy Scott [ORNL; Campo, Javier [University of Zaragoza, Spain; Vos, Thomas E. [University of Utah; Miller, Joel S. [University of Utah

2012-01-01T23:59:59.000Z

45

Polarization bispectrum for measuring primordial magnetic fields  

E-Print Network (OSTI)

We examine the potential of polarization bispectra of the cosmic microwave background (CMB) to constrain primordial magnetic fields (PMFs). We compute all possible bispectra between temperature and polarization anisotropies sourced by PMFs and show that they are weakly correlated with well-known local-type and secondary ISW-lensing bispectra. From a Fisher analysis it is found that, owing to E-mode bispectra, in a cosmic-variance-limited experiment the expected uncertainty in the amplitude of magnetized bispectra is 80% improved in comparison with an analysis in terms of temperature auto-bispectrum alone. In the $\\mathit{Planck}$ or the proposed PRISM experiment cases, we will be able to measure PMFs with strength 2.6 or 2.2 nG. PMFs also generate bispectra involving B-mode polarization, due to tensor-mode dependence. We also find that the B-mode bispectrum can reduce the uncertainty more drastically and hence PMFs comparable to or less than 1 nG may be measured in a PRISM-like experiment.

Maresuke Shiraishi

2013-08-12T23:59:59.000Z

46

Bipolar pulse field for magnetic refrigeration  

DOE Patents (OSTI)

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.

Lubell, M.S.

1994-10-25T23:59:59.000Z

47

Tiny, Atom-based Detector Senses Weak Magnetic Fields  

Science Conference Proceedings (OSTI)

... miniature magnetometer is sensitive enough to detect a concealed rifle about 12 meters (40 feet) away or a six-inch-diameter steel pipeline up to ...

2012-04-16T23:59:59.000Z

48

Magnetic Braiding and Parallel Electric Fields  

E-Print Network (OSTI)

The braiding of the solar coronal magnetic field via photospheric motions - with subsequent relaxation and magnetic reconnection -- is one of the most widely debated ideas of solar physics. We readdress the theory in the light of developments in three-dimensional magnetic reconnection theory. It is known that the integrated parallel electric field along field lines is the key quantity determining the rate of reconnection, in contrast with the two-dimensional case where the electric field itself is the important quantity. We demonstrate that this difference becomes crucial for sufficiently complex magnetic field structures. A numerical method is used to relax a braided magnetic field to an ideal force-free equilibrium; that equilibrium is found to be smooth, with only large- scale current structures. However, the equilibrium is shown to have a highly filamentary integrated parallel current structure with extremely short length- scales. An analytical model is developed to show that, in a coronal situation, the length scales associated with the integrated parallel current structures will rapidly decrease with increasing complexity, or degree of braiding, of the magnetic field. Analysis shows the decrease in these length scales will, for any finite resistivity, eventually become inconsistent with the stability of a force- free field. Thus the inevitable consequence of the magnetic braiding process is shown to be a loss of equilibrium of the coronal field, probably via magnetic reconnection events.

A. L. Wilmot-Smith; G. Hornig; D. I. Pontin

2008-10-08T23:59:59.000Z

49

Graphene Nanoribbon in Sharply Localized Magnetic Fields  

E-Print Network (OSTI)

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.

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

2011-03-21T23:59:59.000Z

50

Spatial energy spectrum of primordial magnetic fields  

E-Print Network (OSTI)

Here, we analyze the primordial magnetic field transition between a radiative and a matter-dominated universe. The gravitational structure formation affects its evolution and energy spectrum. The structure excitation can trigger magnetic field amplification and the steepening of its energy density spectrum.

Grazyna Siemieniec-Ozieblo

2004-10-04T23:59:59.000Z

51

Permanent magnet edge-field quadrupole  

DOE Patents (OSTI)

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.

Tatchyn, Roman O. (Mountain View, CA)

1997-01-01T23:59:59.000Z

52

On Color Superconductivity in External Magnetic Field  

E-Print Network (OSTI)

We study color superconductivity in external magnetic field. We discuss the reason why the mixing angles in color-flavor locked (CFL) and two-flavor superconductivity (2SC) phases are different despite the fact that the CFL gap goes to the 2SC gap for $m_s \\to \\infty$. Although flavor symmetry is explicitly broken in external magnetic field, we show that all values of gaps in their coset spaces of possible solutions in the CFL phase are equivalent in external magnetic field.

E. V. Gorbar

2000-01-20T23:59:59.000Z

53

Meson Spectrum in Strong Magnetic Fields  

E-Print Network (OSTI)

We study the relativistic quark-antiquark system embedded in magnetic field. The Hamiltonian containing confinement, one gluon exchange and spin-spin interaction is derived. We analytically follow the evolution of the lowest meson states as a functions of MF strength. Calculating the one gluon exchange interaction energy and spin-spin contribution we have observed, that these corrections remain finite at large magnetic fields, preventing the vanishing of the total rho-meson mass at some B_crit, as previously thought. We display the rho masses as functions of magnetic field in comparison with recent lattice data.

M. A. Andreichikov; B. O. Kerbikov; V. D. Orlovsky; Yu. A. Simonov

2013-04-09T23:59:59.000Z

54

Fluctuations in the Gravitational, Strong and Weak Nuclear Fields through an Effective Harmonic Oscillator Model  

E-Print Network (OSTI)

We propose an effective harmonic oscillator model in order to treat the fluctuations of the gravitational, strong and weak nuclear fields. With respect to the gravitational field, first we use the model to estimate its fluctuating strength, necessary to decohere the wavefunction of a cubic centimeter of air at the standard temperature and pressure conditions. Second, the fluctuation of a point mass through a distance equal to the Planck length leads to the self-gravitational interaction of a particle, which can be related to its de Broglie frequency. Third, by making the equality of the fluctuating field strength with the gravitational field of a mass M at half of its Schwarzschild radius, we obtain an estimate of the mass of the Universe. We also consider the fluctuations of the strong nuclear field, as a means to estimate the separation in energy between the ground state and the centroid of the excitated states of the nucleon. Finally, taking into account the neutron-proton mass difference, we use the fluctuations of the weak nuclear field in order to evaluate the weak coupling constant.

P. R. Silva

2001-12-10T23:59:59.000Z

55

Magnetic field gradient effects on Rayleigh-Taylor instability with continuous magnetic field and density profiles  

SciTech Connect

In this paper, the effects of magnetic field gradient (i.e., the magnetic field transition layer effects) on the Rayleigh-Taylor instability (RTI) with continuous magnetic field and density profiles are investigated analytically. The transition layers of magnetic field and density with two different typical profiles are studied and the analytic expressions of the linear growth rate of the RTI are obtained. It is found that the magnetic field effects strongly reduce the linear growth rate of the RTI, especially when the perturbation wavelength is short. The linear growth rate of the RTI increases with the thickness of the magnetic field transition layer, especially for the case of small thickness of the magnetic field transition layer. When the magnetic field transition layer width is long enough, the linear growth rate of the RTI can be saturated. Thus when one increases the width of the magnetic field transition layer, the linear growth rate of the RTI increases only in a certain range, which depends on the magnetic field strength. The numerical results are compared with the analytic linear growth rates and they agree well with each other.

Yang, B. L. [Graduate School, China Academy of Engineering Physics, Beijing 100088 (China); Wang, L. F.; Ye, W. H. [HEDPS and CAPT, Peking University, Beijing 100871 (China); LCP, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Xue, C. [LCP, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

2011-07-15T23:59:59.000Z

56

Magnetic Field Measurements and Analysis For an Aladdin Dipole Magnet  

NLE Websites -- All DOE Office Websites (Extended Search)

Field Measurements and Analysis Field Measurements and Analysis For an Aladdin Dipole Magnet by Kenneth M. Thompson Electromagnetic Technology Program Argonne National Laboratory Argonne, 1L 60439 L8-40 November 21, 1985 Table of Contents Summary i A. Introduction *..*.**.***.....****...**.*..*...*..***.......*..... 1 1. Magnet Description 2. Measuring System 3. Data Descriptions 1 1 3 B. Equipment **********************.***.******.*************..******* 5 1. Probe Positioning System a. Description b. Calibration 2. Field Probe a. Calibration b. Probe Center 1. Method 2. Repeatability c. Hall Gaussmeter Parameters 3. Auxiliary Probes 4. Optical Alignment Equipment 5. Power Supply 6. Magnet Cooling Water System 7. Support a. Magnet b. Manipulator 5 5 7 7 8 9 9 9 10 10 13 13

57

Lunar magnetic field measurements with a cubesat  

E-Print Network (OSTI)

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 ...

Garrick-Bethell, Ian

58

Effects of Magnetic Field on Micro Flames.  

E-Print Network (OSTI)

??The effect of a gradient magnetic field on a diffusion micro flame i.e. C3H8/air flame has been systematically studied to comprehend their interaction. A non-uniform… (more)

Swaminathan, Sumathi

2005-01-01T23:59:59.000Z

59

Laminated magnet field coil sheath  

DOE Patents (OSTI)

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.

Skaritka, J.R.

1987-05-15T23:59:59.000Z

60

Magnetic Fields from Electrical Appliances and Devices  

Science Conference Proceedings (OSTI)

A major emphasis of research addressing potential health effects associated with power-frequency magnetic fields has been on assessing exposure to magnetic fields attributable to loads and their associated ground currents flowing on electrical transmission and distribution systems. Though these exposures can vary widely both over time and among residences, they are nonetheless present virtually all of the time. These exposures have remained a focus of attention for the scientific community largely becaus...

2010-09-28T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Magnetic field transfer device and method  

DOE Patents (OSTI)

A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180[degree] from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180[degree] from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils. 16 figs.

Wipf, S.L.

1990-02-13T23:59:59.000Z

62

Magnetic Fields in Stellar Astrophysics  

E-Print Network (OSTI)

This is a white paper submitted to the Stars and Stellar Evolution (SSE) Science Frontier Panel (SFP) of the NRC's 2010 Astronomy and Astrophysics Decadal Survey. The white paper is endorsed by the NSF Physics Frontier Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas (CMSO).

Uzdensky, Dmitri; Ji, Hantao; Townsend, Richard; Yamada, Masaaki

2009-01-01T23:59:59.000Z

63

HEAT CAPACITY MEASUREMENTS IN PULSED MAGNETIC FIELDS  

E-Print Network (OSTI)

(World Scientific, to be published) The new NHMFL 60T quasi-continuous magnet produces a flat-top field for a period of 100 ms at 60 Tesla, and for longer time at lower fields, e.g. 0.5 s at 35 Tesla. We have developed for the first time the capability to measure heat capacity at very high magnetic fields in the NHMFL 60T quasi-continuous magnet at LANL, using a probe built out of various plastic materials. The field plateau allows us to utilize a heat-pulse method to obtain heat capacity data. Proof-of-principle heat capacity experiments were performed on a variety of correlated electron systems. Both magnet performance characteristics and physical properties of various materials studied hold out a promise of wide application of this new tool. 1 I. TECHNIQUE The 60 Tesla Long-Pulse (60TLP) magnet was recently commissioned at the Los Alamos National Laboratory. This magnet produces a flat-top field for a period of 100 ms at 60

M. Jaime; R. Movshovich; J. L. Sarrao; J. Kim; G. Stewart; W. P. Beyermann

1999-01-01T23:59:59.000Z

64

New magnetic field measurements of beta Cephei stars and Slowly Pulsating B stars  

E-Print Network (OSTI)

We present the results of the continuation of our magnetic survey with FORS1 at the VLT of a sample of B-type stars consisting of confirmed or candidate beta Cephei stars and Slowly Pulsating B (hereafter SPB) stars, along with a small number of normal B-type stars. A weak mean longitudinal magnetic field of the order of a few hundred Gauss was detected in three beta Cephei stars and two stars suspected to be beta Cephei stars, in five SPB stars and eight stars suspected to be SPB stars. Additionally, a longitudinal magnetic field at a level larger than 3sigma has been diagnosed in two normal B-type stars, the nitrogen-rich early B-type star HD52089 and in the B5 IV star HD153716. Roughly one third of beta Cephei stars have detected magnetic fields: Out of 13 beta Cephei stars studied to date with FORS1, four stars possess weak magnetic fields, and out of the sample of six suspected beta Cephei stars two show a weak magnetic field. The fraction of magnetic SPBs and candidate SPBs is found to be higher: roughl...

Hubrig, S; De Cat, P; Schöller, M; Morel, T; Ilyin, I

2009-01-01T23:59:59.000Z

65

Magnetic nanoparticles for applications in oscillating magnetic field  

DOE Green Energy (OSTI)

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.

Peeraphatdit, Chorthip

2010-12-15T23:59:59.000Z

66

Critical Magnetic Field Determination of Superconducting Materials  

Science Conference Proceedings (OSTI)

Superconducting RF technology is becoming more and more important. With some recent cavity test results showing close to or even higher than the critical magnetic field of 170-180 mT that had been considered a limit, it is very important to develop a way to correctly measure the critical magnetic field (H{sup RF}{sub c}) of superconductors in the RF regime. Using a 11.4 GHz, 50-MW, electric field at the sample surface. A model of the system is presented in this paper along with a discussion of preliminary experimental data.

Canabal, A.; Tajima, T.; /Los Alamos; Dolgashev, V.A.; Tantawi, S.G.; /SLAC; Yamamoto, T.; /Tsukuba, Natl. Res. Lab. Metrol.

2011-11-04T23:59:59.000Z

67

An Einstein-like theory of gravity with a non-newtonian weak-field limit  

E-Print Network (OSTI)

We propose a model describing Einstein gravity coupled to a scalar field with an exponential potential. We show that the weak-field limit of the model has static solutions given by a gravitational potential behaving for large distances as \\ln r . The Newtonian term GM/r appears only as subleading. Our model can be used to give a phenomenological explanation of the rotation curves of the galaxies without postulating the presence of dark matter. This can be achieved only by giving up at galactic scales Einstein equivalence principle.

Mariano Cadoni

2003-12-09T23:59:59.000Z

68

Photon Redshift in a Magnetic field  

E-Print Network (OSTI)

Previous results from the authors concerning the arising a tiny photon anomalous paramagnetic moment are also interpreted as a red-shift in analogy to the gravitational known effect. It is due to the photon interaction with the magnetized virtual electron-positron background which withdraw transverse momentum from photons and is polarization-dependent. If the photon frequency red-shift implies a change in time, a clock would go faster for increasing magnetic field intensity.

Rojas, H Pérez

2010-01-01T23:59:59.000Z

69

Photon Splitting and Pair Conversion in Strong Magnetic Fields  

E-Print Network (OSTI)

The magnetospheres of neutron stars provide a valuable testing ground for as-yet unverified theoretical predictions of quantum electrodynamics (QED) in strong electromagnetic fields. Exhibiting magnetic field strengths well in excess of a TeraGauss, such compact astrophysical environments permit the action of exotic mechanisms that are forbidden by symmetries in field-free regions. Foremost among these processes are single-photon pair creation, where a photon converts to an electron-positron pair, and magnetic photon splitting, where a single photon divides into two of lesser energy via the coupling to the external field. The pair conversion process is exponentially small in weak fields, and provides the leading order contribution to vacuum polarization. In contrast, photon splitting possesses no energy threshold and can operate in kinematic regimes where the lower order pair conversion is energetically forbidden. This paper outlines some of the key physical aspects of these processes, and highlights their manifestation in neutron star magnetospheres. Anticipated observational signatures include profound absorption turnovers in pulsar spectra at gamma-ray wavelengths. The shapes of these turnovers provide diagnostics on the possible action of pair creation and the geometrical locale of the photon emission region. There is real potential for the first confirmation of strong field QED with the new GLAST mission, to be launched by NASA in 2008. Suppression of pair creation by photon splitting and its implications for pulsars is also discussed.

Matthew G. Baring

2008-04-05T23:59:59.000Z

70

The Energy Eigenvalues of the Two Dimensional Hydrogen Atom in a Magnetic Field  

E-Print Network (OSTI)

In this paper, the energy eigenvalues of the two dimensional hydrogen atom are presented for the arbitrary Larmor frequencies by using the asymptotic iteration method. We first show the energy eigenvalues for the no magnetic field case analytically, and then we obtain the energy eigenvalues for the strong and weak magnetic field cases within an iterative approach for $n=2-10$ and $m=0-1$ states for several different arbitrary Larmor frequencies. The effect of the magnetic field on the energy eigenvalues is determined precisely. The results are in excellent agreement with the findings of the other methods and our method works for the cases where the others fail.

A. Soylu; O. Bayrak; I. Boztosun

2007-03-13T23:59:59.000Z

71

SQUID-Detected NMR and MRI at Ultralow Magnetic Fields  

By combining the use of supersensitive magnetic field detecting Superconducting QUantum Interference Devices (SQUIDS) with ...

72

Bound states in a strong magnetic field  

SciTech Connect

We expect a strong magnetic field to be produced in the perpendicular direction to the reaction plane, in a noncentral heavy-ion collision . The strength of the magnetic field is estimated to be eB{approx}m{sup 2}{sub {pi}}{approx} 0.02 GeV{sup 2} at the RHIC and eB{approx} 15m{sup 2}{sub {pi}}{approx} 0.3 GeV{sup 2} at the LHC. We investigate the effects of the magnetic field on B{sup 0} and D{sup 0} mesons, focusing on the changes of the energy levels and of the mass of the bound states.

Machado, C. S.; Navarra, F. S.; Noronha, J.; Oliveira, E. G. [Instituto de Fisica, Universidade de Sao Paulo Rua do Matao, Travessa R, 187, 05508-090 Sao Paulo, SP (Brazil); Ferreira Filho, L. G. [Departamento de Matematica e Computacao, Faculdade de Tecnologia, Universidade do Estado do Rio de Janeiro Rodovia Presidente Dutra, km 298, Polo Industrial, CEP 27537-000, Resende, RJ (Brazil)

2013-03-25T23:59:59.000Z

73

Evolution of primordial magnetic fields in mean-field approximation  

E-Print Network (OSTI)

We study the evolution of phase-transition-generated cosmic magnetic fields coupled to the primeval cosmic plasma in turbulent and viscous free-streaming regimes. The evolution laws for the magnetic energy density and correlation length, both in helical and non-helical cases, are found by solving the autoinduction and Navier-Stokes equations in mean-field approximation. Analytical results are derived in Minkowski spacetime and then extended to the case of a Friedmann universe with zero spatial curvature, both in radiation and matter dominated eras. The three possible viscous free-streaming phases are characterized by a drag term in the Navier-Stokes equation which depends on the free-steaming properties of neutrinos, photons, or hydrogen atoms, respectively. In the case of non-helical magnetic fields, the magnetic intensity $B$ and the magnetic correlation length $\\xi_B$ evolve asymptotically with the temperature $T$ as $B(T) \\simeq \\kappa_B (N_i v_i)^{\\varrho_1} (T/T_i)^{\\varrho_2}$ and $\\xi_B(T) \\simeq \\kap...

Campanelli, Leonardo

2013-01-01T23:59:59.000Z

74

Generation of Strong Magnetic Fields in Axisymmetry by the Stationary Accretion Shock Instability  

E-Print Network (OSTI)

We begin an exploration of the capacity of the stationary accretion shock instability (SASI) to generate magnetic fields by adding a weak, stationary, and radial (but bipolar) magnetic field to a spherically symmetric fluid configuration that models a stalled shock in the post-bounce supernova environment. Upon perturbation the SASI develops, and its lateral flows alternately advect the initially radial magnetic field towards and away from the polar regions. Lateral flows into the polar regions result in partially radial outflows along the symmetry axis, and over several SASI cycles the magnetic field parallel to the axis grows--{\\em even in the absence of rotation}--to dynamical significance ($\\gtrsim 10^{15}$ G), finally saturating upon local equipartition in the polar regions. While the resulting field configuration creates low-density `funnels' and enables energy transport along the field through MHD waves, it does not induce qualitatively new features in the global evolution of the shock.

Endeve, Eirik; Budiardja, Reuben D; Mezzacappa, Anthony

2008-01-01T23:59:59.000Z

75

Strain sensors for high field pulse magnets  

Science Conference Proceedings (OSTI)

In this paper we present an investigation into several strain sensing technologies that are being considered to monitor mechanical deformation within the steel reinforcement shells used in high field pulsed magnets. Such systems generally operate at cryogenic temperatures to mitigate heating issues that are inherent in the coils of nondestructive, high field pulsed magnets. The objective of this preliminary study is to characterize the performance of various strain sensing technologies at liquid nitrogen temperatures (-196 C). Four sensor types are considered in this investigation: fiber Bragg gratings (FBG), resistive foil strain gauges (RFSG), piezoelectric polymers (PVDF), and piezoceramics (PZT). Three operational conditions are considered for each sensor: bond integrity, sensitivity as a function of temperature, and thermal cycling effects. Several experiments were conducted as part of this study, investigating adhesion with various substrate materials (stainless steel, aluminum, and carbon fiber), sensitivity to static (FBG and RFSG) and dynamic (RFSG, PVDF and PZT) load conditions, and sensor diagnostics using PZT sensors. This work has been conducted in collaboration with the National High Magnetic Field Laboratory (NHMFL), and the results of this study will be used to identify the set of sensing technologies that would be best suited for integration within high field pulsed magnets at the NHMFL facility.

Martinez, Christian [Los Alamos National Laboratory; Zheng, Yan [Los Alamos National Laboratory; Easton, Daniel [Los Alamos National Laboratory; Farinholt, Kevin M [Los Alamos National Laboratory; Park, Gyuhae [Los Alamos National Laboratory

2009-01-01T23:59:59.000Z

76

Evaluation of Occupational Magnetic Field Exposure Guidelines  

Science Conference Proceedings (OSTI)

As a first step in assessing potential effects of EMF exposure guidelines on utility operations, EPRI sponsored a technical evaluation of the major occupational EMF exposure guidelines and an analysis of existing magnetic-field exposure databases. The research reported herein is a comprehensive extension of that work, that includes studies by several research groups on diverse topics related to guidelines.

1998-12-15T23:59:59.000Z

77

Phase space structure of the electron diffusion region in reconnection with weak guide fields  

Science Conference Proceedings (OSTI)

Kinetic simulations of magnetic reconnection provide detailed information about the electric and magnetic structure throughout the simulation domain, as well as high resolution profiles of the essential fluid parameters including the electron and ion densities, flows, and pressure tensors. However, the electron distribution function, f(v), within the electron diffusion region becomes highly structured in the three dimensional velocity space and is not well resolved by the data available from the particle-in-cell (PIC) simulations. Here, we reconstruct the electron distribution function within the diffusion region at enhanced resolution. This is achieved by tracing electron orbits in the fields taken from PIC simulations back to the inflow region where an analytic form of the magnetized electron distribution is known. For antiparallel reconnection, the analysis reveals the highly structured nature of f(v), with striations corresponding to the number of times electrons have been reflected within the reconnection current layer, and exposes the origin of gradients in the electron pressure tensor important for momentum balance. The structure of the reconnection region is strongly tied to the pressure anisotropy that develops in the electrons upstream of the reconnection region. The addition of a guide field changes the nature of the electron distributions, and the differences are accounted for by studying the motion of single particles in the field geometry. Finally, the geometry of small guide field reconnection is shown to be highly sensitive to the ion/electron mass ratio applied in the simulation.

Ng, J.; Egedal, J.; Le, A. [Department of Physics, and Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Daughton, W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2012-11-15T23:59:59.000Z

78

Quadratic helicities and the energy of magnetic fields  

E-Print Network (OSTI)

Two non-local asymptotic invariants of magnetic fields for the ideal magnetohydrodynamics are introduced. The velocity of variation of the invariants for a non-ideal magnetohydrodynamics with a small magnetic dissipation is estimated. By means of the invariants the spectra of electromagnetic fields are investigated. A possible role of higher magnetic helicities during a relaxation of magnetic fields is discussed.

Petr M. Akhmet'ev

2011-10-05T23:59:59.000Z

79

Quadratic helicities and the energy of magnetic fields  

E-Print Network (OSTI)

Two non-local asymptotic invariants of magnetic fields for the ideal magnetohydrodynamics are introduced. The velocity of variation of the invariants for a non-ideal magnetohydrodynamics with a small magnetic dissipation is estimated. By means of the invariants the spectra of electromagnetic fields are investigated. A possible role of higher magnetic helicities during a relaxation of magnetic fields is discussed.

Akhmet'ev, Petr M

2011-01-01T23:59:59.000Z

80

Point sensitive NMR imaging system using a magnetic field configuration with a spatial minimum  

DOE Patents (OSTI)

A point-sensitive NMR imaging system (10) in which a main solenoid coil (11) produces a relatively strong and substantially uniform magnetic field and a pair of perturbing coils (PZ1 and PZ2) powered by current in the same direction superimposes a pair of relatively weak perturbing fields on the main field to produce a resultant point of minimum field strength at a desired location in a direction along the Z-axis. Two other pairs of perturbing coils (PX1, PX2; PY1, PY2) superimpose relatively weak field gradients on the main field in directions along the X- and Y-axes to locate the minimum field point at a desired location in a plane normal to the Z-axes. An RF generator (22) irradiates a tissue specimen in the field with radio frequency energy so that desired nuclei in a small volume at the point of minimum field strength will resonate.

Eberhard, Philippe H. (El Cerrito, CA)

1985-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Absolute magnetic helicity and the cylindrical magnetic field  

Science Conference Proceedings (OSTI)

The different magnetic helicities conserved under conditions of perfect electrical conductivity are expressions of the fundamental property that every evolving fluid surface conserves its net magnetic flux. This basic hydromagnetic point unifies the well known Eulerian helicities with the Lagrangian helicity defined by the conserved fluxes frozen into a prescribed set of disjoint toroidal tubes of fluid flowing as a permanent partition of the entire fluid [B. C. Low, Astrophys. J. 649, 1064 (2006)]. This unifying theory is constructed from first principles, beginning with an analysis of the Eulerian and Lagrangian descriptions of fluids, separating the ideas of fluid and magnetic-flux tubes and removing the complication of the magnetic vector potential's free gauge from the concept of helicity. The analysis prepares for the construction of a conserved Eulerian helicity, without that gauge complication, to describe a 3D anchored flux in an upright cylindrical domain, this helicity called absolute to distinguish it from the well known relative helicity. In a version of the Chandrasekhar-Kendall representation, the evolving field at any instant is a unique superposition of a writhed, untwisted axial flux with a circulating flux of field lines all closed and unlinked within the cylindrical domain. The absolute helicity is then a flux-weighted sum of the writhe of that axial flux and its mutual linkage with the circulating flux. The absolute helicity is also conserved if the frozen-in field and its domain are continuously deformed by changing the separation between the rigid cylinder-ends with no change of cylinder radius. This hitherto intractable cylindrical construction closes a crucial conceptual gap for the fundamentals to be complete at last. The concluding discussion shows the impact of this development on our understanding of helicity, covering (i) the helicities of wholly contained and anchored fields; (ii) the Eulerian and Lagrangian descriptions of field evolution; (iii) twist as a topological property of solenoidal fields versus the linkage properties of open and closed discrete curves treated by Gauss, Caligarneau, Berger, and Prior; and (iv) the change of absolute helicity by resistive diffusion. These are important hydromagnetic properties of twisted magnetic fields in the million-degree hot, highly conducting corona of the Sun.

Low, B. C. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado 80307 (United States)

2011-05-15T23:59:59.000Z

82

NONRELATIVISTIC COLLISIONLESS SHOCKS IN WEAKLY MAGNETIZED ELECTRON-ION PLASMAS: TWO-DIMENSIONAL PARTICLE-IN-CELL SIMULATION OF PERPENDICULAR SHOCK  

Science Conference Proceedings (OSTI)

A two-dimensional particle-in-cell simulation is performed to investigate weakly magnetized perpendicular shocks with a magnetization parameter of {sigma} = 6 x 10{sup -5}, which is equivalent to a high Alfven Mach number M{sub A} of {approx}130. It is shown that current filaments form in the foot region of the shock due to the ion-beam-Weibel instability (or the ion filamentation instability) and that they generate a strong magnetic field there. In the downstream region, these current filaments also generate a tangled magnetic field that is typically 15 times stronger than the upstream magnetic field. The thermal energies of electrons and ions in the downstream region are not in equipartition and their temperature ratio is T{sub e}/T{sub i} {approx} 0.3-0.4. Efficient electron acceleration was not observed in our simulation, although a fraction of the ions are accelerated slightly on reflection at the shock. The simulation results agree very well with the Rankine-Hugoniot relations. It is also shown that electrons and ions are heated in the foot region by the Buneman instability (for electrons) and the ion-acoustic instability (for both electrons and ions). However, the growth rate of the Buneman instability is significantly reduced due to the relatively high temperature of the reflected ions. For the same reason, ion-ion streaming instability does not grow in the foot region.

Kato, Tsunehiko N.; Takabe, Hideaki, E-mail: kato-t@ile.osaka-u.ac.j [Institute of Laser Engineering, Osaka University, 2-6 Yamada-oka, Suita, Osaka 565-0871 (Japan)

2010-09-20T23:59:59.000Z

83

Non-Employee Static Magnetic Field Questionnaire  

NLE Websites -- All DOE Office Websites (Extended Search)

Occupational Medicine Clinic (OMC) Occupational Medicine Clinic (OMC) Medical Questionnaire for non-BSA Workers/Students who may enter STATIC MAGNETIC FIELDS NAME:_________________ Extension__________ BNL Badge #:_____________ BNL Supervisor_____________ INSTRUCTIONS TO BSA SUPERVISOR or PRECEPTOR: Please print this form and give it to the (non-BSA employee) worker or student for completion. This individual should not give you the completed form, but should instead mail or fax it to OMC. INSTRUCTIONS TO WORKER or STUDENT: The purpose of this questionnaire is to provide the OMC physician at BNL with information about any medical devices or conditions you may have that might affect your ability to safely enter a strong magnetic field, in order to determine whether you can be medically cleared to enter such a field.

84

Probing the Magnetic Fields of Nearby Spiral Galaxies at Low Frequencies with LOFAR  

E-Print Network (OSTI)

While the Low Frequency Array (LOFAR) is still in its commissioning phase, early science results are starting to emerge. Two nearby galaxies, M51 and NGC4631, have been observed as part of the Magnetism Key Science Project's (MKSP) effort to increase our understanding of the nature of weak magnetic fields in galaxies. LOFAR and the complexity of its calibration as well as the aims and goals of the MKSP are presented.

Mulcahy, D D; Adebahr, B; Anderson, J; Beck, R; Bell, M R; Chyzy, K; Giessuebel, R; Heald, G; Horneffer, A; Jurusik, W; Pizzo, R; Scaife, A; Sotomayor-Beltran, C; Nikiel-Wroczynski, B

2011-01-01T23:59:59.000Z

85

Attenuation of a magnetic field by a superconductor  

Science Conference Proceedings (OSTI)

Observation of magnetic ac field penetration through superconducting tin films has led to the discovery of a 180° phase shift between the magnetic fields on either side of the film under favorable conditions. This result has so far been published ...

K. E. Drangeid; R. Sommerhalder; H. Müller; H. Seitz

1964-01-01T23:59:59.000Z

86

Characterization of Magnetic Fields from Power Distribution Transformers  

Science Conference Proceedings (OSTI)

This report describes a measurement study that was performed to characterize magnetic fields from power distribution transformers. The purpose of the study was to evaluate magnetic field attenuation rates of various sizes of transformers.

2009-09-25T23:59:59.000Z

87

A generalized lens equation for light deflection in weak gravitational fields  

E-Print Network (OSTI)

A generalized lens equation for weak gravitational fields in Schwarzschild metric and valid for finite distances of source and observer from the light deflecting body is suggested. The magnitude of neglected terms in the generalized lens equation is estimated to be smaller than or equal to 15 Pi/4 (m/d')^2, where m is the Schwarzschild radius of massive body and d' is Chandrasekhar's impact parameter. The main applications of this generalized lens equation are extreme astrometrical configurations, where 'Standard post-Newtonian approach' as well as 'Classical lens equation' cannot be applied. It is shown that in the appropriate limits the proposed lens equation yields the known post-Newtonian terms, 'enhanced' post-post-Newtonian terms and the Classical lens equation, thus provides a link between these both essential approaches for determining the light deflection.

Sven Zschocke

2011-05-18T23:59:59.000Z

88

Fluorescent lamp with static magnetic field generating means  

DOE Patents (OSTI)

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.

Moskowitz, P.E.; Maya, J.

1987-09-08T23:59:59.000Z

89

Fluorescent lamp with static magnetic field generating means  

DOE Patents (OSTI)

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.

Moskowitz, Philip E. (Peabody, MA); Maya, Jakob (Brookline, MA)

1987-01-01T23:59:59.000Z

90

Pilot Study of Nonresidential Power Frequency Magnetic Fields  

Science Conference Proceedings (OSTI)

EPRI has initiated several research projects to investigate magnetic field levels, their characteristics, and their sources. This report describes nonresidential magnetic field measurement protocols and instrumentation that can be used to identify and measure magnetic field sources in a variety of settings, including schools, offices, and electric utility facilities.

1991-09-01T23:59:59.000Z

91

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

E-Print Network (OSTI)

magnets to the magnetic energy stored within that magnet.the sample have stored magnetic energies as low as 3.3 M J (plotted against stored energy and magnetic field time field

Green, M.A.

2008-01-01T23:59:59.000Z

92

Parity of the Solar Magnetic Fields and Related Astrophysical Phenomena  

E-Print Network (OSTI)

The cumulative contribution of odd (Bo) and even (BE) parity zonal magnetic multipoles to the solar magnetic fields is calculated using spherical harmonic coefficients of the photospheric magnetic field for the years 1959-1985. The dominant parity of the solar magnetic field is shown to change from odd to even during every sunspot cycle. The association of variations of Bo and BE with different astrophysical phenomena such as magnetic reversal of solar polar magnetic fields, north-south asymmetry in sunspot activity and strength of the interplanetary magnetic field will be also discussed. Using solar observations we could infer that dominant parity of the solar magnetic field is changing from even to odd during the past 12 solar cycles when the solar activity is showing an increasing trend during this period.

G. Gopkumar; T. E. Girish

2010-12-16T23:59:59.000Z

93

Parity of the Solar Magnetic Fields and Related Astrophysical Phenomena  

E-Print Network (OSTI)

The cumulative contribution of odd (Bo) and even (BE) parity zonal magnetic multipoles to the solar magnetic fields is calculated using spherical harmonic coefficients of the photospheric magnetic field for the years 1959-1985. The dominant parity of the solar magnetic field is shown to change from odd to even during every sunspot cycle. The association of variations of Bo and BE with different astrophysical phenomena such as magnetic reversal of solar polar magnetic fields, north-south asymmetry in sunspot activity and strength of the interplanetary magnetic field will be also discussed. Using solar observations we could infer that dominant parity of the solar magnetic field is changing from even to odd during the past 12 solar cycles when the solar activity is showing an increasing trend during this period.

Gopkumar, G

2010-01-01T23:59:59.000Z

94

Multiparameter magnetic inspection system with magnetic field control and plural magnetic transducers  

DOE Patents (OSTI)

A multiparameter magnetic inspection system is disclosed for providing an efficient and economical way to derive a plurality of independent measurements regarding magnetic properties of the magnetic material under investigation. The plurality of transducers for a plurality of different types of measurements operatively connected to the specimen. The transducers are in turn connected to analytical circuits for converting transducer signals to meaningful measurement signals of the magnetic properties of the specimen. The measurement signals are processed and can be simultaneously communicated to a control component. The measurement signals can also be selectively plotted against one another. The control component operates the functioning of the analytical circuits and operates and controls components to impose magnetic fields of desired characteristics upon the specimen. The system therefore allows contemporaneous or simultaneous derivation of the plurality of different independent magnetic properties of the material which can then be processed to derive characteristics of the material. 1 figure.

Jiles, D.C.

