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1

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

2

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

3

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

4

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

5

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

6

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

7

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

8

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

9

Random walk of magnetic field lines in dynamical turbulence: A field line tracing method. I. Slab turbulence  

SciTech Connect

To study the wandering of magnetic field lines is an important subject in theoretical physics. Results of field line random walk theories can be applied in plasma physics as well as astrophysics. Previous investigations are based on magnetostatic models. These models have been used in analytical work as well as in computer simulations to warrant mathematical and numerical tractability. To replace the magnetostatic model by a dynamical turbulence model is a difficult task. In the present article, a field line tracing method is used to describe field line wandering in dynamical magnetic turbulence. As examples different models are employed, namely, the plasma wave model, the damping model of dynamical turbulence, and the random sweeping model. It is demonstrated that the choice of the turbulence model has a very strong influence on the field line structure. It seems that if dynamical turbulence effects are included, Markovian diffusion can be found for other forms of the wave spectrum as in the magnetostatic model. Therefore, the results of the present paper are useful to specify turbulence models. As a further application we consider charged particle transport at early times.

Shalchi, A. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada)

2010-08-15T23:59:59.000Z

10

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

11

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

12

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

SciTech Connect

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

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

1994-11-01T23:59:59.000Z

13

Kolmogorov-Sinai entropy in field line diffusion by anisotropic magnetic turbulence  

E-Print Network (OSTI)

The Kolmogorov-Sinai (KS) entropy in turbulent diffusion of magnetic field lines is analyzed on the basis of a numerical simulation model and theoretical investigations. In the parameter range of strongly anisotropic magnetic turbulence the KS entropy is shown to deviate considerably from the earlier predicted scaling relations [Rev. Mod. Phys. {\\bf 64}, 961 (1992)]. In particular, a slowing down logarithmic behavior versus the so-called Kubo number $R\\gg 1$ ($R = (\\delta B / B_0) (\\xi_\\| / \\xi_\\bot)$, where $\\delta B / B_0$ is the ratio of the rms magnetic fluctuation field to the magnetic field strength, and $\\xi_\\bot$ and $\\xi_\\|$ are the correlation lengths in respective dimensions) is found instead of a power-law dependence. These discrepancies are explained from general principles of Hamiltonian dynamics. We discuss the implication of Hamiltonian properties in governing the paradigmatic "percolation" transport, characterized by $R\\to\\infty$, associating it with the concept of pseudochaos (random non-chaotic dynamics with zero Lyapunov exponents). Applications of this study pertain to both fusion and astrophysical plasma and by mathematical analogy to problems outside the plasma physics. This research article is dedicated to the memory of Professor George M. Zaslavsky

Alexander V. Milovanov; Rehab Bitane; Gaetano Zimbardo

2009-04-23T23:59:59.000Z

14

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

15

Recovering the Line-Of-Sight Magnetic Field in the Chromosphere from Ca II IR Spectra  

E-Print Network (OSTI)

We propose a method to derive the line-of-sight magnetic flux density from measurements in the chromospheric Ca II IR line at 854.2 nm. The method combines two well-understood techniques, the center-of-gravity and bisector methods, in a single hybrid technique. The technique is tested with magneto-static simulations of a flux tube. We apply the method to observations with the Interferometric Bidimensional Spectrometer (IBIS) installed at the Dunn Solar Telescope of the NSO/SP to investigate the morphology of the lower chromosphere, with focus on the chromospheric counterparts to the underlying photospheric magnetic flux elements.

Wöger, F; Uitenbroek, H; Rimmele, T

2009-01-01T23:59:59.000Z

16

EPRI Comments on a UK Case-Control Study of Magnetic Fields from High Voltage Power Lines and Childhood Cancer  

Science Conference Proceedings (OSTI)

A paper, entitled "Childhood cancer and magnetic fields from high voltage power lines in England and Wales: a case-control study," was published in the British Journal of Cancer on September 28, 2010. The authors assessed the association between exposure to EMF from power lines at the address of birth and childhood cancer. The current paper provides additional results to a study published earlier from the same data set in 2005. These EPRI comments provide an overview of study findings, conclusions, stren...

2010-12-22T23:59:59.000Z

17

Magnetically insulated transmission line oscillator  

DOE Patents (OSTI)

A magnetically insulated transmission line oscillator employs self-generated magnetic fields to generate microwave energy. An anode of the oscillator includes slow-wave structures which are formed of a plurality of thin conductive vanes defining cavities therebetween, and a gap is formed between the anode and a cathode of the oscillator. In response to a pulsed voltage applied to the anode and cathode, self-generated magnetic fields arfe produced in a cross-field orientation with respect to the orientation of the electric field between the anode and the cathode. The cross-field magnetic fields insulate the flow of electrons in the gap and confine the flow of electrons within the gap.

Bacon, Larry D. (Albuquerque, NM); Ballard, William P. (Albuquerque, NM); Clark, M. Collins (Albuquerque, NM); Marder, Barry M. (Albuquerque, NM)

1988-01-01T23:59:59.000Z

18

Magnetically insulated transmission line oscillator  

DOE Patents (OSTI)

A magnetically insulated transmission line oscillator employs self-generated magnetic fields to generate microwave energy. An anode of the oscillator includes slow-wave structures which are formed of a plurality of thin conductive vanes defining cavities therebetween, and a gap is formed between the anode and a cathode of the oscillator. In response to a pulsed voltage applied to the anode and cathode, self-generated magnetic fields are produced in a cross-field orientation with respect to the orientation of the electric field between the anode and the cathode. The cross-field magnetic fields insulate the flow of electrons in the gap and confine the flow of electrons within the gap. 11 figs.

Bacon, L.D.; Ballard, W.P.; Clark, M.C.; Marder, B.M.

1987-05-19T23:59:59.000Z

19

Survey of Magnetic Fields Near BPA 230-kV and 500-kV Transmission Lines.  

Science Conference Proceedings (OSTI)

The purpose of this study was to characterize typical levels and variability of 60Hz magnetic fields at the centerline and edge of right-of-way of Bonneville Power Administration (BPA) 230-kV and 500-kV transmission lines. This was accomplished by taking magnetic field measurements at over 800 spans in Oregon and Washington. The spans were sampled using a stratified random sampling procedure with region (East vs. West), voltage (230-kV vs 500-kV), and circuit configuration as strata. There were five different circuit configuration groups for each region/voltage category requiring a total of 200 strata. Magnetic field measurements were taken at 13 locations under each span using an EMDEX-C as a survey meter. Additional information recorded for each span included conductor height (at 10 locations), right-of-way width, longitudinal and lateral slope, time of day, vegetation, terrain, weather conditions, temperature, wind speed, span length and presence of other lines in the corridor. 9 refs., 17 figs., 26 tabs.

Perrin, Nancy; Aggarwal, Rajinder Pal; Bracken, T. Daniel

1991-05-20T23:59:59.000Z

20

Magnetic field exposure assessment for adult residents of Maine who live near and far away from overhead transmission lines  

Science Conference Proceedings (OSTI)

Sixty-Hz magnetic field exposures were measured for 45 adult residents of Maine. Thirty of the subjects resided near rights-of-way (ROWs) with either 345- and 115-kV transmission lines, or ROWs with only 115-kV transmission lines; fifteen resided far from any transmission lines. Personal exposure data for a single 24-hour period was acquired with the EMDEX. The EMDEX's event-marker button was used to partition exposures into Home and Away components. Also, three area measurements were taken for each subject during the personal exposure measurement period: (1) 24-hr fixed-site bedroom measurement with a second EMDEX; (2) Spot measurements in at least three rooms of every residence; and (3) Spot measurements outside each residence. Residence near transmission lines highly loaded during the measurement period was associated with increased Home and Total exposure relative to a far-away population. Average exposure level while away from home was uniform (at about 2 mG) throughout the study population. On a quantitative level, Home exposure was correlated equivalently with Spot-In (r = .70) and the 24-hr fixed site measurement (r = .68). Correlations of area measurements with Total exposure were weaker because of the dilution effect of Away exposure (r = .64 for Spot-In; r = .61 for 24-h Bedroom). Away and Home exposures were not correlated (r = .14), which reinforced our confidence that the participants used the EMDEX correctly. The data suggest the need for caution before inferences are drawn about total personal exposure from area measurements. The study demonstrates the feasibility of obtaining valid measures of magnetic-field exposure with the personal exposure monitors that have been developed.

Kavet, R.; Silva, J.M.; Thornton, D. (Enertech Consultants, Campbell, CA (United States))

1992-01-01T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic field lines" 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

Parallel transport of long mean-free-path plasma along open magnetic field lines: Parallel heat flux  

SciTech Connect

In a long mean-free-path plasma where temperature anisotropy can be sustained, the parallel heat flux has two components with one associated with the parallel thermal energy and the other the perpendicular thermal energy. Due to the large deviation of the distribution function from local Maxwellian in an open field line plasma with low collisionality, the conventional perturbative calculation of the parallel heat flux closure in its local or non-local form is no longer applicable. Here, a non-perturbative calculation is presented for a collisionless plasma in a two-dimensional flux expander bounded by absorbing walls. Specifically, closures of previously unfamiliar form are obtained for ions and electrons, which relate two distinct components of the species parallel heat flux to the lower order fluid moments such as density, parallel flow, parallel and perpendicular temperatures, and the field quantities such as the magnetic field strength and the electrostatic potential. The plasma source and boundary condition at the absorbing wall enter explicitly in the closure calculation. Although the closure calculation does not take into account wave-particle interactions, the results based on passing orbits from steady-state collisionless drift-kinetic equation show remarkable agreement with fully kinetic-Maxwell simulations. As an example of the physical implications of the theory, the parallel heat flux closures are found to predict a surprising observation in the kinetic-Maxwell simulation of the 2D magnetic flux expander problem, where the parallel heat flux of the parallel thermal energy flows from low to high parallel temperature region.

Guo Zehua; Tang Xianzhu [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2012-06-15T23:59:59.000Z

22

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

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

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

25

A Study On High Voltage AC Power Transmission Line Electric And Magnetic Field Coupling With Nearby Metallic Pipelines.  

E-Print Network (OSTI)

??In the recent years, there has been a trend to run metallic pipelines carrying petroleum products and high voltage AC power lines parallel to each… (more)

Gupta, Abhishek

2006-01-01T23:59:59.000Z

26

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

27

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

28

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

29

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

30

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

31

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

32

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

33

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

34

Magnetic Materials for Broadband Transmission Line  

E-Print Network (OSTI)

The author’s series of articles on broadband transmission line transformers (TLTs) concludes with these notes on magnetic materials and the properties that are important for best performance Ferrite and iron powder magnetic materials were developed to support a wide range of components, including inductors, EMI suppressors, conventional transformers and transmission line transformers (TLTs). This article deals with transmission line transformers, presenting the observations and conclusions of the author, reached after extensive experimental research into the behavior and performance of these devices in broadband applications. Figure 1 · The three transformers used in comparing the performance of the autotransformer and the transmission line transformer. At the top left is an autotransformer; at the top right is the transmission line transformer, while at the bottom is a transmission line transformer without a ferrite core. All transformers had a total of 10 turns.

Jerry Sevick

2005-01-01T23:59:59.000Z

35

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

36

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

37

Four cavity efficiency enhanced magnetically insulated line oscillator  

DOE Patents (OSTI)

This invention relates to magnetically insulated line oscillators (MILOs), and more particularly to a four cavity MILO that is ultra compact and displays enhanced efficiency as a result of the four cavity configuration that incorporates an RF choke and electron dump region to obtain high power microwaves with lower voltage requirements than typically required in the microwave field for gigawatt output from microwave sources.

Lemke, R.W.; Clark, M.C.; Calico, S.E.

1996-07-10T23:59:59.000Z

38

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

39

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

40

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

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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

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

42

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

43

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

44

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

45

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

46

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

47

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

48

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

49

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

50

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

51

Calculation of electric field and audible noise from transmission lines with non-parallel conductors  

Science Conference Proceedings (OSTI)

In order to investigate the feasibility of using new transmission line configurations with non-parallel conductors, for managing magnetic field in critical areas, techniques are needed to assess the effects of different three-dimensional line arrangements on other important design parameters. A new method for calculation of electric field and corona-generated audible noise from non-parallel conductors is described and implemented as a computer tool. This method uses linearly varying line charges to simulate charge distribution along the axial direction of the transmission line. New algorithms are developed for calculating electric field and audible noise due to non-uniform line charges and illustrated by examples of low magnetic field transmission line designs.

