Science.gov

Sample records for magnetic field configurations

  1. Magnetic field configuration of the theta aurora

    NASA Technical Reports Server (NTRS)

    Toffoletto, F. R.; Hill, T. W.

    1990-01-01

    A magnetic configuration of the open magnetosphere is described which is conducive to the formation of the theta aurora when the IMF has a significant northward component. A magnetic field topology and polar cap configuration, derived from a quantitative model of the open magnetosphere that incorporates Crooker's antiparallel merging hypothesis, are presented. Under this hypothesis, when the IMF has a northward component, the dayside merging line bifurcates, leaving a large fraction of the subsolar magnetopause untouched by the merging process. The polar cap, defined by tracing magnetic field lines that connect from the solar wind to the earth, is similarly bifurcated, leaving a sun-aligned stagnation region that is not magnetically connected to the solar wind and may plausibly be associated with the sun-aligned 'bar' of the theta aurora. The model provides testable predictions with regard to the position of this 'convection gap' in both Northern and Southern Hemispheres as functions of IMF direction.

  2. Magnetic Reconnection in Field-Reversed Configurations

    NASA Astrophysics Data System (ADS)

    Sevillano, Evelio

    Internal magnetic field probes are used to study the magnetic field-line reconnection during the formation of Field-Reversed Configurations (FRC's) in a low-compression theta-pinch. Measurements of the reversed trapped flux indicated that most of the loss of the initial bias flux occurs during the radial implosion. Therefore the flux loss is not a consequence of plasma-wall contact during field-reversal. An operating boundary in the parameter space of filling pressure, bias field and external field is found for formation of FRC's with equilibrium lengths shorter than the coil. Measurements of the internal magnetic fields near the ends of the theta-pinch indicate that FRC formation can be delayed by plasma flow out the ends. The addition of independently driven magnetic mirrors extends the operating boundary. An axial array of magnetic islands forms during the early stages of the discharge. These islands then coalesce into large units. Several possible explanations of their formation are given. In addition, the growth rate for coalescence obtained from MHD simulations is compared with the experimental results. With the addition of a third magnetic mirror near the midplane of the device the formation of a two-cell FRC is observed. These experiments provide a proof-of -principle for possible future multiple-cell experiments. It was discovered that the reconnection in the region of the X-point between the cells consisted of two phases. A slow phase, where flux is dissipated slowly, is followed by the onset of a fast reconnection phase which leads to the formation of the two independent cells. The FRC's created are different than those in most other experiments in that neither an n = 2 rotational instability nor a strong axial contraction are observed. Simultaneous measurements of the density and excluded-flux radius indicate that the configurations terminate as a result of a radial collapse. This collapse may be a consequence of loss of the reversed flux as a barrier of radiation energy loss is crossed and the plasma resistivity consequently increases.

  3. Configuration of the local interstellar magnetic field

    NASA Astrophysics Data System (ADS)

    Frisch, Priscilla C.; Andersson, B.; Berdhyugin, A.; Funsten, H. O.; DeMajistre, R.; Magalhaes, A.; McComas, D.; Piirola, V.; Schwadron, N.; Seriacopi, D.; Slavin, J. D.; Wiktorowicz, S.; IBEX Team

    2014-01-01

    The discovery of the Ribbon of energetic neutral atoms by the Interstellar Boundary Explorer (IBEX) provides a new and unexpected diagnostic of the direction of the local interstellar magnetic field (ISMF). The IBEX Ribbon forms where the interstellar magnetic field draping over the heliosphere is perpendicular to the sightline. We have shown that the direction of the interstellar magnetic field close to the Sun, obtained from starlight polarized in the interstellar medium (ISM), is consistent with the ISMF direction that is traced by the IBEX Ribbon. In this presentation we show that new optical polarization data indicate that the local ISMF has a smoothly varying component stretching from the first to the third galactic quadrant. Both the ISMF direction and the kinematics of local interstellar gas within tens of parsecs support an interpretation where the local interstellar clouds are a fragment of the expanding Loop I superbubble.

  4. Electrostatic waves in general magnetic field configurations

    SciTech Connect

    Chen, L.; Tsai, S.T.

    1981-07-01

    A scheme for investigating linear electrostatic waves in general magnetically confined plasmas is presented. The scheme is a generalization of the low-frequency (less than the cyclotron frequency) gyrokinetic formalism of Rutherford and Frieman as well as Taylor and Hastie to arbitrary frequencies. Governing integral wave equations for slab plasmas with magnetic shear as well as axisymmetric tokamaks are then derived to illustrate the applications.

  5. Modelling the magnetic field configuration of neutron stars

    NASA Astrophysics Data System (ADS)

    Ciolfi, R.

    2014-09-01

    The properties of the extremely strong magnetic fields of neutron stars affect in a unique way their evolution and the associated phenomenology. Due to the lack of constraints from direct observations, our understanding of the magnetic field configuration in neutron star interiors depends on the progress in theoretical modelling. Here we discuss the effort in building models of magnetized neutron stars focussing on some of the recent results. In particular, we comment on the instability of purely poloidal and purely toroidal magnetic field configurations and on the evidence in favour of the so-called twisted-torus solutions. We conclude with an outlook on the present status of the field and future directions.

  6. A filament supported by different magnetic field configurations

    NASA Astrophysics Data System (ADS)

    Guo, Y.; Schmieder, B.; Dmoulin, P.; Wiegelmann, T.; Aulanier, G.; Trk, T.; Bommier, V.

    2011-08-01

    A nonlinear force-free magnetic field extrapolation of vector magnetogram data obtained by THEMIS/MTR on 2005 May 27 suggests the simultaneous existence of different magnetic configurations within one active region filament: one part of the filament is supported by field line dips within a flux rope, while the other part is located in dips within an arcade structure. Although the axial field chirality (dextral) and the magnetic helicity (negative) are the same along the whole filament, the chiralities of the filament barbs at different sections are opposite, i.e., right-bearing in the flux rope part and left-bearing in the arcade part. This argues against past suggestions that different barb chiralities imply different signs of helicity of the underlying magnetic field. This new finding about the chirality of filaments will be useful to associate eruptive filaments and magnetic cloud using the helicity parameter in the Space Weather Science.

  7. Ring Current Modeling in a Realistic Magnetic Field Configuration

    NASA Technical Reports Server (NTRS)

    Fok, M.-C.; Moore, T. E.

    1997-01-01

    A 3-dimensional kinetic model has been developed to study the dynamics of the storm time ring current in a dipole magnetic field. In this paper, the ring current model is extended to include a realistic, time-varying magnetic field model. The magnetic field is expressed as the cross product of the gradients of two Euler potentials and the bounce-averaged particle drifts are calculated in the Euler potential coordinates. A dipolarization event is modeled by collapsing a tail-like magnetosphere to a dipole-like configuration. Our model is able to simulate the sudden enhancements in the ring current ion fluxes and the corresponding ionospheric precipitation during the substorm expansion.

  8. Hamiltonian description of closed configurations of the vacuum magnetic field

    NASA Astrophysics Data System (ADS)

    Skovoroda, A. A.

    2015-05-01

    Methods of obtaining and using the Hamiltonians of closed vacuum magnetic configurations of fusion research systems are reviewed. Various approaches to calculate the flux functions determining the Hamiltonian are discussed. It is shown that the Hamiltonian description allows one not only to reproduce all traditional results, but also to study the behavior of magnetic field lines by using the theory of dynamic systems. The potentialities of the Hamiltonian formalism and its close relation to traditional methods are demonstrated using a large number of classical examples adopted from the fundamental works by A.I. Morozov, L.S. Solov'ev, and V.D. Shafranov.

  9. Analytical study of the magnetic field generated by multipolar magnetic configuration

    NASA Astrophysics Data System (ADS)

    Murillo Acevedo, M. T.; Dugar-Zhabon, V. D.; Otero, O.

    2016-02-01

    The magneto-statics field from a parallelepiped magnet which can turn around an axis, is the first step to find the whole magnetic field in a multipolar configuration. This configuration is present in the ion sources, which are heated by electron cyclotron resonance. We present the analytic formulas to calculate this magnetic field outside the volume of the magnet. To model the magnet, we considered a constant magnetization vector inside of magnet volume. Therefore, the magnetic scalar potential method can be used. We present the results by a hexapolar system. Their magnetic field components are calculated on confinement region, several graphics are shown with directions and magnitude's gradients of the magnetic field to help understand better the confinement system. Our results are confronted with experimental ones. These formulas are very useful in research of plasma magnetic confinement in ion sources through computational simulations.

  10. Anisotropic Magnetic Confinement. Applications to Field-Reversed Configurations

    NASA Astrophysics Data System (ADS)

    Clemente, Roberto Antonio

    Introducing an auxiliary function of the usual poloidal magnetic stream function, it is possible to obtain axisymmetric solutions of the ideal anisotropic magnetohydrodynamic equations for steady rotating plasmas, in terms of solutions of the Maschke and Perrin equation for isotropic plasmas, with temperature as a surface function. For vanishing rotation, the problem is reduced to the classical Grad-Schlter-Shafranov equation for static equilibria. Some applications of the equilibrium models to the study of tilting stability and classical particle transport in field-reversed configurations are presented.

  11. Interpretation of the coronal magnetic field configuration of the Sun

    NASA Astrophysics Data System (ADS)

    Li, Bo; Li, Xing; Yu, Hui

    2012-12-01

    The origin of the heliospheric magnetic flux on the Sun, and hence the origin of the solar wind, is a topic of hot debate. While the prevailing view is that the solar wind originates from outside the coronal streamer helmets, there also exists the suggestion that the open magnetic field spans a far wider region. Without the definitive measurement of the coronal magnetic field, it is difficult to unambiguously resolve the conflict between the two scenarios. We present two 2-dimensional, Alfvnic-turbulence-based models of the solar corona and solar wind, one with and the other without a closed magnetic field region in the inner corona. The purpose of the latter model is to test whether it is possible to realize a picture suggested by polarimetric measurements of the corona using the Fe XIII 10747 line, where open magnetic field lines seem to penetrate the streamer base. The boundary conditions at the coronal base are able to account for important observational constraints, especially those on the magnetic flux distribution. Interestingly, the two models provide similar polarized brightness (pB) distributions in the field of view (FOV) of SOHO/LASCO C2 and C3 coronagraphs. In particular, a dome-shaped feature is present in the C2 FOV even for the model without a closed magnetic field. Moreover, both models fit the Ulysses data scaled to 1 AU equally well. We suggest that: 1) The pB observations cannot be safely taken as a proxy for the magnetic field topology, as is often implicitly assumed. 2) The Ulysses measurements, especially the one showing a nearly uniform distribution with heliocentric latitude of the radial magnetic field, do not rule out the ubiquity of open magnetic fields on the Sun.

  12. Resonance and Chaotic Trajectories in Magnetic Field Reversed Configuration

    SciTech Connect

    A.S. Landsman; S.A. Cohen; M. Edelman; G.M. Zaslavsky

    2005-04-13

    The nonlinear dynamics of a single ion in a field-reversed configuration (FRC) were investigated. FRC is a toroidal fusion device which uses a specific type of magnetic field to confine ions. As a result of angular invariance, the full three-dimensional Hamiltonian system can be expressed as two coupled, highly nonlinear oscillators. Due to the high nonlinearity in the equations of motion, the behavior of the system is extremely complex, showing different regimes, depending on the values of the conserved canonical angular momentum and the geometry of the fusion vessel. Perturbation theory and averaging were used to derive the unperturbed Hamiltonian and frequencies of the two degrees of freedom. The derived equations were then used to find resonances and compare to Poincar{copyright} surface-of-section plots. A regime was found where the nonlinear resonances were clearly separated by KAM [Kolmogorov-Arnold-Mosher] curves. The structure of the observed island chains was explained. The condition for the destruction of KAM curves and the onset of strong chaos was derived, using Chirikov island overlap criterion, and shown qualitatively to depend both on the canonical angular momentum and geometry of the device. After a brief discussion of the adiabatic regime the paper goes on to explore the degenerate regime that sets in at higher values of angular momenta. In this regime, the unperturbed Hamiltonian can be approximated as two uncoupled linear oscillators. In this case, the system is near-integrable, except in cases of a universal resonance, which results in large island structures, due to the smallness of nonlinear terms, which bound the resonance. The linear force constants, dominant in this regime, were derived and the geometry for a large one-to-one resonance identified. The above analysis showed good agreement with numerical simulations and was able to explain characteristic features of the dynamics.

  13. Evaluation of magnetic refocusing in linear-beam microwave tubes. [using optimal magnetic field configuration

    NASA Technical Reports Server (NTRS)

    Stankiewicz, N.

    1974-01-01

    Magnetic field configurations in which the axial component of the field decays linearly to a constant plateau field are evaluated for use in refocusing the output beam of linear beam microwave tubes. The slope of the decay and the value of the plateau field are parameters in this study. A uniform beam with a space charge force only in the radial direction is assumed, and the electron trajectories are computed for various classes. For a given magnetic configuration (slope and plateau value) the plateau length is calculated for a specified class and the rms deviation of the output angles for all classes is computed at the end of this plateau length. A minimum condition for a refocused beam is defined to be one in which the rms value of the output angles is less than the rms input. Many of the configurations satisfied this criteria and successfully reduced the rms value by half.

  14. What Controls the Configuration of the Titan Ionospheric Magnetic Field

    NASA Astrophysics Data System (ADS)

    Wei, Hanying; Ma, Yingjuan; Russell, Christopher; Dougherty, Michele

    2013-04-01

    Titan does not have a significant intrinsic magnetic field, but it has a dense atmosphere which interacts with the sub-corotating plasma in the Saturnian magnetosphere. During the interaction, the upstream plasma flow slows down and diverts around Titan, and the magnetic field slowly diffuses into Titan's ionosphere and induces currents in the ionosphere. The resulting field pattern is that, upstream field lines drape around Titan, and downstream field lines stretch into a tail. We investigate whether such a draping-field pattern is present statistically in all eight years of Cassini Titan flyby data, to answer the question, How well can a steady-state model predict the observations? We find that the high-altitude field (above 1200 km altitudes) agrees with the draping-field picture and can be well-ordered by the current upstream conditions; however, the low-altitude (below 1200 km altitudes) field does not. Due to the time-variability of upstream conditions, coupling between the neutral and ionized components of the atmosphere, and the long magnetic-diffusion time scale at low altitudes, the magnetic field at these altitudes has a complex pattern and may not be due to the "current" upstream condition but a "previous" upstream condition. We use MHD models to simulate the Titan interaction with varying upstream conditions and Titan scales of fields at high and low altitudes. This paper presents the results from these observations and simulations.

  15. The magnetic field and magnetospheric configuration of Uranus

    NASA Technical Reports Server (NTRS)

    Ness, Norman F.; Connerney, John E. P.; Lepping, Ronald P.; Schulz, Michael; Voigt, Gerd-Hannes

    1991-01-01

    A significant and unique planetary magnetic field discovered by Voyager 2 is presented. A large tilt of 58.6 deg of the magnetic-dipole axis from the rotation axis was found. Combined with a large offset of 0.3 RU of the magnetic dipole from the center of the planet, the moment of 0.23 gauss-RU3 leads to field magnitudes at the surface which vary widely between 0.1 and 1.0 gauss. A simple diagram illustrating the offset tilted dipole of Uranus and some field lines is shown. A more exact and accurate spherical-harmonic model of the planetary field, which includes both dipole and quadrupole moments, is derived. There exists a well-developed bipolar magnetic tail on the night side of the planet which rotates daily about the extended planet-sunline with Uranus because of the large obliquity of the Uranian rotation axis.

  16. Large Solar Flares and Sheared Magnetic Field Configuration

    NASA Technical Reports Server (NTRS)

    Choudhary, Debi Prasad

    2001-01-01

    This Comment gives additional information about the nature of flaring locations on the Sun described in the article "Sun unleashes Halloween storm", by R. E. Lopez, et al. What causes the large explosions from solar active regions that unleash huge magnetic storms and adverse space weather? It is now beyond doubt that the magnetic field in solar active regions harbors free energy that is released during these events. Direct measurements of the longitudinal and transverse components of active region magnetic fields with the vector magnetograph at NASA Marshall Space Flight Center (MSFC), taken on a regular basis for the last 30 years, have found key signatures of the locations of powerful flares. A vector magnetograph detects and measures the magnetic shear, which is the deviation of the observed transverse magnetic field direction from the potential field. The sheared locations possess abundant free magnetic energy for solar flares. In addition to active region NOAA 10486, the one that produced the largest flares last October, the NASA/MSFC vector magnetograph has observed several other such complex super active regions, including NOAA 6555 and 6659.

  17. Hanle Effect Diagnostics of the Coronal Magnetic Field: A Test Using Realistic Magnetic Field Configurations

    NASA Astrophysics Data System (ADS)

    Raouafi, N.-E.; Solanki, S. K.; Wiegelmann, T.

    2009-06-01

    Our understanding of coronal phenomena, such as coronal plasma thermodynamics, faces a major handicap caused by missing coronal magnetic field measurements. Several lines in the UV wavelength range present suitable sensitivity to determine the coronal magnetic field via the Hanle effect. The latter is a largely unexplored diagnostic of coronal magnetic fields with a very high potential. Here we study the magnitude of the Hanle-effect signal to be expected outside the solar limb due to the Hanle effect in polarized radiation from the H I Ly? and ? lines, which are among the brightest lines in the off-limb coronal FUV spectrum. For this purpose we use a magnetic field structure obtained by extrapolating the magnetic field starting from photospheric magnetograms. The diagnostic potential of these lines for determining the coronal magnetic field, as well as their limitations are studied. We show that these lines, in particular H I Ly?, are useful for such measurements.

  18. Magnetic field configuration in a flaring active region

    NASA Astrophysics Data System (ADS)

    Palacios, J.; Balmaceda, L. A.; Vieira, L. E.

    2015-10-01

    The Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) provides continuous monitoring of the Sun's vector magnetic field through full-disk photospheric data with both high cadence and high spatial resolution. Here we investigate the evolution of AR 11249 from March 6 to March 7, 2012. We make use of HMI Stokes imaging, SDO/SHARPs, the HMI magnetic field line-of-sight (LOS) maps and the transverse components of the magnetic field as well as LOS velocity maps in order to detect regions with significant flux emergence and/or cancellation. In addition, we apply the Local Correlation Tracking (LCT) technique to the total and signed magnetic flux data and derive maps of horizontal velocity. From this analysis, we were able to pinpoint localized shear regions (and a shear channel) where penumbrae and pore formation areas, with strong linear polarization signals, are stretched and squeezed, showing also important downflows and upflows. We have also utilized Hinode/SP data and compared them to the HMI-SHARPs and the HMI-Stokes spectrograms. The aforementioned shear channel seems to correspond well with the X-class flare main channel of March 7 2012, as observed in AIA/SDO 171, 304 and 1600 Å.

  19. Unbalanced magnetic field configuration: plasma and film properties.

    PubMed

    Rodil, S E; Olaya, J J

    2006-08-16

    Coatings of CrN, TiN, ZrN, TaN and NbN were deposited using an unbalanced magnetron sputtering system with two different degrees of unbalancing to investigate the effect of the degree of unbalancing on both plasma characteristics and film properties. The degree of unbalancing was determined by an extensive characterization of the magnetic field fluxes in the X-Z plane perpendicular to the target. Then, the plasma parameters, such as electron temperature, plasma potential, plasma density and ion current density, were obtained for each target and as a function of the unbalance coefficient. The film microstructure, hardness, corrosion and wear resistant were measured to determine the effect of the degree of unbalancing on these properties. The results suggested that the degree of unbalancing, through the variations induced in the ion bombardment and plasma ionization, had a strong influence on the film hardness, microstructure and preferred orientation. PMID:21690858

  20. Probe measurements of the three-dimensional magnetic field structure in a rotating magnetic field sustained field-reversed configuration

    SciTech Connect

    Velas, K. M.; Milroy, R. D.

    2014-01-15

    A translatable three-axis probe was constructed and installed on the translation, confinement, and sustainment upgrade (TCSU) experiment. With ninety windings, the probe can simultaneously measure B{sub r}, B{sub ?}, and B{sub z} at 30 radial positions, and can be placed at any desired axial position within the field reversed configuration (FRC) confinement chamber. Positioning the probe at multiple axial positions and taking multiple repeatable shots allows for a full r-z map of the magnetic field. Measurements were made for odd-parity rotating magnetic field (RMF) antennas and even-parity RMF. The steady state data from applying a 10?kHz low pass filter used in conjunction with data at the RMF frequency yields a map of the full 3D rotating field structure. Comparisons will be made to the 3D magnetic structure predicted by NIMROD simulations, with parameters adjusted to match that of the TCSU experiments. The probe provides sufficient data to utilize a Maxwell stress tensor approach to directly measure the torque applied to the FRC's electrons, which combined with a resistive torque model, yields an estimate of the average FRC resistivity.

  1. 3D magnetic field configuration of small-scale reconnection events in the solar plasma atmosphere

    NASA Astrophysics Data System (ADS)

    Shimizu, T.

    2015-10-01

    The outer solar atmosphere, i.e., the corona and the chromosphere, is replete with small energy-release events, which are accompanied by transient brightening and jet-like ejections. These events are considered to be magnetic reconnection events in the solar plasma, and their dynamics have been studied using recent advanced observations from the Hinode spacecraft and other observatories in space and on the ground. These events occur at different locations in the solar atmosphere and vary in their morphology and amount of the released energy. The magnetic field configurations of these reconnection events are inferred based on observations of magnetic fields at the photospheric level. Observations suggest that these magnetic configurations can be classified into two groups. In the first group, two anti-parallel magnetic fields reconnect to each other, yielding a 2D emerging flux configuration. In the second group, helical or twisted magnetic flux tubes are parallel or at a relative angle to each other. Reconnection can occur only between anti-parallel components of the magnetic flux tubes and may be referred to as component reconnection. The latter configuration type may be more important for the larger class of small-scale reconnection events. The two types of magnetic configurations can be compared to counter-helicity and co-helicity configurations, respectively, in laboratory plasma collision experiments.

  2. Study on Axially Distributed Divertor Magnetic Field Configuration in a Mirror Cell

    SciTech Connect

    Islam, M.K.; Nakashima, Y.; Higashizono, Y.; Katanuma, I.; Cho, T

    2005-01-15

    A mirror magnetic field configuration (MFC) is studied in which a divertor is distributed axially using multipole coils. Both configurations of divertor and minimum-B are obtained in a mirror cell. Magnetohydrodynamic (MHD) instability of a mirror cell can be eliminated in this way. Concept of the design and properties of the MFC are discussed.

  3. Convective Power Loss Measurements in a Field Reversed Configuration with Rotating Magnetic Field Current Drive

    NASA Astrophysics Data System (ADS)

    Melnik, Paul

    The Translation, Confinement, and Sustainment Upgrade (TCSU) experiment achieves direct formation and sustainment of a field reversed configuration (FRC) plasma through rotating magnetic fields (RMF). The pre-ionized gas necessary for FRC formation is supplied by a magnetized cascade arc source that has been developed for TCSU. To ensure ideal FRC performance, the condition of the vacuum chamber prior to RMF start-up has been characterized with the use of a fast response ion gauge. A circuit capable of gating the puff valves with initial high voltage for quick response and then indefinite operational voltage was also designed. A fully translatable combination Langmuir / Mach probe was also built to measure the electron temperature, electron density, and ion velocity of the FRC. These measurements were also successfully completed in the FRC exhaust jets allowing for an accurate analysis of the FRC power loss through convection.

  4. Flux generation and sustainment of a field reversed configuration with rotating magnetic field current drive

    SciTech Connect

    Slough, J. T.; Miller, K. E.

    2000-05-01

    A new experimental device has been constructed to study the flux build-up and sustainment of a field reversed configuration (FRC) with a rotating magnetic field (RMF). Even though complete penetration was expected from RMF theory, the RMF field was observed to penetrate only a few centimeters inside the FRC separatrix. Despite the limited penetration, significantly larger toroidal currents (40 kA) were driven than in previous experiments ({approx}2 kA) with the same RMF field. The high currents and lack of deep penetration allowed the axial field to be the dominant field throughout the FRC. The radially inward pondermotive force arising from axial screening currents at the FRC edge had a significant influence on energy and particle confinement, reducing convective losses to the limit of observability. With only ohmic heating, the measured low ion temperatures (2 eV) left the ions unmagnetized while the electrons ({approx}40 eV) were well magnetized. No destructive instability was observed for the RMF driven FRC despite the lack of a strong kinetic ion component. (c) 2000 American Institute of Physics.

  5. Rotating magnetic field current drive of high-temperature field reversed configurations with high {zeta} scaling

    SciTech Connect

    Guo, H. Y.; Hoffman, A. L.; Milroy, R. D.

    2007-11-15

    Greatly reduced recycling and impurity ingestion in the Translation, Confinement, and Sustainment--Upgrade (TCSU) device has allowed much higher plasma temperatures to be achieved in the field reversed configurations (FRC) under rotating magnetic field (RMF) formation and sustainment. The hotter plasmas have higher magnetic fields and much higher diamagnetic electron rotation rates so that the important ratio of average electron rotation frequency to RMF frequency, called {zeta}, approaches unity, for the first time, in TCSU. A large fraction of the RMF power is absorbed by an as yet unexplained (anomalous) mechanism directly proportional to the square of the RMF magnitude. It becomes of relatively lesser significance as the FRC current increases, and simple resistive heating begins to dominate, but the anomalous absorption is useful for initial plasma heating. Measurements of total absorbed power, and comparisons of applied RMF torque to torque on the electrons due to electron-ion friction under high-{zeta} operation, over a range of temperatures and fields, have allowed the separation of the classical Ohmic and anomalous heating to be inferred, and cross-field plasma resistivities to be calculated.

  6. Power deposition and field penetration in a field-reversed configuration generated by rotating magnetic fields

    NASA Astrophysics Data System (ADS)

    Kuthi, A.; Zwi, H.; Wells, B.; Wong, A. Y.

    1989-07-01

    Power deposition profiles derived from measured equlibrium and field-penetration profiles in the RACETRACK rotating magnetic field drived FRC are presented. It is found, that significantly higher RF power can be deposited in the plasma than what is necessary to maintain the diamagnetic current. The Klima relations are reconciled with the higher power input because the excess power is delivered by waves possessing zero net angular momentum. Only the right-hand rotating component of the RF field penetrates fully, and this results in correct circular polarization of the fields on axis regardless of the imposed polarization by the antennas.

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

    SciTech Connect

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

    2011-01-05

    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-Β 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 (τfc) 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 (τfc > 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.

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

    SciTech Connect

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

    2007-06-25

    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.

  9. A MAGNETOHYDRODYNAMIC MODEL FOCUSED ON THE CONFIGURATION OF MAGNETIC FIELD RESPONSIBLE FOR A SOLAR PENUMBRAL MICROJET

    SciTech Connect

    Magara, T.

    2010-05-20

    In order to understand the configuration of magnetic field producing a solar penumbral microjet that was recently discovered by Hinode, we performed a magnetohydrodynamic simulation reproducing a dynamic process of how that configuration is formed in a modeled solar penumbral region. A horizontal magnetic flux tube representing a penumbral filament is placed in a stratified atmosphere containing the background magnetic field that is directed in a relatively vertical direction. Between the flux tube and the background field there forms the intermediate region in which the magnetic field has a transitional configuration, and the simulation shows that in the intermediate region magnetic reconnection occurs to produce a clear jet-like structure as suggested by observations. The result that a continuous distribution of magnetic field in three-dimensional space gives birth to the intermediate region producing a jet presents a new view about the mechanism of a penumbral microjet, compared to a simplistic view that two field lines, one of which represents a penumbral filament and the other the background field, interact together to produce a jet. We also discuss the role of the intermediate region in protecting the structure of a penumbral filament subject to microjets.

  10. Equilibrium configuration of the 1u state of hydrogen molecular ion in a magnetic field.

    PubMed

    Song, Xuanyu; Gong, Cheng; Wang, Xiaofeng; Qiao, Haoxue

    2013-08-14

    Using the variational method based on the Gaussian basis set, the authors investigate the 1u state of hydrogen molecular ion in a non-parallel magnetic field with respect to the fixed molecular axis. At sufficiently small field strength, the equilibrium configuration prefers the perpendicular orientation, in which the (relative) orientation ? between the magnetic field and the molecular axis is 90. With increasing field strength, the orientation ? of the equilibrium configuration decreases, and is neither the parallel orientation nor the perpendicular orientation at field strength between 10(9) G and 2.35 10(10) G. Meanwhile, more and more configurations with large orientations become unstable with respect to the dissociation H + p. PMID:23947853

  11. Observations of improved confinement in field reversed configurations sustained by antisymmetric rotating magnetic fields

    SciTech Connect

    Guo, H.Y.; Hoffman, A.L.; Steinhauer, L.C.

    2005-06-15

    Rotating magnetic fields (RMF) have been employed to both form and sustain currents in field reversed configurations (FRC). A major concern about this method has been the fear of opening up magnetic field lines with even small ratios of vacuum RMF B{sub {omega}} to external confinement field B{sub e}. A recently proposed innovation was to use an antisymmetric arrangement of RMF, but vacuum calculations with full RMF penetration showed that very low values of B{sub {omega}}/B{sub e} would still be required to provide field-line closure. Recent comparisons of symmetric and antisymmetric RMF drive on the translation, confinement, and sustainment (TCS) facility [A. L. Hoffman, H. Y. Guo, J. T. Slough et al., Fusion Sci. Technol. 41, 92 (2002)] have shown strong improvements in the basic confinement properties of the FRCs when using antisymmetric drive, even with ratios of B{sub {omega}}/B{sub e} as high as 0.3. This is due to normal standard operation with only partial penetration of the RMF beyond the FRC separatrix. The uniform transverse RMF in vacuum is shielded by the conducting plasma, resulting in a mostly azimuthal field near the FRC separatrix with a very small radial component. Simple numerical calculations using analytical solutions for the partially penetrated antisymmetric RMF, superimposed on Grad-Shafranov solutions for the poloidal FRC fields, show good field-line closure for the TCS experimental conditions. The antisymmetric arrangement also leads to more efficient current drive and improved stabilization of rotational modes.

  12. Novel Approach to Construction Realistic Magnetic Field Configuration in the Lower Solar Atmosphere

    NASA Astrophysics Data System (ADS)

    Fedun, V.; Gent, F.; Erdelyi, R.

    2014-12-01

    Models of realistic magnetic field configurations, typical of the lower solar atmosphere, in magneto-hydrostatic equilibrium are analytically constructed. Systems incorporating open single and multiple flux tubes and closed magnetic loops can be combined to form magnetic structures that could even represent complex solar active regions.The developed model successfully spans the Interface Region of the solar atmosphere, from the photosphere up to the solar corona across the challenging transition region, while retaining physically valid plasma pressure, density and magnetic flux. Modelling magnetic structures can depict the main characteristics of solar intergranular lanes or active regions. HMI data can be used, as an initial magnetic field distribution,to construct a realistic magnetic field distribution. The model includes a number of free parameters, which makes the solution applicable to a variety of other physical problems, and it may therefore be of more general interest.

  13. Penetration and radial force balance in field-reversed configuration with large rotating magnetic field

    SciTech Connect

    Ohnishi, M.; Fukuhara, M.; Masaki, T.; Osawa, H.; Chikano, T.; Hugrass, W.

    2008-10-15

    A field-reversed configuration (FRC) is formed by applying a rotating magnetic field (RMF) much larger than the axial magnetic field to a cylindrical glass vacuum chamber filled with 10 Pa argon gas without a preionization. The FRC with the plasma density 2.2x10{sup 19} m{sup -3}, the temperature 8.0 eV, the separatrix length 0.45 m, and the separatrix radius 0.035 m is sustained for the notably long period of 40 ms. It is observed that the antenna current which produces the RMF is reduced by about half after the FRC is formed. The interaction between the plasma and the antenna circuit increases the antenna resistance and changes the inductance of the antenna so that the circuit becomes nonresonant. The RMF is sufficiently large to fully penetrate to the center during the period and drive the current with a rigid rotor profile. The RMF is shown to play a major role in sustaining the plasma pressure.

  14. Applied magnetic field design for the field reversed configuration compression heating experiment

    NASA Astrophysics Data System (ADS)

    Domonkos, M. T.; Amdahl, D.; Camacho, J. F.; Coffey, S. K.; Degnan, J. H.; Delaney, R.; Frese, M.; Gale, D.; Grabowski, T. C.; Gribble, R.; Intrator, T. P.; McCullough, J.; Montano, N.; Robinson, P. R.; Wurden, G.

    2013-04-01

    Detailed calculations of the formation, guide, and mirror applied magnetic fields in the FRC compression-heating experiment (FRCHX) were conducted using a commercially available generalized finite element solver, COMSOL Multiphysics. In FRCHX, an applied magnetic field forms, translates, and finally captures the FRC in the liner region sufficiently long to enable compression. Large single turn coils generate the fast magnetic fields necessary for FRC formation. Solenoidal coils produce the magnetic field for translation and capture of the FRC prior to liner implosion. Due to the limited FRC lifetime, liner implosion is initiated before the FRC is injected, and the magnetic flux that diffuses into the liner is compressed. Two-dimensional axisymmetric magnetohydrodynamic simulations using MACH2 were used to specify optimal magnetic field characteristics, and this paper describes the simulations conducted to design magnetic field coils and compression hardware for FRCHX. This paper presents the vacuum solution for the magnetic field.

  15. Applied magnetic field design for the field reversed configuration compression heating experiment.

    PubMed

    Domonkos, M T; Amdahl, D; Camacho, J F; Coffey, S K; Degnan, J H; Delaney, R; Frese, M; Gale, D; Grabowski, T C; Gribble, R; Intrator, T P; McCullough, J; Montano, N; Robinson, P R; Wurden, G

    2013-04-01

    Detailed calculations of the formation, guide, and mirror applied magnetic fields in the FRC compression-heating experiment (FRCHX) were conducted using a commercially available generalized finite element solver, COMSOL Multiphysics(). In FRCHX, an applied magnetic field forms, translates, and finally captures the FRC in the liner region sufficiently long to enable compression. Large single turn coils generate the fast magnetic fields necessary for FRC formation. Solenoidal coils produce the magnetic field for translation and capture of the FRC prior to liner implosion. Due to the limited FRC lifetime, liner implosion is initiated before the FRC is injected, and the magnetic flux that diffuses into the liner is compressed. Two-dimensional axisymmetric magnetohydrodynamic simulations using MACH2 were used to specify optimal magnetic field characteristics, and this paper describes the simulations conducted to design magnetic field coils and compression hardware for FRCHX. This paper presents the vacuum solution for the magnetic field. PMID:23635196

  16. Analysis of payload bay magnetic fields due to dc power multipoint and single point ground configurations

    NASA Technical Reports Server (NTRS)

    Lawton, R. M.

    1976-01-01

    An analysis of magnetic fields in the Orbiter Payload Bay resulting from the present grounding configuration (structure return) was presented and the amount of improvement that would result from installing wire returns for the three dc power buses was determined. Ac and dc magnetic fields at five points in a cross-section of the bay are calculated for both grounding configurations. Y and Z components of the field at each point are derived in terms of a constant coefficient and the current amplitude of each bus. The dc loads assumed are 100 Amperes for each bus. The ac noise current used is a spectrum 6 db higher than the Orbiter equipment limit for narrowband conducted emissions. It was concluded that installing return wiring to provide a single point ground for the dc Buses in the Payload Bay would reduce the ac and dc magnetic field intensity by approximately 30 db.

  17. Formation of a field reversed configuration for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl; Qerushi, Artan; Tahsiri, Hooshang

    2006-02-07

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  18. Formation of a field reversed configuration for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl; Qerushi, Artan; Tahsiri, Hooshang

    2007-02-20

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  19. Formation of a field reversed configuration for magnetic and electrostatic confinement of plasma

    DOEpatents

    Rostoker, Norman; Binderbauer, Michl

    2003-12-16

    A system and method for containing plasma and forming a Field Reversed Configuration (FRC) magnetic topology are described in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. Further, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. In this configuration, ions and electrons may have adequate density and temperature so that upon collisions they are fused together by nuclear force, thus releasing fusion energy. Moreover, the fusion fuel plasmas that can be used with the present confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels.

  20. Particle Diffusion in Chaotic Magnetic Fields Generated by Asymmetric Current Configurations

    NASA Astrophysics Data System (ADS)

    Ram, A. K.; Dasgupta, B.

    2008-12-01

    The observed cross-field diffusion of charged particles in cosmic rays is assumed to be due to the chaotic nature of the interplanetary/intergalactic magnetic fields. Among the classic works on this subject have been those of Parker [1] and Jokipii [2]. Parker considered the passage of cosmic ray particles and energetic solar particles in a large scale magnetic field containing small scale irregularities. In the context of cosmic ray propagation, Jokipii considered a small fluctuating component, added on to a uniform magnetic field, to study the spatial transport of particles. In these studies the irregular component of the magnetic field is prescribed in an ad hoc fashion. In contrast, we consider asymmetric, nonlinear, steady-state magnetic fields, in three spatial dimensions, generated by currents flowing in circular loops and straight lines [3]. These magnetic fields are completely deterministic and, for certain range of parameters, chaotic. We will present analytical and numerical studies on the spatial characteristics of these fields. The motion of charged particles in the nonlinear and chaotic magnetic fields is determined using the Lorentz equation. A particle moving in a deterministic chaotic magnetic field superposed on a uniform background magnetic field is found to undergo spatial transport. This shows that chaotic magnetic fields generated by simple current configurations can produce cross-field diffusion. A detailed analysis of particle motion and diffusion along with application to space plasmas will be presented. [1] E.N. Parker, Planet. Space Sci. 13, 9 (1965). [2] J.R. Jokipii, Astrophys. J. 146, 480 (1966), and J.R. Jokipii, Astrophys. J. 149, 405 (1967). [3] A.K. Ram and B. Dasgupta, Eos Trans. AGU 87 (52), Fall Meet. Suppl. Abstract NG31B-1593 (2006); and Eos Trans. AGU 88 (52), Fall Meet. Suppl. Abstract NG21B-0522 (2007).

  1. Transport of Positrons in Arbitrary Configurations of Electric and Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Petrovic, Zoran; Dujko, Sasa; Bankovic, Ana; Marjanovic, Srdjan; White, Ron

    2015-05-01

    In realistic geometries in gas filled positron traps electric and magnetic fields may not be always along the same axis or perpendicular. It has been shown for electrons that for arbitrary angles a wide variety of effects may occur. Most importantly controlling the angle may control diffusion and thus affect strongly the losses. We have performed calculations of transport coefficients for molecular hydrogen and carbon-tetra-fluoride. Monte Carlo technique was supplemented by novel development of solution of Boltzmann equation for arbitrary configuration of electric and magnetic fields. Both flux and bulk variants of transport coefficients were considered. It was found that it is possible to control diffusion and hence diffusion losses in a wide range of values by varying the angle of magnetic field. In addition it was found that the configuration will affect the mean energy and hence the losses due to Ps formation. The magnitude of effects depends strongly on shapes of the cross sections for positron scattering.

  2. Equilibrium configurations of Vlasov plasmas carrying a current component along an external magnetic field.

    NASA Technical Reports Server (NTRS)

    Kan, J. R.

    1972-01-01

    A model of equilibrium configurations of Vlasov plasmas is considered which represents a combination of the models of Harris (1962) and Nicholson (1963). These plasma configurations carry a current component along an external magnetic field. The considered slab model contains a diamagnetic current and a field-aligned current for an arbitrary ratio of particle pressure to magnetic pressure of the applied constant field. For a fixed pressure ratio and field-aligned current, the model admits a family of equilibrium solutions in which the diamagnetic currents range from zero to a maximum value. The amount of diamagnetic current flowing in a machine depends on the width of the machine, the field-aligned current and other plasma parameters.

  3. Experimental results with an optimized magnetic field configuration for JET breakdown

    NASA Astrophysics Data System (ADS)

    Albanese, R.; Maviglia, F.; Lomas, P. J.; Manzanares, A.; Mattei, M.; Neto, A.; Rimini, F. G.; de Vries, P. C.; EFDA Contributors, JET

    2012-12-01

    Experiments and modelling have been carried out to optimize the magnetic field null during breakdown at JET. Such optimization may prove to be essential for reliable plasma initiation at low voltages, e.g. in ITER where the value of the electric field available will be limited to 0.33 V m-1. A two-dimensional FEM electromagnetic model has been employed to predict the stray field configuration during JET breakdown. This model includes the active poloidal field circuits, a description of the passive structure and the JET magnetic circuit. In particular, the model includes the gap at the top of the iron circuit (but not at the bottom), which introduces a perturbing field, with radial and vertical components, not previously considered. A number of experiments were run using the optimized magnetic null configuration, allowing one to achieve a more robust breakdown at a low electric field. The model calculation to adjust the magnetic null position was validated using the recordings from a fast visible camera. The optimized position and dynamics of the plasma start lead to a smoother behaviour of the JET radial field control system, far from the amplifier limits. Finally, an important indication was obtained on the precision needed for the active current measurements during the low electric field breakdown relevant from the perspective of the ITER real-time acquisition system.

  4. Particle Confinement in Axisymmetric Poloidal Magnetic Field Configurations with Zeros of B: Methodological Note

    SciTech Connect

    Arsenin, V.V.; Skovoroda, A.A.

    2005-12-15

    Collisionless particle confinement in axisymmetric configurations with magnetic field nulls is analyzed. The existence of an invariant of motion--the generalized azimuthal momentum--makes it possible to determine in which of the spatial regions separated by magnetic separatrices passing through the magnetic null lines the particle occurs after it leaves the vicinity of a magnetic null line. In particular, it is possible to formulate a sufficient condition for the particle not to escape through the separatrix from the confinement region to the external region. In the configuration under analysis, the particles can be lost from a separatrix layer with a thickness on the order of the Larmor radius because of the nonconservation of the magnetic moment {mu}. In this case, the variations in {mu} are easier to describe in a coordinate system associated with the magnetic surfaces. An analysis is made of the applicability of expressions for the single-pass change {delta}{mu} in the magnetic moment that were obtained in different magnetic field models for a confinement system with a divertor (such that there is a circular null line)

  5. Radial expansion of an ideal MHD configuration and the temporal development of the magnetic field. [in magnetic cloud velocity profiles

    NASA Technical Reports Server (NTRS)

    Farrugia, C. J.; Osherovich, V. A.; Burlaga, L. F.; Lepping, R. P.; Freeman, M. P.