1991-04-16T23:59:59.000Z

95

Numerical simulation of graphene in external magnetic field  

E-Print Network (OSTI)

In this paper the results of numerical simulation of monolayer graphene in external magnetic field are presented. The numerical simulation is performed in the effective lattice field theory with noncompact $3 + 1$-dimensional Abelian lattice gauge fields and $2 + 1$-dimensional staggered lattice fermions. The dependences of fermion condensate and graphene conductivity on the dielectric permittivity of substrate for different values of external magnetic field are calculated. It is found that magnetic field shifts insulator-semimetal phase transition to larger values of the dielectric permittivity of substrate. The phase diagram of graphene in external magnetic field is drawn.

D. L. Boyda; V. V. Braguta; S. N. Valgushev; M. I. Polikarpov; M. V. Ulybyshev

2013-08-13T23:59:59.000Z

96

Magnetic field survey at PG&E photovoltaic sites  

DOE Green Energy (OSTI)

Public awareness has aroused concerns over the possible effects of magnetic fields on human health. While research continues to determine if magnetic fields do, in fact, affect human health, concerned individuals are requesting data on magnetic field sources in their environments to base personal decisions about limiting their exposure to these sources. Timely acceptance and implementation of photovoltaics (PV), particularly for distributed applications such as PV rooftops, windows, and vehicles, may be hampered by the lack of PV magnetic field data. To address this situation, magnetic flux density was measured around equipment at two PVUSA (Photovoltaics for Utility Scale Applications) project sites in Kerman and Davis, California. This report documents the data and compares the PV magnetic fields with published data on more prevalent magnetic field sources. Although not comprehensive, electric and magnetic field (EMF) data taken at PVUSA indicate that 60-Hz magnetic fields (the EMF type of greatest public concern) are significantly less for PV arrays than for household applications. Therefore, given the present EMF research knowledge, PV array EMF may not merit considerable concern. The PV system components exhibiting significant AC magnetic fields are the transformers and power conditioning units (PCUs). However, the AC magnetic fields associated with these components are localized and are not detected at PV system perimeters. Concern about transformer and PCU EMF would apply to several generation and storage technologies.

Chang, G.J.; Jennings, C.

1994-08-01T23:59:59.000Z

97

Astrophysical gyrokinetics: kinetic and fluid turbulent cascades in magnetized weakly collisional plasmas  

E-Print Network (OSTI)

We present a theoretical framework for plasma turbulence in astrophysical plasmas (solar wind, interstellar medium, galaxy clusters, accretion disks). The key assumptions are that the turbulence is anisotropic with respect to the mean magnetic field and frequencies are low compared to the ion cyclotron frequency. The energy injected at the outer scale scale has to be converted into heat, which ultimately cannot be done without collisions. A KINETIC CASCADE develops that brings the energy to collisional scales both in space and velocity. Its nature depends on the physics of plasma fluctuations. In each of the physically distinct scale ranges, the kinetic problem is systematically reduced to a more tractable set of equations. In the "inertial range" above the ion gyroscale, the kinetic cascade splits into a cascade of Alfvenic fluctuations, which are governed by the RMHD equations at both the collisional and collisionless scales, and a passive cascade of compressive fluctuations, which obey a linear kinetic equation along the moving field lines associated with the Alfvenic component. In the "dissipation range" between the ion and electron gyroscales, there are again two cascades: the kinetic-Alfven-wave (KAW) cascade governed by two fluid-like Electron RMHD equations and a passive phase-space cascade of ion entropy fluctuations. The latter cascade brings the energy of the inertial-range fluctuations that was damped by collisionless wave-particle interaction at the ion gyroscale to collisional scales in the phase space and leads to ion heating. The KAW energy is similarly damped at the electron gyroscale and converted into electron heat. Kolmogorov-style scaling relations are derived for these cascades. Astrophysical and space-physical applications are discussed in detail.

A. A. Schekochihin; S. C. Cowley; W. Dorland; G. W. Hammett; G. G. Howes; E. Quataert; T. Tatsuno

2007-03-31T23:59:59.000Z

98

Electric and Magnetic Field Exposure During Live Line Work  

Science Conference Proceedings (OSTI)

An employee performing work on a transmission line while that line is energized is subjected to the local electric and magnetic fields produced by the voltage and current on the line. The electric field can result in spark discharges, contact currents, and stimulation of the body hair with attendant annoyance. Magnetic fields do not result in shock phenomena, but have become of concern to some people with regard to alleged health effects. Magnetic field shielding is not practical for live line ...

2013-10-07T23:59:59.000Z

99

Solar winds along curved magnetic field lines  

E-Print Network (OSTI)

Both remote-sensing measurements using the interplanetary scintillation (IPS) technique and in situ measurements by the Ulysses spacecraft show a bimodal structure for the solar wind at solar minimum conditions. At present what makes the fast wind fast and the slow wind slow still remains to be answered. While a robust empirical correlation exists between the coronal expansion rate $f_c$ of the flow tubes and the speeds $v$ measured in situ, further data analysis suggests that $v$ depends on more than just $f_c$. We examine whether the non-radial shape of field lines, which naturally accompanies any non-radial expansion, could be an additional geometrical factor. We solved the transport equations incorporating the heating due to turbulent Alfv\\'en waves for an electron-proton solar wind along curved field lines given by an analytical magnetic field model, representative of a solar minimum corona. The field line shape is found to influence substantially the solar wind parameters, reducing the asymptotic speed ...

Li, Bo; Chen, Yao

2011-01-01T23:59:59.000Z

100

Magnetic Fields1 Increasingly, instruments that generate large static magnetic fields (e.g., NMR spectrometers,  

E-Print Network (OSTI)

been issued by the International Commission on Non-ionizing Radiation (ICNIRP, 2009), which internal shielding, which reduces the strength of the magnetic field outside of the instrument. Strong, the hazards associated with cryogenic liquids are of concern, as well. The health effects of exposure

Shull, Kenneth R.

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Fermilab | Recovery Act | High-field superconducting magnets  

NLE Websites -- All DOE Office Websites (Extended Search)

may allow scientists to create high-field superconducting magnets that could exceed 50 Tesla, or more than twice the strength of existing magnets. In the project's first phase,...

102

Paramagnetic spin-up of a field reversed configuration with rotating magnetic field current drive.  

E-Print Network (OSTI)

??A transverse Rotating Magnetic Field (RMF) can drive toroidal current and sustain the poloidal flux of a Field Reversed Configuration (FRC) through the application of… (more)

Peter, Andrew Maxwell

2009-01-01T23:59:59.000Z

103

Magnetized GRB outflow model: weak reverse shock emission and short energy transfer timescale  

E-Print Network (OSTI)

We show that the absence of the bright optical flashes in most {\\it Swift} Gamma-ray Burst (GRB) afterglows can be explained, if the reverse shock region is magnetized with a $\\sigma \\sim 1$, or the emission spectrum of the electrons accelerated in the mildly magnetized ($0.1magnetized outflow is sub-relativistic, where $\\sigma$ is the ratio of the magnetic energy flux to the particle energy flux. We also find that for $\\sigma\\gg 1$, the energy transfer between the magnetized ejecta and the forward shock may be too quick to account for the shallow decline phase that is well detected in many {\\it Swift} GRB X-ray afterglows.

Yi-Zhong Fan

2008-08-05T23:59:59.000Z

104

Diffusion Processes in Turbulent Magnetic Fields  

E-Print Network (OSTI)

We study of the effect of turbulence on diffusion processes within magnetized medium. While we exemplify our treatment with heat transfer processes, our results are quite general and are applicable to different processes, e.g. diffusion of heavy elements. Our treatment is also applicable to describing the diffusion of cosmic rays arising from magnetic field wandering. In particular, we find that when the energy injection velocity is smaller than the Alfven speed the heat transfer is partially suppressed, while in the opposite regime the effects of turbulence depend on the intensity of driving. In fact, the scale $l_A$ at which the turbulent velocity is equal the Alfven velocity is a new important parameter. When the electron mean free path $\\lambda$ is larger than $l_A$, the stronger the the turbulence, the lower thermal conductivity by electrons is. The turbulent motions, however, induces their own advective transport, that can provide effective diffusivity. For clusters of galaxies, we find that the turbulence is the most important agent for heat transfer. We also show that the domain of applicability of the subdiffusion concept is rather limited.

Alex Lazarian

2007-07-04T23:59:59.000Z

105

Diffusion Processes in Turbulent Magnetic Fields  

E-Print Network (OSTI)

We study of the effect of turbulence on diffusion processes within magnetized medium. While we exemplify our treatment with heat transfer processes, our results are quite general and are applicable to different processes, e.g. diffusion of heavy elements. Our treatment is also applicable to describing the diffusion of cosmic rays arising from magnetic field wandering. In particular, we find that when the energy injection velocity is smaller than the Alfven speed the heat transfer is partially suppressed, while in the opposite regime the effects of turbulence depend on the intensity of driving. In fact, the scale $l_A$ at which the turbulent velocity is equal the Alfven velocity is a new important parameter. When the electron mean free path $\\lambda$ is larger than $l_A$, the stronger the the turbulence, the lower thermal conductivity by electrons is. The turbulent motions, however, induces their own advective transport, that can provide effective diffusivity. For clusters of galaxies, we find that the turbule...

Lazarian, Alex

2007-01-01T23:59:59.000Z

106

Remote Sensing of Chromospheric Magnetic Fields via the Hanle and Zeeman Effects  

E-Print Network (OSTI)

The only way to obtain reliable empirical information on the intensity and topology of the weak magnetic fields of the quiet solar chromosphere is via the measurement and rigorous physical interpretation of polarization signals in chromospheric spectral lines. The observed Stokes profiles reported here are due to the Hanle and Zeeman effects operating in a weakly magnetized plasma that is in a state far from local thermodynamic equilibrium. The physical origin of their enigmatic linear polarization Q and U components is the existence of atomic polarization in their metastable lower-levels, which permits the action of a dichroism mechanism that has nothing to do with the transverse Zeeman effect. It is also pointed out that the population imbalances and coherences among the Zeeman sublevels of such long-lived atomic levels can survive in the presence of horizontal magnetic fields having intensities in the gauss range, and produce significant polarization signals. Finally, it is shown how the most recent developments in the observation and theoretical modelling of weak polarization signals are facilitating fundamental new advances in our ability to investigate the magnetism of the outer solar atmosphere via spectropolarimetry.

J. Trujillo Bueno; R. Manso Sainz

2007-11-16T23:59:59.000Z

107

Casimir Momentum of a Chiral Molecule in a Magnetic Field  

E-Print Network (OSTI)

In a classical description, a neutral, polarizable object acquires a kinetic momentum when exposed to crossed electric and magnetic fields. In the presence of only a magnetic field no such momentum exists classically, although it is symmetry-allowed for an object lacking mirror symmetry. We perform a full QED calculation to show that the quantum vacuum coupled to a chiral molecule provides a kinetic "Casimir" momentum directed along the magnetic field, proportional to its rotatory power and the fine structure constant.

Manuel Donaire; Bart van Tiggelen; Geert L. J. A. Rikken

2013-04-24T23:59:59.000Z

108

Self-generated magnetic fields in q-distributed plasmas  

SciTech Connect

A quasi-steady magnetic field can be generated with high-frequency electromagnetic radiation through wave-wave and wave-particle interactions in astrophysical plasmas and laser-produced plasmas. Nonlinear coupling equations of self-generated magnetic fields are obtained in nonextensive distribution frame, as a generalization for the standard Maxwellian distribution frame. The numerical results show that self-generated magnetic fields may collapse and lead to various turbulent patterns with different index q.

Li Dingguo [School of Materials Science and Engineering, Nanchang University, Nanchang 330047 (China); School of Nuclear Engineering and Technology, East China Institute of Technology, Fuzhou 344000 (China); Liu Sanqiu [School of Materials Science and Engineering, Nanchang University, Nanchang 330047 (China); School of Science, Nanchang University, Nanchang 330047 (China); Li Xiaoqing [School of Science, Nanchang University, Nanchang 330047 (China)

2013-02-15T23:59:59.000Z

109

Temperature compensated current sensor using reference magnetic field  

DOE Patents (OSTI)

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.

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

2007-10-09T23:59:59.000Z

110

Phase diagram of hot quark matter under magnetic field  

Science Conference Proceedings (OSTI)

I review the computation of the phase diagram of hot quark matter in strong magnetic field, at zero baryon density, within an effective model of Quantum Chromodynamics.

Ruggieri, Marco [Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)

2010-12-22T23:59:59.000Z

111

Production of Materials with Superior Properties Utilizing High Magnetic Field  

Processing materials in a magnetic field is an innovative and revolutionary means to change materials and structural properties by tailoring the ...

112

Quark-gluon plasma in an external magnetic field  

E-Print Network (OSTI)

Using numerical simulations of lattice QCD we calculate the effect of an external magnetic field on the equation of state of the quark-gluon plasma. The results are obtained using a Taylor expansion of the pressure with respect to the magnetic field for the first time. The coefficients of the expansion are computed to second order in the magnetic field. Our setup for the external magnetic field avoids complications arising from toroidal boundary conditions, making a Taylor series expansion straightforward. This study is exploratory and is meant to serve as a proof of principle.

L. Levkova; C. DeTar

2013-09-04T23:59:59.000Z

113

Coulomb law and energy levels in a superstrong magnetic field  

E-Print Network (OSTI)

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

Vysotsky, M I

2012-01-01T23:59:59.000Z

114

Amplifying Magnetic Fields in High Energy Density Plasmas | U...  

Office of Science (SC) Website

Amplifying Magnetic Fields in High Energy Density Plasmas Fusion Energy Sciences (FES) FES Home About Research Facilities Science Highlights Benefits of FES Funding Opportunities...

115

Taking the Stress Out of Magnetic Field Detection  

Science Conference Proceedings (OSTI)

... Transmission electron microscope (TEM) images show sections of a continuous 400 ... that draw in external magnetic field lines and concentrate them ...

2012-10-18T23:59:59.000Z

116

Resonance enhancement of nonsequential double ionization by a magnetic field  

Science Conference Proceedings (OSTI)

We investigate nonsequential double ionization (NSDI) of helium by using an additional magnetic field parallel to the polarization of the laser pulse. By exploring the ability of a magnetic field for focusing the selected trajectories that contribute to the NSDI, we have found that the yield of NSDI, as a function of the magnetic-field strength, shows different behavior for different laser intensities. As a result, an additional magnetic field provides a way to identify that the NSDI mechanism of laser-assisted collision ionization begins to play an important role as the laser intensity increases.

Li Hongyun [Department of Physics, State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Peking University, Beijing 100871 (China); Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Chen Jing; Liu Jie [Center for Nonlinear Studies, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Jiang Hongbing; Gong Qihuang [Department of Physics, State Key Laboratory for Artificial Microstructures and Mesoscopic Physics, Peking University, Beijing 100871 (China); Fu Panming; Wang Bingbing [Laboratory of Optical Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Yan Zongchao [Department of Physics, University of New Brunswick, Fredericton, New Brunswick, E3B 5A3 (Canada)

2011-01-15T23:59:59.000Z

117

Quantitative imaging of stray fields and magnetization distributions in hard magnetic element arrays  

E-Print Network (OSTI)

Quantitative imaging of stray fields and magnetization distributions in hard magnetic element with inverse magnetostatic methods. The method is applied to hard magnetic FePt and PrCo5 films which exhibit of thin hard magnetic elements. We show that by application of the MOIF technique and inverse

Johansen, Tom Henning

118

Observation of low magnetic field density peaks in helicon plasma  

SciTech Connect

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.

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

119

Structural Steel Attenuation of External Magnetic Fields in Buildings  

Science Conference Proceedings (OSTI)

This report investigates the passive attenuation of external power-frequency magnetic fields caused by structural steel members used in commercial building construction. This effect has not been considered in previous assessments of the field levels inside buildings.

2007-04-26T23:59:59.000Z

120

Magnetic-field-induced antiferromagnetism in the Kondo lattice  

E-Print Network (OSTI)

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 ...

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

2004-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


121

High magnetic field processing of liquid crystalline polymers  

DOE Patents (OSTI)

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.

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

1998-11-24T23:59:59.000Z

122

High magnetic field processing of liquid crystalline polymers  

DOE Patents (OSTI)

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.

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

1998-01-01T23:59:59.000Z

123

Magnetic hose: Routing and Long-distance Transportation of Magnetic Fields  

E-Print Network (OSTI)

Magnetism is a fundamental interaction shaping our physical world, at the basis of technologies such as magnetic recording or energy generation. Unlike electromagnetic waves, which can be routed and transmitted with waveguides to long distances, magnetic fields rapidly decay with distance. Here we show the concept, design, and properties of a magnetic hose which enables to transfer the static magnetic field generated by a source to an arbitrary distance, and along any given trajectory. Using transformation optics, adapted to static magnetic fields, we first introduce an ideal scheme displaying the basic mechanism behind our proposal and allowing for a perfect transfer. Then we present a simplified approach, which allows to construct a magnetic hose using two available materials: a superconducting shell with a ferromagnetic core. Such a magnetic hose can guide and transport magnetic fields to large distances, unlike ferromagnets- the conventional existing method-, for which transmitted fields decay quickly with the ferromagnetic length. As a proof of pinciple experiment, we demonstrate the field transmission through superconducting-ferromagnetic hoses with lengths up to 140mm, which improve the transmission of an analogous ferromagnet by a 400% factor. Magnetic hoses may provide new solutions in enhancing spin couplings in all-magnetic logic schemes and in harnessing quantum systems by addressable magnetic fields, in the context of quantum information processing.

Carles Navau; Jordi Prat-Camps; Oriol Romero-Isart; J. Ignacio Cirac; Alvaro Sanchez

2013-04-23T23:59:59.000Z

124

The Orientation of the Local Interstellar Magnetic Field  

E-Print Network (OSTI)

The orientation of the local interstellar magnetic field introduces asymmetries in the heliosphere that affect the location of heliospheric radio emissions and the streaming direction of ions from the termination shock of the solar wind. We combine observations of radio emissions and energetic particle streaming with extensive 3D MHD computer simulations of magnetic field draping over the heliopause to show that the plane of the local interstellar field is ~ 60-90 degrees from the galactic plane. This suggests that the field orientation in the Local Interstellar Cloud differs from that of a larger scale interstellar magnetic field thought to parallel the galactic plane.

M. Opher; E. C. Stone; T. I. Gombosi

2007-05-13T23:59:59.000Z

125

Perturbative analysis of sheared flow Kelvin-Helmholtz instability in a weakly relativistic magnetized electron fluid  

Science Conference Proceedings (OSTI)

In the interaction of intense lasers with matter/plasma, energetic electrons having relativistic energies get created. These energetic electrons can often have sheared flow profiles as they propagate through the plasma medium. In an earlier study [Phys. Plasmas 17, 022101 (2010)], it was shown that a relativistic sheared electron flow modifies the growth rate and threshold condition of the conventional Kelvin-Helmholtz instability. A perturbative analytic treatment for the case of weakly relativistic regime has been provided here. It provides good agreement with the numerical results obtained earlier.

Sundar, Sita; Das, Amita; Kaw, Predhiman [Institute for Plasma Research, Bhat, Gandhinagar-382428 (India)

2012-05-15T23:59:59.000Z

126

Processing of Soft Magnetic Alloys in High Magnetic Field  

Science Conference Proceedings (OSTI)

... Magnetic Materials for Use in Energy-efficient Distribution Transformers ... Novel Morphology of Highly Efficient Two-phase Ferrite Cores for Power Systems

127

Role of Magnetic Fields and Texturing to Improved Magnetic Materials  

Science Conference Proceedings (OSTI)

Mar 13, 2012 ... Experiments to observe the structural and magnetic phase transformations were performed at the Spallation Neutron Source (SNS) at Oak ...

128

Magnetic properties of the nucleon in a uniform background field  

E-Print Network (OSTI)

We present results for the magnetic moment and magnetic polarisability of the neutron and the magnetic moment of the proton. These results are calculated using the uniform background field method on 32^3 x 64 dynamical QCD lattices provided by the PACS-CS collaboration as part of the ILDG. We use a uniform background magnetic field quantised by the periodic spatial volume. We investigate ways to improve the effective energy plots used to calculate magnetic polarisabilities, including the use of correlation matrix techniques with various source smearings.

Thomas Primer; Waseem Kamleh; Derek Leinweber; Matthias Burkardt

2013-07-05T23:59:59.000Z

129

Developments in deep brain stimulation using time dependent magnetic fields  

SciTech Connect

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.

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

2012-03-07T23:59:59.000Z

130

Gluon Vortices and Induced Magnetic Field in Compact Stars  

E-Print Network (OSTI)

The natural candidates for the realization of color superconductivity are the extremely dense cores of compact stars, many of which have very large magnetic fields, especially the so-called magnetars. In this paper we discuss how a color superconducting core can serve to generate and enhance the stellar magnetic field without appealing to a magnetohydrodynamic dynamo mechanism.

Efrain J. Ferrer

2007-08-12T23:59:59.000Z

131

Gluon Vortices and Induced Magnetic Field in Compact Stars  

SciTech Connect

The natural candidates for the realization of color superconductivity are the extremely dense cores of compact stars, many of which have very large magnetic fields, especially the so called magnetars. In this paper we discuss how a color superconducting core can serve to generate and enhance the stellar magnetic field without appealing to a magnetohydrodynamic dynamo mechanism.

Ferrer, Efrain J. [Department of Physics, Western Illinois University, Macomb, IL 61455 (United States)

2007-10-26T23:59:59.000Z

132

Measurement of Power System Magnetic Fields by Waveform Capture  

Science Conference Proceedings (OSTI)

An instrumentation and software package has been developed to characterize an extensive range of temporal, spatial, and frequency parameters associated with magnetic fields.The MultiWave (TM) System can capture the actual magnetic field waveform and coexisting power system environmental conditions in residential, nonresidential, and transient capture applications.

1992-03-01T23:59:59.000Z

133

Phase transitions in quark matter under strong magnetic fields  

SciTech Connect

In this work we use de SU(2) Nambu-Jona-Lasinio model to study the chiral transition at finite temperature, chemical potential and magnetic field. We show how the magnetic field affects the location of the critical end-point in the phase diagram, the constituent quark masses and the spinodal lines concerning the first order transition.

Garcia, Andre F.; Pinto, Marcus B. [Physics Department, Universidade Federal de Santa Catarina (Brazil)

2013-03-25T23:59:59.000Z

134

Heart Rate Variability (HRV) in Ambient Magnetic Fields  

Science Conference Proceedings (OSTI)

In a healthy individual, the rate at which the heart beats exhibits continuous variability. In prior research at Midwest Research Institute (MRI), exposure to intermittent, but not continuous, magnetic fields was associated with alterations in heart rate variability (HRV). This report describes additional studies specifically designed to address the potential effects of magnetic field exposure on HRV.

1998-12-17T23:59:59.000Z

135

Time evolution of fields in strontium ferrite permanent magnets  

SciTech Connect

Field strengths for strontium ferrite permanent magnets built for the Fermilab Recycler and 8 GeV transfer line have been measured for the past 4 years. The ferrite magnetization exhibits a time dependence parameterized by M1/M{sub 2} = -9 x 10{sup -4} x log (t{sub 1}/t{sub 2}) as determined from measurements of a gradient magnet. This parameterization has been checked against several other styles of permanent dipoles, and quadrupole magnets with good agreement.

James T. Volk et al.

2001-06-11T23:59:59.000Z

136

Magnetism of a relativistic degenerate electron gas in a strong magnetic field  

SciTech Connect

The magnetization and magnetic susceptibility of a degenerate electron gas in a strong magnetic field in which electrons are located on the ground Landau level and the electron gas has the properties of a nonlinear paramagnet have been calculated. The paradoxical properties of the electron gas under these conditions-a decrease in the magnetization with the field and an increase in the magnetization with the temperature-have been revealed. It has been shown that matter under the corresponding conditions of neutron stars is a paramagnet with a magnetic susceptibility of {chi} {approx} 0.001.

Skobelev, V. V., E-mail: v.skobelev@inbox.ru [Moscow State Industrial University (Russian Federation)

2012-09-15T23:59:59.000Z

137

Projectile-power-compressed magnetic-field pulse generator  

DOE Green Energy (OSTI)

Design considerations and experimental results are presented of a compressed magnetic field pulsed energy source. A 100-mm-diameter, gun-fired projectile of approx. 2MJ kinetic energy was the input energy source. An initial magnetic field was trapped and compressed by the projectile. With a shorted load, a magajoule in a nanohenry was the design goal, i.e., 50 percent energy transformation from kinetic to magnetic. Five percent conversion was the highest recorded before gauge failure.

Barlett, R.H.; Takemori, H.T.; Chase, J.B.

1983-03-17T23:59:59.000Z

138

THE DESIGN AND CONSTRUCTION OF MAGNETIC FIELDS FOR PLASMA RESEARCH  

SciTech Connect

The main problems arising during the design and con struction of medium size air-core electro-magnets are discussed. The basic equations are given relating magnetic field strength, magnetic field rise time, power input, electrodynamic forces, and thermal conditions e.g., allowable temperature rise to give the detailed dimensions required for the electrical conductor and the cooling annull. The details for a 25 kgauss sectional oil-cooled electromagnet for plasma research are described. (auth)

Gryzinski, M.; Sadowski, M.

1962-03-01T23:59:59.000Z

139

NMR system and method having a permanent magnet providing a rotating magnetic field  

DOE Patents (OSTI)

Disclosed herein are systems and methods for generating a rotating magnetic field. The rotating magnetic field can be used to obtain rotating-field NMR spectra, such as magic angle spinning spectra, without having to physically rotate the sample. This result allows magic angle spinning NMR to be conducted on biological samples such as live animals, including humans.

Schlueter, Ross D [Berkeley, CA; Budinger, Thomas F [Berkeley, CA

2009-05-19T23:59:59.000Z

140

Fundamental Statistical Descriptions of Plasma Turbulence in Magnetic Fields  

SciTech Connect

A pedagogical review of the historical development and current status (as of early 2000) of systematic statistical theories of plasma turbulence is undertaken. Emphasis is on conceptual foundations and methodology, not practical applications. Particular attention is paid to equations and formalism appropriate to strongly magnetized, fully ionized plasmas. Extensive reference to the literature on neutral-fluid turbulence is made, but the unique properties and problems of plasmas are emphasized throughout. Discussions are given of quasilinear theory, weak-turbulence theory, resonance-broadening theory, and the clump algorithm. Those are developed independently, then shown to be special cases of the direct-interaction approximation (DIA), which provides a central focus for the article. Various methods of renormalized perturbation theory are described, then unified with the aid of the generating-functional formalism of Martin, Siggia, and Rose. A general expression for the renormalized dielectric function is deduced and discussed in detail. Modern approaches such as decimation and PDF methods are described. Derivations of DIA-based Markovian closures are discussed. The eddy-damped quasinormal Markovian closure is shown to be nonrealizable in the presence of waves, and a new realizable Markovian closure is presented. The test-field model and a realizable modification thereof are also summarized. Numerical solutions of various closures for some plasma-physics paradigms are reviewed. The variational approach to bounds on transport is developed. Miscellaneous topics include Onsager symmetries for turbulence, the interpretation of entropy balances for both kinetic and fluid descriptions, self-organized criticality, statistical interactions between disparate scales, and the roles of both mean and random shear. Appendices are provided on Fourier transform conventions, dimensional and scaling analysis, the derivations of nonlinear gyrokinetic and gyrofluid equations, stochasticity criteria for quasilinear theory, formal aspects of resonance-broadening theory, Novikov's theorem, the treatment of weak inhomogeneity, the derivation of the Vlasov weak-turbulence wave kinetic equation from a fully renormalized description, some features of a code for solving the direct-interaction approximation and related Markovian closures, the details of the solution of the EDQNM closure for a solvable three-wave model, and the notation used in the article.

John A. Krommes

2001-02-16T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Brownian dynamics of charged particles in a constant magnetic field  

SciTech Connect

Numerical algorithms are proposed for simulating the Brownian dynamics of charged particles in an external magnetic field, taking into account the Brownian motion of charged particles, damping effect, and the effect of magnetic field self-consistently. Performance of these algorithms is tested in terms of their accuracy and long-time stability by using a three-dimensional Brownian oscillator model with constant magnetic field. Step-by-step recipes for implementing these algorithms are given in detail. It is expected that these algorithms can be directly used to study particle dynamics in various dispersed systems in the presence of a magnetic field, including polymer solutions, colloidal suspensions, and, particularly, complex (dusty) plasmas. The proposed algorithms can also be used as thermostat in the usual molecular dynamics simulation in the presence of magnetic field.

Hou, L. J.; Piel, A. [IEAP, Christian-Albrechts Universitaet, D-24118 Kiel (Germany); Miskovic, Z. L. [Department of Applied Mathematics, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Shukla, P. K. [Institut fuer Theoretische Physik IV, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2009-05-15T23:59:59.000Z

142

Nucleation of bulk superconductivity close to critical magnetic field  

E-Print Network (OSTI)

We consider the two-dimensional Ginzburg-Landau functional with constant applied magnetic field. For applied magnetic fields close to the second critical field $H_{C_2}$ and large Ginzburg-Landau parameter, we provide leading order estimates on the energy of minimizing configurations. We obtain a fine threshold value of the applied magnetic field for which bulk superconductivity contributes to the leading order of the energy. Furthermore, the energy of the bulk is related to that of the Abrikosov problem in a periodic lattice. A key ingredient of the proof is a novel $L^\\infty$-bound which is of independent interest.

S. Fournais; A. Kachmar

2009-09-30T23:59:59.000Z

143

Analysis of magnetic fields produced far from electric power lines  

Science Conference Proceedings (OSTI)

In this paper, the authors develop a simple and general method for analyzing the magnetic fields produced by power lines at far distances, that is, at distances large in comparison to the spacing between the line's phase conductors. Magnetic fields produced far from conventional power lines have remarkably simple properties. The authors present formulae for the fields produced by various conventional and unconventional power line configurations; included are line designs characterized by reduced magnetic-field levels. Errors in the formulae are less than [plus minus]10% at the edge of a typical transmission right-of-way.

Kaune, W.T. (Enertech Consultants Campbell, CA (United States)); Zaffanella, L.E. (High Voltage Transmission Research Center, Lenox, MA (United States))

1992-10-01T23:59:59.000Z

144

Tunable Polarization of Spin Polarized Current by Magnetic Field  

SciTech Connect

The spin polarization of a high g-factor bulk semiconductor is theoretically investigated in the presence of a magnetic field parallel to a driving electric field. Calculations have been carried out using the energy-dependent relaxation time approximation in association with spin-flip scattering. As the magnitude of the magnetic field increases, the spin-polarized current alternates between the spin-up and spin-down states for the low spin-scattering system. This implies that the current polarization can be tuned by controlling the magnetic field strength, suggesting possible applications to spintronic devices. An experimental method for investigating alternative current polarization is also considered.

Joo, S.; Kim, K.; Lee, J.; Kim, T.; Rhie, K.; Hong, J.; Shin, K-H.

2010-10-10T23:59:59.000Z

145

DYNAMICS OF CHROMOSPHERIC UPFLOWS AND UNDERLYING MAGNETIC FIELDS  

SciTech Connect

We used H{alpha}-0.1 nm and magnetic field (at 1.56{mu}) data obtained with the New Solar Telescope to study the origin of the disk counterparts to type II spicules, so-called rapid blueshifted excursions (RBEs). The high time cadence of our chromospheric (10 s) and magnetic field (45 s) data allowed us to generate x-t plots using slits parallel to the spines of the RBEs. These plots, along with potential field extrapolation, led us to suggest that the occurrence of RBEs is generally correlated with the appearance of new, mixed, or unipolar fields in close proximity to network fields. RBEs show a tendency to occur at the interface between large-scale fields and small-scale dynamic magnetic loops and thus are likely to be associated with the existence of a magnetic canopy. Detection of kinked and/or inverse {sup Y-}shaped RBEs further confirm this conclusion.

Yurchyshyn, V.; Abramenko, V.; Goode, P. [Big Bear Solar Observatory, New Jersey Institute of Technology, Big Bear City, CA 92314 (United States)] [Big Bear Solar Observatory, New Jersey Institute of Technology, Big Bear City, CA 92314 (United States)

2013-04-10T23:59:59.000Z

146

PROBING PRIMORDIAL MAGNETIC FIELDS USING Ly{alpha} CLOUDS  

SciTech Connect

From previous studies of the effect of primordial magnetic fields on early structure formation, we know that the presence of primordial magnetic fields during early structure formation could induce more perturbations at small scales (at present 1-10 h {sup -1} Mpc) as compared to the usual {Lambda}CDM theory. Matter power spectra over these scales are effectively probed by cosmological observables such as shear correlation and Ly{alpha} clouds. In this paper we discuss the implications of primordial magnetic fields on the distribution of Ly{alpha} clouds. We simulate the line-of-sight density fluctuation including the contribution coming from the primordial magnetic fields. We compute the evolution of Ly{alpha} opacity for this case and compare our theoretical estimates of Ly{alpha} opacity with the existing data to constrain the parameters of the primordial magnetic fields. We also discuss the case when the two density fields are correlated. Our analysis yields an upper bound of roughly 0.3-0.6 nG on the magnetic field strength for a range of nearly scale-invariant models, corresponding to a magnetic field power spectrum index n {approx_equal} -3.

Pandey, Kanhaiya L.; Sethi, Shiv K. [Raman Research Institute, Bangalore 560080 (India)] [Raman Research Institute, Bangalore 560080 (India)

2013-01-01T23:59:59.000Z

147

Los Alamos achieves world-record pulsed magnetic field  

NLE Websites -- All DOE Office Websites (Extended Search)

Los Alamos achieves world-record pulsed magnetic field Los Alamos achieves world-record pulsed magnetic field Los Alamos achieves world-record pulsed magnetic field Researchers have set a new world record for the strongest magnetic field produced by a nondestructive magnet. August 23, 2011 Los Alamos National Laboratory sits on top of a once-remote mesa in northern New Mexico with the Jemez mountains as a backdrop to research and innovation covering multi-disciplines from bioscience, sustainable energy sources, to plasma physics and new materials. Los Alamos National Laboratory sits on top of a once-remote mesa in northern New Mexico with the Jemez mountains as a backdrop to research and innovation covering multi-disciplines from bioscience, sustainable energy sources, to plasma physics and new materials.

148

Interaction mechanisms and biological effects of static magnetic fields  

Science Conference Proceedings (OSTI)

Mechanisms through which static magnetic fields interact with living systems are described and illustrated by selected experimental observations. These mechanisms include electrodynamic interactions with moving, ionic charges (blood flow and nerve impulse conduction), magnetomechanical interactions (orientation and translation of molecules structures and magnetic particles), and interactions with electronic spin states in charge transfer reactions (photo-induced electron transfer in photosynthesis). A general summary is also presented of the biological effects of static magnetic fields. There is convincing experimental evidence for magnetoreception mechanisms in several classes of lower organisms, including bacteria and marine organisms. However, in more highly evolved species of animals, there is no evidence that the interactions of static magnetic fields with flux densities up to 2 Tesla (1 Tesla [T] = 10{sup 4} Gauss) produce either behavioral or physiolocical alterations. These results, based on controlled studies with laboratory animals, are consistent with the outcome of recent epidemiological surveys on human populations exposed occupationally to static magnetic fields.

Tenforde, T.S.

1994-06-01T23:59:59.000Z

149

Holographic Photon Production with Magnetic Field in Anisotropic Plasmas  

E-Print Network (OSTI)

We investigate the thermal photon production from constant magnetic field in a strongly coupled and anisotropic plasma via the gauge/gravity duality. The dual geometry with pressure anisotropy is generated from the axion-dilaton gravity action introduced by Mateos and Trancancelli and the magnetic field is coupled to fundamental matters(quarks) through the D3/D7 embeddings. We find that the photon spectra with different quark mass are enhanced at large frequency when the photons are emitted parallel to the anisotropic direction with larger pressure or perpendicular to the magnetic field. However, in the opposite conditions for the emitted directions, the spectra approximately saturate isotropic results in the absence of magnetic field. On the other hand, a resonance emerges at moderate frequency for the photon spectrum with heavy quarks when the photons move perpendicular to the magnetic field. The resonance is more robust when the photons are polarized along the magnetic field. On the contrary, in the presence of pressure anisotropy, the resonance will be suppressed. There exist competing effects of magnetic field and pressure anisotropy on meson melting in the strongly coupled super Yang-Mills plasma, while we argue that the suppression led by anisotropy may not be applied to the quark gluon plasma.