Liu, Y. [Virginia Tech, Blacksburg, VA (United States); Zaffanella, L.E. [Enertech Consultants, Lee, MA (United States)

1996-07-01T23:59:59.000Z

52

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

53

A test of a 2 Tesla superconducting transmission line magnet system  

Science Conference Proceedings (OSTI)

Superconducting transmission line magnet test system for an injector accelerator of a staged VLHC proton-proton colliding beam accelerator has been built and operated at Fermilab. The 1.5 m long, twin-aperture, combined function dipole magnet of 2 Tesla field is excited by a single turn 100 kA transmission line superconductor. The 100 kA dc current is generated using dc-dc switching converters powered by a bulk 240 kW supply. A pair of horizontally placed conventional leads facilitates transfer of this current to the magnet transmission line superconductor operating at liquid helium temperature. Fabrication of magnet components and magnet assembly work are described. The magnet test system and its operation are presented, and the performance is summarized.

Piekarz, Henryk; Carcagno, Ruben; Claypool, Brad; Foster, George W.; Hays, Steven L.; Huang, Yuenian; Kashikhin, Vladimir; Malamud, Ernest; Mazur, Peter O.; Nehring, Roger; Oleck, Andrew; Rabehl, Roger; Schlabach, Phil; Sylvester, Cosmore; Velev, Gueorgui; Volk, James; /Fermilab; Wake, Masayoshi; /KEK, Tsukuba

2005-09-01T23:59:59.000Z

54

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

55

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

56

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

57

Magnetic and electric field testing of the Amtrak Northeast Corridor and New Jersey transit/North Jersey coast line rail systems. Volume 2. Appendices. Final report, May 1993-March 1993  

Science Conference Proceedings (OSTI)

The safety of magnetically levitated (maglev) and high speed rail (HSR) trains proposed for application in the United States is the responsibility of the Federal Railroad Administration (FRA). The characterization of electric and magnetic fields (EMF) produced by both steady (dc) and alternating currents (ac) at power frequency (50 Hz in Europe and 60 Hz in the U.S.) and above, in the Extreme Low Frequency (ELF) range (3-3000 Hz), is of interest with respect to any potential health effects these fields may have on the public and on transportation workers. An EMF survey of National Rail Passengers Corporation trains operating on the Northeast Corridor (NEC) was performed, as part of a comprehensive comparative safety assessment of the German Transrapid (TR-07) maglev system and of existing (NEC and transit trains) and advanced rail systems (the French TGV). The report is Volume 2 of two volumes. A portable magnetic field monitoring system (augmented to include an electric fields probe) was used to sample, record and store three-axis static and ac magnetic fields waveforms simultaneously, at multiple locations. A real time Digital Audio Tape (DAT) recorder able to capture EMF transients, and two personal power-frequency magnetic field monitors were used to collect complementary data.

Dietrich, F.M.; Robertson, D.C.; Steiner, G.A.

1993-04-01T23:59:59.000Z

58

Magnetic and electric field testing of the Amtrak Northeast Corridor and New Jersey Transit/North Jersey coast line rail systems. Volume 1. Analysis. Final report, May 1992-March 1992  

Science Conference Proceedings (OSTI)

The safety of magnetically levitated (maglev) and high speed rail (HSR) trains proposed for application in the United States is the responsibility of the Federal Railroad Administration (FRA). The characterization of electric and magnetic fields (EMF) produced by both steady (dc) and alternating currents (ac) at power frequency (50 Hz in Europe and 60 Hz in the U.S.) and above, in the Extreme Low Frequency (ELF) range (3-3000 Hz), is of interest with respect to any potential health effects these fields may have on the public and on transportation workers. An EMF survey of National Rail Passengers Corporation trains operating on the Northeast Corridor (NEC) was performed, as part of a comprehensive comparative safety assessment of the German Transrapid (TR-07) maglev system, and of existing (NEC and transit trains) and advanced rail systems (the French TGV). The report is Volume 1 of two volumes. A portable magnetic field monitoring system (augmented to include an electric fields probe) was used to sample, record and store three-axis static and ac magnetic fields waveforms simultaneously, at multiple locations. A real time Digital Audio Tape (DAT) recorder able to capture EMF transients, and two personal power-frequency magnetic field monitors were used to collect complementary data.

Dietrich, F.M.; Feero, W.E.; Papas, P.N.; Steiner, G.A.

1993-04-01T23:59:59.000Z

59

Electron flow stability in magnetically insulated vacuum transmission lines.  

Science Conference Proceedings (OSTI)

We evaluate the stability of electron current flow in high-power magnetically insulated transmission lines (MITLs). A detailed model of electron flow in cross-field gaps yields a dispersion relation for electromagnetic (EM) transverse magnetic waves [R. C. Davidson et al., Phys. Fluids 27, 2332 (1984)] which is solved numerically to obtain growth rates for unstable modes in various sheath profiles. These results are compared with two-dimensional (2D) EM particle-in-cell (PIC) simulations of electron flow in high-power MITLs. We find that the macroscopic properties (charge and current densities and self-fields) of the equilibrium profiles observed in the simulations are well represented by the laminar-flow model of Davidson et al. Idealized simulations of sheared flow in electron sheaths yield growth rates for both long (diocotron) and short (magnetron) wavelength instabilities that are in good agreement with the dispersion analysis. We conclude that electron sheaths that evolve self-consistently from space-charged-limited emission of electrons from the cathode in well-resolved 2D EM PIC simulations form stable profiles.

Genoni, Thomas C. (Voss Scientific, LLC, Albuquerque, NM); Stygar, William A.; Welch, Dale Robert (Voss Scientific, LLC, Albuquerque, NM); Clark, R. E. (Voss Scientific, LLC, Albuquerque, NM); Rose, David V. (Voss Scientific, LLC, Albuquerque, NM)

2010-11-01T23:59:59.000Z

60

Investigating Magnetic Field Lines Project Overview  

E-Print Network (OSTI)

. How did various sub-populations of students perform? Consider factors such as gender, race, socio of properties and changes of properties in matter. · Transfer of energy Content Standard E: Science-12, all students should develop an understanding of motions and forces. · Conservation of energy

Weston, Ken

Note: This page contains sample records for the topic "magnetic field lines" 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

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

62

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

63

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

64

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

65

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

66

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

67

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

68

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

69

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

70

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

71

Measurements of a crenelated iron pole tip for the VLHC transmission line magnet  

E-Print Network (OSTI)

The Very Large Hadron Collider (VLHC) is under conceptual design in Fermilab. One option under development is a 2-Tesla warm iron 2-in-1 single turn superferric magnet built around an 80 kA superconducting transmission line. A normal-conducting test stand was built to optimize the iron lamination shape for this magnet. It uses a water- cooled copper winding to provide the 100 kA-turns needed to generate 2 Tesla fields in both 20 mm air gaps of the magnet. A magnetic measurement facility has been set up for magnetic field mapping, which includes a flat measurement coil, precision stage for coil motion and integrator. Results from a first test of the "crenelation" technique to mitigate the saturation sextupole in iron magnets are described and future plans are discussed. (5 refs).

Di Marco, J; Kashikhin, V V; Makarov, A A; Schlabach, P; MacKay, W W

1999-01-01T23:59:59.000Z

72

THE ABRUPT CHANGES IN THE PHOTOSPHERIC MAGNETIC AND LORENTZ FORCE VECTORS DURING SIX MAJOR NEUTRAL-LINE FLARES  

SciTech Connect

We analyze the spatial and temporal variations of the abrupt photospheric magnetic changes associated with six major flares using 12 minute, 0.''5 pixel{sup -1} vector magnetograms from NASA's Helioseismic and Magnetic Imager instrument on the Solar Dynamics Observatory satellite. The six major flares occurred near the main magnetic neutral lines of four active regions, NOAA 11158, 11166, 11283, and 11429. During all six flares the neutral-line field vectors became stronger and more horizontal, in each case almost entirely due to strengthening of the horizontal field components parallel to the neutral line. In all six cases the neutral-line pre-flare fields were more vertical than the reference potential fields, and collapsed abruptly and permanently closer to potential-field tilt angles during every flare, implying that the relaxation of magnetic stress associated with non-potential tilt angles plays a major role during major flares. The shear angle with respect to the reference potential field did not show such a pattern, demonstrating that flare processes do not generally relieve magnetic stresses associated with photospheric magnetic shear. The horizontal fields became significantly and permanently more aligned with the neutral line during the four largest flares, suggesting that the collapsing field is on average more aligned with the neutral line than the pre-flare neutral-line field. The vertical Lorentz force had a large, abrupt, permanent downward change during each of the flares, consistent with loop collapse. The horizontal Lorentz force changes acted mostly parallel to the neutral line in opposite directions on each side, a signature of the fields contracting during the flare, pulling the two sides of the neutral line toward each other. The greater effect of the flares on field tilt than on shear may be explained by photospheric line-tying.

Petrie, G. J. D. [National Solar Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)

2012-11-01T23:59:59.000Z

73

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

74

Spectral Line Shapes as a Diagnostic Tool in Magnetic Fusion  

DOE Green Energy (OSTI)

Spectral line shapes and intensities are used for obtaining information on the various regions of magnetic fusion devices. Emission from low principal quantum numbers of hydrogen isotopes is analyzed for understanding the complex recycling mechanism. Lines emitted from high principal quantum numbers of hydrogen and helium are dominated by Stark effect, allowing an electronic density diagnostic in the divertor. Intensities of lines emitted by impurities are fitted for a better knowledge of ion transport in the confined plasma.

Stamm, R; Capes, H; Demura, A; Godbert-Mouret, L; Koubiti, M; Marandet, Y; Mattioli, M; Rosato, J; Rosmej, F; Fournier, K B

2006-07-22T23:59:59.000Z

75

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

76

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

77

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

78

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

79

Depinning of flux lines and AC losses in magnet-superconductor levitation system  

DOE Green Energy (OSTI)

The AC loss characteristics of a magnet-superconductor system were studied with the magnet fixed to the free end of an oscillating cantilever located near a stationary melt-textured YBCO pellet. Below a threshold AC field amplitude {approx}2Oe, the dissipation of the oscillator is amplitude-independent, characteristic of a linear, non-hysteretic regime. Above threshold,dissipation increases with amplitude, reflecting the depinning and hysteretic motion of flux lines. The threshold AC field is an order of magnitude higher than that measured for the same YBCO material via AC susceptometry in a uniform DC magnetic field, A partial lock-in of flux lines between YBCO ab planes is proposed as the mechanism for the substantial increase of the depinning threshold.

Terentiev, A. N.; Hull, J. R.; De Long, L. E.

1999-11-29T23:59:59.000Z

80

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

Note: This page contains sample records for the topic "magnetic field lines" 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

Controlled generation of field squeezing with cold atomic clouds coupled to a superconducting transmission line resonator  

E-Print Network (OSTI)

We propose an efficient method for controlled generation of field squeezing with cold atomic clouds trapped close to a superconducting transmission line resonator. It is shown that, based on the coherent strong magnetic coupling between the collective atomic spins and microwave fields in the transmission line resonator, two-mode or single mode field squeezed states can be generated through coherent control on the dynamics of the system. The degree of squeezing and preparing time can be directly controlled through tuning the external classical fields. This protocol may offer a promising platform for implementing scalable on-chip quantum information processing with continuous variables.

Li, Peng-Bo

2010-01-01T23:59:59.000Z

82

Controlled generation of field squeezing with cold atomic clouds coupled to a superconducting transmission line resonator  

E-Print Network (OSTI)

We propose an efficient method for controlled generation of field squeezing with cold atomic clouds trapped close to a superconducting transmission line resonator. It is shown that, based on the coherent strong magnetic coupling between the collective atomic spins and microwave fields in the transmission line resonator, two-mode or single mode field squeezed states can be generated through coherent control on the dynamics of the system. The degree of squeezing and preparing time can be directly controlled through tuning the external classical fields. This protocol may offer a promising platform for implementing scalable on-chip quantum information processing with continuous variables.