    1992-01-01

    We study the free radial expansion of a 3-component magnetic configuration. The emphasis of this paper is on the behavior of a field undergoing non-self-similar expansion. Comparing our results with the evolution of a magnetic configuration expanding self-similarly, we find that self-similar expansion appears as the asymptotic limit (with time) of the general case. Using a model field we show that a non-self-similar velocity profile need not have a strict monotonic decrease with time.

  6. 3D Magnetic Field Configuration of the 2006 December 13 Flare Extrapolated with the Optimization Method

    NASA Astrophysics Data System (ADS)

    Guo, Y.; Ding, M. D.; Wiegelmann, T.; Li, H.

    2008-06-01

    The photospheric vector magnetic field of the active region NOAA 10930 was obtained with the Solar Optical Telescope (SOT) on board the Hinode satellite with a very high spatial resolution (about 0.3''). Observations of the two-ribbon flare on 2006 December 13 in this active region provide us a good sample to study the magnetic field configuration related to the occurrence of the flare. Using the optimization method for nonlinear force-free field (NLFFF) extrapolation proposed by Wheatland et al. and recently developed by Wiegelmann, we derive the three-dimensional (3D) vector magnetic field configuration associated with this flare. The general topology can be described as a highly sheared core field and a quasi-potential envelope arch field. The core field clearly shows some dips supposed to sustain a filament. Free energy release in the flare, calculated by subtracting the energy contained in the NLFFF and the corresponding potential field, is 2.4 × 1031 ergs, which is ~2% of the preflare potential field energy. We also calculate the shear angles, defined as the angles between the NLFFF and potential field, and find that they become larger at some particular sites in the lower atmosphere, while they become significantly smaller in most places, implying that the whole configuration gets closer to the potential field after the flare. The Ca II H line images obtained with the Broadband Filter Imager (BFI) of the SOT and the 1600 Å images with the Transition Region and Coronal Explorer (TRACE) show that the preflare heating occurs mainly in the core field. These results provide evidence in support of the tether-cutting model of solar flares.

  7. Magnetic shielding properties of high- Tc superconducting hollow cylinders: model combining experimental data for axial and transverse magnetic field configurations

    NASA Astrophysics Data System (ADS)

    Fagnard, J.-F.; Dirickx, M.; Ausloos, M.; Lousberg, G.; Vanderheyden, B.; Vanderbemden, Ph

    2009-10-01

    Magnetic shielding efficiency was measured on high- Tc superconducting hollow cylinders subjected to either an axial or a transverse magnetic field in a large range of field sweep rates, dBapp/dt. The behaviour of the superconductor was modelled in order to reproduce the main features of the field penetration curves by using a minimum number of free parameters suitable for both magnetic field orientations. The field penetration measurements were carried out on Pb-doped Bi-2223 tubes at 77 K by applying linearly increasing magnetic fields with a constant sweep rate ranging between 10 µT s-1 and 10 mT s-1 for both directions of the applied magnetic field. The experimental curves of the internal field versus the applied field, Bin(Bapp), show that, at a given sweep rate, the magnetic field for which the penetration occurs, Blim, is lower for the transverse configuration than for the axial configuration. A power law dependence with large exponent, n', is found between Blim and dBapp/dt. The values of n' are nearly the same for both configurations. We show that the main features of the curves Bin(Bapp) can be reproduced using a simple 2D model, based on the method of Brandt, involving a E(J) power law with an n-exponent and a field-dependent critical current density, Jc(B), (following the Kim model: Jc = Jc0(1+B/B1)-1). In particular, a linear relationship between the measured n'-exponents and the n-exponent of the E(J) power law is suggested by taking into account the field dependence of the critical current density. Differences between the axial and the transverse shielding properties can be simply attributed to demagnetizing fields.

  8. H{sub 3}{sup +} molecular ion in a magnetic field: Linear parallel configuration

    SciTech Connect

    Turbiner, A. V.; Guevara, N. L.; Lopez Vieyra, J. C.

    2007-05-15

    A detailed study of the ground state of the H{sub 3}{sup +} molecular ion in linear configuration, parallel to the magnetic field direction, and its low-lying {sigma}, {pi}, and {delta} states is carried out for magnetic fields B=0-4.414x10{sup 13} G in the Born-Oppenheimer approximation. The variational method is employed with a single trial function which includes electronic correlation in the form exp({gamma}r{sub 12}), where {gamma} is a variational parameter. It is shown that the quantum numbers of the state of the lowest total energy (ground state) depend on the magnetic field strength. The ground state evolves from the spin-singlet {sup 1}{sigma}{sub g} state for weak magnetic fields B(less-or-similar sign)5x10{sup 8} G to a weakly bound spin-triplet {sup 3}{sigma}{sub u} state for intermediate fields and, eventually, to a spin-triplet {sup 3}{pi}{sub u} state for 5x10{sup 10}(less-or-similar sign)B(less-or-similar sign)4.414x10{sup 13} G. Local stability of the linear parallel configuration with respect to possible small deviations is checked.

  9. Investigation and optimization of the magnetic field configuration in high-power impulse magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Yu, He; Meng, Liang; Szott, Matthew M.; McLain, Jake T.; Cho, Tae S.; Ruzic, David N.

    2013-08-01

    An effort to optimize the magnetic field configuration specifically for high-power impulse magnetron sputtering (HiPIMS) was made. Magnetic field configurations with different field strengths, race track widths and race track patterns were designed using COMSOL. Their influence on HiPIMS plasma properties was investigated using a 36 cm diameter copper target. The I-V discharge characteristics were measured. The temporal evolution of electron temperature (Te) and density (ne) was studied employing a triple Langmuir probe, which was also scanned in the whole discharge region to characterize the plasma distribution and transport. Based on the studies, a closed path for electrons to drift along was still essential in HiPIMS in order to efficiently confine electrons and achieve a high pulse current. Very dense plasmas (1019-1020 m-3) were generated in front of the race tracks during the pulse, and expanded downstream afterwards. As the magnetic field strength increased from 200 to 800 G, the expansion became faster and less isotropic, i.e. more directional toward the substrate. The electric potential distribution accounted for these effects. Varied race track widths and patterns altered the plasma distribution from the target to the substrate. A spiral-shaped magnetic field design was able to produce superior plasma uniformity on the substrate in addition to improved target utilization.

  10. Superposed epoch analysis of pressure and magnetic field configuration changes in the plasma sheet

    NASA Technical Reports Server (NTRS)

    Kistler, L. M.; Baumjohann, W.; Nagai, T.; Mobius, E.

    1993-01-01

    Using data from 41 substorm events in the near-Earth magnetotail, we have combined plasma, energetic ion, and magnetic field data from the AMPTE/IRM spacecraft to perform a superposed epoch analysis of changes in the total pressure and in the magnetic field configuration as a function of time relative to substorm onset. Unloading is evident in the total pressure profile; the pressure decreases by about 20 percent. Pressure changes during the growth phase are not as uniform for the different substorms as the pressure changes during the expansion phase. To study changes in the magnetic field configuration, we have determined the development of the plasma pressure profiles in z for an average of data from 15 to 19 R(E). At substorm onset, the field line dipolarization begins on the innermost field lines and then progresses to the outer field lines. The field lines map the closest to the Earth about 45 min after substorm onset, and then begin to stretch out again during the recovery phase of the substorm.

  11. A configurable component-based software system for magnetic field measurements

    SciTech Connect

    Nogiec, J.M.; DiMarco, J.; Kotelnikov, S.; Trombly-Freytag, K.; Walbridge, D.; Tartaglia, M.; /Fermilab

    2005-09-01

    A new software system to test accelerator magnets has been developed at Fermilab. The magnetic measurement technique involved employs a single stretched wire to measure alignment parameters and magnetic field strength. The software for the system is built on top of a flexible component-based framework, which allows for easy reconfiguration and runtime modification. Various user interface, data acquisition, analysis, and data persistence components can be configured to form different measurement systems that are tailored to specific requirements (e.g., involving magnet type or test stand). The system can also be configured with various measurement sequences or tests, each of them controlled by a dedicated script. It is capable of working interactively as well as executing a preselected sequence of tests. Each test can be parameterized to fit the specific magnet type or test stand requirements. The system has been designed with portability in mind and is capable of working on various platforms, such as Linux, Solaris, and Windows. It can be configured to use a local data acquisition subsystem or a remote data acquisition computer, such as a VME processor running VxWorks. All hardware-oriented components have been developed with a simulation option that allows for running and testing measurements in the absence of data acquisition hardware.

  12. Design of magnetic field configuration for controlled discharge properties in highly ionized plasma

    NASA Astrophysics Data System (ADS)

    Alami, Jones; Stranak, Vitezslav; Herrendorf, Ann-Pierra; Hubicka, Zdenek; Hippler, Rainer

    2015-08-01

    In the present article, the effect of magnetic field design on electron and ion properties in both a metallic Ti/Ar and a reactive Ti/Ar + O2 high power impulse magnetron sputtering (HiPIMS) discharges is investigated. For the purpose, a variable magnetron with defined imbalance and geometrical coefficients K and {{K}\\text{G}} , respectively, was utilized. The electron density, the mean electron energy, the plasma potential, and the floating potential were determined by employing time-resolved Langmuir probe measurements, for four specified magnetic field configurations. Mass spectroscopy was used in order to determine the energy distribution function of metal (Ti+ , Ti2+) and gaseous (Ar+ , Ar2+ , O+ , O2+ ) ions. Analysis of the measured data shows that the magnetic field design dramatically affects the charged particles energy- and spatial-distribution, causing a change in the plasma properties. It is concluded that a well-determined configuration of the magnetic field is necessary in order to insure discharge stability and reproducibility.

  13. Non-thermal Plasmas Around Massive Black Holes: Collective Modes, Ring Configurations and Magnetic Field Generation

    NASA Astrophysics Data System (ADS)

    Coppi, B.

    2013-10-01

    The discovered gamma-ray bubbles emanating from the center of Our Galaxy are a new motivation to develop theories for large scale structures in the Universe in terms of plasmas for which electromagnetic interactions are no less important than the relevant (e.g. density wave theory of spirals) gravitational interactions. Moreover, considering the observed emission spectra, the particle distributions in phase space cannot be represented by isotropic Maxwellian in significant cases. The consequent theory of plasmas surrounding rotating massive black holes has led to identify new stationary plasma and field configurations (in particular Solitary Rings) and modes, emerging from conventional (currentless) disks, that depend on the existence of temperature anisotropies. These modes, which produce outward transport of angular momentum at a significant rate, involve large amplifications of a seed magnetic field. In the related (by the envisioned non-linear mode evolution) stationary configurations, without a seed magnetic field, the field energy densities are of the order of the particle thermal energy densities. Thus a clear sequence of processes for the generation of magnetic fields in the Universe is identified. US DOE partly sponsored.

  14. Magnetic flux trapping during field reversal in the formation of a field-reversed configuration

    NASA Astrophysics Data System (ADS)

    Steinhauer, Loren C.

    1985-11-01

    The flow of plasma and magnetic flux toward a wall is examined in a slab geometry where the magnetic field is parallel to the wall. Magnetohydrodynamic (MHD) flow with a quasisteady approximation is assumed that reduces the problem to three coupled ordinary differential equations. The calculated behavior shows that a thin current sheath is established at the wall in which a variety of phenomena appear, including significant resistive heating and rapid deceleration of the plasma flow. The sheath physics determines the speed at which flux and plasma flow toward the wall. The model has been applied to the field-reversal phase of a field-reversed theta pinch, during which the reduced magnetic field near the wall drives an outward flow of plasma and magnetic flux. The analysis leads to approximate expressions for the instantaneous flow speed, the loss of magnetic flux during the field reversal phase, the integrated heat flow to the wall, and the highest possible magnetic flux retained after reversal. Predictions from this model are compared with previous time-dependent MHD calculations and with experimental results from the TRX-1 [Proceedings of the 4th Symposium on the Physics and Technology of Compact Toroids, 27-29 October 1981 (Lawrence Livermore National Laboratory, Livermore, CA, 1982), p. 61] and TRX-2 [Proceedings of the 6th U.S. Symposium on Compact Toroid Research, 20-23 February, 1984 (Princeton Plasma Physics Laboratory, Princeton, NJ, 1984), p. 154] experiments.

  15. Plasma-dominated magnetic field configurations for the magnetosphere of Uranus

    NASA Technical Reports Server (NTRS)

    Ip, A. K.; Voigt, G.-H.

    1985-01-01

    There is significant indirect evidence that the planet Uranus possesses a magnetic field. This evidence is based on the observation of hydrogen Lyman alpha emission from Uranus with the aid of the International Ultraviolet Explorer (IUE) spacecraft. The detection of water ice on the Uranian moons led Cheng (1984) to suggest that charged particle sputtering of the icy satellites could provide a significant internal source of oxygen ions and protons to the Uranian magnetosphere. Cheng concluded that this mechanism would predict aurorae around both magnetic poles of Uranus. Cheng's idea of the presence of a continuous internal plasma supply to the Uranian magnetosphere is further pursued in the present investigation. Questions are considered regarding the evolution of Uranus' magnetosphere from a vacuum configuration toward a plasma pressure dominated equilibrium configuration, taking into account the amount of the thermal plasma pressure as a free parameter.

  16. MAGNETIC FIELD CONFIGURATION AT THE GALACTIC CENTER INVESTIGATED BY WIDE-FIELD NEAR-INFRARED POLARIMETRY: TRANSITION FROM A TOROIDAL TO A POLOIDAL MAGNETIC FIELD

    SciTech Connect

    Nishiyama, Shogo; Yoshikawa, Tatsuhito; Nagata, Tetsuya; Hatano, Hirofumi; Nagayama, Takahiro; Tamura, Motohide; Matsunaga, Noriyuki; Suenaga, Takuya; Hough, James H.; Sugitani, Koji; Kato, Daisuke

    2010-10-10

    We present a large-scale view of the magnetic field (MF) in the central 2{sup 0} x 2{sup 0} region of our Galaxy. The polarization of point sources has been measured in the J, H, and K{sub S} bands using the near-infrared polarimetric camera SIRPOL on the 1.4 m Infrared Survey Facility telescope. Comparing the Stokes parameters between high extinction stars and relatively low extinction ones, we obtain polarization originating from magnetically aligned dust grains in the central few hundred parsecs of our Galaxy. We find that near the Galactic plane, the MF is almost parallel to the Galactic plane (i.e., toroidal configuration), but at high Galactic latitudes (|b | >0.{sup 0}4) the field is nearly perpendicular to the plane (i.e., poloidal configuration). This is the first detection of a smooth transition of the large-scale MF configuration in this region.

  17. The Relationship Among Magnetic Field Configuration, Penumbral Size, and Evershed Flow Speed

    NASA Astrophysics Data System (ADS)

    Deng, Na; Shimizu, T.; Choudhary, D.

    2010-05-01

    Recent observations (e.g., Wang et al. 2004; Deng et al. 2005) have shown that there is a sudden penumbral decay associated with major flares during which the overall magnetic field inclination in penumbra changes due to magnetic reconnection. We propose that the size (i.e., length) of sunspot penumbra is related to the localized magnetic field configuration. In order to test this hypothesis, we study 11 sunspots close to disk center with different sizes, which were observed by Hinode/SOT at the late phase of solar cycle 23. We notice that even for typical alpha sunspots near the disc center, the penumbral length is different in different sectors in the same spot. Since the Evershed flow is coupled with penumbra, we also study the properties of Evershed flow, such as its speed, at different location of a sunspot. The SP data is used to study the magnetic field parameters (e.g., strength, inclination) in different penumbral sectors that show distinct penumbral length. The Evershed flow is measured both by Doppler shift from SP observation and by Local Correlation Tracking based on time series of BFI data. We aim to find the relationship among magnetic field topology, penumbral size, and Evershed flow speed.

  18. Inductrack magnet configuration

    DOEpatents

    Post, Richard Freeman

    2003-12-16

    A magnet configuration comprising a pair of Halbach arrays magnetically and structurally connected together are positioned with respect to each other so that a first component of their fields substantially cancels at a first plane between them, and a second component of their fields substantially adds at this first plane. A track of windings is located between the pair of Halbach arrays and a propulsion mechanism is provided for moving the pair of Halbach arrays along the track. When the pair of Halbach arrays move along the track and the track is not located at the first plane, a current is induced in the windings and a restoring force is exerted on the pair of Halbach arrays.

  19. Inductrack magnet configuration

    DOEpatents

    Post, Richard Freeman

    2003-10-14

    A magnet configuration comprising a pair of Halbach arrays magnetically and structurally connected together are positioned with respect to each other so that a first component of their fields substantially cancels at a first plane between them, and a second component of their fields substantially adds at this first plane. A track of windings is located between the pair of Halbach arrays and a propulsion mechanism is provided for moving the pair of Halbach arrays along the track. When the pair of Halbach arrays move along the track and the track is not located at the first plane, a current is induced in the windings and a restoring force is exerted on the pair of Halbach arrays.

  20. Analysis and Modeling of Coronal Holes Observed by CORONAS-1. 1; Morphology and Magnetic Field Configuration

    NASA Technical Reports Server (NTRS)

    Obridko, Vladmir; Formichev, Valery; Kharschiladze, A. F.; Zhitnik, Igor; Slemzin, Vladmir; Hathaway, David H.; Wu, Shi T.

    1998-01-01

    Two low-latitude coronal holes observed by CORONAS-1 in April and June 1994 are analyzed together with magnetic field measurements obtained from Wilcox and Kitt Peak Solar Observatories. To estimate the comparable temperature of these two coronal holes, the YOHKOH observations are also utilized. Using this information, we have constructed three-dimensional magnetic field lines to illustrate the geometrical configuration of these coronal holes. The calculated synoptic maps are used to determine the existence of closed and open field regions of the hole. Finally, we have correlated the characteristics of two coronal holes with observed solar wind speed. We found that the brighter coronal hole has high speed solar wind, and the dimmer coronal hole has low speed solar wind.

  1. Magnetic field configuration and field-aligned acceleration of energetic ions during substorm onsets

    NASA Astrophysics Data System (ADS)

    Korth, A.; Pu, Z. Y.

    2001-09-01

    In this paper, we present an interpretation of the observed field-aligned acceleration events measured by GEOS-2 near the night-side synchronous orbit at substorm onsets (Chen et al., 2000). We show that field-aligned acceleration of ions (with pitch angle asymmetry) is closely related to strong short-lived electric fields in the Ey direction. The acceleration is associated with either rapid dipolarization or further stretching of local magnetic field lines. Theoretical analysis suggests that a centrifugal mechanism is a likely candidate for the parallel energization. Equatorward or anti-equatorward energization occurs when the tail current sheet is thinner tailward or earthward of the spacecraft, respectively. The magnetic field topology leading to anti-equatorward energization corresponds to a situation where the near-Earth tail undergoes further compression and the inner edge of the plasma sheet extends inwards as close as the night-side geosynchronous altitudes.

  2. Exotic H{sub 3}{sup 2+} ion in a strong magnetic field: Linear configuration

    SciTech Connect

    Turbiner, A.V.; Lopez Vieyra, J.C.; Guevara, N.L.

    2005-08-15

    An accurate study of the lowest 1{sigma}{sub g} and the low-lying excited 1{sigma}{sub u},1{pi}{sub u,g},1{delta}{sub g,u} electronic states of the exotic molecular ion H{sub 3}{sup 2+} in linear configuration parallel to a magnetic field is carried out. The magnetic field ranges from 10{sup 10} G up to 4.414x10{sup 13} G, where nonrelativistic considerations are justified. The variational method is exploited and the same trial function is used for different magnetic fields. It is shown that the states of positive z parity 1{sigma}{sub g},1{pi}{sub u},1{delta}{sub g} are bound states of the H{sub 3}{sup 2+} exotic ion: the state 1{sigma}{sub g} exists for magnetic fields B > or approx. 10{sup 10} G, and the states 1{pi}{sub u},1{delta}{sub g} exist for B > or approx. 2.35x10{sup 10} G. It is demonstrated that for magnetic fields B > or approx. 2.35x10{sup 12} G the potential energy surface well corresponding to the 1{sigma}{sub g} state contains at least one longitudinal vibrational state. It is shown that the negative z-parity states 1{sigma}{sub u},1{pi}{sub g},1{delta}{sub u} are pure repulsive in the whole range of magnetic fields studied, B=10{sup 10}-4.414x10{sup 13} G.

  3. Ion and electron cyclotron wall conditioning in stellarator and tokamak magnetic field configuration on WEGA

    SciTech Connect

    Wauters, T.; Louche, F.; Urlings, P.

    2014-02-12

    Discharge wall conditioning is an effective tool to improve plasma performance in tokamaks and stellarators. RF Discharge Conditioning (RFDC) techniques are envisaged for use during operational campaigns on superconducting devices like the ITER tokamak and W7-X stellarator, as alternative to DC Glow Discharge Conditioning which is inefficient in presence of magnetic fields. This contribution investigates RFDC in both the ion and electron cyclotron range of frequencies (ICRF and ECRF) on the WEGA device (Max-Planck-Institute for Plasma Physics, Greifswald, Germany) as preparation for W7-X operation. ECRF discharges produced by localised absorption of RF power at EC resonance layers suffer from poor radial discharge homogeneity in the tokamak vacuum magnetic field configuration, severely limiting the plasma wetted wall areas and consequently the conditioning efficiency. The non-localised production of ICRF discharges by collisional RF power absorption features much improved discharge homogeneity making Ion Cyclotron Wall Conditioning (ICWC) the favoured RFDC technique for superconducting tokamaks. RFDC with the stellarator vacuum magnetic field needs to aim at sufficient plasma densities at and outside the last closed flux surface (LCFS), maximising the convective plasma flux along the open field lines to the wall. Whereas for ICRF discharges this condition is easily fulfilled, on WEGA for He-ECRF discharges this could be achieved as well by off axis heating close to the LCFS. In stellarator magnetic field configuration it is found that He-ICWC for wall desaturation is at least one order of magnitude more efficient than He-ECWC. Novel ECWC methods are proposed that can decrease this efficiency gap with ICWC to a factor 2-3. The efficiency difference is less pronounced in case of H{sub 2}-ICWC and ECWC for isotopic exchange.

  4. Motion of charged particles in magnetic fields created by symmetric configurations of wires

    NASA Astrophysics Data System (ADS)

    Aguirre, Jacobo; Luque, Alejandro; Peralta-Salas, Daniel

    2010-05-01

    In this paper we study the motion of a charged particle in the presence of a magnetic field created by three different systems of wires: an infinite rectilinear filament, a circular wire and the union of both. In the first case we prove that the equations of motion are Liouville integrable and we provide a complete description of the trajectories, which turn out to be of helicoidal type. In the case of the circular wire we study some restricted motions and we show that there is a trapping region similar to the Van Allen inner radiation belt in the Earth magnetosphere. We prove the existence of quasi-periodic orbits using Mosers twist theorem, and the existence of scattering trajectories using differential inequalities. We also provide numerical evidence of Hamiltonian chaos and chaotic scattering by computing several Poincar sections, Lyapunov exponents, fractal basins and their fractal dimensions. A similar study is done for the third system, although quasi-periodic orbits are proved to exist only under certain (perturbative) assumptions. From the viewpoint of the applications we propose a magnetic trap based on these configurations. Furthermore, the circular wire system can be interpreted as a simplified model of the levitated magnetic dipole-one of the recent proposals to confine a hot plasma for fusion power generation-and hence our work provides a verification of confinement and quasi-periodicity, beyond the adiabatic approximation, for this plasma system. Apart from contributing to the rigorous theory of the motion of charges in magnetic fields, this paper illustrates that very simple magnetic configurations can give rise to complicated, even chaotic trajectories, thus posing the question of how the complexity of magnetic lines affects the complexity of particle motions.

  5. Effect of magnetic field configuration on the multiply charged ion and plume characteristics in Hall thruster plasmas

    SciTech Connect

    Kim, Holak; Lim, Youbong; Choe, Wonho Park, Sanghoo; Seon, Jongho

    2015-04-13

    Multiply charged ions and plume characteristics in Hall thruster plasmas are investigated with regard to magnetic field configuration. Differences in the plume shape and the fraction of ions with different charge states are demonstrated by the counter-current and co-current magnetic field configurations, respectively. The significantly larger number of multiply charged and higher charge state ions including Xe{sup 4+} are observed in the co-current configuration than in the counter-current configuration. The large fraction of multiply charged ions and high ion currents in this experiment may be related to the strong electron confinement, which is due to the strong magnetic mirror effect in the co-current magnetic field configuration.

  6. Onset and Saturation of Ion Heating by Odd-parity Rotating-magnetic-fields in a Field-reversed Configuration

    SciTech Connect

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

    2005-11-01

    Heating of figure-8 ions by odd-parity rotating magnetic fields (RMFο) applied to an elongated field-reversed configuration (FRC) is investigated. The largest energy gain occurs at resonances (s ≡ ω(sub)R/ω) of the RMFο frequency, ω(sub)R, with the figure-8 orbital frequency, ω, and is proportional to s^2 for s – even resonances and to s for s – odd resonances. The threshold for the transition from regular to stochastic orbits explains both the onset and saturation of heating. The FRC magnetic geometry lowers the threshold for heating below that in the tokamak by an order of magnitude.

  7. Preparing to compress a Field Reversed Configuration target for Magnetized Target Fusion

    NASA Astrophysics Data System (ADS)

    Intrator, T. P.; Wurden, G. A.; Renneke, R.; Dorf, L. A.; Farrell, M.; Gray, T. K.; Hsu, S. C.; Lynn, A. G.; Gilmore, M.; Grabowski, C.; Ruden, E. L.; Degnan, J.; Awe, T.; Siemon, R.

    2006-10-01

    We summarize the our physics motivation for magnetized (MTF) target fusion and outline our engineering progress. A high pressure field reversed configuration (FRC) is shown that suits the MTF target and physics premises. Adiabatic MTF plasma compression should fall between magnetic and inertial fusion conditions. The small theta pinch FRC + Liner experiment (FRX-L) is designed to attain sufficient lifetime for MTF, at high pressure, with minimum pulsed power infrastructure. Small size begets large toroidal electric field for the formation FRC and initial shock heating followed by additional desirable ohmic heating prior to translation. Anomalously large resistivity is observed. FRX-L has demonstrated high target FRC plasma pressure (T>300 eV, ne> 5x10^22 m-3) of 20-30 atmospheres. Design and implementation details are shown for a series of FRC translation and implosion on plasma experiments.

  8. A first look into the magnetic field configuration of prominence threads using spectropolarimetric data

    NASA Astrophysics Data System (ADS)

    Orozco Surez, D.; Asensio Ramos, A.; Trujillo Bueno, J.

    2014-01-01

    We show preliminary results of an ongoing investigation aimed at determining the configuration of the magnetic field vector in the threads of a quiescent hedgerow solar prominence using high-spatial resolution spectropolarimetric observations taken in the He I 1083.0 nm multiplet. The data consist of a two-dimensional map of a quiescent hedgerow prominence showing vertical threads. The observations were obtained with the Tenerife Infrared Polarimeter attached to the German Vacuum Tower Telescope at the Observatorio del Teide (Spain). The He I 1083.0 nm Stokes signals are interpreted with an inversion code, which takes into account the key physical processes that generate and/or modify circular and linear polarization signals in the He I 1083.0 nm triplet: the Zeeman effect, anisotropic radiation pumping, and the Hanle effect. We present initial results of the inversions, i.e, the strength and orientation of the magnetic field vector along the prominence and in prominence threads.

  9. Configuration of the magnetic field and reconstruction of Pangaea in the Permian period.

    PubMed

    Westphal, M

    1977-05-12

    The virtual geomagnetic poles of Laurasia and Gondwanaland in the Carboniferous and Permian periods diverge significantly when these continents are reassembled according to the fit calculated by Bullard et al. Two interpretations have been offered: Briden et al. explain these divergences by a magnetic field configuration very different from that of a geocentric axial dipole; Irving (and private communication), Van der Voo and French(4) suggest a different reconstruction and it is shown here that these two interpretations are not incompatible and that the first may help the second. PMID:16073416

  10. Magnetic pressure driven implosion of solid liner suitable for compression of field reverse configurations

    SciTech Connect

    Degnan, J.H.; Bartlett, R.; Cavazos, T.

    1999-07-01

    The initial design and performance of a magnetic pressure driven imploding solid liner with dimensions suitable for compressing a Field Reversed Configuration (FRC) is presented and discussed. The nominal liner parameters are 30 cm length, 5 cm outer radius, {approximately}0.1 cm thickness, Al material. The liner is imploded by magnetic pressure from an axial discharge driven by a 1,300 microfarad capacitor bank. Other nominal discharge parameters are {approximately}80 kV initial bank voltage, {approximately}44 nanohenry initial total inductance, and {approximately} milliohm series resistance. The discharge current exceeds 10 mega-amps in {approximately} 9 {micro}sec. Several types of calculations indicate that such a liner will implode in {approximately} 22 to 25 /{micro}sec, and will achieve a >0.3 cm/{micro}sec implosion velocity by the time the liner has imploded to {approximately}2.5 cm radius. This performance and these dimensions are suitable for FRC formation and compression, as discussed by K Schoenberg, R. Siemon, et al. (1). The diagnostics for the initial experiments include current (via Rogowski coils and inductive magnetic probes), voltage (via capacitive divider probes), flash radiography, and diagnostic magnetic field compression. Several types of simulations, including two dimensional magnetohydrodynamic simulations, are also discussed.

  11. Improvement of the magnetic configuration in the reversed field pinch through successive bifurcations

    SciTech Connect

    Lorenzini, R.; Agostini, M.; Alfier, A.; Antoni, V.; Apolloni, L.; Auriemma, F.; Barana, O.; Baruzzo, M.; Bettini, P.; Bonfiglio, D.; Bolzonella, T.; Bonomo, F.; Brombin, M.; Buffa, A.; Canton, A.; Cappello, S.; Carraro, L.; Cavazzana, R.; Chitarin, G.; Dal Bello, S.

    2009-05-15

    The reversed field pinch (RFP) is a magnetic configuration alternative to the tokamak that can be considered for a second generation of reactors. In this paper new remarkable results obtained in the RFP experiment RFX-mod are presented, showing that an internal transport barrier delimitates a large fraction of the plasma volume in a RFP when the current is raised to {approx}1.5 MA. The formation of this transport barrier is related to a profound, spontaneous modification of the magnetic topology. Due to the occurrence of a saddle node bifurcation the plasma enters in the single helical axis state, which is theoretically known to be more resilient to chaos. This bifurcation is driven by the amplitude of the helical perturbation which dominates the mode spectrum.

  12. Improvement of the magnetic configuration in the reversed field pinch through successive bifurcationsa)

    NASA Astrophysics Data System (ADS)

    Lorenzini, R.; Agostini, M.; Alfier, A.; Antoni, V.; Apolloni, L.; Auriemma, F.; Barana, O.; Baruzzo, M.; Bettini, P.; Bonfiglio, D.; Bolzonella, T.; Bonomo, F.; Brombin, M.; Buffa, A.; Canton, A.; Cappello, S.; Carraro, L.; Cavazzana, R.; Chitarin, G.; Dal Bello, S.; De Lorenzi, A.; De Masi, G.; Escande, D. F.; Fassina, A.; Franz, P.; Gaio, E.; Gazza, E.; Giudicotti, L.; Gnesotto, F.; Gobbin, M.; Grando, L.; Guo, S. C.; Innocente, P.; Luchetta, A.; Manduchi, G.; Marchiori, G.; Marcuzzi, D.; Marrelli, L.; Martin, P.; Martini, S.; Martines, E.; Milani, F.; Moresco, M.; Novello, L.; Ortolani, S.; Paccagnella, R.; Pasqualotto, R.; Peruzzo, S.; Piovan, R.; Piovesan, P.; Piron, L.; Pizzimenti, A.; Pomaro, N.; Predebon, I.; Puiatti, M. E.; Rostagni, G.; Sattin, F.; Scarin, P.; Serianni, G.; Sonato, P.; Spada, E.; Soppelsa, A.; Spagnolo, S.; Spizzo, G.; Spolaore, M.; Taliercio, C.; Terranova, D.; Toigo, V.; Valisa, M.; Veltri, P.; Vianello, N.; Zaccaria, P.; Zaniol, B.; Zanotto, L.; Zilli, E.; Zuin, M.

    2009-05-01

    The reversed field pinch (RFP) is a magnetic configuration alternative to the tokamak that can be considered for a second generation of reactors. In this paper new remarkable results obtained in the RFP experiment RFX-mod are presented, showing that an internal transport barrier delimitates a large fraction of the plasma volume in a RFP when the current is raised to 1.5 MA. The formation of this transport barrier is related to a profound, spontaneous modification of the magnetic topology. Due to the occurrence of a saddle node bifurcation the plasma enters in the single helical axis state, which is theoretically known to be more resilient to chaos. This bifurcation is driven by the amplitude of the helical perturbation which dominates the mode spectrum.

  13. Development of Field-Reversed Configuration Plasma Gun Formation Techniques for Magnetized Target Fusion

    NASA Astrophysics Data System (ADS)

    Lynn, Alan; Gilmore, Mark; Wynkoop, Tyler; Intrator, Thomas; Weber, Thomas

    2012-10-01

    Magnetized Target Fusion (MTF) is an innovative approach for a relatively fast and cheap path to the production of fusion energy that utilizes magnetic confinement to assist in the compression of a hot plasma to thermonuclear conditions by an external driver. Los Alamos National Laboratory (LANL) is currently pursing demonstration of the MTF concept via compression of an FRC (field-reversed configuration) plasma by a metal liner z-pinch in conjunction with the Air Force Research Laboratory in Albuquerque, NM. A key physics issue for the FRC as an MTF target lies in the initial pre-ionization (PI) stage. The PI formation process determines the amount of magnetic flux that can be trapped to form the FRC. This trapped flux plays an important role in the FRC's final equilibrium, transport, and stability properties. It also provides the route to greatest potential gains in FRC lifetime, which is essential to provide enough time to translate and compress the FRC effectively. In conjunction with LANL we plan to test and characterize a new system to improve the initial PI plasma formation. This system will use an array of plasma guns to form the initial plasma. Initial characterization of the plasma gun behavior will be presented.

  14. Measurements accounting for the impediment of ion spin-up in rotating magnetic field driven field reversed configurations

    SciTech Connect

    Deards, C. L.; Hoffman, A. L.; Steinhauer, L. C.

    2011-11-15

    Improved vacuum hygiene, wall conditioning, and reduced recycling in the rotating magnetic field (RMF) driven translation, confinement, and sustainment-upgrade (TCSU) field reversed configuration experiment have made possible a more accurate assessment of the forces affecting ion spin-up. This issue is critical in plasmas sustained by RMFs, such as TCSU since ion spin-up can substantially reduce or cancel the RMF current drive effect. Several diagnostics are brought to bear, including a 3-axis translatable magnetic probe allowing the first experimental measurement of the end shorting effect. These results show that the ion rotation is determined by a balance between electron-ion friction, the end shorting effect, and ion drag against neutrals.

  15. Measurements accounting for the impediment of ion spin-up in rotating magnetic field driven field reversed configurations

    NASA Astrophysics Data System (ADS)

    Deards, C. L.; Hoffman, A. L.; Steinhauer, L. C.

    2011-11-01

    Improved vacuum hygiene, wall conditioning, and reduced recycling in the rotating magnetic field (RMF) driven translation, confinement, and sustainment-upgrade (TCSU) field reversed configuration experiment have made possible a more accurate assessment of the forces affecting ion spin-up. This issue is critical in plasmas sustained by RMFs, such as TCSU since ion spin-up can substantially reduce or cancel the RMF current drive effect. Several diagnostics are brought to bear, including a 3-axis translatable magnetic probe allowing the first experimental measurement of the end shorting effect. These results show that the ion rotation is determined by a balance between electron-ion friction, the end shorting effect, and ion drag against neutrals.

  16. Three-Dimensional MHD Simulation of FTEs Produced by Merging at an Isolated Point in a Sheared Magnetic Field Configuration

    NASA Technical Reports Server (NTRS)

    Santos, J. C.; Sibeck, D. G.; Buchner, J.; Gonzalez, W. D.; Ferreira, J. L.

    2014-01-01

    We present predictions for the evolution of FTEs generated by localized bursts of reconnection on a planar magnetopause that separates a magnetosheath region of high densities and weak magnetic field from a magnetospheric region of low densities and strong magnetic field. The magnetic fields present a shear angle of 105 degrees. Reconnection forms a pair of FTEs each crossing the magnetopause in the field reversal region and bulging into the magnetosphere and magnetosheath. At their initial stage they can be characterized as flux tubes since the newly reconnected magnetic field lines are not twisted. Reconnection launches Alfvenic perturbations that propagate along the FTEs generating high-speed jets, which move the pair of FTEs in opposite directions. As the FTE moves, it displaces the ambient magnetic field and plasma producing bipolar magnetic field and plasma velocity signatures normal to the nominal magnetopause in the regions surrounding the FTE. The combination of the ambient plasma with the FTE flows generates a vortical velocity pattern around the reconnected field lines. During its evolution the FTE evolves to a flux rope configuration due to the twist of the magnetic field lines. The alfvenic perturbations propagate faster along the part of the FTE bulging into the magnetosphere than in the magnetosheath, and due to the differences between the plasma and magnetic field properties the perturbations have slightly different signatures in the two regions. As a consequence, the FTEs have different signatures depending on whether the satellite encounters the part bulging into the magnetosphere or into the magnetosheath.

  17. Three-dimensional MHD simulation of FTEs produced by merging at an isolated point in a sheared magnetic field configuration

    NASA Astrophysics Data System (ADS)

    Santos, J. C.; Sibeck, D. G.; Bchner, J.; Gonzalez, W. D.; Ferreira, J. L.

    2014-03-01

    We present predictions for the evolution of FTEs generated by localized bursts of reconnection on a planar magnetopause that separates a magnetosheath region of high densities and weak magnetic field from a magnetospheric region of low densities and strong magnetic field. The magnetic fields present a shear angle of 105 degrees. Reconnection forms a pair of FTEs each crossing the magnetopause in the field reversal region and bulging into the magnetosphere and magnetosheath. At their initial stage they can be characterized as flux tubes since the newly reconnected magnetic field lines are not twisted. Reconnection launches Alfvenic perturbations that propagate along the FTEs generating high-speed jets, which move the pair of FTEs in opposite directions. As the FTE moves, it displaces the ambient magnetic field and plasma producing bipolar magnetic field and plasma velocity signatures normal to the nominal magnetopause in the regions surrounding the FTE. The combination of the ambient plasma with the FTE flows generates a vortical velocity pattern around the reconnected field lines. During its evolution the FTE evolves to a flux rope configuration due to the twist of the magnetic field lines. The alfvenic perturbations propagate faster along the part of the FTE bulging into the magnetosphere than in the magnetosheath, and due to the differences between the plasma and magnetic field properties the perturbations have slightly different signatures in the two regions. As a consequence, the FTEs have different signatures depending on whether the satellite encounters the part bulging into the magnetosphere or into the magnetosheath.

  18. Can We Predict CME Deflections Based on Solar Magnetic Field Configuration Alone?

    NASA Astrophysics Data System (ADS)

    Kay, C.; Opher, M.; Evans, R. M.

    2013-12-01

    Accurate space weather forecasting requires knowledge of the trajectory of coronal mass ejections (CMEs), including predicting CME deflections close to the Sun and through interplanetary space. Deflections of CMEs occur due to variations in the background magnetic field or solar wind speed, magnetic reconnection, and interactions with other CMEs. Using our newly developed model of CME deflections due to gradients in the background solar magnetic field, ForeCAT (Kay et al. 2013), we explore the questions: (a) do all simulated CMEs ultimately deflect to the minimum in the background solar magnetic field? (b) does the majority of the deflection occur in the lower corona below 4 Rs? ForeCAT does not include temporal variations in the magnetic field of active regions (ARs), spatial variations in the background solar wind speed, magnetic reconnection, or interactions with other CMEs. Therefore we focus on the effects of the steady state solar magnetic field. We explore two different Carrington Rotations (CRs): CR 2029 (April-May 2005) and CR 2077 (November-December 2008). Little is known about how the density and magnetic field fall with distance in the lower corona. We consider four density models derived from observations (Chen 1996, Mann et al. 2003, Guhathakurta et al. 2006, Leblanc et al. 1996) and two magnetic field models (PFSS and a scaled model). ForeCAT includes drag resulting from both CME propagation and deflection through the background solar wind. We vary the drag coefficient to explore the effect of drag on the deflection at 1 AU.

  19. Multichord Laser Interferometry on the Magnetized Target Fusion Program's FRL-X Field Reversed Configuration

    NASA Astrophysics Data System (ADS)

    Ruden, Edward; Analla, Francis; Zhang, Shouyin

    2002-11-01

    AFRL's Directed Energy Directorate has built a multiple chord 6328 nm interferometer to diagnose a Field Reversed Configuration (FRC) being developed for LANL and AFRL's collaborative Magnetized Target Fusion (MTF) program. The FRC is intended for compression to near thermonuclear fusion conditions by AFRL's Shiva Star capacitor bank. The interferometer is designed to measure the density integral along eight chords of the uncompressed FRC vs. time. This permits Abel inversion to determine the density profile history. The reference beam is split off with a Bragg cell, raising its frequency by 80 MHz. This permits RF quadrature mixing of the interference signal. The probe traverses a 10 cm diameter quartz tube containing the FRC. A similar tube is placed in the reference path to compensate for refractive distortion. Focusing the beams at tube transit further mitigates distortion. Preliminary design validation experiments at LANL using 2 chords have been successfully completed, and the upgrade to 8 chords is in progress. Results to date will be presented.

  20. Magneto-optical mapping of elementary topological configurations of inhomogeneous magnetic fields

    NASA Astrophysics Data System (ADS)

    Ivanov, V. E.

    2016-03-01

    Magneto-optical images (MO) of projections of an inhomogeneous magnetic field on a magnetic indicator films plane were studied experimentally and by means of modeling. Inhomogeneity of the field clearly displays itself in the planar component distribution of this vector field by the presence of singular points and is clearly revealed by the MO-images in longitudinal sensitivity. The topological structure of the singular points of the field (Poincare Index) manifests itself in the peculiarities of the intensity distribution of the magneto-optical images. These peculiarities can serve as identifiers of "sink", "source" and "saddle"-type singular points. The influence of a homogenous bias field on the change in topological properties is demonstrated. Changes in the geometry of the magnetic system also change the topology of the magnetic field; this is reflected in the number and the properties of the singular points of the MO-images.