Shang-Yu Wu; Di-Lun Yang

2013-05-23T23:59:59.000Z

150

First magnetic field models for recently discovered magnetic beta Cephei and slowly pulsating B stars  

E-Print Network (OSTI)

In spite of recent detections of magnetic fields in a number of beta Cephei and slowly pulsating B (SPB) stars, their impact on stellar rotation, pulsations, and element diffusion is not sufficiently studied yet. The reason for this is the lack of knowledge of rotation periods, the magnetic field strength distribution and temporal variability, and the field geometry. New longitudinal field measurements of four beta Cephei and candidate beta Cephei stars, and two SPB stars were acquired with FORS2 at the VLT. These measurements allowed us to carry out a search for rotation periods and to constrain the magnetic field geometry for four stars in our sample.

Hubrig, S; Schoeller, M; Briquet, M; Morel, T; De Cat, P

2011-01-01T23:59:59.000Z

151

Magnetic fields and the dynamics of spiral galaxies  

E-Print Network (OSTI)

We investigate the dynamics of magnetic fields in spiral galaxies by performing 3D MHD simulations of galactic discs subject to a spiral potential. Recent hydrodynamic simulations have demonstrated the formation of inter-arm spurs as well as spiral arm molecular clouds provided the ISM model includes a cold HI phase. We find that the main effect of adding a magnetic field to these calculations is to inhibit the formation of structure in the disc. However, provided a cold phase is included, spurs and spiral arm clumps are still present if $\\beta \\gtrsim 0.1$ in the cold gas. A caveat to two phase calculations though is that by assuming a uniform initial distribution, $\\beta \\gtrsim 10$ in the warm gas, emphasizing that models with more consistent initial conditions and thermodynamics are required. Our simulations with only warm gas do not show such structure, irrespective of the magnetic field strength. Furthermore, we find that the introduction of a cold HI phase naturally produces the observed degree of disorder in the magnetic field, which is again absent from simulations using only warm gas. Whilst the global magnetic field follows the large scale gas flow, the magnetic field also contains a substantial random component that is produced by the velocity dispersion induced in the cold gas during the passage through a spiral shock. Without any cold gas, the magnetic field in the warm phase remains relatively well ordered apart from becoming compressed in the spiral shocks. Our results provide a natural explanation for the observed high proportions of disordered magnetic field in spiral galaxies and we thus predict that the relative strengths of the random and ordered components of the magnetic field observed in spiral galaxies will depend on the dynamics of spiral shocks.

C. L. Dobbs; D. J. Price

2007-10-18T23:59:59.000Z

152

CALCULATION OF PULSED KICKER MAGNETIC FIELD ATTENUATION INSIDE BEAM CHAMBERS  

NLE Websites -- All DOE Office Websites (Extended Search)

CALCULATION OF PULSED KICKER MAGNETIC FIELD ATTENUATION CALCULATION OF PULSED KICKER MAGNETIC FIELD ATTENUATION INSIDE BEAM CHAMBERS S. H. Kim January 8, 2001 1. Introduction and Summary The ceramic beam chambers in the sections of the kicker magnets for the beam injection and extraction in the Advanced Photon Source (APS) are made of alumina. The inner surface of the ceramic chamber is coated with a conductive paste. The choice of coating thickness is intended to reduce the shielding of the pulsed kicker magnetic field while containing the electromagnetic fields due to the beam bunches inside the chamber, and minimize the Ohmic heating due to the fields on the chamber [1]. The thin coating generally does not give a uniform surface resistivity for typical dimensions of the ceramic chambers in use. The chamber cross section is a circular or

153

Inflationary susceptibilities, duality and large-scale magnetic fields generation  

E-Print Network (OSTI)

We investigate what can be said about the interaction of scalar fields with Abelian gauge fields during a quasi-de Sitter phase of expansion and under the assumption that the electric and the magnetic susceptibilities do not coincide. The duality symmetry, transforming the magnetic susceptibility into the inverse of the electric susceptibility, exchanges the magnetic and electric power spectra. The mismatch between the two susceptibilities determines an effective refractive index affecting the evolution of the canonical fields. The constraints imposed by the duration of the inflationary phase and by the magnetogenesis requirements pin down the rate of variation of the susceptibilities that is consistent with the observations of the magnetic field strength over astrophysical and cosmological scales but avoids back-reaction problems. The parameter space of this magnetogenesis scenario is wider than in the case when the susceptibilities are equal, as it happens when the inflaton or some other spectator field is solely coupled to the standard gauge kinetic term.

Massimo Giovannini

2013-10-07T23:59:59.000Z

154

Heat pipes for use in a magnetic field  

DOE Patents (OSTI)

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.

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

1983-07-19T23:59:59.000Z

155

Interstellar Turbulent Magnetic Field Generation by Plasma Instabilities  

E-Print Network (OSTI)

The maximum magnetic field strength generated by Weibel-type plasma instabilities is estimated for typical conditions in the interstellar medium. The relevant kinetic dispersion relations are evaluated by conducting a parameter study both for Maxwellian and for suprathermal particle distributions showing that micro Gauss magnetic fields can be generated. It is shown that, depending on the streaming velocity and the plasma temperatures, either the longitudinal or a transverse instability will be dominant. In the presence of an ambient magnetic field, the filamentation instability is typically suppressed while the two-stream and the classic Weibel instability are retained.

Tautz, R C

2013-01-01T23:59:59.000Z

156

Heat pipes for use in a magnetic field  

DOE Patents (OSTI)

A heat pipe configuration is described for use in a magnetic field environment of a fusion reactor. 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 to 3 times the heat as a cylindrical heat pipe of the same cross sectional area.

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

1981-04-29T23:59:59.000Z

157

Intense transient magnetic-field generation by laser plasma  

DOE Patents (OSTI)

In a laser system, the return current of a laser generated plasma is conducted near a target to subject that target to the magnetic field thereof. In alternate embodiments the target may be either a small non-fusion object for testing under the magnetic field or a laser-fusion pellet. In the laser-fusion embodiment, the laser-fusion pellet is irradiated during the return current flow and the intense transient magnetic field is used to control the hot electrons thereof to hinder them from striking and heating the core of the irradiated laser-fusion pellet.

Benjamin, R.F.

1981-08-18T23:59:59.000Z

158

Heat pipes for use in a magnetic field  

DOE Patents (OSTI)

A heat pipe configuration for use in a magnetic field environment of a fusion reactor. 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.

Werner, Richard W. (San Ramon, CA); Hoffman, Myron A. (Davis, CA)

1983-01-01T23:59:59.000Z

159

PERMANENT MAGNET DESIGNS WITH LARGE VARIATIONS IN FIELD STRENGTH.  

Science Conference Proceedings (OSTI)

The use of permanent magnets has been investigated as an option for electron cooling ring for the proposed luminosity upgrade of RHIC. Several methods have been developed that allow a large variation in field strength. These design concepts were verified with computer simulations using finite element codes. It will be shown that the field uniformity is maintained while the field strength is mechanically adjusted.

GUPTA,R.

2004-01-21T23:59:59.000Z

160

Superconducting Magnetic Energy Storage in Trapped Field Magnets of High Temperature Superconductors  

Science Conference Proceedings (OSTI)

Superconducting permanent magnets for storing high magnetic fields can serve as a means of energy storage and are useful in applications ranging from motors and generators to fault current limiters and circuit breakers. This report presents the results of experimental studies on high temperature superconductors, which were successfully used to trap a record high stable magnetic field of 83,000 G at 54 K and 100,000 G at 42 K.

1995-12-29T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

Materials Physics Applications: The National High Magnetic Field Laboratory  

NLE Websites -- All DOE Office Websites (Extended Search)

Search Search National High Magnetic Field Laboratory, NHMFL Home About Us Organization DIVISION Materials Physics and Applications Division GROUPS Superconductivity Technology Center Condensed Matter and Magnet Science Center for Integrated Nanotechnologies Sensors & Electrochemical Devices Materials Chemistry CONTACTS Group Leader Mike Hundley Director, NHMFL-PFF/Deputy Group Leader Chuck Mielke Head of Users Program Operations Jon Betts Professional Staff Assistant Julie T. Gallegos TA-03 Group Office TA-03, Building 0034, Room 101 Office Administrator Juanita Armijo TA-35 Group Office TA-35, Building 0127, Room C117 Office Administrator Angeline Willow 505-667-5032 National High Magnetic Field Laboratory, Pulsed Field Facility The Pulsed Field Facility at Los Alamos National Laboratory in Los Alamos, New Mexico, is one of three campuses of the National High Magnetic Field Laboratory (NHMFL), the other two being at Florida State University, Tallahassee (continuous fields, magnetic resonance, and general headquarters) and the University of Florida ,Gainesville(ultra-low temperatures at high magnetic fields). The NHMFL is sponsored primarily by the National Science Foundation, Division of Materials Research, with additional support from the State of Florida and the US Department of Energy.

162

Influence of primordial magnetic fields on 21 cm emission  

E-Print Network (OSTI)

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.

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

2008-08-11T23:59:59.000Z

163

Bio-Med Variable Field MRI Project | Superconducting Magnet Division  

NLE Websites -- All DOE Office Websites (Extended Search)

Bio-Med Variable Field MRI Project Bio-Med Variable Field MRI Project One of the Research and Development projects currently underway is the Bio-Med magnet. Destined for use within the solenoidal field of an MRI, it is designed for use where the subject, in this case a rat, must be tracked in order to obtain an image. Typical MRIs require the subject to remain stationary, and a rat will not normally oblige when it is awake. By moving the composite field (MRI Solenoid plus Bio-Med dipole) to track the rat, it is possible to allow the rat some freedom of motion, while still imaging the brain functions. For the rapid movement typical of a rat, the Bio-Med coil magnet must be capable of very rapid changes in field. Superconducting magnets are typically not designed to allow rapid field variations. To do so typically

164

New approaches to thermoelectric cooling effects in magnetic fields  

DOE Green Energy (OSTI)

The authors review thermoelectric effects in a magnetic field at a phenomenological level. Discussions of the limiting performance and problems with its computation for both Peltier and Ettingshausen coolers are presented. New principles to guide the materials scientists are discussed for magnetic effects, and a brief review of the subtle measurement problems is presented.

Migliori, A.; Darling, T.W.; Freibert, F. [and others

1997-05-01T23:59:59.000Z

165

Gravitational influences on magnetic field structure in accretion disks  

E-Print Network (OSTI)

Black holes and compact objects are often surrounded by structures known as accretion disks which consist of ionized plasma. Due to the immense forces present in the disk, interesting and complex magnetic field structures ...

Schneck, Kristiana E. (Kristiana Elizabeth)

2010-01-01T23:59:59.000Z

166

EMDEX (Electric and Magnetic Field Digital EXposure) system manuals  

Science Conference Proceedings (OSTI)

The EPRI Electric and Magnetic Field Digital EXposure (EMDEX) system consists of hardware and software for characterizing electric and magnetic field exposures. The EMDEX meter is a computer-based portable unit that samples, at a user-programmable rate, the three vector components of magnetic flux density, a measure of the average electric field acting on the torso of the wearer (if an optional sensor is worn) and a measure of rotational motion of the meter in the earth's magnetic field. Modules of the DATACALC software package are used to program the EMDEX, retrieve data at the end of a measurement session, analyze EMDEX data, and prepare tabular and graphical data summaries. The User Manual is designed to provide instruction on the use of the exposure system hardware and software. The Technical Reference Manual provides additional, detailed descriptions of the hardware, software and methodologies used in the EMDEX system.

Not Available

1989-10-01T23:59:59.000Z

167

CONSTRAINING PRIMORDIAL MAGNETIC FIELDS THROUGH LARGE-SCALE STRUCTURE  

Science Conference Proceedings (OSTI)

We study primordial magnetic field effects on the matter perturbations in the universe. We assume magnetic field generation prior to the big bang nucleosynthesis (BBN), i.e., during the radiation-dominated epoch of the universe expansion, but do not limit analysis by considering a particular magnetogenesis scenario. Contrary to previous studies, we limit the total magnetic field energy density and not the smoothed amplitude of the magnetic field at large (of the order of 1 Mpc) scales. We review several cosmological signatures, such as halo abundance, thermal Sunyaev-Zel'dovich effect, and Ly{alpha} data. For a cross-check, we compare our limits with that obtained through the cosmic microwave background faraday rotation effect and BBN. The limits range between 1.5 nG and 4.5 nG for n{sub B} in (- 3; -1.5).

Kahniashvili, Tina; Natarajan, Aravind; Battaglia, Nicholas [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Maravin, Yurii [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, KS 66506 (United States); Tevzadze, Alexander G., E-mail: tinatin@andrew.cmu.edu [Faculty of Exact and Natural Sciences, Javakhishvili Tbilisi State University, 3 Chavchavadze Avenue, Tbilisi 0128 (Georgia)

2013-06-10T23:59:59.000Z

168

Magnetic fields and radiative feedback in the star formation process  

E-Print Network (OSTI)

Star formation is a complex process involving the interplay of many physical effects, including gravity, turbulent gas dynamics, magnetic fields and radiation. Our understanding of the process has improved substantially in recent years, primarily as a result of our increased ability to incorporate the relevant physics in numerical calculations of the star formation process. In this contribution we present an overview of our recent studies of star cluster formation in turbulent, magnetised clouds using self-gravitating radiation-magnetohydrodynamics calculations (Price and Bate 2008, 2009). Our incorporation of magnetic fields and radiative transfer into the Smoothed Particle Hydrodynamics method are discussed. We highlight how magnetic fields and radiative heating of the gas around newborn stars can solve several of the key puzzles in star formation, including an explanation for why star formation is such a slow and inefficient process. However, the presence of magnetic fields at observed strengths in collaps...

Price, Daniel J

2010-01-01T23:59:59.000Z

169

Magnetic Fields in High-Density Stellar Matter  

E-Print Network (OSTI)

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.

German Lugones

2005-04-20T23:59:59.000Z

170

CONSEQUENCES OF MAGNETIC FIELD STRUCTURE FOR HEAT TRANSPORT IN MAGNETOHYDRODYNAMICS  

SciTech Connect

Interfaces between hot and cold magnetized plasmas exist in various astrophysical contexts, for example, where hot outflows impinge on an ambient interstellar medium. It is of interest to understand how the structure of the magnetic field spanning the interface affects the temporal evolution of the temperature gradient. Here, we explore the relation between the magnetic field topology and the heat transfer rate by adding various fractions of tangled versus ordered field across a hot-cold interface that allows the system to evolve to a steady state. We find a simple mathematical relation for the rate of heat conduction as a function of the initial ratio of ordered-to-tangled field across the interface. We discuss potential implications for the astrophysical context of magnetized wind blown bubbles around evolved stars.

Li Shule; Frank, Adam; Blackman, Eric, E-mail: shuleli@pas.rochester.edu [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States)

2012-03-20T23:59:59.000Z

171

Composite systems in magnetic field: from hadrons to hydrogen atom  

E-Print Network (OSTI)

We briefly review the recent studies of the behavior of composite systems in magnetic field. The hydrogen atom is chosen to demonstrate the new results which may be experimentally tested. Possible applications to physics of antihydrogen are mentioned.

B. O. Kerbikov

2013-12-11T23:59:59.000Z

172

Primordial magnetic fields and formation of molecular hydrogen  

E-Print Network (OSTI)

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.

Shiv K Sethi; Biman B. Nath; Kandaswamy Subramanian

2008-04-22T23:59:59.000Z

173

Analyses of Magnetic-Field Peak-Exposure Summary Measures  

Science Conference Proceedings (OSTI)

Past emphasis on exposure characterization and analyses for magnetic fields has been on measures of central tendency, such as long-term time-weighted average (TWA) exposure. Past emphasis on exposure characterization and analyses for magnetic fields has been on measures of central tendency such as long-term time-weighted average (TWA) exposure. This report examines peak exposure measures such as the maximum and 99th percentile of measurements during a day. EPRI sponsored this study to enhance industry kn...

2003-11-19T23:59:59.000Z

174

Hall effect in a strong magnetic field: Direct comparisons of compressible magnetohydrodynamics and the reduced Hall magnetohydrodynamic equations  

SciTech Connect

In this work we numerically test a model of Hall magnetohydrodynamics in the presence of a strong mean magnetic field: the reduced Hall magnetohydrodynamic model (RHMHD) derived by [Gomez et al., Phys. Plasmas 15, 102303 (2008)] with the addition of weak compressible effects. The main advantage of this model lies in the reduction of computational cost. Nevertheless, up until now the degree of agreement with the original Hall MHD system and the range of validity in a regime of turbulence were not established. In this work direct numerical simulations of three-dimensional Hall MHD turbulence in the presence of a strong mean magnetic field are compared with simulations of the weak compressible RHMHD model. The results show that the degree of agreement is very high (when the different assumptions of RHMHD, such as spectral anisotropy, are satisfied). Nevertheless, when the initial conditions are isotropic but the mean magnetic field is maintained strong, the results differ at the beginning but asymptotically reach a good agreement at relatively short times. We also found evidence that the compressibility still plays a role in the dynamics of these systems, and the weak compressible RHMHD model is able to capture these effects. In conclusion the weak compressible RHMHD model is a valid approximation of the Hall MHD turbulence in the relevant physical context.

Martin, L. N.; Dmitruk, P. [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina) and IFIBA, CONICET, Ciudad Universitaria, 1428 Buenos Aires (Argentina); Gomez, D. O. [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina) and IFIBA, CONICET, Ciudad Universitaria, 1428 Buenos Aires (Argentina); Instituto de Astronomia y Fisica del Espacio, Ciudad Universitaria, 1428 Buenos Aires (Argentina)

2010-11-15T23:59:59.000Z

175

2-3 High Field Magnetic Resonance Facility  

NLE Websites -- All DOE Office Websites (Extended Search)

HFMRF Overview HFMRF Overview High Field Magnetic Resonance Facility A significant portion of research conducted in the High Field Magnetic Resonance Facility (HFMRF) focuses on developing a fundamental, molecular-level understanding of biochemi- cal and biological systems and their response to environmental effects. A secondary focus is in materials science and catalysis and the chemical mechanisms and processes that operate in these areas. Resident and matrixed research staff within this facility offer expertise in the areas of structural biology, solid-state materials characterization, and magnetic resonance imaging (MRI) techniques. Instrumentation & Capabilities NMR * 900-MHz NMR (operational in 2004) * 800-MHz NMR * 750-MHz NMR * 600-MHz NMR (2 systems)

176

MRS Photodiode, LED and extruded scintillator performance in magnetic field  

SciTech Connect

The experimental results on the performance of the MRS (Metal/Resistor/Semiconductor) photodiode in the strong magnetic field of 4.4T, and the possible impact of the quench of the magnet at 4.5T on sensor's operation are reported. In addition, the experimental results on the performance of the extruded scintillator and WLS fiber, and various LEDs in the magnetic fields of 1.8T and 2.3T respectively, are detailed. The measurement method used is being described.

Beznosko, D.; Blazey, G.; Dyshkant, A.; Francis, K.; Kubik, D.; Rykalin, V.; Zutshi, V.; /Northern Illinois U.

2005-05-01T23:59:59.000Z

177

Fluorescent lamp unit with magnetic field generating means  

DOE Patents (OSTI)

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.

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

1989-08-08T23:59:59.000Z

178

Study of HTS Wires at High Magnetic Fields  

SciTech Connect

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.

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

2009-01-01T23:59:59.000Z

179

Electrons Confined with an Axially Symmetric Magnetic Mirror Field  

Science Conference Proceedings (OSTI)

Low energy non-neutral electron plasmas were confined with an axially symmetric magnetic mirror field and an electrostatic potential to investigate the basic confinement properties of a simple magnetic mirror trap. As expected the confinement time became longer as a function of the mirror ratio. The axial electrostatic oscillations of a confined electron plasma were also observed. Obtained results suggested an improved scheme to accumulate low energy charged particles with the use of a magnetic mirror field, which would enable the investigation of electron-positron plasmas.

Higaki, H.; Ito, K.; Kira, K.; Okamoto, H. [Graduate School of Advanced Sciences of Matter, Hiroshima University 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8530 (Japan)

2008-08-08T23:59:59.000Z

180

Influence of external magnetic and laser radiation fields on Feshbach resonances in collision of atoms  

E-Print Network (OSTI)

We study collision of two atoms with formation of Feshbach resonance at combined interaction with the external magnetic field and laser radiation. In cases of one- and two-photon resonances of laser radiation with two discrete vibrational molecular levels, we show that Feshbach resonances appear at interaction of external magnetic field with dressed states formed via Autler-Townes effect. In addition, in case of one-photon resonance the lower vibrational molecular state is coupled by laser radiation with the continuum of the elastic channel and forms laser-induced Feshbach resonance via both Autler-Townes effect and LICS mechanism. We study the combined process of formation of Feshbach resonances; this enables the control of Feshbach resonance by varying the magnetic field and intensity and frequency of laser radiation. We obtain the cross-sections of elastic and inelastic scattering and show that quenching of resonance occurs at the energy equal to that of the systems ground state. Dependence of the cross-sections on the magnetic field and laser intensity is examined in detail. In all considered cases, the scattering length is obtained depending on the magnetic and laser fields are studied. In the absence of magnetic interaction if the hyperfine substates of the quasibound state in the closed channel and those of individual colliding atoms in the open channel are the same, Feshbach resonances may arise via weak interaction between nuclear and electronic motions, which leads to transitions between electronic states. The obtained results can be employed in new studies of collisions of cold atoms, e.g., of alkali metal atoms and for interpretation of new experiments in BECs.

E. A. Gazazyan; A. D. Gazazyan; V. O. Chaltykyan

2012-09-21T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


181

Magnetic field switching in parallel quantum dots  

E-Print Network (OSTI)

We show that the Coulomb blockade in parallel dots pierced by magnetic flux $\\Phi$ completely blocks the resonant current for any value of $\\Phi$ except for integer multiples of the flux quantum $\\Phi_0$. This non-analytic (switching) dependence of the current on $\\Phi$ arises only when the dot states that carry the current are of the same energy. The time needed to reach the steady state, however, diverges when $\\Phi\\to n\\Phi_0$.

Feng Li; Xin-Qi Li; Wei-Min Zhang; S. A. Gurvitz

2008-03-11T23:59:59.000Z

182

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

DOE Green Energy (OSTI)

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.

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

1991-01-01T23:59:59.000Z

183

Photon and Axion Splitting in an Inhomogeneous Magnetic Field  

E-Print Network (OSTI)

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.

E. I. Guendelman

2008-02-03T23:59:59.000Z

184

Vacuum pressures and energy in a strong magnetic field  

E-Print Network (OSTI)

We study vacuum in a strong magnetic field. It shows a nonlinear response, as a ferromagnetic medium. Anisotropic pressures arise, and a negative pressure is exerted in the direction perpendicular to the field. The analogy of this effect with the Casimir effect is analyzed. The vacuum transverse pressure is found to be of the same order of the statistical pressure for $B\\sim10^{15}G$ and $N\\sim10^{33}electrons/cm^{3}$. Vacuum interaction with the field is studied also for $B\\sim10^{16}G$ and larger, including the electron anomalous magnetic moment. We estimate quark contribution to vacuum behavior.

H. Perez Rojas; E. Rodriguez Querts

2004-06-25T23:59:59.000Z

185

Atomic magnetic gradiometer for room temperature high sensitivity magnetic field detection  

DOE Patents (OSTI)

A laser-based atomic magnetometer (LBAM) apparatus measures magnetic fields, comprising: a plurality of polarization detector cells to detect magnetic fields; a laser source optically coupled to the polarization detector cells; and a signal detector that measures the laser source after being coupled to the polarization detector cells, which may be alkali cells. A single polarization cell may be used for nuclear magnetic resonance (NMR) by prepolarizing the nuclear spins of an analyte, encoding spectroscopic and/or spatial information, and detecting NMR signals from the analyte with a laser-based atomic magnetometer to form NMR spectra and/or magnetic resonance images (MRI). There is no need of a magnetic field or cryogenics in the detection step, as it is detected through the LBAM.

Xu,Shoujun (Berkeley, CA); Lowery, Thomas L. (Belmont, MA); Budker, Dmitry (El Cerrito, CA); Yashchuk, Valeriy V. (Richmond, CA); Wemmer, David E. (Berkeley, CA); Pines, Alexander (Berkeley, CA)

2009-08-11T23:59:59.000Z

186

Stability of the toroidal magnetic field in rotating stars  

E-Print Network (OSTI)

The magnetic field in stellar radiation zones can play an important role in phenomena such as mixing, angular momentum transport, etc. We study the effect of rotation on the stability of a predominantly toroidal magnetic field in the radiation zone. In particular we considered the stability in spherical geometry by means of a linear analysis in the Boussinesq approximation. It is found that the effect of rotation on the stability depends on a magnetic configuration. If the toroidal field increases with the spherical radius, the instability cannot be suppressed entirely even by a very fast rotation. Rotation can only decrease the growth rate of instability. If the field decreases with the radius, the instability has a threshold and can be completey suppressed.

Bonanno, Alfio

2013-01-01T23:59:59.000Z

187

Non-axisymmetric instability of axisymmetric magnetic fields  

E-Print Network (OSTI)

The MHD instabilities can generate complex field topologies even if the initial field configuration is a very simple one. We consider the stability properties of magnetic configurations containing a toroidal and an axial field. In this paper, we concentrate mainly on the behavior of non-axisymmetric perturbations in axisymmetric magnetic configurations. The stability is treated by a linear analysis of ideal MHD equations.In the presence of an axial field, it is shown that the instability can occur for a wide range of the azimuthal wavenumber $m$, and its growth rate increases with increasing $m$. At given $m$, the growth rate is at its maximum for perturbations with the axial wave-vector that makes the Alfv\\'en frequency approximately vanishing. We argue that the instability of magnetic configurations in the ideal MHD can typically be dominated by perturbations with very short azimuthal and axial wavelengths.

Bonanno, Alfio

2008-01-01T23:59:59.000Z

188

Magnetic field switching in parallel quantum dots  

E-Print Network (OSTI)

We show that the Coulomb blockade in parallel dots pierced by magnetic flux $\\Phi$ completely blocks the resonant current for any value of $\\Phi$ except for integer multiples of the flux quantum $\\Phi_0$. This non-analytic (switching) dependence of the current on $\\Phi$ arises only when the dot states that carry the current are of the same energy. The time needed to reach the steady state, however, diverges when $\\Phi\\to n\\Phi_0$. This current switch effect can find application in nano-circuit devices.

Li, Feng; Zhang, Wei-Min; Gurvitz, S A

2008-01-01T23:59:59.000Z

189

MAGNETIC FIELD INTENSIFICATION BY THE THREE-DIMENSIONAL 'EXPLOSION' PROCESS  

Science Conference Proceedings (OSTI)

We investigate an intensification mechanism for the magnetic field near the base of the solar convection zone that does not rely on differential rotation. Such mechanism in addition to differential rotation has been suggested by studies of flux emergence, which typically require field strength in excess of those provided by differential rotation alone. We study here a process in which potential energy of the superadiabatically stratified convection zone is converted into magnetic energy. This mechanism, known as the 'explosion of magnetic flux tubes', has been previously studied in thin flux tube approximation as well as two-dimensional magnetohydrodynamic (MHD) simulations; here we expand the investigation to three-dimensional MHD simulations. Our main result is that enough intensification can be achieved in a three-dimensional magnetic flux sheet as long as the spatial scale of the imposed perturbation normal to the magnetic field is sufficiently large. When this spatial scale is small, the flux sheet tends to rise toward the surface, resulting in a significant decrease of the magnetic field amplification.

Hotta, H.; Yokoyama, T. [Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Rempel, M., E-mail: hotta.h@eps.s.u-tokyo.ac.jp [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307 (United States)

2012-11-01T23:59:59.000Z

190

Edge states induced by Iwatsuka Hamiltonians with positive magnetic fields  

E-Print Network (OSTI)

We study purely magnetic Schr\\"odinger operators in two-dimensions $(x,y)$ with magnetic fields $b(x)$ that depend only on the $x$-coordinate. The magnetic field $b(x)$ is assumed to be bounded, there are constants $0 \\epsilon$. The case of a jump in the magnetic field at $x=0$ corresponding to $\\epsilon=0$ is also studied. We prove that the magnetic field creates an effective barrier near $x=0$ that causes edge currents to flow along it consistent with the classical interpretation. We prove lower bounds on edge currents carried by states with energy localized inside the energy bands of the Hamiltonian. We prove that these edge current-carrying states are well-localized in $x$ to a region of size $b_-^{-1/2}$, also consistent with the classical interpretation. We demonstrate that the edge currents are stable with respect to various magnetic and electric perturbations. For a family of perturbations compactly supported in the $y$-direction, we prove that the time asymptotic current exists and satisfies the same lower bound.

Peter D. Hislop; Eric Soccorsi

2013-07-23T23:59:59.000Z

191

Influence of the Earth's magnetic field on large area photomultipliers  

SciTech Connect

The influence of the Earth's magnetic field on large area photomultipliers proposed for a future deep sea neutrino telescope was studied under the EU-funded KM3NeT design study. The aims were to evaluate variations in PMT performance in the Earth's magnetic field and to decide whether the use of magnetic shielding is necessary. Measurements were performed on three Hamamatsu PMTs: two 8-inch R5912 types, one of these with super-bi-alkali photocathode, and a 10-inch R7081 type with a standard bi-alkali photocathode. The various characteristics of the PMTs were measured while varying the PMT orientations with respect to the Earth's magnetic field, both with and without a mu-metal cage as magnetic shield. In the 8-inch PMTs the impact of the magnetic field was found to be smaller than that on the 10-inch PMT. The increased quantum efficiency in the 8 super-bi-alkali PMT almost compensated its smaller detection surface compared to the 10' PMT. No significant effects were measured upon transit time and the fraction of spurious pulses. (authors)

Leonora, E.; Aiello, S. [INFN - National Inst. of Nuclear Physics, Section of Catania, CO Via Santa Sofia 64, 95123 Catania (Italy); Leotta, G. [Dept. of Physics and Astronomy of Catania, CO Via Santa Sofia 64, 95123 Catania (Italy)

2011-07-01T23:59:59.000Z

192

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

SciTech Connect

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.

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

193

Impact of tangled magnetic fields on AGN-blown bubbles  

E-Print Network (OSTI)

There is growing consensus that feedback from AGN is the main mechanism responsible for stopping cooling flows in clusters of galaxies. AGN are known to inflate buoyant bubbles that supply mechanical power to the intracluster gas (ICM). High Reynolds number hydrodynamical simulations show that such bubbles get entirely disrupted within 100 Myr, as they rise in cluster atmospheres, which is contrary to observations. This artificial mixing has consequences for models trying to quantify the amount of heating and star formation in cool core clusters of galaxies. It has been suggested that magnetic fields can stabilize bubbles against disruption. We perform MHD simulations of fossil bubbles in the presence of tangled magnetic fields using the high order PENCIL code. We focus on the physically-motivated case where thermal pressure dominates over magnetic pressure and consider randomly oriented fields with and without maximum helicity and a case where large scale external fields drape the bubble.We find that helicity has some stabilizing effect. However, unless the coherence length of magnetic fields exceeds the bubble size, the bubbles are quickly shredded. As observations of Hydra A suggest that lengthscale of magnetic fields may be smaller then typical bubble size, this may suggest that other mechanisms, such as viscosity, may be responsible for stabilizing the bubbles. However, since Faraday rotation observations of radio lobes do not constrain large scale ICM fields well if they are aligned with the bubble surface, the draping case may be a viable alternative solution to the problem. A generic feature found in our simulations is the formation of magnetic wakes where fields are ordered and amplified. We suggest that this effect could prevent evaporation by thermal conduction of cold Halpha filaments observed in the Perseus cluster.

M. Ruszkowski; T. A. Ensslin; M. Bruggen; S. Heinz; C. Pfrommer

2007-03-30T23:59:59.000Z

194

ON THE ORIGIN OF THE 1/f SPECTRUM IN THE SOLAR WIND MAGNETIC FIELD  

Science Conference Proceedings (OSTI)

We present a mechanism for the formation of the low-frequency 1/f magnetic spectrum based on numerical solutions of a shell-reduced MHD model of the turbulent dynamics inside the sub-Alfvenic solar wind. We assign reasonably realistic profiles to the wind speed and the density along the radial direction, and a radial magnetic field. Alfven waves of short periodicity (600 s) are injected at the base of the chromosphere, penetrate into the corona, and are partially reflected, thus triggering a turbulent cascade. The cascade is strong for the reflected wave while it is weak for the outward propagating waves. Reflection at the transition region recycles the strong turbulent spectrum into the outward weak spectrum, which is advected beyond the Alfvenic critical point without substantial evolution. There, the magnetic field has a perpendicular power-law spectrum with slope close to the Kolmogorov -5/3. The parallel spectrum is inherited from the frequency spectrum of large (perpendicular) eddies. The shape is a double power law with slopes of {approx_equal} - 1 and -2 at low and high frequencies, respectively, with the position of the break depending on the injected spectrum. We suggest that the double power-law spectrum measured by Helios at 0.3 AU, where the average magnetic field is not aligned with the radial (contrary to our assumptions), results from the combination of such different spectral slopes. At low frequency the parallel spectrum dominates with its characteristic 1/f shape, while at higher frequencies its steep spectral slope (-2) is masked by the more energetic perpendicular spectrum (slope -5/3).

Verdini, Andrea [Solar-Terrestrial Center of Excellence-SIDC, Royal Observatory of Belgium, Bruxelles (Belgium); Grappin, Roland [LUTH, Observatoire de Paris, CNRS, Universite Paris-Diderot, 92190 Meudon (France); Pinto, Rui [Laboratoire AIM Paris-Saclay, CEA/Irfu, and Universite Paris-Diderot CNRS/INSU, Gis-sur-Yvette (France); Velli, Marco, E-mail: verdini@oma.be, E-mail: Roland.Grappin@obspm.fr, E-mail: rui.pinto@cea.fr, E-mail: mvelli@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA (United States)

2012-05-10T23:59:59.000Z

195

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

E-Print Network (OSTI)

costs given magnet stored-energy or average bore induction timecost will go up with stored energy and with field volume timesCost of Superconducting Magnets as a Function of Stored Energy and Design Magnetic Induction times

Green, M.A.

2008-01-01T23:59:59.000Z

196

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

E-Print Network (OSTI)

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 ...

Karim, Ishtak

2007-01-01T23:59:59.000Z

197

FIRST SIMULTANEOUS DETECTION OF MOVING MAGNETIC FEATURES IN PHOTOSPHERIC INTENSITY AND MAGNETIC FIELD DATA  

SciTech Connect

The formation and the temporal evolution of a bipolar moving magnetic feature (MMF) was studied with high-spatial and temporal resolution. The photometric properties were observed with the New Solar Telescope at Big Bear Solar Observatory using a broadband TiO filter (705.7 nm), while the magnetic field was analyzed using the spectropolarimetric data obtained by Hinode. For the first time, we observed a bipolar MMF simultaneously in intensity images and magnetic field data, and studied the details of its structure. The vector magnetic field and the Doppler velocity of the MMF were also studied. A bipolar MMF with its positive polarity closer to the negative penumbra formed, accompanied by a bright, filamentary structure in the TiO data connecting the MMF and a dark penumbral filament. A fast downflow ({<=}2 km s{sup -1}) was detected at the positive polarity. The vector magnetic field obtained from the full Stokes inversion revealed that a bipolar MMF has a U-shaped magnetic field configuration. Our observations provide a clear intensity counterpart of the observed MMF in the photosphere, and strong evidence of the connection between the MMF and the penumbral filament as a serpentine field.