Peng-Bo Li; Fu-Li Li

2010-02-26T23:59:59.000Z

83

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

84

Design Considerations of Fast-cycling Synchrotrons Based on Superconducting Transmission Line Magnets  

E-Print Network (OSTI)

Design Considerations of Fast-cycling Synchrotrons Based on Superconducting Transmission Line Magnets

Piekarz, H; Huang, Y; Shiltsev, V

2008-01-01T23:59:59.000Z

85

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

86

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

87

SQUID-Detected NMR and MRI at Ultralow Magnetic Fields  

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

88

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

89

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

90

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

91

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

92

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

93

Imaging vector fields using Line Integral Convolution  

SciTech Connect

Imaging vector fields has applications in science, art, image processing and special effects. An effective new approach is to use linear and curvilinear filtering techniques to locally blur textures along a vector field. This approach builds on several previous texture generation and filtering techniques. It is, however, unique because it is local, one-dimensional and independent of any predefined geometry or texture. The technique is general and capable of imaging arbitrary two- and three-dimensional vector fields. The local one-dimensional nature of the algorithm lends itself to highly parallel and efficient implementations. Furthermore, the curvilinear filter is capable of rendering detail on very intricate vector fields. Combining this technique with other rendering and image processing techniques -- like periodic motion filtering -- results in richly informative and striking images. The technique can also produce novel special effects.

Cabral, B.; Leedom, L.C.

1993-03-01T23:59:59.000Z

94

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

95

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

96

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

97

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

98

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

99

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

100

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.

Note: This page contains sample records for the topic "magnetic field lines" 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

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

102

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

103

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

104

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

105

Probability Density Functions to Represent Magnetic Fields at the Solar Surface  

E-Print Network (OSTI)

Numerical simulations of magneto-convection and analysis of solar magnetogram data provide empirical probability density functions (PDFs) for the line-of-sight component of the magnetic field. In this paper, we theoretically explore effects of several types of PDFs on polarized Zeeman line formation. We also propose composite PDFs to account for randomness in both field strength and orientation. Such PDFs can possibly mimic random fields at the solar surface.

Sampoorna, M

2009-01-01T23:59:59.000Z

106

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

107

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

108

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

109

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

110

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

111

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

112

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

113

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

114

Electric and Magnetic Screening Masses at Finite Temperature from Generalized Polyakov-Line Correlations in Two-flavor Lattice QCD  

E-Print Network (OSTI)

Screenings of the quark-gluon plasma in electric and magnetic sectors are studied on the basis of generalized Polyakov-line correlation functions in lattice QCD simulations with two flavors of improved Wilson quarks. Using the Euclidean-time reflection ($\\R$) and the charge conjugation ($\\Ca$), electric and magnetic screening masses are extracted in a gauge invariant manner. Long distance behavior of the standard Polyakov-line correlation in the quark-gluon plasma is found to be dictated by the magnetic screening. Also, ratio of the two screening masses agrees with that obtained from the dimensionally-reduced effective field theory and the ${\\cal N}=4$ supersymmetric Yang-Mills theory.

Y. Maezawa; S. Aoki; S. Ejiri; T. Hatsuda; N. Ishii; K. Kanaya; N. Ukita; T. Umeda

2010-03-06T23:59:59.000Z

115

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

116

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

117

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

118

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

119

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.

120

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

Note: This page contains sample records for the topic "magnetic field lines" 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

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,...

122

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

123

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

124

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

125

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

126

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

127

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

128

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

129

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

130

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

131

Exposure to transmission line electric fields during farming operations  

Science Conference Proceedings (OSTI)

This paper describes an analysis of exposure to transmission line electric fields during typical farming operations. This analysis makes use of experimentally determined ''activity factors'' and time budget information for typical farms as compiled by the U.S. Department of Agriculture. A detailed exposure assessment for 18 ''typical farms'' (as defined by USDA) is provided for a base case 345 kV design. Exposure estimates for transmission lines ranging from 115-765 kV are provided for a representative farm.

Silva, M.; Huber, D.

1985-09-01T23:59:59.000Z

132

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

133

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

134

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 ...

135

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

136

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...

137

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

138

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.

139

Four cavity efficiency enhanced magnetically insulated line oscillator  

SciTech Connect

A four cavity, efficient magnetically insulated line oscillator (C4-E MILO) having seven vanes and six cavities formed within a tube-like structure surrounding a cathode. The C4-E MILO has a primary slow wave structure which is comprised of four vanes and the four cavities located near a microwave exit end of the tube-like structure. The primary slow wave structure is the four cavity (C4) portion of the magnetically insulated line oscillator (MILO). An RF choke is provided which is comprised of three of the vanes and two of the cavities. The RF choke is located near a pulsed power source portion of the tube-like structure surrounding the cathode. The RF choke increases feedback in the primary slow wave structure, prevents microwaves generated in the primary slow wave structure from propagating towards the pulsed power source and modifies downstream electron current so as to enhance microwave power generation. A beam dump/extractor is located at the exit end of the oscillator tube for extracting microwave power from the oscillator, and in conjunction with an RF extractor vane, which comprises the fourth vane of the primary slow wave structure (nearest the exit) having a larger gap radius than the other vanes of the primary SWS, comprises an RF extractor. Uninsulated electron flow is returned downstream towards the exit along an anode/beam dump region located between the beam dump/extractor and the exit where the RF is radiated at said RF extractor vane located near the exit and the uninsulated electron flow is disposed at the beam dump/extractor.

Lemke, Raymond W. (Albuquerque, NM); Clark, Miles C. (Albuquerque, NM); Calico, Steve E. (Albuquerque, NM)

1998-04-21T23:59:59.000Z

140

Four cavity efficiency enhanced magnetically insulated line oscillator  

DOE Patents (OSTI)

A four cavity, efficient magnetically insulated line oscillator (C4-E MILO) having seven vanes and six cavities formed within a tube-like structure surrounding a cathode is disclosed. The C4-E MILO has a primary slow wave structure which is comprised of four vanes and the four cavities located near a microwave exit end of the tube-like structure. The primary slow wave structure is the four cavity portion of the magnetically insulated line oscillator (MILO). An RF choke is provided which is comprised of three of the vanes and two of the cavities. The RF choke is located near a pulsed power source portion of the tube-like structure surrounding the cathode. The RF choke increases feedback in the primary slow wave structure, prevents microwaves generated in the primary slow wave structure from propagating towards the pulsed power source and modifies downstream electron current so as to enhance microwave power generation. A beam dump/extractor is located at the exit end of the oscillator tube for extracting microwave power from the oscillator, and in conjunction with an RF extractor vane, which comprises the fourth vane of the primary slow wave structure (nearest the exit) having a larger gap radius than the other vanes of the primary SWS, comprises an RF extractor. Uninsulated electron flow is returned downstream towards the exit along an anode/beam dump region located between the beam dump/extractor and the exit where the RF is radiated at said RF extractor vane located near the exit and the uninsulated electron flow is disposed at the beam dump/extractor. 34 figs.

Lemke, R.W.; Clark, M.C.; Calico, S.E.

1998-04-21T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic field lines" 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

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

142

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

143

Field Guide: Inspection of Transmission Line Grounding Systems  

Science Conference Proceedings (OSTI)

This EPRI report, one in a series of practical guides designed as reference aids for utility personnel working in the field, visually catalogs the various condition issues that commonly affect transmission line grounding systems. It presents photographs and short written descriptions of the conditions and lists associated causes, failure modes, and impacts.The downloadable PDF for this product is optimized for viewing on electronic devices such as tablets. For Android devices, Adobe ...

2013-11-25T23:59:59.000Z

144

Gas insulated transmission line with insulators having field controlling recesses  

DOE Patents (OSTI)

A gas insulated transmission line having a novel insulator for supporting an inner conductor concentrically within an outer sheath. The insulator has a recess contiguous with the periphery of one of the outer and inner conductors. The recess is disposed to a depth equal to an optimum gap for the dielectric insulating fluid used for the high voltage insulation or alternately disposed to a large depth so as to reduce the field at the critical conductor/insulator interface.

Cookson, Alan H. (Pittsburgh, PA); Pederson, Bjorn O. (Chelmsford, MA)

1984-01-01T23:59:59.000Z

145

Field Guide: Inspection of Transmission Line Grounding Systems (Standard PDF)  

Science Conference Proceedings (OSTI)

This EPRI report, one in a series of practical guides designed as reference aids for utility personnel working in the field, visually catalogs the various condition issues that commonly affect transmission line grounding systems. It presents photographs and short written descriptions of the conditions and lists associated causes, failure modes, and impacts. The guide is printed in color on high-quality paper and is ring-bound. It is therefore recommended that members order printed copies rather than ...

2012-11-06T23:59:59.000Z

146

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

147

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

148

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

149

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

150

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

151

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.

152

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.

153

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.

154

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

155

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

156

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

157

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

158

A Holographic Quantum Critical Point at Finite Magnetic Field and Finite Density  

E-Print Network (OSTI)

We analyze the phase diagram of N=4 supersymmetric Yang-Mills theory with fundamental matter in the presence of a background magnetic field and nonzero baryon number. We identify an isolated quantum critical point separating two differently ordered finite density phases. The ingredients that give rise to this transition are generic in a holographic setup, leading us to conjecture that such critical points should be rather common. In this case, the quantum phase transition is second order with mean-field exponents. We characterize the neighborhood of the critical point at small temperatures and identify some signatures of a new phase dominated by the critical point. We also identify the line of transitions between the finite density and zero density phases. The line is completely determined by the mass of the lightest charged quasiparticle at zero density. Finally, we measure the magnetic susceptibility and find hints of fermion condensation at large magnetic field.

Kristan Jensen; Andreas Karch; Ethan G. Thompson

2010-02-11T23:59:59.000Z

159

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

160

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 ...

Note: This page contains sample records for the topic "magnetic field lines" 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.
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161

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

162

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

163

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

164

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

165

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

166

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

167

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

168

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

169

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

170

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

171

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

172

The Velocity Field of Quasar Broad Emission Line Gas  

E-Print Network (OSTI)

In this Letter, the broad emission line (BEL) profiles of superluminal quasars with apparent jet velocities, $\\beta_{a}>10$, (ultraluminal QSOs, or ULQSOs hereafter) are studied as a diagnostic of the velocity field of the BEL emitting gas in quasars. The ULQSOs are useful because they satisfy a very strict kinematical constraint, their parsec scale jets must be propagating within $12^{\\circ}$ of the line of sight. We know the orientation of these objects with great certainty. The large BEL FWHM, $\\sim 3,000 \\mathrm{km/s} - 6,000 \\mathrm{km/s}$, in ULQSOs tend to indicate that the BEL gas has a larger component of axial velocity (either random or in a wind) along the jet direction than previously thought.

Brian Punsly

2007-01-25T23:59:59.000Z

173

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

174

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.

175

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

176

Electro Acceleration in a Geomagnetic Field Line Resonance  

Science Conference Proceedings (OSTI)

A hybrid MHD kinetic electron model in dipolar coordinates is used to sim- ulate the upward current region of a geomagnetic Field Line Resonance (FLR) system for a realistic ambient electron temperatures of a keV. It is found that mirror force e ects result in potential drops su#14;cient to accelerate electrons to energies in excess of a keV in support of eld aligned currents on the or- der of 0.5 #22;µA/m2. The wave energy dissipated in this acceleration would com- pletely damp an undriven FLR with an equatorial width of 0.5 RE within two resonance cycles.

Peter Damiano and J.R. Johnson

2012-08-17T23:59:59.000Z

177

Construction of Superconducting Magnet System for the J-PARC Neutrino Beam Line  

Science Conference Proceedings (OSTI)

Following success of a prototype R&D, construction of a superconducting magnet system for J-PARC neutrino beam line has been carried out since 2005. A new conceptual beam line with the superconducting combined function magnets demonstrated the successful beam transport to the neutrino production target.

Nakamoto, T.; Wanderer, P.; Sasaki, K.; Ajima, Y.; Araoka, O.; Fujii, Y.; Hastings, N.; Higashi, N.; Iida, M.; Ishii, T.; Kimura, N.; Kobayashi, T.; Makida, Y.; Nakadaira, T.; Ogitsu, T.; Ohhata, H.; Okamura, T.; Sakashita, K.; Sugawara, S.; Suzuki, S.; Tanaka, K.; Tomaru, T.; Terashima, A.; Yamamoto, A.; Ichikawa, A.; Kakuno, H.; Anerella, M.; Escallier, J.; Ganetis, G.; gupta, R.; Jain, A.; Muratore, J.; Parker, B.; Boussuge, T.; Charrier, J.-P.; Arakawa, M.; Ichihara, T.; Minato, T.; Okada, Y.; Itou, A.; Kumaki, T.; Nagami, M.; Takahashi, T.