  1. Effects of internal structure on equilibrium of field-reversed configuration plasma sustained by rotating magnetic field

    SciTech Connect

    Yambe, Kiyoyuki; Inomoto, Michiaki; Okada, Shigefumi; Kobayashi, Yuka; Asai, Tomohiko

    2008-09-15

    The effects of an internal structure on the equilibrium of a field-reversed configuration (FRC) plasma sustained by rotating magnetic field is investigated by using detailed electrostatic probe measurements in the FRC Injection Experiment apparatus [S. Okada, et al., Nucl. Fusion. 45, 1094 (2005)]. An internal structure installed axially on the geometrical axis, which simulates Ohmic transformer or external toroidal field coils on the FRC device, brings about substantial changes in plasma density profile. The internal structure generates steep density-gradients not only on the inner side but on the outer side of the torus. The radial electric field is observed to sustain the ion thermal pressure-gradient in the FRC without the internal structure; however, the radial electric field is not sufficient to sustain the increased ion thermal pressure-gradient in the FRC with the internal structure. Spontaneously driven azimuthal ion flow will be accountable for the imbalance of the radial pressure which is modified by the internal structure.

  2. Analysis of the magnetic field configuration of a filament-associated flare from X-ray, UV, and optical observations

    NASA Technical Reports Server (NTRS)

    Cheng, C.-C.; Pallavicini, R.

    1984-01-01

    X-ray and ultraviolet observations from SMM of a filament-associated event on November 22, 1980 are examined in conjunction with ground-based optical observations, in order to determine the magnetic field configuration involved in the flaring process. Evidence that the flare was produced by gradual energy release in a large sheared magnetic loop which interacted with another smaller loop is found. Nonthermal processes, as indicated by hard X-ray emission and impulsive UV kernels, were produced in the interaction of the two loops. Although this flare shared some of the characteristics of Long Duration (class II) Events, no indication of a helmet-type configuration, as generally envisaged for class II events, was found. On the contrary, the magnetic configuration of the November 22, 1980 event was more similar to that of a compact (class I) flare, although on a much larger spatial scale and longer time scale.

  3. Transition from drift to interchange instabilities in an open magnetic field line configuration

    SciTech Connect

    Poli, F. M.; Ricci, P.; Fasoli, A.; Podesta, M.

    2008-03-15

    The transition from a regime dominated by drift instabilities to a regime dominated by pure interchange instabilities is investigated and characterized in the simple magnetized toroidal device TORPEX [TORoidal Plasma EXperiment, A. Fasoli et al., Phys. of Plasmas 13, 055906 (2006)]. The magnetic field lines are helical, with a dominant toroidal component and a smaller vertical component. Instabilities with a drift character are observed in the favorable curvature region, on the high field side with respect to the maximum of the background density profile. For a limited range of values of the vertical field they coexist with interchange instabilities in the unfavorable curvature region, on the plasma low field side. With increasing vertical magnetic field magnitude, a gradual transition between the two regimes is observed on the low field side, controlled by the value of the field line connection length. The observed transition follows the predictions of a two-fluid linear model.

  4. On the Role of Global Magnetic Field Configuration in Affecting Ring Current Dynamics

    NASA Technical Reports Server (NTRS)

    Zheng, Y.; Zaharia, S. G.; Fok, M. H.

    2010-01-01

    Plasma and field interaction is one important aspect of inner magnetospheric physics. The magnetic field controls particle motion through gradient, curvature drifts and E cross B drift. In this presentation, we show how the global magnetic field affects dynamics of the ring current through simulations of two moderate geomagnetic storms (20 November 2007 and 8-9 March 2008). Preliminary results of coupling the Comprehensive Ring Current Model (CRCM) with a three-dimensional plasma force balance code (to achieve self-consistency in both E and B fields) indicate that inclusion of self-consistency in B tends to mitigate the intensification of the ring current as other similar coupling efforts have shown. In our approach, self-consistency in the electric field is already an existing capability of the CRCM. The magnetic self-consistency is achieved by computing the three-dimensional magnetic field in force balance with anisotropic ring current ion distributions. We discuss the coupling methodology and its further improvement. In addition, comparative studies by using various magnetic field models will be shown. Simulation results will be put into a global context by analyzing the morphology of the ring current, its anisotropy and characteristics ofthe interconnected region 2 field-aligned currents.

  5. On the Magnetic Field of Pulsars with Realistic Neutron Star Configurations

    NASA Astrophysics Data System (ADS)

    Belvedere, R.; Rueda, Jorge A.; Ruffini, R.

    2015-01-01

    We have recently developed a neutron star model fulfilling global and not local charge neutrality, both in the static and in the uniformly rotating cases. The model is described by the coupled Einstein-Maxwell-Thomas-Fermi equations, in which all fundamental interactions are accounted for in the framework of general relativity and relativistic mean field theory. Uniform rotation is introduced following Hartle's formalism. We show that the use of realistic parameters of rotating neutron stars, obtained from numerical integration of the self-consistent axisymmetric general relativistic equations of equilibrium, leads to values of the magnetic field and radiation efficiency of pulsars that are very different from estimates based on fiducial parameters that assume a neutron star mass M = 1.4 M ?, radius R = 10 km, and moment of inertia I = 1045 g cm2. In addition, we compare and contrast the magnetic field inferred from the traditional Newtonian rotating magnetic dipole model with respect to the one obtained from its general relativistic analog, which takes into account the effect of the finite size of the source. We apply these considerations to the specific high-magnetic field pulsar class and show that, indeed, all of these sources can be described as canonical pulsars driven by the rotational energy of the neutron star, and have magnetic fields lower than the quantum critical field for any value of the neutron star mass.

  6. ON THE MAGNETIC FIELD OF PULSARS WITH REALISTIC NEUTRON STAR CONFIGURATIONS

    SciTech Connect

    Belvedere, R.; Rueda, Jorge A.; Ruffini, R. E-mail: jorge.rueda@icra.it

    2015-01-20

    We have recently developed a neutron star model fulfilling global and not local charge neutrality, both in the static and in the uniformly rotating cases. The model is described by the coupled Einstein-Maxwell-Thomas-Fermi equations, in which all fundamental interactions are accounted for in the framework of general relativity and relativistic mean field theory. Uniform rotation is introduced following Hartle's formalism. We show that the use of realistic parameters of rotating neutron stars, obtained from numerical integration of the self-consistent axisymmetric general relativistic equations of equilibrium, leads to values of the magnetic field and radiation efficiency of pulsars that are very different from estimates based on fiducial parameters that assume a neutron star mass M = 1.4 M {sub ☉}, radius R = 10 km, and moment of inertia I = 10{sup 45} g cm{sup 2}. In addition, we compare and contrast the magnetic field inferred from the traditional Newtonian rotating magnetic dipole model with respect to the one obtained from its general relativistic analog, which takes into account the effect of the finite size of the source. We apply these considerations to the specific high-magnetic field pulsar class and show that, indeed, all of these sources can be described as canonical pulsars driven by the rotational energy of the neutron star, and have magnetic fields lower than the quantum critical field for any value of the neutron star mass.

  7. The TITAN magnet configuration

    NASA Astrophysics Data System (ADS)

    Bathke, C. G.

    The TITAN study uses copper-alloy ohmic-heating coils (OHC) to start up inductively a reversed-field-pinch (RFP) fusion reactor. The plasma equilibrium is maintained with a pair of superconducting equilibrium-field coils (EFCs). A second pair of copper EFCs provides the necessary trimming of the equilibrium field during plasma transients. A compact toroidal-field-coil (TFC) set is provided by an integrated blanket/coil (IBC). The IBC concept also is applied to the toroidal-field divertor coils. Steady-state operation is achieved with oscillating-field current drive, which oscillates at low amplitude and frequency the OHCs, EFCs, the TFCs, and divertor coils about their steady-state currents. An integrated magnet design, which uses low-field, low technology coils, and the related design basis is given.

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

    DOEpatents

    Eberhard, Philippe H. (El Cerrito, CA)

    1985-01-01

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

  9. Numerical analysis of the trajectories of a single charged particle in a nonadiabatic cusp magnetic field configuration

    SciTech Connect

    Selvarajan, V.; Vijayalakshmi, K.A.

    1995-05-01

    The trajectories of a nonrelativistic single charged particle in a nonadiabatic cusped magnetic field configuration are numerically analyzed. Depth of penetration of the particle into the cusped field, multiple reflections and radial excursion of the particle transmitted by the cusped field are discussed. A significant observation was that a meticulous choice of particle and field parameters could lead to several number of reflections. For radial excursion a plateau region over {Phi} was exhibited. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  10. Impact of rotation on the geometrical configurations of fossil magnetic fields

    NASA Astrophysics Data System (ADS)

    Emeriau, C.; Mathis, S.

    2015-01-01

    The MiMeS project demonstrated that a small fraction of massive stars (around 7%) presents large-scale, stable, generally dipolar magnetic fields at their surface. These fields that do not present any evident correlations with stellar mass or rotation are supposed to be fossil remnants of the initial phases of stellar evolution. They result from the relaxation to MHD equilibrium states, during the formation of stable radiation zones, of initial fields resulting from a previous convective phase. In this work, we present new theoretical results, where we generalize previous studies by taking rotation into account. The properties of relaxed fossil fields are compared to those obtained when rotation is ignored. Consequences for magnetic fields in the radiative envelope of rotating early-type stars and their stability are finally discussed.

  11. The magnetic field configuration of a solar prominence inferred from spectropolarimetric observations in the He i 10 830 triplet

    NASA Astrophysics Data System (ADS)

    Orozco Surez, D.; Asensio Ramos, A.; Trujillo Bueno, J.

    2014-06-01

    Context. Determining the magnetic field vector in quiescent solar prominences is possible by interpreting the Hanle and Zeeman effects in spectral lines. However, observational measurements are scarce and lack high spatial resolution. Aims: We determine the magnetic field vector configuration along a quiescent solar prominence by interpreting spectropolarimetric measurements in the He i 1083.0 nm triplet obtained with the Tenerife Infrared Polarimeter installed at the German Vacuum Tower Telescope of the Observatorio del Teide. Methods: The He i 1083.0 nm triplet Stokes profiles were analyzed with an inversion code that takes the physics responsible for the polarization signals in this triplet into account. The results are put into a solar context with the help of extreme ultraviolet observations taken with the Solar Dynamic Observatory and the Solar Terrestrial Relations Observatory satellites. Results: For the most probable magnetic field vector configuration, the analysis depicts a mean field strength of 7 gauss. We do not find local variations in the field strength except that the field is, on average, lower in the prominence body than in the prominence feet, where the field strength reaches ~25 gauss. The averaged magnetic field inclination with respect to the local vertical is ~77. The acute angle of the magnetic field vector with the prominence main axis is 24 for the sinistral chirality case and 58 for the dextral chirality. These inferences are in rough agreement with previous results obtained from the analysis of data acquired with lower spatial resolutions. A movie is available in electronic form at http://www.aanda.org

  12. The effect of large-scale magnetic field on outflow in ADAFs: an odd symmetry configuration

    NASA Astrophysics Data System (ADS)

    Samadi, Maryam; Abbassi, Shahram

    2016-01-01

    We construct self-similar inflow-outflow solutions for a hot viscous-resistive accretion flow with large-scale magnetic fields that have odd symmetry with respect to the equatorial plane in Bθ and even symmetry in Br and Bφ. Following previous authors, we also assume that the polar velocity vθ is non-zero. We focus on four parameters: βr0, βφ0 (the plasma beta parameters associated with magnetic field components at the equatorial plane), the magnetic resistivity η0 and the density index n = -dln ρ/dln r. The resulting flow solutions are divided into two parts, consisting of an inflow region with a negative radial velocity (vr < 0) and an outflow region with vr > 0. Our results show that stronger outflows emerge for smaller βr0 (≤10-2 for n > 1) and larger values of βφ0, η0 and n.

  13. Influence of demagnetization coil configuration on residual field in an extremely magnetically shielded room: Model and measurements

    NASA Astrophysics Data System (ADS)

    Knappe-Grueneberg, Silvia; Schnabel, Allard; Wuebbeler, Gerd; Burghoff, Martin

    2008-04-01

    The Berlin magnetically shielded room 2 (BMSR-2) features a magnetic residual field below 500pT and a field gradient level less than 0.5pT/mm, which are needed for very sensitive human biomagnetic recordings or low field NMR. Nevertheless, below 15Hz, signals are compromised by an additional noise contribution due to vibration forced sensor movements in the field gradient. Due to extreme shielding, the residual field and its homogeneity are determined mainly by the demagnetization results of the mumetal shells. Eight different demagnetization coil configurations can be realized, each results in a characteristic field pattern. The spatial dc flux density inside BMSR-2 is measured with a movable superconducting quantum interference device system with an accuracy better than 50pT. Residual field and field distribution of the current-driven coils fit well to an air-core coil model, if the high permeable core and the return lines outside of the shells are neglected. Finally, we homogenize the residual field by selecting a proper coil configuration.

  14. Investigation of different magnetic field configurations using an electrical, modular Zeeman slower

    NASA Astrophysics Data System (ADS)

    Ohayon, Ben; Ron, Guy

    2015-10-01

    We present a method of constructing an automatically reconfigurable, modular, electronic Zeeman slower, which is remotely controlled. This setup is used to investigate the ability of different magnetic field profiles to slow thermal atoms to the capture velocity of a magneto-optical-trap. We show that a simple numerical optimization process yields better results than the commonly used approach for deciding on the appropriate field and comes close to the optimum field, found by utilizing a fast feedback loop which uses a genetic algorithm. Our new numerical method is easily adaptable to a variety of existing slower designs and may be beneficial where feedback is unavailable.

  15. roAp stars: surface lithium abundance distribution and magnetic field configuration

    NASA Astrophysics Data System (ADS)

    Polosukhina, N.; Shulyak, D.; Shavrina, A.; Lyashko, D.; Drake, N. A.; Glagolevski, Yu.; Kudryavtsev, D.; Smirnova, M.

    2014-08-01

    High-resolution spectra obtained with the 6m BTA telescope, Russia, and with HARPS and VLT/UVES telescopes at ESO, Chile, were used for Doppler Imaging analysis of two roAp stars, HD 12098 and HD 60435, showing strong and variable Li resonance line in their spectra. We found that Li has highly inhomogeneous distribution on the surfaces of these stars. We compared our results with previously obtained Doppler Imaging mapping of two CP2 stars, HD 83368 and HD 3980, and discuss the correlation between the position of the high Li-abundance spots and magnetic field.

  16. Stable anisotropic plasma confinement in magnetic configurations with convex-concave field lines

    NASA Astrophysics Data System (ADS)

    Tsventoukh, M. M.

    2014-02-01

    It is shown that a combination of the convex and the concave part of a field line provides a strong stabilizing action against convective (flute-interchange) plasma instability (Tsventoukh 2011 Nucl. Fusion 51 112002). This results in internal peaking of the stable plasma pressure profile that is calculated from the collisionless kinetic stability criterion for any magnetic confinement system with combination of mirrors and cusps. Connection of the convex and concave field line parts results in a reduction of the space charge that drives the unstable E × B motion, as there is an opposite direction of the particle drift in a non-uniform field at convex and concave field lines. The pressure peaking arises at the minimum of the second adiabatic invariant J that takes place at the ‘middle’ of a tandem mirror-cusp transverse cross-section. The position of the minimum in J varies with the particle pitch angle that results in a shift of the peaking position depending on plasma anisotropy. This allows one to improve a stable peaked pressure profile at a convex-concave field by changing the plasma anisotropy over the trap cross-section. Examples of such anisotropic distribution functions are found that give an additional substantial enhancement in the maximal central pressure. Furthermore, the shape of new calculated stable profiles has a wide central plasma layer instead of a narrow peak.

  17. Plasma equilibrium in axisymmetric poloidal magnetic field configurations in flux coordinates

    SciTech Connect

    Arsenin, V. V.; Terekhin, P. N.

    2011-08-15

    A simple derivation is given of equilibrium equations in flux coordinates in the general case of an anisotropic-pressure plasma. The issue of how to formulate the boundary conditions for these equations is discussed for two types of configurations-a straight system and a system with an internal conductor. Examples of numerical solutions to the equilibrium problem for these configurations are presented.

  18. Passive magnetic bearing configurations

    DOEpatents

    Post, Richard F. (Walnut Creek, CA)

    2011-01-25

    A journal bearing provides vertical and radial stability to a rotor of a passive magnetic bearing system when the rotor is not rotating and when it is rotating. In the passive magnetic bearing system, the rotor has a vertical axis of rotation. Without the journal bearing, the rotor is vertically and radially unstable when stationary, and is vertically stable and radially unstable when rotating.

  19. Field Reversed Configuration Target Design for a Magnetized Target Fusion Experiment

    NASA Astrophysics Data System (ADS)

    Wurden, G. A.; Schoenberg, K. F.; Siemon, R. E.; Tuszewski, M.; Wysocki, F. J.; Milroy, R. D.

    1998-11-01

    We are designing a compact (r=5 cm, l=30 cm), high density (n=10^18 cm-3) FRC using theta pinch formation techniques, which will be translated into an aluminum liner for implosion to fusion relevant parameters. Stored plasma energy will be modest (7.5 kJ), with average beta of 1, and external magnetic field strength of 5.4 T. MOQUI code calculations show that the required plasma can be formed using conical theta pinch coils and our existing Colt 0.25 MJ capacitor bank, and then translated in a few microseconds into the aluminum liner, where it is trapped. After the plasma is suitably diagnosed (Thomson scattering, interferometry, spectroscopy), the experiment will be attached to a pulsed-power driver (Shiva Star or Atlas, for example), where it will be destructively imploded. Modularity and compatibility with an actual liner assembly are important elements of this FRC target plasma design. On the Web, click http://fusionenergy.lanl.gov for more details.

  20. Application of a solar wind model driven by turbulence dissipation to a 2D magnetic field configuration

    SciTech Connect

    Lionello, Roberto; Downs, Cooper; Linker, Jon A.; Mikić, Zoran; Velli, Marco E-mail: cdowns@predsci.com E-mail: mikic@predsci.com

    2014-12-01

    Although it is widely accepted that photospheric motions provide the energy source and that the magnetic field must play a key role in the process, the detailed mechanisms responsible for heating the Sun's corona and accelerating the solar wind are still not fully understood. Cranmer et al. developed a sophisticated, one-dimensional (1D), time-steady model of the solar wind with turbulence dissipation. By varying the coronal magnetic field, they obtain, for a single choice of wave properties, a realistic range of slow and fast wind conditions with a sharp latitudinal transition between the two streams. Using a 1D, time-dependent model of the solar wind of Lionello et al., which incorporates turbulent dissipation of Alfvén waves to provide heating and acceleration of the plasma, we have explored a similar configuration, obtaining qualitatively equivalent results. However, our calculations suggest that the rapid transition between slow and fast wind suggested by this 1D model may be disrupted in multidimensional MHD simulations by the requirement of transverse force balance.

  1. Three-dimensional instability of thermal convection in a vertical Bridgman growth configuration under traveling magnetic field

    NASA Astrophysics Data System (ADS)

    Wang, Bo-Fu; Li, Yan-Hui; Zhou, Lin; Deng, An-Li; Ma, Dong-Jun; Sun, De-Jun; Jiang, Jin

    2015-06-01

    Thermal convection in a vertical Bridgman growth configuration under the effect of a traveling magnetic field (TMF) is investigated numerically. The vertical Bridgman growth configuration is approximated by convection in a cylinder with a parabolic heated sidewall and isothermal-cooled end walls. The TMF effect is introduced as a usual approximation under low frequency and a low induction assumption to use the analytical expression for the Lorentz force applied in the fluid volume. The strength of the TMF force is measured by the parameter Ft. The cylinder aspect ratio (height/radius) is fixed to Γ =1, and the Prandtl number considered is fixed to Pr = 0.02. The base flow simultaneously excited by buoyancy and TMF is axisymmetric. Our primary goal is to determine how the flow loses stability to three-dimensional flow. An extremely multiple valued stability curve in the (Ft,Ra) plane is revealed by linear stability analysis. Three distinct flow regimes are classified, i.e., buoyancy dominated regime, buoyancy and TMF-counterbalanced regime, and TMF-dominated regime. Typical steady and unsteady three-dimensional flows are illustrated.

  2. Switching ferroelectric domain configurations using both electric and magnetic fields in Pb(Zr,Ti)O3Pb(Fe,Ta)O3 single-crystal lamellae

    PubMed Central

    Evans, D. M.; Schilling, A.; Kumar, Ashok; Sanchez, D.; Ortega, N.; Katiyar, R. S.; Scott, J. F.; Gregg, J. M.

    2014-01-01

    Thin single-crystal lamellae cut from Pb(Zr,Ti)O3Pb(Fe,Ta)O3 ceramic samples have been integrated into simple coplanar capacitor devices. The influence of applied electric and magnetic fields on ferroelectric domain configurations has been mapped, using piezoresponse force microscopy. The extent to which magnetic fields alter the ferroelectric domains was found to be strongly history dependent: after switching had been induced by applying electric fields, the susceptibility of the domains to change under a magnetic field (the effective magnetoelectric coupling parameter) was large. Such large, magnetic field-induced changes resulted in a remanent domain state very similar to the remanent state induced by an electric field. Subsequent magnetic field reversal induced more modest ferroelectric switching. PMID:24421376

  3. Elucidation of Ground-State Spin Configurations of Ising Models in a Magnetic Field with Frustration on a Diamond Hierarchical Lattice

    NASA Astrophysics Data System (ADS)

    Hirose, Yuhei; Oguchi, Akihide; Fukumoto, Yoshiyuki

    2015-10-01

    To study the ground-state spin configuration as a function of magnetic field, the spin configurations at each stage lattice are determined by analyzing recursion equations. The exact calculation of the magnetization curve by Hirose et al. [J. Phys. Soc. Jpn. 83, 074716 (2014)] shows that an infinitely small applied magnetic field on the zero-field classical spin-liquid phase can induce an infinitely small magnetization, which is as if this Ising system has a gapless spectrum. In this study, we reveal that an infinitely small applied field makes a large number of spins flip upwards with the exchange-energy loss remaining finite. This exotic behavior originates from the frustration effect of diamond structures and an inherent long-range nature of hierarchical lattices.

  4. High Performance Field Reversed Configurations

    NASA Astrophysics Data System (ADS)

    Binderbauer, Michl

    2014-10-01

    The field-reversed configuration (FRC) is a prolate compact toroid with poloidal magnetic fields. FRCs could lead to economic fusion reactors with high power density, simple geometry, natural divertor, ease of translation, and possibly capable of burning aneutronic fuels. However, as in other high-beta plasmas, there are stability and confinement concerns. These concerns can be addressed by introducing and maintaining a significant fast ion population in the system. This is the approach adopted by TAE and implemented for the first time in the C-2 device. Studying the physics of FRCs driven by Neutral Beam (NB) injection, significant improvements were made in confinement and stability. Early C-2 discharges had relatively good confinement, but global power losses exceeded the available NB input power. The addition of axially streaming plasma guns, magnetic end plugs as well as advanced surface conditioning leads to dramatic reductions in turbulence driven losses and greatly improved stability. As a result, fast ion confinement significantly improved and allowed for build-up of a dominant fast particle population. Under such appropriate conditions we achieved highly reproducible, long-lived, macroscopically stable FRCs with record lifetimes. This demonstrated many beneficial effects of large orbit particles and their performance impact on FRCs Together these achievements point to the prospect of beam-driven FRCs as a path toward fusion reactors. This presentation will review and expand on key results and present context for their interpretation.

  5. Final Report on Development of Optimized Field-Reversed Configuration Plasma Formation Techniques for Magnetized Target Fusion

    SciTech Connect

    Lynn, Alan

    2013-11-01

    The University of New Mexico (UNM) proposed a collaboration with Los Alamos National Laboratory (LANL) to develop and test methods for improved formation of field-reversed configuration (FRC) plasmas relevant to magnetized target fusion (MTF) energy research. MTF is an innovative approach for a relatively fast and cheap path to the production of fusion energy that utilizes magnetic confinement to assist in the compression of a hot plasma to thermonuclear conditions by an external driver. LANL is currently pursing demonstration of the MTF concept via compression of an FRC plasma by a metal liner z-pinch in conjunction with the Air Force Research Laboratory in Albuquerque, NM. A key physics issue for the FRC's ultimate success as an MTF target lies in the initial pre-ionization (PI) stage. The PI plasma sets the initial conditions from which the FRC is created. In particular, the PI formation process determines the amount of magnetic flux that can be trapped to form the FRC. A ringing theta pinch ionization (RTPI) technique, such as currently used by the FRX-L device at LANL, has the advantages of high ionization fraction, simplicity (since no additional coils are required), and does not require internal electrodes which can introduce impurities into the plasma. However RTPI has been shown to only trap #24;50% of the initial bias flux at best and imposes additional engineering constraints on the capacitor banks. The amount of trapped flux plays an important role in the FRC's final equilibrium, transport, and stability properties, and provides increased ohmic heating of the FRC through induced currents as the magnetic field decays. Increasing the trapped flux also provides the route to greatest potential gains in FRC lifetime, which is essential to provide enough time to translate and compress the FRC effectively. In conjunction with LANL we initially planned to develop and test a microwave break- down system to improve the initial PI plasma formation. The UNM team would design the microwave optics and oversee the fabrication and assembly of all components and assist with integration into the FRX-L machine control system. LANL would provide a preexisting 65 kW X-band microwave source and some associated waveguide hardware. Once constructed and installed, UNM would take the lead in operating the microwave breakdown system and conducting studies to optimize its use in FRC PI formation in close cooperation with the needs of the LANL MTF team. In conjunction with our LANL collaborators, we decided after starting the project to switch from a microwave plasma breakdown approach to a plasma gun technology to use for enhanced plasma formation in the FRX-L field-reversed configuration experiment at LANL. Plasma guns would be able to provide significantly higher density plasma with greater control over its distribution in time and space within the experiment. This would allow greater control and #12;ne-tuning of the PI plasma formed in the experiment. Multiple plasma guns would be employed to fill a Pyrex glass test chamber (built at UNM) with plasma which would then be characterized and optimized for the MTF effort.

  6. Upgraded coil configuration for ISABELLE magnets

    SciTech Connect

    Hahn, H.; Dahl, P.F.; Kaugerts, J.E.; Prodell, A.G.

    1981-01-01

    Achievement of the design field of 5 T in the ISABELLE dipole magnets is turning out to be more arduous than expected and several avenues of improvement are being pursued. One possibility for improving training and peak field performance is discussed in this paper. It has been recognized that the inert spacers with their adjacent active turns in the cosine magnet windings can be replaced by a double thickness braid operating at approximately half-current density in 46 of the 190 turns. Since the high-field region occurs in the low current density turns near the poles, a performance improvement can be expected. It has been verified that the proposed coil configuration satisfies the field requirements and details thereof are given. Results from an experimental magnet in which superconducting spacer turns are used to simulate half-current density windings are presented. Construction of thick braid coils is being planned and the status of these magnets is reviewed.

  7. 3D effects of edge magnetic field configuration on divertor/scrape-off layer transport and optimization possibilities for a future reactor

    NASA Astrophysics Data System (ADS)

    Kobayashi, M.; Xu, Y.; Ida, K.; Corre, Y.; Feng, Y.; Schmitz, O.; Frerichs, H.; Tabares, F. L.; Evans, T. E.; Coenen, J. W.; Liang, Y.; Bader, A.; Itoh, K.; Yamada, H.; Ghendrih, Ph.; Ciraolo, G.; Tafalla, D.; Lopez-Fraguas, A.; Guo, H. Y.; Cui, Z. Y.; Reiter, D.; Asakura, N.; Wenzel, U.; Morita, S.; Ohno, N.; Peterson, B. J.; Masuzaki, S.

    2015-10-01

    This paper assesses the three-dimensional (3D) effects of the edge magnetic field structure on divertor/scrape-off layer transport, based on an inter-machine comparison of experimental data and on the recent progress of 3D edge transport simulation. The 3D effects are elucidated as a consequence of competition between transports parallel (\\parallel ) and perpendicular (\\bot ) to the magnetic field, in open field lines cut by divertor plates, or in magnetic islands. The competition has strong impacts on divertor functions, such as determination of the divertor density regime, impurity screening and detachment control. The effects of magnetic perturbation on the edge electric field and turbulent transport are also discussed. Parameterization to measure the 3D effects on the edge transport is attempted for the individual divertor functions. Based on the suggested key parameters, an operation domain of the 3D divertor configuration is discussed for future devices.

  8. Field-Reversed Configurations in an Unmagnetized Plasma

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.; Strohmaier, K. D.

    2008-09-26

    An oscillating magnetic field is applied with a loop antenna to an unmagnetized plasma. At small amplitudes the field is evanescent. At large amplitudes the field magnetizes the electrons, which allows deeper field penetration in the whistler modes. Field-reversed configurations are formed at each half cycle. Electrons are energized. Transient whistler instabilities produce high-frequency oscillations in the magnetized plasma volume.

  9. Inductive sustainment of oblate field-reversed configurations with the assistance of magnetic diffusion, shaping, and finite-Larmor radius stabilization

    SciTech Connect

    Gerhardt, S. P.; Belova, E. V.; Yamada, M.; Ji, H.; Jacobson, C. M.; McGeehan, B.; Ren, Y.; Inomoto, M.; Maqueda, R.

    2008-02-15

    Oblate field-reversed configurations (FRCs) have been sustained for >300 {mu}s, or >15 magnetic diffusion times, through the use of an inductive solenoid. These argon FRCs can have their poloidal flux sustained or increased, depending on the timing and strength of the induction. An inward pinch is observed during sustainment, leading to a peaking of the pressure profile and maintenance of the FRC equilibrium. The good stability observed in argon (and krypton) does not transfer to lighter gases, which develop terminal co-interchange instabilities. The stability in argon and krypton is attributed to a combination of external field shaping, magnetic diffusion, and finite-Larmor radius effects.

  10. The Magnetic Configuration of a ?-Spot

    NASA Astrophysics Data System (ADS)

    Balthasar, H.; Beck, C.; Louis, R. E.; Verma, M.; Denker, C.

    2014-10-01

    Sunspots, which harbor both magnetic polarities within one penumbra, are called ?-spots. They are often associated with flares. Nevertheless, there are only very few detailed observations of the spatially resolved magnetic field configuration. We present an investigation performed with the Tenerife Infrared Polarimeter at the Vacuum Tower Telescope in Tenerife. We observed a sunspot with a main umbra and several additional umbral cores, one of them with opposite magnetic polarity (the ?-umbra). The ?-spot is divided into two parts by a line along which central emissions of the spectral line Ca II 854.2 nm appear. The Evershed flow comming from the main umbra ends at this line. In deep photospheric layers, we find an almost vertical magnetic field for the ?-umbra, and the magnetic field decreases rapidly with height, faster than in the main umbra. The horizontal magnetic field in the direction connecting main and ?-umbra is rather smooth, but in one location next to a bright penumbral feature at some distance to the ?-umbra, we encounter a change of the magnetic azimuth by 90 from one pixel to the next. Near the ?-umbra, but just outside, we encounter a blue-shift of the spectral line profiles which we interpret as Evershed flow away from the ?-umbra. Significant electric current densities are observed at the dividing line of the spot and inside the ?-umbra.

  11. Controlling precise magnetic field configuration around electron cyclotron resonance zone for enhancing plasma parameters and beam current

    SciTech Connect

    Yano, Keisuke Kurisu, Yosuke; Nozaki, Dai; Kimura, Daiju; Imai, Youta; Kumakura, Sho; Sato, Fuminobu; Kato, Yushi; Iida, Toshiyuki

    2014-02-15

    Multi-charged ion source which has wide operating conditions is required in various application fields. We have constructed tandem type ECR ion source (ECRIS); one of the features of its main stage is an additional coil for controlling magnetic field distribution around the mirror bottom precisely. Here the effect of magnetic field variation caused by the additional coil is experimentally considered in terms of plasma parameters and beam current as the first investigation of the main stage plasma. Furthermore, behavior of magnetic lines of force flowing from the ECR zone is calculated, and is compared with measurement results aiming for better understanding of interrelationship between plasma production and ion beam generation on the ECRIS.

  12. Controlling precise magnetic field configuration around electron cyclotron resonance zone for enhancing plasma parameters and beam current.

    PubMed

    Yano, Keisuke; Kurisu, Yosuke; Nozaki, Dai; Kimura, Daiju; Imai, Youta; Kumakura, Sho; Sato, Fuminobu; Kato, Yushi; Iida, Toshiyuki

    2014-02-01

    Multi-charged ion source which has wide operating conditions is required in various application fields. We have constructed tandem type ECR ion source (ECRIS); one of the features of its main stage is an additional coil for controlling magnetic field distribution around the mirror bottom precisely. Here the effect of magnetic field variation caused by the additional coil is experimentally considered in terms of plasma parameters and beam current as the first investigation of the main stage plasma. Furthermore, behavior of magnetic lines of force flowing from the ECR zone is calculated, and is compared with measurement results aiming for better understanding of interrelationship between plasma production and ion beam generation on the ECRIS. PMID:24593516

  13. 11-13 GHz electron cyclotron resonance plasma source using cylindrically comb-shaped magnetic-field configuration for broad ion-beam processing

    SciTech Connect

    Asaji, Toyohisa; Kato, Yushi; Sato, Fuminobu; Iida, Toshiyuki; Saito, Junji

    2006-11-15

    An electron cyclotron resonance (ECR) plasma source for broad ion-beam processing has been upgraded by a cylindrically comb-shaped magnetic-field configuration and 11-13 GHz frequency microwaves. A pair of comb-shaped magnets surrounds a large-bore discharge chamber. The magnetic field well confines plasmas with suppressing diffusion toward the axial direction of the cylindrical chamber. The magnetic field is constructed with a multipole and two quasiring permanent magnets. The plasma density clearly increases as compared with that in a simple multipole magnetic-field configuration. The frequency of microwaves output from the traveling-wave tube amplifier can be easily changed with an input signal source. The plasma density for 13 GHz is higher than that for 11 GHz. The maximum plasma density has reached approximately 10{sup 18} m{sup -3} at a microwave power of only 350 W and a pressure of 1.0 Pa. The enhancement of plasma generation by second-harmonic resonance and microwave modes has been investigated. The plasma density and the electron temperature are raised around the second-harmonic resonance zone. And then, the ion saturation current is periodically increased with varying the position of the plate tuner. The distance between the peaks is nearly equal to half of the free-space wavelength of microwave. The efficiency of ECR has been improved by using the comb-shaped magnetic field and raising microwave frequency, and then the high-density plasma source has been accomplished at low microwave power.

  14. Spectroscopy with multiple field configurations

    SciTech Connect

    Krasnitz, A. )

    1991-04-15

    The effect of field configuration copying on both fermion and fermion-antifermion pair correlation functions is studied in detail in a simple quantum-mechanical model. It is found that, with very few exceptions, the copying procedure results in a large correction to the corresponding effective masses. In particular, this correction leads to an oscillatory behavior of the effective masses, similar to that observed for mesons in recent lattice QCD calculations. It is argued that the copying technique is unlikely to be useful as a spectroscopic tool.

  15. Field-reversed configurations in an unmagnetized plasma.

    PubMed

    Stenzel, R L; Urrutia, J M; Strohmaier, K D

    2008-09-26

    An oscillating magnetic field is applied with a loop antenna to an unmagnetized plasma. At small amplitudes the field is evanescent. At large amplitudes the field magnetizes the electrons, which allows deeper field penetration in the whistler modes. Field-reversed configurations are formed at each half cycle. Electrons are energized. Transient whistler instabilities produce high-frequency oscillations in the magnetized plasma volume. PMID:18851455

  16. Magnetic Field Configuration of Active Region NOAA 6555 at the Time of a Long Duration Flare on 23 March 1991: An Exception to Standard Flare Reconnection Model

    NASA Technical Reports Server (NTRS)

    Choudhary, Debi Prasad; Gary, Allen G.

    1998-01-01

    The high-resolution H(sub alpha) images observed during the decay phase of a long duration flare on 23 March 1991 are used to study the three-dimensional magnetic field configuration of the active region NOAA 6555. Whereas, all the large flares in NOAA 6555 occurred at the location of high magnetic shear and flux emergence, this long duration flare was observed in the region of low magnetic shear at the photosphere. The H(sub alpha) loop activity started soon after the maximum phase of the flare. There were few long loop at the initial phase of the activity. Some of these were sheared in the chromosphere at an angle of about 45 deg with the east-west axis. Gradually, increasing number of shorter loops, oriented along the east-west axis, started appearing. The chromospheric Dopplergrams show blue-shifts at the end points of the loops. By using different magnetic field models, we have extrapolated the photospheric magnetograms to the chromospheric heights. The magnetic field lines computed by using the potential field model correspond to most of the observed H(sub alpha) loops. The height of the H(sub alpha) loops were derived by comparing them with the computed field lines. From the temporal evolution of the H(sub alpha) loop activity, we derive the negative rate of appearance of H(sub alpha) features as a function of height. It is found that the field lines oriented along one of the neutral lines was sheared and low lying. The higher field lines were mostly potential. The paper also outlines a possible scenario for describing the post-flare stage of the observed long duration flare.

  17. Review of field-reversed configurations

    SciTech Connect

    Steinhauer, Loren C.

    2011-07-15

    This review addresses field-reversed configurations (FRCs), which are compact-toroidal magnetic systems with little or no toroidal field and very high {beta} (ratio of plasma pressure to magnetic pressure). Although enthusiasm for the FRC has primarily been driven by its potential for an attractive fusion reactor, this review focuses on the physics rather than on technological or engineering aspects. Major advances in both theory and experiment have taken place since the previous comprehensive FRC review in 1988. Even so many questions remain. In particular, even though FRC experiments have exhibited remarkable stability, how well this extrapolates to larger systems remains unresolved. The review considers FRCs under familiar topical categories: equilibrium, global stability, self-organization, transport, formation, and sustainment.

  18. Review of field-reversed configurations

    NASA Astrophysics Data System (ADS)

    Steinhauer, Loren C.

    2011-07-01

    This review addresses field-reversed configurations (FRCs), which are compact-toroidal magnetic systems with little or no toroidal field and very high ? (ratio of plasma pressure to magnetic pressure). Although enthusiasm for the FRC has primarily been driven by its potential for an attractive fusion reactor, this review focuses on the physics rather than on technological or engineering aspects. Major advances in both theory and experiment have taken place since the previous comprehensive FRC review in 1988. Even so many questions remain. In particular, even though FRC experiments have exhibited remarkable stability, how well this extrapolates to larger systems remains unresolved. The review considers FRCs under familiar topical categories: equilibrium, global stability, self-organization, transport, formation, and sustainment.

  19. A high density field reversed configuration (FRC) target for magnetized target fusion: First internal profile measurements of a high density FRC

    NASA Astrophysics Data System (ADS)

    Intrator, T.; Zhang, S. Y.; Degnan, J. H.; Furno, I.; Grabowski, C.; Hsu, S. C.; Ruden, E. L.; Sanchez, P. G.; Taccetti, J. M.; Tuszewski, M.; Waganaar, W. J.; Wurden, G. A.

    2004-05-01

    Magnetized target fusion (MTF) is a potentially low cost path to fusion, intermediate in plasma regime between magnetic and inertial fusion energy. It requires compression of a magnetized target plasma and consequent heating to fusion relevant conditions inside a converging flux conserver. To demonstrate the physics basis for MTF, a field reversed configuration (FRC) target plasma has been chosen that will ultimately be compressed within an imploding metal liner. The required FRC will need large density, and this regime is being explored by the FRX-L (FRC-Liner) experiment. All theta pinch formed FRCs have some shock heating during formation, but FRX-L depends further on large ohmic heating from magnetic flux annihilation to heat the high density (2-51022m-3), plasma to a temperature of Te+Ti?500 eV. At the field null, anomalous resistivity is typically invoked to characterize the resistive like flux dissipation process. The first resistivity estimate for a high density collisional FRC is shown here. The flux dissipation process is both a key issue for MTF and an important underlying physics question.

  20. An automated approach to magnetic divertor configuration design

    NASA Astrophysics Data System (ADS)

    Blommaert, M.; Dekeyser, W.; Baelmans, M.; Gauger, N. R.; Reiter, D.

    2015-01-01

    Automated methods based on optimization can greatly assist computational engineering design in many areas. In this paper an optimization approach to the magnetic design of a nuclear fusion reactor divertor is proposed and applied to a tokamak edge magnetic configuration in a first feasibility study. The approach is based on reduced models for magnetic field and plasma edge, which are integrated with a grid generator into one sensitivity code. The design objective chosen here for demonstrative purposes is to spread the divertor target heat load as much as possible over the entire target area. Constraints on the separatrix position are introduced to eliminate physically irrelevant magnetic field configurations during the optimization cycle. A gradient projection method is used to ensure stable cost function evaluations during optimization. The concept is applied to a configuration with typical Joint European Torus (JET) parameters and it automatically provides plausible configurations with reduced heat load.

  1. Tilting mode in field-reversed configurations

    SciTech Connect

    Schwarzmeier, J.L.; Barnes, D.C.; Lewis, H.R.; Seyler, C.E.; Shestakov, A.I.

    1982-01-01

    Field Reversed Configurations (FRCs) experimentally have exhibited remarkable stability on the magnetohydrodynamic (MHD) timescale, despite numerous MHD calculations showing FRCs to be unstable. It is easy to believe that local modes are stabilized by finite Larmor radius (FLR) effects, but more puzzling is the apparent stability of FRCs against global modes, where one would expect FLR effects to be less important. In this paper we study the tilting mode, which MHD has shown to be a rapidly growing global mode. The tilting mode in FRCs is driven by the pressure gradient, and magnetic compression and field line bending are the stabilizing forces. A schematic of the evolution of the tilting mode is shown. The tilting mode is considered dangerous, because it would lead to rapid tearing across the separatrix. Unlike spheromaks, the tilting mode in FRCs has a separatrix that is fixed in space, so that the mode is strictly internal.

  2. Rigid-rotor, field-reversed configuration

    SciTech Connect

    Conti, F. Giammanco, F.; Plasma Diagnostics and Technologies Ltd., Via Giuntini 63, 56023 Navacchio ; Wessel, F. J.; Binderbauer, M. W.; Bolte, N.; Morehouse, M.; Qerushi, A.; Rahman, H. U.; Roche, T.; Slepchenkov, M.