Lim, Eun-Kyung; Yurchyshyn, Vasyl; Goode, Philip, E-mail: eklim@bbso.njit.edu [Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314-9672 (United States)

2012-07-01T23:59:59.000Z

198

Dissipative Taylor-Couette flows under the influence of helical magnetic fields  

E-Print Network (OSTI)

The linear stability of MHD Taylor-Couette flows in axially unbounded cylinders is considered, for magnetic Prandtl number unity. Magnetic fields varying from purely axial to purely azimuthal are imposed, with a general helical field parameterized by \\beta=B_\\phi/B_z. We map out the transition from the standard MRI for \\beta=0 to the nonaxisymmetric Azimuthal MagnetoRotational Instability (AMRI) for \\beta\\to \\infty. For finite \\beta, positive and negative wave numbers m, corresponding to right and left spirals, are no longer identical. The transition from \\beta=0 to \\beta\\to\\infty includes all the possible forms of MRI with axisymmetric and nonaxisymmetric modes. For the nonaxisymmetric modes, the most unstable mode spirals in the opposite direction to the background field. The standard (\\beta=0) MRI is axisymmetric for weak fields (including the instability with the lowest Reynolds number) but is nonaxisymmetric for stronger fields. If the azimuthal field is due in part to an axial current flowing through th...

Ruediger, G; Schultz, M; Hollerbach, R

2010-01-01T23:59:59.000Z

199

MAGNETIC FIELD STRUCTURES TRIGGERING SOLAR FLARES AND CORONAL MASS EJECTIONS  

SciTech Connect

Solar flares and coronal mass ejections, the most catastrophic eruptions in our solar system, have been known to affect terrestrial environments and infrastructure. However, because their triggering mechanism is still not sufficiently understood, our capacity to predict the occurrence of solar eruptions and to forecast space weather is substantially hindered. Even though various models have been proposed to determine the onset of solar eruptions, the types of magnetic structures capable of triggering these eruptions are still unclear. In this study, we solved this problem by systematically surveying the nonlinear dynamics caused by a wide variety of magnetic structures in terms of three-dimensional magnetohydrodynamic simulations. As a result, we determined that two different types of small magnetic structures favor the onset of solar eruptions. These structures, which should appear near the magnetic polarity inversion line (PIL), include magnetic fluxes reversed to the potential component or the nonpotential component of major field on the PIL. In addition, we analyzed two large flares, the X-class flare on 2006 December 13 and the M-class flare on 2011 February 13, using imaging data provided by the Hinode satellite, and we demonstrated that they conform to the simulation predictions. These results suggest that forecasting of solar eruptions is possible with sophisticated observation of a solar magnetic field, although the lead time must be limited by the timescale of changes in the small magnetic structures.

Kusano, K.; Bamba, Y.; Yamamoto, T. T. [Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 (Japan); Iida, Y.; Toriumi, S. [Department of Earth and Planetary Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Asai, A., E-mail: kusano@nagoya-u.jp [Unit of Synergetic Studies for Space, Kyoto University, 17 Kitakazan Ohmine-cho, Yamashina-ku, Kyoto 607-8471 (Japan)

2012-11-20T23:59:59.000Z

200

Towards Integrated Design and Modeling of High Field Accelerator Magnets  

SciTech Connect

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.

Caspi, S.; Ferracin, P.

2006-06-01T23:59:59.000Z

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201

Enhancement of accelerating field of microwave cavities by magnetic insulation  

Science Conference Proceedings (OSTI)

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.

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

2011-04-15T23:59:59.000Z

202

Molecular cloud formation and magnetic fields in spiral galaxies  

E-Print Network (OSTI)

We present ongoing hydrodynamic and MHD simulations of molecular cloud formation in spiral galaxies. The hydrodynamic results show the formation of molecular gas clouds where spiral shocks compress atomic gas to high densities. The spiral shocks also produce structure in the spiral arms, provided the gas is cold (gas than when a single phase is assumed. We also discuss very recent results from galactic-scale MHD calculations. From observational comparisons of the magnetic and thermal pressure, magnetic fields are expected to be a major factor in explaining the dynamics of the ISM, from kpc scales to those of star formation. We describe the difference in structure of the spiral arms, and the evolution of the global magnetic field for a range of field strengths.

Clare Dobbs; Daniel Price; Ian Bonnell

2007-06-26T23:59:59.000Z

203

Particle energization through time-periodic helical magnetic fields  

E-Print Network (OSTI)

We solve for the motion of charged particles in a helical time-periodic ABC (Arnold-Beltrami-Childress) magnetic field. The magnetic field lines of a stationary ABC field with $A=B=C=1$ are chaotic, and we show that the motion of a charged particle in such a field is also chaotic at late time with positive Lyapunov exponent. We further show that in time-periodic (frequency $\\omega$) ABC fields the kinetic energy of a charged particle can increase indefinitely with time. At late times the mean kinetic energy grows as a power law in time with exponent $\\xi$ that approaches unity. For an initial distribution of particles, whose kinetic energy is uniformly distributed within some interval, the PDF of kinetic energy is, at late time, close to a Gaussian but with steeper tails.

Dhrubaditya Mitra; Axel Brandenburg; Brahmananda Dasgupta; Eyvind Niklasson; Abhay Ram

2013-06-01T23:59:59.000Z

204

Effects of fringing magnetic fields on MHD seawater thruster performance  

DOE Green Energy (OSTI)

There are several loss mechanisms that influence the flow and electrical field characteristics of an MHD seawater thruster and hence its performance. Among those losses are the jet losses, ohmic losses, three-dimensional effects, and electrical end losses. Some of those loss mechanisms have been discussed before, together with the parameters affecting the thruster performance. Thruster electrical end losses are caused by the fringing of the magnetic field near the ends of the electrodes, and by the nonuniformity of the current and electric fields across the thruster, particularly near the ends of the electrodes. Therefore, the current density cannot be calculated from a simple one-dimensional relationship. Rather, a multi-dimensional solution of the electric fields should be performed. No simple expression can be written for the electrical end losses, because end effects depend on several parameters that include the thruster aspect ratio, load factor and the profile of the magnetic field in the fringe region away from the electrodes.

Doss, E.D.; Geyer, H.K.

1992-01-01T23:59:59.000Z

205

Effects of fringing magnetic fields on MHD seawater thruster performance  

DOE Green Energy (OSTI)

There are several loss mechanisms that influence the flow and electrical field characteristics of an MHD seawater thruster and hence its performance. Among those losses are the jet losses, ohmic losses, three-dimensional effects, and electrical end losses. Some of those loss mechanisms have been discussed before, together with the parameters affecting the thruster performance. Thruster electrical end losses are caused by the fringing of the magnetic field near the ends of the electrodes, and by the nonuniformity of the current and electric fields across the thruster, particularly near the ends of the electrodes. Therefore, the current density cannot be calculated from a simple one-dimensional relationship. Rather, a multi-dimensional solution of the electric fields should be performed. No simple expression can be written for the electrical end losses, because end effects depend on several parameters that include the thruster aspect ratio, load factor and the profile of the magnetic field in the fringe region away from the electrodes.

Doss, E.D.; Geyer, H.K.

1992-07-01T23:59:59.000Z

206

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

E-Print Network (OSTI)

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 for actuator applications, and can be employed as sensors/power-harvesters due to their capability to convert mechanical stimuli into magnetic response or vice versa. The purpose of the present work was to investigate magneto-thermo-mechanical (MTM) response of various MSMAs, under simultaneously applied magnetic field, heat and stress. To accomplish this, two novel testing systems which allowed absolute control on magnetic field and stress/strain in a wide and stable range of temperature were designed and manufactured. MTM characterization of MSMAs enabled us to determine the effects of main parameters on reversible magnetic field-induced phase transformation (FIPT), such as magnetocrystalline anisotropy energy, Zeeman energy, stress hysteresis, thermal hysteresis, critical stress to start stress induced phase transformation and crystal orientation. Conventional SMA characteristics of single crystalline Ni2MnGa and NiMnCoIn and polycrystalline NiMnCoAl and NiMnCoSn MSMAs were investigated using the macroscopic MTM testing system to reveal how these conventional properties were linked to magnetic-field-induced actuation. An actuation stress of 5 MPa and a work output of 157 kJm?3 were obtained by the field-induced martensite variant reorientation (VR) in NiMnGa alloys. FIPT was investigated both in Ni2MnGa MSMA and in NiMnCoIn metamagnetic SMA. It proved as an alternative governing mechanism of field-induced shape change to VR in Ni2MnGa single crystals: one-way and reversible (0.5% cyclic magnetic field induced strain (MFIS) under 22 MPa) stress-assisted FIPTs were realized under low field magnitudes (power by means of VR in NiMnGa MSMAs was explored: without enhanced pickup coil parameters or optimized power conditioning circuitry, 280 mV was harvested at 10 Hz frequency within a strain range of 4.9%. For the first time in magnetic shape memory alloys literature, a fully recoverable MFIS of 3% under 125 MPa was attained on single crystalline metamagnetic SMA NiMnCoIn by means of our microscopic MTM testing system to understand the evolution of FIPT under simultaneously applied magnetic field and stress. Conventional SMA characteristics of polycrystalline bulk NiMnCoAl and sintered compacted-powder NiMnCoSn metamagnetic SMAs were also investigated, with and without applied field.

Basaran, Burak

2009-12-01T23:59:59.000Z

207

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

Science Conference Proceedings (OSTI)

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.

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

1999-05-01T23:59:59.000Z

208

Green Bank Telescope observations of the water masers of NGC 3079: accretion disk magnetic field and maser scintillation  

E-Print Network (OSTI)

We present observations of the 22 GHz water megamasers in the circumnuclear disk of NGC 3079 obtained with the Green Bank Telescope. The data are analyzed for circular polarization due to the Zeeman-induced splitting of the water maser lines. No circular polarization is detected and we derive a 1 sigma upper limit of 11 mG for the toroidal magnetic field at ~0.64 pc from the central black hole. This is the tightest upper limit for the magnetic field around a black hole to date. We use the magnetic field limit to derive an estimate of the mass accretion onto the central black hole. In addition to the polarimetric results, we present an observation of rapid variability in the maser lines, which we explain as weak interstellar scintillation. From the scintillation parameters, we estimate an intrinsic size of the mostly saturated maser features of ~12 microarcseconds. This is consistent with models assuming a thick, clumpy accretion disk.

W. H. T. Vlemmings; H. E. Bignall; P. J. Diamond

2006-10-30T23:59:59.000Z

209

On the ordering of energy levels in homogeneous magnetic fields  

E-Print Network (OSTI)

We study the energy levels of a single particle in a homogeneous magnetic field and in an axially symmetric external potential. For potentials that are superharmonic off the central axis, we find a general ``pseudoconcave'' ordering of the ground state energies of the Hamiltonian restricted to the sectors with fixed angular momentum. The physical applications include atoms and ions in strong magnetic fields. There the energies are monotone increasing and concave in angular momentum. In the case of a periodic chain of atoms the pseudoconcavity extends to the entire lowest band of Bloch functions.

Bernhard Baumgartner; Robert Seiringer

2000-11-17T23:59:59.000Z

210

Direct observation of Oersted-field-induced magnetization dynamics in magnetic nanostripes  

Science Conference Proceedings (OSTI)

We have used time-resolved x-ray photoemission electron microscopy to investigate the magnetization dynamics induced by nanosecond current pulses in NiFe/Cu/Co nanostripes. A large tilt of the NiFe magnetization in the direction transverse to the stripe is observed during the pulses. We show that this effect cannot be quantitatively understood from the amplitude of the Oersted field and the shape anisotropy. High-frequency oscillations observed at the onset of the pulses are attributed to precessional motion of the NiFe magnetization about the effective field. We discuss the possible origins of the large magnetization tilt and the potential implications of the static and dynamic effects of the Oersted field on current-induced domain-wall motion in such stripes.

Uhlir, V. [Institut Neel, Centre national de la recherche scientifique and Universite Joseph Fourier, BP166, F-38042 Grenoble (France); Institute of Physical Engineering, Brno University of Technology, CZ-61669 Brno (Czech Republic); Pizzini, S.; Rougemaille, N.; Ranno, L.; Fruchart, O.; Wagner, E.; Vogel, J. [Institut Neel, Centre national de la recherche scientifique and Universite Joseph Fourier, BP166, F-38042 Grenoble (France); Cros, V. [Unite Mixte de Physique CNRS-Thales, Route departementale 128, F-91767 Palaiseau Cedex (France); Jimenez, E.; Camarero, J. [Departamento Fisica de la Materia Condensada, Instituto ''Nicolas Cabrera'' and Instituto Madrileno de Estudios Avanzados-Nanociencia, Campus Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Urbanek, M. [Institute of Physical Engineering, Brno University of Technology, CZ-61669 Brno (Czech Republic); Gaudin, G. [SPINTEC, UMR8191 CEA/CNRS/UJF/Grenoble INP, INAC, F-38045 Grenoble (France); Tieg, C. [European Synchrotron Radiation Facility, BP200, F-38043 Grenoble (France); Sirotti, F. [Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin, F-91192 Gif-sur-Yvette (France)

2011-01-15T23:59:59.000Z

211

Homogenous BSCCO-2212 Round Wires for Very High Field Magnets  

Science Conference Proceedings (OSTI)

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

Dr. Scott Campbell Dr. Terry Holesinger Dr. Ybing Huang

2012-06-30T23:59:59.000Z

212

POLOIDAL MAGNETIC FIELD TOPOLOGY FOR TOKAMAKS WITH CURRENT HOLES  

Science Conference Proceedings (OSTI)

The appearance of hole currents in tokamaks seems to be very important in plasma confinement and on-set of instabilities, and this paper is devoted to study the topology changes of poloidal magnetic fields in tokamaks. In order to determine these fields different models for current profiles can be considered. It seems to us, that one of the best analytic descriptions is given by V. Yavorskij et al., which has been chosen for the calculations here performed. Suitable analytic equations for the family of magnetic field surfaces with triangularity and Shafranov shift are written down here. The topology of the magnetic field determines the amount of trapped particles in the generalized mirror type magnetic field configurations. Here it is found that the number of maximums and minimums of Bp depends mainly on triangularity, but the pattern is also depending of the existence or not of hole currents. Our calculations allow comparing the topology of configurations of similar parameters, but with and without whole currents. These differences are study for configurations with equal ellipticity but changing the triangularity parameters. Positive and negative triangularities are considered and compared between them.

Puerta, Julio; Martin, Pablo; Castro, Enrique [Universidad Simon Bolivar, Departamento de Fisica, Plasma Physics Laboratory, Caracas (Venezuela, Bolivarian Republic of)

2009-07-26T23:59:59.000Z

213

Stability of magnetic configurations containing the toroidal and axial fields  

E-Print Network (OSTI)

Stability properties of magnetic-field configurations containing the toroidal and axial field are considered. The stability is treated by making use of linear analysis. It is shown that the conditions required for the onset of instability are essentially different from those given by the necessary condition $d (s B_{\\phi})/ds > 0$, where $s$ is the cylindrical radius. The growth rate of instability is calculated for a wide range of the parameters. We argue that the instability can operate in two different regimes depending on the strength of the axial field and the profile of the toroidal field.

Bonanno, Alfio

2007-01-01T23:59:59.000Z

214

Kinetic models of current sheets with a sheared magnetic field  

Science Conference Proceedings (OSTI)

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.

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

215

Strongest non-destructive magnetic field: world record set at 100-tesla  

NLE Websites -- All DOE Office Websites (Extended Search)

Strongest non-destructive magnetic field: world record set at Strongest non-destructive magnetic field: world record set at 100-tesla level Strongest non-destructive magnetic field: world record set at 100-tesla level National High Magnetic Field Laboratory magnet achieved a whopping 100.75 tesla-the 100-tesla level is roughly equivalent to 2 million times Earth's magnetic field. March 22, 2012 World record set at National High Magnetic Field Laboratory, Los Alamos In 2011, researchers at the National High Magnetic Field Laboratory set a new world record for the strongest nondestructive magnet field: 97.4 tesla. The feat positioned them to in March 2012 deliver a magnet capable of achieving the elusive 100-tesla goal, profoundly affecting a range of scientific investigations. Get Expertise Director, Pulsed Field Facility

216

SOLAR MAGNETIC FIELD REVERSALS AND THE ROLE OF DYNAMO FAMILIES  

SciTech Connect

The variable magnetic field of the solar photosphere exhibits periodic reversals as a result of dynamo activity occurring within the solar interior. We decompose the surface field as observed by both the Wilcox Solar Observatory and the Michelson Doppler Imager into its harmonic constituents, and present the time evolution of the mode coefficients for the past three sunspot cycles. The interplay between the various modes is then interpreted from the perspective of general dynamo theory, where the coupling between the primary and secondary families of modes is found to correlate with large-scale polarity reversals for many examples of cyclic dynamos. Mean-field dynamos based on the solar parameter regime are then used to explore how such couplings may result in the various long-term trends in the surface magnetic field observed to occur in the solar case.

DeRosa, M. L. [Lockheed Martin Solar and Astrophysics Laboratory, 3251 Hanover St. B/252, Palo Alto, CA 94304 (United States); Brun, A. S. [Laboratoire AIM Paris-Saclay, CEA/Irfu Universite Paris-Diderot CNRS/INSU, F-91191 Gif-sur-Yvette (France); Hoeksema, J. T. [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)

2012-09-20T23:59:59.000Z

217

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

DOE Patents (OSTI)

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.

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

218

Self-Generated Magnetic Fields in Galactic Cooling Flows  

E-Print Network (OSTI)

Interstellar magnetic fields in elliptical galaxies are assumed to have their origin in stellar fields that accompany normal mass loss from an evolving population of old stars. The seed fields are amplified by interstellar turbulence driven by stellar mass loss and supernova events. These disordered fields are further amplified by time-dependent compression in the inward moving galactic cooling flow and are expected to dominate near the galactic core. Under favorable circumstances, fields similar in strength to those observed $B \\sim 1-10~(r/10~kpc)^{-1.2}\\mu$G can be generated solely from these natural galactic processes. In general the interstellar field throughout elliptical galaxies is determined by the outermost regions in the interstellar gas where the turbulent dynamo process can occur. Because of the long hydrodynamic flow times in galactic cooling flows, currently observed magnetic fields may result from periods of intense turbulent field amplification that occurred in the outer galaxy in the distant past. Particularly strong fields in ellipticals may result from ancient galactic mergers or shear turbulence introduced at the boundary between the interstellar gas and ambient cluster gas.

William G. Mathews; Fabrizio Brighenti

1997-06-10T23:59:59.000Z

219

On magnetic-field-induced dissipationless electric current in nanowires  

E-Print Network (OSTI)

We propose a general design of a metallic double-nanowire structure which may support an equilibrium dissipationless electric current in the presence of magnetic field. The structure consists of a compact wire element of a specific shape, which is periodically extended in one spatial dimension. Topologically, each wire element is equivalent to a ring, which supports a dissipationless current in the presence of magnetic flux similarly to the persistent electric current in a normal metal nanoring. Geometrically, each wire element breaks spatial inversion symmetry so that the equilibrium electric current through the device becomes nonzero. We also argue that the same effect should exist in long planar chiral nanoribbons subjected to external magnetic field.

M. N. Chernodub

2013-03-28T23:59:59.000Z

220

Energy Spectrum of Anyons in a Magnetic Field  

E-Print Network (OSTI)

For the many-anyon system in external magnetic field, we derive the energy spectrum as an exact solution of the quantum eigenvalue problem with particular topological constraints. Our results agree with the numerical spectra recently obtained for the 3- and the 4-anyon systems.

Fabrizio Illuminati

1992-07-29T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


221

New approaches to thermoelectric cooling effects in magnetic fields  

DOE Green Energy (OSTI)

The authors review thermoelectric effects in a magnetic field at a phenomenological level. Discussions of the limiting performance and problems with its computation for both Peltier and Ettingshausen coolers are presented. New principles are discussed to guide the materials scientist in the search for better Ettingshausen materials, and a brief review of the subtle measurement problems is presented.

Migliori, A.; Darling, T.W.; Freibert, F.; Trugman, S.A.; Moshopoulou, E. [Los Alamos National Lab., NM (United States); Sarrao, J.L. [Florida State Univ., Tallahassee, FL (United States)

1997-08-01T23:59:59.000Z

222

Influence of primordial magnetic fields on 21 cm emission  

E-Print Network (OSTI)

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...

Schleicher, Dominik R G; Klessen, Ralf S

2008-01-01T23:59:59.000Z

223

Energy Eigenvalues of Kemmer Equation for a Homogeneous Magnetic Field  

E-Print Network (OSTI)

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.

A. Havare; K. Sogut

2002-07-10T23:59:59.000Z

224

Spin flip probability of electron in a uniform magnetic field  

SciTech Connect

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.

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

225

A linear helicon plasma device with controllable magnetic field gradient  

Science Conference Proceedings (OSTI)

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.

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

226

Molecular Lines as Diagnostics of Solar and Stellar Magnetic Fields  

E-Print Network (OSTI)

Molecular Lines as Diagnostics of Solar and Stellar Magnetic Fields S.V. Berdyugina1, S.K. Solanki2 (Berdyugina et al. 2000; Berdyugina & Solanki 2001a). The synthetic Stokes profiles of various molecular and sunspot temperature. Introducing molecular lines into the inversion of sunspot spectra leads

Berdyugina, Svetlana

227

Triggering for Magnetic Field Measurements of the LCLS Undulators  

Science Conference Proceedings (OSTI)

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.

Hacker, Kirsten

2010-12-13T23:59:59.000Z

228

What is a flux tube? On the magnetic field topology of buoyant flux structures  

E-Print Network (OSTI)

What is a flux tube? On the magnetic field topology of buoyant flux structures Fausto Cattaneo study the topology of field lines threading buoyant magnetic flux struc- tures. The magnetic structures ­ Sun: interior ­ Sun: magnetic fields ­ Stars: spots 1 Current address: Department of Mathematics

229

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

SciTech Connect

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.

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

2010-04-13T23:59:59.000Z

230

Once-ionized helium in superstrong magnetic fields  

E-Print Network (OSTI)

It is generally believed that magnetic fields of some neutron stars, the so-called magnetars, are enormously strong, up to 10^{14} - 10^{15} G. Recent investigations have shown that the atmospheres of magnetars are possibly composed of helium. We calculate the structure and bound-bound radiative transitions of the He^+ ion in superstrong fields, including the effects caused by the coupling of the ion's internal degrees of freedom to its center-of-mass motion. We show that He^+ in superstrong magnetic fields can produce spectral lines with energies of up to about 3 keV, and it may be responsible for absorption features detected recently in the soft X-ray spectra of several radio-quiet isolated neutron stars. Quantization of the ion's motion across a magnetic field results in a fine structure of spectral lines, with a typical spacing of tens electron-volts in magnetar-scale fields. It also gives rise to ion cyclotron transitions, whose energies and oscillator strengths depend on the state of the bound ion.

George G. Pavlov; Victor G. Bezchastnov

2005-05-23T23:59:59.000Z

231

Apparatus for unilateral generation of a homogeneous magnetic field  

DOE Patents (OSTI)

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.

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

1984-05-01T23:59:59.000Z

232

Apparatus for unilateral generation of a homogeneous magnetic field  

DOE Patents (OSTI)

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.

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

1988-01-01T23:59:59.000Z

233

ROLE OF MAGNETIC FIELD STRENGTH AND NUMERICAL RESOLUTION IN SIMULATIONS OF THE HEAT-FLUX-DRIVEN BUOYANCY INSTABILITY  

SciTech Connect

The role played by magnetic fields in the intracluster medium (ICM) of galaxy clusters is complex. The weakly collisional nature of the ICM leads to thermal conduction that is channeled along field lines. This anisotropic heat conduction profoundly changes the instabilities of the ICM atmosphere, with convective stabilities being driven by temperature gradients of either sign. Here, we employ the Athena magnetohydrodynamic code to investigate the local non-linear behavior of the heat-flux-driven buoyancy instability (HBI) relevant in the cores of cooling-core clusters where the temperature increases with radius. We study a grid of two-dimensional simulations that span a large range of initial magnetic field strengths and numerical resolutions. For very weak initial fields, we recover the previously known result that the HBI wraps the field in the horizontal direction, thereby shutting off the heat flux. However, we find that simulations that begin with intermediate initial field strengths have a qualitatively different behavior, forming HBI-stable filaments that resist field-line wrapping and enable sustained vertical conductive heat flux at a level of 10%-25% of the Spitzer value. While astrophysical conclusions regarding the role of conduction in cooling cores require detailed global models, our local study proves that systems dominated by the HBI do not necessarily quench the conductive heat flux.

Avara, Mark J.; Reynolds, Christopher S. [Department of Astronomy, University of Maryland, College Park, MD 20740 (United States); Bogdanovic, Tamara, E-mail: mavara@astro.umd.edu, E-mail: chris@astro.umd.edu, E-mail: tamarab@gatech.edu [Center for Relativistic Astrophysics, School of Physics, Georgia Tech, Atlanta, GA 30332 (United States)

2013-08-20T23:59:59.000Z

234

Theory of magnetization transport in a spatially varying magnetic field derived from entropic considerations  

E-Print Network (OSTI)

A theory of magnetization transport of a single spin-species in a spatially varying magnetic field is derived from entropic considerations. The theory describes thermodynamic transport in the language of differential geometry. Both magnetization diffusion and separation are predicted from a sample geometry, a magnetic field geometry, an entropy density function, and a single space-time scale. It is expressed first and most generally as coupled nonlinear partial differential equations, which are valid for the regime of high dipole-energy and magnetization. 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 SMT parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is derived, and is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield. Differences among the three models are illustrated by numerical solution. A family of analytic, steady-state solutions to the nonlinear transport equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. A steady-state solution for the magnetization is shown to be equivalent to the widely applied separation equation of Fenske. Moreover, we show that the SMT parameter is functionally related to the relative volatility parameter of Fenske.

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

2013-10-28T23:59:59.000Z

235

Quasi-equilibrium electron density along a magnetic field line  

SciTech Connect

A methodology is developed to determine the density of high-energy electrons along a magnetic field line for a low-{beta} plasma. This method avoids the expense and statistical noise of traditional particle tracking techniques commonly used for high-energy electrons in bombardment plasma generators. By preserving the magnetic mirror and assuming a mixing timescale, typically the elastic collision frequency with neutrals, a quasi-equilibrium electron distribution can be calculated. Following the transient decay, the analysis shows that both the normalized density and the reduction fraction due to collision converge to a single quasi-equilibrium solution.

Mao, Hann-Shin; Wirz, Richard [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095 (United States)

2012-11-26T23:59:59.000Z

236

THE IMPACT OF THERMODYNAMICS ON GRAVITATIONAL COLLAPSE: FILAMENT FORMATION AND MAGNETIC FIELD AMPLIFICATION  

Science Conference Proceedings (OSTI)

Stars form by the gravitational collapse of interstellar gas. The thermodynamic response of the gas can be characterized by an effective equation of state. It determines how gas heats up or cools as it gets compressed, and hence plays a key role in regulating the process of stellar birth on virtually all scales, ranging from individual star clusters up to the galaxy as a whole. We present a systematic study of the impact of thermodynamics on gravitational collapse in the context of high-redshift star formation, but argue that our findings are also relevant for present-day star formation in molecular clouds. We consider a polytropic equation of state, P = k{rho}{sup {Gamma}}, with both sub-isothermal exponents {Gamma} 1. We find significant differences between these two cases. For {Gamma} > 1, pressure gradients slow down the contraction and lead to the formation of a virialized, turbulent core. Weak magnetic fields are strongly tangled and efficiently amplified via the small-scale turbulent dynamo on timescales corresponding to the eddy-turnover time at the viscous scale. For {Gamma} < 1, on the other hand, pressure support is not sufficient for the formation of such a core. Gravitational contraction proceeds much more rapidly and the flow develops very strong shocks, creating a network of intersecting sheets and extended filaments. The resulting magnetic field lines are very coherent and exhibit a considerable degree of order. Nevertheless, even under these conditions we still find exponential growth of the magnetic energy density in the kinematic regime.

Peters, Thomas; Klessen, Ralf S.; Federrath, Christoph; Smith, Rowan J. [Zentrum fuer Astronomie, Institut fuer Theoretische Astrophysik, Universitaet Heidelberg, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Schleicher, Dominik R. G. [Institut fuer Astrophysik, Georg-August-Universitaet, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany); Banerjee, Robi [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg (Germany); Sur, Sharanya, E-mail: tpeters@physik.uzh.ch [Raman Research Institute, C. V. Raman Avenue, Sadashivnagar, Bangalore 560080 (India)

2012-12-01T23:59:59.000Z

237

Particle acceleration by fluctuating electric fields at a magnetic field null point  

E-Print Network (OSTI)

Particle acceleration consequences from fluctuating electric fields superposed on an X-type magnetic field in collisionless solar plasma are studied. Such a system is chosen to mimic generic features of dynamic reconnection, or the reconnective dissipation of a linear disturbance. We explore numerically the consequences for charged particle distributions of fluctuating electric fields superposed on an X-type magnetic field. Particle distributions are obtained by numerically integrating individual charged particle orbits when a time varying electric field is superimposed on a static X-type neutral point. This configuration represents the effects of the passage of a generic MHD disturbance through such a system. Different frequencies of the electric field are used, representing different possible types of wave. The electric field reduces with increasing distance from the X-type neutral point as in linear dynamic magnetic reconnection. The resulting particle distributions have properties that depend on the amplitude and frequency of the electric field. In many cases a bimodal form is found. Depending on the timescale for variation of the electric field, electrons and ions may be accelerated to different degrees and often have energy distributions of different forms. Protons are accelerated to $\\gamma$-ray producing energies and electrons to and above hard X-ray producing energies in timescales of 1 second. The acceleration mechanism is possibly important for solar flares and solar noise storms but is also applicable to all collisionless plasmas.

P. Petkaki; A. L. MacKinnon

2007-07-09T23:59:59.000Z

238

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

DOE Patents (OSTI)

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.

Casada, D.A.; Haynes, H.D.

1993-08-17T23:59:59.000Z

239

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

SciTech Connect

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.

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

1993-01-01T23:59:59.000Z

240

Magnetism in the spiral galaxy NGC 6946: magnetic arms, depolarization rings, dynamo modes and helical fields  

E-Print Network (OSTI)

The spiral galaxy NGC 6946 was observed in total intensity and linear polarization in five radio bands between 3cm and 21cm. At the inner edge of the inner gas spiral arm the ordered magnetic field is only mildly compressed and turns smoothly, to become aligned along the gas arm. Hence the field is not shocked and is probably connected to the warm, diffuse gas. At larger radii, two bright magnetic arms between the optical arms are visible in polarized intensity. The field in the northern magnetic arm is almost totally aligned. Faraday rotation measures (RM) in these arms are consistent with the superposition of two low azimuthal dynamo modes. Three more magnetic arms are discovered in the outer galaxy, located between HI arms. Due to strong Faraday depolarization the galaxy is not transparent to polarized waves at 18cm and 20cm. The large-scale asymmetry in depolarization with respect to the major axis may be another indication of large-scale helical fields. Three depolarization rings of almost zero polarization seen at 20cm are probably generated by differential Faraday rotation in HII complexes in NGC 6946 of 300-500 pc size. - In the gas/optical spiral arms, the total (mostly turbulent) magnetic field is amplified to \\simeq 20\\muG. Its energy density is \\simeq 10 times larger than that of the ionized gas and is similar to that of the turbulent gas motions in the inner galaxy. The magnetic energy exceeds that of the turbulent energy in the outer galaxy.

Rainer Beck

2007-05-29T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

Voltage spike detection in high field superconducting accelerator magnets  

SciTech Connect

A measurement system for the detection of small magnetic flux changes in superconducting magnets, which are due to either mechanical motion of the conductor or flux jump, has been developed at Fermilab. These flux changes are detected as small amplitude, short duration voltage spikes, which are {approx}15mV in magnitude and lasts for {approx}30 {micro}sec. The detection system combines an analog circuit for the signal conditioning of two coil segments and a fast data acquisition system for digitizing the results, performing threshold detection, and storing the resultant data. The design of the spike detection system along with the modeling results and noise analysis will be presented. Data from tests of high field Nb{sub 3}Sn magnets at currents up to {approx}20KA will also be shown.

Orris, D.F.; Carcagno, R.; Feher, S.; Makulski, A.; Pischalnikov, Y.M.; /Fermilab

2004-12-01T23:59:59.000Z

242

Structure and Dynamics of the Sun's Open Magnetic Field  

E-Print Network (OSTI)

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.

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

2007-05-30T23:59:59.000Z

243

Transport of Magnetic Fields in Convective, Accreting Supernova Cores  

E-Print Network (OSTI)

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

Christopher Thompson; Norman Murray

2001-05-24T23:59:59.000Z

244

MAGNETIC EXPLOSIONS: ROLE OF THE INDUCTIVE ELECTRIC FIELD  

Science Conference Proceedings (OSTI)

Inclusion of the inductive electric field, E{sub ind}, due to the temporally changing B, in magnetic explosions is discussed, with emphasis on solar flares. Several roles played by E{sub ind} are identified: on a global scale, E{sub ind} produces the electromotive force that drives the explosion; the associated E{sub ind} Multiplication-Sign B drift is identified with the inflow of magnetic field lines into a reconnection region; the polarization current, associated with {partial_derivative}E{sub ind}/{partial_derivative}t, implies a J Multiplication-Sign B force that accelerates this inflow; and the component of E{sub ind} parallel to B accelerates the energetic electrons that cause hard X-ray emission and type III radio bursts. Some simple models that describe these effects are presented. A resolution of the long-standing 'number problem' in solar flares is suggested.

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

2012-04-10T23:59:59.000Z

245

Magnetic field adjustment structure and method for a tapered wiggler  

DOE Patents (OSTI)

An improved method and structure is disclosed for adjusting the magnetic field generated by a group of electromagnet poles spaced along the path of a charged particle beam to compensate for energy losses in the charged particles which comprises providing more than one winding on at least some of the electromagnet poles; connecting one respective winding on each of several consecutive adjacent electromagnet poles to a first power supply, and the other respective winding on the electromagnet pole to a different power supply in staggered order; and independently adjusting one power supply to independently vary the current in one winding on each electromagnet pole in a group whereby the magnetic field strength of each of a group of electromagnet poles may be changed in smaller increments.

Halbach, Klaus (Berkeley, CA)

1988-01-01T23:59:59.000Z

246

Magnetism of Semiconductor-Based Magnetic Tunnel Junctions under Electric Field from First Principles  

SciTech Connect

Semiconductor magnetic tunnel junctions (MTJs), composed of diluted magnetic semiconductors (DMSs) sandwiching a semiconductor barrier, have potential applications in spintronics but their development has been slow due to the difficulty of controlling the magnetism of DMSs. In terms of density functional calculations for model semiconductor MTJs, (Zn,Co)O/ZnO/(Zn,Co)O and (Ga,Mn)N/GaN/(Ga,Mn)N, we show that the magnetic coupling between the transition metal ions in each DMS electrode of such semiconductor MTJs can be switched from ferromagnetic to antiferromagnetic, or vice versa, under the application of external electric field across the junctions. Our results suggest a possible avenue for the application of semiconductor MTJs.

Kan, E.; Xiang, H.; Yang, J.; Whangbo, M. H.

2009-06-01T23:59:59.000Z

247

Magnetic-field induced screening effect and collective excitations  

SciTech Connect

We explicitly construct the fermion propagator in a magnetic field background B to take the lowest Landau-level approximation. We analyze the energy and momentum dependence in the polarization tensor and discuss the collective excitations. We find there appear two branches of collective modes in one of two transverse gauge particles; one represents a massive and attenuated gauge particle and the other behaves similar to the zero sound at finite density.

Fukushima, Kenji [Department of Physics, Keio University, Kanagawa 223-8522 (Japan)

2011-06-01T23:59:59.000Z

248

Circuitry, systems and methods for detecting magnetic fields  

SciTech Connect

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.