2009-10-18T23:59:59.000Z

178

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

179

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

180

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

Note: This page contains sample records for the topic "magnetic field lines" 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

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

182

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

183

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

184

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

185

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

186

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

187

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

188

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

189

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

190

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

191

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.

192

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

193

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

194

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

195

RAYLEIGH-TAYLOR INSTABILITIES OF A COLLAPSING CYLINDRICAL SHELL IN A MAGNETIC FIELD  

SciTech Connect

The instability of a radially accelerated cylindrical shell in a magnetic field has been investigated. It was assumed thai the shell was of infinitesimal thickness. For perturbations which do not bend the lines of the magnetic field, the growth rate was found to be w= (gk)/sup 1/2/, where g is the acceleration of the shell and k is the wavenumber. This growth rate is independent of the shell thickness. Perturbations which do bend the lines of the field were also found to be unstable. From a supplementary calculation, it was concluded that these instabilities were effective only for wavelengths greater than 8 pi a where 2a is the shell thickness. (auth)

Harris, E.G.

1962-09-01T23:59:59.000Z

196

Nuclear magnetic flowmeter -- Spectrometer with fiber -optical communication line in cooling systems of atomic energy plants  

Science Conference Proceedings (OSTI)

Fiber-optic communication line for transmitting a signal of nuclear magnetic resonance of liquid medium in the ship's central computer was developed. This fiber-optic communication line allows us to give an NMR signal in digital or analog form without ... Keywords: FOCL transmission coefficient, Fiber optic communication line (FOCL), communication system, optical converter, optical modulator

V. V. Davydov; V. I. Dudkin; A. U. Karseev

2013-04-01T23:59:59.000Z

197

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

198

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

199

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

200

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

Note: This page contains sample records for the topic "magnetic field lines" 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.


201

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

202

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

203

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

204

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

205

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

206

An Energy-Stabilized Varied-Line-Space-Monochromator UndulatorBeam Line for PEEM Illumination and Magnetic Circular Dichroism  

Science Conference Proceedings (OSTI)

A new undulator beam line has been built and commissioned at the Advanced Light Source for illumination of the PEEM3 microscope. The beam line delivers high flux beams over an energy range from C1s through the transition metals to include the M edges of the magnetic rare earth elements. We present details of the optical design, and data on the performance of the zero-order tracking of the photon energy.

Warwick, Tony; McKinney, Wayne; Domning, Ed; Doran, Andrew; Padmore, Howard

2006-06-01T23:59:59.000Z

207

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

208

Induced vacuum current and magnetic field in the background of a cosmic string  

E-Print Network (OSTI)

Vacuum polarization effects in the cosmic string background are considered. We find that a current is induced in the vacuum of the quantized massive scalar field and that the current circulates around the string which is generalized to a $(d-2)$-brane in locally flat $(d+1)$-dimensional space-time. As a consequence of the Maxwell equation, a magnetic field strength is also induced in the vacuum and is directed along the cosmic string. The dependence of the current and the field strength on the string flux and tension is comprehensively analyzed. Both the current and the field strength are holomorphic functions of the space dimension, decreasing exponentially with the distance from the string. In the case of $d=3$ we show that, due to the vacuum polarization, the cosmic string is enclosed in a tube of the magnetic flux lines if the mass of the quantized field is less than the inverse of the transverse size of the string core.

Yu. A. Sitenko; N. D. Vlasii

2009-09-02T23:59:59.000Z

209

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)

210

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

211

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

212

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

213

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

214

Material Shielding of Power Frequency Magnetic Fields: Research and Testing Results from the EPRI Power Delivery Center -- Lenox  

Science Conference Proceedings (OSTI)

Magnetic fields from power lines and other electrical facilities can interfere with sensitive electronic equipment such as computers, electron microscopes, medical diagnostic and monitoring equipment, and air traffic control displays. Shields can be designed to reduce the magnetic field strength in the areas of interest, but attention must be given to certain aspects of shield design. This report deals with three aspects of practical shield construction: flat sheet dimensions, joining sheets, and thin co...

1998-06-29T23:59:59.000Z

215

Discovery of the magnetic field in the pulsating B star beta Cephei  

E-Print Network (OSTI)

Although the star itself is not He enriched, the periodicity and the variability in the UV wind lines of the pulsating B1 IV star beta Cep are similar to what is observed in magnetic He-peculiar B stars, suggesting that beta Cep is magnetic. We searched for a magnetic field using spectropolarimetry. From UV spectroscopy, we analysed the wind variability and investigated the correlation with the magnetic data. Using 130 time-resolved circular polarisation spectra, obtained with the MuSiCoS spectropolarimeter at the 2m TBL from 1998 until 2005, we applied the least-squares deconvolution method on the Stokes V spectra and derived the longitudinal component of the integrated magnetic field over the visible hemisphere of the star. We performed a period analysis on the magnetic data and on EW measurements of UV wind lines obtained over 17 years. We also analysed the short- and long-term radial velocity variations, which are due to the pulsations and the 90-year binary motion. beta Cep hosts a sinusoidally varying m...

Henrichs, H F; Verdugo, E; Schnerr, R S; Neiner, C; Donati, J -F; Catala, C; Shorlin, S L S; Wade, G A; Veen, P M; Nichols, J S; Damen, E M F; Talavera, A; Hill, G M; Kaper, L; Tijani, A M; Geers, V C; Wiersema, K; Plaggenborg, B; Rygl, K L J

2013-01-01T23:59:59.000Z

216

NONLINEAR FORCE-FREE MAGNETIC FIELD FITTING TO CORONAL LOOPS WITH AND WITHOUT STEREOSCOPY  

SciTech Connect

We developed a new nonlinear force-free magnetic field (NLFFF) forward-fitting algorithm based on an analytical approximation of force-free and divergence-free NLFFF solutions, which requires as input a line-of-sight magnetogram and traced two-dimensional (2D) loop coordinates of coronal loops only, in contrast to stereoscopically triangulated three-dimensional loop coordinates used in previous studies. Test results of simulated magnetic configurations and from four active regions observed with STEREO demonstrate that NLFFF solutions can be fitted with equal accuracy with or without stereoscopy, which relinquishes the necessity of STEREO data for magnetic modeling of active regions (on the solar disk). The 2D loop tracing method achieves a 2D misalignment of {mu}{sub 2} = 2. Degree-Sign 7 {+-} 1. Degree-Sign 3 between the model field lines and observed loops, and an accuracy of Almost-Equal-To 1.0% for the magnetic energy or free magnetic energy ratio. The three times higher spatial resolution of TRACE or SDO/AIA (compared with STEREO) also yields a proportionally smaller misalignment angle between model fit and observations. Visual/manual loop tracings are found to produce more accurate magnetic model fits than automated tracing algorithms. The computation time of the new forward-fitting code amounts to a few minutes per active region.

Aschwanden, Markus J., 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)

2013-02-15T23:59:59.000Z

217

CALIBRATING 100 YEARS OF POLAR FACULAE MEASUREMENTS: IMPLICATIONS FOR THE EVOLUTION OF THE HELIOSPHERIC MAGNETIC FIELD  

Science Conference Proceedings (OSTI)

Although the Sun's polar magnetic fields are thought to provide important clues for understanding the 11 year sunspot cycle, including the observed variations of its amplitude and period, the current database of high-quality polar field measurements spans relatively few sunspot cycles. In this paper, we address this deficiency by consolidating Mount Wilson Observatory polar faculae data from four data reduction campaigns, validating it through a comparison with facular data counted automatically from Michelson Doppler Imager (MDI) intensitygrams, and calibrating it against polar field measurements taken by the Wilcox Solar Observatory and average polar field and total polar flux calculated using MDI line-of-sight magnetograms. Our results show that the consolidated polar facular measurements are in excellent agreement with both polar field and polar flux estimates, making them an ideal proxy to study the evolution of the polar magnetic field. Additionally, we combine this database with sunspot area measurements to study the role of the polar magnetic flux in the evolution of the heliospheric magnetic field (HMF). We find that there is a strong correlation between HMF and polar flux at solar minimum and that, taken together, polar flux and sunspot area are better at explaining the evolution of the HMF during the last century than sunspot area alone.

Munoz-Jaramillo, Andres; DeLuca, Edward E. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Sheeley, Neil R. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Zhang, Jie, E-mail: amunoz@cfa.harvard.edu, E-mail: edeluca@cfa.harvard.edu, E-mail: neil.sheeley@nrl.navy.mil, E-mail: jzhang7@gmu.edu [School of Physics, Astronomy and Computational Sciences, George Mason University, Fairfax, VA 22030 (United States)

2012-07-10T23:59:59.000Z

218

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

219

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

220

MAGNETIC FIELD STRUCTURE OF THE LARGE MAGELLANIC CLOUD FROM FARADAY ROTATION MEASURES OF DIFFUSE POLARIZED EMISSION  

Science Conference Proceedings (OSTI)

We present a study of the magnetic field of the Large Magellanic Cloud (LMC), carried out using diffuse polarized synchrotron emission data at 1.4 GHz acquired at the Parkes Radio Telescope and the Australia Telescope Compact Array. The observed diffuse polarized emission is likely to originate above the LMC disk on the near side of the galaxy. Consistent negative rotation measures (RMs) derived from the diffuse emission indicate that the line-of-sight magnetic field in the LMC's near-side halo is directed coherently away from us. In combination with RMs of extragalactic sources that lie behind the galaxy, we show that the LMC's large-scale magnetic field is likely to be of quadrupolar geometry, consistent with the prediction of dynamo theory. On smaller scales, we identify two brightly polarized filaments southeast of the LMC, associated with neutral hydrogen arms. The filaments' magnetic field potentially aligns with the direction toward the Small Magellanic Cloud (SMC). We suggest that tidal interactions between the SMC and the LMC in the past 10{sup 9} years are likely to have shaped the magnetic field in these filaments.

Mao, S. A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); McClure-Griffiths, N. M.; McConnell, D. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, Epping, NSW 1710 (Australia); Gaensler, B. M. [Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia); Haverkorn, M. [Department of Astrophysics, Radboud University, P.O. Box 9010, 6500-GL Nijmegen (Netherlands); Beck, R. [Max-Planck-Institut fuer Radioastronomie, D-53121 Bonn (Germany); Wolleben, M. [Square Kilometre Array South Africa, The Park, Pinelands 7405 (South Africa); Stanimirovic, S. [Department of Astronomy, University of Wisconsin, Madison, WI 53706 (United States); Dickey, J. M. [Physics Department, University of Tasmania, Hobart, TAS 7001 (Australia); Staveley-Smith, L., E-mail: mao@astro.wisc.edu [International Centre for Radio Astronomy Research (ICRAR), The University of Western Australia, Crawley, WA 6009 (Australia)

2012-11-01T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic field lines" 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

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

222

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

223

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

224

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

225

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

226

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

227

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

228

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

229

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

230

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

231

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

232

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

233

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

234

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

235

Uncertainties in field-line tracing in the magnetosphere. Part I: the axisymmetric part of the internal geomagnetic field  

E-Print Network (OSTI)

of the internal geomagnetic field D. M. Willis1;3, J. Robin Singh1;2 , Jacqueline Comer1;2 1 Rutherford Appleton in the specification of the geomagnetic field of internal origin. Because of the complexity in computing the axisymmetric part of the internal geomagnetic field. An exact analytic equation exists for the magnetic field

Paris-Sud XI, Université de

236

Probing the Magnetic Field at Sub-Parsec Radii in the Accretion Disk of NGC 4258  

E-Print Network (OSTI)

We present an analysis of polarimetric observations at 22 GHz of the water vapor masers in NGC 4258 obtained with the VLA and the GBT. We do not detect any circular polarization in the spectrum indicative of Zeeman-induced splitting of the maser lines of water, a non-paramagnetic molecule. We have improved the 1-sigma upper limit estimate on the toroidal component of the magnetic field in the circumnuclear disk of NGC 4258 at a radius of 0.2 pc from 300 mG to 90 mG. We have developed a new method for the analysis of spectra with blended features and derive a 1-sigma upper limit of 30 mG on the radial component of the magnetic field at a radius of 0.14 pc. Assuming thermal and magnetic pressure balance, we estimate an upper limit on the mass accretion rate of ~10^(-3.7) M_sun/yr for a total magnetic field of less than 130 mG. We discuss the ramifications of our results on current maser models proposed to explain the observed maser emission structure and the consequences for current accretion theories. We find from our magnetic field limits that the thin-disk model and the jet-disk model are better candidates for accounting for the extremely low-luminosity nature of NGC 4258, than models that include advection-dominated accretion flows.