    2014-02-15

    The radial profiles, n(r), B{sub z}(r), and E{sub r}(r), for a Flux-Coil (“inductively driven”), Field-Reversed Configuration (FC-FRC) are measured and compared to the predictions of the Rigid-Rotor Model (RRM), which is an analytic, one-dimensional, time-independent, equilibrium description for the FRC. Injectors mounted on both ends of the confinement vessel provide a pre-fill plasma. Coaxial coils mounted outside the vacuum boundaries of the annular-confinement vessel accelerate the plasma and produce the FRC. The density profile is measured by laser interferometry, the magnetic-field profile using an in-situ probe array, and the electric-field profile using an in-situ, floating-probe array. Free parameters for each profile are measured, which also allow other intrinsic-plasma parameters to be determined, using computer-fit algorithms: null radius, radial thickness, plasma temperature, rotation frequencies, the latter of which are independently verified by spectroscopy. All radial profiles agree with the RRM predictions, for the experimental configuration, parameter regime, and specified-time interval studied here.

  3. Design and characterization of 2.45 GHz electron cyclotron resonance plasma source with magnetron magnetic field configuration for high flux of hyperthermal neutral beam

    SciTech Connect

    Kim, Seong Bong; Kim, Dae Chul; Yoo, Suk Jae; Namkung, Won; Cho, Moohyun

    2010-08-15

    A 2.45 GHz electron cyclotron resonance (ECR) source with a magnetron magnetic field configuration was developed to meet the demand of a hyperthermal neutral beam (HNB) flux on a substrate of more than 1x10{sup 15} cm{sup -2} s{sup -1} for industrial applications. The parameters of the operating pressure, ion density, electron temperature, and distance between the neutralization plate and the substrate for the HNB source are specified in a theoretical analysis. The electron temperature and the ion density are measured to characterize the ECR HNB source using a Langmuir probe and optical emission spectroscopy. The parameters of the ECR HNB source are in good agreement with the theoretically specified parameters.

  4. High field superconducting magnets

    NASA Technical Reports Server (NTRS)

    Hait, Thomas P. (Inventor); Shirron, Peter J. (Inventor)

    2011-01-01

    A superconducting magnet includes an insulating layer disposed about the surface of a mandrel; a superconducting wire wound in adjacent turns about the mandrel to form the superconducting magnet, wherein the superconducting wire is in thermal communication with the mandrel, and the superconducting magnet has a field-to-current ratio equal to or greater than 1.1 Tesla per Ampere; a thermally conductive potting material configured to fill interstices between the adjacent turns, wherein the thermally conductive potting material and the superconducting wire provide a path for dissipation of heat; and a voltage limiting device disposed across each end of the superconducting wire, wherein the voltage limiting device is configured to prevent a voltage excursion across the superconducting wire during quench of the superconducting magnet.

  5. Magnetic fields at Neptune

    SciTech Connect

    Ness, N.F. ); Acuna, M.H.; Burlaga, L.F.; Connerney, J.E.P.; Lepping, R.P. ); Neubauer, F.M. )

    1989-12-15

    The National Aeronautics and Space Administration Goddard Space Flight Center-University of Delaware Bartol Research Institute magnetic field experiment on the Voyager 2 spacecraft discovered a strong and complex intrinsic magnetic field of Neptune and an associated magnetosphere and magnetic tail. A maximum magnetic field of nearly 10,000 nanoteslas (1 nanotesla = 10{sup {minus}5} gauss) was observed near closest approach, at a distance of 1.18 R{sub N}. The planetary magnetic field between 4 and 15 R{sub N} can be well represented by an offset tilted magnetic dipole (OTD), displaced from the center of Neptune by the surprisingly large amount of 0.55 R{sub N} and inclined by 47{degrees} with respect to the rotation axis. Within 4 R{sub N}, the magnetic field representation must include localized sources or higher order magnetic multipoles, or both, which are not yet well determined. As the spacecraft exited the magnetosphere, the magnetic tail appeared to be monopolar, and no crossings of an imbedded magnetic field reversal or plasma neutral sheet were observed. The auroral zones are most likely located far from the rotation poles and may have a complicated geometry. The rings and all the known moons of Neptune are imbedded deep inside the magnetosphere, except for Nereid, which is outside when sunward of the planet. The radiation belts will have a complex structure owing to the absorption of energetic particles by the moons and rings of Neptune and losses associated with the significant changes in the diurnally varying magnetosphere configuration. In an astrophysical context, the magnetic field of Neptune, like that of Uranus, may be described as that of an oblique rotator.

  6. Global Stability of the Field Reversed Configuration

    SciTech Connect

    E.V. Belova; S.C. Jardin; H. Ji; R.M. Kulsrud; W. Park; M. Yamada

    2000-11-15

    New computational results are presented which provide a theoretical basis for the stability of the Field Reversed Configuration (FRC). The FRC is a compact toroid with negligible toroidal field in which the plasma is confined by a poloidal magnetic field associated with toroidal diamagnetic current. Although many MHD modes are predicted to be unstable, FRCs have been produced successfully by several formation techniques and show surprising macroscopic resilience. In order to understand this discrepancy, we have developed a new 3D nonlinear hybrid code (kinetic ions and fluid electrons), M3D-B, which is used to study the role of kinetic effects on the n = 1 tilt and higher n modes in the FRC. Our simulations show that there is a reduction in the tilt mode growth rate in the kinetic regime, but no absolute stabilization has been found for s bar less than or approximately equal to 1, where s bar is the approximate number of ion gyroradii between the field null and the separatrix. However, at low values of s bar, the instabilities saturate nonlinearly through a combination of a lengthening of the initial equilibrium and a modification of the ion distribution function. These saturated states persist for many Alfven times, maintaining field reversal.

  7. A high performance field-reversed configuration

    SciTech Connect

    Binderbauer, M. W.; Tajima, T.; Steinhauer, L. C.; Garate, E.; Tuszewski, M.; Smirnov, A.; Gota, H.; Barnes, D.; Deng, B. H.; Thompson, M. C.; Trask, E.; Yang, X.; Putvinski, S.; Rostoker, N.; Andow, R.; Aefsky, S.; Bolte, N.; Bui, D. Q.; Ceccherini, F.; Clary, R.; and others

    2015-05-15

    Conventional field-reversed configurations (FRCs), high-beta, prolate compact toroids embedded in poloidal magnetic fields, face notable stability and confinement concerns. These can be ameliorated by various control techniques, such as introducing a significant fast ion population. Indeed, adding neutral beam injection into the FRC over the past half-decade has contributed to striking improvements in confinement and stability. Further, the addition of electrically biased plasma guns at the ends, magnetic end plugs, and advanced surface conditioning led to dramatic reductions in turbulence-driven losses and greatly improved stability. Together, these enabled the build-up of a well-confined and dominant fast-ion population. Under such conditions, highly reproducible, macroscopically stable hot FRCs (with total plasma temperature of ∼1 keV) with record lifetimes were achieved. These accomplishments point to the prospect of advanced, beam-driven FRCs as an intriguing path toward fusion reactors. This paper reviews key results and presents context for further interpretation.

  8. Large-gap magnetic positioning system having advantageous configuration

    NASA Astrophysics Data System (ADS)

    Chong, Paul; Commandeur, Colin; Davis, Harold; Whitehead, Lorne

    1992-05-01

    A magnetic configuration was devised in which the positioned object is maintained in a stable orientation and position on one side of an opaque plane surface entirely by means of magnetic components on the other side of the plane. The system is effective with or without gravity, and can operate in any orientation. In this system, the positioned object need only contain a simple dipole magnet. The positioning components consist of a group of permanent magnets creating a magnetic field configuration which stabilizes the levitated dipole in all but one degree of freedom, and a magnetic position sensing and force feedback system to actively stabilize the object in the one unstable direction. The system utilizes very low power at equilibrium and can maintain gaps of 50 mm.

  9. The influence of elevated 50 Hz electric and magnetic fields on implanted cardiac pacemakers: the role of the lead configuration and programming of the sensitivity.

    PubMed

    Toivonen, L; Valjus, J; Hongisto, M; Metso, R

    1991-12-01

    The influence of the electromagnetic interference (EMI) on performance of 15 implanted cardiac pacemakers (12 generator models) was tested during exposure at a high voltage substation. All patients had an adequate spontaneous heart rate during the study. Tests were performed in the ventricular inhibited mode with unipolar sensing in all pacemakers and repeated with bipolar sensing in four pacemakers. The sensitivity was set to a regular, functionally proper level and then to the highest available level. Exposure was done to moderate (1.2-1.7 kV/m) and strong (7.0-8.0 kV/m) electric fields, which correspond to the immediate vicinity of 110 and 400 kV power lines, respectively. In moderate electric fields the output was inhibited in one pacemaker at regular sensitivity (1.7-3.0 mV) and in five pacemakers at the highest sensitivity (0.5-1.25 mV). In strong electric fields the output was inhibited in five pacemakers at regular sensitivity and several pacemakers converted to noise reversion mode at the highest sensitivity. In bipolar mode only one of four pacemakers at high sensitivity (0.5-1.0 mV) was inhibited in the strongest electric field, whereas all four did so in the unipolar mode. One pacemaker with unipolar sensitivity at 0.5 mV was interfered by 63 microT magnetic field. The results confirm that the programmed sensitivity level and the lead configuration markedly influence pacemakers' vulnerability to EMI. Bipolar sensing mode is rather safe in the presence of EMI, which is encountered in public environments. The programmable features of today's pacemakers permit individualized, less stringent safety measures to avoid electromagnetic hazards. PMID:1723194

  10. Eruptive solar magnetic fields

    NASA Technical Reports Server (NTRS)

    Low, B. C.

    1981-01-01

    The quasi-steady evolution of solar magnetic fields in response to gradual photospheric changes is considered, with particular attention given to the threshold of a sudden eruption in the solar atmosphere. The formal model of an evolving, force-free field dependent on two Cartesian coordinates is extended to a field which is not force free but in static equilibrium with plasma pressure and gravity. The basic physics is illustrated through the evolution of a loop-shaped electric current sheet enclosing a potential bipolar field with footpoints rooted in the photosphere. A free-boundary problem is posed and then solved for the equilibrium configuration of the current sheet in a hydrostatically supported isothermal atmosphere. As the footpoints move apart to spread a constant photospheric magnetic flux over a larger region, the equilibria available extend the field to increasing heights.

  11. Evolution of heliospheric magnetized configurations via topological invariants

    NASA Astrophysics Data System (ADS)

    Roth, Ilan

    2013-07-01

    The analogy between magnetohydrodynamics (MHD) and knot theory is utilized in presenting a new method for an analysis of stability and evolution of complex magnetic heliospheric flux tubes. Planar projection of a three-dimensional magnetic configuration depicts the structure as a two-dimensional diagram with crossings, to which one may assign mathematical operations leading to robust topological invariants. These invariants enrich the topological information of magnetic configurations beyond helicity. It is conjectured that the field which emerges from the solar photosphere is structured as one of the simplest knots-unknot or prime knot-and these flux ropes are then stretched while carried by the solar wind into the interplanetary medium. Preservation of invariants for small diffusivity and large cross section of the emerging magnetic flux makes them impervious to large scale reconnection, allowing us to predict the observed structures at 1 AU as elongated prime knots. Similar structures may be observed in magnetic clouds which got disconnected from their footpoints and in ion drop-out configurations from a compact flare source in solar impulsive solar events. Observation of small scale magnetic features consistent with prime knots may indicate spatial intermittency and non-Gaussian statistics in the turbulent cascade process. For flux tubes with higher resistivity, magnetic energy decay rate should decrease with increased knot complexity as the invariants are then harder to be violated. These observations could be confirmed if adjacent satellites happen to measure distinctly oriented magnetic fields with directionally varying suprathermal particle fluxes.

  12. Alternative poloidal field configurations for ITER

    SciTech Connect

    Bulmer, R.H.; Neilson, G.H.

    1997-09-02

    The US Home Team has investigated the physics and engineering issues for two alternate poloidal field coil configurations for ITER. The first is called the Segmented CS configuration, where all of the solenoid modules are pancake-wound. The second option, termed the Hybrid CS configuration, utilizes a layer-wound central module and pancake-wound end modules. Performance comparisons are presented for the baseline design and the two alternate PF configurations, characterizing the 21 MA reference scenario. Alternate operating modes such as reverse-shear operation and a 17 MA driven mode were evaluated, but are not reported here.

  13. Configurational analysis of an EBT reactor in various magnetic geometries

    SciTech Connect

    Owen, L.W.; Uckan, N.A.

    1980-01-01

    Optimization of vacuum field particle confinement in an ELMO Bumpy Torus (EBT) reactor has been considered. Several methods of improving the efficient utilization of magnetic fields and the particle confinement characteristics of a reactor have been analyzed. These include the use of (1) magnets with a large mirror ratio, (2) high field Nb/sub 3/Sn or Nb/sub 3/Sn/NbTi hybrid mirror coils, (3) split-wedge mirror coils, (4) aspect ratio enhancement (ARE) coils, and (5) recently developed field symmetrizing (SYM) coils. Of these, particle drift orbits and three-dimensional tensor pressure equilibrium calculations have shown that the ARE and SYM coils used in conjunction with high field magnets offer the most promise of good plasma performance in a smaller size (up to 50%) EBT reactor. The relative merits of each magnetic configuration are discussed, and the design characteristics are given.

  14. High-Energy Electron Confinement in a Magnetic Cusp Configuration

    NASA Astrophysics Data System (ADS)

    Park, Jaeyoung; Krall, Nicholas A.; Sieck, Paul E.; Offermann, Dustin T.; Skillicorn, Michael; Sanchez, Andrew; Davis, Kevin; Alderson, Eric; Lapenta, Giovanni

    2015-04-01

    We report experimental results validating the concept that plasma confinement is enhanced in a magnetic cusp configuration when β (plasma pressure/magnetic field pressure) is of order unity. This enhancement is required for a fusion power reactor based on cusp confinement to be feasible. The magnetic cusp configuration possesses a critical advantage: the plasma is stable to large scale perturbations. However, early work indicated that plasma loss rates in a reactor based on a cusp configuration were too large for net power production. Grad and others theorized that at high β a sharp boundary would form between the plasma and the magnetic field, leading to substantially smaller loss rates. While not able to confirm the details of Grad's work, the current experiment does validate, for the first time, the conjecture that confinement is substantially improved at high β . This represents critical progress toward an understanding of the plasma dynamics in a high-β cusp system. We hope that these results will stimulate a renewed interest in the cusp configuration as a fusion confinement candidate. In addition, the enhanced high-energy electron confinement resolves a key impediment to progress of the Polywell fusion concept, which combines a high-β cusp configuration with electrostatic fusion for a compact, power-producing nuclear fusion reactor.

  15. Magnetic Cusp Configuration of the SPL Plasma Generator

    NASA Astrophysics Data System (ADS)

    Kronberger, Matthias; Chaudet, Elodie; Favre, Gilles; Lettry, Jacques; Kchler, Detlef; Moyret, Pierre; Paoluzzi, Mauro; Prever-Loiri, Laurent; Schmitzer, Claus; Scrivens, Richard; Steyaert, Didier

    2011-09-01

    The Superconducting Proton Linac (SPL) is a novel linear accelerator concept currently studied at CERN. As part of this study, a new Cs-free, RF-driven external antenna H- plasma generator has been developed to withstand an average thermal load of 6 kW. The magnetic configuration of the new plasma generator includes a dodecapole cusp field and a filter field separating the plasma heating and H- production regions. Ferrites surrounding the RF antenna serve in enhancing the coupling of the RF to the plasma. Due to the space requirements of the plasma chamber cooling circuit, the cusp magnets are pushed outwards compared to Linac4 and the cusp field strength in the plasma region is reduced by 40% when N-S magnetized magnets are used. The cusp field strength and plasma confinement can be improved by replacing the N-S magnets with offset Halbach elements of which each consists of three magnetic sub-elements with different magnetization direction. A design challenge is the dissipation of RF power induced by eddy currents in the cusp and filter magnets which may lead to overheating and demagnetization. In view of this, a copper magnet cage has been developed that shields the cusp magnets from the radiation of the RF antenna.

  16. Magnetic Cusp Configuration of the SPL Plasma Generator

    SciTech Connect

    Kronberger, Matthias; Chaudet, Elodie; Favre, Gilles; Lettry, Jacques; Kuechler, Detlef; Moyret, Pierre; Paoluzzi, Mauro; Prever-Loiri, Laurent; Schmitzer, Claus; Scrivens, Richard; Steyaert, Didier

    2011-09-26

    The Superconducting Proton Linac (SPL) is a novel linear accelerator concept currently studied at CERN. As part of this study, a new Cs-free, RF-driven external antenna H{sup -} plasma generator has been developed to withstand an average thermal load of 6 kW. The magnetic configuration of the new plasma generator includes a dodecapole cusp field and a filter field separating the plasma heating and H{sup -} production regions. Ferrites surrounding the RF antenna serve in enhancing the coupling of the RF to the plasma. Due to the space requirements of the plasma chamber cooling circuit, the cusp magnets are pushed outwards compared to Linac4 and the cusp field strength in the plasma region is reduced by 40% when N-S magnetized magnets are used. The cusp field strength and plasma confinement can be improved by replacing the N-S magnets with offset Halbach elements of which each consists of three magnetic sub-elements with different magnetization direction. A design challenge is the dissipation of RF power induced by eddy currents in the cusp and filter magnets which may lead to overheating and demagnetization. In view of this, a copper magnet cage has been developed that shields the cusp magnets from the radiation of the RF antenna.

  17. Chaotic motion of charged particles in toroidal magnetic configurations.

    PubMed

    Cambon, Benjamin; Leoncini, Xavier; Vittot, Michel; Dumont, Rmi; Garbet, Xavier

    2014-09-01

    We study the motion of a charged particle in a tokamak magnetic field and discuss its chaotic nature. Contrary to most of recent studies, we do not make any assumption on any constant of the motion and solve numerically the cyclotron gyration using Hamiltonian formalism. We take advantage of a symplectic integrator allowing us to make long-time simulations. First considering an idealized magnetic configuration, we add a nongeneric perturbation corresponding to a magnetic ripple, breaking one of the invariant of the motion. Chaotic motion is then observed and opens questions about the link between chaos of magnetic field lines and chaos of particle trajectories. Second, we return to an axisymmetric configuration and tune the safety factor (magnetic configuration) in order to recover chaotic motion. In this last setting with two constants of the motion, the presence of chaos implies that no third global constant exists, we highlight this fact by looking at variations of the first order of the magnetic moment in this chaotic setting. We are facing a mixed phase space with both regular and chaotic regions and point out the difficulties in performing a global reduction such as gyrokinetics. PMID:25273181

  18. Chaotic motion of charged particles in toroidal magnetic configurations

    SciTech Connect

    Cambon, Benjamin; Leoncini, Xavier; Vittot, Michel; Dumont, Rémi; Garbet, Xavier

    2014-09-01

    We study the motion of a charged particle in a tokamak magnetic field and discuss its chaotic nature. Contrary to most of recent studies, we do not make any assumption on any constant of the motion and solve numerically the cyclotron gyration using Hamiltonian formalism. We take advantage of a symplectic integrator allowing us to make long-time simulations. First considering an idealized magnetic configuration, we add a nongeneric perturbation corresponding to a magnetic ripple, breaking one of the invariant of the motion. Chaotic motion is then observed and opens questions about the link between chaos of magnetic field lines and chaos of particle trajectories. Second, we return to an axisymmetric configuration and tune the safety factor (magnetic configuration) in order to recover chaotic motion. In this last setting with two constants of the motion, the presence of chaos implies that no third global constant exists, we highlight this fact by looking at variations of the first order of the magnetic moment in this chaotic setting. We are facing a mixed phase space with both regular and chaotic regions and point out the difficulties in performing a global reduction such as gyrokinetics.

  19. Magnetic fields at neptune.

    PubMed

    Ness, N F; Acua, M H; Burlaga, L F; Connerney, J E; Lepping, R P; Neubauer, F M

    1989-12-15

    The National Aeronautics and Space Administration Goddard Space Flight Center-University of Delaware Bartol Research Institute magnetic field experiment on the Voyager 2 spacecraft discovered a strong and complex intrinsic magnetic field of Neptune and an associated magnetosphere and magnetic tail. The detached bow shock wave in the supersonic solar wind flow was detected upstream at 34.9 Neptune radii (R(N)), and the magnetopause boundary was tentatively identified at 26.5 R(N) near the planet-sun line (1 R(N) = 24,765 kilometers). A maximum magnetic field of nearly 10,000 nanoteslas (1 nanotesla = 10(-5) gauss) was observed near closest approach, at a distance of 1.18 R(N). The planetary magnetic field between 4 and 15 R(N) can be well represented by an offset tilted magnetic dipole (OTD), displaced from the center of Neptune by the surprisingly large amount of 0.55 R(N) and inclined by 47 degrees with respect to the rotation axis. The OTD dipole moment is 0.133 gauss-R(N)(3). Within 4 R(N), the magnetic field representation must include localized sources or higher order magnetic multipoles, or both, which are not yet well determined. The obliquity of Neptune and the phase of its rotation at encounter combined serendipitously so that the spacecraft entered the magnetosphere at a time when the polar cusp region was directed almost precisely sunward. As the spacecraft exited the magnetosphere, the magnetic tail appeared to be monopolar, and no crossings of an imbedded magnetic field reversal or plasma neutral sheet were observed. The auroral zones are most likely located far from the rotation poles and may have a complicated geometry. The rings and all the known moons of Neptune are imbedded deep inside the magnetosphere, except for Nereid, which is outside when sunward of the planet. The radiation belts will have a complex structure owing to the absorption of energetic particles by the moons and rings of Neptune and losses associated with the significant changes in the diurnally varying magnetosphere configuration. In an astrophysical context, the magnetic field of Neptune, like that of Uranus, may be described as that of an "oblique" rotator. PMID:17756002

  20. The effects of magnetic nozzle configurations on plasma thrusters

    NASA Technical Reports Server (NTRS)

    York, Thomas M.

    1990-01-01

    Plasma thrusters have been operated at power levels from 10 kw to 0.1 MW. When these devices have had magnetic fields applied to them which form a nozzle configuration for the expanding plasma, they have shown marked increases in exhaust velocity which is in direct proportion to the magnitude of the applied field. Further, recent results have shown that electrode erosion may be influenced by applied magnetic fields. This research effort is directed to the experimental and computational study of the effects of applied magnetic field nozzles in the acceleration of plasma flows. Plasma source devices which eliminate the plasma interaction in normal thrusters are studied as most basic. Normal thruster configurations were studied without applied fields and with applied magnetic nozzle fields. Unique computational studies utilize existing codes which accurately include transport processes. Unique diagnostic studies supported the experimental studies to generate new data. Both computation and diagnostics were combined to indicate the physical mechanisms and transport properties that are operative in order to allow scaling and accurate prediction of thruster performance.

  1. The effects of magnetic nozzle configurations on plasma thrusters

    NASA Technical Reports Server (NTRS)

    York, Thomas M.

    1989-01-01

    Plasma thrusters have been operated at power levels from 10kW to 0.1MW. When these devices have had magnetic fields applied to them which form a nozzle configuration for the expanding plasma, they have shown marked increases in exhaust velocity which is in direct proportion to the magnitude of the applied field. Further, recent results have shown that electrode erosion may be influenced by applied magnetic fields. This research is directed to the experimental and computational study of the effects of applied magnetic field nozzles in the acceleration of plasma flows. Plasma source devices which eliminate the plasma interaction in normal thrusters are studied as most basic. Normal thruster configurations will be studied without applied fields and with applied magnetic nozzle fields. Unique computational studies will utilize existing codes which accurately include transport processes. Unique diagnostic studies will support the experimental studies to generate new data. Both computation and diagnostics will be combined to indicate the physical mechanisms and transport properties that are operative in order to allow scaling and accurate prediction of thruster performance.

  2. Magnetic field sensor

    NASA Astrophysics Data System (ADS)

    Silva, Nicolas

    2012-09-01

    Earlier papers1-3 in this journal have described experiments on measuring the magnetic fields of current-carrying wires and permanent magnets using magnetic field probes of various kinds. This paper explains how to use an iPad and the free app MagnetMeter-3D Vector Magnetometer and Accelerometer4 (compass HD) to measure the magnetic fields.

  3. Distinct magnetic signatures of fractional vortex configurations in multiband superconductors

    SciTech Connect

    Silva, R. M. da; Domínguez, D.; Aguiar, J. Albino

    2014-12-08

    Vortices carrying fractions of a flux quantum are predicted to exist in multiband superconductors, where vortex core can split between multiple band-specific components of the superconducting condensate. Using the two-component Ginzburg-Landau model, we examine such vortex configurations in a two-band superconducting slab in parallel magnetic field. The fractional vortices appear due to the band-selective vortex penetration caused by different thresholds for vortex entry within each band-condensate, and stabilize near the edges of the sample. We show that the resulting fractional vortex configurations leave distinct fingerprints in the static measurements of the magnetization, as well as in ac dynamic measurements of the magnetic susceptibility, both of which can be readily used for the detection of these fascinating vortex states in several existing multiband superconductors.

  4. Precession of an Electron-Magnetohydrodynamic Field-Reversed Configuration

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Griskey, M. C.; Urrutia, J. M.; Strohmaier, K. D.

    2002-05-01

    A field-reversed configuration is generated in a large laboratory plasma in the parameter regime of electron magnetohydrodynamics. During its free relaxation, the magnetic moment is observed to precess when tilted from its original axis. The precession velocity is the electron drift velocity in the toroidal current layer. The precession is a manifestation of frozen-in field lines in a moving electron fluid.

  5. Classification of magnetic configurations for the cloverleaf divertor

    NASA Astrophysics Data System (ADS)

    Ryutov, D. D.; Umansky, M. V.

    2014-10-01

    The cloverleaf divertor is based on magnetic configuration with the third-order poloidal field null. If the currents in the divertor coils are somewhat different from those required for the generation of the third-order null, the latter splits into three closely-spaced first-order nulls. One can move these nulls around by changing the currents in the divertor coils. A large variety of configurations can be created. In this study we provide general topological classification of all configurations possible in the case of the coils situated at sufficiently large distance from the nulls. It turns out that these configurations can be identified by a single dimensionless parameter, analogously to what has been done for the snowflake divertor. In addition to this general classification, we evaluate the length scales of the field variation in each of the three nulls, as well as connection lengths and local magnetic shear for a variety of configurations. Work performed for U.S. DOE by LLNL under Contract DE-AC52-07NA27344.

  6. Martian external magnetic field proxies

    NASA Astrophysics Data System (ADS)

    Langlais, Benoit; Civet, Francois

    2015-04-01

    Mars possesses no dynamic magnetic field of internal origin as it is the case for the Earth or for Mercury. Instead Mars is characterized by an intense and localized magnetic field of crustal origin. This field is the result of past magnetization and demagnetization processes, and reflects its evolution. The Interplanetary Magnetic Field (IMF) interacts with Mars' ionized environment to create an external magnetic field. This external field is weak compared to lithospheric one but very dynamic, and may hamper the detailed analysis of the internal magnetic field at some places or times. Because there are currently no magnetic field measurements made at Mars' surface, it is not possible to directly monitor the external field temporal variability as it is done in Earth's ground magnetic observatories. In this study we examine to indirect ways of quantifying this external field. First we use the Advanced Composition Explorer (ACE) mission which measures the solar wind about one hour upstream of the bow-shock resulting from the interaction between the solar wind and the Earth's internal magnetic field. These measurements are extrapolated to Mars' position taking into account the orbital configurations of the Mars-Earth system and the velocity of particles carrying the IMF. Second we directly use Mars Global Surveyor magnetic field measurements to quantify the level of variability of the external field. We subtract from the measurements the internal field which is otherwise modeled, and bin the residuals first on a spatial and then on a temporal mesh. This allows to compute daily or semi daily index. We present a comparison of these two proxies and demonstrate their complementarity. We also illustrate our analysis by comparing our Martian external field proxies to terrestrial index at epochs of known strong activity. These proxies will especially be useful for upcoming magnetic field measurements made around or at the surface of Mars.

  7. Magnetic refrigeration: recent developments and alternative configurations

    NASA Astrophysics Data System (ADS)

    Almanza, Morgan; Kedous-Lebouc, Afef; Yonnet, Jean-Paul; Legait, Ulrich; Roudaut, Julien

    2015-07-01

    Magnetic refrigeration, based on magnetocaloric effect, is an upcoming environmentaly friendly technology with a high potential to improve energy efficiency and to reduce greenhouse gas emission. It is a multidisciplinary research theme and its real emergence requires, to overcome scientific and technical issues related to both material and system. This paper presents the state of the art in magnetic cooling, the main recent works achieved and discusses in more details the thermodynamic phenomenon according to the G2Elab experience in the field. Contribution to the topical issue "Electrical Engineering Symposium (SGE 2014)", edited by Adel Razek

  8. Magnetic field line Hamiltonian

    SciTech Connect

    Boozer, A.H.

    1985-02-01

    The basic properties of the Hamiltonian representation of magnetic fields in canonical form are reviewed. The theory of canonical magnetic perturbation theory is then developed and applied to the time evolution of a magnetic field embedded in a toroidal plasma. Finally, the extension of the energy principle to tearing modes, utilizing the magnetic field line Hamiltonian, is outlined.

  9. WE-G-17A-08: Electron Gun Operation for in Line MRI-Linac Configurations: An Assessment of Beam Fidelity and Recovery Techniques for Different SIDs and Magnetic Field Strengths

    SciTech Connect

    Whelan, B; Keall, P; Constantin, D; Holloway, L; Kolling, S; Oborn, B; Fahrig, R

    2014-06-15

    Purpose: To test the functionality of medical electron guns within the fringe field of a purpose built superconducting MRI magnet, and to test different recovery techniques for a variety of imaging field strengths and SIDs. Methods: Three different electron guns were simulated using Finite Element Modelling; a standard diode gun, a standard triode gun, and a novel diode gun designed to operate within parallel magnetic fields. The approximate working regime of each gun was established by assessing exit current in constant magnetic fields of varying strength and defining ‘working’ as less than 10% change in injection current. Next, the 1.0T MRI magnet was simulated within Comsol Multiphysics. The coil currents in this model were also scaled to produce field strengths of .5, 1, 1.5 and 3T. Various magnetic shield configurations were simulated, varying the SID from 800 to 1300mm. The average magnetic field within the gun region was assessed together with the distortion in the imaging volume - greater than 150uT distortion was considered unacceptable. Results: The conventional guns functioned in fields of less than 7.5mT. Conversely, the redesigned diode required fields greater than .1T to function correctly. Magnetic shielding was feasible for SIDS of greater than 1000mm for field strengths of .5T and 1T, and 1100mm for 1.5 and 3.0T. Beyond these limits shielding resulted in unacceptable MRI distortion. In contrast, the redesigned diode could perform acceptably for SIDs of less than 812, 896, 931, and 974mm for imaging strengths of 0.5, 1.0, 1.5, 3.0T. Conclusions: For in-line MRIlinac configurations where the electron gun is operating in low field regions, shielding is a straight forward option. However, as magnetic field strength increases and the SID is reduced, shielding results in too great a distortion in the MRI and redesigning the electron optics is the preferable solution. The authors would like to acknowledge funding from the National Health and Research Council (AUS), National Institute of Health (NIH), and Cancer Institute NSW.

  10. Magnetic field fluctuations during substorms

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.

    1971-01-01

    Before a magnetospheric substorm and during its early phases the magnetic field magnitude in the geomagnetic tail increases and field lines in the nighttime hemisphere assume a more tail-like configuration. Before the substorm onset a minimum amount of magnetic flux is observed to cross the neutral sheet which means that the neutral sheet currents attain their most earthward locations and their greatest current densities. This configuration apparently results from an increased transport of magnetic flux to the tail caused by a southward interplanetary magnetic field. The field begins relaxing toward a more dipolar configuration at the time of a substorm onset with the recovery probably occurring first between 6 and 10 R sub E. This recovery must be associated with magnetospheric convection which restores magnetic flux to the dayside hemisphere. Field aligned currents appear to be required to connect magnetospheric currents to the auroral electrojets, implying that a net current flows in a limited range of longitudes. Space measurements supporting current systems are limited. More evidence exists for the occurrence of double current sheets which do not involve net current at a given longitude.

  11. Magnetic field mapper

    NASA Technical Reports Server (NTRS)

    Masters, R. M.; Stenger, F. J.

    1969-01-01

    Magnetic field mapper locates imperfections in cadmium sulphide solar cells by detecting and displaying the variations of the normal component of the magnetic field resulting from current density variations. It can also inspect for nonuniformities in other electrically conductive materials.

  12. Kinetic Stability of the Field Reversed Configuration

    SciTech Connect

    E.V. Belova; R.C. Davidson; H. Ji; and M. Yamada

    2002-07-09

    New computational results are presented which advance the understanding of the stability properties of the Field-Reversed Configuration (FRC). The FRC is an innovative confinement approach that offers a unique fusion reactor potential because of its compact and simple geometry, translation properties, and high plasma beta. One of the most important issues is FRC stability with respect to low-n (toroidal mode number) MHD modes. There is a clear discrepancy between the predictions of standard MHD theory that many modes should be unstable on the MHD time scale, and the observed macroscopic resilience of FRCs in experiments.

  13. Confinement of translated field-reversed configurations

    NASA Astrophysics Data System (ADS)

    Tuszewski, M.; Armstrong, W. T.; Chrien, R. E.; Klingner, P. L.; McKenna, K. F.; Rej, D. J.; Sherwood, E. G.; Siemon, R. E.

    1986-03-01

    The confinement properties of translating field-reversed configurations (FRC) in the FRX-C/T device [Phys. Fluids 29, (1986)] are analyzed and compared to previous data without translation and to available theory. Translation dynamics do not appear to appreciably modify the FRC confinement. Some empirical scaling laws with respect to various plasma parameters are extracted from the data. These are qualitatively similar to those obtained in the TRX-1 device [Phys. Fluids 28, 888 (1985)] without translation and with a different formation method. Translation with a static gas fill offers new opportunities such as improved particle confinement or refueling of the FRC particle inventory.

  14. THE RADIO PROPERTIES AND MAGNETIC FIELD CONFIGURATION IN THE CRAB-LIKE PULSAR WIND NEBULA G54.1+0.3

    SciTech Connect

    Lang, Cornelia C.; Clubb, Kelsey I.; Wang, Q. Daniel; Lu Fangjun

    2010-02-01

    We present a multifrequency radio investigation of the Crab-like pulsar wind nebula (PWN) G54.1+0.3 using the Very Large Array. The high resolution of the observations reveals that G54.1+0.3 has a complex radio structure which includes filamentary and loop-like structures that are magnetized, a diffuse extent similar to the associated diffuse X-ray emission. But the radio and X-ray structures in the central region differ strikingly, indicating that they trace very different forms of particle injection from the pulsar and/or particle acceleration in the nebula. No spectral index gradient is detected in the radio emission across the PWN, whereas the X-ray emission softens outward in the nebula. The extensive radio polarization allows us to image in detail the intrinsic magnetic field, which is well-ordered and reveals that a number of loop-like filaments are strongly magnetized. In addition, we determine that there are both radial and toroidal components to the magnetic field structure of the PWN. Strong mid-infrared (IR) emission detected in Spitzer Space Telescope data is closely correlated with the radio emission arising from the southern edge of G54.1+0.3. In particular, the distributions of radio and X-ray emission compared with the mid-IR emission suggest that the PWN may be interacting with this interstellar cloud. This may be the first PWN where we are directly detecting its interplay with an interstellar cloud that has survived the impact of the supernova explosion associated with the pulsar's progenitor.

  15. Simultaneous effects of radial magnetic field and wall properties on peristaltic flow of Carreau-Yasuda fluid in curved flow configuration

    NASA Astrophysics Data System (ADS)

    Hayat, T.; Tanveer, A.; Alsaadi, F.

    2015-12-01

    The objective of present article is to address the magnetohydrodynamic (MHD) peristaltic flow of Carreau-Yasuda fluid in a curved geometry. The channel boundaries satisfy wall slip and compliant properties. The fluid is electrically conducting through an applied magnetic field in the radial direction. Heat transfer is also studied. Governing equation comprised the viscous dissipation effects. The non-linear expressions are first obtained and then approximated using long wavelength and low Reynolds number considerations. The resulting systems are solved for the series solutions. The expressions of velocity, temperature, heat transfer coefficient and stream function are obtained and analyzed via graphical illustrations.

  16. The configuration of the Brazilian scientific field.

    PubMed

    Barata, Rita B; Arago, Erika; de Sousa, Luis E P Fernandes; Santana, Taris M; Barreto, Mauricio L

    2014-03-01

    This article describes the configuration of the scientific field in Brazil, characterizing the scientific communities in every major area of knowledge in terms of installed capacity, ability to train new researchers, and capacity for academic production. Empirical data from several sources of information are used to characterize the different communities. Articulating the theoretical contributions of Pierre Bourdieu, Ludwik Fleck, and Thomas Kuhn, the following types of capital are analyzed for each community: social capital (scientific prestige), symbolic capital (dominant paradigm), political capital (leadership in S & T policy), and economic capital (resources). Scientific prestige is analyzed by taking into account the volume of production, activity index, citations, and other indicators. To characterize symbolic capital, the dominant paradigms that distinguish the natural sciences, the humanities, applied sciences, and technology development are analyzed theoretically. Political capital is measured by presidency in one of the main agencies in the S & T national system, and research resources and fellowships define the economic capital. The article discusses the composition of these different types of capital and their correspondence to structural capacities in various communities with the aim of describing the configuration of the Brazilian scientific field. PMID:24676181

  17. Magnetosphere of Uranus: plasma sources, convection, and field configuration

    SciTech Connect

    Voigt, G.; Hill, T.W.; Dessler, A.J.

    1983-03-01

    At the time of the Voyager 2 flyby of Uranus, the planetary rotational axis will be roughly antiparallel to the solar wind flow. If Uranus has a magnetic dipole moment that is approximately aligned with its spin axis, and if the heliospheric shock has not been encountered, we will have the rare opportunity to observe a ''pole-on'' magnetosphere as discussed qualitatively by Siscoe. Qualitative arguments based on analogy with Earth, Jupiter, and Saturn suggest that the magnetosphere of Uranus may lack a source of plasma adequate to produce significant internal currents, internal convection, and associated effects. In order to provide a test of this hypothesis with the forthcoming Voyager measurements, we have constructed a class of approximately self-consistent quantitative magnetohydrostatic equilibrium configurations for a pole-on magnetosphere with variable plasma pressure parameters. Given a few simplifying assumptions, the geometries of the magnetic field and of the tail current sheet can be computed for a given distribution of trapped plasma pressure. The configurations have a single funnel-shaped polar cusp that points directly into the solar wind and a cylindrical tail plasma sheet whose currents close within the tail rather than on the tail magnetopause, and whose length depends on the rate of decrease of thermal plasma pressure down the tail. Interconnection between magnetospheric and interplanetary fields results in a highly asymmetric tail-field configuration. These features were predicted qualtitatively by Siscoe; the quantitative models presented here may be useful in the interpretation of Voyager encounter results.

  18. Photospheric magnetic fields

    NASA Technical Reports Server (NTRS)

    Howard, R.

    1972-01-01

    Knowledge on the nature of magnetic fields on the solar surface is reviewed. At least a large part of the magnetic flux in the solar surface is confined to small bundles of lines of force within which the field strength is of the order of 500 gauss. Magnetic fields are closely associated with all types of solar activity. Magnetic flux appears at the surface at the clearly defined birth or regeneration of activity of an active region. As the region ages, the magnetic flux migrates to form large-scale patterns and the polar fields. Some manifestations of the large-scale distribution are discussed.

  19. Magnetic configuration dependence of magnetoresistance in a Fe-porphyrin-like carbon nanotube spintronic device

    SciTech Connect

    Zeng, Jing; Chen, Ke-Qiu

    2014-01-20

    By using nonequilibrium Green's functions in combination with the density functional theory, we investigate the spin-dependent transport properties in a Fe-porphyrin-like carbon nanotube spintronic device. The results show that magnetoresistance ratio is strongly dependent on the magnetic configuration of the Fe-porphyrin-like carbon nanotube. Under the application of the external magnetic field, the magnetoresistance ratio of the device can be increased from about 19% to about 1020% by tuning the magnetic configuration in the device. Our results confirm that the magnetic configuration is a key factor for obtaining a high-performance spintronic device.

  20. Reducing Field Distortion in Magnetic Resonance Imaging

    NASA Technical Reports Server (NTRS)

    Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

    2010-01-01

    A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

  1. Magnetic Fields and Plasmas

    SciTech Connect

    Schep, T.J.

    2004-03-15

    Plasmas and magnetic fields are inseparably related in numerous physical circumstances. This is not only the case in natural occurring plasmas like the solar corona and the earth magnetic tail, but also in laboratory plasmas like tokamaks and stellarators.

  2. Plasma-wall interaction in Hall thrusters with magnetic lens configuration

    SciTech Connect

    Brieda, Lubos; Keidar, Michael

    2012-06-15

    Some recently developed Hall thrusters utilize a magnetic field configuration in which the field lines penetrate the thruster walls at a high incidence angle. This so-called magnetic lens leads to an electric field pointing away from the walls, which is expected to reduce ion losses and improve thruster efficiency. This configuration also introduces an interesting behavior in the sheath formation. At sufficiently large angles, ions are repelled from the wall, and sheath collapse is expected. We use a plasma simulation code to investigate this phenomenon in detail. We consider the role of the magnetic field incidence angle, secondary electron emission, and a magnetic mirror. Numerical study confirms the theoretical predictions, and at large angles, ions are seen to turn away from the wall. We also consider the role of the magnetic field geometry on ion wall flux and channel erosion, and observe reduction in both quantities as the magnetic field incidence angle is increased.

  3. Hybrid equilibria of field-reversed configurations

    SciTech Connect

    Steinhauer, Loren C.

    2011-11-15

    This paper presents the first detailed model of hybrid equilibria relevant to field-reversed configuration experiments, leading to a system of equations that are solved for a range of fully two-dimensional equilibria. Several features of these highly kinetic objects are explored. The range of equilibria is primarily dependent on a single free parameter related to the flow shear. The level of flow shear has a profound effect on the structure, especially near the separatrix. This likely has a strong influence on both stability and transport properties. Higher flow shear is favorable in every respect. The key factor behind the influence of flow shear is the relatively rapid end loss of unconfined ions. Differences between hybrid and static-fluid equilibrium models are highlighted, including the integrity of surface functions, the effect of flow shear, and the scrape-off layer thickness.