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

2010-09-14T23:59:59.000Z

249

Interior Permanent Magnet Reluctance Machine with Brushless Field Excitation  

SciTech Connect

In a conventional permanent magnet (PM) machine, the air-gap flux produced by the PM is fixed. It is difficult to enhance the air-gap flux density due to limitations of the PM in a series-magnetic circuit. However, the air-gap flux density can be weakened by using power electronic field weakening to the limit of demagnetization of the PMs. This paper presents the test results of controlling the PM air-gap flux density through the use of a stationary brushless excitation coil in a reluctance interior permanent magnet with brushless field excitation (RIPM-BFE) motor. Through the use of this technology the air-gap flux density can be either enhanced or weakened. There is no concern with demagnetizing the PMs during field weakening. The leakage flux of the excitation coil through the PMs is blocked. The prototype motor built on this principle confirms the concept of flux enhancement and weakening through the use of excitation coils.

Wiles, R.H.

2005-10-07T23:59:59.000Z

250

The energy space for the Gross-Pitaevskii equation with magnetic field  

E-Print Network (OSTI)

We study the energy space for the Gross-Pitaevskii equation with magnetic field and non-vanishing conditions at infinity. We provide necessary and sufficient conditions on the magnetic field for which the energy space is non-empty.

Kachmar, Ayman

2008-01-01T23:59:59.000Z

251

High temperature, magnetic field assisted (sub)THz quantum cascade laser  

E-Print Network (OSTI)

We demonstrate magnetic field assisted, (sub)THz quantum cascade laser operating above 200 K. This is achieved through the application of strong magnetic fields which provide an additional lateral confinement in order to ...

Wade, Aaron

252

ABRUPT LONGITUDINAL MAGNETIC FIELD CHANGES IN FLARING ACTIVE REGIONS  

Science Conference Proceedings (OSTI)

We characterize the changes in the longitudinal photospheric magnetic field during 38 X-class and 39 M-class flares within 65{sup 0} of disk center using 1 minute GONG magnetograms. In all 77 cases, we identify at least one site in the flaring active region where clear, permanent, stepwise field changes occurred. The median duration of the field changes was about 15 minutes and was approximately equal for X-class and for M-class flares. The absolute values of the field changes ranged from the detection limit of {approx}10 G to as high as {approx}450 G in two exceptional cases. The median value was 69 G. Field changes were significantly stronger for X-class than for M-class flares and for limb flares than for disk-center flares. Longitudinal field changes less than 100 G tended to decrease longitudinal field strengths, both close to disk center and close to the limb, while field changes greater than 100 G showed no such pattern. Likewise, longitudinal flux strengths tended to decrease during flares. Flux changes, particularly net flux changes near disk center, correlated better than local field changes with GOES peak X-ray flux. The strongest longitudinal field and flux changes occurred in flares observed close to the limb. We estimate the change of Lorentz force associated with each flare and find that this is large enough in some cases to power seismic waves. We find that longitudinal field decreases would likely outnumber increases at all parts of the solar disk within 65{sup 0} of disk center, as in our observations, if photospheric field tilts increase during flares as predicted by Hudson et al.

Petrie, G. J. D. [National Solar Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Sudol, J. J. [West Chester University, West Chester, PA 19383 (United States)

2010-12-01T23:59:59.000Z

253

Electric and Magnetic Field Exposure Levels (0 to 3000 Hz) near Residential Photovoltaic Energy Generation Facilities  

Science Conference Proceedings (OSTI)

Electric and magnetic field levels associated with two residential photovoltaic energy generation facilities were characterized in this study. This measurement evaluation included static (direct current [DC]) magnetic fields and power-frequency alternating current (AC) electric and magnetic fields (up to 3,000 Hz).The major source of DC and AC magnetic fields associated with a residential solar facility is the power inverter that converts DC to AC electricity. In close proximity to one ...

2012-11-01T23:59:59.000Z

254

New Magnetic-Field-Sensitive Alloy Could Find Use in Novel ...  

Science Conference Proceedings (OSTI)

... like quartz, to compress under an electric field. ... magnetostriction effect in magnetic fields as low as about ... Ichiro Takeuchi of UMd, are lower than, but ...

2012-10-18T23:59:59.000Z

255

From insulator to quantum Hall liquid at low magnetic fields  

E-Print Network (OSTI)

We have performed low-temperature transport measurements on a GaAs twodimensional electron system at low magnetic fields. Multiple temperatureindependent points and accompanying oscillations are observed in the longitudinal resistivity between the low-field insulator and the quantum Hall liquid. The amplitudes of these oscillations can be well described by conventional Shubnikov-de Haas theory, and our experimental results therefore support the existence of an intermediate metallic regime between the low-field insulator and quantum Hall liquid. 1 Two-dimensional (2D) phase transitions have attracted a great deal of interest recently [1–11]. To date, despite many existing experimental and theoretical studies on 2D phase transitions, there are still some interesting but unresolved issues. In particular, it is still under debate whether a direct transition from an insulator (I) to a high Landau level filling factor (? ? 3) quantum Hall (QH) state at low magnetic fields B is a genuine phase transition. Experimentally, a single approximately temperature (T)-independent point in

Tsai-yu Huanga; C. -t. Lianga; Gil-ho Kimb; C. F. Huangc; Chao-ping Huanga

2006-01-01T23:59:59.000Z

256

Ga-based passive loop optimization for magnetic field mitigation of transmission lines  

Science Conference Proceedings (OSTI)

This paper presents a systematic method to assist in the design of passive loops with the aim of mitigating the magnetic field generated by overhead transmission lines. The procedure is based on a two-dimensional (2D) modeling of the magnetic field, ... Keywords: Compensated loop, Genetic algorithm, Magnetic field, Mitigation, Passive loop, Reduction factor

Pedro Cruz; Jesús M. Riquelme; Antonio de la Villa; José L. Martínez

2007-10-01T23:59:59.000Z

257

Temperature compensated and self-calibrated current sensor using reference magnetic field  

DOE Patents (OSTI)

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.

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

2007-10-09T23:59:59.000Z

258

Kubo formulas for relativistic fluids in strong magnetic fields  

SciTech Connect

Magnetohydrodynamics of strongly magnetized relativistic fluids is derived in the ideal and dissipative cases, taking into account the breaking of spatial symmetries by a quantizing magnetic field. A complete set of transport coefficients, consistent with the Curie and Onsager principles, is derived for thermal conduction, as well as shear and bulk viscosities. It is shown that in the most general case the dissipative function contains five shear viscosities, two bulk viscosities, and three thermal conductivity coefficients. We use Zubarev's non-equilibrium statistical operator method to relate these transport coefficients to correlation functions of the equilibrium theory. The desired relations emerge at linear order in the expansion of the non-equilibrium statistical operator with respect to the gradients of relevant statistical parameters (temperature, chemical potential, and velocity.) The transport coefficients are cast in a form that can be conveniently computed using equilibrium (imaginary-time) infrared Green's functions defined with respect to the equilibrium statistical operator. - Highlights: > Strong magnetic fields can make charged fluids behave anisotropically. > Magnetohydrodynamics for these fluids contains 5 shear, 2 bulk viscosities, and 3 heat conductivities. > We derive Kubo formulas for these transport coefficients.

Huang Xuguang, E-mail: xhuang@th.physik.uni-frankfurt.de [Institute for Theoretical Physics, J. W. Goethe-Universitaet, D-60438 Frankfurt am Main (Germany); Sedrakian, Armen [Institute for Theoretical Physics, J. W. Goethe-Universitaet, D-60438 Frankfurt am Main (Germany); Rischke, Dirk H. [Institute for Theoretical Physics, J. W. Goethe-Universitaet, D-60438 Frankfurt am Main (Germany); Frankfurt Institute for Advanced Studies, D-60438 Frankfurt am Main (Germany)

2011-12-15T23:59:59.000Z

259

LONG-TERM TRENDS IN SUNSPOT MAGNETIC FIELDS  

SciTech Connect

Recent studies indicate that a maximum field strength in sunspots shows a gradual decrease over the last several years. By extrapolating this trend, Penn and Livingston proposed that sunspots may completely disappear in the not-so-distant future. To verify these recent findings, we employ historic synoptic data sets from seven observatories in the former USSR covering the period from 1957 to 2011 (from 1998 to 2011, observations were taken at only one observatory). Our results indicate that while sunspot field strengths rise and wane with solar cycle, there is not a long-term trend that would suggest a gradual decrease in sunspot magnetic fields over the four and a half solar cycles covered by these observations.

Pevtsov, Alexei A. [National Solar Observatory, Sunspot, NM 88349 (United States); Nagovitsyn, Yury A.; Rybak, Alexey L. [Pulkovo Astronomical Observatory, Russian Academy of Sciences, St. Petersburg 196140 (Russian Federation); Tlatov, Andrey G., E-mail: apevtsov@nso.edu, E-mail: nag@gao.spb.edu, E-mail: tlatov@mail.ru [Kislovodsk Solar Station of Pulkovo Observatory, Kislovodsk 357700 (Russian Federation)

2011-12-15T23:59:59.000Z

260

Assessment of biological effects associated with magnetic fields from a superconducting magnetic energy storage plant: Final report. [Contains glossary  

DOE Green Energy (OSTI)

This report provides a detailed evaluation of the potential biological effects of fringe magnetic fields associated with a superconducting magnetic energy storage (SMES) plant. The aspects of magnetic fields that are discussed include mechanisms of interaction of static and slowly time-varying magnetic fields with living systems; biological effects of magnetic fields on human and subhuman species, including the results of both laboratory studies and human epidemiological surveys; physical hazards posed by the interactions of magnetic fields with metallic implants, e.g., aneurysm clips and prostheses, and with medical electronic devices such as cardiac pacemakers; extant guidelines for occupational exposure to magnetic fields are summarized; recommendations for defining acceptable levels of exposure to SMES magnetic fields by occupational personnel and the population-at-large; and recommendations concerning several areas of research that would further our understanding of magnetic field interactions with living systems, and would provide additional elements of information required for the development of future exposure standards. 328 refs., 12 figs., 5 tabs.

Tenforde, T.S.

1986-04-01T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


261

Scale-Free Thin Discs with an Isopedic Magnetic Field  

E-Print Network (OSTI)

Global stationary configurations of both aligned and logarithmic spiral MHD perturbations are constructed analytically within an axisymmetric background ofrazor-thin scale-free gas disc, which is embedded in an axisymmetric gravitational potential of a dark matter halo and involves an isopedic magnetic field almost vertically threaded through the disc plane. The scale-free index $\\beta$ of the disc rotation speed $v_{\\theta}\\propto R^{-\\beta}$ falls in the rangeof $(-1/2 , 1/2)$ where $R$ is the cylindrical radius. With the holding-back of a deep background dark matter halo potential, the isopedic magnetic field may be strong enough to allow for the magnetic tension force overtaking the disc self-gravity, which can significantly influence global stationary MHD perturbation configurations and stability properties of the scale-free disc system. Only for stationary logarithmic spiral MHD perturbations with a perturbation scale-free index $\\beta_1=1/4$ or for aligned stationary MHD perturbations, can the MHD disc maintain a constant radial flux of angularmomentum. The variable radial flux of angular momentum in the radial direction corresponds to a complex dispersion relation. The marginal instabilities foraxisymmetric MHD disturbances are also examined for a special case as an example. When the magnetic tension force overtakes the disc self-gravity, the scale-free disc can be completely stable against axisymmetric MHD disturbances of all wavelengths. We predict the possible existence of an isopedicallymagnetized gas disc system in rotation primarily confined by a massive dark matter halo potential.

Yue Wu; Yu-Qing Lou

2006-07-16T23:59:59.000Z

262

New Methodology For Use in Rotating Field Nuclear Magnetic Resonance  

E-Print Network (OSTI)

MHz and the permanent magnet’s motor’s mechanical rotationa stepping motor held away from the magnet, a pulley system,permanent magnet mechanically is rotated with a motor while

Jachmann, Rebecca C.

2007-01-01T23:59:59.000Z

263

The effects of intense magnetic fields on Landau levels in a neutron star  

E-Print Network (OSTI)

In this paper, an approximate method of calculating the Fermi energy of electrons ($E_{F}(e)$) in a high-intensity magnetic field, based on the analysis of the distribution of a neutron star magnetic field, has been proposed. In the interior of a Neutron star, different forms of intense magnetic field could exist simultaneously and a high electron Fermi energy could be generated by the release of magnetic field energy. The calculation results show that: $E_{F}(e)$ is related to density $\\rho$, the mean electron number per baryon $Y_{e}$ and magnetic field strength $B$.

Gao, Z F; Song, D L; Yuan, J P; Chou, C K

2013-01-01T23:59:59.000Z

264

Quantum energy flow in atomic ions moving in magnetic fields  

E-Print Network (OSTI)

Using a combination of semiclassical and recently developed wave packet propagation techniques we find the quantum self-ionization process of highly excited ions moving in magnetic fields which has its origin in the energy transfer from the center of mass to the electronic motion. It obeys a time scale by orders of magnitude larger than the corresponding classical process. Importantly a quantum coherence phenomenon leading to the intermittent behaviour of the ionization signal is found and analyzed. Universal properties of the ionization process are established.

Vladimir Melezhik; Peter Schmelcher

2000-06-07T23:59:59.000Z

265

PHASE TRANSITION GENERATED COSMOLOGICAL MAGNETIC FIELD AT LARGE SCALES  

SciTech Connect

We constrain a primordial magnetic field (PMF) generated during a phase transition (PT) using the big bang nucleosynthesis bound on the relativistic energy density. The amplitude of the PMF at large scales is determined by the shape of the PMF spectrum outside its maximal correlation length scale. Even if the amplitude of the PMF at 1 Mpc is small, PT-generated PMFs can leave observable signatures in the potentially detectable relic gravitational wave background if a large enough fraction (1%-10%) of the thermal energy is converted into the PMF.

Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Ave., Pittsburgh, PA 15213 (United States); Tevzadze, Alexander G. [Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave., Tbilisi 0160 (Georgia); Ratra, Bharat, E-mail: tinatin@phys.ksu.edu, E-mail: aleko@tevza.org, E-mail: ratra@phys.ksu.edu [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, KS 66506 (United States)

2011-01-10T23:59:59.000Z

266

System having unmodulated flux locked loop for measuring magnetic fields  

DOE Patents (OSTI)

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.

Ganther, Jr., Kenneth R. (Olathe, KS); Snapp, Lowell D. (Blue Springs, MO)

2006-08-15T23:59:59.000Z

267

Low pressure arc discharge lamp apparatus with magnetic field generating means  

DOE Patents (OSTI)

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.

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

1987-10-06T23:59:59.000Z

268

GROWTH OF A LOCALIZED SEED MAGNETIC FIELD IN A TURBULENT MEDIUM  

Science Conference Proceedings (OSTI)

Turbulence dynamo deals with the amplification of a seed magnetic field in a turbulent medium and has been studied mostly for uniform or spatially homogeneous seed magnetic fields. However, some astrophysical processes (e.g., jets from active galaxies, galactic winds, or ram-pressure stripping in galaxy clusters) can provide localized seed magnetic fields. In this paper, we numerically study amplification of localized seed magnetic fields in a turbulent medium. Throughout the paper, we assume that the driving scale of turbulence is comparable to the size of the system. Our findings are as follows. First, turbulence can amplify a localized seed magnetic field very efficiently. The growth rate of magnetic energy density is as high as that for a uniform seed magnetic field. This result implies that magnetic field ejected from an astrophysical object can be a viable source of a magnetic field in a cluster. Second, the localized seed magnetic field disperses and fills the whole system very fast. If turbulence in a system (e.g., a galaxy cluster or a filament) is driven at large scales, we expect that it takes a few large-eddy turnover times for the magnetic field to fill the whole system. Third, growth and turbulence diffusion of a localized seed magnetic field are also fast in high magnetic Prandtl number turbulence. Fourth, even in decaying turbulence, a localized seed magnetic field can ultimately fill the whole system. Although the dispersal rate of the magnetic field is not fast in purely decaying turbulence, it can be enhanced by an additional forcing.

Cho, Jungyeon; Yoo, Hyunju, E-mail: jcho@cnu.ac.kr [Department of Astronomy and Space Science, Chungnam National University, Daejeon (Korea, Republic of)

2012-11-10T23:59:59.000Z

269

NEWTONIAN AND NON-NEWTONIAN MAGNETIC-FIELD RELAXATIONS IN SOLAR-CORONAL MHD  

SciTech Connect

This paper treats the relaxation of a magnetic field into a minimum-energy force-free state in a cold (pressure-less) viscous fluid, under the frozen-in condition of perfect electrical conductivity and letting the viscosity-dissipated energy be completely lost. A non-Newtonian fluid in popular use is studied in relation to the Newtonian viscous fluid, as two alternative numerical means to (1) construct force-free fields representing solar coronal structures in realistic geometry and (2) investigate the Parker theory of spontaneous formation of electric current sheets as a basic MHD process. Faraday's induction equation imposes an independent condition on the fluid velocity at rigid, perfectly conducting boundaries. This boundary condition is quite compatible with Newtonian mechanics but not with the non-Newtonian fluid model where velocity is equated to the Lorentz force with a free, positive multiplicative-factor. This defining property gives rise to unphysical or artificial singularities not previously known that are completely distinct from the physically admissible singularities representing the current sheets of the Parker theory. In particular, the non-Newtonian fluid takes a magnetic field with neutral points from any one of a continuum of initial states into an unphysical state instead of the proper force-free end-state accessible by Newtonian relaxation. The validity of previously published MHD results based on this non-Newtonian fluid, including some counterclaims against the Parker theory, is dubious. Investigating the Parker theory requires numerical relaxation models capable of anticipating and accurately describing inevitable current-sheet singularities. By including a weak resistivity to dissipate the inevitable current sheets as they form, the field can change topology intermittently to seek a terminal force-free state free of singularities. The minimum-energy state of this more complete model corresponds to the long-lived relaxed structures in the corona.

Low, B. C. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO (United States)

2013-05-01T23:59:59.000Z

270

Molten metal feed system controlled with a traveling magnetic field  

DOE Patents (OSTI)

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.

Praeg, Walter F. (Palos Park, IL)

1991-01-01T23:59:59.000Z

271

Molten metal feed system controlled with a traveling magnetic field  

DOE Patents (OSTI)

An apparatus for controlling the feed of molten metal in a continuous metal casting system comprising 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} {minus} 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 characteristic of the metal being cast. 8 figs.

Praeg, W.F.

1989-03-06T23:59:59.000Z

272

Stability of the toroidal magnetic field in stellar radiation zones  

E-Print Network (OSTI)

Understanding the stability of the magnetic field in radiation zones is of crucial importance for various processes in stellar interior like mixing, circulation and angular momentum transport. The stability properties of a star containing a prominent toroidal field in a radiation zone is investigated by means of a linear stability analysis in the Boussinesq approximation taking into account the effect of thermal conductivity. The growth rate of the instability is explicitly calculated and the effects of stable stratification and heat transport are discussed in detail. It is argued that the stabilizing influence of gravity can never entirely suppress the instability caused by electric currents in radiation zones although the stable stratification can significantly decrease the growth rate of instability

Bonanno, Alfio

2011-01-01T23:59:59.000Z

273

EXTRAPOLATION OF THE SOLAR CORONAL MAGNETIC FIELD FROM SDO/HMI MAGNETOGRAM BY A CESE-MHD-NLFFF CODE  

Science Conference Proceedings (OSTI)

Due to the absence of direct measurement, the magnetic field in the solar corona is usually extrapolated from the photosphere in a numerical way. At the moment, the nonlinear force-free field (NLFFF) model dominates the physical models for field extrapolation in the low corona. Recently, we have developed a new NLFFF model with MHD relaxation to reconstruct the coronal magnetic field. This method is based on CESE-MHD model with the conservation-element/solution-element (CESE) spacetime scheme. In this paper, we report the application of the CESE-MHD-NLFFF code to Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) data with magnetograms sampled for two active regions (ARs), NOAA AR 11158 and 11283, both of which were very non-potential, producing X-class flares and eruptions. The raw magnetograms are preprocessed to remove the force and then inputted into the extrapolation code. Qualitative comparison of the results with the SDO/AIA images shows that our code can reconstruct magnetic field lines resembling the EUV-observed coronal loops. Most important structures of the ARs are reproduced excellently, like the highly sheared field lines that suspend filaments in AR 11158 and twisted flux rope which corresponds to a sigmoid in AR 11283. Quantitative assessment of the results shows that the force-free constraint is fulfilled very well in the strong-field regions but apparently not that well in the weak-field regions because of data noise and numerical errors in the small currents.

Jiang Chaowei; Feng Xueshang, E-mail: cwjiang@spaceweather.ac.cn, E-mail: fengx@spaceweather.ac.cn [SIGMA Weather Group, State Key Laboratory for Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China)

2013-06-01T23:59:59.000Z

274

The Sun's Global Photospheric and Coronal Magnetic Fields: Observations and Models  

E-Print Network (OSTI)

In this review, our present day understanding of the Sun's global photospheric and coronal magnetic fields is discussed from both observational and theoretical viewpoints. Firstly, the large-scale properties of photospheric magnetic fields are described, along with recent advances in photospheric magnetic flux transport models. Following this, the wide variety of theoretical models used to simulate global coronal magnetic fields are described. From this, the combined application of both magnetic flux transport simulations and coronal modeling techniques to describe the phenomena of coronal holes, the Sun's open magnetic flux and the hemispheric pattern of solar filaments is discussed. Finally, recent advances in non-eruptive global MHD models are described. While the review focuses mainly on solar magnetic fields, recent advances in measuring and modeling stellar magnetic fields are described where appropriate. In the final section key areas of future research are identified.

Mackay, D H

2012-01-01T23:59:59.000Z

275

Chemical telemetry of OH observed to measure interstellar magnetic fields  

E-Print Network (OSTI)

We present models for the chemistry in gas moving towards the ionization front of an HII region. When it is far from the ionization front, the gas is highly depleted of elements more massive than helium. However, as it approaches the ionization front, ices are destroyed and species formed on the grain surfaces are injected into the gas phase. Photodissociation removes gas phase molecular species as the gas flows towards the ionization front. We identify models for which the OH column densities are comparable to those measured in observations undertaken to study the magnetic fields in star forming regions and give results for the column densities of other species that should be abundant if the observed OH arises through a combination of the liberation of H2O from surfaces and photodissociation. They include CH3OH, H2CO, and H2S. Observations of these other species may help establish the nature of the OH spatial distribution in the clouds, which is important for the interpretation of the magnetic field results.

S. Viti; T. W. Hartquist; P. C. Myers

2005-10-04T23:59:59.000Z

276

Circular Rydberg states of atomic hydrogen in an arbitrary magnetic field  

E-Print Network (OSTI)

We report a theoretical scheme using a B-spline basis set to improve the poor computational accuracy of circular Rydberg states of hydrogen atoms in the intermediate magnetic field. This scheme can produce high accuracy energy levels and valid for an arbitrary magnetic field. Energy levels of hydrogen are presented for circular Rydberg states with azimuthal quantum numbers $|m|$ = 10 - 70 as a function of magnetic field strengths ranging from zero to 2.35 $\\times$ 10$^9$ T. The variation of spatial distributions of electron probability densities with magnetic field strengths is discussed and competition between Coulomb and magnetic interactions is illustrated.

Zhao, L B; Du, M L

2011-01-01T23:59:59.000Z

277

FLARES IN THE CRAB NEBULA DRIVEN BY UNTWISTING MAGNETIC FIELDS  

Science Conference Proceedings (OSTI)

The recent discovery of PeV electrons from the Crab Nebula, produced on rapid timescales of one day or less with a sharply peaked gamma-ray spectrum without hard X-rays, challenges traditional models of diffusive shock acceleration followed by synchrotron radiation. Here, we outline an acceleration model involving a DC electric field parallel to the magnetic field in a twisted toroidal field around the pulsar. Sudden developments of resistivity in localized regions of the twisted field are thought to drive the particle acceleration, up to PeV energies, resulting in flares. This model can reproduce the observed timescales of T Almost-Equal-To 1 day, the peak photon energies of U{sub {Phi},rr} Almost-Equal-To 1 MeV, maximum electron energies of U{sub e,rr} Almost-Equal-To 1 PeV, and luminosities of L Almost-Equal-To 10{sup 36} erg s{sup -1}.

Sturrock, Peter [Center of Space Science and Astrophysics, Stanford University, Stanford, CA 94305 (United States); Aschwanden, Markus J., E-mail: sturrock@stanford.edu, E-mail: aschwanden@lmsal.com [Lockheed Martin Advanced Technology Center, Solar and Astrophysics Laboratory, Org. ADBS, Bldg. 252, 3251 Hanover St., Palo Alto, CA 94304 (United States)

2012-06-01T23:59:59.000Z

278

Phase-only shaped laser pulses in optimal control theory: Application to indirect photofragmentation dynamics in the weak-field limit  

SciTech Connect

We implement phase-only shaped laser pulses within quantum optimal control theory for laser-molecule interaction. This approach is applied to the indirect photofragmentation dynamics of NaI in the weak-field limit. It is shown that optimized phase-modulated pulses with a fixed frequency distribution can substantially modify transient dissociation probabilities as well as the momentum distribution associated with the relative motion of Na and I.

Shu, Chuan-Cun; Henriksen, Niels E. [Department of Chemistry, Building 207, Technical University of Denmark, DK-2800, Kongens Lyngby (Denmark)

2012-01-28T23:59:59.000Z

279

THE HYDROMAGNETIC INTERIOR OF A SOLAR QUIESCENT PROMINENCE. II. MAGNETIC DISCONTINUITIES AND CROSS-FIELD MASS TRANSPORT  

SciTech Connect

This second paper of the series investigates the transverse response of a magnetic field to the independent relaxation of its flux tubes of fluid seeking hydrostatic and energy balance, under the frozen-in condition and suppression of cross-field thermal conduction. The temperature, density, and pressure naturally develop discontinuities across the magnetic flux surfaces separating the tubes, requiring the finite pressure jumps to be compensated by magnetic-pressure jumps in cross-field force balance. The tangentially discontinuous fields are due to discrete currents in these surfaces, {delta}-function singularities in the current density that are fully admissible under the rigorous frozen-in condition but must dissipate resistively if the electrical conductivity is high but finite. The magnetic field and fluid must thus endlessly evolve by this spontaneous formation and resistive dissipation of discrete currents taking place intermittently in spacetime, even in a low-{beta} environment. This is a multi-dimensional effect in which the field plays a central role suppressed in the one-dimensional (1D) slab model of the first paper. The study begins with an order-of-magnitude demonstration that of the weak resistive and cross-field thermal diffusivities in the corona, the latter is significantly weaker for small {beta}. This case for spontaneous discrete currents, as an important example of the general theory of Parker, is illustrated with an analysis of singularity formation in three families of two-dimensional generalizations of the 1D slab model. The physical picture emerging completes the hypothesis formulated in Paper I that this intermittent process is the origin of the dynamic interiors of a class of quiescent prominences revealed by recent Hinode/SOT and SDO/AIA high-resolution observations.

Low, B. C.; Casini, R. [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); Liu, W.; Berger, T. [Lockheed-Martin Advanced Technology Center, Solar and Astrophysics Laboratory, 3251 Hanover Street, Palo Alto, CA 94304 (United States)

2012-09-20T23:59:59.000Z

280

Field Quality Analysis as a Tool to Monitor Magnet Production  

E-Print Network (OSTI)

magnetic) and partly of brass (non-magnetic). The magneticIII 'when a 25% iron-75% brass shim was installed in anFROM A 25% IRON AND 75% BRASS TUN1NG SHIM WHEN IT IS

Gupta, R.

2011-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

Primordial Magnetic Field Limits from CMB Trispectrum - Scalar Modes and Planck Constraints  

E-Print Network (OSTI)

Cosmic magnetic fields are observed to be coherent on large scales and could have a primordial origin. Non-Gaussian signals in the cosmic microwave background (CMB) are generated by primordial magnetic fields as the magnetic stresses and temperature anisotropy they induce depend quadratically on the magnetic field. We compute the CMB scalar trispectrum on large angular scales, for nearly scale-invariant magnetic fields, sourced via the Sachs-Wolfe effect. The trispectra induced by magnetic energy density and by magnetic scalar anisotropic stress are found to have typical magnitudes of approximately $10^{-29}$ and $10^{-19}$, respectively. The scalar anisotropic stress trispectrum is also calculated in the flat-sky approximation and yields a similar result. Observational limits on CMB non-Gaussianity from the Planck mission data allow us to set upper limits of $B_0 \\lesssim 0.6 $ nG on the present value of the primordial cosmic magnetic field. Considering the inflationary magnetic curvature mode in the trispectrum can further tighten the magnetic field upper limit to $B_0 \\lesssim 0.05 $ nG. These sub-nanoGauss constraints from the magnetic trispectrum are the most stringent limits so far on the strength of primordial magnetic fields, on megaparsec scales, significantly better than the limits obtained from the CMB bispectrum and the CMB power spectrum.

Pranjal Trivedi; Kandaswamy Subramanian; T. R. Seshadri

2013-12-18T23:59:59.000Z

282

Magnetic anisotropy in a permalloy microgrid fabricated by near-field optical lithography  

Science Conference Proceedings (OSTI)

We report the fabrication and magnetic properties of permalloy microgrids prepared by near-field optical lithography and characterized using high-sensitivity magneto-optical Kerr effect techniques. A fourfold magnetic anisotropy induced by the grid architecture is identified.

S. P. Li; A. Lebib; D. Peyrade; M. Natali; Y. Chen; W. S. Lew; J. A. C. Bland

2001-01-01T23:59:59.000Z

283

Holographic description of the Schwinger effect in electric and magnetic fields  

E-Print Network (OSTI)

We consider a generalization of the holographic Schwinger effect proposed by Semenoff and Zarembo to the case with constant electric and magnetic fields. There are two ways to turn on magnetic fields, i) the probe D3-brane picture and ii) the string world-sheet picture. In the former picture, magnetic fields both perpendicular and parallel to the electric field are activated by a Lorentz transformation and a spatial rotation. In the latter one, the classical solutions of the string world-sheet corresponding to circular Wilson loops are generalized to contain two additional parameters encoding the presence of magnetic fields.

Yoshiki Sato; Kentaroh Yoshida

2013-03-01T23:59:59.000Z

284

Method and means for measuring the anisotropy of a plasma in a magnetic field  

DOE Patents (OSTI)

Anisotropy is measured of a free-free-bremsstrahlungradiation-generating plasma in a magnetic field by collimating the free-free bremsstrahlung radiation in a direction normal to the magnetic field and scattering the collimated free- free bremsstrahlung radiation to resolve the radiation into its vector components in a plane parallel to the electric field of the bremsstrahlung radiation. The scattered vector components are counted at particular energy levels in a direction parallel to the magnetic field and also normal to the magnetic field of the plasma to provide a measure of anisotropy of the plasma. (Official Gazette)

Shohet, J.L.; Greene, D.G.S.

1973-10-23T23:59:59.000Z

285

A GENERAL THEORY OF CONNECTIVITY AND CURRENT SHEETS IN CORONAL MAGNETIC FIELDS ANCHORED TO DISCRETE SOURCES  

E-Print Network (OSTI)

A GENERAL THEORY OF CONNECTIVITY AND CURRENT SHEETS IN CORONAL MAGNETIC FIELDS ANCHORED TO DISCRETE on the flux of each domain. The resulting equilibria are current-free within each domain and contain singular currents along each of the field's separators. Subject headings: MHD -- Sun: corona -- Sun: magnetic fields

Klapper, Isaac

286

High energy neutrino absorption by W production in a strong magnetic field  

E-Print Network (OSTI)

An influence of a strong external magnetic field on the neutrino self-energy operator is investigated. The width of the neutrino decay into the electron and W boson, and the mean free path of an ultra-high energy neutrino in a strong magnetic field are calculated. A kind of energy cutoff for neutrinos propagating in a strong field is defined.

Kuznetsov, A V; Serghienko, A V

2010-01-01T23:59:59.000Z

287

High energy neutrino absorption by W production in a strong magnetic field  

E-Print Network (OSTI)

An influence of a strong external magnetic field on the neutrino self-energy operator is investigated. The width of the neutrino decay into the electron and W boson, and the mean free path of an ultra-high energy neutrino in a strong magnetic field are calculated. A kind of energy cutoff for neutrinos propagating in a strong field is defined.

A. V. Kuznetsov; N. V. Mikheev; A. V. Serghienko

2010-02-19T23:59:59.000Z

288

Solar magnetic fields and geomagnetic events. Alexei A. Pevtsov 1 and Richard C. Canfield  

E-Print Network (OSTI)

1 Solar magnetic fields and geomagnetic events. Alexei A. Pevtsov 1 and Richard C. Canfield AND GEOMAGNETIC EVENTS #12; 2 Abstract. Some interplanetary studies lead one to expect that the toroidal fields studies of solar magnetic fields and geomagnetic events that bear on these apparently conflicting views

Canfield, Richard

289

Magnetization of neutron star matter  

E-Print Network (OSTI)

The magnetization of neutron star matter in magnetic fields is studied by employing the FSUGold interaction. It is found that the magnetic susceptibilities of the charged particles (proton, electron and muon) can be larger than that of neutron. The effects of the anomalous magnetic moments (AMM) of each component on the magnetic susceptibility are examined in detail. It is found that the proton and electron AMM affect their respective magnetic susceptibility evidently in strong magnetic fields. In addition, they are the protons instead of the electrons that contribute most significantly to the magnetization of the neutron star matter in a relative weak magnetic field, and the induced magnetic field due to the magnetization can be appear to be very large. Finally, the effect of the density-dependent symmetry energy on the magnetization is discussed.

Dong, Jianmin; Gu, Jianzhong

2013-01-01T23:59:59.000Z

290

On the delayed gas breakdown in a ringing theta-pinch with bias magnetic field  

Science Conference Proceedings (OSTI)

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.

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

291

Leukemia/Lymphoma in Mice Exposed to 60-Hz Magnetic Fields: Preliminary Studies and Protocol  

Science Conference Proceedings (OSTI)

Possible health risks from magnetic field exposure establish the need for a high quality experimental database for assessing risk. This report describes preliminary studies of a mouse lymphatic leukemia cancer model used to develop a large-scale (2800-animal) lifetime 60-Hz magnetic field exposure study. This animal model is useful for evaluating whether magnetic fields act as either a complete carcinogen or as a cancer promoter or have no effect at all with respect to lymphatic cancer. A protocol for th...

1997-09-22T23:59:59.000Z

292

Evaluation of Smart Phone Apps Used to Measure AC Magnetic Fields  

Science Conference Proceedings (OSTI)

There are two specific objectives for this project. The first is to understand the characteristics of the magnetic field sensors used for measuring magnetic fields incorporated in smart phones as well as the integrated circuit in which the sensors are embedded. More specifically, since the design of both the sensor and the integrated circuit in which it is embedded affect the capability of the system to provide accurate magnetic field data, this design should be understood. The second is to learn as much ..

2013-05-01T23:59:59.000Z

293

Relativistic and Nonrelativistic Descriptions of Electron Energy Levels in a Static Magnetic Field  

E-Print Network (OSTI)

The physical consequences of the relativistic and nonrelativistic approaches to describe the energy levels of electrons which propagate in a static homogeneous magnetic field are considered. It is shown that for a given strength of the magnetic field, the quantized energy levels of the electrons calculated by nonrelativistic and relativistic equations differ substantially, up to few orders of magnitude for a magnetic field of about 1 Tesla. Experimental verification to resolve the discrepancy would be very welcome.

H. J. Schreiber; N. B. Skachkov

2008-03-28T23:59:59.000Z

294

Apparatus and method for generating a magnetic field by rotation of a charge holding object  

DOE Patents (OSTI)

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.

Gerald, II, Rex E. (Brookfield, IL); Vukovic, Lela (Westchester, IL); Rathke, Jerome W. (Homer Glenn, IL)

2009-10-13T23:59:59.000Z

295

Electric and Magnetic Field Exposure Levels (0 to 3 GHz) in Occupational Environments near Photovoltaic Energy Generation Facilities  

Science Conference Proceedings (OSTI)

Electric and magnetic field levels associated with photovoltaic energy generation facilities were measured and characterized in this study. This evaluation included the measurement of static (direct current [DC]) magnetic fields, power-frequency alternating current (AC) electric and magnetic fields (up to 3,000 Hz), and radio-frequency (RF) electric and magnetic fields (up to 3,000 MHz) at two electric utility solar generation facilities.The major sources of DC magnetic fields within a ...