Maryam Modjaz; James M. Moran; Paul T. Kondratko; Lincoln J. Greenhill

2005-02-11T23:59:59.000Z

237

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

238

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

239

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

240

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

Note: This page contains sample records for the topic "magnetic field lines" 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

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

242

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

243

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

244

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

245

Melatonin secretion and puberty in female lambs exposed to environmental electric and magnetic fields  

SciTech Connect

This study determined whether chronic exposure of female lambs to the electric and magnetic fields (EMF) of a high voltage transmission line can alter pineal secretion of melatonin and the normal occurrence of puberty. Twenty female Suffolk lambs were assigned randomly in equal numbers to a control and a treatment group. Treatment from 2 to 10 mo of age consisted of continuous exposure within the electrical environment of a 500-kV transmission line (mean electric field 6 kV/m, mean magnetic field 40 mG). Treated lambs were penned directly beneath the transmission line; control lambs were maintained in a pen of similar construction 229 m from the line where EMF were at ambient levels (mean electric field < 10 V/m, mean magnetic field < 0.3 mG). Melatonin was analyzed by RIA in serum of blood samples collected at 0.5-3-h intervals over eight 48-h periods. To assess attainment of puberty, serum concentrations of progesterone were determined by RIA from blood samples collected twice weekly beginning at 19 wk of age. Concentrations of circulating melatonin in control and treated lambs were low during daylight hours and increased during nighttime hours. The characteristic pattern of melatonin secretion during nighttime (amplitude, phase, and duration) did not differ between control and treatment groups. Age at puberty and number of subsequent estrous cycles also did not differ between groups. These data suggest that chronic exposure of developing female sheep to 60-Hz environmental EMF does not affect the mechanisms underlying the generation of the circadian pattern of melatonin secretion or the mechanisms involved in the onset of reproductive activity.

Lee, J.M. Jr.; Stormshak, F.; Thompson, J.M.; Thinesen, P.; Painter, L.J.; Olenchek, E.G.; Hess, D.L.; Forbes, R.; Foster, D.L. (Oregon State Univ., Corvallis (United States))

1993-10-01T23:59:59.000Z

246

RADIO DETECTION OF GREEN PEAS: IMPLICATIONS FOR MAGNETIC FIELDS IN YOUNG GALAXIES  

Science Conference Proceedings (OSTI)

Green Peas are a new class of young, emission line galaxies that were discovered by citizen volunteers in the Galaxy Zoo project. Their low stellar mass, low metallicity, and very high star formation rates make Green Peas the nearby (z {approx} 0.2) analogs of the Lyman break galaxies which account for the bulk of the star formation in the early universe (z {approx} 2-5). They thus provide accessible laboratories in the nearby universe for understanding star formation, supernova feedback, particle acceleration, and magnetic field amplification in early galaxies. We report the first direct radio detection of Green Peas with low frequency Giant Metrewave Radio Telescope observations and our stacking detection with archival Very Large Array FIRST data. We show that the radio emission implies that these extremely young galaxies already have magnetic fields ({approx}> 30 {mu}G) even larger than that of the Milky Way. This is at odds with the present understanding of magnetic field growth based on amplification of seed fields by dynamo action over a galaxy's lifetime. Our observations strongly favor models with pregalactic magnetic fields at {mu}G levels.

Chakraborti, Sayan; Yadav, Naveen; Ray, Alak [Department of Astronomy and Astrophysics, Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Colaba, Mumbai 400005 (India); Cardamone, Carolin, E-mail: sayan@tifr.res.in [Massachusetts Institute of Technology, 77 Massachusetts Avenue, Bldg. 26-331, Cambridge, MA 02139 (United States)

2012-02-10T23:59:59.000Z

247

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

248

3D Atlas vertical plate oil transmission line field calculations. Final report  

DOE Green Energy (OSTI)

Because of questions regarding current density and inductance estimates of the Atlas oil transmission line in the region where the vertical plates connect to the disk line, calculations using the 3D FE program Flux3d were initiated. Flux3d inductance values are nearly that estimated by D. Scudder. Calculations for three base designs of E. Ballard and D. Pierce were completed where several variations for each base design were used to determine the important parameters affecting inductance and to check inductance consistency. Flux3d showed for the first base design a very high current density of 36MA/m at the connection between the vertical and horizontal ground plates resulting in a magnetic pressure of 120 kpsi. The second base design modified this connection to reduce the current density to 20MA/m and 36 kpsi and for design 3 current density is 17MA/m. Maximum current density on the hot plates is 20MA/m for all 3 designs. These values assumed 1.2MA per VTL or 45.6MA total system current. Electrical fields on the top of the hot plate near the disk line connection is about 50% greater than the nominal value near the center of the vertical plates.

NONE

1997-09-18T23:59:59.000Z

249

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

250

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

251

Field Guide: Transmission Line Aerial Marking and Lighting  

Science Conference Proceedings (OSTI)

Electric transmission lines and wild birds must co-exist. Power lines traverse birds' flight routes, birds commonly roost on lines and poles, and birds make their nests—the largest of which weigh thousands of pounds—on transmission structures. Some avian activities can have deleterious effects on outdoor structures and transmission—for example, nests have been known to collapse and span critical clearances during storms, resulting in outages. Accordingly, it is important for ...

2013-11-22T23:59:59.000Z

252

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

253

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

254

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

255

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

256

Field Measurement Studies on Shunt Coefficient of Lightning Shield Line  

Science Conference Proceedings (OSTI)

The shunt coefficient of lightning shield line is an important parameter, which needs to be considered when we are designing or reforming the substation grounding network, however, it is difficult to be calculated. This paper is to introduce a method ... Keywords: Short circuit current, Lightning shield line, Shunt coefficient, Shunt impedance

Dechao Li; Jinglu Li; Yuhuan Zhang

2008-10-01T23:59:59.000Z

257

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

258

THE DYNAMICS OF THE SOLAR MAGNETIC FIELD: POLARITY REVERSALS, BUTTERFLY DIAGRAM, AND QUASI-BIENNIAL OSCILLATIONS  

SciTech Connect

The spatio-temporal dynamics of the solar magnetic field has been investigated by using NSO/Kitt Peak magnetic synoptic maps covering the period 1976 August-2003 September. The field radial component, for each heliographic latitude, has been decomposed in intrinsic mode functions through the Empirical Mode Decomposition in order to investigate the time evolution of the various characteristic oscillating modes at different latitudes. The same technique has also been applied on synoptic maps of the meridional and east-west components, which were derived from the observed line-of-sight projection of the field by using the differential rotation. Results obtained for the {approx}22 yr cycle, related to the polarity inversions of the large-scale dipolar field, show an antisymmetric behavior with respect to the equator in all the field components and a marked poleward flux migration in the radial and meridional components (from about -35 Degree-Sign and +35 Degree-Sign in the southern and northern hemispheres, respectively). The quasi-biennial oscillations (QBOs) are also identified as a fundamental timescale of variability of the magnetic field and associated with poleward magnetic flux migration from low latitudes around the maximum and descending phase of the solar cycle. Moreover, signs of an equatorward drift, at a {approx}2 yr rate, seem to appear in the radial and toroidal components. Hence, the QBO patterns suggest a link to a dynamo action. Finally, the high-frequency component of the magnetic field, at timescales less than 1 yr, provides the most energetic contribution and it is associated with the outbreaks of the bipolar regions on the solar surface.

Vecchio, A.; Meduri, D.; Carbone, V. [Dipartimento di Fisica, Universita della Calabria, 87036 Rende (Italy); Laurenza, M.; Storini, M., E-mail: vecchio@fis.unical.it [INAF/IFSI-Roma, Via del Fosso del Cavaliere 100, 00133 Roma (Italy)

2012-04-10T23:59:59.000Z

259

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

260

MAGNETIC FIELD GENERATION AND PARTICLE ENERGIZATION AT RELATIVISTIC SHEAR BOUNDARIES IN COLLISIONLESS ELECTRON-POSITRON PLASMAS  

SciTech Connect

Using particle-in-cell simulations, we study the kinetic physics of relativistic shear flow in collisionless electron-positron (e+e-) plasmas. We find efficient magnetic field generation and particle energization at the shear boundary, driven by streaming instabilities across the shear interface and sustained by the shear flow. Nonthermal, anisotropic high-energy particles are accelerated across field lines to produce a power-law tail turning over just below the shear Lorentz factor. These results have important implications for the dissipation and radiation of jets in blazars and gamma-ray bursts.

Liang, Edison; Smith, Ian [Rice University, MS 108, 6100 Main Street, Houston, TX 77005 (United States); Boettcher, Markus, E-mail: liang@rice.edu, E-mail: iansmith@rice.edu, E-mail: boettchm@ohio.edu [Physics and Astronomy Department, Ohio University, Athens, OH 45701 (United States)

2013-04-01T23:59:59.000Z

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261

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

262

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

263

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

264

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

265

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

266

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

267

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

268

The Influence of the Magnetic Field on Running Penumbral Waves in the Solar Chromosphere  

E-Print Network (OSTI)

We use images of high spatial and temporal resolution, obtained using both ground- and space-based instrumentation, to investigate the role magnetic field inclination angles play in the propagation characteristics of running penumbral waves in the solar chromosphere. Analysis of a near-circular sunspot, close to the center of the solar disk, reveals a smooth rise in oscillatory period as a function of distance from the umbral barycenter. However, in one directional quadrant, corresponding to the north direction, a pronounced kink in the period-distance diagram is found. Utilizing a combination of the inversion of magnetic Stokes vectors and force-free field extrapolations, we attribute this behaviour to the cut-off frequency imposed by the magnetic field geometry in this location. A rapid, localised inclination of the magnetic field lines in the north direction results in a faster increase in the dominant periodicity due to an accelerated reduction in the cut-off frequency. For the first time we reveal how th...

Jess, D B; Van Doorsselaere, T; Keys, P H; Mackay, D H

2013-01-01T23:59:59.000Z

269

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

270

Measurement of a Magnetic Field in a Leading Arm High Velocity Cloud  

E-Print Network (OSTI)

Using a recent catalogue of extragalactic Faraday rotation derived from the NRAO VLA Sky Survey we have found an agreement between Faraday rotation structure and the HI emission structure of a High Velocity Cloud (HVC) associated with the Leading Arm of the Magellanic System. We suggest that this morphological agreement is indicative of Faraday rotation through the HVC. Under this assumption we have used 48 rotation measures through the HVC, together with estimates of the electron column density from H-\\alpha\\ measurements and QSO absorption lines to estimate a strength for the line-of-sight component of the coherent magnetic field in the HVC of > 6 {\\rm \\mu G}$. A coherent magnetic field of this strength is more than sufficient to dynamically stabilize the cloud against ram pressure stripping by the Milky Way halo and may also provide thermal insulation for the cold cloud. We estimate an upper limit to the ratio of random to coherent magnetic field of $B_{r}/B_{||} < 0.8$, which suggests that the random ...

McClure-Griffiths, N M; Gaensler, B M; McConnell, D; Schnitzeler, D H F M

2010-01-01T23:59:59.000Z

271

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

272

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

273

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

274

Superconducting magnetic energy storage for BPA transmission-line stabilization  

DOE Green Energy (OSTI)

The Bonneville Power Administration (BPA) operates the electrical transmission system that joins the Pacific Northwest with southern California. A 30 MJ (8.4 kWh) Superconducting Magnetic Energy Storage (SMES) unit with a 10 MW converter is being installed at the Tacoma Substation to provide system damping for low frequency oscillations of 0.35 Hz. The integrated system status is described and reviewed. Components included in the system are the superconducting coil, seismically mounted in an epoxy fiberglass nonconducting dewar; a helium refrigerator; a heat rejection subsystem; a high pressure gas recovery subsystem; a liquid nitrogen trailer; the converter with power transformers and switchgear; and a computer system for remote microwave link operation of the SMES unit.

Rogers, J.D.; Barron, M.H.; Boenig, H.J.; Criscuolo, A.L.; Dean, J.W.; Schermer, R.I.