  4. Magnetoconvection in sheared magnetic fields

    SciTech Connect

    Bian, N. H.; Garcia, O. E.

    2008-10-15

    The development of magnetoconvection in a sheared magnetic field is investigated. The equilibrium magnetic field B{sub 0} is horizontal and its orientation varies linearly along the vertical axis. Preliminary consideration of the transition from the inertial to the viscous regime of the gravitational resistive interchange instability, reveals that the latter is characterized by the existence of viscoresistive boundary layers of vertical width which scales as Q{sup -1/6}, where Q is the Chandrasekhar number. The situation is analogous to the one encountered in magnetically confined laboratory plasmas, where convective flows are constrained by the magnetic shear to develop in boundary layers located around resonant magnetic surfaces in order to fulfill the 'interchange condition'k{center_dot}B{sub 0}=0, where k is the wave vector of the magnetic perturbation. It follows that when the effect of thermal diffusion is taken into account in the process, convection can only occur above a certain critical value of the Rayleigh number which scales as Q{sup 2/3} for large Q. At the onset, the convection pattern is a superposition of identically thin convective rolls everywhere aligned with the local magnetic field lines and which therefore adopt the magnetic field geometry, a situation also reminiscent of the penumbra of sunspots. Using this degeneracy, equations describing the weakly nonlinear state are obtained and discussed. A reduced magnetohydrodynamic description of magnetoconvection is introduced. Since it is valid for arbitrary magnetic field configurations, it allows a simple extension to the case where there exists an inclination between the direction of gravity and the plane spanned by the equilibrium magnetic field. These reduced magnetohydrodynamic equations are proposed as a powerful tool for further investigations of magnetoconvection in more complex field line geometries.

  5. Inhomogeneous configurations of magnetization of ferromagnetic films with biaxial anisotropy

    SciTech Connect

    Dzhezherya, Yu. I.; Sorockin, M. V. Bubuk, E. A.

    2007-10-15

    The system of the Landau-Lifshitz equations and magnetostatic equations for a ferromagnetic film with biaxial anisotropy and a Q-factor smaller than unity is reduced to a single scalar equation for the magnetostatic potential. Such a procedure is possible if the magnetization modulation scale in the sample considerably exceeds the characteristic magnetic length. The solutions to this equation describing inhomogeneous periodic magnetic configurations are obtained. The energy analysis of these configurations is carried out.

  6. Formation of Field-reversed-Configuration Plasma with Punctuated-betatron-orbit Electrons

    SciTech Connect

    Welch, D. R.; Cohen, S. A.; Genoni, T. C.; Glasser, A. H.

    2010-06-28

    We describe ab initio, self-consistent, 3D, fully electromagnetic numerical simulations of current drive and field-reversed-configuration plasma formation by odd-parity rotating magnetic fields (RMFo). Magnetic-separatrix formation and field reversal are attained from an initial mirror configuration. A population of punctuated-betatron-orbit electrons, generated by the RMFo, carries the majority of the field-normal azimuthal electrical current responsible for field reversal. Appreciable current and plasma pressure exist outside the magnetic separatrix whose shape is modulated by the RMFo phase. The predicted plasma density and electron energy distribution compare favorably with RMFo experiments. __________________________________________________

  7. Optimized configurations of autostable superconducting magnetic bearings for practical applications

    SciTech Connect

    Schoechlin, A.; Ritter, T.; Bornemann, H.J.

    1995-11-01

    In order to establish an optimized bearing design for a flywheel for energy storage, the authors have studied model bearing configurations involving bulk YBCO pellets and double-dipole magnet configurations. They were interested to see what is the correlation between the maximum attainable levitation force, measured for a typical bearing gap of 3 mm, and the separation between the magnetic poles. Equal polarity (north-north) and alternate polarity (north-south) configurations were investigated. The maximum levitation force was obtained with the alternate polarity arrangement for a separation between the magnetic poles of 6 mm. It represents an increase of 19% compared to a non-optimized configuration. The experiments demonstrate that configurations of superconducting magnetic bearings can be optimized to obtain better levitation properties.

  8. Three-dimensional prominence-hosting magnetic configurations: Creating a helical magnetic flux rope

    SciTech Connect

    Xia, C.; Keppens, R.; Guo, Y.

    2014-01-10

    The magnetic configuration hosting prominences and their surrounding coronal structure is a key research topic in solar physics. Recent theoretical and observational studies strongly suggest that a helical magnetic flux rope is an essential ingredient to fulfill most of the theoretical and observational requirements for hosting prominences. To understand flux rope formation details and obtain magnetic configurations suitable for future prominence formation studies, we here report on three-dimensional isothermal magnetohydrodynamic simulations including finite gas pressure and gravity. Starting from a magnetohydrostatic corona with a linear force-free bipolar magnetic field, we follow its evolution when introducing vortex flows around the main polarities and converging flows toward the polarity inversion line near the bottom of the corona. The converging flows bring the feet of different loops together at the polarity inversion line, where magnetic reconnection and flux cancellation happen. Inflow and outflow signatures of the magnetic reconnection process are identified, and thereby the newly formed helical loops wind around preexisting ones so that a complete flux rope grows and ascends. When a macroscopic flux rope is formed, we switch off the driving flows and find that the system relaxes to a stable state containing a helical magnetic flux rope embedded in an overlying arcade structure. A major part of the formed flux rope is threaded by dipped field lines that can stably support prominence matter, while the total mass of the flux rope is in the order of 4-5 10{sup 14} g.

  9. Magnetic field generator

    DOEpatents

    Krienin, Frank

    1990-01-01

    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.

  10. On Cosmic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Florido, E.; Battaner, E.

    2010-12-01

    Magnetic fields are present in all astrophysical media. However, many models and interpretations of observations often ignore them, because magnetic fields are difficult to handle and because they produce complicated morphological features. Here we will comment on the basic intuitive properties, which even if not completely true, provide a first guiding insight on the physics of a particular astrophysical problem. These magnetic properties are not mathematically demonstrated here. How magnetic fields evolve and how they introduce dynamical effects are considered, also including a short comment on General Relativity Magnetohydrodynamics. In a second part we consider some audacious and speculative matters. They are answers to three questions: a) How draw a cube without lifting the pencil from the paper so that when the pen passes through the same side do in the same direction? B) Are MILAGRO anisotropies miraculous? C) Do cosmic magnetic lenses exist?. The last two questions deal with issues related with the interplay between magnetic fields and cosmic ray propagation.

  11. Magnetic Fields in Galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    Magnetic fields are a major agent in the interstellar medium. They contribute significantly to the total pressure which balances the gas disk against gravitation. They affect the gas flows in spiral arms (Gmez and Cox, 2002). The effective sound speed of the gas is increased by the presence of strong fields which reduce the shock strength. The interstellar fields are closely connected to gas clouds. They affect the dynamics of the gas clouds (Elmegreen, 1981; de Avillez and Breitschwerdt, 2004). The stability and evolution of gas clouds are also influenced by magnetic fields, but it is not understood how (Crutcher, 1999; see Chap. 7). Magnetic fields are essential for the onset of star formation as they enable the removal of angular momentum from the protostellar cloud during its collapse (magnetic braking, Mouschovias, 1990). Strong fields may shift the stellar mass spectrum towards the more massive stars (Mestel, 1990). MHD turbulence distributes energy from supernova explosions within the ISM (Subramanian, 1998) and regenerates the field via the dynamo process (Wielebinski, R., Krause, 1993, Beck et al., 1996; Sect. 6). Magnetic reconnection is a possible heating source for the ISM and halo gas (Birk et al., 1998). Magnetic fields also control the density and distribution of cosmic rays in the ISM. A realistic model for any process in the ISM needs basic information about the magnetic field which has to be provided by observations.

  12. Structure of magnetic fields in intracluster cavities

    NASA Astrophysics Data System (ADS)

    Gourgouliatos, Konstantinos Nektarios; Braithwaite, Jonathan; Lyutikov, Maxim

    2010-12-01

    Observations of clusters of galaxies show ubiquitous presence of X-ray cavities, presumably blown by the active galactic nuclei (AGN) jets. We consider magnetic field structures of these cavities. Stability requires that they contain both toroidal and poloidal magnetic fields, while realistic configurations should have vanishing magnetic field on the boundary. For axisymmetric configurations embedded in unmagnetized plasma, the continuity of poloidal and toroidal magnetic field components on the surface of the bubble then requires solving the elliptical Grad-Shafranov equation with both Dirichlet and Neumann boundary conditions. This leads to a double eigenvalue problem, relating the pressure gradients and the toroidal magnetic field to the radius of the bubble. We have found fully analytical stable solutions. This result is confirmed by numerical simulation. We present synthetic X-ray images and synchrotron emission profiles and we evaluate the rotation measure for radiation transversing the bubble.

  13. Magnetic Fields in the Milky Way

    NASA Astrophysics Data System (ADS)

    Haverkorn, Marijke

    This chapter presents a review of observational studies to determine the magnetic field in the Milky Way, both in the disk and in the halo, focused on recent developments and on magnetic fields in the diffuse interstellar medium. I discuss some terminology which is confusingly or inconsistently used and try to summarize current status of our knowledge on magnetic field configurations and strengths in the Milky Way. Although many open questions still exist, more and more conclusions can be drawn on the large-scale and small-scale components of the Galactic magnetic field. The chapter is concluded with a brief outlook to observational projects in the near future.

  14. Interplanetary stream magnetism: Kinematic effects. [solar magnetic fields and wind

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Barouch, E.

    1974-01-01

    The particle density, and the magnetic field intensity and direction are calculated in corotating streams of the solar wind, assuming that the solar wind velocity is constant and radial and that its azimuthal variations are not two rapid. The effects of the radial velocity profile in corotating streams on the magnetic fields were examined using kinematic approximation and a variety of field configurations on the inner boundary. Kinematic and dynamic effects are discussed.

  15. Classification and synthesis of permanent magnet bearing configurations

    SciTech Connect

    Delamare, J.; Rulliere, E.; Yonnet, J.P.

    1995-11-01

    Quite a number of configurations allow one to get passive permanent magnet thrust or radial bearings. However, most of existing devices are based on the same two or three structures. In many cases, a different geometrical structure keeping the same magnetic and mechanical characteristics would allow a simple and cheaper realization. The authors present her a synthesis of passive bearings allowing original structures.

  16. Dynamic processes in field-reversed-configuration compact toroids

    NASA Astrophysics Data System (ADS)

    Rej, D. J.

    The dynamic processes involved in field-reversed configuration (FRC) formation, translation, and compression are reviewed. Though the FRC is related to the field-reversed mirror concept, the formation method used in most experiments is a variant of the field-reversed THETA-pinch. Formation of the FRC eqilibrium occurs rapidly, usually in less than 20 microsec. The formation sequence consists of several coupled processes: preionization; radial implosion and compression; magnetic field line closure; axial contraction; equilibrium formation. Recent experiments and theory have led to a significantly improved understanding of these processes; however, the experimental method still relies on a somewhat empirical approach which involves the optimization of initial preionization plasma parameters and symmetry. New improvements in FRC formation methods include the use of lower voltages which extrapolate better to larger devices. The axial translation of compact toroid plasmas offers an attractive engineering convenience in a fusion reactor. FRC translation has been demonstrated in experiments worldwide, and these plasmas are found to be robust, moving at speeds up to the Alfven velocity over distances of up to 16 m, with no degradation in the confinement. Compact toroids are ideal for magnetic compression. Translated FRCs have been compressed and heated by imploding liners. Upcoming experiments will rely on external flux compression to heat a translater FRC at 1-GW power levels.

  17. High-field superconducting nested coil magnet

    NASA Technical Reports Server (NTRS)

    Laverick, C.; Lobell, G. M.

    1970-01-01

    Superconducting magnet, employed in conjunction with five types of superconducting cables in a nested solenoid configuration, produces total, central magnetic field strengths approaching 70 kG. The multiple coils permit maximum information on cable characteristics to be gathered from one test.

  18. Magnetic Configurations in Co/Cu Multilayered Nanowires: Evidence of Structural and Magnetic Interplay.

    PubMed

    Reyes, D; Biziere, N; Warot-Fonrose, B; Wade, T; Gatel, C

    2016-02-10

    Off-axis electron holography experiments have been combined with micromagnetic simulations to study the remnant magnetic states of electrodeposited Co/Cu multilayered nanocylinders. Structural and chemical data obtained by transmission electron microscopy have been introduced in the simulations. Three different magnetic configurations such as an antiparallel coupling of the Co layers, coupled vortices, and a monodomain-like state have been quantitatively mapped and simulated. While most of the wires present the same remnant state whatever the direction of the saturation field, we show that some layers can present a change from an antiparallel coupling to vortices. Such a configuration can be of particular interest to design nano-oscillators with two different working frequencies. PMID:26783831

  19. Four-state magnetic configuration in a tri-layer asymmetric ring

    NASA Astrophysics Data System (ADS)

    Popescu, Horia; Fortuna, Franck; Delaunay, Renaud; Spezzani, Carlo; Lopez-Flores, Victor; Jaouen, Nicolas; Sacchi, Maurizio

    2015-11-01

    Ring-shaped multilayered sub-micron dots have the potential for the development of non-volatile multi-bit devices. We show that a Co/Cu/FeNi asymmetric ring can take four distinct remanent magnetic states, each one stabilized by applying a magnetic field pulse along one of four in-plane orthogonal directions. We use element selective x-ray holography for imaging the Co magnetic configuration following a magnetic pulse. Micro-magnetic simulations support our experimental findings; they also provide an estimate of the system magnetization dynamics, setting out the conditions for further time-resolved experiments.

  20. Dynamic Magnetic Field Applications for Materials Processing

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Grugel, Richard N.; Motakef, S.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Magnetic fields, variable in time and space, can be used to control convection in electrically conducting melts. Flow induced by these fields has been found to be beneficial for crystal growth applications. It allows increased crystal growth rates, and improves homogeneity and quality. Particularly beneficial is the natural convection damping capability of alternating magnetic fields. One well-known example is the rotating magnetic field (RMF) configuration. RMF induces liquid motion consisting of a swirling basic flow and a meridional secondary flow. In addition to crystal growth applications, RMF can also be used for mixing non-homogeneous melts in continuous metal castings. These applied aspects have stimulated increasing research on RMF-induced fluid dynamics. A novel type of magnetic field configuration consisting of an axisymmetric magnetostatic wave, designated the traveling magnetic field (TMF), has been recently proposed. It induces a basic flow in the form of a single vortex. TMF may find use in crystal growth techniques such as the vertical Bridgman (VB), float zone (FZ), and the traveling heater method. In this review, both methods, RMF and TMF are presented. Our recent theoretical and experimental results include such topics as localized TMF, natural convection dumping using TMF in a vertical Bridgman configuration, the traveling heater method, and the Lorentz force induced by TMF as a function of frequency. Experimentally, alloy mixing results, with and without applied TMF, will be presented. Finally, advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, will be discussed.

  1. Magnetic field dosimeter development

    SciTech Connect

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

    1980-09-01

    In recent years there has been increased concern over potential health hazards related to exposure of personnel to magnetic fields. If exposure standards are to be established, then a means for measuring magnetic field dose must be available. To meet this need, the Department of Energy has funded development of prototype dosimeters at the Battelle Pacific Northwest Laboratory. This manual reviews the principle of operation of the dosimeter and also contains step-by-step instructions for its operation.

  2. Magnetosheath magnetic field variability

    NASA Technical Reports Server (NTRS)

    Sibeck, D. G.

    1994-01-01

    A case study using simulations IRM and CCE observations demonstrates that transient magnetospheric events correspond to pressure pulses in the magnetosheath, inward bow shock motion, and magnetopause compression. Statistical surveys indicate that the magnetosheath magnetic field orientation rarely remains constant during periods of magnetopause and bow shock motion (both characterized by periods of 1 to 10 min). There is no tendency for bow shock motion to occur for southward interplanetary magnetic field (IMF) orientations.

  3. Nonlinear electron magnetohydrodynamics physics. I. Whistler spheromaks, mirrors, and field reversed configurations

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.; Strohmaier, K. D.

    2008-04-15

    The nonlinear interactions of time-varying magnetic fields with plasmas is investigated in the regime of electron magnetohydrodynamics. Simple magnetic field geometries are excited in a large laboratory plasma with a loop antenna driven with large oscillatory currents. When the axial loop field opposes the ambient field, the net field can be reversed to create a field-reversed configuration (FRC). In the opposite polarity, a strong field enhancement is produced. The time-varying antenna field excites whistler modes with wave magnetic fields exceeding the ambient magnetic field. The resulting magnetic field topologies have been measured. As the magnetic topology is changed from FRC to strong enhancement, two propagating field configurations resembling spheromaks are excited, one with positive and the other with negative helicity. Such 'whistler spheromaks' propagate with their null points along the weaker ambient magnetic field, with the current density localized around its O-line. In contrast, 'whistler mirrors' which have topologies similar to linear whistlers, except with B{sub wave}>B{sub 0}, have no null regions and, therefore, broad current layers. This paper describes the basic field topologies of whistler spheromaks and mirrors, while companion papers discuss the associated nonlinear phenomena as well as the interaction between them.

  4. Solar Wind Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Smith, E. J.

    1995-01-01

    The magnetic fields originate as coronal fields that are converted into space by the supersonic, infinitely conducting, solar wind. On average, the sun's rotation causes the field to wind up and form an Archimedes Spiral. However, the field direction changes almost continuously on a variety of scales and the irregular nature of these changes is often interpreted as evidence that the solar wind flow is turbulent.

  5. Soliton configurations of interacting massless fields

    SciTech Connect

    Alekseev, G.A.

    1983-02-01

    The methods of the inverse scattering problem, has been applied to the Einstein equations for vacuum gravitational fields which depend on only two coordinates, and were extended to a system of interacting gravitational and electromagnetic fields without sources. In the present article we describe a further generalization of these methods to the case of the presence in space not only of gravitational and electromagnetic fields but also of a classical ''neutrino'' field, i.e., a massless two-component spinor field (Weyl field), which depends, like the other fields, only on two coordinates. (AIP)

  6. Rotational stability of a long field-reversed configuration

    SciTech Connect

    Barnes, D. C. Steinhauer, L. C.

    2014-02-15

    Rotationally driven modes of long systems with dominantly axial magnetic field are considered. We apply the incompressible model and order axial wavenumber small. A recently developed gyro-viscous model is incorporated. A one-dimensional equilibrium is assumed, but radial profiles are arbitrary. The dominant toroidal (azimuthal) mode numbers ?=1 and ?=2 modes are examined for a variety of non-reversed (B) and reversed profiles. Previous results for both systems with rigid rotor equilibria are reproduced. New results are obtained by incorporation of finite axial wavenumber and by relaxing the assumption of rigid electron and ion rotation. It is shown that the frequently troublesome ?=2 field reversed configuration (FRC) mode is not strongly affected by ion kinetic effects (in contrast to non-reversed cases) and is likely stabilized experimentally only by finite length effects. It is also shown that the ?=1 wobble mode has a complicated behavior and is affected by a variety of configuration and profile effects. The rotationally driven ?=1 wobble is completely stabilized by strong rotational shear, which is anticipated to be active in high performance FRC experiments. Thus, observed wobble modes in these systems are likely not driven by rotation alone.

  7. Field errors in superconducting magnets

    SciTech Connect

    Barton, M.Q.

    1982-01-01

    The mission of this workshop is a discussion of the techniques for tracking particles through arbitrary accelerator field configurations to look for dynamical effects that are suggested by various theoretical models but are not amenable to detailed analysis. A major motivation for this type of study is that many of our accelerator projects are based on the use of superconducting magnets which have field imperfections that are larger and of a more complex nature than those of conventional magnets. Questions such as resonances, uncorrectable closed orbit effects, coupling between planes, and diffusion mechanisms all assume new importance. Since, simultaneously, we are trying to do sophisticated beam manipulations such as stacking, high current accelerator, long life storage, and low loss extraction, we clearly need efficient and accurate tracking programs to proceed with confidence.

  8. Magnetic Field Measurement System

    SciTech Connect

    Kulesza, Joe; Johnson, Eric; Lyndaker, Aaron; Deyhim, Alex; Waterman, Dave; Blomqvist, K. Ingvar; Dunn, Jonathan Hunter

    2007-01-19

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

  9. A novel approach to magnetic divertor configuration design

    NASA Astrophysics Data System (ADS)

    Blommaert, M.; Baelmans, M.; Dekeyser, W.; Gauger, N. R.; Reiter, D.

    2015-08-01

    Divertor exhaust system design and analysis tools are crucial to evolve from experimental fusion reactors towards commercial power plants. In addition to material research and dedicated vessel geometry design, improved magnetic configurations can contribute to sustaining the diverted heat loads. Yet, computational design of the magnetic divertor is a challenging process involving a magnetic equilibrium solver, a plasma edge grid generator and a computationally demanding plasma edge simulation. In this paper, an integrated approach to efficient sensitivity calculations is discussed and applied to a set of slightly reduced divertor models. Sensitivities of target heat load performance to the shaping coil currents are directly evaluated. Using adjoint methods, the cost for a sensitivity evaluation is reduced to about two times the simulation cost of one specific configuration. Further, the use of these sensitivities in an optimal design framework is illustrated by a case with realistic Joint European Torus (JET) configurational parameters.

  10. Magnetic Field Solver

    NASA Technical Reports Server (NTRS)

    Ilin, Andrew V.

    2006-01-01

    The Magnetic Field Solver computer program calculates the magnetic field generated by a group of collinear, cylindrical axisymmetric electromagnet coils. Given the current flowing in, and the number of turns, axial position, and axial and radial dimensions of each coil, the program calculates matrix coefficients for a finite-difference system of equations that approximates a two-dimensional partial differential equation for the magnetic potential contributed by the coil. The program iteratively solves these finite-difference equations by use of the modified incomplete Cholesky preconditioned-conjugate-gradient method. The total magnetic potential as a function of axial (z) and radial (r) position is then calculated as a sum of the magnetic potentials of the individual coils, using a high-accuracy interpolation scheme. Then the r and z components of the magnetic field as functions of r and z are calculated from the total magnetic potential by use of a high-accuracy finite-difference scheme. Notably, for the finite-difference calculations, the program generates nonuniform two-dimensional computational meshes from nonuniform one-dimensional meshes. Each mesh is generated in such a way as to minimize the numerical error for a benchmark one-dimensional magnetostatic problem.

  11. Magnetic fields at uranus.

    PubMed

    Ness, N F; Acua, M H; Behannon, K W; Burlaga, L F; Connerney, J E; Lepping, R P; Neubauer, F M

    1986-07-01

    The magnetic field experiment on the Voyager 2 spacecraft revealed a strong planetary magnetic field of Uranus and an associated magnetosphere and fully developed bipolar masnetic tail. The detached bow shock wave in the solar wind supersonic flow was observed upstream at 23.7 Uranus radii (1 R(U) = 25,600 km) and the magnetopause boundary at 18.0 R(U), near the planet-sun line. A miaximum magnetic field of 413 nanotesla was observed at 4.19 R(U ), just before closest approach. Initial analyses reveal that the planetary magnetic field is well represented by that of a dipole offset from the center of the planet by 0.3 R(U). The angle between Uranus' angular momentum vector and the dipole moment vector has the surprisingly large value of 60 degrees. Thus, in an astrophysical context, the field of Uranus may be described as that of an oblique rotator. The dipole moment of 0.23 gauss R(3)(U), combined with the large spatial offset, leads to minimum and maximum magnetic fields on the surface of the planet of approximately 0.1 and 1.1 gauss, respectively. The rotation period of the magnetic field and hence that of the interior of the planet is estimated to be 17.29+/- 0.10 hours; the magnetotail rotates about the planet-sun line with the same period. Thelarge offset and tilt lead to auroral zones far from the planetary rotation axis poles. The rings and the moons are embedded deep within the magnetosphere, and, because of the large dipole tilt, they will have a profound and diurnally varying influence as absorbers of the trapped radiation belt particles. PMID:17812894

  12. Configuration and temperature dependence of magnetic damping in spin valves

    SciTech Connect

    Joyeux, X.; Devolder, T.; Kim, Joo-Von; Gomez de la Torre, Y.; Eimer, S.; Chappert, C.

    2011-09-15

    Using vector-analyzer ferromagnetic resonance, we have studied the microwave susceptibility of a Py/Co/Cu/Co/MnIr spin valve over a large temperature range (5-450 K) and as a function of the magnetic configuration. An effective magnetization and Gilbert damping constant of 1.1 T and 0.021, respectively, are found for the permalloy free layer, with no discernible variation in temperature observed for either quantities. In contrast, the pinned layer magnetization is reduced by heating, and the exchange bias collapses near a temperature of 450 K. The ferromagnetic resonance linewidth of the free layer increases by 500 MHz when the layer magnetizations are aligned in antiparallel, which is attributed to a configuration-dependent contribution to the damping from spin pumping effects.

  13. Mercury's Magnetic Field

    NASA Astrophysics Data System (ADS)

    Johnson, C. L.

    2014-12-01

    Mercury is the only inner solar system body other than Earth to possess an active core dynamo-driven magnetic field and the only planet with a small, highly dynamic magnetosphere. Measurements made by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have provided a wealth of data on Mercury's magnetic field environment. Mercury's weak magnetic field was discovered 40 years ago by the Mariner 10 spacecraft, but its large-scale geometry, strength and origin could not be definitively established. MESSENGER data have shown that the field is dynamo-generated and can be described as an offset axisymmetric dipole field (hereafter OAD): the magnetic equator lies ~0.2 RM (RM = 2440 km) north of the geographic equator and the dipole moment is 2.8 x1019 Am2 (~0.03% that of Earth's). The weak internal field and the high, but variable, solar wind ram pressure drive vigorous magnetospheric dynamics and result in an average distance from the planet center to the sub-solar magnetopause of only 1.42 RM. Magnetospheric models developed with MESSENGER data have allowed re-analysis of the Mariner 10 observations, establishing that there has been no measureable secular variation in the internal field over 40 years. Together with spatial power spectra for the OAD, this provides critical constraints for viable dynamo models. Time-varying magnetopause fields induce secondary core fields, the magnitudes of which confirm the core radius estimated from MESSENGER gravity and Earth-based radar data. After accounting for large-scale magnetospheric fields, residual signatures are dominated by additional external fields that are organized in the local time frame and that vary with magnetospheric activity. Birkeland currents have been identified, which likely close in the planetary interior at depths below the base of the crust. Near-periapsis magnetic field measurements at altitudes greater than 200 km have tantalizing hints of crustal fields, but crustal sources cannot be distinguished from core fields, nor cleanly separated from external fields. I will report on recent data acquired at altitudes as low as 25 km that have the potential to resolve these issues. The presence of remanent crustal fields would have profound implications for Mercury's thermal and dynamical histories.

  14. Magnetic fields of spherical compact stars in a braneworld

    SciTech Connect

    Ahmedov, B. J.; Fattoyev, F. J.

    2008-08-15

    We study the stellar magnetic field configuration in dependence on brane tension and present solutions of Maxwell equations in the external background space-time of a magnetized spherical star in a Randall-Sundrum II type braneworld. The star is modeled as a sphere consisting of perfect highly magnetized fluid with infinite conductivity and a frozen-in magnetic field. With respect to solutions for magnetic fields found in the Schwarzschild space-time, brane tension introduces enhancing corrections to the exterior magnetic field which could be relevant for the magnetic fields of magnetized compact objects as pulsars and magnetars and may provide observational evidence for the brane tension.

  15. Magnetic Fields in Galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    The origin and evolution of cosmic magnetic fields, their strength and structure in intergalactic space, their first occurrence in young galaxies, and their dynamical importance for galaxy evolution remain widely unknown. Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized radio synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 μG) and in central starburst regions (50-100 μG). Such fields are dynamically important; they can affect gas flows and drive gas inflows in central regions. Polarized radio emission traces ordered fields which can be regular or anisotropic turbulent, generated from isotropic turbulent fields by compression or shear. The strongest ordered fields of 10-15 μG strength are generally found in interarm regions and follow the orientation of adjacent gas spiral arms. In galaxies with strong density waves, ordered (anisotropic turbulent) fields are also observed at the inner edges of the spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions of starburst galaxies. Ordered fields in interacting galaxies have asymmetric distributions and are an excellent tracer of past interactions between galaxies or with the intergalactic medium. Irregular galaxies host isotropic turbulent fields often of similar strength as in spiral galaxies, but only weak ordered fields. Faraday rotation measures (RM) of the diffuse polarized radio emission from the disks of several galaxies reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by a mean-field α -Ω dynamo. So far no indications were found in external galaxies of large-scale field reversals, like the one in the Milky Way. Ordered magnetic fields are also observed in radio halos around edge-on galaxies out to large distances from the plane, with X-shaped patterns. In the outflow cone above a starburst region of NGC 253, RM data indicate a helical magnetic field.

  16. Strangeness spin, magnetic moment, and strangeness configurations of the proton

    SciTech Connect

    An, C.S.; Riska, D.O.; Zou, B.S.

    2006-03-15

    The implications of the empirical signatures for the positivity of the strangeness magnetic moment {mu}{sub s} and the negativity of the strangeness contribution to the proton spin {delta}{sub s} on the possible uudss configurations of five quarks in the proton are analyzed. The empirical signs for the values for these two observables can only be obtained in configurations where the uuds subsystem is orbitally excited and the s antiquark is in the ground state. The configurations in which the s is orbitally excited, including the conventional K{sup +}{lambda}{sup 0} configuration, with the exception of that in which the uuds component has spin 2, yield negative values for {mu}{sub s}. Here, the strangeness spin {delta}{sub s}, strangeness magnetic moment {mu}{sub s}, and axial coupling constant G{sub A}{sup s} are calculated for all possible configurations of the uudss component of the proton. In the configuration with [4]{sub FS}[22]{sub F}[22]{sub S} flavor-spin symmetry, which is likely to have the lowest energy, {mu}{sub s} is positive and {delta}{sub s}{approx_equal}G{sub A}{sup s}{approx_equal}-1/3{mu}{sub s}.

  17. Suprathermal plasma flows in current sheets formed in two- and three-dimensional magnetic configurations

    SciTech Connect

    Kyrie, N. P.; Markov, V. S.; Frank, A. G.

    2010-04-15

    Dynamics of the thermal and directed motions of argon plasma ions in current sheets formed in various magnetic configurations was investigated experimentally Measurements in three-dimensional magnetic configurations with an X line were carried out for the first time. The results of these measurements were compared with the data obtained in experiments with two-dimensional magnetic configurations. The ion temperature and the energies and velocities of directed plasma flows within the current sheet were determined by analyzing the shapes of argon ion spectral lines broadened due to the Doppler effect. It is found that, under the given experimental conditions, the axial magnetic field does not affect the ion temperature and plasma acceleration in the sheet.

  18. Hydromagnetic Stability of a Driven, Dissipative Annular Field Reversed Configuration

    NASA Astrophysics Data System (ADS)

    Pierce, Wilbur Franklin, IV

    The Coaxial Slow Source (CSS) is a device which was designed as a means of forming Annular Field Reversed Configurations for magnetic fusion on relatively slow (50 -100 mus) time scales. Such configurations are predicted to be ideally unstable to magnetohydrodynamic tilting modes in which one half of torus shifts in the positive axial direction and the other half in the negative direction. These instabilities have been observed to grow and saturate at finite amplitude in the CSS as formation progresses. Apparently stable operating regimes of fill pressure/loop voltage space have also been found. The relatively cold temperature (~2 eV) of the plasma gives rise to a high classical resistivity, placing the Lundquist number (ratio of resistive to Alfven time scales) between 0.5 and 10.0. It is proposed that resistivity, along with other dissipation mechanisms such as viscosity and ion-neutral friction, are responsible for the observed stability. Experiments were performed which explore these stability issues. A nonlinear, dynamical systems stability model, which accounts for the effects of inductive current drive and dissipation, was also developed and shows some agreement with the experimental results. The findings of this study are significant for two reasons: (1) It is one of the few clear observations of tilting modes in an FRC-like geometry and (2) It provides an experimental study of ideally unstable modes in a configuration which is not driven sufficiently hard to take it out of the low Lundquist number regime, making a quantitative measurement of the level of dissipation necessary to suppress the ideal tilt mode.

  19. Electronic configurations and magnetic anisotropy in organometallic metallocenes

    NASA Astrophysics Data System (ADS)

    Nawa, Kenji; Kitaoka, Yukie; Nakamura, Kohji; Akiyama, Toru; Ito, Tomonori

    2015-05-01

    Electronic configurations and magnetic anisotropy of organometallic metallocenes (MCp2s) were investigated by means of first principles calculations based on the constraint density functional theory. The results predict that the ground states for M = Cr, Mn, Fe, Co, and Ni are the 3E2 g, 2E2 g, 1A1 g, 2E1 g, and 3A2 g states, respectively. The magnetizations of the CoCp2 and NiCp2 energetically favor highly orienting along the perpendicular and parallel directions to the cyclopentadienyl (Cp) plane, respectively, and the others show almost no preference for the magnetic easy axis.

  20. Planetary magnetic fields

    NASA Technical Reports Server (NTRS)

    Stevenson, D. J.

    1983-01-01

    Observations of planetary magnetic fields are synthesized with current knowledge of the composition and evolution of planets and the sources of planetary magnetism. The observations for earth, Jupiter, Saturn, Mercury, Venus, the moon, Mars, and small bodies and meteorites are summarized. The evolution and structure of the terrestrial planets, of Jupiter and Saturn, and of Uranus and Neptune are discussed in detail. Possible sources of planetary magnetism are discussed, and estimates are established which are sufficient in most cases to identify whether an observed field is likely to be the consequence of dynamo generation. Predictions of the existence or nonexistence of dynamos are offered for each large planet or satellite in the solar system.

  1. Multichord optical interferometry of FRX-L's field reversed configuration

    SciTech Connect

    Ruden, E. L.; Zhang, Shouyin; Wurden, G. A.; Intrator, T. P.; Renneke, R.; Waganaar, W. J.; Analla, F. T.; Grabowski, T. C.

    2006-10-15

    A 0.633 {mu}m laser interferometer provides detailed time resolved information about the spatial distribution of the plasma density of field reversed configurations (FRC's) produced by the FRX-L experiment at Los Alamos National Laboratory. This experiment is an effort to produce a magnetized plasma with closed field lines suitable for compression by a solid metal liner imploded by the Shiva Star capacitor bank at the Air Force Research Laboratory. The interferometer probes a fanned array of eight chords through the FRC midplane, measuring the line integrated free electron density via its effect on optical phase shift relative to eight reference beams as a function of time. The reference beams are given nominally identical optical paths, except that they are folded for compactness and given an 80 MHz higher optical frequency by use of a Bragg cell beam splitter. After the beams are recombined, interference results in 80 MHz electromagnetic beat waves with dynamic phase shifts equal to those of the corresponding optical probes. Quadrature mixing of the electronically monitored light is then performed with rf components. Noteworthy features of the interferometer's design are the unique compact folding scheme of the reference paths, inclusion of a fused quartz tube in the reference path similar to that of the FRC's vacuum vessel to compensate for cylindrical lensing, and transmission of the interfering light via optical fibers to a rf shielded room for processing. Extraneous contributions to the phase shift due to vibration resulting from the system's pulsed magnetic field, and dynamic refractive changes in or near the fused quartz tube wall (possibly due to radiation heating) are corrected for.

  2. Multichord optical interferometry of FRX-L's field reversed configuration

    NASA Astrophysics Data System (ADS)

    Ruden, E. L.; Zhang, Shouyin; Wurden, G. A.; Intrator, T. P.; Renneke, R.; Waganaar, W. J.; Analla, F. T.; Grabowski, T. C.

    2006-10-01

    A 0.633μm laser interferometer provides detailed time resolved information about the spatial distribution of the plasma density of field reversed configurations (FRC's) produced by the FRX-L experiment at Los Alamos National Laboratory. This experiment is an effort to produce a magnetized plasma with closed field lines suitable for compression by a solid metal liner imploded by the Shiva Star capacitor bank at the Air Force Research Laboratory. The interferometer probes a fanned array of eight chords through the FRC midplane, measuring the line integrated free electron density via its effect on optical phase shift relative to eight reference beams as a function of time. The reference beams are given nominally identical optical paths, except that they are folded for compactness and given an 80MHz higher optical frequency by use of a Bragg cell beam splitter. After the beams are recombined, interference results in 80MHz electromagnetic beat waves with dynamic phase shifts equal to those of the corresponding optical probes. Quadrature mixing of the electronically monitored light is then performed with rf components. Noteworthy features of the interferometer's design are the unique compact folding scheme of the reference paths, inclusion of a fused quartz tube in the reference path similar to that of the FRC's vacuum vessel to compensate for cylindrical lensing, and transmission of the interfering light via optical fibers to a rf shielded room for processing. Extraneous contributions to the phase shift due to vibration resulting from the system's pulsed magnetic field, and dynamic refractive changes in or near the fused quartz tube wall (possibly due to radiation heating) are corrected for.

  3. MHD simulations of magnetic reconnection in a skewed three-dimensional tail configuration

    NASA Technical Reports Server (NTRS)

    Birn, J.; Hesse, M.

    1991-01-01

    The dynamic evolution of a nonsymmetric magnetotail configuration initiated by the sudden occurrence of (anomalous) resistivity are examined using a three-dimensional resistive MHD simulation developed by Birn (1990) that includes a net cross-tail field and thus breaks the mirror symmetry around the neutral sheet. Results show that the field evolution is similar to that of a symmetric configuration studied by Birn and Hones (1981), pointing to the formation and ejection of a plasmoid. On the other hand, the topological structure of the magnetic field, defined by the field line connections, was remarkably different from the symmetric case. The plasmoid in this case became 'open', connected initially with the earth but gradually becoming connected with the interplanetary field. The openness of the plasmoid and its magnetic connection with interplanetary field lines suggest the possibility of a heat flux out of the plasmoid on interconnected flux tubes.

  4. Formation of Field-Reversed-Configuration Plasma with Punctuated-Betatron-Orbit Electrons

    SciTech Connect

    Welch, D. R.; Genoni, T. C.; Cohen, S. A.; Glasser, A. H.

    2010-07-02

    We describe ab initio, self-consistent, 3D, fully electromagnetic numerical simulations of current drive and field-reversed-configuration plasma formation by odd-parity rotating magnetic fields (RMF{sub o}). Magnetic-separatrix formation and field reversal are attained from an initial mirror configuration. A population of punctuated-betatron-orbit electrons, generated by the RMF{sub o}, carries the majority of the field-normal azimuthal electrical current responsible for field reversal. Appreciable current and plasma pressure exist outside the magnetic separatrix whose shape is modulated by the RMF{sub o} phase. The predicted plasma density and electron energy distribution compare favorably with RMF{sub o} experiments.

  5. MHD waves and instabilities for gravitating, magnetized configurations in motion

    NASA Astrophysics Data System (ADS)

    Keppens, Rony; Goedbloed, Hans J. P.

    Seismic probing of equilibrium configurations is of course well-known from geophysics, but has also been succesfully used to determine the internal structure of the Sun to an amazing accuracy. The results of helioseismology are quite impressive, although they only exploit an equilibrium structure where inward gravity is balanced by a pressure gradient in a 1D radial fashion. In principle, one can do the same for stationary, gravitating, magnetized plasma equilibria, as needed to perform MHD seismology in astrophysical jets or accretion disks. The introduction of (sheared) differential rotation does require the important switch from diagnosing static to stationary equilibrium configurations. The theory to describe all linear waves and instabilities in ideal MHD, given an exact stationary, gravitating, magnetized plasma equilibrium, in any dimensionality (1D, 2D, 3D) has been known since 1960, and is governed by the Frieman-Rotenberg equation. The full (mathematical) power of spectral theory governing physical eigenmode determination comes into play when using the Frieman-Rotenberg equation for moving equilibria, as applicable to astrophysical jets, accretion disks, but also solar flux ropes with stationary flow patterns. I will review exemplary seismic studies of flowing equilibrium configurations, covering solar to astrophysical configurations in motion. In that case, even essentially 1D configurations require quantification of the spectral web of eigenmodes, organizing the complex eigenfrequency plane.

  6. Classical field configurations and infrared slavery

    NASA Astrophysics Data System (ADS)

    Swanson, Mark S.

    1987-09-01

    The problem of determining the energy of two spinor particles interacting through massless-particle exchange is analyzed using the path-integral method. A form for the long-range interaction energy is obtained by analyzing an abridged vertex derived from the parent theory. This abridged vertex describes the radiation of zero-momentum particles by pointlike sources. A path-integral formalism for calculating the energy of the radiation field associated with this abridged vertex is developed and applications are made to determine the energy necessary for adiabatic separation of two sources in quantum electrodynamics and for an SU(2) Yang-Mills theory. The latter theory is shown to be consistent with confinement via infrared slavery.

  7. Field-reversed configuration (FRC) experiments

    NASA Astrophysics Data System (ADS)

    Siemon, R. E.; Chrien, R. E.; Hugrass, W. N.; Okada, S.; Rej, D. J.; Taggart, D. P.; Tuszewski, M.; Webster, R. B.; Wright, B. L.; Slough, J. T.

    FRCs with equilibrium separatrix radii up to 0.18 m have been formed and studied in FRX-C/LSM. For best formation conditions at low fill pressure, the particle confinement exceeds the predictions of LHD transport calculations by up to a factor of two; however, the inferred flux confinement is more anomalous than in smaller FRCs. Higher bias field produces axial shocks and degradation in confinement, while higher fill pressure results in gross fluting during formation. FRCs have been formed in TRX with s from 2 to 6. These relatively collisional FRCs exhibit flux lifetimes of 10 yields 20 kinetic growth times for the internal tilt mode. The coaxial slow source has produced annular FRCs in a coaxial coil geometry on slow time scales using low voltages.

  8. Hidden magnetic configuration in epitaxial La1-rSrzMnO3 films

    SciTech Connect

    Kao, Chi-Chang

    2011-05-23

    We present an unreported magnetic configuration in epitaxial La{sub 1-x}Sr{sub x}MnO{sub 3} (x {approx} 0.3) (LSMO) films grown on strontium titanate (STO). X-ray magnetic circular dichroism indicates that the remanent magnetic state of thick LSMO films is opposite to the direction of applied magnetic field. Spectroscopic and scattering measurements reveal that the average Mn valence varies from mixed Mn{sup 3+}/Mn{sup 4+} to an enriched Mn{sup 3+} region near the STO interface, resulting in a compressive lattice along a, b-axis and a possible electronic reconstruction in the Mn e{sub g} orbital (d{sub 3z{sup 2}-r{sup 2}}). This reconstruction may provide a mechanism for coupling the Mn{sup 3+} moments antiferromagnetically along the surface normal direction, and in turn may lead to the observed reversed magnetic configuration.