2012-11-07T23:59:59.000Z

296

DENSITY AND MAGNETIC FIELD MEASUREMENTS IN THE TORMAC IV-c PLASMA  

E-Print Network (OSTI)

current waveforms 2.26 Ouput of subtraction circuit (flux exclusion) 2.27 Small probes 2.29 Vacuum magnetic field

Coonrod Jr., John Walter

2011-01-01T23:59:59.000Z

297

Generation of a Magnetic Field by Dynamo Action in a Turbulent Flow of Liquid Sodium  

SciTech Connect

We report the observation of dynamo action in the von Karman sodium experiment, i.e., the generation of a magnetic field by a strongly turbulent swirling flow of liquid sodium. Both mean and fluctuating parts of the field are studied. The dynamo threshold corresponds to a magnetic Reynolds number R{sub m}{approx}30. A mean magnetic field of the order of 40 G is observed 30% above threshold at the flow lateral boundary. The rms fluctuations are larger than the corresponding mean value for two of the components. The scaling of the mean square magnetic field is compared to a prediction previously made for high Reynolds number flows.

Monchaux, R.; Chiffaudel, A.; Daviaud, F.; Dubrulle, B.; Gasquet, C.; Marie, L.; Ravelet, F. [Service de Physique de l'Etat Condense, Direction des Sciences de la Matiere, CEA-Saclay, CNRS URA 2464, 91191 Gif-sur-Yvette cedex (France); Berhanu, M.; Fauve, S.; Mordant, N.; Petrelis, F. [Laboratoire de Physique Statistique de l'Ecole Normale Superieure, CNRS UMR 8550, 24 Rue Lhomond, 75231 Paris Cedex 05 (France); Bourgoin, M.; Moulin, M.; Odier, Ph.; Pinton, J.-F.; Volk, R. [Laboratoire de Physique de l'Ecole Normale Superieure de Lyon, CNRS UMR 5672, 46 allee d'Italie, 69364 Lyon Cedex 07 (France)

2007-01-26T23:59:59.000Z

298

A comparative model of two mechanisms from which a magnetic field arises in the heart  

Science Conference Proceedings (OSTI)

There are two different mechanisms from which a magnetic field can arise in the heart. The first mechanism has the source of the magnetic field as a current dipole oriented perpendicular to the action potential wave front with the “return” currents flowing in an adjacent volume conductor. The second mechanism is one with no adjacent volume conductor and has a magnetic field that arises due to the anisotropy of the tissue. We see that the two mechanisms produce magnetic fields of similar magnitudes and similar falloff rates as distance from the tissue increases

R. A. Murdick; B. J. Roth

2004-01-01T23:59:59.000Z

299

The Latent Heat of Single Flavor Color Superconductivity in a Magnetic Field  

E-Print Network (OSTI)

We calculate the energy release associated with first-order phase transition between different types of single flavor color superconductivity in a magnetic field.

Ping-ping Wu; Hang He; Defu Hou; Hai-cang Ren

2011-04-09T23:59:59.000Z

300

Correspondence between Electro-Magnetic Field and other Dark Energies in Non-linear Electrodynamics  

E-Print Network (OSTI)

In this work, we have considered the flat FRW model of the universe filled with electro-magnetic field. First, the Maxwell's electro-magnetic field in linear form has been discussed and after that the modified Lagrangian in non-linear form for accelerated universe has been considered. The corresponding energy density and pressure for non-linear electro-magnetic field have been calculated. We have found the condition such that the electro-magnetic field generates dark energy. The correspondence between the electro-magnetic field and the other dark energy candidates namely tachyonic field, DBI-essence, Chaplygin gas, hessence dark energy, k-essenece and dilaton dark energy have been investigated. We have also reconstructed the potential functions and the scalar fields in this scenario.

Maity, Sayani; Debnath, Ujjal

2011-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

Correspondence between Electro-Magnetic Field and other Dark Energies in Non-linear Electrodynamics  

E-Print Network (OSTI)

In this work, we have considered the flat FRW model of the universe filled with electro-magnetic field. First, the Maxwell's electro-magnetic field in linear form has been discussed and after that the modified Lagrangian in non-linear form for accelerated universe has been considered. The corresponding energy density and pressure for non-linear electro-magnetic field have been calculated. We have found the condition such that the electro-magnetic field generates dark energy. The correspondence between the electro-magnetic field and the other dark energy candidates namely tachyonic field, DBI-essence, Chaplygin gas, hessence dark energy, k-essenece and dilaton dark energy have been investigated. We have also reconstructed the potential functions and the scalar fields in this scenario.

Sayani Maity; Shuvendu Chakraborty; Ujjal Debnath

2011-04-12T23:59:59.000Z

302

Static magnetic fields: A summary of biological interactions, potential health effects, and exposure guidelines  

SciTech Connect

Interest in the mechanisms of interaction and the biological effects of static magnetic fields has increased significantly during the past two decades as a result of the growing number of applications of these fields in research, industry and medicine. A major stimulus for research on the bioeffects of static magnetic fields has been the effort to develop new technologies for energy production and storage that utilize intense magnetic fields (e.g., thermonuclear fusion reactors and superconducting magnet energy storage devices). Interest in the possible biological interactions and health effects of static magnetic fields has also been increased as a result of recent developments in magnetic levitation as a mode of public transportation. In addition, the rapid emergence of magnetic resonance imaging as a new clinical diagnostic procedure has, in recent years, provided a strong rationale for defining the possible biological effects of magnetic fields with high flux densities. In this review, the principal interaction mechanisms of static magnetic fields will be described, and a summary will be given of the present state of knowledge of the biological, environmental, and human health effects of these fields.

Tenforde, T.S.

1992-05-01T23:59:59.000Z

303

Repeatability of measurements of residential magnetic fields and wire codes  

SciTech Connect

Several epidemiological studies have been based on wire codes (i.e., categories of electrical wiring configurations near residences) or on in-home spot measurements of magnetic flux density (MFD) as surrogates for short- and long-term exposure of children and adults to residential magnetic fields. We used wire code and MFD measurements that were made in 81 Colorado homes in 1985 and again in 1990 to assess their repeatability over periods of 0-24 h and 5 years. These homes, a subset of those lived in by subjects from the case-control study of Savitz et al. [Am J Epidemiol 128:21-38, 1988], were divided into four approximately equally sized groups that were differentiated by wire code and by case-control status. Eight homes were assigned wire codes in 1990 that differed from the 1985 coding of Savitz and colleagues [1988]; of these, seven were coded as high-current configuration (HCC) and one as low-current configuration (LCC) in 1985. Overall, 37 homes were coded as HCC in 1990 compared with 38 homes in 1985. Coding differences were due to differing distance measurements (four homes), differing thick vs. thin categorization of primary-distribution line-conductor sizes (two homes), differing first-span vs. second-span categorization of secondary wires (one home), and physical changes in proximate electrical wiring (one home). Coefficients of correlation between MFD spot measurements that were separated in time by 0-24 h range between 0.70 and 0.90. The coefficient between spot measurements made in 1985 and then again in 1990 is 0.70. These coefficients are similar for HCC and LCC homes and do not depend on whether residential appliances were turned on or off. The data show (at least for the portion of Colorado studied) that residential wire code and, more surprisingly, spot MFD measurements, are fairly reliable over 0-24-h and 5-year periods.

Dovan, T.; Kaune, W.T.; Savitz, D.A. (ENERTECH Consultants, Campbell, CA (United States))

1993-01-01T23:59:59.000Z

304

The Sun's meridional circulation and interior magnetic field  

E-Print Network (OSTI)

of a magnetic ?eld in the sun’s radiative interior,” Nature,The sun’s meridional circulation and interior magnetic ?eldthe radiative interior of the sun under- goes nearly uniform

McCaslin, Jeremy; Garaud, Pascale; Wood, Toby

2010-01-01T23:59:59.000Z

305

Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma  

DOE Patents (OSTI)

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.

Woolley, R.D.

1996-12-31T23:59:59.000Z

306

Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma  

DOE Patents (OSTI)

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.

Woolley, Robert D. (Hillsborough, NJ)

1998-01-01T23:59:59.000Z

307

Diode magnetic-field influence on radiographic spot size  

Science Conference Proceedings (OSTI)

Flash radiography of hydrodynamic experiments driven by high explosives is a well-known diagnostic technique in use at many laboratories. The Dual-Axis Radiography for Hydrodynamic Testing (DARHT) facility at Los Alamos was developed for flash radiography of large hydrodynamic experiments. Two linear induction accelerators (LIAs) produce the bremsstrahlung radiographic source spots for orthogonal views of each experiment ('hydrotest'). The 2-kA, 20-MeV Axis-I LIA creates a single 60-ns radiography pulse. For time resolution of the hydrotest dynamics, the 1.7-kA, 16.5-MeV Axis-II LIA creates up to four radiography pulses by slicing them out of a longer pulse that has a 1.6-{micro}s flattop. Both axes now routinely produce radiographic source spot sizes having full-width at half-maximum (FWHM) less than 1 mm. To further improve on the radiographic resolution, one must consider the major factors influencing the spot size: (1) Beam convergence at the final focus; (2) Beam emittance; (3) Beam canonical angular momentum; (4) Beam-motion blur; and (5) Beam-target interactions. Beam emittance growth and motion in the accelerators have been addressed by careful tuning. Defocusing by beam-target interactions has been minimized through tuning of the final focus solenoid for optimum convergence and other means. Finally, the beam canonical angular momentum is minimized by using a 'shielded source' of electrons. An ideal shielded source creates the beam in a region where the axial magnetic field is zero, thus the canonical momentum zero, since the beam is born with no mechanical angular momentum. It then follows from Busch's conservation theorem that the canonical angular momentum is minimized at the target, at least in principal. In the DARHT accelerators, the axial magnetic field at the cathode is minmized by using a 'bucking coil' solenoid with reverse polarity to cancel out whatever solenoidal beam transport field exists there. This is imperfect in practice, because of radial variation of the total field across the cathode surface, solenoid misalignments, and long-term variability of solenoid fields for given currents. Therefore, it is useful to quantify the relative importance of canonical momentum in determining the focal spot, and to establish a systematic methodology for tuning the bucking coils for minimum spot size. That is the purpose of this article. Section II provides a theoretical foundation for understanding the relative importance of the canonical momentum. Section III describes the results of simulations used to quantify beam parameters, including the momentum, for each of the accelerators. Section IV compares the two accelerators, especially with respect to mis-tuned bucking coils. Finally, Section IV concludes with a methodology for optimizing the bucking coil settings.

Ekdahl, Carl A. Jr. [Los Alamos National Laboratory

2012-09-04T23:59:59.000Z

308

Stochastic Ion Heating in a Field-reversed Configuration Geometry by Rotating Magnetic Fields  

Science Conference Proceedings (OSTI)

Ion heating by application of rotating magnetic fields (RMF) to a prolate field-reversed configuration(FRC) is explored by analytical and numerical techniques. For odd-parity RMF (RMFo), perturbation analysis shows ions in figure-8 orbits gain energy at resonances of the RMFo frequency, ?R, with the figure-8 orbital frequency, ?. Since figure-8 orbits tend to gain the most energy from the RMF and are unlikely to escape in the cusp region (where most losses occur), they are optimal candidates for rapid stochastic heating, as compared to cyclotron and betatron orbits. Comparisons are made between heating caused by even- and odd-parity RMFs and between heating in currently operating and in reactor-scale FRC devices.

S.A. Cohen, A.S. Landsman, and A.H. Glasser

2007-06-25T23:59:59.000Z

309

Potential Magnetic Field around a Helical Flux-rope Current Structure in the Solar Corona  

E-Print Network (OSTI)

We consider the potential magnetic field associated with a helical electric line current flow, idealizing the near-potential coronal field within which a highly localized twisted current structure is embedded. It is found that this field has a significant axial component off the helical magnetic axis where there is no current flow, such that the flux winds around the axis. The helical line current field, in including the effects of flux rope writhe, is therefore more topologically complex than straight line and ring current fields sometimes used in solar flux rope models. The axial flux in magnetic fields around confined current structures may be affected by the writhe of these current structures such that the field twists preferentially with the same handedness as the writhe. This property of fields around confined current structures with writhe may be relevant to classes of coronal magnetic flux rope, including structures observed to have sigmoidal forms in soft X-rays and prominence magnetic fields. For example, ``bald patches'' and the associated heating by Parker current sheet dissipation seem likely. Thus some measurements of flux rope magnetic helicities may derive from external, near-potential fields. The predicted hemispheric preference for positive and negative magnetic helicities is consistent with observational results for prominences and sigmoids and past theoretical results for flux rope internal fields.

G. J. D. Petrie

2007-02-06T23:59:59.000Z

310

ON THE AMPLIFICATION OF MAGNETIC FIELD BY A SUPERNOVA BLAST SHOCK WAVE IN A TURBULENT MEDIUM  

SciTech Connect

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.

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

311

Impact of Magnetic Fields on the Corrosion Degradation of ...  

Science Conference Proceedings (OSTI)

Nanocomposite Alloy Design for High Frequency Power Conversion Applications · Novel La(Fe,Si)13-Based Composites for Magnetic Refrigeration.

312

COMPARISON OF FORCE-FREE CORONAL MAGNETIC FIELD MODELING USING VECTOR FIELDS FROM HINODE AND SOLAR DYNAMICS OBSERVATORY  

Science Conference Proceedings (OSTI)

Photospheric magnetic vector maps from two different instruments are used to model the nonlinear force-free coronal magnetic field above an active region. We use vector maps inferred from polarization measurements of the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (HMI) and the Solar Optical Telescope's Spectropolarimeter (SP) on board Hinode. Besides basing our model calculations on HMI data, we use both SP data of original resolution and scaled down to the resolution of HMI. This allows us to compare the model results based on data from different instruments and to investigate how a binning of high-resolution data affects the model outcome. The resulting three-dimensional magnetic fields are compared in terms of magnetic energy content and magnetic topology. We find stronger magnetic fields in the SP data, translating into a higher total magnetic energy of the SP models. The net Lorentz forces of the HMI and SP lower boundaries verify their force-free compatibility. We find substantial differences in the absolute estimates of the magnetic field energy but similar relative estimates, e.g., the fraction of excess energy and of the flux shared by distinct areas. The location and extension of neighboring connectivity domains differ and the SP model fields tend to be higher and more vertical. Hence, conclusions about the magnetic connectivity based on force-free field models are to be drawn with caution. We find that the deviations of the model solution when based on the lower-resolution SP data are small compared to the differences of the solutions based on data from different instruments.

Thalmann, J. K.; Tiwari, S. K.; Wiegelmann, T., E-mail: thalmann@mps.mpg.de [Max-Plank-Institut fuer Sonnensystemforschung, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany)

2013-05-20T23:59:59.000Z

313

Nanoscale magnetic field mapping with a single spin scanning probe magnetometer  

SciTech Connect

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.

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

314

Passive Superconducting Flux Conservers for Rotating-Magnetic-Field-Driven Field-Reversed Configurations  

SciTech Connect

The Princeton Field-Reversed Configuration (PFRC) experiment employs an odd-parity rotating magnetic field (RMFo) current drive and plasma heating system to form and sustain high-? plasmas. For radial confinement, an array of coaxial, internal, passive, flux-conserving (FC) rings applies magnetic pressure to the plasma while still allowing radio-frequency RMFo from external coils to reach the plasma. The 3 ms pulse duration of the present experiment is limited by the skin time (?fc) of its room-temperature copper FC rings. To explore plasma phenomena with longer characteristic times, the pulse duration of the next-generation PFRC-2 device will exceed 100 ms, necessitating FC rings with (?fc > 300 ms. In this paper we review the physics of internal, discrete, passive FCs and describe the evolution of the PFRC's FC array. We then detail new experiments that have produced higher performance FC rings that contain embedded high-temperature superconducting (HTS) tapes. Several HTS tape winding configurations have been studied and a wide range of extended skin times, from 0.4 s to over 103 s, has been achieved. The new FC rings must carry up to 3 kA of current to balance the expected PFRC-2 plasma pressure, so the dependence of the HTS-FC critical current on the winding configuration and temperature was also studied. From these experiments, the key HTS-FC design considerations have been identified and HTS-FC rings with the desired performance characteristics have been produced.

E. Oz, C.E. Myers, M.R. Edwards, B. Berlinger, A. Brooks, and S.A. Cohen

2011-01-05T23:59:59.000Z

315

Nature of Planetary Matter and Magnetic Field Generation in the Solar System  

E-Print Network (OSTI)

Understanding the nature of the matter comprising the Solar System is crucial for understanding the mechanism that generates the Earth's geomagnetic field and the magnetic fields of other planets and satellites. The commonality in the Solar System of matter like that of the inside of the Earth, together with common nuclear reactor operating conditions,forms the basis for generalizing the author's concept of nuclear geomagnetic field generation to planetary magnetic field generation by natural planetocentric nuclear fission reactors.

J. Marvin Herndon

2009-03-26T23:59:59.000Z

316

Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields  

DOE Patents (OSTI)

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.

Epstein, Arthur J. (Columbus, OH); Morin, Brian G. (Columbus, OH)

1998-01-01T23:59:59.000Z

317

Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields  

DOE Patents (OSTI)

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.

Epstein, A.J.; Morin, B.G.

1998-10-13T23:59:59.000Z

318

Photo of the Week: Controlling Chaos with Magnetic Fields | Department of  

Energy.gov (U.S. Department of Energy (DOE)) Indexed Site

Controlling Chaos with Magnetic Fields Controlling Chaos with Magnetic Fields Photo of the Week: Controlling Chaos with Magnetic Fields January 18, 2013 - 11:26am Addthis This artistic rendition of "spin vortices" illustrates tiny magnetic vortices that spin according to the polarization of each disk's vortex core. At Argonne National Laboratory, scientists are using alternating magnetic fields to control the behavior of these spin vortices, which are small dots made of iron and nickel. The experiments will help to create new, more efficient magnetic devices -- like the random access memory (RAM) in the device you are using to look at this very photo. Learn more about spin vortices. | Photo courtesy of Sander Munster, Dresden University of Technology.

319

Formation of sheet plumes, current coils, and helical magnetic fields in a spherical magnetohydrodynamic dynamo  

Science Conference Proceedings (OSTI)

Aiming at understanding of magnetic field generation process in rapidly rotating stars and planets represented by the Earth, computer simulations of magnetohydrodynamic (MHD) dynamo were performed in a rotating spherical shell geometry. Thermal convection and dynamo process with Ekman number of the order of 10{sup -7} were studied. New structures of convection motion, dynamo-generated electrical current, and magnetic field are found. The flow is organized as a set of thin, sheet-like plumes. The current is made of small-scale coil structure with magnetic flux tubes within each of the coil. These flux tubes are connected each other to form a large scale helical magnetic field structure.

Miyagoshi, Takehiro [Japan Agency for Marine-Earth Science and Technology, Yokohama 236-0001 (Japan); Kageyama, Akira [Graduate School of System Informatics, Kobe University, Kobe 657-8501 (Japan); Sato, Tetsuya [Graduate School of Simulation Studies, University of Hyogo, Kobe 650-0047 (Japan)

2011-07-15T23:59:59.000Z

320

Quark-meson coupling model for antikaon condensation in neutron star matter with strong magnetic fields  

E-Print Network (OSTI)

We study the effects of strong magnetic fields on antikaon condensation in neutron star matter using the quark-meson coupling (QMC) model. The QMC model describes a nuclear many-body system as nonoverlapping MIT bags in which quarks interact through the self-consistent exchange of scalar and vector mesons in the mean-field approximation. It is found that the presence of strong magnetic fields alters the threshold density of antikaon condensation significantly. The onset of $K^-$ condensation stronger depends on the magnetic field strength, and it even shifts beyond the threshold of $\\bar K^0$ condensation for sufficiently strong magnetic fields. In the presence of strong magnetic fields, the equation of state (EOS) becomes stiffer in comparison with the field-free case. The softening of the EOS by antikaon condensation also depends on the magnetic field strength, and it becomes less pronounced with increasing magnetic field strength. The results of the QMC model are compared with those obtained in a relativistic mean-field (RMF) model, and we find there are quantitative differences between the results of the QMC and RMF models.

P. Yue; H. Shen

2008-04-18T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
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to obtain the most current and comprehensive results.


321

NHMFL Breaks the 100 Tesla Barrier Gregory S. Boebinger, National High Magnetic Field Laboratory  

E-Print Network (OSTI)

NHMFL Breaks the 100 Tesla Barrier Gregory S. Boebinger, National High Magnetic Field Laboratory. 109no. 31 12404-12407 On March 22nd 2012, the NHMFL ­ Pulsed Field Facility broke the 100T tesla barrier, setting a world record of 100.75 tesla for a non-destructive magnet. By using advanced

Weston, Ken

322

Exposure to Residential Electric and Magnetic Fields and Risk of Childhood Leukemia  

Science Conference Proceedings (OSTI)

This project explored the possible association between electric and magnetic fields (EMF), wire codes, and childhood leukemia. In general, the project confirmed an association between wire codes and childhood leukemia but failed to identify magnetic fields as the explanation for the observed pattern of results.

1995-09-07T23:59:59.000Z

323

Neutrino self-energy and dispersion in a medium with magnetic field  

E-Print Network (OSTI)

We calculate the one-loop thermal self-energy of a neutrino in a constant and homogeneous magnetic field to all orders in the magnetic field strength using Schwinger's proper time method. We obtain the dispersion relation under various conditions.

A. Erdas; C. W. Kim; T. H. Lee

1998-04-17T23:59:59.000Z

324

Asymptotics of the ground state energy of heavy molecules in self-generated magnetic field  

E-Print Network (OSTI)

We consider asymptotics of the ground state energy of heavy atoms and molecules in the self-generatedl magnetic field and derive it including Scott, and in some cases even Schwinger and Dirac corrections (if magnetic field is not too strong). We also consider related topics: an excessive negative charge, ionization energy and excessive positive charge when atoms can still bind into molecules.

Victor Ivrii

2013-03-19T23:59:59.000Z

325

Original articles: Vortex states in axially symmetric superconductors in applied magnetic field  

Science Conference Proceedings (OSTI)

We solve analytically the linearized Ginzburg-Landau (GL) equation in the presence of an uniform magnetic field with cylindrical boundary conditions. The solution of the non-linear GL equation is provided as an expansion in the basis of linearized solutions. ... Keywords: Axial magnetic field, Mesoscopic superconductivity, Nonlinear Ginzburg-Landau equation, Vortex

Andrei Ludu; Milorad V. Miloševi?; Francois M. Peeters

2012-03-01T23:59:59.000Z

326

Particle acceleration by electrostatic waves traveling perpendicular to nonuniform magnetic fields  

SciTech Connect

A novel method has been proposed for indefinite nonstochastic acceleration of particles by electrostatic waves propagating normal to a magnetic field. Use is made of a magnetic field inhomogeneity to prevent the particle from detrapping from the electrostatic wave. Numerical plots of particle trajectories are presented.

Rath, S.; Kaw, P.K.

1988-05-01T23:59:59.000Z

327

The Magnificent Seven: Magnetic fields and surface temperature distributions  

E-Print Network (OSTI)

Presently seven nearby radio-quiet isolated neutron stars discovered in ROSAT data and characterized by thermal X-ray spectra are known. They exhibit very similar properties and despite intensive searches their number remained constant since 2001 which led to their name ``The Magnificent Seven''. Five of the stars exhibit pulsations in their X-ray flux with periods in the range of 3.4 s to 11.4 s. XMM-Newton observations revealed broad absorption lines in the X-ray spectra which are interpreted as cyclotron resonance absorption lines by protons or heavy ions and / or atomic transitions shifted to X-ray energies by strong magnetic fields of the order of 10^13 G. New XMM-Newton observations indicate more complex X-ray spectra with multiple absorption lines. Pulse-phase spectroscopy of the best studied pulsars RX J0720.4-3125 and RBS 1223 reveals variations in derived emission temperature and absorption line depth with pulse phase. Moreover, RX J0720.4-3125 shows long-term spectral changes which are interpreted as due to free precession of the neutron star. Modeling of the pulse profiles of RX J0720.4-3125 and RBS 1223 provides information about the surface temperature distribution of the neutron stars indicating hot polar caps which have different temperatures, different sizes and are probably not located in antipodal positions.

F. Haberl

2006-09-04T23:59:59.000Z

328

Spin relaxation and linear-in-electric-field frequency shift in an arbitrary, time-independent magnetic field  

Science Conference Proceedings (OSTI)

A method is presented to calculate the spin relaxation times T{sub 1}, T{sub 2} due to a nonuniform magnetic field, and the linear-in-electric-field precession frequency shift {delta}{omega}{sub E} when an electric field is present, in the diffusion approximation for spins confined to a rectangular cell. It is found that the rectangular cell geometry admits of a general result for T{sub 1}, T{sub 2}, and {delta}{omega}{sub E} in terms of the spatial cosine-transform components of the magnetic field.

Clayton, Steven Michael [Los Alamos National Laboratory

2010-12-03T23:59:59.000Z

329

One Dimensional Magnetized TG Gas Properties in an External Magnetic Field  

E-Print Network (OSTI)

With Girardeau's Fermi-Bose mapping, we have constructed the eigenstates of a TG gas in an external magnetic field. When the number of bosons $N$ is commensurate with the number of potential cycles $M$, the probability of this TG gas in the ground state is bigger than the TG gas raised by Girardeau in 1960. Through the comparison of properties between this TG gas and Fermi gas, we find that the following issues are always of the same: their average value of particle's coordinate and potential energy, system's total momentum, single-particle density and the pair distribution function. But the reduced single-particle matrices and their momentum distributions between them are different.

Zhao Liang Wang; An Min Wang

2009-12-31T23:59:59.000Z

330

Thermodynamic properties of strongly coupled plasma in presence of external magnetic field  

E-Print Network (OSTI)

Thermodynamic properties of a Yukawa system consisting of dust particles in plasma are studied in presence of an external magnetic field. It is assumed that dust particles interact with each other by modified potential in presence of magnetic field. Accordingly, a modified expression for internal energy has been obtained. A molecular dynamics code is developed to calculate this internal energy for the entire system. Based on the values of internal energy given by the code Helmholtz free energy and pressure are calculated for the system. Our study shows novel kind of behaviour for internal energy in presence of magnetic field. Thermodynamic properties are affected significantly by magnetic field. The study helps to express internal energy as a function of Coulomb coupling parameter and magnetic field.

Begum, Mahmuda; Das, Nilakshi

2013-01-01T23:59:59.000Z

331

Effect of trapping in a degenerate plasma in the presence of a quantizing magnetic field  

SciTech Connect

Effect of trapping as a microscopic phenomenon in a degenerate plasma is investigated in the presence of a quantizing magnetic field. The plasma comprises degenerate electrons and non-degenerate ions. The presence of the quantizing magnetic field is discussed briefly and the effect of trapping is investigated by using the Fermi-Dirac distribution function. The linear dispersion relation for ion acoustic wave is derived in the presence of the quantizing magnetic field and its influence on the propagation characteristics of the linear ion acoustic wave is discussed. Subsequently, fully nonlinear equations for ion acoustic waves are used to obtain the Sagdeev potential and the investigation of solitary structures. The formation of solitary structures is studied both for fully and partially degenerate plasmas in the presence of a quantizing magnetic field. Both compressive and rarefactive solitons are obtained for different conditions of temperature and magnetic field.

Shah, H. A.; Iqbal, M. J.; Qureshi, M. N. S. [Department of Physics, GC University, Lahore 54000 (Pakistan); Tsintsadze, N. [Department of Physics, GC University, Lahore 54000 (Pakistan); Institute of Physics, Tbilisi 0177 (Georgia); Masood, W. [Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)

2012-09-15T23:59:59.000Z

332

The effects of pseudo magnetic fields in molecular spectra and scattering  

SciTech Connect

Pseudo magnetic fields appear in the Born-Oppenheimer method for molecules when conical intersections or electronic angular momenta are taken into account. These fields are not real magnetic fields but they have the same mathematical properties and can lead to real observable effects in the dynamics of molecules. A general vector potential (gauge theory) approach for including these field effects in the Born-Oppenheimer method is introduced and applied to H + O{sub 2} scattering and the vibrational spectrum of Na{sub 3}(X) for zero total angular momentum (J = 0). The scattering results for HO{sub 2} show significant shifts in the resonance energies and lifetimes due to a magnetic solenoid type field originating from the C{sub 2v} conical intersection in HO{sub 2}. Significant changes in the state-to-state transition probabilities are also observed. The non-degenerate A{sub 1} and A{sub 2} vibrational spectra of Na{sub 3}(X) show significant shifts in the energy levels due to a magnetic solenoid type field originating from the D{sub 3h} conical intersection in Na{sub 3}. These two examples show that the effects of pseudo magnetic fields can be significant and in many cases they must be included in order to obtain agreement between theory and experiment. The newly developed gauge theory techniques for treating pseudo magnetic fields are also relevant for including the effects of real magnetic fields.

Kendrick, B. [Los Alamos National Lab., NM (United States). Theoretical Div.

1996-12-31T23:59:59.000Z

333

The strong magnetic field of the large-amplitude beta Cephei pulsator V1449 Aql  

E-Print Network (OSTI)

Only for very few beta Cephei stars has the behaviour of the magnetic field been studied over the rotation cycle. During the past two years we have obtained multi-epoch polarimetric spectra of the beta Cephei star V1449 Aql with SOFIN at the Nordic Optical Telescope to search for a rotation period and to constrain the geometry of the magnetic field. The mean longitudinal magnetic field is measured at 13 different epochs. The new measurements, together with the previous FORS1 measurements, have been used for the frequency analysis and the characterization of the magnetic field. V1449 Aql so far possesses the strongest longitudinal magnetic field of up to 700G among the beta Cephei stars. The resulting periodogram displays three dominant peaks with the highest peak at f=0.0720d^-1 corresponding to a period P=13.893d. The magnetic field geometry can likely be described by a centred dipole with a polar magnetic field strength B_d around 3kG and an inclination angle beta of the magnetic axis to the rotation axis o...

Hubrig, S; Briquet, M; Schoeller, M; Gonzalez, J F; Nunez, N; De Cat, P; Morel, T

2011-01-01T23:59:59.000Z

334

Ground Magnetics At San Francisco Volcanic Field Area (Warpinski...  

Open Energy Info (EERE)

the target area, obtained rock samples for age dating and mineral chemistry, performed gravity and magnetic surveys, and integrated these results to identify potential drilling...

335

Aligned Microstructure by Applying a High Magnetic Field to ...  

Science Conference Proceedings (OSTI)

Numerical Modeling of Centrifugally Cast HSS Rolls · Numerical Simulation of Electro-magnetic Turbulent Inhibitor Technology in a Tundish · Optimizing the ...

336

Dark energy, integrated Sachs-Wolfe effect and large-scale magnetic fields  

E-Print Network (OSTI)

The impact of large-scale magnetic fields on the interplay between the ordinary and integrated Sachs-Wolfe effects is investigated in the presence of a fluctuating dark energy component. The modified initial conditions of the Einstein-Boltzmann hierarchy allow for the simultaneous inclusion of dark energy perturbations and of large-scale magnetic fields. The temperature and polarization angular power spectra are compared with the results obtained in the magnetized version of the (minimal) concordance model. Purported compensation effects arising at large scales are specifically investigated. The fluctuating dark energy component modifies, in a computable manner, the shapes of the 1- and 2-$\\sigma$ contours in the parameter space of the magnetized background. The allowed spectral indices and magnetic field intensities turn out to be slightly larger than those determined in the framework of the magnetized concordance model where the dark energy fluctuations are absent.

Massimo Giovannini

2009-07-18T23:59:59.000Z

337

Finite temperature Casimir effect for charged massless scalars in a magnetic field  

E-Print Network (OSTI)

The zeta function regularization technique is used to study the finite temperature Casimir effect for a charged and massless scalar field confined between parallel plates and satisfying Dirichlet boundary conditions at the plates. A magnetic field perpendicular to the plates is included. Three equivalent expressions for the zeta function are obtained, which are exact to all orders in the magnetic field strength, temperature and plate distance. These expressions of the zeta function are used to calculate the Helmholtz free energy of the scalar field and the pressure on the plates, in the case of high temperature, small plate distance and strong magnetic field. In all cases, simple analytic expressions are obtained for the free energy and pressure which are accurate and valid for practically all values of temperature, plate distance and magnetic field.

Andrea Erdas; Kevin P. Seltzer

2013-04-23T23:59:59.000Z

338

Mechanism for magnetic field generation and growth in Rayleigh-Taylor unstable inertial confinement fusion plasmas  

Science Conference Proceedings (OSTI)

Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion (ICF) implosions are expected to generate magnetic fields at the gas-ice interface and at the ice-ablator interface. The focus here is on the gas-ice interface where the temperature gradient is the largest. A Hall-MHD model is used to study the magnetic field generation and growth for 2-D single-mode and multimode RTI in a stratified two-fluid plasma, the two fluids being ions and electrons. Self-generated magnetic fields are observed and these fields grow as the RTI progresses via the {nabla}n{sub e} Multiplication-Sign {nabla}T{sub e} term in the generalized Ohm's law. Srinivasan et al.[Phys. Rev. Lett. 108, 165002 (2012)] present results of the magnetic field generation and growth, and some scaling studies in 2-dimensions. The results presented here study the mechanism behind the magnetic field generation and growth, which is related to fluid vorticity generation by RTI. The magnetic field wraps around the bubbles and spikes and concentrates in flux bundles at the perturbed gas-ice interface where fluid vorticity is large. Additionally, the results of Srinivasan et al.[Phys. Rev. Lett. 108, 165002 (2012)] are described in greater detail. Additional scaling studies are performed to determine the growth of the self-generated magnetic field as a function of density, acceleration, perturbation wavelength, Atwood number, and ion mass.

Srinivasan, Bhuvana; Tang Xianzhu [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States)

2012-08-15T23:59:59.000Z

339

The Energy Level Shifts, Wave Functions and the Probability Current Distributions for the Bound Scalar and Spinor Particles Moving in a Uniform Magnetic Field  

E-Print Network (OSTI)

We discuss the equations for the bound one-active electron states based on the analytic solutions of the Schrodinger and Pauli equations for a uniform magnetic field and a single attractive $\\delta({\\bf r})$-potential. It is vary important that ground electron states in the magnetic field differ essentially from the analogous state of spin-0 particles, whose binding energy was intensively studied more than forty years ago. We show that binding energy equations for spin-1/2 particles can be obtained without using the language of boundary conditions in the $\\delta$-potential model developed in pioneering works. We use the obtained equations to calculate the energy level displacements analytically and demonstrate nonlinear dependencies on field intensity. We show that the magnetic field indeed plays a stabilizing role in considered systems in a case of the weak intensity, but the opposite occurs in the case of strong intensity. These properties may be important for real quantum mechanical fermionic systems in two and three dimensions. We also analyze the exact solution of the Pauli equation for an electron moving in the potential field determined by the three-dimensional $\\delta$-well in the presence of a strong magnetic field. We obtain asymptotic expressions for this solution for different values of the problem parameters. In addition, we consider electron probability currents and their dependence on the magnetic field. We show that including the spin in the framework of the nonrelativistic approach allows correctly taking the effect of the magnetic field on the electric current into account. The obtained dependencies of the current distribution, which is an experimentally observable quantity, can be manifested directly in scattering processes, for example.