1982-01-01T23:59:59.000Z

275

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

276

Dependence of solar wind power spectra on the direction of the local mean magnetic field  

E-Print Network (OSTI)

(Abridged) Wavelet analysis can be used to measure the power spectrum of solar wind fluctuations along a line in any direction with respect to the local mean magnetic field. This technique is applied to study solar wind turbulence in high-speed streams in the ecliptic plane near solar minimum using magnetic field measurements with a cadence of eight vectors per second. The analysis of nine high-speed streams shows that the reduced spectrum of magnetic field fluctuations (trace power) is approximately azimuthally symmetric about B_0 in both the inertial range and dissipation range; in the inertial range the spectra are characterized by a power-law exponent that changes continuously from 1.6 \\pm 0.1 in the direction perpendicular to the mean field to 2.0 \\pm 0.1 in the direction parallel to the mean field. The large uncertainties suggest that the perpendicular power-law indices 3/2 and 5/3 are both consistent with the data. The results are similar to those found by Horbury et al. (2008) at high heliographic lat...

Podesta, J J

2009-01-01T23:59:59.000Z

277

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

278

Phase-Field Simulation of Line Edge Roughness in Block ...  

Science Conference Proceedings (OSTI)

... we'd expect. • We used an external “pinning field” at y = 0 and y = Ly to help orient the microdomains. (a) (b) (c) FIG 8: f ...

2012-10-04T23:59:59.000Z

279

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

280

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

Note: This page contains sample records for the topic "magnetic field lines" 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

Probing the Magnetic Field at Sub-Parsec Radii in the Accretion Disk of NGC 4258  

E-Print Network (OSTI)

We present an analysis of polarimetric observations at 22 GHz of the water vapor masers in NGC 4258 obtained with the VLA and the GBT. We do not detect any circular polarization in the spectrum indicative of Zeeman-induced splitting of the maser lines of water, a non-paramagnetic molecule. We have improved the 1-sigma upper limit estimate on the toroidal component of the magnetic field in the circumnuclear disk of NGC 4258 at a radius of 0.2 pc from 300 mG to 90 mG. We have developed a new method for the analysis of spectra with blended features and derive a 1-sigma upper limit of 30 mG on the radial component of the magnetic field at a radius of 0.14 pc. Assuming thermal and magnetic pressure balance, we estimate an upper limit on the mass accretion rate of ~10^(-3.7) M_sun/yr for a total magnetic field of less than 130 mG. We discuss the ramifications of our results on current maser models proposed to explain the observed maser emission structure and the consequences for current accretion theories. We find ...

Modjaz, M; Kondratko, P T; Greenhill, L J; Modjaz, Maryam; Moran, James M.; Kondratko, Paul T.; Greenhill, Lincoln J.

2005-01-01T23:59:59.000Z

282

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

283

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

284

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

285

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

286

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

287

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

288

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

289

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

290

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

291

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

292

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

293

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

294

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

295

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

296

Narrow-line magneto-optical cooling and trapping of strongly magnetic atoms  

E-Print Network (OSTI)

Laser cooling on weak transitions is a useful technique for reaching ultracold temperatures in atoms with multiple valence electrons. However, for strongly magnetic atoms a conventional narrow-line magneto-optical trap (MOT) is destabilized by competition between optical and magnetic forces. We overcome this difficulty in Er by developing an unusual narrow-line MOT that balances optical and magnetic forces using laser light tuned to the blue side of a narrow (8 kHz) transition. The trap population is spin-polarized with temperatures reaching below 2 microkelvin. Our results constitute an alternative method for laser cooling on weak transitions, applicable to rare-earth-metal and metastable alkaline earth elements.

Berglund, Andrew J; McClelland, Jabez J

2008-01-01T23:59:59.000Z

297

Narrow-line magneto-optical cooling and trapping of strongly magnetic atoms  

E-Print Network (OSTI)

Laser cooling on weak transitions is a useful technique for reaching ultracold temperatures in atoms with multiple valence electrons. However, for strongly magnetic atoms a conventional narrow-line magneto-optical trap (MOT) is destabilized by competition between optical and magnetic forces. We overcome this difficulty in Er by developing an unusual narrow-line MOT that balances optical and magnetic forces using laser light tuned to the blue side of a narrow (8 kHz) transition. The trap population is spin-polarized with temperatures reaching below 2 microkelvin. Our results constitute an alternative method for laser cooling on weak transitions, applicable to rare-earth-metal and metastable alkaline earth elements.

Andrew J. Berglund; James L. Hanssen; Jabez J. McClelland

2008-02-06T23:59:59.000Z

298

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

299

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

300

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

Note: This page contains sample records for the topic "magnetic field lines" 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

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

302

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

303

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

304

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

305

OBSERVATIONAL EVIDENCE OF CHANGING PHOTOSPHERIC VECTOR MAGNETIC FIELDS ASSOCIATED WITH SOLAR FLARES  

Science Conference Proceedings (OSTI)

Recent observations have provided evidence that the solar photospheric magnetic fields could have rapid and permanent changes in both longitudinal and transverse components associated with major flares. As a result, the Lorentz force (LF) acting on the solar photosphere and solar interior could be perturbed, and the change of LF is always nearly in the downward direction. However, these rapid and permanent changes have not been systematically investigated, yet, using vector magnetograms. In this paper, we analyze photospheric vector magnetograms covering five flares to study the evolution of photospheric magnetic fields. In particular, we investigate two-dimensional spatial distributions of the changing LF. Around the major flaring polarity inversion line, the net change of the LF is directed downward in an area of {approx}10{sup 19} cm{sup 2} for X-class flares. For all events, the white-light observations show that sunspots darken in this location after flares, and magnetic fields become more inclined, which is consistent with the ideas put forward by Hudson et al. and Fisher et al., and observations.

Su, J. T.; Jing, J.; Wang, H. M. [Space Weather Research Laboratory, New Jersey Institute of Technology, University Heights, Newark, NJ 07102-1982 (United States); Mao, X. J.; Wang, X. F.; Zhang, H. Q.; Deng, Y. Y.; Guo, J.; Wang, G. P., E-mail: sjt@bao.ac.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

2011-06-01T23:59:59.000Z

306

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

307

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

308

EVIDENCE FOR QUASI-ISOTROPIC MAGNETIC FIELDS FROM HINODE QUIET-SUN OBSERVATIONS  

SciTech Connect

Some recent investigations of spectropolarimetric observations of the Zeeman effect in the Fe I lines at 630 nm carried out with the Hinode solar space telescope have concluded that the strength of the magnetic field vector in the internetwork regions of the quiet Sun is in the hG regime and that its inclination is predominantly horizontal. We critically reconsider the analysis of such observations and carry out a complete Bayesian analysis with the aim of extracting as much information as possible from them, including error bars. We apply the recently developed BAYES-ME code that carries out a complete Bayesian inference for Milne-Eddington atmospheres. The sampling of the posterior distribution function is obtained with a Markov Chain Monte Carlo scheme and the marginal distributions are analyzed in detail. The Kullback-Leibler divergence is used to study the extent to which the observations introduce new information in the inference process resulting in sufficiently constrained parameters. Our analysis clearly shows that only upper limits to the magnetic field strength can be inferred, with fields in the kG regime completely discarded. Furthermore, the noise level present in the analyzed Hinode observations induces a substantial loss of information for constraining the azimuth of the magnetic field. Concerning the inclination of the field, we demonstrate that some information is available to constrain it for those pixels with the largest polarimetric signal. The results also point out that the field in pixels with small polarimetric signals can be nicely reproduced in terms of a quasi-isotropic distribution.

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

2009-08-20T23:59:59.000Z

309

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

310

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

311

Random Analysis on Line-Heat Source Temperature Field of Ground Source Heat Pumps Buried Pipes  

Science Conference Proceedings (OSTI)

In this paper the random properties of ground-source heat pump (GSHP) system.GSHP buried pipe to Kelvin one-dimensional line source of heat transfer model are discussed. The model randomness is analyzed, and the GSHP buried pipe to random excess temperature ... Keywords: GSHP, Buriedpipe, Line-heat source, Temperature field, Correlation

Changsheng Guan; Zhuodong Liu; Kai Xia; Xuyi Chen

2009-05-01T23:59:59.000Z

312

Field Guide: Transmission Line Aerial Marking and Lighting (Optimized for Electronic Viewing)  

Science Conference Proceedings (OSTI)

Various types of aerial marking and lighting are applied to transmission structures and wires as a safety enhancement to improve the visibility of structures and lines. This EPRI report, one in a series of practical guides designed as reference aids for utility personnel working in the field, is devoted to the subject of transmission line aerial marking and lighting, with an emphasis on inspection.This field guide has been optimized for viewing on electronic devices. For a standard PDF ...

2011-12-09T23:59:59.000Z

313

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

314

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

315

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

316

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

317

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

318

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

319

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

320

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

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321

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

322

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

323

The hybrid reactor project based on the straight field line mirror concept  

SciTech Connect

The straight field line mirror (SFLM) concept is aiming towards a steady-state compact fusion neutron source. Besides the possibility for steady state operation for a year or more, the geometry is chosen to avoid high loads on materials and plasma facing components. A comparatively small fusion hybrid device with 'semi-poor' plasma confinement (with a low fusion Q factor) may be developed for industrial transmutation and energy production from spent nuclear fuel. This opportunity arises from a large fission to fusion energy multiplication ratio, Q{sub r} = P{sub fis}/P{sub fus}>>1. The upper bound on Q{sub r} is primarily determined by geometry and reactor safety. For the SFLM, the upper bound is Q{sub r} Almost-Equal-To 150, corresponding to a neutron multiplicity of k{sub eff}=0.97. Power production in a mirror hybrid is predicted for a substantially lower electron temperature than the requirement T{sub e} Almost-Equal-To 10 keV for a fusion reactor. Power production in the SFLM seems possible with Q Almost-Equal-To 0.15, which is 10 times lower than typically anticipated for hybrids (and 100 times smaller than required for a fusion reactor). This relaxes plasma confinement demands, and broadens the range for use of plasmas with supra-thermal ions in hybrid reactors. The SFLM concept is based on a mirror machine stabilized by qudrupolar magnetic fields and large expander tanks beyond the confinement region. The purpose of the expander tanks is to distribute axial plasma loss flow over a sufficiently large area so that the receiving plates can withstand the heat. Plasma stability is not relying on a plasma flow into the expander regions. With a suppressed plasma flow into the expander tanks, a possibility arise for higher electron temperature. A brief presentation will be given on basic theory for the SFLM with plasma stability and electron temperature issues, RF heating computations with sloshing ion formation, neutron transport computations with reactor safety margins and material load estimates, magnetic coil designs as well as a discussion on the implications of the geometry for possible diagnostics. Reactor safety issues are addressed and a vertical orientation of the device could assist passive coolant circulation. Specific attention is put to a device with a 25 m long confinement region and 40 cm plasma radius in the mid-plane. In an optimal case (k{sub eff}= 0.97) with a fusion power of only 10 MW, such a device may be capable of producing a power of 1.5 GW{sub th}.

Agren, O.; Noack, K.; Moiseenko, V. E.; Hagnestal, A.; Kaellne, J.; Anglart, H. [Uppsala University, Angstroem Laboratory, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden); Institute of Plasma Physics, National Science Center 'Kharkiv Institute of Physics and Technology', 61108 Kharkiv (Ukraine); Uppsala University, Angstroem Laboratory, Uppsala University, Box 534, SE-751 21 Uppsala (Sweden); Royal Institute of Technology, Nuclear Reactor Technology, SE 100 44 Stockholm (Sweden)

2012-06-19T23:59:59.000Z

324

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

325

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

326

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

327

LDRD final report on confinement of cluster fusion plasmas with magnetic fields.  