  9. Hidden Magnetic Configuration in Epitaxial La1-x SrxMnO3 Films

    SciTech Connect

    Lee, J.S.; Arena, D.A.; Yu, P.; Nelson, C.S.; Fan, R.; Kinane, C.J.; Langridge, S.; Rossell, M.D.; Ramesh, R.; Kao, C.C.

    2010-12-17

    We present an unreported magnetic configuration in epitaxial La{sub 1-x}Sr{sub x}MnO{sub 3} (x {approx} 0.3) (LSMO) films grown on strontium titanate (STO). X-ray magnetic circular dichroism indicates that the remanent magnetic state of thick LSMO films is opposite to the direction of the applied magnetic field. Spectroscopic and scattering measurements reveal that the average Mn valence varies from mixed Mn{sup 3+}/Mn{sup 4+} to an enriched Mn{sup 3+} region near the STO interface, resulting in a compressive lattice along the a, b axis and a possible electronic reconstruction in the Mn e{sub g} orbital (d{sub 3z{sup 2}-r{sup 2}}). This reconstruction may provide a mechanism for coupling the Mn{sup 3+} moments antiferromagnetically along the surface normal direction, and in turn may lead to the observed reversed magnetic configuration.

  10. Nonlinear stability of field-reversed configurations with self-generated toroidal field

    SciTech Connect

    Omelchenko, Y. A.; Schaffer, M. J.; Parks, P. B.

    2001-10-01

    The field-reversed configuration (FRC) is a high-beta compact toroidal plasma confinement scheme in which the external poloidal field is reversed on the geometric axis by azimuthal (toroidal) plasma current. A quasineutral, hybrid, particle-in-cell (PIC) approach [Y. A. Omelchenko and R. N. Sudan, Phys. Plasmas 2, 2773 (1995)] is applied to study long-term nonlinear stability of computational FRC equilibria to a number of toroidal modes, including the most disruptive tilt mode. In particular, a self-generated toroidal magnetic field is found to be an important factor in mitigating the instability and preventing the confinement disruption. This is shown to be a unique FRC property resulting from the Hall effect in the regions of vanishing poloidal magnetic field. The instability-driven toroidal field stabilizes kink formation by increasing the magnetic field energy without destabilizing curvature-driven plasma motion. Finally, the tilt instability saturates due to nonlinear, finite Larmor radius (FLR) effects and plasma relaxation to a quasisteady kinetic state. During this transition the FRC is shown to dissipate a substantial amount of initially trapped flux and plasma energy. These effects are demonstrated for kinetic and fluid-like, spherical and prolate FRCs.

  11. Magnetic Signatures on Planets Without Magnetic Fields

    NASA Astrophysics Data System (ADS)

    McEnroe, S. A.; Dyar, M. D.; Brown, L. B.

    2002-03-01

    On extraterrestrial bodies with no present day magnetic fields, the majority of the magnetic signature must come from high coercivity phases such as hemo-ilmenite, ilmenohematite, or very fine-grained magnetite.

  12. Time Window for Magnetic Reconnection in Plasma Configurations with Velocity Shear

    SciTech Connect

    Faganello, M.; Califano, F.; Pegoraro, F.

    2008-10-24

    It is shown that the rate of magnetic field line reconnection can be clocked by the evolution of the large-scale processes that are responsible for the formation of the current layers where reconnection can take place. In unsteady plasma configurations, such as those produced by the onset of the Kelvin-Helmholtz instability in a plasma with a velocity shear, qualitatively different magnetic structures are produced depending on how fast the reconnection process develops on the external clock set by the evolving large-scale configuration.

  13. Crustal Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick T.; Ravat, D.; Frawley, James J.

    1999-01-01

    Cosmos 49, Polar Orbit Geophysical Observatory (POGO) (Orbiting Geophysical Observatory (OGO-2, 4 and 6)) and Magsat have been the only low-earth orbiting satellites to measure the crustal magnetic field on a global scale. These missions revealed the presence of long- wavelength (> 500 km) crustal anomalies predominantly located over continents. Ground based methods were, for the most part, unable to record these very large-scale features; no doubt due to the problems of assembling continental scale maps from numerous smaller surveys acquired over many years. Questions arose as to the source and nature of these long-wave length anomalies. As a result there was a great stimulant given to the study of the magnetic properties of the lower crust and upper mantle. Some indication as to the nature of these deep sources has been provided by the recent results from the deep crustal drilling programs. In addition, the mechanism of magnetization, induced or remanent, was largely unknown. For computational ease these anomalies were considered to result solely from induced magnetization. However, recent results from Mars Orbiter Laser Altimeter (MOLA), a magnetometer-bearing mission to Mars, have revealed crustal anomalies with dimensions similar to the largest anomalies on Earth. These Martian features could only have been produced by remanent magnetization, since Mars lacks an inducing field. The origin of long-wavelength crustal anomalies, however, has not been completely determined. Several large crustal magnetic anomalies (e.g., Bangui, Kursk, Kiruna and Central Europe) will be discussed and the role of future satellite magnetometer missions (Orsted, SUNSAT and Champ) in their interpretation evaluated.

  14. Refocusing properties of periodic magnetic fields

    NASA Technical Reports Server (NTRS)

    Stankiewicz, N.

    1976-01-01

    The use of depressed collectors for the efficient collection of spent beams from linear-beam microwave tubes depends on a refocusing procedure in which the space charge forces and transverse velocity components are reduced. The refocusing properties are evaluated of permanent magnet configurations whose axial fields are approximated by constant plateaus or linearly varying fields. The results provide design criteria and show that the refocusing properties can be determined from the plateau fields alone.

  15. Preliminary investigation of force-reduced superconducting magnet configurations for advanced technology applications

    SciTech Connect

    Bouillard, J.X.

    1992-12-01

    The feasibility of new high-field low specific weight superconducting magnet designs using force-free fields is being explored analytically and numerically. This report attempts to assess the technical viability of force-free field concepts to produce high-field, low specific weight and large bore volume magnets, which could promote the use of high temperature superconductors. Several force-free/force-reduced magnet configurations are first reviewed, then discussed and assessed. Force-free magnetic fields, fields for which the current flows parallel to the field, have well-known mathematical solutions extending upon infinite domains. These solutions, however, are no longer force-free everywhere for finite geometries. In this preliminary study, force-free solutions such as the Lundquist solutions truncated to a size where the internal field of the coil matches an externally cylindrical magnetic field (also called a Lundquist coil) are numerically modeled and explored. Significant force-reduction for such coils was calculated, which may have some importance for the design of lighter toroidal magnets used in thermonuclear fusion power generation, superconducting magnetic energy storage (SMES), and mobile MHD power generation and propulsion.

  16. Explaining Mercury's peculiar magnetic field

    NASA Astrophysics Data System (ADS)

    Wicht, Johannes; Cao, Hao; Heyner, Daniel; Dietrich, Wieland; Christensen, Ulrich R.

    2014-05-01

    MESSENGER magnetometer data revealed that Mercury's magnetic field is not only particularly weak but also has a peculiar geometry. The MESSENGER team finds that the location of the magnetic equator always lies significantly north of the geographic equator, is largely independent of the distance to the planet, and also varies only weakly with longitude. The field is best described by an axial dipole that is offset to the north by about 20% of the planetary radius. In terms of classical Gauss coefficients, this translates into a low axial dipole component of g10= -190 nT but a relatively large axial quadrupole contribution that amounts to roughly 40% of this value. The axial octupole is also sizable while higher harmonic contributions are much weaker. Very remarkable is also the fact that the equatorial dipole contribution is very small, consistent with a dipole tilt below 0.8 degree, and this is also true for the other non-axisymmetic field contributions. We analyze several numerical dynamos concerning their capability of explaining Mercury's magnetic field. Classical schemes geared to model the geomagnetic field typically show a much weaker quadrupole component and thus a smaller offset. The onset only becomes larger when the dynamo operates in the multipolar regime at higher Rayleigh numbers. However, since the more complex dynamics generally promotes all higher multipole contributions the location of the magnetic equator varies strongly with longitude and distance to the planet. The situation improves when introducing a stably stratified outer layer in the dynamo region, representing either a rigid FeS layer or a sub-adiabatic core-mantle boundary heat flux. This layer filters out the higher harmonic contributions and the field not only becomes sufficiently weak but also assumes a Mercury like offset geometry during a few percent of the simulation time. To increase the likelihood for the offset configuration, the north-south symmetry must be permanently broken and we explore two scenarios. Increasing the heat flux through the northern hemisphere of the core-mantle boundary is an obvious choice but is not supported by current models for Mercury's mantle. We find that a combination of internal rather than bottom driving and an increased heat flux through the equatorial region of the core-mantle boundary also promotes the required symmetry breaking and results in very Mercury like fields. The reason is that the imposed heat flux pattern, though being equatorially symmetric, lowers the critical Rayleigh number for the onset of equatorially anti-symmetric convection modes. In both scenarios, a stably stratified layer or a feedback coupling to the magnetospheric field is required for lowering the field strength to Mercury-like values.

  17. Normal glow discharge in axial magnetic field

    NASA Astrophysics Data System (ADS)

    Surzhikov, S.; Shang, J.

    2014-10-01

    Theory and results of mathematical modeling of a glow discharge in a parallel-plate configuration with axial magnetic field is presented. The model consists of continuity equations for electron and ion fluids, the Poisson equation for the self-consistent electric field. Numerical simulation results are presented for two-dimensional glow discharge at various initial conditions. The results are obtained for molecular nitrogen at pressure 1-5 Torr, emf of power supply 1-2 kV, and magnetic field induction B = 0-0.5 T. It is shown that in the presence of the axial magnetic field the glow discharge is rotated around its axis of symmetry. Nevertheless it is shown that in the investigated range of discharge parameters in an axial magnetic field the law of the normal current density is retained.

  18. Coronal Magnetic Field Models

    NASA Astrophysics Data System (ADS)

    Wiegelmann, Thomas; Petrie, Gordon J. D.; Riley, Pete

    2015-07-01

    Coronal magnetic field models use photospheric field measurements as boundary condition to model the solar corona. We review in this paper the most common model assumptions, starting from MHD-models, magnetohydrostatics, force-free and finally potential field models. Each model in this list is somewhat less complex than the previous one and makes more restrictive assumptions by neglecting physical effects. The magnetohydrostatic approach neglects time-dependent phenomena and plasma flows, the force-free approach neglects additionally the gradient of the plasma pressure and the gravity force. This leads to the assumption of a vanishing Lorentz force and electric currents are parallel (or anti-parallel) to the magnetic field lines. Finally, the potential field approach neglects also these currents. We outline the main assumptions, benefits and limitations of these models both from a theoretical (how realistic are the models?) and a practical viewpoint (which computer resources to we need?). Finally we address the important problem of noisy and inconsistent photospheric boundary conditions and the possibility of using chromospheric and coronal observations to improve the models.

  19. Dynamics of charged particles in spatially chaotic magnetic fields

    SciTech Connect

    Ram, Abhay K.; Dasgupta, Brahmananda

    2010-12-15

    The spatial topology of magnetic field lines can be chaotic for fields generated by simple current configurations. This is illustrated for a system consisting of a circular current loop and a straight current wire. An asymmetric configuration of the current system leads to three-dimensional spatially chaotic magnetic fields. The motion of charged particles in these fields is not necessarily chaotic and exhibits intriguing dynamical properties. Particles having initial velocities closely aligned with the direction of the local magnetic field are likely to follow chaotic orbits in phase space. Other particles follow coherent and periodic orbits; these orbits being the same as in the symmetric current configuration for which the field lines are not chaotic. An important feature of particles with chaotic motion is that they undergo spatial transport across magnetic field lines. The cross-field diffusion is of interest in a variety of magnetized plasmas including laboratory and astrophysical plasmas.

  20. Chaotic magnetic fields: Particle motion and energization

    SciTech Connect

    Dasgupta, Brahmananda; Ram, Abhay K.; Li, Gang; Li, Xiaocan

    2014-02-11

    Magnetic field line equations correspond to a Hamiltonian dynamical system, so the features of a Hamiltonian systems can easily be adopted for discussing some essential features of magnetic field lines. The integrability of the magnetic field line equations are discussed by various authors and it can be shown that these equations are, in general, not integrable. We demonstrate several examples of realistic chaotic magnetic fields, produced by asymmetric current configurations. Particular examples of chaotic force-free field and non force-free fields are shown. We have studied, for the first time, the motion of a charged particle in chaotic magnetic fields. It is found that the motion of a charged particle in a chaotic magnetic field is not necessarily chaotic. We also showed that charged particles moving in a time-dependent chaotic magnetic field are energized. Such energization processes could play a dominant role in particle energization in several astrophysical environments including solar corona, solar flares and cosmic ray propagation in space.

  1. The Primordial Origin Model of Magnetic Fields in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Sofue, Yoshiaki; Machida, Mami; Kudoh, Takahiro

    2010-10-01

    We propose a primordial-origin model for composite configurations of global magnetic fields in spiral galaxies. We show that a uniform tilted magnetic field wound up into a rotating disk galaxy can evolve into composite magnetic configurations comprising bisymmetric spiral (S = BSS), axisymmetric spiral (A = ASS), plane-reversed spiral (PR), and/or ring (R) fields in the disk, and vertical (V) fields in the center. By MHD simulations we show that these composite galactic fields are indeed created from a weak primordial uniform field, and that different configurations can co-exist in the same galaxy. We show that spiral fields trigger the growth of two-armed gaseous arms. The centrally accumulated vertical fields are twisted and produce a jet toward the halo. We found that the more vertical was the initial uniform field, the stronger was the formed magnetic field in the galactic disk.

  2. Probing Magnetic Configurations in Buried Cobalt/Copper Multilayered Nanowires

    NASA Astrophysics Data System (ADS)

    Liu, Kai

    2009-03-01

    Multilayered magnetic nanowires have been a model system for heterostructured junctions that exhibit a host of fascinating perpendicular spin transport phenomena, such as giant and tunneling magnetoresistance (MR), and spin-transfer torque effects. Due to the extremely small physical dimensions the magnetic components in these nanowires or junctions often exhibit complex magnetization reversal behaviors, which are difficult to probe by magnetic imaging since the entities are buried deep inside a matrix. Conventional hysteresis loop measurement alone cannot reliably distinguish the reversal mechanisms either. In this work we have captured magnetic and MR ``fingerprints'' of Co nanodiscs in Co/Cu multilayered nanowires as they undergo a single domain to vortex state transition, using a first-order reversal curve (FORC) method [1]. The nanowires have been electrochemically deposited into nanoporous polycarbonate membranes. In 50 nm diameter [Co(5nm)/Cu(8nm)]400 nanowires, a 10% MR effect is observed at 300 K. In 200 nm diameter nanowires, the magnetic configurations can be tuned by adjusting the Co nanodisc aspect ratio. Nanowires with thinnest Co exhibit single domain behavior. Those with thicker Co exhibit vortex states, where the irreversible nucleation and annihilation of the vortices are manifested as butterfly-like features in the FORC distributions, similar to those observed in arrays of Fe nanodots [2]. They also show a superposition of giant and anisotropic magnetoresistance, which corresponds to the specific magnetic configurations of the Co nanodiscs. [4pt] [1] J. E. Davies, et al, Phys. Rev. B 70, 224434 (2004); Appl. Phys. Lett. 86, 262503 (2005); Phys. Rev. B 77, 014421 (2008).[0pt] [2] R. K. Dumas, et al, Phys. Rev. B 75, 134405 (2007); Appl. Phys. Lett. 91, 202501 (2007).

  3. THE GALACTIC MAGNETIC FIELD

    SciTech Connect

    Jansson, Ronnie; Farrar, Glennys R.

    2012-12-10

    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.

  4. The Galactic Magnetic Field

    NASA Astrophysics Data System (ADS)

    Jansson, Ronnie; Farrar, Glennys R.

    2012-12-01

    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 ?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.

  5. Global solar magnetic fields

    NASA Astrophysics Data System (ADS)

    Hoeksema, J. T.

    The global solar magnetic field greatly affects the corona, heliosphere, and terrestrial environment as well as revealing much about the Sun itself. It may be useful to think of the global field in two ways: as an aggregate of many small scale processes and as an entity. When considering the origin and evolution of the global field, one immediately focuses on the smaller-scale features and processes that it comprises. These include the emergence of active regions, the interaction of new and existing flux patterns, the distortion and dispersal of flux over the surface by convective motions, the phenomena that produce the emergence of patterns with various periods, and the influence of convection and rotation at various depths on flux tubes. When contemplating the effects of the global field, one often focuses on it as an entity or on its large-scale features. Examples are the reversal of the polar fields, the asymmetry between the north and south hemispheres, the dipole or quadrupole structure of the coronal field and its observation of the Earth as 2 or 4 polarity sectors, and the rigid rotation seen in coronal holes. Both views help us appreciate the significance of the global field.

  6. Superhorizon magnetic fields

    NASA Astrophysics Data System (ADS)

    Campanelli, Leonardo

    2016-03-01

    We analyze the evolution of superhorizon-scale magnetic fields from the end of inflation till today. Whatever is the mechanism responsible for their generation during inflation, we find that a given magnetic mode with wave number k evolves, after inflation, according to the values of k ηe , nk , and Ωk , where ηe is the conformal time at the end of inflation, nk is the number density spectrum of inflation-produced photons, and Ωk is the phase difference between the two Bogoliubov coefficients which characterize the state of that mode at the end of inflation. For any realistic inflationary magnetogenesis scenario, we find that nk-1≪|k ηe|≪1 , and three evolutionary scenarios are possible: (i) |Ωk∓π |=O (1 ) , in which case the evolution of the magnetic spectrum Bk(η ) is adiabatic, a2Bk(η )=const , with a being the expansion parameter; (ii) |Ωk∓π |≪|k ηe| , in which case the evolution is superadiabatic, a2Bk(η )∝η ; (iii) |k ηe|≪|Ωk∓π |≪1 or |k ηe|˜|Ωk∓π |≪1 , in which case an early phase of adiabatic evolution is followed, after a time η⋆˜|Ωk∓π |/k , by a superadiabatic evolution. Once a given mode reenters the horizon, it remains frozen into the plasma and then evolves adiabatically till today. As a corollary of our results, we find that inflation-generated magnetic fields evolve adiabatically on all scales and for all times in conformal-invariant free Maxwell theory, while they evolve superadiabatically after inflation on superhorizon scales in the nonconformal-invariant Ratra model, where the inflaton is kinematically coupled to the electromagnetic field. The latter result supports and, somehow, clarifies our recent claim that the Ratra model can account for the presence of cosmic magnetic fields without suffering from both backreaction and strong-coupling problems.

  7. Low field magnetic resonance imaging

    DOEpatents

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

    2010-07-13

    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.

  8. Two-dimensional interpreter for field-reversed configurations

    SciTech Connect

    Steinhauer, Loren

    2014-08-15

    An interpretive method is developed for extracting details of the fully two-dimensional (2D) “internal” structure of field-reversed configurations (FRC) from common diagnostics. The challenge is that only external and “gross” diagnostics are routinely available in FRC experiments. Inferring such critical quantities as the poloidal flux and the particle inventory has commonly relied on a theoretical construct based on a quasi-one-dimensional approximation. Such inferences sometimes differ markedly from the more accurate, fully 2D reconstructions of equilibria. An interpreter based on a fully 2D reconstruction is needed to enable realistic within-the-shot tracking of evolving equilibrium properties. Presented here is a flexible equilibrium reconstruction with which an extensive data base of equilibria was constructed. An automated interpreter then uses this data base as a look-up table to extract evolving properties. This tool is applied to data from the FRC facility at Tri Alpha Energy. It yields surprising results at several points, such as the inferences that the local β (plasma pressure/external magnetic pressure) of the plasma climbs well above unity and the poloidal flux loss time is somewhat longer than previously thought, both of which arise from full two-dimensionality of FRCs.

  9. Electric and magnetic fields

    NASA Technical Reports Server (NTRS)

    Kaufman, H. R.; Robinson, R. S.; Etters, R. D.

    1982-01-01

    A number of energy momentum anomalies are described that result from the use of Abraham-Lorentz electromagnetic theory. These anomalies have in common the motion of charged bodies or current carrying conductors relative to the observer. The anomalies can be avoided by using the nonflow approach, based on internal energy of the electromagnetic field. The anomalies can also be avoided by using the flow approach, if all contributions to flow work are included. The general objective of this research is a fundamental physical understanding of electric and magnetic fields which, in turn, might promote the development of new concepts in electric space propulsion. The approach taken is to investigate quantum representations of these fields.

  10. Electronic configurations and magnetic anisotropy in organometallic metallocenes

    SciTech Connect

    Nawa, Kenji Kitaoka, Yukie; Nakamura, Kohji; Akiyama, Toru; Ito, Tomonori

    2015-05-07

    Electronic configurations and magnetic anisotropy of organometallic metallocenes (MCp{sub 2}s) were investigated by means of first principles calculations based on the constraint density functional theory. The results predict that the ground states for M = Cr, Mn, Fe, Co, and Ni are the {sup 3}E{sub 2g}, {sup 2}E{sub 2g}, {sup 1}A{sub 1g}, {sup 2}E{sub 1g}, and {sup 3}A{sub 2g} states, respectively. The magnetizations of the CoCp{sub 2} and NiCp{sub 2} energetically favor highly orienting along the perpendicular and parallel directions to the cyclopentadienyl (Cp) plane, respectively, and the others show almost no preference for the magnetic easy axis.

  11. Effect of the Array Distance on the Magnetization Configuration of Submicorn-Sized Ferromagnetic Rings

    NASA Astrophysics Data System (ADS)

    Miyawaki, T.; Toyoda, K.; Kohda, M.; Fujita, A.; Nitta, J.

    2008-10-01

    Magnetization characteristics of one dimensionally arrayed submicron-sized ferromagnetic rings were investigated by MOKE varying inter-ring distance lx. Changing of onion-to-vortex and vortex-to-onion transition fields, HOV and HVO, respectively, due to magnetostatic interaction were found to be proportional to the power of lx. The interaction was found to cause significant change of magnetic configuration and enhance the lx-dependence of HOV and HVO than considering only the decay of magnetostatic energy of uniform-magnetized ring array. Energies of the ring array were also calculated and lx-dependence of HOV and HVO was discussed qualitatively.

  12. Analysis of magnetic systems with high-anisotropy localized magnetic field for terahertz-radiation generation

    NASA Astrophysics Data System (ADS)

    Denisultanov, S. E. Azbite A. Kh; Khodzitsky, M. K.

    2015-11-01

    For enhancement of terahertz radiation generation in terahertz devices four permanent magnetic systems by strong localized magnetic field were considered. Their different configurations were used for simulation and comparative analysis and choice compact system with maximum value of localized magnetic field at the room temperature.

  13. Magnetic nanoparticle motion in external magnetic field

    NASA Astrophysics Data System (ADS)

    Usov, N. A.; Liubimov, B. Ya

    2015-07-01

    A set of equations describing the motion of a free magnetic nanoparticle in an external magnetic field in a vacuum, or in a medium with negligibly small friction forces is postulated. The conservation of the total particle momentum, i.e. the sum of the mechanical and the total spin momentum of the nanoparticle is taken into account explicitly. It is shown that for the motion of a nanoparticle in uniform magnetic field there are three different modes of precession of the unit magnetization vector and the director that is parallel the particle easy anisotropy axis. These modes differ significantly in the precession frequency. For the high-frequency mode the director points approximately along the external magnetic field, whereas the frequency and the characteristic relaxation time of the precession of the unit magnetization vector are close to the corresponding values for conventional ferromagnetic resonance. On the other hand, for the low-frequency modes the unit magnetization vector and the director are nearly parallel and rotate in unison around the external magnetic field. The characteristic relaxation time for the low-frequency modes is remarkably long. This means that in a rare assembly of magnetic nanoparticles there is a possibility of additional resonant absorption of the energy of alternating magnetic field at a frequency that is much smaller compared to conventional ferromagnetic resonance frequency. The scattering of a beam of magnetic nanoparticles in a vacuum in a non-uniform external magnetic field is also considered taking into account the precession of the unit magnetization vector and director.

  14. Electric field induced by dynamical change of dipolar configurations in ferromagnets.

    PubMed

    Prosandeev, S; Bellaiche, L

    2009-03-01

    An analytical expression for the electric field, Eint, induced by any dynamical change of dipolar configuration is derived for ferromagnets. Effective Hamiltonian simulations are further conducted to realistically compute such field in an asymmetric permalloy ring. It is found that Eint mostly consists of short pulses that are correlated with the rapid temporal change of the magnetic toroidal moment in this low-dimensional ferromagnet, thus providing macroscopic information about the dynamical change of magnetic vortices. Discussion about the connection between Eint and some electric fields recently mentioned in the literature is also provided. PMID:19392561

  15. Polar Magnetic Field Experiment

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1999-01-01

    This grant covers the initial data reduction and analysis of the magnetic field measurements of the Polar spacecraft. At this writing data for the first three years of the mission have been processed and deposited in the key parameter database. These data are also available in a variety of time resolutions and coordinate systems via a webserver at UCLA that provides both plots and digital data. The flight software has twice been reprogrammed: once to remove a glitch in the data where there were rare collisions between commands in the central processing unit and once to provide burst mode data at 100 samples per second on a regular basis. The instrument continues to function as described in the instrument paper (1.1 in the bibliography attached below). The early observations were compared with observations on the same field lines at lower altitude. The polar magnetic measurements also proved to be most useful for testing the accuracy of MHD models. WE also made important contributions to study of waves and turbulence.

  16. Photonic Magnetic Field Sensor

    NASA Astrophysics Data System (ADS)

    Wyntjes, Geert

    2002-02-01

    Small, in-line polarization rotators or isolators to reduce feedback in fiber optic links can be the basis for excellent magnetic field sensors. Based on the giant magneto-optical (GMO) or Faraday effect in iron garnets, they with a magnetic field of a few hundred Gauss, (20 mT) for an interaction length for an optical beam of a few millimeters achieve a polarization rotation or phase shift of 45 deg (1/8 cycle). When powered by a small laser diode, with the induced linear phase shift recovered at the shot noise limit, we have demonstrated sensitivities at the 3.3 nT/Hz1/2 level for frequencies from less than 1 Hz to frequencies into the high kHz range. Through further improvements; an increase in interaction length, better materials and by far the greatest factor, the addition of a flux concentrator, sensitivities at the pT/Hz1/2 level appear to be within reach. We will detail such a design and discuss the issues that may limit achieving these goals.

  17. CSEM-steel hybrid wiggler/undulator magnetic field studies

    SciTech Connect

    Halbach, K.; Hoyer, E.; Marks, S.; Plate, D.; Shuman, D.

    1985-05-01

    Current design of permanent magnet wiggler/undulators use either pure charge sheet equivalent material (CSEM) or the CSEM-Steel hybrid configuration. Hybrid configurations offer higher field strength at small gaps, field distributions dominated by the pole surfaces and pole tuning. Nominal performance of the hybrid is generally predicted using a 2-D magnetic design code neglecting transverse geometry. Magnetic measurements are presented showing transverse configuration influence on performance, from a combination of models using CSEMs, REC (H/sub c/ = 9.2 kOe) and NdFe (H/sub c/ = 10.7 kOe), different pole widths and end configurations. Results show peak field improvement using NdFe in place of REC in identical models, gap peak field decrease with pole width decrease (all results less than computed 2-D fields), transverse gap field distributions, and importance of CSEM material overhanging the poles in the transverse direction for highest gap fields.

  18. Magnetic fields in mixed neutron-star-plus-wormhole systems

    NASA Astrophysics Data System (ADS)

    Aringazin, Ascar; Dzhunushaliev, Vladimir; Folomeev, Vladimir; Kleihaus, Burkhard; Kunz, Jutta

    2015-04-01

    We consider mixed configurations consisting of a wormhole filled by a strongly magnetized isotropic or anisotropic neutron fluid. The nontrivial topology of the spacetime is allowed by the presence of exotic matter. By comparing these configurations with ordinary magnetized neutron stars, we clarify the question of how the presence of the nontrivial topology influences the magnetic field distribution inside the fluid. In the case of an anisotropic fluid, we find new solutions describing configurations, where the maximum of the fluid density is shifted from the center. A linear stability analysis shows that these mixed configurations are unstable.

  19. Directed Plasma Flow across Magnetic Field

    NASA Astrophysics Data System (ADS)

    Presura, R.; Stepanenko, Y.; Neff, S.; Sotnikov, V. I.

    2008-04-01

    The Hall effect plays a significant role in the penetration of plasma flows across magnetic field. For example, its effect may become dominant in the solar wind penetration into the magnetosphere, in the magnetic field advection in wire array z-pinch precursors, or in the arcing of magnetically insulated transmission lines. An experiment performed at the Nevada Terawatt Facility explored the penetration of plasma with large Hall parameter (˜10) across ambient magnetic field. The plasma was produced by ablation with the short pulse high intensity laser Leopard (0.35 ps, 10^17W/cm^2) and the magnetic field with the pulsed power generator Zebra (50 T). The expanding plasma assumed a jet configuration and propagated beyond a distance consistent with a diamagnetic bubble model. Without magnetic field, the plasma expansion was close to hemispherical. The ability to produce the plasma and the magnetic field with distinct generators allows a controlled, quasi-continuous variation of the Hall parameter and other plasma parameters making the experiments useful for benchmarking numerical simulations.

  20. Magnetic Fields: Visible and Permanent.

    ERIC Educational Resources Information Center

    Winkeljohn, Dorothy R.; Earl, Robert D.

    1983-01-01

    Children will be able to see the concept of a magnetic field translated into a visible reality using the simple method outlined. Standard shelf paper, magnets, iron filings, and paint in a spray can are used to prepare a permanent and well-detailed picture of the magnetic field. (Author/JN)

  1. Configurational Statistics of Magnetic Bead Detection with Magnetoresistive Sensors

    PubMed Central

    Henriksen, Anders Dahl; Ley, Mikkel Wennemoes Hvitfeld; Flyvbjerg, Henrik; Hansen, Mikkel Fougt

    2015-01-01

    Magnetic biosensors detect magnetic beads that, mediated by a target, have bound to a functionalized area. This area is often larger than the area of the sensor. Both the sign and magnitude of the average magnetic field experienced by the sensor from a magnetic bead depends on the location of the bead relative to the sensor. Consequently, the signal from multiple beads also depends on their locations. Thus, a given coverage of the functionalized area with magnetic beads does not result in a given detector response, except on the average, over many realizations of the same coverage. We present a systematic theoretical analysis of how this location-dependence affects the sensor response. The analysis is done for beads magnetized by a homogeneous in-plane magnetic field. We determine the expected value and standard deviation of the sensor response for a given coverage, as well as the accuracy and precision with which the coverage can be determined from a single sensor measurement. We show that statistical fluctuations between samples may reduce the sensitivity and dynamic range of a sensor significantly when the functionalized area is larger than the sensor area. Hence, the statistics of sampling is essential to sensor design. For illustration, we analyze three important published cases for which statistical fluctuations are dominant, significant, and insignificant, respectively. PMID:26496495

  2. Magnetic field therapy: a review.

    PubMed

    Markov, Marko S

    2007-01-01

    There is increasing interest in using permanent magnets for therapeutic purposes encouraged by basic science publications and clinical reports. Magnetotherapy provides a non invasive, safe, and easy method to directly treat the site of injury, the source of pain and inflammation, and other types of disease. The physiological bases for the use of magnetic fields for tissue repair as well as physical principles of dosimetry and application of various magnetic fields are subjects of this review. Analysis of the magnetic and electromagnetic stimulation is followed by a discussion of the advantage of magnetic field stimulation compared with electric current and electric field stimulation. PMID:17454079

  3. Plasma transport in a simulated magnetic-divertor configuration

    SciTech Connect

    Strawitch, C. M.

    1981-03-01

    The transport properties of plasma on magnetic field lines that intersect a conducting plate are studied experimentally in the Wisconsin internal ring D.C. machine. The magnetic geometry is intended to simulate certain aspects of plasma phenomena that may take place in a tokamak divertor. It is found by a variety of measurements that the cross field transport is non-ambipolar; this may have important implications in heat loading considerations in tokamak divertors. The undesirable effects of nonambipolar flow make it preferable to be able to eliminate it. However, we find that though the non-ambipolarity may be reduced, it is difficult to eliminate entirely. The plasma flow velocity parallel to the magnetic field is found to be near the ion acoustic velocity in all cases. The experimental density and electron temperature profiles are compared to the solutions to a one dimensional transport model that is commonly used in divertor theory.

  4. High magnetic field MHD generator program

    NASA Astrophysics Data System (ADS)

    1980-10-01

    The MHD channel phenomena which are important at high magnetic fields are investigated. Nonuniformity effects, boundary layers, Hall field breakdown, the effects on electrode configuration and current concentrations, and studies of steady state combustion disk and linear channels in an existing 6 Tesla magnet of small dimensions are discussed. In the study of the effects of nonuniformities and instabilities, theoretical models were developed and tested against available data. Boundary layer measurements and calculations of velocity, temperature, and electron density were systematically assessed; by accounting for the effect of free stream turbulence, good agreement is obtained between measurement and theory. An improved laser Doppler anemometer was developed for turbulence damping and velocity profile measurements.

  5. Leptogenesis and primordial magnetic fields

    SciTech Connect

    Long, Andrew J.; Sabancilar, Eray; Vachaspati, Tanmay E-mail: eray.sabancilar@asu.edu

    2014-02-01

    The anomalous conversion of leptons into baryons during leptogenesis is shown to produce a right-handed helical magnetic field; in contrast, the magnetic field produced during electroweak baryogenesis is known to be left-handed. If the cosmological medium is turbulent, the magnetic field evolves to have a present day coherence scale ? 10pc and field strength ? 10{sup ?18}Gauss. This result is insensitive to the energy scale at which leptogenesis took place. Observations of the amplitude, coherence scale, and helicity of the intergalactic magnetic field promise to provide a powerful probe of physics beyond the Standard Model and the very early universe.

  6. Fast superconducting magnetic field switch

    DOEpatents

    Goren, Y.; Mahale, N.K.

    1996-08-06

    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. 6 figs.

  7. Fast superconducting magnetic field switch

    DOEpatents

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

    1996-01-01

    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.

  8. Measuring vector magnetic fields in solar prominences

    NASA Astrophysics Data System (ADS)

    Orozco Surez, D.; Asensio Ramos, A.; Trujillo Bueno, J.

    2013-05-01

    We present spectropolarimetric observations in the He I 1083.0 nm multiplet of a quiescent, hedgerow solar prominence. The data were taken with the Tenerife Infrared Polarimeter attached to the German Vacuum Tower Telescope at the Observatorio del Teide (Tenerife; Canary Islands; Spain). The observed He I circular and linear polarization signals are dominated by the Zeeman effect and by atomic level polarization and the Hanle effect, respectively. These observables are sensitive to the strength and orientation of the magnetic field vector at each spatial point of the field of view. We determine the magnetic field vector of the prominence by applying the HAZEL inversion code to the observed Stokes profiles. We briefly discuss the retrieved magnetic field vector configuration.

  9. Magnetic fields in superconducting neutron stars.

    PubMed

    Lander, S K

    2013-02-15

    The interior of a neutron star is likely to be predominantly a mixture of superfluid neutrons and superconducting protons. This results in the quantization of the star's magnetic field into an array of thin flux tubes, producing a macroscopic force very different from the Lorentz force of normal matter. We show that in an axisymmetric superconducting equilibrium the behavior of a magnetic field is governed by a single differential equation. Solving this, we present the first self-consistent superconducting neutron star equilibria with poloidal and mixed poloidal-toroidal fields and also give the first quantitative results for the corresponding magnetically induced distortions to the star. The poloidal component is dominant in all our configurations. We suggest that the transition from normal to superconducting matter in a young neutron star may cause a large-scale field rearrangement. PMID:25166363

  10. High-Field Superconducting Magnets Supporting PTOLEMY

    NASA Astrophysics Data System (ADS)

    Hopkins, Ann; Luo, Audrey; Osherson, Benjamin; Gentile, Charles; Tully, Chris; Cohen, Adam

    2013-10-01

    The Princeton Tritium Observatory for Light, Early Universe, Massive Neutrino Yield (PTOLEMY) is an experiment planned to collect data on Big Bang relic neutrinos, which are predicted to be amongst the oldest and smallest particles in the universe. Currently, a proof-of-principle prototype is being developed at Princeton Plasma Physics Laboratory to test key technologies associated with the experiment. A prominent technology in the experiment is the Magnetic Adiabatic Collimation with an Electrostatic Filter (MAC-E filter), which guides tritium betas along magnetic field lines generated by superconducting magnets while deflecting those of lower energies. B field mapping is performed to ensure the magnets produce a minimum field at the midpoint of the configuration of the magnets and to verify accuracy of existing models. Preliminary tests indicate the required rapid decrease in B field strength from the bore of the more powerful 3.35 T magnet, with the field dropping to 0.18 T approximately 0.5 feet from the outermost surface of the magnet.

  11. Magnetic configurations of a Co monolayer on Cr substrates

    NASA Astrophysics Data System (ADS)

    Izquierdo, J.; Demangeat, C.

    2000-11-01

    The spin polarization of a single Co monolayer on Cr substrates with low-Miller indices is investigated using the tight-binding linear muffin-tin orbital method. For all Cr substrates we consider epitaxial growth of Co. The Co overlayer is ferromagnetic for the (100) and (111) faces while for the (110) direction the stable solution is a C(22) that gives a zero net magnetization on the Co monolayer. For (100) Cr substrate the effect of the Co overlayer is to decrease dramatically the Cr polarization in the two monolayers underneath the Co and the Co-Cr coupling at the interface is found ferromagnetic. In the case of the (111) surface the effect of Co on the magnetization of the Cr substrate is less pronounced and the Co-Cr coupling is now antiferromagnetic. For the Co monolayer on the (110) surface we obtain a C(22) solution that gives a zero net magnetization per layer, while for the Co bilayer on Cr(110) we get a ferromagnetic configuration. In both cases the magnetic moments at the Cr interface atoms are strongly reduced.

  12. Effects of Satellite Sampling Configurations on Derived Gridded Fields

    NASA Technical Reports Server (NTRS)

    Lait, Leslie R.

    1998-01-01

    Various configurations of a scanning satellite instrument are simulated by sampling realistic fields of nitrous oxide. Synoptic grids are computed from the resulting simulated orbital data and compared to the original sampled data fields. Results are compared with those obtained by flying a simulated satellite over low-resolution fields and fields that are static in time. Although increasing the number of instrument scan positions does provide more information along an orbital swath, using more than three to five scan positions does not significantly increase the accuracy of global synoptic grids using the gridding techniques described here.

  13. Exposure guidelines for magnetic fields

    SciTech Connect

    Miller, G.

    1987-12-01

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

  14. Magnetic field modification of optical magnetic dipoles.

    PubMed

    Armelles, Gaspar; Caballero, Blanca; Cebollada, Alfonso; Garcia-Martin, Antonio; Meneses-Rodríguez, David

    2015-03-11

    Acting on optical magnetic dipoles opens novel routes to govern light-matter interaction. We demonstrate magnetic field modification of the magnetic dipolar moment characteristic of resonant nanoholes in thin magnetoplasmonic films. This is experimentally shown through the demonstration of the magneto-optical analogue of Babinet's principle, where mirror imaged MO spectral dependencies are obtained for two complementary magnetoplasmonic systems: holes in a perforated metallic layer and a layer of disks on a substrate. PMID:25646869

  15. Whistler Modes with Wave Magnetic Fields Exceeding the Ambient Field

    SciTech Connect

    Stenzel, R.L.; Urrutia, J.M.; Strohmaier, K.D.

    2006-03-10

    Whistler-mode wave packets with fields exceeding the ambient dc magnetic field have been excited in a large, high electron-beta plasma. The waves are induced with a loop antenna with dipole moment either along or opposite to the dc field. In the latter case the excited wave packets have the topology of a spheromak but are propagating in the whistler mode along and opposite to the dc magnetic field. Field-reversed configurations with net zero helicity have also been produced. The electron magnetohydrodynamics fields are force free, have wave energy density exceeding the particle energy density, and propagate stably at subelectron thermal velocities through a nearly uniform stationary ion density background.

  16. Whistler modes with wave magnetic fields exceeding the ambient field.

    PubMed

    Stenzel, R L; Urrutia, J M; Strohmaier, K D

    2006-03-10

    Whistler-mode wave packets with fields exceeding the ambient dc magnetic field have been excited in a large, high electron-beta plasma. The waves are induced with a loop antenna with dipole moment either along or opposite to the dc field. In the latter case the excited wave packets have the topology of a spheromak but are propagating in the whistler mode along and opposite to the dc magnetic field. Field-reversed configurations with net zero helicity have also been produced. The electron magnetohydrodynamics fields are force free, have wave energy density exceeding the particle energy density, and propagate stably at subelectron thermal velocities through a nearly uniform stationary ion density background. PMID:16606272

  17. Magnetic-field-dosimetry system

    SciTech Connect

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

    1981-01-21

    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.

  18. The ASTROMAG superconducting magnet facility configured for a free flying satellite

    SciTech Connect

    Green, M.A.; Smoot, G.F.

    1991-06-01

    ASTROMAG is a particle astrophysics facility that was originally configured for the Space Station. The heart of the ASTROMAG facility is a large superconducting magnet which is cooled using superfluid helium. The task of resizing the facility so that it will fly in a satellite in a high angle of inclination orbit is driven by the launch weight capability of the launch rocket and the desire to be able to do nearly the same physics as the Space Station version of ASTROMAG. In order to reduce the launch weight, the magnet and its cryogenic system had to be downsized, yet the integrated field generated by the magnet in the particle detectors has to match the Space Station version of the magnet. The use of aluminum matrix superconductor and oriented composite materials in the magnet insulation permits one to achieve this goal. The net magnetic dipole moment from the ASTROMAG magnet must be small to minimize the torque due to interaction with the earth's magnetic field. The ASTROMAG magnet consists of identical two coils 1.67 meters apart. The two coils are connected in series in persistent mode. Each coil is designed to carry 2.34 million ampere turns. Both coils are mounted on the same magnetic axis and they operate at opposite polarity. This reduces the dipole moment by a factor of more than 1000. This is tolerable for the Space Station version of the magnet. A magnet operating on a free flying satellite requires additional compensation. This report presents the magnet parameters of a free flying version of ASTROMAG and the parameters of the space cryogenic system for the magnet. 12 refs., 6 figs.