V. N. Rodionov; G. A. Kravtsova

2011-02-19T23:59:59.000Z

340

Neutral Beam Injection for Plasma and Magnetic FieldDiagnostics  

DOE Green Energy (OSTI)

At the Lawrence Berkeley National Laboratory (LBNL) adiagnostic neutral beam injection system for measuring plasma parameters,flow velocity, and local magnetic field is being developed. High protonfraction and small divergence is essential for diagnostic neutral beams.In our design, a neutral hydrogen beam with an 8 cm x 11 cm (or smaller)elliptical beam spot at 2.5 m from the end of the extraction column isproduced. The beam will deliver up to 5 A of hydrogen beam to the targetwith a pulse width of ~;1 s, once every 1 - 2 min. The H1+ ion species ofthe hydrogen beamwill be over 90 percent. For this application, we havecompared two types of RF driven multicusp ion sources operating at 13.56MHz. The first one is an ion source with an external spiral antennabehind a dielectric RF-window. The second one uses an internal antenna insimilar ion source geometry. The source needs to generate uniform plasmaover a large (8 cm x 5 cm) extraction area. We expect that the ion sourcewith internal antenna will be more efficient at producing the desiredplasma density but might have the issue of limited antenna lifetime,depending on the duty factor. For both approaches there is a need forextra shielding to protect the dielectric materials from the backstreaming electrons. The source walls will be made of insulator materialsuch as quartz that has been observed to generate plasma with higheratomic fraction than sources with metal walls. The ion beam will beextracted and accelerated by a set of grids with slits, thus forming anarray of 6 sheet-shaped beamlets. The multiple grid extraction will beoptimized using computer simulation programs. Neutralization of the beamwill be done in neutralization chamber, which has over 70 percentneutralization efficiency.

Vainionpaa, Jaakko Hannes; Leung, Ka Ngo; Kwan, Joe W.; Levinton,Fred

2007-08-01T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

Magnetometry of random AC magnetic fields using a single Nitrogen-Vacancy center  

E-Print Network (OSTI)

We report on the use of a single NV center to probe fluctuating AC magnetic fields. Using engineered currents to induce random changes in the field amplitude and phase, we show that stochastic fluctuations reduce the NV center sensitivity and, in general, make the NV response field-dependent. We also introduce two modalities to determine the field spectral composition, unknown a priori in a practical application. One strategy capitalizes on the generation of AC-field-induced coherence 'revivals', while the other approach uses the time-tagged fluorescence intensity record from successive NV observations to reconstruct the AC field spectral density. These studies are relevant for magnetic sensing in scenarios where the field of interest has a non-trivial, stochastic behavior, such as sensing unpolarized nuclear spin ensembles at low static magnetic fields.

Abdelghani Laraoui; Jonathan S. Hodges; Carlos A. Meriles

2010-09-02T23:59:59.000Z

342

Magnetometry of random AC magnetic fields using a single Nitrogen-Vacancy center  

E-Print Network (OSTI)

We report on the use of a single NV center to probe fluctuating AC magnetic fields. Using engineered currents to induce random changes in the field amplitude and phase, we show that stochastic fluctuations reduce the NV center sensitivity and, in general, make the NV response field-dependent. We also introduce two modalities to determine the field spectral composition, unknown a priori in a practical application. One strategy capitalizes on the generation of AC-field-induced coherence 'revivals', while the other approach uses the time-tagged fluorescence intensity record from successive NV observations to reconstruct the AC field spectral density. These studies are relevant for magnetic sensing in scenarios where the field of interest has a non-trivial, stochastic behavior, such as sensing unpolarized nuclear spin ensembles at low static magnetic fields.

Laraoui, Abdelghani; Meriles, Carlos A

2010-01-01T23:59:59.000Z

343

Spinning a New Type of Magnetic Field | U.S. DOE Office of Science (SC)  

NLE Websites -- All DOE Office Websites (Extended Search)

Spinning a New Type of Magnetic Field Spinning a New Type of Magnetic Field Basic Energy Sciences (BES) BES Home About Research Facilities Science Highlights Benefits of BES Funding Opportunities Basic Energy Sciences Advisory Committee (BESAC) News & Resources Contact Information Basic Energy Sciences U.S. Department of Energy SC-22/Germantown Building 1000 Independence Ave., SW Washington, DC 20585 P: (301) 903-3081 F: (301) 903-6594 E: sc.bes@science.doe.gov More Information » October 2013 Spinning a New Type of Magnetic Field Harnessing the spins of electrons in a new way - enabling efficient magnetic switching and holding promise for spintronic devices. Print Text Size: A A A Subscribe FeedbackShare Page Click to enlarge photo. Enlarge Photo Image courtesy of John Xiao Schematic of mechanism for generating a magnetic field. The system consists

344

Non-locality of energy separating transformations for Dirac electrons in a magnetic field  

E-Print Network (OSTI)

We investigate a non-locality of Moss-Okninski transformation (MOT) used to separate positive and negative energy states in the 3+1 Dirac equation for relativistic electrons in the presence of a magnetic field. Properties of functional kernels generated by the MOT are analyzed and kernel non-localities are characterized by calculating their second moments parallel and perpendicular to the magnetic field. Transformed functions are described and investigated by computing their variances. It is shown that the non-locality of the energy-separating transformation in the direction parallel to the magnetic field is characterized by the Compton wavelength $\\lambda_c=\\hbar/mc$. In the plane transverse to magnetic field the non-locality depends both on magnetic radius $L=(\\hbar/eB)^{1/2}$ and $\\lambda_c$. The non-locality of MO transformation for the 2+1 Dirac equation is also considered.

Tomasz M. Rusin; Wlodek Zawadzki

2011-10-12T23:59:59.000Z

345

The impact of magnetic field on the thermal evolution of neutron stars  

E-Print Network (OSTI)

The impact of strong magnetic fields B>10e13 G on the thermal evolution of neutron stars is investigated, including crustal heating by magnetic field decay. For this purpose, we perform 2D cooling simulations with anisotropic thermal conductivity considering all relevant neutrino emission processes for realistic neutron stars. The standard cooling models of neutron stars are called into question by showing that the magnetic field has relevant (and in many cases dominant) effects on the thermal evolution. The presence of the magnetic field significantly affects the thermal surface distribution and the cooling history of these objects during both, the early neutrino cooling era and the late photon cooling era. The minimal cooling scenario is thus more complex than generally assumed. A consistent magneto-thermal evolution of magnetized neutron stars is needed to explain the observations.

Deborah N. Aguilera; José A. Pons; Juan A. Miralles

2007-12-09T23:59:59.000Z

346

The impact of magnetic field on the thermal evolution of neutron stars  

E-Print Network (OSTI)

The impact of strong magnetic fields B>10e13 G on the thermal evolution of neutron stars is investigated, including crustal heating by magnetic field decay. For this purpose, we perform 2D cooling simulations with anisotropic thermal conductivity considering all relevant neutrino emission processes for realistic neutron stars. The standard cooling models of neutron stars are called into question by showing that the magnetic field has relevant (and in many cases dominant) effects on the thermal evolution. The presence of the magnetic field significantly affects the thermal surface distribution and the cooling history of these objects during both, the early neutrino cooling era and the late photon cooling era. The minimal cooling scenario is thus more complex than generally assumed. A consistent magneto-thermal evolution of magnetized neutron stars is needed to explain the observations.

Aguilera, Deborah N; Miralles, Juan A

2007-01-01T23:59:59.000Z

347

Gas Kinetic Study of Magnetic Field Effects on Plasma Plumes  

E-Print Network (OSTI)

Plasma flow physics in magnetic nozzles must be clearly understood for optimal design of plasma propulsion devices. Toward that end, in this thesis we: i) perform an extensive literature survey of magnetic nozzle physics, ii) assess the validity of magnetohydrodynamics for studying magnetic nozzle physics, and iii) illustrate the effects of the Hall term in simple flows as well as in magnetic nozzle configurations through numerical experiments with the Magneto-Gas Kinetic Method (MGKM). The crucial steps necessary for thrust generation in magnetic nozzles are energy conversion, plasma detachment, and momentum transfer. These three physical phenomena must be understood to optimize magnetic nozzle design. The operating dimensionless parameter ranges of six prominent experiments are considered and the corresponding mechanisms are discussed. An order of magnitude analysis of the governing equations reveal: i) most magnetic nozzles under consideration operate at the edge of the continuum regime rendering continuum-based description and computation valid; ii) in the context of MHD framework, the generalized Ohm’s law must be used to capture all of the relevant physics. This work also continues the development of the Magneto Gas Kinetic Method (MGKM) computational tool. Validation of the solver is performed in shock-tube and Hartmann channel flows in the Hall physics regime. Comparison with theory and available data is made whenever possible. Novel numerical experiments of magnetic nozzle plasma jets in the Hall regime are performed, confirming the theoretically predicted azimuthal rotation of the plasma jet due to Hall physics. The primary conclusion from this work is that the addition of the Hall effect generates helical structures in magnetic nozzle plasma flows. Preliminary results are encouraging for future magnetic nozzle studies and further challenges are identified.

Ebersohn, Frans 1987-

2012-12-01T23:59:59.000Z

348

Generation of multiscale magnetic field by parity-invariant time-periodic flows  

E-Print Network (OSTI)

We study generation of magnetic fields involving large spatial scales by time- and space-periodic small-scale parity-invariant flows. The anisotropic magnetic eddy diffusivity tensor is calculated by the standard procedure involving expansion of magnetic modes and their growth rates in power series in the scale ratio. Our simulations, conducted for flows with random harmonic composition and exponentially decaying energy spectra, demonstrate that enlargement of the spatial scale of magnetic field is beneficial for generation by time-periodic flows. However, they turn out, in general, to be less efficient dynamos, than steady flows.

V. A. Zheligovsky; O. M. Podvigina

2002-07-28T23:59:59.000Z

349

Electric Field Control of Ferromagnetism and Magnetic Devices Using Multiferroics  

E-Print Network (OSTI)

4 Electric field control of ferromagnetism: In-plane5 Electric field control of ferromagnetism: out-of-plane6.3.3 Electric field control of spin valve resistance

Heron, John Thomas

2013-01-01T23:59:59.000Z

350

MAGNETIC HELICITY OF SELF-SIMILAR AXISYMMETRIC FORCE-FREE FIELDS  

Science Conference Proceedings (OSTI)

In this paper, we continue our theoretical studies addressing the possible consequences of magnetic helicity accumulation in the solar corona. Our previous studies suggest that coronal mass ejections (CMEs) are natural products of coronal evolution as a consequence of magnetic helicity accumulation and that the triggering of CMEs by surface processes such as flux emergence also have their origin in magnetic helicity accumulation. Here, we use the same mathematical approach to study the magnetic helicity of axisymmetric power-law force-free fields but focus on a family whose surface flux distributions are defined by self-similar force-free fields. The semi-analytical solutions of the axisymmetric self-similar force-free fields enable us to discuss the properties of force-free fields possessing a huge amount of accumulated magnetic helicity. Our study suggests that there may be an absolute upper bound on the total magnetic helicity of all bipolar axisymmetric force-free fields. With the increase of accumulated magnetic helicity, the force-free field approaches being fully opened up with Parker-spiral-like structures present around a current-sheet layer as evidence of magnetic helicity in the interplanetary space. It is also found that among the axisymmetric force-free fields having the same boundary flux distribution, the one that is self-similar is the one possessing the maximum amount of total magnetic helicity. This gives a possible physical reason why self-similar fields are often found in astrophysical bodies, where magnetic helicity accumulation is presumably also taking place.

Zhang Mei [Key Laboratory of Solar Activity, National Astronomical Observatory, Chinese Academy of Sciences, Datun Road A20, Chaoyang District, Beijing 100012 (China); Flyer, Natasha [Institute for Mathematics Applied to Geosciences, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States); Low, Boon Chye [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

2012-08-10T23:59:59.000Z

351

Effects of Electric and Magnetic Fields on Simple Plants  

Science Conference Proceedings (OSTI)

... than 40 years ago suggested that simple plants – grasses, beans, and corn- exhibited varying effects in simulated geomagnetic fields and in electric fields.

352

Scripta Materialia 52 (2004) 461-466 Effect of 30 Tesla Magnetic Field on Transformations in a  

E-Print Network (OSTI)

Scripta Materialia 52 (2004) 461-466 Effect of 30 Tesla Magnetic Field on Transformations transforms to ferrite. Thus, a 30 Tesla magnetic field can raise transformation temperatures by ~90°C during

Cambridge, University of

353

Nonlinear generation mechanism for the vortical electric field in magnetized plasma media  

Science Conference Proceedings (OSTI)

A physical mechanism and nonlinear mathematical formalism for study of generation and further amplification of the vortical electric field in the magnetized plasma are proposed. A modulation instability process in a plasma medium is considered in a strong constant magnetic field. The plasmon condensate is modulated not by a low-frequency ionic sound as is usually done, but by the beating of two high-frequency transverse electromagnetic waves propagating along the external magnetic field. Conditions in which aperiodic instability occurs are found and its increment is defined. This instability leads to a decrease in the scale of Langmuir turbulence along the external magnetic field and to the generation of electromagnetic fields. Dissipative property of the medium increases an amplitude threshold of the pumping waves. It is shown that for sufficiently large amplitudes of pumping waves the effect described in the paper is the defining nonlinear process.

Aburjania, G. D. [Tbilisi State University, M. Nodia Institute of Geophysics, Tbilisi 0143 (Georgia)

2007-10-15T23:59:59.000Z

354

Scalar and Spinor Particles with Low Binding Energy in the Strong Stationary Magnetic Field Studied by Means of Two-and Three-Dimensional Models  

E-Print Network (OSTI)

On the basis of analytic solutions of Schrodinger and Pauli equations for a uniform magnetic field and a single attractive $\\delta({\\bf r})$-potential the equations for the bound one-active electron states are discussed. It is vary important that ground electron states in the magnetic field essentially different from the analog state of spin-0 particles that binding energy has been intensively studied at more then forty years ago. We show that binding energy equations for spin-1/2 particles can be obtained without using of a well-known language of boundary conditions in the model of $\\delta$-potential that has been developed in pioneering works. Obtained equations are used for the analytically calculation of the energy level displacements, which demonstrate nonlinear dependencies on field intensities. It is shown that in a case of the weak intensity a magnetic field indeed plays a stabilizing role in considering systems. However the strong magnetic field shows the opposite action. We are expected that these properties can be of importance for real quantum mechanical fermionic systems in two- and three-dimensional cases.

V. N. Rodionov

2007-02-22T23:59:59.000Z

355

Field polarity dependent nucleation of superconductivity in quasi-one-dimensional magnetic templates.  

SciTech Connect

We investigate the nucleation of superconductivity in an Al/Al{sub 2}O{sub 3}/Py trilayer system by electrical transport measurements. Magnetic force microscopy images taken at room temperature show that the 0.7 {micro}m thick Py-film form stripes of magnetic domains with alternating out-of-plane stray field. After applying a strong out of plane magnetic field H the superconductor/normal phase boundary becomes asymmetric with respect to H = 0. This lack of field polarity symmetry results from the unbalanced size distribution of domains with opposite polarity.

Ataklti, G. W.; Silhanek, A. V.; Van de Vondel, J.; Gillijns, W.; Belkin, A.; Karapetrov, G.; Moshchalkov, V. V.; Materials Science Division; Katholieke Univ. Leuven; Illinois Inst. of Tech.

2010-01-01T23:59:59.000Z

356

RESEARCH ON THE EFFECTS OF MAGNETIC FIELDS ON THERMIONIC POWER GENERATION. Progress Report No. 1  

SciTech Connect

Research concerned with a theoretical and experimental study of magneto- thermionic power generation is reported. This concept promises a number of advantsges over conventional thermionic generators. Low pressure Cs diodes suffer from an undesirable size limitation, because selfinduced magnetic fields reduce current transmission and hence, efficiency. Although this effect does not arise in the small devices tested to date, it becomes important in building larger generators. Analysis indicates that this problem can be virtually eliminnted by the application of a longitudinal magnetic field. An experimental and theoretical study was initiated to verify the predicted magnetic field effects, and to examine their possible use in a-c generation. (auth)

Schock, A.; Kunen, A.E.

1961-10-01T23:59:59.000Z

357

Mean magnetic field renormalization and Kolmogorov's energy spectrum in MHD turbulence  

E-Print Network (OSTI)

In this paper we construct a self-consistent renormalization group procedure for MHD turbulence in which small wavenumber modes are averaged out, and effective mean magnetic field at large wavenumbers is obtained. In this scheme the mean magnetic field scales as $k^{-1/3}$, while the energy spectrum scales as $k^{-5/3}$ similar to that in fluid turbulence. We also deduce from the formalism that the magnitude of cascade rate decreases as the strength of the mean magnetic field is increased.

Mahendra K. Verma

1998-03-15T23:59:59.000Z

358

The effect of highly structured cosmic magnetic fields on ultra-high energy cosmic ray propagation  

E-Print Network (OSTI)

The possibility that the magnetic field is strongly correlated with the large-scale structure of the universe has been recently considered in the literature. In this scenario the intergalactic magnetic field has a strong ($\\mu$G) regular component spanning tens of Mpc but localized in sheets and filaments, while the vast voids in between are almost free of magnetic field. If true, this could have important consequences on the propagation of ultra-high energy cosmic rays, and severely affect our capacity of doing astronomy with charged particles. A quantitative discussion of these effects is given in the present work.

Gustavo Medina Tanco

1998-08-07T23:59:59.000Z

359

Ultra high energy cosmic rays and the large scale structure of the galactic magnetic field  

E-Print Network (OSTI)

We study the deflection of ultra high energy cosmic ray protons in different models of the regular galactic magnetic field. Such particles have gyroradii well in excess of 1 kpc and their propagation in the galaxy reflects only the large scale structure of the galactic magnetic field. A future large experimental statistics of cosmic rays of energy above 10$^{19}$ eV could be used for a study of the large scale structure of the galactic magnetic field if such cosmic rays are indeed charged nuclei accelerated at powerful astrophysical objects and if the distribution of their sources is not fully isotropic.

Todor Stanev

1996-07-17T23:59:59.000Z

360

Approximate Integrals of rf-driven Particle Motion in Magnetic Field  

DOE Green Energy (OSTI)

For a particle moving in nonuniform magnetic field under the action of an rf wave, ponderomotive effects result from rf-driven oscillations nonlinearly coupled with Larmor rotation. Using Lagrangian and Hamiltonian formalism, we show how, despite this coupling, two independent integrals of the particle motion are approximately conserved. Those are the magnetic moment of free Larmor rotation and the quasi-energy of the guiding center motion parallel to the magnetic field. Under the assumption of non-resonant interaction of the particle with the rf field, these integrals represent adiabatic invariants of the particle motion.

I.Y. Dodin; N.J. Fisch

2004-04-26T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Wave breaking phenomenon of lower-hybrid oscillations induced by a background inhomogeneous magnetic field  

Science Conference Proceedings (OSTI)

In a fluid description, we study space-time evolution of lower hybrid modes in a cold quasi-neutral homogeneous plasma in presence of a background inhomogeneous magnetic field. Within a linear analysis, a dispersion relation with inhomogeneous magnetic field shows 'phase mixing' of such oscillations. A manifestation of 'phase mixing' is shown in 'mode coupling.' By using Lagrangian variables, an exact solution is presented in parametric form of this nonlinear time dependent problem. It is demonstrated that initially excited lower hybrid modes always break via phase mixing phenomenon in presence of an inhomogeneous magnetic field. Breaking of such oscillations is revealed by the appearance of spikes in the plasma density profile.

Maity, Chandan; Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Sengupta, Sudip [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)

2012-10-15T23:59:59.000Z

362

Effect of magnetic field on the mechanical properties of magnetostrictive iron-gallium nanowires  

SciTech Connect

This study experimentally investigates the elastic properties of individual iron-gallium nanowires with and without an applied magnetic bias field. The experiments were conducted with a custom manipulator stage designed for use within a scanning electron microscope, where nanowires were mechanically tested both statically and dynamically. Experiments were also performed in the presence of a 20 Oe dc magnetic field in order to identify any variation in wire properties. The results suggest that iron-gallium nanowires possess an elastic modulus very similar to the macroscale value, tensile strengths of more than double the bulk material, and minor magnetic field induced stiffening at low stresses.

Downey, Patrick R.; Flatau, Alison B. [Department of Aerospace Engineering, University of Maryland, 3181 Martin Hall, College Park, Maryland 20742 (United States); McGary, Patrick D.; Stadler, Bethanie J. H. [Department of Electrical and Computer Engineering, University of Minnesota, 200 Union St., Minneapolis, Minnesota 55455 (United States)

2008-04-01T23:59:59.000Z

363

Visualizing DIII-D Tokamak magnetic field lines  

Science Conference Proceedings (OSTI)

Keywords: graphics hardware, haloed lines, illuminated lines, interactive visualization, magentic field, plasma physics, tokamak

Greg Schussman; Kwan-Liu Ma; David Schissel; Todd Evans

2000-10-01T23:59:59.000Z

364

DRIFT COEFFICIENTS OF CHARGED PARTICLES IN TURBULENT MAGNETIC FIELDS  

Science Conference Proceedings (OSTI)

Using test-particle simulations, the off-diagonal elements of the diffusion tensor are evaluated numerically. The comparison of the so-obtained time-dependent drift coefficients with analytical approximations shows that, for weak turbulence strengths or for slab turbulence geometry, the weak scattering result provides an excellent agreement with the numerical results. For two- or three-dimensional turbulence geometry, however, neither the classical scattering result nor alternative analytical approaches provide an accurate description of the numerically obtained values. Furthermore, the influence is discussed of a non-constant energy range in the turbulence spectrum and of non-static turbulence, for which the time dependence is modeled using magnetohydrodynamic plasma waves.

Tautz, R. C. [Zentrum fuer Astronomie und Astrophysik, Technische Universitaet Berlin, Hardenbergstrasse 36, D-10623 Berlin (Germany); Shalchi, A., E-mail: rct@tp4.rub.de, E-mail: andreasm4@yahoo.com [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)

2012-01-10T23:59:59.000Z

365

A general theory of connectivity and current sheets in coronal magnetic fields anchored to discrete sources  

E-Print Network (OSTI)

A general theory of connectivity and current sheets in coronal magnetic fields anchored to discrete are current-free within each domain, and contain singular currents along each of the field's separators. 1 suggested, from reconnection along the single field line lying at the interface of the four resulting flux

Longcope, Dana

366

A Method for Constraining Cosmic Magnetic Field Models Using Ultra-High Energy Cosmic Rays: The Field Scan Method  

E-Print Network (OSTI)

The Galactic magnetic field, locally observed to be on the order of a few $\\mu$G, is sufficiently strong to induce deflections in the arrival directions of ultra-high energy cosmic rays. We present a method that establishes measures of self-consistency for hypothesis sets comprised of cosmic magnetic field models and ultra-high energy cosmic ray composition and source distributions. The method uses two independent procedures to compare the backtracked velocity vectors outside the magnetic field model to the distribution of backtracked velocity directions of many isotropic observations with the same primary energies. This allows for an estimate of the statistical consistency between the observed data and simulated isotropic observations. Inconsistency with the isotropic expectation of source correlation in both procedures is interpreted as the hypothesis set providing a self-consistent description of GMF and UHECR properties for the cosmic ray observations.

Michael S. Sutherland; Brian M. Baughman; James J. Beatty

2012-07-06T23:59:59.000Z

367

Perspective on the Role of Negative Ions and Ion-Ion Plasmas in Heavy Ion Fusion Science, Magnetic Fusion Energy, and Related Fields  

E-Print Network (OSTI)

Fusion Science, Magnetic Fusion Energy, and Related FieldsFusion Science, Magnetic Fusion Energy, and Related Fieldscalled, in the magnetic fusion energy community, a tandem

Kwan, J.W.

2008-01-01T23:59:59.000Z

368

Fowler-Nordheim Electron Cold Emission Formalism in Presence of Strong Magnetic Field  

E-Print Network (OSTI)

Formalisms for both non-relativistic as well as relativistic versions of field emission of electrons in presence of strong quantizing magnetic field, relevant for strongly magnetized neutron stars or magnetars are developed. In the non-relativistic scenario, where electrons obey Schr{$\\ddot{\\rm{o}}$}dinger equation, we have noticed that when Landau levels are populated for electrons in presence of strong quantizing magnetic field the transmission probability exactly vanishes unless the electrons are spin polarized in the opposite direction to the external magnetic field. On the other hand, the cold electron emission under the influence of strong electrostatic field at the poles is totally forbidden from the surface of those compact objects for which the surface magnetic field strength is $\\gg 10^{15}$G (in the eventuality that they may exist). Whereas in the relativistic case, where the electrons obey Dirac equation, the presence of strong quantizing magnetic field completely forbids the emission of electrons from the surface of compact objects if $B >10^{13}$G.

Arpita Ghosh; Somenath Chakrabarty

2012-06-14T23:59:59.000Z

369

Magnetic Field Generation in Planets and Satellites by Natural Nuclear Fission Reactors  

E-Print Network (OSTI)

One of the most fundamental problems in physics has been to understand the nature of the mechanism that generates the geomagnetic field and the magnetic fields of other planets and satellites. For decades, the dynamo mechanism, thought to be responsible for generating the geomagnetic field and other planetary magnetic fields, has been ascribed to convection in each planet's iron-alloy core. Recently, I described the problems inherent in Earth-core convection and proposed instead that the geomagnetic field is produced by a dynamo mechanism involving convection, not in the fluid core, but in the electrically conductive, fluid, fission-product sub-shell of a natural nuclear fission reactor at the center of the Earth, called the georeactor. Here I set forth in detail the commonality in the Solar System of the matter like that of the inside of the Earth, which is my basis for generalizing the concept of planetary magnetic field generation by natural planetocentric nuclear fission reactors.

J. Marvin Herndon

2007-07-27T23:59:59.000Z

370

NONLINEAR FORCE-FREE MODELING OF MAGNETIC FIELDS IN A SOLAR FILAMENT  

SciTech Connect

We present a striking filament pattern in the nonlinear force-free (NLFF) chromospheric magnetic field of the active region NOAA 10956. The NLFF chromospheric field is extrapolated from the Hinode high-resolution photospheric vector magnetogram using the weighted optimization method. The modeled structure is characterized by a highly sheared field with strong horizontal magnetic components and has a virtually identical shape and location as the filament seen in H{alpha}. The modeled field strength agrees with the recent He I 10830 A observations by Kuckein et al.. The unequivocal resemblance between the NLFF extrapolation and the H{alpha} observation not only demonstrates the ability of the NLFF field to reproduce chromospheric features, but also provides a valuable diagnostic tool for the filament magnetic fields.

Jing Ju; Yuan Yuan; Xu Yan; Liu Rui; Wang Haimin [Space Weather Research Laboratory, New Jersey Institute of Technology, Newark, NJ 07102 (United States); Wiegelmann, Thomas, E-mail: ju.jing@njit.ed, E-mail: yy46@njit.ed, E-mail: yx2@njit.ed, E-mail: rui.liu@njit.ed, E-mail: haimin@flare.njit.ed, E-mail: wiegelmann@linmpi.mpg.d [Max Planck Institut fuer Sonnensystemforschung (MPS), Max-Planck-Strasse 2, 37191 Katlenburg-Lindau (Germany)

2010-08-10T23:59:59.000Z

371

Magnetic anisotropy in a permalloy microgrid fabricated by near-field optical lithography  

Science Conference Proceedings (OSTI)

We report the fabrication and magnetic properties of permalloy microgrids prepared by near-field optical lithography and characterized using high-sensitivity magneto-optical Kerr effect techniques. A fourfold magnetic anisotropy induced by the grid architecture is identified. {copyright} 2001 American Institute of Physics.

Li, S. P.; Lebib, A.; Peyrade, D.; Natali, M.; Chen, Y.; Lew, W. S.; Bland, J. A. C.

2001-07-01T23:59:59.000Z

372

Impact of Permanent Magnet Field on Inductance Variation of a PMLSM Julien Gomand1  

E-Print Network (OSTI)

of Surface Mounted Permanent Magnet Linear Synchronous Motors are generally presented with constantImpact of Permanent Magnet Field on Inductance Variation of a PMLSM Julien Gomand1 , Ghislain Remy1 Linear drive, Modelling, Estimation technique, Synchronous motor, Harmonics. Abstract Analytical models

Paris-Sud XI, Université de

373

The Impact of the BLAST Magnetic Field on the Cerenkov Detectors  

SciTech Connect

We report a factor of two improvement to the efficiencies of a large array of diffusely reflective aerogel Cerenkov detectors which were operated near a high magnetic field. This was accomplished by designing additional magnetic shielding. The improvement was studied by observing the ADC spectrum of the detectors.

Tonguc, B. [Department of Physics, Sakarya University, 54187 Adapazari (Turkey)

2008-04-21T23:59:59.000Z

374

Electric fields in solar magnetic structures due to gradient driven instabilities: heating and acceleration of particles  

E-Print Network (OSTI)

The electrostatic instabilities driven by the gradients of the density, temperature and magnetic field, are discussed in their application to solar magnetic structures. Strongly growing modes are found for some typical plasma parameters. These instabilities i) imply the presence of electric fields that can accelerate the plasma particles in both perpendicular and parallel directions with respect to the magnetic field vector, and ii) can stochastically heat ions. The perpendicular acceleration is to the leading order determined by the $\\bmath{E}\\times \\bmath{B}$-drift acting equally on both ions and electrons, while the parallel acceleration is most effective on electrons. The experimentally confirmed stochastic heating is shown to act mainly in the direction perpendicular to the magnetic field vector and acts stronger on heavier ions. The energy release rate and heating may exceed for several orders of magnitude the value accepted as necessary for a self-sustained heating in the solar corona. The energy sourc...

Vranjes, J

2009-01-01T23:59:59.000Z

375

Extracting Nucleon Magnetic Moments and Electric Polarizabilities from Lattice QCD in Background Electric Fields  

E-Print Network (OSTI)

Nucleon properties are investigated in background electric fields. As the magnetic moments of baryons affect their relativistic propagation in constant electric fields, electric polarizabilities cannot be determined without knowledge of magnetic moments. We devise combinations of nucleon correlation functions in external electric fields to isolate both observables. Using an ensemble of anisotropic gauge configurations with dynamical clover fermions, we demonstrate how magnetic moments and electric polarizabilities can be determined from lattice QCD simulations in background electric fields. We obtain results for both the neutron and proton, however, our study is currently limited to electrically neutral sea quarks. The value we extract for the nucleon isovector magnetic moment is comparable to that obtained from measuring lattice three-point functions at similar pion masses.

Detmold, William; Walker-Loud, Andre

2010-01-01T23:59:59.000Z

376

ENHANCED DISSIPATION RATE OF MAGNETIC FIELD IN STRIPED PULSAR WINDS BY THE EFFECT OF TURBULENCE  

SciTech Connect

In this paper, we report on turbulent acceleration of the dissipation of the magnetic field in the post-shock region of a Poynting flux-dominated flow, such as the Crab pulsar wind nebula. We have performed two-dimensional resistive relativistic magnetohydrodynamics simulations of subsonic turbulence driven by the Richtmyer-Meshkov instability at the shock fronts of the Poynting flux-dominated flows in pulsar winds. We find that turbulence stretches current sheets which substantially enhances the dissipation of the magnetic field, and that most of the initial magnetic field energy is dissipated within a few eddy-turnover times. We also develop a simple analytical model for turbulent dissipation of the magnetic field that agrees well with our simulations. The analytical model indicates that the dissipation rate does not depend on resistivity even in the small resistivity limit. Our findings can possibly alleviate the {sigma}-problem in the Crab pulsar wind nebulae.

Takamoto, Makoto [Department of Physics, Kyoto University, Oiwake-cho, Kitashirakawa, Sakyo-ku, Kyoto 606-8502 (Japan); Inoue, Tsuyoshi [Department of Physics and Mathematics, Aoyama Gakuin University, Fuchinobe, Chuou-ku, Sagamihara 252-5258 (Japan); Inutsuka, Shu-ichiro, E-mail: takamoto@tap.scphys.kyoto-u.ac.jp, E-mail: inouety@phys.aoyama.ac.jp, E-mail: inutsuka@nagoya-u.jp [Department of Physics, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan)

2012-08-10T23:59:59.000Z

377

BSA 10-20: Iron-based Superconductors for High-field Magnets  

... a material that allows magnetic fields up to 20 Tesla to be achieved at 4.2 Kelvin. However, Nb3Sn wires typically require a post-winding ...

378

Measuring response of extruded scintillator to UV LED in magnetic field  

SciTech Connect

The experimental results on the performance of the extruded scintillator and WLS fiber, and various LEDs in the magnetic fields of 1.8T and 2.3T respectively, are reported. The methodic used is being described.

Beznosko, D.; Blazey, G.; Dyshkant, A.; Francis, K.; Kubik, D.; Rykalin, V.; /Northern Illinois U.; Tartaglia, M.; /Fermilab; Zutshi, V.; /Northern Illinois U.

2005-05-01T23:59:59.000Z

379

Quantum-limited measurement of magnetic-field gradient with entangled atoms  

E-Print Network (OSTI)

We propose a method to detect the microwave magnetic-field gradient by using a pair of entangled two-component Bose-Einstein condensates. We consider the two spatially separated condensates to be coupled to the two different magnetic fields. The magnetic-field gradient can be determined by measuring the variances of population differences and relative phases between the two-component condensates in two wells. The precision of measurement can reach the Heisenberg limit. We study the effects of one-body and two-body atom losses on the detection. We find that the entangled atoms can outperform the uncorrelated atoms in probing the magnetic fields in the presence of atom losses. The effect of atom-atom interactions is also discussed.

H. T. Ng

2013-01-15T23:59:59.000Z

380

Ferrohydrodynamic flows in uniform and non-uniform rotating magnetic fields  

E-Print Network (OSTI)

Ferrofluids are conventionally used in such DC magnetic field applications as rotary and exclusion seals, stepper motor dampers, and heat transfer fluids. Recent research demonstrates ferrofluid use in alternating and ...

He, Xiaowei, Ph. D. Massachusetts Institute of Technology

2006-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

A Pilot Study of Pregnancy Outcome, Physical Activity and Magnetic Field Exposure  

Science Conference Proceedings (OSTI)

This brief describes a pilot study that addresses the feasibility of a study of pregnancy outcomes in assisted reproductive technology (ART) populations in relation to magnetic field exposure and physical activity.

2012-12-31T23:59:59.000Z

382

On O-X mode conversion in 2D inhomogeneous plasma with a sheared magnetic field  

E-Print Network (OSTI)

The conversion of an ordinary wave to an extraordinary wave in a 2D inhomogeneous slab model of the plasma confined by a sheared magnetic field is studied analytically.

A Yu Popov

2009-08-10T23:59:59.000Z

383

Ferrofluid spin-up flows from uniform and non-uniform rotating magnetic fields  

E-Print Network (OSTI)

When ferrofluid in a cylindrical container is subjected to a rotating azimuthally directed magnetic field, the fluid "spins up" into an almost rigid-body rotation where ferrofluid nanoparticles have both a linear and an ...

Khushrushahi, Shahriar Rohinton

2010-01-01T23:59:59.000Z

384

CMB temperature anisotropy from broken spatial isotropy due to a homogeneous cosmological magnetic field  

Science Conference Proceedings (OSTI)

We derive the cosmic microwave background temperature anisotropy two-point correlation function (including off-diagonal correlations) from broken spatial isotropy due to an arbitrarily oriented homogeneous cosmological magnetic field.

Kahniashvili, Tina [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States); Department of Physics, Laurentian University, Ramsey Lake Road, Sudbury, ON P3E 2C6 (Canada); National Abastumani Astrophysical Observatory, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Lavrelashvili, George [Department of Theoretical Physics, A. Razmadze Mathematical Institute, 1 M. Aleksidze, Tbilisi, GE-0193 (Georgia); Ratra, Bharat [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States)

2008-09-15T23:59:59.000Z

385

A two-phase spherical electric machine for generating rotating uniform magnetic fields  

E-Print Network (OSTI)

This thesis describes the design and construction of a novel two-phase spherical electric machine that generates rotating uniform magnetic fields, known as a fluxball machine. Alternative methods for producing uniform ...

Lawler, Clinton T. (Clinton Thomas)

2007-01-01T23:59:59.000Z

386

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

E-Print Network (OSTI)

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.