Science Conference Proceedings (OSTI)

Two versions of a current driver for single-turn, single-use 1-cm diameter magnetic field coils have been built and tested at the Sandia National Laboratories for use with cluster fusion experiments at the University of Texas in Austin. These coils are used to provide axial magnetic fields to slow radial loss of electrons from laser-produced deuterium plasmas. Typical peak field strength achievable for the two-capacitor system is 50 T, and 200 T for the ten-capacitor system. Current rise time for both systems is about 1.7 {mu}s, with peak current of 500 kA and 2 MA, respectively. Because the coil must be brought to the laser, the driver needs to be portable and drive currents in vacuum. The drivers are complete but laser-plasma experiments are still in progress. Therefore, in this report, we focus on system design, initial tests, and performance characteristics of the two-capacitor and ten-capacitors systems. The questions of whether a 200 T magnetic field can retard the breakup of a cluster-fusion plasma, and whether this field can enhance neutron production have not yet been answered. However, tools have been developed that will enable producing the magnetic fields needed to answer these questions. These are a two-capacitor, 400-kA system that was delivered to the University of Texas in 2010, and a 2-MA ten-capacitor system delivered this year. The first system allowed initial testing, and the second system will be able to produce the 200 T magnetic fields needed for cluster fusion experiments with a petawatt laser. The prototype 400-kA magnetic field driver system was designed and built to test the design concept for the system, and to verify that a portable driver system could be built that delivers current to a magnetic field coil in vacuum. This system was built copying a design from a fixed-facility, high-field machine at LANL, but made to be portable and to use a Z-machine-like vacuum insulator and vacuum transmission line. This system was sent to the University of Texas in Austin where magnetic fields up to 50 T have been produced in vacuum. Peak charge voltage and current for this system have been 100 kV and 490 kA. It was used this last year to verify injection of deuterium and surrogate clusters into these small, single-turn coils without shorting the coil. Initial test confirmed the need to insulate the inner surface of the coil, which requires that the clusters must be injected through small holes in an insulator. Tests with a low power laser confirmed that it is possible to inject clusters into the magnetic field coils through these holes without destroying the clusters. The university team also learned the necessity of maintaining good vacuum to avoid insulator, transmission line, and coil shorting. A 200-T, 2 MA system was also constructed using the experience from the first design to make the pulsed-power system more robust. This machine is a copy of the prototype design, but with ten 100-kV capacitors versus the two used in the prototype. It has additional inductance in the switch/capacitor unit to avoid breakdown seen in the prototype design. It also has slightly more inductance at the cable connection to the vacuum chamber. With this design we have been able to demonstrate 1 MA current into a 1 cm diameter coil with the vacuum chamber at air pressure. Circuit code simulations, including the additional inductance with the new design, agree well with the measured current at a charge voltage of 40 kV with a short circuit load, and at 50 kV with a coil. The code also predicts that with a charge voltage of 97 kV we will be able to get 2 MA into a 1 cm diameter coil, which will be sufficient for 200 T fields. Smaller diameter or multiple-turn coils will be able to achieve even higher fields, or be able to achieve 200-T fields with lower charge voltage. Work is now proceeding at the university under separate funding to verify operation at the 2-MA level, and to address issues of debris mitigation, measurement of the magnetic field, and operation in vacuum. We anticipate operation at full current with single

Argo, Jeffrey W.; Kellogg, Jeffrey W.; Headley, Daniel Ignacio; Stoltzfus, Brian Scott; Waugh, Caleb J.; Lewis, Sean M.; Porter, John Larry, Jr.; Wisher, Matthew; Struve, Kenneth William; Savage, Mark Edward; Quevedo, Hernan J.; Bengtson, Roger

2011-11-01T23:59:59.000Z

328

Plasma Modes Along the Open Field Lines of a Neutron Star  

E-Print Network (OSTI)

We consider electrostatic plasma modes along the open field lines of a rotating neutron star. Goldreich-Julian charge density in general relativity is analyzed for the neutron star with zero inclination. It is found that the charge density is maximum at the polar cap and it remains almost same in certain extended region of the pole. For a steady state Goldreich-Julian charge density we found the usual plasma oscillation along the field lines; plasma frequency resembles to the gravitational redshift close to the Schwarzschild radius. We study the nonlinear plasma mode along the field lines. From the system of equations under general relativity, a second order differential equation is derived. The equation contains a term which describes the growing plasma modes near Schwarzschild radius in a black hole environment. The term vanishes with the distance far away from the gravitating object. For initially zero potential and field on the surface of a neutron star, Goldreich-Julian charge density is found to create the plasma mode, which is enhanced and propagates almost without damping along the open field lines. We briefly outline our plan to extend the work for studying soliton propagation along the open field lines of strongly gravitating objects.

U. A. Mofiz; B. J. Ahmedov

2007-05-30T23:59:59.000Z

329

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

330

Flexible gas insulated transmission line having regions of reduced electric field  

DOE Patents (OSTI)

A gas insulated transmission line having radially flexible field control means for reducing the electric field along the periphery of the inner conductor at predetermined locations wherein the support insulators are located. The radially flexible field control means of the invention includes several structural variations of the inner conductor, wherein careful controlling of the length to depth of surface depressions produces regions of reduced electric field. Several embodiments of the invention dispose a flexible connector at the predetermined location along the inner conductor where the surface depressions that control the reduced electric field are located.

Cookson, Alan H. (Pittsburgh, PA); Fischer, William H. (Wilkins Township, Allegheny County, PA); Yoon, Kue H. (Pittsburgh, PA); Meyer, Jeffry R. (Penn Hills Township, Allegheny County, PA)

1983-01-01T23:59:59.000Z

331

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

332

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

333

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

334

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

335

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

336

CHARACTERISTICS AND EVOLUTION OF THE MAGNETIC FIELD AND CHROMOSPHERIC EMISSION IN AN ACTIVE REGION CORE OBSERVED BY HINODE  

Science Conference Proceedings (OSTI)

We describe the characteristics and evolution of the magnetic field and chromospheric emission in an active region core observed by the Solar Optical Telescope (SOT) on Hinode. Consistent with previous studies, we find that the moss is unipolar, the spatial distribution of magnetic flux evolves slowly, and that the magnetic field is only moderately inclined. We also show that the field-line inclination and horizontal component are coherent, and that the magnetic field is mostly sheared in the inter-moss regions where the highest magnetic flux variability is seen. Using extrapolations from spectropolarimeter magnetograms, we show that the magnetic connectivity in the moss is different from that in the quiet Sun because most of the magnetic field extends to significant coronal heights. The magnetic flux, field vector, and chromospheric emission in the moss also appear highly dynamic but actually show only small-scale variations in magnitude on timescales longer than the cooling times for hydrodynamic loops computed from our extrapolations, suggesting high-frequency (continuous) heating events. Some evidence is found for flux (Ca II intensity) changes on the order of 100-200 G (DN) on timescales of 20-30 minutes that could be taken as indicative of low-frequency heating. We find, however, that only a small fraction (10%) of our simulated loops would be expected to cool on these timescales, and we do not find clear evidence that the flux changes consistently produce intensity changes in the chromosphere. Using observations from the EUV Imaging Spectrometer (EIS), we also determine that the filling factor in the moss is {approx}16%, consistent with previous studies and larger than the size of an SOT pixel. The magnetic flux and chromospheric intensity in most individual SOT pixels in the moss vary by less than {approx}20% and {approx}10%, respectively, on loop cooling timescales. In view of the high energy requirements of the chromosphere, we suggest that these variations could be sufficient for the heating of 'warm' EUV loops, but that the high basal levels may be more important for powering the hot core loops rooted in the moss. The magnetic field and chromospheric emission appear to evolve gradually on spatial scales comparable to the cross-field scale of the fundamental coronal structures inferred from EIS measurements.

Brooks, David H.; Warren, Harry P. [Space Science Division, Code 7673, Naval Research Laboratory, Washington, DC 20375 (United States); Winebarger, Amy R., E-mail: dhbrooks@ssd5.nrl.navy.mi [Department of Physics, Alabama A and M, 4900 Meridian Street, Normal, AL 35762 (United States)

2010-09-10T23:59:59.000Z

337

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

338

Uncertainties in field-line tracing in the magnetosphere. Part II: the complete internal geomagnetic field  

E-Print Network (OSTI)

geomagnetic field D. M. Willis1, *, J. Robin Singh 1,2 , K. S. C. Freeman1 1 Rutherford Appleton Laboratory coefficients that define the axisymmetric part of the internal geomagnetic field (i.e. g0 n 6 g0 n). Numerical geomagnetic field (i.e. gm n 6 gm n and hm n 6 hm n ). An algorithm is formulated that greatly reduces

Paris-Sud XI, Université de

339

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

340

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

Note: This page contains sample records for the topic "magnetic field lines" 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

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

342

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

343

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

344

Field Guide: Transmission Line Aerial Marking and Lighting (Hard Copy and Standard PDF)  

Science Conference Proceedings (OSTI)

Various types of aerial marking and lighting are applied to transmission structures and wires as a safety enhancement to improve the visibility of structures and lines. This EPRI report, one in a series of practical guides designed as reference aids for utility personnel working in the field, is devoted to the subject of transmission line aerial marking and lighting, with an emphasis on inspection. The pocket-sized, ring-bound guide is printed in color on high-quality paper. ...

2012-11-09T23:59:59.000Z

345

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

346

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

347

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

348

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

349

Direct measurement of the quantum state of the electromagnetic field in a superconducting transmission line  

E-Print Network (OSTI)

We propose an experimental procedure to directly measure the state of an electromagnetic field inside a resonator, corresponding to a superconducting transmission line, coupled to a Cooper-pair box (CPB). The measurement protocol is based on the use of a dispersive interaction between the field and the CPB, and the coupling to an external classical field that is tuned to resonance with either the field or the CPB. We present a numerical simulation that demonstrates the feasibility of this protocol, which is within reach of present technology.

F. de Melo; L. Aolita; F. Toscano; L. Davidovich

2006-02-23T23:59:59.000Z

350

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

351

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

352

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

353

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

354

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

355

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

356

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

357

MOA: Magnetic Field Oscillating Amplified Thruster and its Application for Nuclear Electric and Thermal Propulsion  

Science Conference Proceedings (OSTI)

More than 60 years after the later Nobel laureate Hannes Alfven had published a letter stating that oscillating magnetic fields can accelerate ionised matter via magneto-hydrodynamic interactions in a wave like fashion, the technical implementation of Alfven waves for propulsive purposes has been proposed, patented and examined for the first time by a group of inventors. The name of the concept, utilising Alfven waves to accelerate ionised matter for propulsive purposes, is MOA - Magnetic field Oscillating Amplified thruster. Alfven waves are generated by making use of two coils, one being permanently powered and serving also as magnetic nozzle, the other one being switched on and off in a cyclic way, deforming the field lines of the overall system. It is this deformation that generates Alfven waves, which are in the next step used to transport and compress the propulsive medium, in theory leading to a propulsion system with a much higher performance than any other electric propulsion system. Based on computer simulations, which were conducted to get a first estimate on the performance of the system, MOA is a highly flexible propulsion system, whose performance parameters might easily be adapted, by changing the mass flow and/or the power level. As such the system is capable to deliver a maximum specific impulse of 13116 s (12.87 mN) at a power level of 11.16 kW, using Xe as propellant, but can also be attuned to provide a thrust of 236.5 mN (2411 s) at 6.15 kW of power. While space propulsion is expected to be the prime application for MOA and is supported by numerous applications such as Solar and/or Nuclear Electric Propulsion or even as an 'afterburner system' for Nuclear Thermal Propulsion, other terrestrial applications can be thought of as well, making the system highly suited for a common space-terrestrial application research and utilisation strategy. (authors)

Frischauf, Norbert [QASAR Technologie(s) GmbH, Johann Gottekgasse 39, A-1230, Vienna (Austria); Hettmer, Manfred; Grassauer, Andreas; Bartusch, Tobias [QASAR Technologie(s) GmbH, Johann Gottekgasse 39, A-1230, Vienna (Austria); Koudelka, Otto [Institute of Communication Networks and Satellite Communication, Graz University of Technology, Inffeldgasse 12/I, A-8010 Graz (Austria)

2006-07-01T23:59:59.000Z

358

A new Jeans resolution criterion for (M)HD simulations of self-gravitating gas: Application to magnetic field amplification by gravity-driven turbulence  

E-Print Network (OSTI)

Cosmic structure formation is characterized by the complex interplay between gravity, turbulence, and magnetic fields. The processes by which gravitational energy is converted into turbulent and magnetic energies, however, remain poorly understood. Here, we show with high-resolution, adaptive-mesh simulations that MHD turbulence is efficiently driven by extracting energy from the gravitational potential during the collapse of a dense gas cloud. Compressible motions generated during the contraction are converted into solenoidal, turbulent motions, leading to a natural energy ratio of E_sol/E_tot of approximately 2/3. We find that the energy injection scale of gravity-driven turbulence is close to the local Jeans scale. If small seeds of the magnetic field are present, they are amplified exponentially fast via the small-scale dynamo process. The magnetic field grows most efficiently on the smallest scales, for which the stretching, twisting, and folding of field lines, and the turbulent vortices are sufficientl...