  19. The Astromag Superconducting Magnet Facility Configured for a FreeFlying Satellite

    SciTech Connect

    Green, M.A.; Smoot, George F.

    1991-06-01

    ASTROMAG is a particle astrophysics facility that was originally configured for the Space Station. The heart of the ASTROMAG facility is a large superconducting magnet which is cooled using superfluid helium. The task of resizing the facility so that it will fly in a satellite in. a high angle of inclination orbit is driven by the launch weight capability of the launch rocket and the desire to be able to do nearly the same physics as the Space Station version of ASTROMAG. In order to reduce the launch weight, the magnet and its cryogenic system had to be downsized, yet the integrated field generated by the magnet in the particle detectors has to match the Space Station version of the magnet. The use of aluminum matrix superconductor and oriented composite materials in the magnet insulation permits one to achieve this goal. The net magnetic dipole moment from the ASTROMAG magnet must be small to minimize the torque due to interaction with the earth's magnetic field. The ASTROMAG magnet consists of identical two coils 1.67 meters apart. The two coils are connected in series in persistent mode. Each coil is designed to carry 2.34 million ampere turns. Both coils are mounted on the same magnetic axis and they operate at opposite polarity. This reduces the dipole moment by a factor of more than 1000. This is tolerable for the Space Station version of the magnet. A magnet operating on a free flying satellite requires additional compensation. This report presents the magnet parameters of a free flying version of ASTROMAG and the parameters of the space cryogenic system for the magnet.

  20. Mercury's magnetic field and interior

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Ness, N. F.

    1988-01-01

    The magnetic-field data collected on Mercury by the Mariner-10 spacecraft present substantial evidence for an intrinsic global magnetic field. However, studies of Mercury's thermal evolution show that it is most likely that the inner core region of Mercury solidified or froze early in the planet's history. Thus, the explanation of Mercury's magnetic field in the framework of the traditional planetary dynamo is less than certain.

  1. Separatrix radius measurement of field-reversed configuration plasma in FRX-L

    SciTech Connect

    Zhang, S.Y.; Tejero, E.M.; Taccetti, J.M.; Wurden, G.A.; Intrator, T.P.; Waganaar, W.J.; Perkins, R.

    2004-10-01

    Magnetic pickup coils and single turn flux loops are installed on the FRX-L device. The combination of the two measurements provides the excluded flux radius that approximates the separatrix radius of the field-reversed configuration (FRC) plasma. Arrays of similar probes are used to map out local magnetic field dynamics beyond both ends of the theta-coil confinement region to help understand the effects of cusp locations on flux trapping during the FRC formation process. Details on the probe design and system calibrations are presented. The overall system calibration of excluded flux radius measurement is examined by replacing FRC plasma with a known radius aluminum conductor cylinder.

  2. Detection of magnetic barriers in a chaotic domain: first application of finite time Lyapunov exponent method to a magnetic confinement configuration

    NASA Astrophysics Data System (ADS)

    Rubino, G.; Borgogno, D.; Veranda, M.; Bonfiglio, D.; Cappello, S.; Grasso, D.

    2015-08-01

    Magnetic field lines embedded in a plasma confinement system are often characterized by a chaotic motion. This weakens the confinement properties of any magnetic configuration. However, even in case of chaotic domains, magnetic barriers can emerge and limit the field line motion itself. In the context of the numerical simulation of a Reversed-Field Pinch configuration a new magnetic topology analysis, borrowed from previous fluid dynamic studies, is discussed. This methodology relies on the behavior of the Finite Time Lyapunov Exponent (FTLE) associated with the magnetic field. By referring to a previous work in which the magnetic field is given in terms of analytical function (Borgogno et al 2011 Phys. Plasmas 18 102307) the FTLE field shows the presence of ridges, special gradient lines normal to the direction of minimum curvature, forming magnetic barriers. These ridges can be recognized as Lagrangian Coherent Structures (LCSs) for the system, actually opposing the penetration of magnetic field lines across them. In this article a more general numerical scheme for the detection of the LCSs has been adopted that allows analysis of realistic cases in which the magnetic fields are numerically known on a discrete mesh. After a validation test performed on the analytical case, a first application to a numerical magnetohydrodynamics simulation of the RFP, characterized by a broad chaotic region, has been performed. A strong magnetic barrier has been observed that effectively limits the field lines motion inside the chaotic sea.

  3. Experimental evidence of skyrmion-like configurations in bilayer nanodisks with perpendicular magnetic anisotropy

    SciTech Connect

    Stebliy, Maxim E. Kolesnikov, Alexander G.; Davydenko, Alexander V.; Ognev, Alexey V.; Samardak, Alexander S.; Chebotkevich, Ludmila A.

    2015-05-07

    Formation and existence of magnetic skyrmion-like configurations in bilayer nanodisks (Ta(3?nm)/[Co(0.37?nm)/Ni(0.58?nm)]{sub 10}){sub 2} with perpendicular magnetic anisotropy are shown experimentally at room temperature. Magnetization reversal through the skyrmion state is studied using magnetic hysteresis measurements. An evolution of skyrmion configurations in the nanodisk structure is analyzed. Experimental methods and micromagnetic simulations help to understand the magnetization reversal processes occurring through the stable skyrmion-like configurations. Formation of the intermediate C-states during magnetization reversal is demonstrated. The skyrmion number for all possible spin configurations is calculated.

  4. Experimental evidence of skyrmion-like configurations in bilayer nanodisks with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Stebliy, Maxim E.; Kolesnikov, Alexander G.; Davydenko, Alexander V.; Ognev, Alexey V.; Samardak, Alexander S.; Chebotkevich, Ludmila A.

    2015-05-01

    Formation and existence of magnetic skyrmion-like configurations in bilayer nanodisks {Ta(3 nm)/[Co(0.37 nm)/Ni(0.58 nm)]10}2 with perpendicular magnetic anisotropy are shown experimentally at room temperature. Magnetization reversal through the skyrmion state is studied using magnetic hysteresis measurements. An evolution of skyrmion configurations in the nanodisk structure is analyzed. Experimental methods and micromagnetic simulations help to understand the magnetization reversal processes occurring through the stable skyrmion-like configurations. Formation of the intermediate C-states during magnetization reversal is demonstrated. The skyrmion number for all possible spin configurations is calculated.

  5. Domain configuration and magnetization switching in arrays of permalloy nanostripes

    NASA Astrophysics Data System (ADS)

    Iglesias-Freire, .; Jaafar, M.; Prez, L.; de Abril, O.; Vzquez, M.; Asenjo, A.

    2014-04-01

    The proximity effect in the collective behavior of arrays of magnetic nanostripes is currently a subject of intensive research. The imperative of reducing the size and distances between elements in order to achieve higher storage capacity, faster access to the information as well as low energy consumption, brings consequences about the isolated behavior of the elements and devices. Parallel to each other permalloy nanostripes with high aspect ratio have been prepared by the nanolithography technique. The evolution of the closure domains and the magnetization direction in individual nanostructures has been imaged under applied magnetic fields using Variable Field Magnetic Force Microscopy. Moreover, the magnetostatic interactions between neighboring elements and the proximity effects in arrays of such nanostructures have been quantitatively analyzed by Magnetic Force Microscopy and micromagnetic simulations. The agreement between simulations and the experimental results allows us to conclude the relevance of those interactions depending on the geometry characteristics. In particular, results suggest that the magnetostatic coupling between adjacent nanostripes vanishes for separation distances higher than 500 nm.

  6. Magnetic Fields in Early Protostellar Disk Formation

    NASA Astrophysics Data System (ADS)

    González-Casanova, Diego F.; Lazarian, Alexander; Santos-Lima, Reinaldo

    2016-03-01

    We consider formation of accretion disks from a realistically turbulent molecular gas using 3D MHD simulations. In particular, we analyze the effect of the fast turbulent reconnection described by the Lazarian & Vishniac model for the removal of magnetic flux from a disk. With our numerical simulations we demonstrate how the fast reconnection enables protostellar disk formation resolving the so-called “magnetic braking catastrophe.” In particular, we provide a detailed study of the dynamics of a 0.5 M⊙ protostar and the formation of its disk for up to several thousands years. We measure the evolution of the mass, angular momentum, magnetic field, and turbulence around the star. We consider effects of two processes that strongly affect the magnetic transfer of angular momentum, both of which are based on turbulent reconnection: the first, “reconnection diffusion,” removes the magnetic flux from the disk; the other involves the change of the magnetic field's topology, but does not change the absolute value of the magnetic flux through the disk. We demonstrate that for the first mechanism, turbulence causes a magnetic flux transport outward from the inner disk to the ambient medium, thus decreasing the coupling of the disk to the ambient material. A similar effect is achieved through the change of the magnetic field's topology from a split monopole configuration to a dipole configuration. We explore how both mechanisms prevent the catastrophic loss of disk angular momentum and compare both above turbulent reconnection mechanisms with alternative mechanisms from the literature.

  7. Magnetic fields around evolved stars

    NASA Astrophysics Data System (ADS)

    Leal-Ferreira, M.; Vlemmings, W.; Kemball, A.; Amiri, N.; Maercker, M.; Ramstedt, S.; Olofsson, G.

    2014-04-01

    A number of mechanisms, such as magnetic fields, (binary) companions and circumstellar disks have been suggested to be the cause of non-spherical PNe and in particular collimated outflows. This work investigates one of these mechanisms: the magnetic fields. While MHD simulations show that the fields can indeed be important, few observations of magnetic fields have been done so far. We used the VLBA to observe five evolved stars, with the goal of detecting the magnetic field by means of water maser polarization. The sample consists in four AGB stars (IK Tau, RT Vir, IRC+60370 and AP Lyn) and one pPN (OH231.8+4.2). In four of the five sources, several strong maser features were detected allowing us to measure the linear and/or circular polarization. Based on the circular polarization detections, we infer the strength of the component of the field along the line of sight to be between ~30 mG and ~330 mG in the water maser regions of these four sources. When extrapolated to the surface of the stars, the magnetic field strength would be between a few hundred mG and a few Gauss when assuming a toroidal field geometry and higher when assuming more complex magnetic fields. We conclude that the magnetic energy we derived in the water maser regions is higher than the thermal and kinetic energy, leading to the conclusion that, indeed, magnetic fields probably play an important role in shaping Planetary Nebulae.

  8. ELF field in the proximity of complex power line configuration measurement procedures.

    PubMed

    Benes, M; Comelli, M; Villalta, R

    2006-01-01

    The issue of how to measure magnetic induction fields generated by various power line configurations, when there are several power lines that run across the same exposure area, has become a matter of interest and study within the Regional Environment Protection Agency of Friuli Venezia Giulia. In classifying the various power line typologies the definition of double circuit line was given: in this instance the magnetic field is determined by knowing the electrical and geometric parameters of the line. In the case of independent lines instead, the field is undetermined. It is therefore pointed out how, in the latter case, extracting previsional information from a set of measurements of the magnetic field alone is impossible. Making measurements throughout the territory of service has in several cases offered the opportunity to define standard operational procedures. PMID:16410292

  9. Magnetic domain configuration of La0.7 Sr 0.3 MnO 3 patterned elements

    NASA Astrophysics Data System (ADS)

    Vaz, Carlos A. F.; Rhensius, Jan; Bisig, Andre; Klui, Mathias; Heyderman, Laura; Nio, Miguel; Locatelli, Andrea; Gaucher, F.; Galdi, Alice; Mchin, Laurence

    2011-03-01

    The magnetization configuration in small La 0.7 Sr 0.3 Mn O3 elements is investigated as a function of geometry, film thickness, magnetic field, and temperature using x-ray magnetic circular dichroism photoemission electron microscopy (XMCD-PEEM). The patterned elements were defined by focused ion beam (FIB) lithography, and consist of elements varying in shape (from circular, triangular and quadrangular) and size, from 200 nm up to 10 ? m. A strong magnetic contrast is observed for all thicknesses (10-50 nm). The magnetic state in the larger elements tends to be multidomain, with complex configurations that are determined by the presence of local pinning sites. These pinning sites are overcome with increasing temperature, and the magnetic configuration evolves into lower energy states. In contrast, the magnetic configuration of the smaller elements are largely determined by the magnetostatic energy contribution, which gives rise to highly symmetric states as found in 3d ferromagnetic structures. Our results show that the magnetism of small LSMO elements is robust nearly up to the critical temperature, with magnetic configurations that can be controlled by suitable geometrical design.

  10. Magnetic Fields and Massive Star Formation

    NASA Astrophysics Data System (ADS)

    Zhang, Qizhou; Qiu, Keping; Girart, Josep M.; (Baobab Liu, Hauyu; Tang, Ya-Wen; Koch, Patrick M.; Li, Zhi-Yun; Keto, Eric; Ho, Paul T. P.; Rao, Ramprasad; Lai, Shih-Ping; Ching, Tao-Chung; Frau, Pau; Chen, How-Huan; Li, Hua-Bai; Padovani, Marco; Bontemps, Sylvain; Csengeri, Timea; Jurez, Carmen

    2014-09-01

    Massive stars (M > 8 M ?) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 ?m obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of lsim0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within 40 of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the outflow axis appears to be randomly oriented with respect to the magnetic field in the core. This result suggests that at the scale of accretion disks (lsim 103 AU), angular momentum and dynamic interactions possibly due to close binary or multiple systems dominate over magnetic fields. With this unprecedentedly large sample of massive clumps, we argue on a statistical basis that magnetic fields play an important role during the formation of dense cores at spatial scales of 0.01-0.1 pc in the context of massive star and cluster star formation.

  11. Magnetic fields and massive star formation

    SciTech Connect

    Zhang, Qizhou; Keto, Eric; Ho, Paul T. P.; Ching, Tao-Chung; Chen, How-Huan; Qiu, Keping; Girart, Josep M.; Juárez, Carmen; Liu, Hauyu; Tang, Ya-Wen; Koch, Patrick M.; Rao, Ramprasad; Lai, Shih-Ping; Li, Zhi-Yun; Frau, Pau; Li, Hua-Bai; Padovani, Marco; Bontemps, Sylvain

    2014-09-10

    Massive stars (M > 8 M {sub ☉}) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 μm obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of ≲0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within 40° of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the outflow axis appears to be randomly oriented with respect to the magnetic field in the core. This result suggests that at the scale of accretion disks (≲ 10{sup 3} AU), angular momentum and dynamic interactions possibly due to close binary or multiple systems dominate over magnetic fields. With this unprecedentedly large sample of massive clumps, we argue on a statistical basis that magnetic fields play an important role during the formation of dense cores at spatial scales of 0.01-0.1 pc in the context of massive star and cluster star formation.

  12. Magnetic response to applied electrostatic field in external magnetic field

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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 the 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 the lines of force is depicted, both inside and outside the charge, which resembles that of a standard solenoid of classical magnetostatics.

  13. Transport in a stochastic magnetic field

    SciTech Connect

    White, R.B.; Wu, Yanlin . Plasma Physics Lab.); Rax, J.M. . Dept. de Recherches sur la Fusion Controlee)

    1992-01-01

    Collisional heat transport in a stochastic magnetic field configuration is investigated. Well above stochastic threshold, a numerical solution of a Chirikov-Taylor model shows a short-time nonlocal regime, but at large time the Rechester-Rosenbluth effective diffusion is confirmed. Near stochastic threshold, subdiffusive behavior is observed for short mean free paths. The nature of this subdiffusive behavior is understood in terms of the spectrum of islands in the stochastic sea.

  14. Transport in a stochastic magnetic field

    SciTech Connect

    White, R.B.; Wu, Yanlin; Rax, J.M.

    1992-09-01

    Collisional heat transport in a stochastic magnetic field configuration is investigated. Well above stochastic threshold, a numerical solution of a Chirikov-Taylor model shows a short-time nonlocal regime, but at large time the Rechester-Rosenbluth effective diffusion is confirmed. Near stochastic threshold, subdiffusive behavior is observed for short mean free paths. The nature of this subdiffusive behavior is understood in terms of the spectrum of islands in the stochastic sea.

  15. The Impact of Well-Field Configuration on Plume Persistence

    NASA Astrophysics Data System (ADS)

    Guo, Z.; Brusseau, M.

    2013-12-01

    It is now recognized that most sites with large groundwater contaminant plumes will require many decades before cleanup will be achieved under current methods and standards. Conceptually, the factors that contribute to plume persistence have long been established, including uncontrolled source zones, dispersed reservoirs of dissolved (present in lower-permeability zones) and sorbed contaminant, and hydraulic-related factors such as non-optimal remedial well-field performance. Of these potential factors, hydraulic phenomena associated with configuration and operation of the well field employed for remedial operations have received minimal attention. The objective of this research is to investigate the influence of well-field configuration on contaminant mass removal and reduction in contaminant mass discharge (CMD). Mathematical modeling, implemented using MODFLOW and MT3D, was conducted to simulate scenarios with different well-field configurations in both homogenous and heterogeneous aquifers. The system was designed such that contaminant was present as only aqueous and sorbed mass (no separate organic-liquid sources). The impacts of several variables on the results are investigated, including pumping rate, layer thickness, and vertical dispersivity. The results are assessed in terms of the relationship between reductions in CMD and reductions in contaminant mass.

  16. Theory of fossil magnetic field

    NASA Astrophysics Data System (ADS)

    Dudorov, Alexander E.; Khaibrakhmanov, Sergey A.

    2015-02-01

    Theory of fossil magnetic field is based on the observations, analytical estimations and numerical simulations of magnetic flux evolution during star formation in the magnetized cores of molecular clouds. Basic goals, main features of the theory and manifestations of MHD effects in young stellar objects are discussed.

  17. Magnetic structure of current sheets in magnetic fields with a singular X line

    SciTech Connect

    Bogdanov, S. Yu.; Bugrov, S. G.; Gritsyna, V. P.; Zverev, O. V.; Karpov, G. V.; Markov, V. S.; Repin, D. V.; Frank, A. G.

    2007-06-15

    Direct measurements of magnetic fields in a plasma show that current sheets can form in magnetic configurations with an X line in the presence of a longitudinal magnetic field. It is found that, in a plane perpendicular to the X line and to the direction of the main current, the current sheet has two very different dimensions. The tangential and normal components of the magnetic field and current density in the sheet are determined. The influence of the initial conditions (such as the strength of the longitudinal magnetic field, the gradient of the transverse field, and the plasma ion mass) on the current sheet parameters is investigated.

  18. The Effects of Magnetic Nozzle Configurations on Plasma Thrusters

    NASA Technical Reports Server (NTRS)

    Turchi, P. J.

    1997-01-01

    Over the course of eight years, the Ohio State University has performed research in support of electric propulsion development efforts at the NASA Lewis Research Center, Cleveland, OH. This research has been largely devoted to plasma propulsion systems including MagnetoPlasmaDynamic (MPD) thrusters with externally-applied, solenoidal magnetic fields, hollow cathodes, and Pulsed Plasma Microthrusters (PPT's). Both experimental and theoretical work has been performed, as documented in four master's theses, two doctoral dissertations, and numerous technical papers. The present document is the final report for the grant period 5 December 1987 to 31 December 1995, and summarizes all activities. Detailed discussions of each area of activity are provided in appendices: Appendix 1 - Experimental studies of magnetic nozzle effects on plasma thrusters; Appendix 2 - Numerical modeling of applied-field MPD thrusters; Appendix 3 - Theoretical and experimental studies of hollow cathodes; and Appendix 4 -Theoretical, numerical and experimental studies of pulsed plasma thrusters. Especially notable results include the efficacy of using a solenoidal magnetic field downstream of a plasma thruster to collimate the exhaust flow, the development of a new understanding of applied-field MPD thrusters (based on experimentally-validated results from state-of-the art, numerical simulation) leading to predictions of improved performance, an experimentally-validated, first-principles model for orificed, hollow-cathode behavior, and the first time-dependent, two-dimensional calculations of ablation-fed, pulsed plasma thrusters.

  19. Physics and Engineering Assessmetns of the K-DEMO Magnet Configuration

    SciTech Connect

    Neilson, George H.; Brown, Thomas

    2014-09-01

    Increased attention is being given now to studies of next-step fusion facilities with nuclear missions. Among these, South Korea's K DEMO is unique in its focus on a high toroidal magnetic field, large major radius, steady-state tokamak design for the core of a facility to test fusion nuclear components in Phase I and, after upgrades, produce 500 MW of electricity in a Phase II. Innovative features of the K DEMO magnet set include the use of two toroidal field (TF) coil winding packs with conductor grading and a machine configuration designed for vertical maintenance. The magnet arrangement features large TF coils and widely spaced poloidal field (PF) coils to accommodate removal of in-vessel components as large modules. Physics and engineering assessments of the pre-conceptual K-DEMO magnet configuration are reported, including: 1) design point and operating space assessment, 2) conductor assessment, and 3) structural assessment. It is found that a reference design point at 6.8 m major radius and 7.4 T toroidal field provides sufficient operating margins for the 500 MWe Phase II mission. Analyses of candidate cable-in-conduit conductors provide predictions of critical current degradation, both in the initial load cycle and an additionally with cyclic loading. A first-pass global analysis of the magnet system found minimal out-of-plane deformations of the TF coil, but an overstress condition in the inner leg of the TF coil. However an analysis taking into account elastic-plastic behavior, frictional sliding, and displacement shows that the structure can safely carry the load. Although the design evolution is still at an early stage, these assessments support the design point choices to date and the expectation that a feasible solution for the high-field K DEMO magnet system can be found.

  20. Maneuvering thermal conductivity of magnetic nanofluids by tunable magnetic fields

    NASA Astrophysics Data System (ADS)

    Patel, Jaykumar; Parekh, Kinnari; Upadhyay, R. V.

    2015-06-01

    We report an experimental investigation of magnetic field dependent thermal conductivity of a transformer oil base magnetic fluid as a function of volume fractions. In the absence of magnetic field, thermal conductivity increases linearly with an increase in volume fraction, and magnitude of thermal conductivity thus obtained is lower than that predicted by Maxwell's theory. This reveals the presence of clusters/oligomers in the system. On application of magnetic field, it exhibits a non-monotonous increase in thermal conductivity. The results are interpreted using the concept of a two-step homogenization method (which is based on differential effective medium theory). The results show a transformation of particle cluster configuration from long chain like prolate shape to the aggregated drop-like structure with increasing concentration as well as a magnetic field. The aggregated drop-like structure for concentrated system is supported by optical microscopic images. This shape change of clusters reduces thermal conductivity enhancement. Moreover, this structure formation is observed as a dynamic phenomenon, and at 226 mT field, the length of the structure extends with time, becomes maximum, and then reduces. This change results in the increase or decrease of thermal conductivity.

  1. Origin of cosmic magnetic fields.

    PubMed

    Campanelli, Leonardo

    2013-08-01

    We calculate, in the free Maxwell theory, the renormalized quantum vacuum expectation value of the two-point magnetic correlation function in de Sitter inflation. We find that quantum magnetic fluctuations remain constant during inflation instead of being washed out adiabatically, as usually assumed in the literature. The quantum-to-classical transition of super-Hubble magnetic modes during inflation allow us to treat the magnetic field classically after reheating, when it is coupled to the primeval plasma. The actual magnetic field is scale independent and has an intensity of few10(-12)??G if the energy scale of inflation is few10(16)??GeV. Such a field accounts for galactic and galaxy cluster magnetic fields. PMID:23971556

  2. Measurements of magnetic field alignment

    SciTech Connect

    Kuchnir, M.; Schmidt, E.E.

    1987-11-06

    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.

  3. Magnetic Field Relaxation and Current Sheets in an Ideal Plasma

    NASA Astrophysics Data System (ADS)

    Candelaresi, S.; Pontin, D. I.; Hornig, G.

    2015-08-01

    We investigate the existence of magnetohydrostatic equilibria for topologically complex magnetic fields. The approach employed is to perform ideal numerical relaxation experiments. We use a newly developed Lagrangian relaxation scheme that exactly preserves the magnetic field topology during the relaxation. Our configurations include both twisted and sheared fields, of which some fall into the category for which Parker predicted no force-free equilibrium. The first class of field considered contains no magnetic null points, and field lines connect between two perfectly conducting plates. In these cases, we observe only resolved current layers of finite thickness. In further numerical experiments, we confirm that magnetic null points are loci of singular currents.

  4. Magnetic Field Topology and Observed Energy Release Locations

    NASA Astrophysics Data System (ADS)

    Mandrini, C. H.

    2006-08-01

    The magnetic field is thought to be the source of the energy release in many and varied observed coronal phenomena, from the less energetic coronal heating to the most violent flares and prominence eruptions. These phenomena involve not only very different scales from the energetic, but also from the temporal, point of view. Magnetic field reconnection, which is efficient only at very small spatial scales, has been the energy release mechanism that has been so far proposed. From a theoretical point of view, magnetic configurations with a complex topology, i.e. having separatrices, are the ones where current sheets can form in 2D. When going to 3D, and if the photospheric magnetic field is described by a series of isolated polarities (surrounded by field free regions), a complete topological description is given by the skeleton formed by null points, spines, fans and separators, and associated separatrices. However, if the photosphere is fully magnetized, most of the above topological structures disappear: only separatrices associated to coronal magnetic nulls remain. An extra set of separatrices is associated to the field lines curved up above the photosphere (defining the bald-patch locations). For some observed magnetic configurations, those topological structures are enough to understand where flare brightenings appear as a result of magnetic field reconnection. However, solar active phenomena are seen to occur also in a larger variety of configurations. Quasi-separatrix layers, which are regions where there is a drastic change in field-line linkage, generalize the concept of separatrices to magnetic configurations without magnetic null points and bald patches. We will review examples of observed flaring regions and their topologies that show us that magnetic reconnection can occur in wider variety of magnetic configurations than traditionally thought.

  5. Measuring interfacial magnetic configurations with Polarized Neutron Reflectometry

    NASA Astrophysics Data System (ADS)

    Hauet, Thomas

    2009-03-01

    Polarized neutron reflectivity (PNR) is ideally suited for imaging both vertical structural and magnetic variations in the complex magnetic multilayers [1]. During the talk will be described particularly how this technique allows obtaining the magnetic depth-profile of exchange-coupled bilayer. For instance, Gd40Fe60/ Tb12Fe88 is a model system to study exchange-bias phenomena origin in anti-ferromagnetically coupled AF/FM system, like FeF2/Fe. In these systems, unusual properties are observed such as a transition from positive to negative exchange bias field HE as the cooling field Hcf is swept from small to large positive value [2]. Combining complementary techniques that are macroscopic magnetization measurements and PNR, we have demonstrated that the above properties, e.g. the cooling field dependence of HE, come from an interfacial domain wall (iDW) frozen in the TbFe as the sample is cooled down under a field [3, 4]. Moreover, PNR measurements have recently revealed that the frozen iDW is metastable and that the exchange bias training effect in TbFe/GdFe results from the thermally assisted relaxation of the iDW, with field cycling [4, 5]. Overall, PNR studies concerning the TbFe/GdFe have brought strong insights into the exchange bias mechanisms in exchange coupled hard/soft systems with in-plane anisotropy. However we have demonstrated as well that this powerful technique can be applied to systems with perpendicular magnetic anisotropy (PMA). Although, in that case, the perpendicular moments are parallel to the scattering vector and do not give rise to scattering via the neutron selection rules, we have used a unconventional geometry to obtain a depth-dependent magnetic profile of a PMA exchange-coupled system. Specifically, we have characterized antiferromagnetically-coupled, TbFeCo/[Co/Pd] multilayers [6]. [4pt] [1] K.V. O'Donovan et al., Phys. Rev. Lett. 88, 067201 (2002). [0pt] [2] J. Nogues and al. Phys. Rev. Lett. 76, 4624 (1996) [0pt] [3] Y. Henry et al., Phys. Rev. B 73, 134420 (2006) [0pt] [4] T. Hauet et al., Phys. Rev. Lett. 96, 067207 (2006) [0pt] [5] T. Hauet et al., Appl. Phys. Lett. 91, 022505 (2007) [0pt] [6] S. Watson et al., Appl. Phys. Lett. 92, 202507 (2008)

  6. The MAVEN Magnetic Field Investigation

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Espley, J.; Lawton, P.; Murphy, S.; Odom, J.; Oliversen, R.; Sheppard, D.

    2014-01-01

    The MAVEN magnetic field investigation is part of a comprehensive particles and fields subsystem that will measure the magnetic and electric fields and plasma environment of Mars and its interaction with the solar wind. The magnetic field instrumentation consists of two independent tri-axial fluxgate magnetometer sensors, remotely mounted at the outer extremity of the two solar arrays on small extensions ("boomlets"). The sensors are controlled by independent and functionally identical electronics assemblies that are integrated within the particles and fields subsystem and draw their power from redundant power supplies within that system. Each magnetometer measures the ambient vector magnetic field over a wide dynamic range (to 65,536 nT per axis) with a quantization uncertainty of 0.008 nT in the most sensitive dynamic range and an accuracy of better than 0.05%. Both magnetometers sample the ambient magnetic field at an intrinsic sample rate of 32 vector samples per second. Telemetry is transferred from each magnetometer to the particles and fields package once per second and subsequently passed to the spacecraft after some reformatting. The magnetic field data volume may be reduced by averaging and decimation, when necessary to meet telemetry allocations, and application of data compression, utilizing a lossless 8-bit differencing scheme. The MAVEN magnetic field experiment may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. A spacecraft magnetic control program was implemented to provide a magnetically clean environment for the magnetic sensors and the MAVEN mission plan provides for occasional spacecraft maneuvers - multiple rotations about the spacecraft x and z axes - to characterize spacecraft fields and/or instrument offsets in flight.

  7. The MAVEN Magnetic Field Investigation

    NASA Astrophysics Data System (ADS)

    Connerney, J. E. P.; Espley, J.; Lawton, P.; Murphy, S.; Odom, J.; Oliversen, R.; Sheppard, D.

    2015-12-01

    The MAVEN magnetic field investigation is part of a comprehensive particles and fields subsystem that will measure the magnetic and electric fields and plasma environment of Mars and its interaction with the solar wind. The magnetic field instrumentation consists of two independent tri-axial fluxgate magnetometer sensors, remotely mounted at the outer extremity of the two solar arrays on small extensions ("boomlets"). The sensors are controlled by independent and functionally identical electronics assemblies that are integrated within the particles and fields subsystem and draw their power from redundant power supplies within that system. Each magnetometer measures the ambient vector magnetic field over a wide dynamic range (to 65,536 nT per axis) with a resolution of 0.008 nT in the most sensitive dynamic range and an accuracy of better than 0.05 %. Both magnetometers sample the ambient magnetic field at an intrinsic sample rate of 32 vector samples per second. Telemetry is transferred from each magnetometer to the particles and fields package once per second and subsequently passed to the spacecraft after some reformatting. The magnetic field data volume may be reduced by averaging and decimation, when necessary to meet telemetry allocations, and application of data compression, utilizing a lossless 8-bit differencing scheme. The MAVEN magnetic field experiment may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. A spacecraft magnetic control program was implemented to provide a magnetically clean environment for the magnetic sensors and the MAVEN mission plan provides for occasional spacecraft maneuvers—multiple rotations about the spacecraft x and z axes—to characterize spacecraft fields and/or instrument offsets in flight.

  8. Novel technologies and configurations of superconducting magnets for MRI

    NASA Astrophysics Data System (ADS)

    Lvovsky, Yuri; Stautner, Ernst Wolfgang; Zhang, Tao

    2013-09-01

    A review of non-traditional approaches and emerging trends in superconducting magnets for MRI is presented. Novel technologies and concepts have arisen in response to new clinical imaging needs, changes in market cost structure, and the realities of newly developing markets. Among key trends are an increasing emphasis on patient comfort and the need for ‘greener’ magnets with reduced helium usage. The paper starts with a brief overview of the well-optimized conventional MR magnet technology that presently firmly occupies the dominant position in the imaging market up to 9.4 T. Non-traditional magnet geometries, with an emphasis on openness, are reviewed. The prospects of MgB2 and high-temperature superconductors for MRI applications are discussed. In many cases the introduction of novel technologies into a cost-conscious commercial market will be stimulated by growing needs for advanced customized procedures, and specialty scanners such as orthopedic or head imagers can lead the way due to the intrinsic advantages in their design. A review of ultrahigh-field MR is presented, including the largest 11.7 T Iseult magnet. Advanced cryogenics approaches with an emphasis on low-volume helium systems, including hermetically sealed self-contained cryostats requiring no user intervention, as well as future non-traditional non-helium cryogenics, are presented.

  9. Electric current variations and 3D magnetic configuration of coronal jets

    NASA Astrophysics Data System (ADS)

    Schmieder, Brigitte; Harra, Louise K.; Aulanier, Guillaume; Guo, Yang; Demoulin, Pascal; Moreno-Insertis, Fernando, , Prof

    Coronal jets (EUV) were observed by SDO/AIA on September 17, 2010. HMI and THEMIS measured the vector magnetic field from which we derived the magnetic flux, the phostospheric velocity and the vertical electric current. The magnetic configuration was computed with a non linear force-free approach. The phostospheric current pattern of the recurrent jets were associated with the quasi-separatrix layers deduced from the magnetic extrapolation. The large twisted near-by Eiffel-tower-shape jet was also caused by reconnection in current layers containing a null point. This jet cannot be classified precisely within either the quiescent or the blowout jet types. We will show the importance of the existence of bald patches in the low atmosphere

  10. Cosmic Magnetic Fields - An Overview

    NASA Astrophysics Data System (ADS)

    Wielebinski, Richard; Beck, Rainer

    Magnetic fields have been known in antiquity. Aristotle attributes the first of what could be called a scientific discussion on magnetism to Thales, who lived from about 625 BC. In China “magnetic carts” were in use to help the Emperor in his journeys of inspection. Plinius comments that in the Asia Minor province of Magnesia shepherds' staffs get at times “glued” to a stone, a alodestone. In Europe the magnetic compass came through the Arab sailors who met the Portuguese explorers. The first scientific treatise on magnetism, “De Magnete”, was published by William Gilbert who in 1600 described his experiments and suggested that the Earth was a huge magnet. Johannes Kepler was a correspondent of Gilbert and at times suggested that planetary motion was due to magnetic forces. Alas, this concept was demolished by Isaac Newton,who seeing the falling apple decided that gravity was enough. This concept of dealing with gravitational forces only remains en vogue even today. The explanations why magnetic effects must be neglected go from “magnetic energy is only 1% of gravitation” to “magnetic fields only complicate the beautiful computer solutions”. What is disregarded is the fact that magnetic effects are very directional(not omni-directional as gravity) and also the fact that magnetic fields are seen every where in our cosmic universe.

  11. Magnetic field amplifier employing high-Tc bulk superconductor

    NASA Astrophysics Data System (ADS)

    Choi, Seyong; Kiyoshi, Tsukasa; Matsumoto, Shinji

    2009-04-01

    We propose a new device built from a bulk superconductor to enhance the magnetic flux density within a high-field superconducting magnet. The high-temperature superconductor (HTS) bulk application, named the magnetic field amplifier, was constructed from four pieces of Gd-Ba-Cu-O superconductor. The field amplifier has a unique configuration of the bulk superconductor, which suppresses the current on the periphery of the bulk induced by external field variation. We experimentally demonstrated that the field was effectively amplified at the center of the HTS bulk device. By increasing the background field from 12 to 13 T in field-cooling mode, a magnetic flux density of 14.76 T was obtained at the center of the amplifier. The observed multiplication factor was 2.76, corresponding to external field variation. A configuration to further improve efficiency and reduce size is also presented.

  12. Heat pipes for use in a magnetic field

    DOEpatents

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

    1983-07-19

    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.

  13. Heat pipes for use in a magnetic field

    DOEpatents

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

    1983-01-01

    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.

  14. A self-consistent calculation of rotating magnetic fields

    SciTech Connect

    Sperling, J.L.; Glassman, A.J.; Moses, K.G.; Quon, B.H.

    1986-07-01

    A self-consistent method is described for determining the static magnetic-field reduction in a magnetized plasma with a specified density profile by radio-frequency (rf)-driven rotating magnetic fields (RMFs). Electron-ion collisions and transport losses are included in the analysis. Application of RMF current drive to tandem mirrors and rotomak reactors is considered. The results of the calculations show that magnetic wells can be produced in mirror configurations, and reversal of applied static magnetic fields can be generated in rotomark geometrics by RMF for modest investments of rf power at frequencies for which the rf technology is economically attractive.

  15. Field reversed configuration confinement enhancement through edge biasing and neutral beam injection.

    PubMed

    Tuszewski, M; Smirnov, A; Thompson, M C; Korepanov, S; Akhmetov, T; Ivanov, A; Voskoboynikov, R; Schmitz, L; Barnes, D; Binderbauer, M W; Brown, R; Bui, D Q; Clary, R; Conroy, K D; Deng, B H; Dettrick, S A; Douglass, J D; Garate, E; Glass, F J; Gota, H; Guo, H Y; Gupta, D; Gupta, S; Kinley, J S; Knapp, K; Longman, A; Hollins, M; Li, X L; Luo, Y; Mendoza, R; Mok, Y; Necas, A; Primavera, S; Ruskov, E; Schroeder, J H; Sevier, L; Sibley, A; Song, Y; Sun, X; Trask, E; Van Drie, A D; Walters, J K; Wyman, M D

    2012-06-22

    Field reversed configurations (FRCs) with high confinement are obtained in the C-2 device by combining plasma gun edge biasing and neutral beam injection. The plasma gun creates an inward radial electric field that counters the usual FRC spin-up. The n = 2 rotational instability is stabilized without applying quadrupole magnetic fields. The FRCs are nearly axisymmetric, which enables fast ion confinement. The plasma gun also produces E × B shear in the FRC edge layer, which may explain the observed improved particle transport. The FRC confinement times are improved by factors 2 to 4, and the plasma lifetimes are extended from 1 to up to 4 ms. PMID:23004613

  16. PREPROCESSING MAGNETIC FIELDS WITH CHROMOSPHERIC LONGITUDINAL FIELDS

    SciTech Connect

    Yamamoto, Tetsuya T.; Kusano, K.

    2012-06-20

    Nonlinear force-free field (NLFFF) extrapolation is a powerful tool for the modeling of the magnetic field in the solar corona. However, since the photospheric magnetic field does not in general satisfy the force-free condition, some kind of processing is required to assimilate data into the model. In this paper, we report the results of new preprocessing for the NLFFF extrapolation. Through this preprocessing, we expect to obtain magnetic field data similar to those in the chromosphere. In our preprocessing, we add a new term concerning chromospheric longitudinal fields into the optimization function proposed by Wiegelmann et al. We perform a parameter survey of six free parameters to find minimum force- and torque-freeness with the simulated-annealing method. Analyzed data are a photospheric vector magnetogram of AR 10953 observed with the Hinode spectropolarimeter and a chromospheric longitudinal magnetogram observed with SOLIS spectropolarimeter. It is found that some preprocessed fields show the smallest force- and torque-freeness and are very similar to the chromospheric longitudinal fields. On the other hand, other preprocessed fields show noisy maps, although the force- and torque-freeness are of the same order. By analyzing preprocessed noisy maps in the wave number space, we found that small and large wave number components balance out on the force-free index. We also discuss our iteration limit of the simulated-annealing method and magnetic structure broadening in the chromosphere.

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

    SciTech Connect

    Del-Castillo-Negrete, Diego; Blazevski, Daniel

    2014-06-01

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

  18. Thermometers in Low Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Gerak, G.; Begu, S.

    2010-09-01

    In this article the effect of low amplitude DC magnetic fields on different types of thermometers is discussed. By means of a precision water-cooled electromagnet, the effect of a magnetic field on platinum resistance thermometers, thermistors, and type T, J, and K thermocouples was investigated, while thermometers were thermally stabilized in thermostatic baths. Four different baths were used for temperatures from 77 K (-196 C) to 353 K (80 C): liquid nitrogen bath (nitrogen boiling point at atmospheric pressure), ice-point bath, room-temperature air bath, and hot-water bath. The generated DC magnetic field of high relative precision (2 10-4 at 1 T, 4 10-5 short-term stability) and high relative uniformity (2 10-5 over 1 cm2, 10 mm gap) had a magnetic flux density of 1 T in the center of the gap between the magnet pole caps. The results indicate a magnetic effect of up to 100 mK due to a 1 T magnetic field for the types of thermocouples composed of ferromagnetic materials (Fe, Cr, Ni). For platinum resistance thermometers, thermistors, and non-magnetic type T thermocouples, the detected magnetic effect was weaker, i.e., under 10 mK.

  19. Low-Magnetic-Field Magnetars

    NASA Astrophysics Data System (ADS)

    Turolla, Roberto; Esposito, Paolo

    2013-11-01

    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 (≃ 4.4×1013 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.

  20. The magnetic field of Neptune

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, Mario H.; Ness, Norman F.

    1992-01-01

    A model is given of the planetary magnetic field of Neptune based on a spherical harmonic analysis of the observations obtained by the Voyager 2. Generalized inverse techniques are used to partially solve a severely underdetermined inverse problem, and the resulting model is nonunique since the observations are limited in spatial distribution. Dipole, quadrupole, and octupole coefficients are estimated independently of other terms, and the parameters are shown to be well constrained by the measurement data. The large-scale features of the magnetic field including dipole tilt, offset, and harmonic content are found to characterize a magnetic field that is similar to that of Uranus. The traits of Neptune's magnetic field are theorized to relate to the 'ice' interior of the planet, and the dynamo-field generation reflects this poorly conducting planet.

  1. Preflare magnetic and velocity fields

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.; Gaizauskas, V.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M.-J.; Porter, J. G.; Schmeider, B.

    1986-01-01

    A characterization is given of the preflare magnetic field, using theoretical models of force free fields together with observed field structure to determine the general morphology. Direct observational evidence for sheared magnetic fields is presented. The role of this magnetic shear in the flare process is considered within the context of a MHD model that describes the buildup of magnetic energy, and the concept of a critical value of shear is explored. The related subject of electric currents in the preflare state is discussed next, with emphasis on new insights provided by direct calculations of the vertical electric current density from vector magnetograph data and on the role of these currents in producing preflare brightenings. Results from investigations concerning velocity fields in flaring active regions, describing observations and analyses of preflare ejecta, sheared velocities, and vortical motions near flaring sites are given. This is followed by a critical review of prevalent concepts concerning the association of flux emergence with flares

  2. AC photovoltaic module magnetic fields

    SciTech Connect

    Jennings, C.; Chang, G.J.; Reyes, A.B.; Whitaker, C.M.