J. Sanchez Almeida

2006-11-22T23:59:59.000Z

387

Stability of Relativistic Matter with Magnetic Fields for Nuclear Charges up to the Critical Value  

E-Print Network (OSTI)

We give a proof of stability of relativistic matter with magnetic fields all the way up to the critical value of the nuclear charge $Z\\alpha=2/\\pi$.

Rupert L. Frank; Elliott H. Lieb; Robert Seiringer

2006-10-24T23:59:59.000Z

388

On magnetic-field-induced dissipationless electric current in helicoidal graphene nanoribbons  

E-Print Network (OSTI)

We argue that twisted (helicoidal) graphene nanoribbons may support dissipationless electric current in the presence of static uniform magnetic field. The non-resistive charge transfer in this parity-odd system should be enhanced by thermal fluctuations.

M. N. Chernodub

2013-04-05T23:59:59.000Z

389

E33: Influence of High Magnetic Field on Intermediate Phase Growth ...  

Science Conference Proceedings (OSTI)

It indicates that high magnetic field of positive gradient promote the growth rate of the .... Mechanical Properties of Low-cost Beta-type Ti-Mn Alloys Fabricated by ...

390

Partially Ionized Atmospheres of Neutron Stars with Strong Magnetic Fields  

DOE Green Energy (OSTI)

We construct hydrogen atmosphere models for strongly magnetized neutron stars in thermodynamic equilibrium, taking into account partial ionization. The presence of bound states affects the equation of state, absorption coefficients, and polarizability tensor of a strongly magnetized plasma. Therefore the partial ionization influences the polarization vectors and opacities of normal electromagnetic waves, and thus the spectra of outgoing radiation. Here we review a model suitable for the most typical neutron-star atmospheres and focus on the problems that remain to be solved for its extension to other atmospheric parameters.

Potekhin, A.

2005-01-28T23:59:59.000Z

391

Plasma particle and energy reflection at a wall with an obliquely incident magnetic field  

SciTech Connect

The particle and energy reflection coefficients are calculated for a plasma incident at a wall with an obliquely incident magnetic field. The salient result of these calculations is that the reflection coefficients can approach unity when the magnetic field is incident at grazing angles. This reflection of particles and energy will be an important process in determining the particle and energy balance in the edge plasma.

Knize, R.J.

1985-07-01T23:59:59.000Z

392

Superconducting magnet development capability of the LLNL (Lawrence Livermore National Laboratory) High Field Test Facility  

SciTech Connect

This paper discusses the following topics: High-Field Test Facility Equipment at LLNL; FENIX Magnet Facility; High-Field Test Facility (HFTF) 2-m Solenoid; Cryogenic Mechanical Test Facility; Electro-Mechanical Conductor Test Apparatus; Electro-Mechanical Wire Test Apparatus; FENIX/HFTF Data System and Network Topology; Helium Gas Management System (HGMS); Airco Helium Liquefier/Refrigerator; CTI 2800 Helium Liquefier; and MFTF-B/ITER Magnet Test Facility.

Miller, J.R.; Shen, S.; Summers, L.T.

1990-02-01T23:59:59.000Z

393

Association of Wire Code Configuration With Long-Term Average 60-Hz Magnetic Fields and Exposure  

Science Conference Proceedings (OSTI)

Previous studies have reported associations between cancer and the configuration of outdoor electric utility lines, popularly referred to as the wire code, which were developed as a surrogate for time-weighted-average (TWA) exposure to magnetic fields. A study was conducted to measure the magnetic fields in over 200 houses in eight areas within the contiguous United States. This interim report presents the major results of that study.

1998-12-16T23:59:59.000Z

394

High-field magnets using high-critical-temperature superconducting thin films  

DOE Patents (OSTI)

High-field magnets fabricated from high-critical-temperature superconducting ceramic (HTSC) thin films which can generate fields greater than 4 Tesla. The high-field magnets are made of stackable disk-shaped substrates coated with HTSC thin films, and involves maximizing the critical current density, superconducting film thickness, number of superconducting layers per substrate, substrate diameter, and number of substrates while minimizing substrate thickness. The HTSC thin films are deposited on one or both sides of the substrates in a spiral configuration with variable line widths to increase the field.

Mitlitsky, Fred (Livermore, CA); Hoard, Ronald W. (Livermore, CA)

1994-01-01T23:59:59.000Z

395

High-field magnets using high-critical-temperature superconducting thin films  

DOE Patents (OSTI)

High-field magnets fabricated from high-critical-temperature superconducting ceramic (HTSC) thin films which can generate fields greater than 4 Tesla are disclosed. The high-field magnets are made of stackable disk-shaped substrates coated with HTSC thin films, and involves maximizing the critical current density, superconducting film thickness, number of superconducting layers per substrate, substrate diameter, and number of substrates while minimizing substrate thickness. The HTSC thin films are deposited on one or both sides of the substrates in a spiral configuration with variable line widths to increase the field. 4 figures.

Mitlitsky, F.; Hoard, R.W.

1994-05-10T23:59:59.000Z

396

Transport of Magnetic Field by a Turbulent Flow of Liquid Sodium  

SciTech Connect

We study the effect of a turbulent flow of liquid sodium generated in the von Karman geometry, on the localized field of a magnet placed close to the frontier of the flow. We observe that the field can be transported by the flow on distances larger than its integral length scale. In the most turbulent configurations, the mean value of the field advected at large distance vanishes. However, the rms value of the fluctuations increases linearly with the magnetic Reynolds number. The advected field is strongly intermittent.

Volk, R.; Odier, Ph.; Pinton, J.-F. [Laboratoire de Physique de l'Ecole Normale Superieure de Lyon, CNRS UMR 5672, 47 allee d'Italie, 69364 Lyon Cedex 07 (France); Ravelet, F.; Monchaux, R.; Chiffaudel, A.; Daviaud, F. [Service de Physique de l'Etat Condense, Direction des Sciences de la Matiere, CEA-Saclay, CNRS URA 2464, 91191 Gif-sur-Yvette cedex (France); Berhanu, M.; Fauve, S.; Mordant, N.; Petrelis, F. [Laboratoire de Physique Statistique de l'Ecole Normale Superieure, CNRS UMR 8550, 24 Rue Lhomond, 75231 Paris Cedex 05 (France)

2006-08-18T23:59:59.000Z

397

TVA's 500-kV electric and magnetic fields: measurements and analyses  

Science Conference Proceedings (OSTI)

This report summarizes the results of the 500-kV electric and magnetic fields data project, performed by the Electrical Systems Group of the Tennessee Valley Authority (TVA). The objectives of the project were to measure, record, and analyze electric and magnetic fields in the vicintiy of TVA's 500-kV transmission lines. Also the effects of transmission line fields on the growth and development of selected agricultural and forest plant species were to be investigated. This report contains only the categorization and the statistical analysis of the fields data.

Not Available

1983-09-01T23:59:59.000Z

398

The magnetic field along the jets of NGC 4258 as deduced from high frequency radio observations  

E-Print Network (OSTI)

We present 2.4" resolution, high sensitivity radio continuum observations of the nearby spiral galaxy NGC 4258 in total intensity and linear polarization obtained with the Very Large Array at 3.6 cm (8.44 GHz). The radio emission along the northern jet and the center of the galaxy is polarized and allows investigation of the magnetic field. Assuming energy-equipartition between the magnetic field and the relativistic particles and distinguishing between (1) a relativistic electron-proton jet and (2) a relativistic electron-positron jet, we obtain average magnetic field strengths of about (1) 310\\muG and (2) 90\\muG. The rotation measure is determined to range from -400 to -800 rad/m^2 in the northern jet. Correcting the observed E-vectors of polarized intensity for Faraday rotation, the magnetic field along the jet turns out to be orientated mainly along the jet axis. An observed tilt with respect to the jet axis may indicate also a toroidal magnetic field component or a slightly helical magnetic field around the northern jet.

M. Krause; A. L"ohr

2004-03-05T23:59:59.000Z

399

RESEARCH Open Access H low field nuclear magnetic resonance  

E-Print Network (OSTI)

magnetic resonance, Biodiesel, Biodiesel physical properties, Chemometrics, Laplace inversion of biodiesel Paula Berman1 , Adi Leshem1 , Oren Etziony1 , Ofer Levi2 , Yisrael Parmet2 , Michael Saunders3 and Zeev Wiesman1* Abstract Background: Biodiesel production has increased dramatically over the last

Stanford University

400

Ground Magnetics At San Francisco Volcanic Field Area (Warpinski, Et Al.,  

Open Energy Info (EERE)

Warpinski, Et Al., Warpinski, Et Al., 2004) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground Magnetics At San Francisco Volcanic Field Area (Warpinski, Et Al., 2004) Exploration Activity Details Location San Francisco Volcanic Field Area Exploration Technique Ground Magnetics Activity Date Usefulness not indicated DOE-funding Unknown Notes Northern Arizona University has re-assessed the existing exploration data, geologically mapped the target area, obtained rock samples for age dating and mineral chemistry, performed gravity and magnetic surveys, and integrated these results to identify potential drilling targets and sites. Further work may occur in 2004 or 2005. References N. R. Warpinski, A. R. Sattler, R. Fortuna, D. A. Sanchez, J.

Note: This page contains sample records for the topic "weak magnetic fields" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


401

A Relativistic Generalization of Fowler-Nordheim Cold Emission in Presence of Strong Magnetic Field  

E-Print Network (OSTI)

A relativistic version of cold emission of electrons in presence of strong magnetic field, relevant for strongly magnetized neutron stars is obtained. It is found that in this scenario, a scalar type potential barrier does not allow quantum tunneling through the surface. Whereas, in presence of a vector type surface barrier, the probability of electron emission is much larger compared to the original Fowler-Nordheim cold emission of electrons. It is found that the relativistic version in presence of strong magnetic field does not follow exponential decay.

Arpita Ghosh; Somenath Chakrabarty

2010-06-27T23:59:59.000Z

402

Calculation methods and detection techniques for electric and magnetic fields from power lines with measurement verification  

E-Print Network (OSTI)

An accurate determination and characterization of electric and magnetic fields produced by power lines is a complex task. Different models must be used for far fields and for near fields. This study is centered on computation and measurement aspects of extremely low frequency magnetic fields in the direct proximity of the conductors of power lines, situated well above the ground level. Conventional approximation of a sagged wire as a straight horizontal conductor of infinite length has been substituted with a periodical catenary model of the conductors A series of measurements performed with all electric utility bucket truck provide unique magnetic field data very close to the conductors. A conceptual design of a power line proximity detector is proposed as a result of these studies.

Mamishev, Alexander V

1994-01-01T23:59:59.000Z

403

Magnetars: Time Evolution, Superfluid Properties, and Mechanism of Magnetic Field Decay  

E-Print Network (OSTI)

We calculate the coupled thermal evolution and magnetic field decay in relativistic model neutron stars threaded by superstrong magnetic fields (B > 10^{15} G). Our main goal is to evaluate how such ``magnetars'' evolve with time and how field decay modifies the transitions to core superfluidity and cooling dominated by surface X-ray emission. Observations of a thermal X-ray spectral component and fast timing noise place strong constraints on the presence of a superfluid core. We find that the transition to core superfluidity can be significantly delayed by field decay in the age range ~ 10^3-10^5 yrs. The mechanism of Hall drift is related to the stability of the core magnetic field, and to currents flowing outward through the crust. The heating effect is enhanced if it is continuous rather than spasmodic. Condensation of a heavy element layer at the surface is shown to cause only modest changes in the outward conduction of heat.

P. Arras; A. Cumming; C. Thompson

2004-01-27T23:59:59.000Z

404

Electric and Magnetic Fields (EMF) RAPID Program Engineering Project 8: FINAL REPORT, Evaluation of Field Reduction Technologies, Volume 1 (Report) and Volume 2 (Appendices)  

SciTech Connect

This draft report consists of two volumes. Volume 1, the main body, contains an introducto~ sectionj an overview of magnetic fields sectio~ and field reduction technology evaluation section. Magnetic field reduction methods are evalpated for transmission lines, distribution Iines,sulxtations, building wiring applkmd machinery, and transportation systems. The evaluation considers effectiveness, co% and other ftiors. Volume 2 contains five appendices, Append~ A presents magnetic field shielding information. Appendices B and C present design assumptions and magnetic field plots for transmission and distribution lines, respectively. Appendices D and E present cost estimate details for transmission and distribution limes, respectively.

Commonwealth Associates, Inc.; IIT Research Institute

1997-08-01T23:59:59.000Z

405

Relativistic diodes in crossed magnetic fields. Progress report, June 1, 1975--February 15, 1976  

DOE Green Energy (OSTI)

The behavior of a cylindrical field emission diode (radial potential approximately 200 kV) was studied in the presence of an externally applied axial magnetic field B less than or equal to 16 kG. Observations made of the space charge-limited electron current (approximately 50 kA) compare favorably with theory which takes into account the presence of both the external axial magnetic field and the azimuthal self-magnetic field generated by current flow in the cathode. At magnetic fields exceeding the critical field necessary for cutoff, small but not insignificant current flows persist. The associated microwave emission suggests that this residual current is being driven by an as-yet-unidentified high-frequency instability. Time-resolved measurements of the diode current and voltage lead to a determination of the expansion velocity of the cathode and anode plasmas. It was found that an external magnetic field of approximately 5 kG suffices to stop plasma motion. This value is in agreement with magnetohydrodynamic computations for a hydrogen plasma having an initial temperature of a few eV. Spectroscopic measurements of the diode plasma have shown that hydrogen is indeed the dominant ion species. Stark broadening of the spectral lines yields their number density.

Bekefi, G.

1976-02-01T23:59:59.000Z

406

Oceanic Internal Waves Are Not Weak Waves  

Science Conference Proceedings (OSTI)

It is shown that the oceanic internal wave field is too energetic by roughly two orders of magnitude to be treated theoretically as an assemblage of weakly interacting waves. This may be seen both from recent weak wave theoretical calculations ...

Greg Holloway

1980-06-01T23:59:59.000Z

407

ABRUPT LONGITUDINAL MAGNETIC FIELD CHANGES AND ULTRAVIOLET EMISSIONS ACCOMPANYING SOLAR FLARES  

Science Conference Proceedings (OSTI)

We have used Transition Region and Coronal Explorer 1600 A images and Global Oscillation Network Group (GONG) magnetograms to compare ultraviolet (UV) emissions from the chromosphere to longitudinal magnetic field changes in the photosphere during four X-class solar flares. An abrupt, significant, and persistent change in the magnetic field occurred across more than 10 pixels in the GONG magnetograms for each flare. These magnetic changes lagged the GOES flare start times in all cases, showing that they were consequences and not causes of the flares. Ultraviolet emissions were spatially coincident with the field changes. The UV emissions tended to lag the GOES start times for the flares and led the changes in the magnetic field in all pixels except one. The UV emissions led the photospheric field changes by 4 minutes on average with the longest lead being 9 minutes; however, the UV emissions continued for tens of minutes, and more than an hour in some cases, after the field changes were complete. The observations are consistent with the picture in which an Alfven wave from the field reconnection site in the corona propagates field changes outward in all directions near the onset of the impulsive phase, including downward through the chromosphere and into the photosphere, causing the photospheric field changes, whereas the chromosphere emits in the UV in the form of flare kernels, ribbons, and sequential chromospheric brightenings during all phases of the flare.

Johnstone, B. M.; Petrie, G. J. D.; Sudol, J. J. [Department of Physics, West Chester University, West Chester, PA 19383 (United States)

2012-11-20T23:59:59.000Z

408

A Snowflake-Shaped Magnetic Field Holds Promise for Taming Harsh Fusion  

NLE Websites -- All DOE Office Websites (Extended Search)

A Snowflake-Shaped Magnetic Field Holds Promise for Taming Harsh Fusion A Snowflake-Shaped Magnetic Field Holds Promise for Taming Harsh Fusion Plasmas Recent experiments have confirmed the great potential of a novel plasma-material interface concept. By U.S Department of Energy Office of Science October 31, 2012 Tweet Widget Facebook Like Google Plus One National Spherical Torus Experiment (Photo by Elle Starkman, Office of Communications, PPPL) National Spherical Torus Experiment The Science Heat escaping from the core of a twelve-million degree nuclear fusion plasma device was successfully contained by a snowflake-shaped magnetic field to mitigate its impact on device walls. The Impact One of the grand challenges of the magnetic fusion research is to "tame the plasma-material interface"-to develop an interface between the hot

409

Options for Shielding Tokamak Cooling Water Electrical Components against High Magnetic Fields  

SciTech Connect

The Tokamak Cooling Water System (TCWS) Instrumentation and Control (I&C) components of ITER will be located in areas of relatively high magnetic fields. Previous tests on electrical and I&C components have indicated that shielding will be required to protect these components from such magnetic fields. To accomplish this, studies were performed by AREVA Federal Services (AFS) in support of the TCWS Design project with the intent of identifying an optimal solution for shielding I&C components. This report presents a summary of these studies and presents design options for providing magnetic shielding to ITER TCWS I&C components and electrical equipment that are susceptible to the magnetic fields present.

Korsah, Kofi [ORNL; Michael, Smith [AREVA Federal Services LLC; Kim, Seokho H [ORNL; Charles, Neumeyer [Princeton Plasma Physics Laboratory (PPPL)

2011-01-01T23:59:59.000Z

410

H II REGION DRIVEN GALACTIC BUBBLES AND THEIR RELATIONSHIP TO THE GALACTIC MAGNETIC FIELD  

SciTech Connect

The relative alignments of mid-infrared traced Galactic bubbles are compared to the orientation of the mean Galactic magnetic field in the disk. The orientations of bubbles in the northern Galactic plane were measured and are consistent with random orientations-no preferential alignment with respect to the Galactic disk was found. A subsample of H II region driven Galactic bubbles was identified, and as a single population they show random orientations. When this subsample was further divided into subthermal and suprathermal H II regions, based on hydrogen radio recombination linewidths, the subthermal H II regions showed a marginal deviation from random orientations, but the suprathermal H II regions showed significant alignment with the Galactic plane. The mean orientation of the Galactic disk magnetic field was characterized using new near-infrared starlight polarimetry and the suprathermal H II regions were found to preferentially align with the disk magnetic field. If suprathermal linewidths are associated with younger H II regions, then the evolution of young H II regions is significantly affected by the Galactic magnetic field. As H II regions age, they cease to be strongly linked to the Galactic magnetic field, as surrounding density variations come to dominate their morphological evolution. From the new observations, the ratios of magnetic-to-ram pressures in the expanding ionization fronts were estimated for younger H II regions.

Pavel, Michael D.; Clemens, D. P., E-mail: pavelmi@bu.edu, E-mail: clemens@bu.edu [Institute for Astrophysical Research, Boston University, 725 Commonwealth Ave., Boston, MA 02215 (United States)

2012-12-01T23:59:59.000Z

411

Magnetic field and field orientation dependence of the critical current density in Bi-2212 round wires and other HTS conductors  

Science Conference Proceedings (OSTI)

The authors have performed measurements of the magnetic field dependence of the critical current density J{sub c} of Bi-2212/Ag round wire produced by isothermal melt processing. In contrast to the case for flat tape, there is very little dependence of J{sub c} on the direction of the magnetic field as it is rotated normal to the wire axis, which is the direction of the nominal current flow. However, when the angle of the magnetic field direction is rotated from normal to the wire axis to parallel to that axis, J{sub c} at 64 K and 0.2 T increases by more than a factor of four. Again, this is in contrast to the results observed for Bi-2212/Ag and Bi-2223/Ag flat tapes, which show no anisotropy under similar experimental conditions. They can explain these differences in angular anisotropy by referring to the microstructure of these two conductor types, which have distinctly different types of grain alignment. They discuss the general behavior of the dependence of J{sub c} on the orientation of a magnetic field for high temperature superconductors.

Willis, J.O.; Holesinger, T.G.; Coulter, J.Y.; Maley, M.P. [Los Alamos National Lab., NM (United States). Superconductivity Technology Center

1996-10-01T23:59:59.000Z

412

Disk Accretion Flow Driven by Large-Scale Magnetic Fields: Solutions with Constant Specific Energy  

E-Print Network (OSTI)

(Abridged) We study the dynamical evolution of a stationary, axisymmetric, and perfectly conducting cold accretion disk containing a large-scale magnetic field around a Kerr black hole, trying to understand the relation between accretion and the transportation of angular momentum and energy. We solve the radial momentum equation for solutions corresponding to an accretion flow that starts from a subsonic state at infinity, smoothly passes the fast critical point, then supersonically falls into the horizon of the black hole. The solutions always have the following features: 1) The specific energy of fluid particles remains constant but the specific angular momentum is effectively removed by the magnetic field. 2) At large radii, where the disk motion is dominantly rotational, the energy density of the magnetic field is equipartitioned with the rotational energy density of the disk. 3) Inside the fast critical point, where radial motion becomes important, the ratio of the electromagnetic energy density to the kinetic energy density drops quickly. The results indicate that: 1) Disk accretion does not necessarily imply energy dissipation since magnetic fields do not have to transport or dissipate a lot of energy as they effectively transport angular momentum. 2) When resistivity is small, the large-scale magnetic field is amplified by the shearing rotation of the disk until the magnetic energy density is equipartitioned with the rotational energy density, ending up with a geometrically thick disk. This is in contrast with the evolution of small-scale magnetic fields where if the resistivity is nonzero the magnetic energy density is likely to be equipartitioned with the kinetic energy density associated with local random motions (e.g., turbulence), making a thin Keplerian disk possible.

Li-Xin Li

2002-12-20T23:59:59.000Z

413

Spin glass transition in a magnetic field: a renormalization group study  

E-Print Network (OSTI)

We study the transition of short range Ising spin glasses in a magnetic field, within a general replica symmetric field theory, which contains three masses and eight cubic couplings, that is defined in terms of the fields representing the replicon, anomalous and longitudinal modes. We discuss the symmetry of the theory in the limit of replica number n ? 0, and consider the regular case where the longitudinal and anomalous masses remain degenerate. The spin glass transitions in zero and non-zero field are analyzed in a common framework. The mean field treatment shows the usual results, that is a transition in zero field, where all the modes become critical, and a transition in nonzero field, at the de Almeida-Thouless (AT) line, with only the replicon mode critical. Renormalization group methods are used to study the critical behavior, to order ? = 6 ? d. In the general theory we find a stable fixed-point associated to the spin glass transition in zero field. This fixed-point becomes unstable in the presence of a small magnetic field, and we calculate crossover exponents, which we relate to zero-field critical exponents. In a finite magnetic field, we find no physical stable fixed-point to describe the AT transition, in agreement with previous results of other authors. PACS numbers: 75.50.Lk, 75.40.Cx 1 I

I. R. Pimentel; T. Temesvári; C. De Dominicis

2002-01-01T23:59:59.000Z

414

Prediction of magnetic field near power lines by normalized radial basis function network  

Science Conference Proceedings (OSTI)

Over the past several decades, concerns have been raised over the possibility that the exposure to extremely low frequency electromagnetic fields from power lines may have harmful effects on human and living organisms. This work involved the computation ... Keywords: Gradient descent algorithm, Magnetic fields, NRBF network, Power lines, Prediction, Training set

Vesna Rankovi?; Jasna Radulovi?

2011-11-01T23:59:59.000Z

415

Thin superconducting disk with field-dependent critical current: Magnetization and ac susceptibilities  

E-Print Network (OSTI)

Thin superconducting disk with field-dependent critical current: Magnetization and ac of a superconducting thin disk are calculated in the critical-state model assuming a field-dependent critical current for the flux and current distributions Phys. Rev. B 60, 13 112 1999 for a disk placed in a perpendicular

Johansen, Tom Henning

416

Assessment of children's long-term exposure to magnetic fields (the Enertech study)  

SciTech Connect

The objective of this study was to evaluate whether engineering approaches to estimating residential fields due to ground currents and outdoor line currents provide a valid basis for assessing magnetic field exposure. Investigators selected 35 homes representing a range of external utility wiring and home grounding characteristics. During two visits to the study houses about half a year apart, they measured ground currents, indoor magnetic fields (both 24-hour and spot), outdoor magnetic field profiles, and using a three-axis integrating meter (the AMEX-3D) also measured personal exposure. They also collected data on residential power consumption and utility load on the distribution system during the measurement period. The investigators tested whether engineering-based exposure estimates correlated with those measured on the AMEX-3D. Time-weighted-average (TWA) magnetic field exposure as recorded on the AMEX-3D correlated significantly with both the power consumed within individual residences and the power flowing on the utility distribution system. Spot-measured fields were also associated with these quantities. However, compared with the use of spot-measured fields or the Wertheimer-Leeper wiring code, the model incorporating residential consumption and utility loading did not improve the predictability of personal exposure. In addition, temporal variation in the consumption/loading data was not useful in predicting temporal differences in exposure patterns. Despite the statistically significant correlations of spot-measured fields with exposure during the same or even the other of two visits, personal exposures during the two visits were poorly correlated.

Kaune, W.T.; Zaffanella, L.E.

1992-11-01T23:59:59.000Z

417

Solar Wind and Interplanetary Magnetic Field: A Tutorial C. T. Russell  

E-Print Network (OSTI)

Solar Wind and Interplanetary Magnetic Field: A Tutorial C. T. Russell Institute of Geophysics at the center of the sun to its radiation into space by the photosphere, but most importantly for the solar wind controls the properties of the solar wind. In this tutorial review we examine the properties of the fields

Russell, Christopher T.

418

Fermi Surface of Uranium at Ambient Pressure Gregory S. Boebinger, National High Magnetic Field Laboratory  

E-Print Network (OSTI)

Fermi Surface of ­Uranium at Ambient Pressure Gregory S. Boebinger, National High Magnetic Field Laboratory DMR-Award 0654118 DC Field Facility User Program The fermi surface of ­Uranium has been measured surface of alpha-uranium at ambient pressure, Phys. Rev. B Rapid Commun., 80, 241101 (2009). B//c-axis B

Weston, Ken

419

Correlated time derivatives of current, electric field intensity, and magnetic flux density for triggered lightning at 15 m  

E-Print Network (OSTI)

Correlated time derivatives of current, electric field intensity, and magnetic flux density current and its time derivative correlated with the corresponding electric field intensity and magnetic. The measured current derivative waveform and the return stroke portion of the magnetic flux density derivative

Florida, University of

420

Study of Various Slanted Air-gap Structures of Interior Permanent Magnet Synchronous Motor with Brushless Field Excitation  

E-Print Network (OSTI)

Study of Various Slanted Air-gap Structures of Interior Permanent Magnet Synchronous Motor of the slanted air-gap structure of an interior permanent magnet synchronous motor with brushless field magnet machine, synchronous motors, torque. I. NOMENCLATURE BFE brushless field excitation IPMSM interior

Tolbert, Leon M.

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421

Bucking Coil Implementation on PMT for Active Cancelling of Magnetic Field  

SciTech Connect

Aerogel and water Cerenkov detectors were employed to tag kaons for a lambda hypernuclear spectroscopic experiment which used the (e,e'K{sup +}) reaction in experimental Hall C at Jefferson Lab (JLab E05-115). Fringe fields from the kaon spectrometer magnet yielded ~5 Gauss at the photomultiplier tubes (PMT) for these detectors which could not be easily shielded. As this field results in a lowered kaon detection efficiency, we implemented a bucking coil on each photomultiplier tubes to actively cancel this magnetic field, thus maximizing kaon detection efficiency.

Gogami, T; Asaturyan, A; Bono, J; Baturin, P; Chen, C; Chiba, A; Chiga, N; Fujii, Y; Hashimoto, O; Kawama, D; Maruta, T; Maxwell, V; Mkrtchyan, A; Nagao, S; Nakamura, S N; Reinhold, J; Shichijo, A; Tang, L; Taniya, N; Wood, S A; Ye, Z

2013-11-01T23:59:59.000Z

422

Effects on Freshwater Organisms of Magnetic Fields Associated with Hydrokinetic Turbines  

SciTech Connect

Underwater cables will be used to transmit electricity between turbines in an array (interturbine cables), between the array and a submerged step-up transformer (if part of the design), and from the transformer or array to shore. All types of electrical transmitting cables (as well as the generator itself) will emit EMF into the surrounding water. The electric current will induce magnetic fields in the immediate vicinity, which may affect the behavior or viability of animals. Because direct electrical field emissions can be prevented by shielding and armoring, we focused our studies on the magnetic fields that are unavoidably induced by electric current moving through a generator or transmission cable. These initial experiments were carried out to evaluate whether a static magnetic field, such as would be produced by a direct current (DC) transmitting cable, would affect the behavior of common freshwater fish and invertebrates.

Cada, Glenn F [ORNL; Bevelhimer, Mark S [ORNL; Riemer, Kristina P [ORNL; Turner, Julie W [ORNL

2011-07-01T23:59:59.000Z

423

Magnetic field characterization of electrical appliances as point sources through in situ measurements  

SciTech Connect

It is shown that magnetic field exposure from a point source can be studied by characterizing the source with a magnetic dipole. A technique based on in situ measurements of amplitude and phase angle of three orthogonal components of the magnetic field at three points at different distances from the source was developed. The method to determine the center and the real and imaginary components of the dipole moment along the three aces is described. The characterization of the source allows the prediction of the field at any distance and along any direction from the source. The effects of background fields and of the source dimensions and complexity on the accuracy of the results are discussed.

Zaffanella, L.E.; Sullivan, T.P. [Enertech Consultants, Lee, MA (United States); Visintainer, I. [CESI, Milan (Italy)

1997-01-01T23:59:59.000Z

424

Probing Solar Magnetic Field with the "Cosmic-Ray Shadow" of the Sun  

E-Print Network (OSTI)

We report on a clear solar-cycle variation of the Sun's shadow in the 10 TeV cosmic-ray flux observed by the Tibet air shower array during a full solar cycle from 1996 to 2009. In order to clarify the physical implications of the observed solar cycle variation, we develop numerical simulations of the Sun's shadow, using the Potential Field Source Surface (PFSS) model and the Current Sheet Source Surface (CSSS) model for the coronal magnetic field. We find that the intensity deficit in the simulated Sun's shadow is very sensitive to the coronal magnetic field structure, and the observed variation of the Sun's shadow is better reproduced by the CSSS model. This is the first successful attempt to evaluate the coronal magnetic field models by using the Sun's shadow observed in the TeV cosmic-ray flux.

Amenomori, M; Chen, D; Chen, T L; Chen, W Y; Cui, S W; Danzengluobu,; Ding, L K; Feng, C F; Feng, Zhaoyang; Feng, Z Y; Gou, Q B; Guo, Y Q; Hakamada, K; He, H H; He, Z T; Hibino, K; Hotta, N; Hu, Haibing; Hu, H B; Huang, J; Jia, H Y; Jiang, L; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Labaciren,; Le, G M; Li, A F; Li, H J; Li, W J; Liu, C; Liu, J S; Liu, M Y; Lu, H; Meng, X R; Mizutani, K; Munakata, K; Nanjo, H; Nishizawa, M; Ohnishi, M; Ohta, I; Onuma, H; Ozawa, S; Qian, X L; Qu, X B; Saito, T; Saito, T Y; Sakata, M; Sako, T K; Shao, J; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, H; Wu, H R; Xue, L; Yamamoto, Y; Yang, Z; Yasue, S; Yuan, A F; Yuda, T; Zhai, L M; Zhang, H M; Zhang, J L; Zhang, X Y; Zhang, Y; Zhang, Yi; Zhang, Ying; Zhaxisangzhu,; Zhou, X X

2013-01-01T23:59:59.000Z

425

Dynamic Phase Transitions In The Spin-2 Ising System Under An Oscillating Magnetic Field Within The Effective-Field Theory  

SciTech Connect

The dynamic phase transitions are studied in the spin-2 Ising model under a time-dependent oscillating magnetic field by using the effective-field theory with correlations. The effective-field dynamic equation is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first- or second-order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic order parameter and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are presented in (T/zJ, h/zJ) plane.

Ertas, Mehmet; Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey)

2010-12-23T23:59:59.000Z

426

Effect of Electric and Magnetic Fields on Spin Dynamics in the Resonant Electric Dipole Moment Experiment  

E-Print Network (OSTI)

A buildup of the vertical polarization in the resonant electric dipole moment (EDM) experiment [Y. F. Orlov, W. M. Morse, and Y. K. Semertzidis, Phys. Rev. Lett. 96, 214802 (2006)] is affected by a horizontal electric field in the particle rest frame oscillating at a resonant frequency. This field is defined by the Lorentz transformation of an oscillating longitudinal electric field and a uniform vertical magnetic one. The effect of a longitudinal electric field is significant, while the contribution from a magnetic field caused by forced coherent longitudinal oscillations of particles is dominant. The effect of electric field on the spin dynamics was not taken into account in previous calculations. This effect is considerable and leads to decreasing the EDM effect for the deuteron and increasing it for the proton. The formula for resonance strengths in the EDM experiment has been derived. The spin dynamics has been calculated.

Alexander J. Silenko

2006-04-11T23:59:59.000Z

427

Influence of a Weak Field of Pulsed DC Electricity on the Behavior and Incidence of Injury in Adult Steelhead and Pacific Lamprey, Final Report.  

DOE Green Energy (OSTI)

Predation by pinnipeds, such as California sea lions Zalophus californianus, Pacific harbor seals Phoca vitulina, and Stellar sea lions Eumetopias jubatus on adult Pacific salmon Oncorhynchus spp in the lower Columbia River has become a serious concern for fishery managers trying to conserve and restore runs of threatened and endangered fish. As a result, Smith-Root, Incorporated (SRI; Vancouver, Washington), manufacturers of electrofishing and closely-related equipment, proposed a project to evaluate the potential of an electrical barrier to deter marine mammals and reduce the amount of predation on adult salmonids (SRI 2007). The objectives of their work were to develop, deploy, and evaluate a passive, integrated sonar and electric barrier that would selectively inhibit the upstream movements of marine mammals and reduce predation, but would not injure pinnipeds or impact anadromous fish migrations. However, before such a device could be deployed in the field, concerns by regional fishery managers about the potential effects of such a device on the migratory behavior of Pacific salmon, steelhead O. mykiss, Pacific lampreys Entoshpenus tridentata, and white sturgeon Acipenser transmontanus, needed to be addressed. In this report, we describe the results of laboratory research designed to evaluate the effects of prototype electric barriers on adult steelhead and Pacific lampreys. The effects of electricity on fish have been widely studied and include injury or death (e.g., Sharber and Carothers 1988; Dwyer et al. 2001; Snyder 2003), physiological dysfunction (e.g., Schreck et al. 1976; Mesa and Schreck 1989), and altered behavior (Mesa and Schreck 1989). Much of this work was done to investigate the effects of electrofishing on fish in the wild. Because electrofishing operations would always use more severe electrical settings than those proposed for the pinniped barrier, results from these studies are probably not relevant to the work proposed by SRI. Field electrofishing operations typically use high voltage and amperage settings and a variety of waveforms, pulse widths (PW), and pulse frequencies (PF), depending on conditions and target species. For example, when backpack electrofishing for trout in a small stream, one might use settings such as 500 V pulsed DC, a PW of 1 ms, and a PF of 60 Hz. In contrast, the electrical barrier proposed by SRI will produce electrical conditions significantly lower than those used in electrofishing, particularly for PW and PF (e.g., PW ranging from 300-1,000 {micro}s and PF from 2-3 Hz). Further, voltage gradients (in V/cm) are predicted to be lower in the electric barrier than those produced during typical electrofishing. Although the relatively weak, pulsed DC electric fields to be produced by the barrier may be effective at deterring pinnipeds, little, if anything, is known about the effects of such low intensity electrical fields on fish behavior. For this research, we evaluated the effects of weak, pulsed DC electric currents on the behavior of adult steelhead and Pacific lamprey and the incidence of injury in steelhead only. In a series of laboratory experiments, we: (1) documented the rate of passage of fish over miniature, prototype electric barriers when they were on and off; (2) determined some electric thresholds beyond which fish would not pass over the barrier; and (3) assessed the incidence and severity of injury in steelhead exposed to relatively severe electrical conditions. The results of this study shoul