Federrath, Christoph; Schleicher, Dominik R G; Banerjee, Robi; Klessen, Ralf S

2011-01-01T23:59:59.000Z

359

Spectrometer sensitivity calibration in the extreme uv by means of branching ratios of magnetic dipole lines  

SciTech Connect

Relative intensity measurements of various line pairs resulting from magnetic dipole transitions within the configurations s/sup 2/p/sup 2/ and s/sup 2/p/sup 4/, in conjunction with calculated transition probabilities, have been used to determine the wavelength dependence of the sensitivity of a grazing incidence spectrometer, in the range 400 to 1000 A. Emissions from Cr XIX, Fe XXI, Ni XXI and XXIII, Cu XXIV, and Zr XXVII ions in PLT tokamak discharges were used for this purpose. Absolute sensitivity of the spectrometer at selected wavelengths had been determined by the traditional hydrogen, helium, carbon, and oxygen electric-dipole line pairs from the same discharges. Similar attempts to use transitions in the s/sup 2/p/sup 3/ configurations in Cr XVIII, Zr XXVI, and Mo XXVIII ions resulted in significant discrepancies that are ascribed to uncertainties in the corresponding calculated transition probabilities.

Denne, B.; Hinnov, E.

1984-04-01T23:59:59.000Z

360

Field Guide: Inspection of Transmission Line Grounding Systems (Optimized for Electronic Viewing)  

Science Conference Proceedings (OSTI)

This EPRI report, one in a series of practical guides designed as reference aids for utility personnel working in the field, visually catalogs the various condition issues that commonly affect transmission line grounding systems. It presents photographs and short written descriptions of the conditions and lists associated causes, failure modes, and impacts. This field guide has been optimized for viewing on electronic devices. For a standard PDF or copy of this product printed on high-quality paper ...

2011-12-09T23:59:59.000Z

Note: This page contains sample records for the topic "magnetic field lines" 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

Field Guide: Construction and Inspection of Compression Connectors for Overhead Transmission Lines  

Science Conference Proceedings (OSTI)

This field guide provides a general, field-deployable resource for utility professionals who are engaged in the construction and installation of compression connectors, as well as those who are involved with in-service inspection and assessment of this line component. It describes typical applications, compression connector basics, construction methods, common assembly errors, and inspection methods. In addition, it provides a list of relevant technical and training resources.The ...

2013-08-15T23:59:59.000Z

362

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

363

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

364

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

365

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

366

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

367

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

368

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

369

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

370

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.

371

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

372

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

373

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

374

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

375

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

376

Nuclear magnetic resonance studies of quadrupolar nuclei and dipolar field effects  

SciTech Connect

Experimental and theoretical research conducted in two areas in the field of nuclear magnetic resonance (NMR) spectroscopy is presented: (1) studies of the coherent quantum-mechanical control of the angular momentum dynamics of quadrupolar (spin I > 1/2) nuclei and its application to the determination of molecular structure; and (2) applications of the long-range nuclear dipolar field to novel NMR detection methodologies.The dissertation is organized into six chapters. The first two chapters and associated appendices are intended to be pedagogical and include an introduction to the quantum mechanical theory of pulsed NMR spectroscopy and the time dependent theory of quantum mechanics. The third chapter describes investigations of the solid-state multiple-quantum magic angle spinning (MQMAS) NMR experiment applied to I = 5/2 quadrupolar nuclei. This work reports the use of rotary resonance-matched radiofrequency irradiation for sensitivity enhancement of the I = 5/2 MQMAS experiment. These experiments exhibited certain selective line narrowing effects which were investigated theoretically.The fourth chapter extends the discussion of multiple quantum spectroscopy of quadrupolar nuclei to a mostly theoretical study of the feasibility of enhancing the resolution of nitrogen-14 NMR of large biomolecules in solution via double-quantum spectroscopy. The fifth chapter continues to extend the principles of multiple quantum NMR spectroscopy of quadrupolar nuclei to make analogies between experiments in NMR/nuclear quadrupolar resonance (NQR) and experiments in atomic/molecular optics (AMO). These analogies are made through the Hamiltonian and density operator formalism of angular momentum dynamics in the presence of electric and magnetic fields.The sixth chapter investigates the use of the macroscopic nuclear dipolar field to encode the NMR spectrum of an analyte nucleus indirectly in the magnetization of a sensor nucleus. This technique could potentially serve as an encoding module for the recently developed NMR remote detection experiment. The feasibility of using hyperpolarized xenon-129 gas as a sensor is discussed. This work also reports the use of an optical atomic magnetometer to detect the nuclear magnetization of Xe-129 gas, which has potential applicability as a detection module for NMR remote detection experiments.

Urban, Jeffry Todd

2004-12-21T23:59:59.000Z

377

Analysis of CAT-1 Monitor Field Data for SDG&E Lines 23007 and 23052 Using DTCR  

Science Conference Proceedings (OSTI)

This report concerns the analysis of field data provided by SDG&E for a Valley Group CAT-1 line tension monitoring instrument at San Mateo. Lines 23007 and 23052 were monitored. PDC utilized EPRI's DTCR3 software to calculate conductor temperatures and line ratings based on the tension, solar temperature and line current data. The results are evaluated in light of previous field tests sponsored by EPRI.

2006-03-08T23:59:59.000Z

378

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

379

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

380

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.

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381

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

382

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

383

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

384

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

385

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

386

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

387

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

388

Determination of High-Frequency Current Distribution Using EMTP-Based Transmission Line Models with Resulting Radiated Electromagnetic Fields  

SciTech Connect

Application of BPL technologies to existing overhead high-voltage power lines would benefit greatly from improved simulation tools capable of predicting performance - such as the electromagnetic fields radiated from such lines. Existing EMTP-based frequency-dependent line models are attractive since their parameters are derived from physical design dimensions which are easily obtained. However, to calculate the radiated electromagnetic fields, detailed current distributions need to be determined. This paper presents a method of using EMTP line models to determine the current distribution on the lines, as well as a technique for using these current distributions to determine the radiated electromagnetic fields.

Mork, B; Nelson, R; Kirkendall, B; Stenvig, N

2009-11-30T23:59:59.000Z

389

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

390

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

391

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

392

Electric and Magnetic Walls on Dielectric Interfaces  

E-Print Network (OSTI)

Sufficient conditions of the existence of electric or magnetic walls on dielectric interfaces are given for a multizone uniform dielectric waveguiding system. If one of two adjacent dielectric zones supports a TEM field distribution while the other supports a TM (TE) field distribution, then the common dielectric interface behaves as an electric (magnetic) wall, that is, the electric (magnetic) field line is perpendicular to the interface while the magnetic (electric) field line is parallel to the interface.

Changbiao Wang

2010-07-20T23:59:59.000Z

393

Analytical time domain electromagnetic field propagators and closed-form solutions for transmission lines  

E-Print Network (OSTI)

An analytical solution for the coupled telegrapher’s equations in terms of the voltage and current on a homogeneous lossy transmission line and multiconductor transmission line is presented. The resulting telegrapher’s equation solution is obtained in the form of an exact time domain propagator operating on the line voltage and current. It is shown that the analytical equations lead to a stable numerical method that can be used in the analysis of both homogeneous and inhomogeneous transmission lines. A numerical dispersion relation is derived proving that this method has no numerical dispersion down to the two points per wavelength Nyquist limit. Examples are presented showing that exceptionally accurate results are obtained for lossy single and multiconductor transmission lines. The method is extended to represent the general solution to Maxwell’s differential equations in vector matrix form. It is shown that, given the electromagnetic field and boundary conditions at a given instant in time, the free space time domain propagator and corresponding dyadic Green’s functions in 1-, 2-, and 3-dimensions can be used to calculate the field at all subsequent times.

Jeong, Jaehoon

2006-12-01T23:59:59.000Z

394

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

395

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

396

R&D ERL: Magnetic measurements of the ERL magnets  

SciTech Connect

The magnet system of ERL consists of G5 solenoids, 6Q12 quadrupoles with 0.58 T/m gradient, 3D60 dipoles with 0.4 T central field, 15 and 30 degree Z-bend injection line dipole/quadrupole combined function magnets, and extraction line magnets. More details about the magnets can be found in a report by G. Mahler. Field quality in all the 6Q12 quadrupoles, 3D60 dipoles and the injection line magnets has been measured with either a rotating coil, or a Hall probe mapper. This report presents the results of these magnetic measurements.

Jain, A.

2010-08-01T23:59:59.000Z

397

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...

398

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 ...

399

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

400

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

Note: This page contains sample records for the topic "magnetic field lines" 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

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

402

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

403

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

404

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

405

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

406

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

407

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

408

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

409

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

410

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

411

Investigation of a high impedance magnetically insulated transmission line oscillator with hollow load  

Science Conference Proceedings (OSTI)

A novel high-impedance magnetically insulated transmission line oscillator (MILO) with greatly restrained power deposition on the anode has been investigated. Methods to increase the MILO impedance and decrease the anode current are discussed. A MILO with impedance of 30 {Omega} and power conversion efficiency of 25% is presented by particle-in-cell simulations. Compared with the previous MILO in our lab, the anode current of the proposed MILO is reduced about 50%, the power conversion efficiency doubles, and the power deposition on anode is reduced nearly one half. Furthermore, considerations for reducing the power deposition on load have also been carried out in MILO design, and the load current is reduced to 4.6 kA, only 17% of the total anode current. Finally, a hollow load was introduced to reduce the power deposition density on the load, without decreasing the power conversion efficiency.

Zhou Heng; Shu Ting; Li Zhiqiang [College of Opto-electric Science and Engineering, National University of Defense Technology, Hunan 410073 (China)

2012-09-15T23:59:59.000Z

412

Theoretical and experimental investigation of axial power extraction from a magnetically insulated transmission line oscillator  

SciTech Connect

The utility of the magnetically insulated transmission line oscillator (MILO) as a high power microwave source depends on how efficiently power can be extracted from it. We have designed a slow-wave stepped transformer for the purpose of axially extracting microwave power from a 3.6 GHz coaxial MILO. The slow-wave transformer design was optimized using particle-in-cell simulation, and tested in experiments performed on the HPM Simulation Division's GEMINI and GYPSY water Blumlein pulse power sources. In this paper we summarize the slow-wave stepped transformer design, and describe MILO axial power extraction experiments which yielded up to 300 MW of radiated power. 10 refs., 4 figs., 2 tabs.

Lemke, R.W.; DeMuth, G.E.; Biggs, A.W. (Sandia National Labs., Albuquerque, NM (USA); Air Force Weapons Lab., Kirtland AFB, NM (USA); Alabama Univ., Huntsville, AL (USA). Dept. of Electrical and Computer Engineering)

1989-01-01T23:59:59.000Z

413

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

414

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

415

Effects of a 60 Hz Magnetic Field of up to 50 mT on Human Neuromotor Control: An EEG/EMG/Tremor Study  

Science Conference Proceedings (OSTI)

High voltage power lines, industrial processes, and domestic electric appliances are among the numerous sources of daily exposure to extremely low frequency (ELF, below 300 Hz) magnetic fields (MF). ELF MF effects on humans have been studied over the past few decades, and these fields have been reported to affect human movement, brain electrical activity, and high-level brain information processing (cognition). Different strategies have been used to tackle this question using various physiological, ...

2013-11-25T23:59:59.000Z

416

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

417

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.

418

Magnetic fluorescent lamp  

DOE Patents (OSTI)

The radiant emission of a mercury-argon discharge in a fluorescent lamp assembly is enhanced by providing means for establishing a magnetic field with lines of force along the path of electron flow through the bulb of the lamp assembly, to provide Zeeman splitting of the ultraviolet spectral line. Optimum results are obtained when the magnetic field strength causes a Zeeman splitting of approximately 1.7 times the thermal line width.

Berman, S.M.; Richardson R.W.

1983-12-29T23:59:59.000Z

419

Parahydrogen-enhanced zero-field nuclear magnetic ...  

Science Conference Proceedings (OSTI)

... inspection reveals small splittings of some lines due to long-range (at least four-bond) homonuclear couplings to protons on the benzene ring. ...

2011-06-20T23:59:59.000Z

420

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

Note: This page contains sample records for the topic "magnetic field lines" 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.


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