    1997-12-31

    Implementation of alternating current (AC) photovoltaic (PV) modules, particularly for distributed applications such as PV rooftops and facades, may be slowed by public concern about electric and magnetic fields (EMF). This paper documents magnetic field measurements on an AC PV module, complementing EMF research on direct-current PV modules conducted by PG and E in 1993. Although not comprehensive, the PV EMF data indicate that 60 Hz magnetic fields (the EMF type of greatest public concern) from PV modules are comparable to, or significantly less than, those from household appliances. Given the present EMF research knowledge, AC PV module EMF may not merit considerable concern.

  3. Magnetic fields and scintillator performance

    SciTech Connect

    Green, D.; Ronzhin, A.; Hagopian, V.

    1995-06-01

    Experimental data have shown that the light output of a scintillator depends on the magnitude of the externally applied magnetic fields, and that this variation can affect the calorimeter calibration and possibly resolution. The goal of the measurements presented here is to study the light yield of scintillators in high magnetic fields in conditions that are similar to those anticipated for the LHC CMS detector. Two independent measurements were performed, the first at Fermilab and the second at the National High Magnetic Field Laboratory at Florida State University.

  4. Topology, Magnetic Field, and Strongly Interacting Matter

    NASA Astrophysics Data System (ADS)

    Kharzeev, Dmitri E.

    2015-10-01

    Gauge theories with compact symmetry groups possess topologically nontrivial configurations of gauge field. This characteristic has dramatic implications for the vacuum structure of quantum chromodynamics (QCD) and for the behavior of QCD plasma, as well as for condensed matter systems with chiral quasi-particles. I review the current status of this problem with an emphasis both on the interplay between chirality and a background magnetic field and on the observable manifestations of topology in heavy-ion collisions, Dirac semimetals, neutron stars, and the early Universe.

  5. Gyrokinetic particle simulation of a field reversed configuration

    NASA Astrophysics Data System (ADS)

    Fulton, D. P.; Lau, C. K.; Holod, I.; Lin, Z.; Dettrick, S.

    2016-01-01

    Gyrokinetic particle simulation of the field-reversed configuration (FRC) has been developed using the gyrokinetic toroidal code (GTC). The magnetohydrodynamic equilibrium is mapped from cylindrical coordinates to Boozer coordinates for the FRC core and scrape-off layer (SOL), respectively. A field-aligned mesh is constructed for solving self-consistent electric fields using a semi-spectral solver in a partial torus FRC geometry. This new simulation capability has been successfully verified and driftwave instability in the FRC has been studied using the gyrokinetic simulation for the first time. Initial GTC simulations find that in the FRC core, the ion-scale driftwave is stabilized by the large ion gyroradius. In the SOL, the driftwave is unstable on both ion and electron scales.

  6. Torsional oscillations of neutron stars with highly tangled magnetic fields

    NASA Astrophysics Data System (ADS)

    Sotani, Hajime

    2015-11-01

    To determine the frequencies of magnetic oscillations in neutron stars with highly tangled magnetic fields, we derive the perturbation equations. We assume that the field strength of the global magnetic structure is so small that such fields are negligible compared with tangled fields, which may still be far from a realistic configuration. Then, we systematically examine the spectra of the magnetic oscillations, as varying the magnetic field strength and stellar mass. The frequencies without crust elasticity are completely proportional to the strength of the magnetic field, whose proportionality constant depends strongly on the stellar mass. On the other hand, the oscillation spectra with crust elasticity become more complicated, where the frequencies even for weak magnetic fields are different from the crustal torsional oscillations without magnetic fields. For discussing spectra, the critical field strength can play an important role, and it is determined in such a way that the shear velocity is equivalent to the Alfvén velocity at the crust basis. Additionally, we find that the effect of the crust elasticity can be seen strongly in the fundamental oscillations with a lower harmonic index, ℓ. Unlike the stellar models with a pure dipole magnetic field, we also find that the spectra with highly tangled magnetic fields become discrete, where one can expect many of the eigenfrequencies. Maybe these frequencies could be detected after the violent phenomena breaking the global magnetic field structure.

  7. Magnetic field structure of Mercury

    NASA Astrophysics Data System (ADS)

    Hiremath, K. M.

    2012-04-01

    Recently planet Mercury - an unexplored territory in our solar system - has been of much interest to the scientific community due to recent flybys of the spacecraft MESSENGER that discovered its intrinsic stationary and large-scale dipole like magnetic field structure with an intensity of 300nT confirming Mariner 10 observations. In the present study, with the observed constraint of Mercury's atmospheric magnetic field structure, internal magnetic field structure is modeled as a solution of magnetic diffusion equation. In this study, Mercury's internal structure mainly consists of a stable stratified fluid core and the convective mantle. For simplicity, magnetic diffusivity in both parts of the structure is considered to be uniform and constant with a value represented by a suitable averages. It is further assumed that vigorous convection in the mantle disposes of the electric currents leading to a very high diffusivity in that region. Thus, in order to satisfy observed atmospheric magnetic field structure, Mercury's most likely magnetic field structure consists of a solution of MHD diffusion equation in the core and a combined multipolar (dipole and quadrupole like magnetic field structures embedded in the uniform field) solution of a current free like magnetic field structure in the mantle and in the atmosphere. With imposition of appropriate boundary conditions at the core-mantle boundary for the first two diffusion eigen modes, in order to satisfy the observed field structure, present study puts the constraint on Mercury's core radius to be 2000km. From the estimated magnetic diffusivity and the core radius, it is also possible to estimate the two diffusion eigen modes with their diffusion time scales of 8.6 and 3.7 billion years respectively suggesting that the planet inherits its present-day magnetic field structure from the solar Nebula. It is proposed that permanency of such a large-scale magnetic field structure of the planet is attained during Mercury's early evolutionary history of heavy bombardments by the asteroids and comets supporting the giant impact hypothesis for the formation of Mercury.

  8. Magnetic Field Generation in Stars

    NASA Astrophysics Data System (ADS)

    Ferrario, Lilia; Melatos, Andrew; Zrake, Jonathan

    2015-10-01

    Enormous progress has been made on observing stellar magnetism in stars from the main sequence (particularly thanks to the MiMeS, MAGORI and BOB surveys) through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence, in the generation and stability of neutron star fields.

  9. Real gas flow fields about three dimensional configurations

    NASA Technical Reports Server (NTRS)

    Balakrishnan, A.; Lombard, C. K.; Davy, W. C.

    1983-01-01

    Real gas, inviscid supersonic flow fields over a three-dimensional configuration are determined using a factored implicit algorithm. Air in chemical equilibrium is considered and its local thermodynamic properties are computed by an equilibrium composition method. Numerical solutions are presented for both real and ideal gases at three different Mach numbers and at two different altitudes. Selected results are illustrated by contour plots and are also tabulated for future reference. Results obtained compare well with existing tabulated numerical solutions and hence validate the solution technique.

  10. Instability of the current sheet in the Earth's magnetotail with normal magnetic field

    SciTech Connect

    Bessho, N.; Bhattacharjee, A.

    2014-10-15

    Instability of a current sheet in the Earth's magnetotail has been investigated by two-dimensional fully kinetic simulations. Two types of magnetic configuration have been studied; those with uniform normal magnetic field along the current sheet and those in which the normal magnetic field has a spatial hump. The latter configuration has been proposed by Sitnov and Schindler [Geophys. Res. Lett. 37, L08102 (2010)] as one in which ion tearing modes might grow. The first type of configuration exhibits electron tearing modes when the normal magnetic field is small. The second type of configuration exhibits an instability which does not tear or change the topology of magnetic field lines. The hump in the initial configuration can propagate Earthward in the nonlinear regime, leading to the formation of a dipolarization front. Secondary magnetic islands can form in regions where the normal magnetic field is very weak. Under no conditions do we find the ion tearing instability.

  11. Magnetic Field Effects on Plasma Plumes

    NASA Technical Reports Server (NTRS)

    Ebersohn, F.; Shebalin, J.; Girimaji, S.; Staack, D.

    2012-01-01

    Here, we will discuss our numerical studies of plasma jets and loops, of basic interest for plasma propulsion and plasma astrophysics. Space plasma propulsion systems require strong guiding magnetic fields known as magnetic nozzles to control plasma flow and produce thrust. Propulsion methods currently being developed that require magnetic nozzles include the VAriable Specific Impulse Magnetoplasma Rocket (VASIMR) [1] and magnetoplasmadynamic thrusters. Magnetic nozzles are functionally similar to de Laval nozzles, but are inherently more complex due to electromagnetic field interactions. The two crucial physical phenomenon are thrust production and plasma detachment. Thrust production encompasses the energy conversion within the nozzle and momentum transfer to a spacecraft. Plasma detachment through magnetic reconnection addresses the problem of the fluid separating efficiently from the magnetic field lines to produce maximum thrust. Plasma jets similar to those of VASIMR will be studied with particular interest in dual jet configurations, which begin as a plasma loops between two nozzles. This research strives to fulfill a need for computational study of these systems and should culminate with a greater understanding of the crucial physics of magnetic nozzles with dual jet plasma thrusters, as well as astrophysics problems such as magnetic reconnection and dynamics of coronal loops.[2] To study this problem a novel, hybrid kinetic theory and single fluid magnetohydrodynamic (MHD) solver known as the Magneto-Gas Kinetic Method is used.[3] The solver is comprised of a "hydrodynamic" portion based on the Gas Kinetic Method and a "magnetic" portion that accounts for the electromagnetic behaviour of the fluid through source terms based on the resistive MHD equations. This method is being further developed to include additional physics such as the Hall effect. Here, we will discuss the current level of code development, as well as numerical simulation results

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

    DOEpatents

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

    1991-01-01

    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.

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

    DOEpatents

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

    1991-04-09

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

  14. Broad Ion Beam Extraction from Large Bore ECR Ion Source with Cylindrically Comb-Shaped Magnetic Fields Configuration by Feeding Simultaneously 11 to 13 GHz and 2.45 GHz Microwaves

    SciTech Connect

    Kato, Y.; Satani, T.; Matsui, Y.; Watanabe, T.; Sato, F.; Iida, T.; Muramatsu, M.; Kitagawa, A.; Tanaka, K.; Asaji, T.

    2008-11-03

    We tried to enlarge the operation window of an electron cyclotron resonance (ECR) ion source for producing the ECR plasma confined by cylindrically comb-shaped magnetic field, and for extracting the broad ion beam under the low pressures and low microwave powers. The magnetic field by permanent magnets constructs ECR zones at different positions for 2.45 GHz and 11 to 13 GHz microwaves, respectively. According to probe measurements, profiles of plasma density and temperature are different for using each single microwave. We conduct production of ECR plasma by launching simultaneously these two frequency microwaves, and obtain flat profiles of the electron density and the electron temperature. These profiles are not achieved by feeding single frequency microwave. It is found that plasma can be controllable on spatial profiles beyond wide operation window of plasma parameters. We conducted preliminary extracting and forming large bore ion beam from this source. We will make this source a part of tandem type ion source for the first stage. We investigated feasibility and hope to realize the device which has wide range operation window in a single device to produce many kinds of ion beams as like to universal source based on ECR ion source.

  15. The polar heliospheric magnetic field

    NASA Technical Reports Server (NTRS)

    Jokipii, J. R.; Kota, J.

    1989-01-01

    It is suggested that the polar heliospheric magnetic field, at large heliocentric distances, may deviate considerably from the generally accepted Archimedean spiral. Instead, it is suggested that the large-scale field near the poles may be dominated by randomly-oriented transverse magnetic fields with magnitude much larger than the average spiral. The average vector field is still the spiral, but the average magnitude may be much larger. In addition, the field direction is transverse to the radial direction most of the time instead of being nearly radial. This magnetic-field structure has important consequences for the transport of cosmic rays. Preliminary model calculations suggest changes in the radial gradient of galactic cosmic rays which may improve agreement with observations.

  16. Measuring Earth's Magnetic Field Simply.

    ERIC Educational Resources Information Center

    Stewart, Gay B.

    2000-01-01

    Describes a method for measuring the earth's magnetic field using an empty toilet paper tube, copper wire, clear tape, a battery, a linear variable resistor, a small compass, cardboard, a protractor, and an ammeter. (WRM)

  17. Analysis of Magnetic Plucking Configurations for Frequency Up-Converting Harvesters

    NASA Astrophysics Data System (ADS)

    Xue, T.; Roundy, S.

    2015-12-01

    Magnetic plucking applies the strategy of frequency up-conversion in inertial energy harvesting when the energy source, such as human motion, only provides excitations with very low and irregular frequencies. This paper presents an analysis of three different magnet configurations to achieve magnetic plucking based on a three-dimensional analytical cube permanent magnet model: direct repulsive configuration, orthogonal configuration and indirect repulsive configuration. Simulation and experimental results indicate that the indirect repulsive configuration generates the largest tip displacement given the pratical constraints in designing a wearable energy harvester. We have implemented this configuration in a wrist-worn rotational energy harvester to pluck multiple piezoelectric beams. Other configurations, however, can potentially be advantageous in applications with alternative constraints.

  18. Galactic dynamics with magnetic fields

    NASA Astrophysics Data System (ADS)

    Howes, Gregory Gershom

    Contributing to the effort to unravel the origin and understand the evolution of magnetic fields in the universe, this dissertation focuses on the evolution of the Galactic magnetic field through analytical and numerical approaches. The current state of research into magnetism in the universe is reviewed, with particular emphasis on synthesizing a unified view of the various environments in which magnetic fields have been observed. An analytical examination of the stability of magnetic fields in a sheared flow is presented. Gradient Particle Magnetohydro-dynamics is a new computational algorithm for MHD simulation developed here with validation tests of the method to display its capabilities. Adaptive Particle Refinement provides a general adaptive framework into which this new algorithm can be fit, promising improved computational efficiency and better stability characteristics. A model for numerical evolution of the magnetized Galactic disk is described. Preliminary results of two-dimensional Galactic disk simulations are analyzed to demonstrate the potential of this new computational tool and lend insight into the evolution of the Galactic magnetic field.

  19. Heat flow control in thermo-magnetic convective systems using engineered magnetic fields

    NASA Astrophysics Data System (ADS)

    Lee, Jaewook; Nomura, Tsuyoshi; Dede, Ercan M.

    2012-09-01

    We present the design of a magnetically controlled convective heat transfer system. The underlying thermo-magnetic instability phenomenon is described, and enhanced convective fluid flow patterns are determined using non-linear programming techniques plus a design sensitivity analysis. Specifically, the magnetic fluid body force is computed by finding the optimal distribution and magnetization direction of a magnetic field source, where the objective is to minimize the maximum temperature of a closed loop heat transfer system. Sizeable fluid recirculation zones are induced by arranging magnetic field generation elements in configurations similar to Halbach arrays. Applications include improved heat flow control for electromechanical systems.

  20. A Field-Reversed Configuration Plasma Translated into a Neutral Gas Atmosphere

    NASA Astrophysics Data System (ADS)

    Sekiguchi, Jun'ichi; Asai, Tomohiko; Takahashi, Tsutomu; Ando, Hirotoshi; Arai, Mamiko; Katayama, Seri; Takahashi, Toshiki

    2014-10-01

    A field-reversed configuration (FRC) is a compact toroid dominantly with poloidal magnetic field. Because of its simply-connected configuration, an FRC can be translated axially along a gradient of guide magnetic field, and trapped in a confinement region with quasi-static external magnetic field. FRC translation experiments have been performed several facilities. Translation speed of those translated FRCs is comparable with super-Alfvenic speed of approximately 200 km/s. In this experiments, FRC translation has been performed on the FAT (FRC Amplification via Translation) facility. Achieved translation speed in the case of translation into a confinement chamber maintained as the vacuum state is in the range from 130 to 210 km/s. On the other hand, FRC translation into a statically filled deuterium gas atmosphere has also been performed. In the case of translation into filled neutral gas, FRC translation speed is approximately 80 km/s and the separatrix volume has extremely expanded compared with the case of a vacuum state. The phenomenon suggests the presence of regeneration process of translation kinetic energy back into the internal plasma energy during the translation process. This work was partially supported by ``Nihon University Symbolic Project.'' The authors gratefully acknowledge contributions from Nac Image Technology Inc. on the fast camera measurements.

  1. Results from recent rotating magnetic field experiments on TCS

    SciTech Connect

    Brooks, R. D.; Crawford, E. A.; Hoffman, A. L.; Melnik, P.; Milroy, R. D.; Peter, M.; Pietrzyk, Z. A.; Slough, J. T.; Tobin, S. J.; Votroubek, G. R.; Guo, H. Y.

    2001-01-01

    The Field Reversed Confipation (FRC) is attractive for the design of a magnetic fusion reactor because of its intrinsically high plasma beta, natural divertor, and engineering simplicity. The lifetime of FRCs produced by the conventional field reversed theta pinch (FRTP) method is restricted to only hundreds of microseconds due to resistive flux losses. Rotating Magnetic Field (RMF) offers a promising tool for toroidal current drive in FRCs and maintaining the configurations in steady state.

  2. Magnetic fields on the Sun

    NASA Astrophysics Data System (ADS)

    Howard, R.

    1982-02-01

    Synoptic observations of solar magnetic fields are discussed. Seen in long-term averages, the magnetic fields of the Sun show distinctive behavior. The active-region latitudes are characterized by magnetic fields of preceding polarity. The flow of following polarity fields to make up the polar fields is episodic, not continuous. This field motion is a directed poleward flow and is not due to diffusion. The total magnetic flux on the solar surface, which is related linearly to the calcium emission in integrated sunlight, varies from activity minimum to maximum by a factor of 2 or 3. Nearly all this flux is seen at active-region latitudes-only about 1% is at the poles. The total flux of the Sun disappears from the surface at a very rapid rate and is replaced by new flux. All the field and flux patterns that we see originate in active-region latitudes. The polar magnetic fields of the Sun were observed to change polarity recently. The variations of the full-disk solar flux are shown to lead to the proper rotation rate of the Sun, but the phase of the variations is constant for only a year or two at most.

  3. Electric and magnetic microfields inside and outside space-limited configurations of ions and ionic currents

    NASA Astrophysics Data System (ADS)

    Romanovsky, M. Yu; Ebeling, W.; Schimansky-Geier, L.

    2005-01-01

    The problem of electric and magnetic microfields inside finite spherical systems of stochastically moving ions and outside them is studied. The first possible field of applications is high temperature ion clusters created by laser fields [1]. Other possible applications are nearly spherical liquid systems at room-temperature containing electrolytes. Looking for biological applications we may also think about a cell which is a complicated electrolytic system or even a brain which is a still more complicated system of electrolytic currents. The essential model assumption is the random character of charges motion. We assume in our basic model that we have a finite nearly spherical system of randomly moving charges. Even taking into account that this is at best a caricature of any real system, it might be of interest as a limiting case, which admits a full theoretical treatment. For symmetry reasons, a random configuration of moving charges cannot generate a macroscopic magnetic field, but there will be microscopic fluctuating magnetic fields. Distributions for electric and magnetic microfields inside and outside such space- limited systems are calculated. Spherical systems of randomly distributed moving charges are investigated. Starting from earlier results for infinitely large systems, which lead to Holtsmark- type distributions, we show that the fluctuations in finite charge distributions are larger (in comparison to infinite systems of the same charge density).

  4. The magnetic field of Neptune

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, Mario H.; Ness, Norman F.

    1991-01-01

    The Voyager 2 observations obtained during the Neptune encounter are used to develop a spherical harmonic model of the planetary magnetic field of Neptune. The model yields a dipole of magnitude 0.14 G R(N) exp 3, tilted by 47 deg toward 72 deg west longitude. Neptune's quadrupole is equal to or exceeding in magnitude the surface dipole field; the octupole is also very large, although less well constrained. The characteristics of the Neptune's magnetic field are illustrated using contour maps of the field on the planet's surface.

  5. Optical sensor of magnetic fields

    DOEpatents

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

    1986-03-25

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

  6. Magnetic field induced dynamical chaos

    SciTech Connect

    Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra

    2013-12-15

    In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the xy plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples.

  7. Magnetic field induced dynamical chaos

    SciTech Connect

    Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra

    2013-12-15

    In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the x–y plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples.

  8. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    2015-12-01

    Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 \\upmu G) and in central starburst regions (50-100 \\upmu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 \\upmu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.—Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young galaxies and their dynamical importance during galaxy evolution, will be studied with forthcoming radio telescopes like the Square Kilometre Array.

  9. Magnetic field effect on hemin

    NASA Astrophysics Data System (ADS)

    Bartoszek, Mariola; Balanda, Maria; Skrzypek, Danuta; Drzazga, Zofia

    2001-12-01

    Magnetic behaviour of hemin has been investigated by means of magnetostatic methods, AC-susceptibility measurements and EPR spectroscopy. The measurements were made using polycrystalline and oriented samples of hemin in the temperature range 2.3-292 K and in magnetic fields up to 6 T. In the paramagnetic region, the susceptibility obeys the Curie-Weiss law with positive Curie-Weiss temperature. At low temperature, a rapid increase of the susceptibility is noticed but up to 2 K no long-range correlations are observed. The studies show that the iron ion in hemin exists in two spin states ( S= {5}/{2} and {1}/{2}). The applied magnetic field increases the occupation of the low-spin state. Hemin shows high-field-induced magnetic anisotropy which, similar to the susceptibility, increases with decreasing temperature.

  10. Magnetic fields in quiescent prominences

    NASA Technical Reports Server (NTRS)

    Van Ballegooijen, A. A.; Martens, P. C. H.

    1990-01-01

    The origin of the axial fields in high-latitude quiescent prominences is considered. The fact that almost all quiescent prominences obey the same hemisphere-dependent rule strongly suggests that the solar differential rotation plays an important role in producing the axial fields. However, the observations are inconsistent with the hypothesis that the axial fields are produced by differential rotation acting on an existing coronal magnetic field. Several possible explanations for this discrepancy are considered. The possibility that the sign of the axial field depends on the topology of the magnetic field in which the prominence is embedded is examined, as is the possibility that the neutral line is tilted with respect to the east-west direction, so that differential rotation causes the neutral line also to rotate with time. The possibility that the axial fields of quiescent prominences have their origin below the solar surface is also considered.

  11. Space charge, plasma potential and electric field distributions in HiPIMS discharges of varying configuration

    NASA Astrophysics Data System (ADS)

    Liebig, B.; Bradley, J. W.

    2013-08-01

    An electron-emitting (emissive) probe has been used to study the temporal and spatial distribution of the plasma potential during high-power impulse magnetron sputtering (HiPIMS) discharges with various substrate and magnetic field configurations. The average power was 700 W, with a repetition frequency of 100 Hz and pulse duration of 100 s. Strongly negative plasma potentials exceeding -300 V and electric fields up to 10 kV m-1, caused by strong separation of charges with net charge carrier densities ?n of about 1014 m-3, were observed during the ignition of the discharge. The spatial distribution of the plasma potential in the stable stage of the discharge showed values consistently 5 V more negative for a floating substrate compared with a grounded one, so enhancing electron transport around the insulated substrate to grounded walls. However, this change in the electrical configuration of the plasma does not alter significantly the fraction of ionized sputtered particles (of about 30%) that can potentially reach the substrate. By changing the degree of unbalance of the sputtering source, we find a strong correlation between the electric field strength in the magnetic trap (created through charge separation) and the absolute value (and shape) of the magnetic field. For the more unbalanced magnetron, a flattening of the plasma potential structure (decrease in the axial electric field) was observed close to the target. Our findings show in principle that manipulation of the potential barrier close to the target through changing the magnetic field can regulate the proportion of sputtered and ionized species reaching the substrate.

  12. NUMERICAL SIMULATION OF SOLAR MICROFLARES IN A CANOPY-TYPE MAGNETIC CONFIGURATION

    SciTech Connect

    Jiang, R.-L.; Fang, C.; Chen, P.-F.

    2012-06-01

    Microflares are small activities in the solar low atmosphere; some are in the low corona while others are in the chromosphere. Observations show that some of the microflares are triggered by magnetic reconnection between the emerging flux and a pre-existing background magnetic field. We perform 2.5-dimensional, compressible, resistive magnetohydrodynamic simulations of the magnetic reconnection with gravity considered. The background magnetic field is a canopy-type configuration that is rooted at the boundary of the solar supergranule. By changing the bottom boundary conditions in the simulation, a new magnetic flux emerges at the center of the supergranule and reconnects with the canopy-type magnetic field. We successfully simulate the coronal and chromospheric microflares whose current sheets are located at the corona and the chromosphere, respectively. The microflare with a coronal origin has a larger size and a higher temperature enhancement than the microflare with a chromospheric origin. In the microflares with coronal origins, we also found a hot jet ({approx}1.8 Multiplication-Sign 10{sup 6} K), which is probably related to the observational extreme ultraviolet or soft X-ray jets, and a cold jet ({approx}10{sup 4} K), which is similar to the observational H{alpha}/Ca surges. However, there is only a H{alpha}/Ca bright point in the microflares that have chromospheric origins. The study of parameter dependence shows that the size and strength of the emerging magnetic flux are the key parameters that determine the height of the reconnection location, and they further determine the different observational features of the microflares.

  13. The magnetic field of Uranus

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, Mario H.; Ness, Norman F.

    1987-01-01

    Aspherical harmonic model of the planetary magnetic field of Uranus is obtained from the Voyager 2 encounter observations using generalized inverse techniques which allow partial solutions to complex (underdetermined) problems. The Goddard Space Flight Center 'Q3' model is characterized by a large dipole tilt (58.6 deg) relative to the rotation axis, a dipole moment of 0.228 G R(Uranus radii cubed) and an unusually large quadrupole moment. Characteristics of this complex model magnetic field are illustrated using contour maps of the field on the planet's surface and discussed in the context of possible dynamo generation in the relatively poorly conducting 'ice' mantle.

  14. Magnetic fields and coronal heating

    NASA Astrophysics Data System (ADS)

    Golub, L.; Maxson, C.; Rosner, R.; Vaiana, G. S.; Serio, S.

    1980-05-01

    General considerations concerning the scaling properties of magnetic-field-related coronal heating mechanisms are used to build a two-parameter model for the heating of closed coronal regions. The model predicts the way in which coronal temperature and electron density are related to photospheric magnetic field strength and the size of the region, using the additional constraint provided by the scaling law of Rosner, Tucker, and Vaiana. The model duplicates the observed scaling of total thermal energy content with total longitudinal flux; it also predicts a relation between the coronal energy density (or pressure) and the longitudinal field strength modified by the region scale size.

  15. Magnetic Fields in Molecular Clouds

    NASA Astrophysics Data System (ADS)

    Bourke, T. L.; Goodman, A. A.

    2004-09-01

    Magnetic fields are believed to play an important role in the evolution of molecular clouds, from their large scale structure to dense cores, protostellar envelopes, and protoplanetary disks. How important is unclear, and whether magnetic fields are the dominant force driving star formation at any scale is also unclear. In this review we examine the observational data which address these questions, with particular emphasis on high angular resolution observations. Unfortunately the data do not clarify the situation. It is clear that the fields are important, but to what degree we don't yet know. Observations to date have been limited by the sensitivity of available telescopes and instrumentation. In the future ALMA and the SKA in particular should provide great advances in observational studies of magnetic fields, and we discuss which observations are most desirable when they become available.

  16. The magnetic field of Mercury

    NASA Technical Reports Server (NTRS)

    Ness, N. F.

    1979-01-01

    The paper examines the magnetic field observations and their analyses relating to the determination of the Mercury magnetic field. Methods of analyzing data included: (1) comparison of bow shock and magnetopause relative positions at Mercury to the earth, (2) direct spherical harmonic analysis, (3) magnetosphere modeling by an image dipole, and (4) scaling of a mathematical model for the terrestrial magnetosphere. Dipole moments were determined using partial quadrupole and octupole terms to improve the least-square fit of models to observations; analyses by method (2) yield a convergent series of dipole moments values considered to best represent the intrinsic planetary field. Finally, it is suggested that the origin of the magnetic field of Mercury cannot be uniquely determined, but the sources of convective energy may be radiogenic decay and heat release, gravitational settling, and differentiation of processional torques.

  17. Fibrillation of solar magnetic fields

    NASA Astrophysics Data System (ADS)

    Ashbourn, J. M. A.; Woods, L. C.

    2009-06-01

    Solar magnetic structures are often observed in the form of flux tubes composed of a number of smaller elements called fibres or threads, although theoretically such concentrations should not appear but should be flattened by magnetic diffusivity into a uniform, low intensity field. In this paper we describe a mechanism which may be responsible for the fibrillation and also for the very large diffusivity which dissipates magnetic flux tubes in hours instead of years. Firstly, the electric current associated with magnetic field gradients usually increases the local electron temperature and reduces the resistivity, so that the current becomes concentrated into sheets or streamers. Secondly, the magnetic field gradients continue to increase until the current magnitude reaches its limit, which is determined by the electron-ion streaming instability. Then with appropriate temperature and number densities, the Larmor radius of the ions overlaps the near discontinuity in Bz and generates a sharply peaked fluid motion at the edge that is close to the thermal speed. Finally, the resulting vorticity generates an axial magnetic field opposing Bz in the term partial B_z/partial t, and if this is sufficient to change the sign of this term, the very unstable backward heat equation results. This instability repeatedly switches on and off and maintains the magnetic structure in the fibrillated form. Such structures are eventually eliminated by magnetic diffusivity in the usual way, but because of the fluctuations in Bz, this occurs at a vastly increased rate. We show that this phenomenon increases the magnetic diffusivity, D, by a factor 108 in agreement with some observations of plasma loops and supergranules.

  18. Effects of magnetic configuration on divertor power and particle deposition for long pulse operation in EAST

    NASA Astrophysics Data System (ADS)

    Guo, H. Y.; Xia, T. Y.; Liu, S. C.; Wang, H. Q.; Wang, L.; Xu, X. Q.

    2015-08-01

    The magnetic configuration exhibits a strong influence on the dynamics of Edge Localized Modes (ELMs), as demonstrated in the EAST superconducting tokamak. We find that poloidal drifts play an important role in particle deposition during the ELMs, leading to a strong up/down asymmetry in the double null divertor configuration, favoring the upper divertor for normal toroidal field, Bt, i.e., with the ion ∇B drift towards the bottom, while the heat flux distribution appears to be rather uniform during ELMs. These observations are well reproduced by the boundary plasma turbulence code, BOUT++. As divertor pumping was only available at the bottom, the preferential particle flow towards the bottom divertor associated with reverse Bt led to a preferred scenario for long pulse operation in EAST.

  19. Superconductive magnetic energy storage (SMES) external fields and safety considerations

    SciTech Connect

    Polk, C. . Dept. of Electrical Engineering); Boom, R.W.; Eyssa, Y.M. . Applied Superconductivity Center)

    1992-01-01

    This paper addresses preferred SMES configurations and the external magnetic fields which they generate. Possible biological effects of fields are reviewed briefly. It is proposed that SMES units be fenced at the 10 gauss (1 mT) level to keep unrestricted areas safe, even for persons with cardiac pacemakers. For a full size 5000 MWh (1.8 {times} 10 {sup 13} J) SMES the magnetic field decreases to 10 gauss at a radial distance of 2 km from the center of the coil. Other considerations related to the environmental impact of large SMES magnetic fields are discussed briefly.

  20. Profile stabilization of tilt mode in a Field Reversed Configuration

    SciTech Connect

    Cobb, J.W.; Tajima, T.; Barnes, D.C.

    1993-06-01

    The possibility of stabilizing the tilt mode in Field Reversed Configurations without resorting to explicit kinetic effects such as large ion orbits is investigated. Various pressure profiles, P({Psi}), are chosen, including ``hollow`` profiles where current is strongly peaked near the separatrix. Numerical equilibria are used as input for an initial value simulation which uses an extended Magnetohydrodynamic (MHD) model that includes viscous and Hall terms. Tilt stability is found for specific hollow profiles when accompanied by high values of separatrix beta, {beta}{sub sep}. The stable profiles also have moderate to large elongation, racetrack separatrix shape, and lower values of 3, average ratio of Larmor radius to device radius. The stability is unaffected by changes in viscosity, but the neglect of the Hall term does cause stable results to become marginal or unstable. Implications for interpretation of recent experiments are discussed.

  1. Flux Transport and the Sun's Global Magnetic Field

    NASA Technical Reports Server (NTRS)

    Hathaway, David H.

    2010-01-01

    The Sun s global magnetic field is produced and evolved through the emergence of magnetic flux in active regions and its transport across the solar surface by the axisymmetric differential rotation and meridional flow and the non-axisymmetric convective flows of granulation, supergranulation, and giant cell convection. Maps of the global magnetic field serve as the inner boundary condition for space weather. The photospheric magnetic field and its evolution determine the coronal and solar wind structures through which CMEs must propagate and in which solar energetic particles are accelerated and propagate. Producing magnetic maps which best represent the actual field configuration at any instant requires knowing the magnetic field over the observed hemisphere as well as knowing the flows that transport flux. From our Earth-based vantage point we only observe the front-side hemisphere and each pole is observable for only six months of the year at best. Models for the surface magnetic flux transport can be used to provide updates to the magnetic field configuration in those unseen regions. In this presentation I will describe successes and failures of surface flux transport and present new observations on the structure, the solar cycle variability, and the evolution of the flows involved in magnetic flux transport. I find that supergranules play the dominant role due to their strong flow velocities and long lifetimes. Flux is transported by differential rotation and meridional flow only to the extent that the supergranules participate in those two flows.

  2. Indoor localization using magnetic fields

    NASA Astrophysics Data System (ADS)

    Pathapati Subbu, Kalyan Sasidhar

    Indoor localization consists of locating oneself inside new buildings. GPS does not work indoors due to multipath reflection and signal blockage. WiFi based systems assume ubiquitous availability and infrastructure based systems require expensive installations, hence making indoor localization an open problem. This dissertation consists of solving the problem of indoor localization by thoroughly exploiting the indoor ambient magnetic fields comprising mainly of disturbances termed as anomalies in the Earth's magnetic field caused by pillars, doors and elevators in hallways which are ferromagnetic in nature. By observing uniqueness in magnetic signatures collected from different campus buildings, the work presents the identification of landmarks and guideposts from these signatures and further develops magnetic maps of buildings - all of which can be used to locate and navigate people indoors. To understand the reason behind these anomalies, first a comparison between the measured and model generated Earth's magnetic field is made, verifying the presence of a constant field without any disturbances. Then by modeling the magnetic field behavior of different pillars such as steel reinforced concrete, solid steel, and other structures like doors and elevators, the interaction of the Earth's field with the ferromagnetic fields is described thereby explaining the causes of the uniqueness in the signatures that comprise these disturbances. Next, by employing the dynamic time warping algorithm to account for time differences in signatures obtained from users walking at different speeds, an indoor localization application capable of classifying locations using the magnetic signatures is developed solely on the smart phone. The application required users to walk short distances of 3-6 m anywhere in hallway to be located with accuracies of 80-99%. The classification framework was further validated with over 90% accuracies using model generated magnetic signatures representing hallways with different kinds of pillars, doors and elevators. All in all, this dissertation contributes the following: 1) provides a framework for understanding the presence of ambient magnetic fields indoors and utilizing them to solve the indoor localization problem; 2) develops an application that is independent of the user and the smart phones and 3) requires no other infrastructure since it is deployed on a device that encapsulates the sensing, computing and inferring functionalities, thereby making it a novel contribution to the mobile and pervasive computing domain.

  3. Magnetic field of the Earth

    NASA Astrophysics Data System (ADS)

    Popov, Aleksey

    2013-04-01

    The magnetic field of the Earth has global meaning for a life on the Earth. The world geophysical science explains: - occurrence of a magnetic field of the Earth it is transformation of kinetic energy of movements of the fused iron in the liquid core of Earth - into the magnetic energy; - the warming up of a kernel of the Earth occurs due to radioactive disintegration of elements, with excretion of thermal energy. The world science does not define the reasons: - drift of a magnetic dipole on 0,2 a year to the West; - drift of lithospheric slabs and continents. The author offers: an alternative variant existing in a world science the theories "Geodynamo" - it is the theory « the Magnetic field of the Earth », created on the basis of physical laws. Education of a magnetic field of the Earth occurs at moving the electric charge located in a liquid kernel, at rotation of the Earth. At calculation of a magnetic field is used law the Bio Savara for a ring electric current: dB = . Magnetic induction in a kernel of the Earth: B = 2,58 Gs. According to the law of electromagnetic induction the Faradey, rotation of a iron kernel of the Earth in magnetic field causes occurrence of an electric field Emf which moves electrons from the center of a kernel towards the mantle. So of arise the radial electric currents. The magnetic field amplifies the iron of mantle and a kernel of the Earth. As a result of action of a radial electric field the electrons will flow from the center of a kernel in a layer of an electric charge. The central part of a kernel represents the field with a positive electric charge, which creates inverse magnetic field Binv and Emfinv When ?mfinv = ?mf ; ?inv = B, there will be an inversion a magnetic field of the Earth. It is a fact: drift of a magnetic dipole of the Earth in the western direction approximately 0,2 longitude, into a year. Radial electric currents a actions with the basic magnetic field of a Earth - it turn a kernel. It coincides with laws of electromagnetism. According to a rule of the left hand: if the magnetic field in a kernel is directed to drawing, electric current are directed to an axis of rotation of the Earth, - a action of force clockwise (to West). Definition of the force causing drift a kernel according to the law of Ampere F = IBlsin. Powerful force 3,5 × 1012 Nyton, what makes drift of the central part of a kernel of the Earth on 0,2 the longitude in year to West, and also it is engine of the mechanism of movement of slabs together with continents. Movement of a core of the Earth carry out around of a terrestrial axis one circulation in the western direction in 2000 of years. Linear speed of rotation of a kernel concerning a mantle on border the mantle a kernel: V = × 3,471 × 10 = 3,818 × 10 m/s = 33 m/day = 12 km/years. Considering greater viscosity of a mantle, the powerful energy at rotation of a kernel seize a mantle and lithospheric slabs and makes their collisions as a result of which there are earthquakes and volcano. Continents Northern and Southern America every year separate from the Europe and Africa on several centimeters. Atlantic ocean as a result of movement of these slabs with such speed was formed for 200 million years, that in comparison with the age of the Earth - several billions years, not so long time. Drift of a kernel in the western direction is a principal cause of delay of speed of rotation of the Earth. Flow of radial electric currents allot according to the law of Joule - Lenz, the quantity of warmth : Q = I2Rt = IUt, of thermal energy 6,92 × 1017 calories/year. This defines heating of a kernel and the Earth as a whole. In the valley of the median-Atlantic ridge having numerous volcanos, the lava flow constantly thus warm up waters of Atlantic ocean. It is a fact the warm current Gulf Stream. Thawing of a permafrost and ices of Arctic ocean, of glaciers of Greenland and Antarctica is acknowledgement: the warmth of earth defines character of thawing of glaciers and a permafrost. This is a global warming. The version of the author: the periods of inversion of a magnetic field of the Earth determine cycles of the Ice Age. At inversions of a magnetic field when B=0, radial electric currents are small or are absent, excretion of thermal energy minimally or an equal to zero,it is the beginning of the cooling the Earth and offensive of the Ice Age. Disappearance warm current Gulf Stream warming the north of the Europe and Canada. Drift of a magnetic dipole of the Earth in a rotation the opposite to rotation of the Earth, is acknowledgement of drift of a kernel of the Earth in a rotation the opposite to rotation of the Earth and is acknowledgement of the theory « the Magnetic field of the Earth ». The author continues to develop the theory « the Magnetic field of the Earth » and invites geophysicists to accept in it participation in it.

  4. Comparison of the field configurations of the magnetotails of Uranus and Neptune

    NASA Technical Reports Server (NTRS)

    Lepping, R. P.

    1994-01-01

    The magnetic field configuration-states of the magnetotails of the planets Uranus and Neptune are compared. Earth's case is also briefly treated, as well as some related aspects of the other three magnetic planets. In Uranus' case, due to the large tilt (59 deg) of the planet's magnetic dipole with respect to its spin axis and the unusual obliquity of that axis, the angle of attack (alpha) of the solar wind with respect to dipole alignment goes through all possible angles, 0 deg to 180 deg, yielding a very broad spectrum of configuration-states of its tail. Cases are discussed where the planetary magnetic dipole is either aligned with the Sun-planet-line ('pole-on' state) or perpendicular to it and some intermediate states, for both Uranus and Neptune. Only Uranus experiences the pole-on state, which next occurs in November 1999 (+/- 2 months); last year (1993.2) it had the first 'perpendicular' state since Voyager encounter which resembles Earth's case. Neptune never has a pole-on configuration, but it gets as close as alpha = 14 deg from it; the next occurrence is early in 2003. At Voyager encounter Neptune's magnetotail apparently rapidly migrated through a broad spectrum of field structures with near extreme states resembling an Earth-like case on the one hand and a cylindrically symmetric one on the other. Magnetopause 'openness' should dramatically change in terms of the rapidly changing angle of attack throughout a planetary day for these two planets, and this has important implications for their magnetotails. Any future manetospheric mission plans for Uranus or Neptune should take in to consideration the allowed range of values for alpha for the epoch of interest; this is especially of concern for Uranus which has a pole-on state, and all possible alphas, around the middle of 2014, 20 years from now.

  5. Observations of Mercury's magnetic field

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.

    1975-01-01

    Magnetic field data obtained by Mariner 10 during the third and final encounter with the planet Mercury on 16 March 1975 were studied. A well developed bow shock and modest magnetosphere, previously observed at first encounter on 29 March 1974, were again observed. In addition, a much stronger magnetic field near closest approach, 400 gamma versus 98 gamma, was observed at an altitude of 327 km and approximately 70 deg north Mercurian latitude. Spherical harmonic analysis of the data provide an estimate of the centered planetary magnetic dipole of 4.7 x 10 to the 22nd power Gauss/cu cm with the axis tilted 12 deg to the rotation axis and in the same sense as Earth's. The interplanetary field was sufficiently different between first and third encounters that in addition to the very large field magnitude observed, it argues strongly against a complex induction process generating the observed planetary field. While a possibility exists that Mercury possesses a remanent field due to magnetization early in its formation, a present day active dynamo seems to be a more likely candidate for its origin.

  6. The configuration of the auroral distribution for interplanetary magnetic field B sub z northward. 1. IMF B sub x and B sub y dependencies as observed by the Viking satellite

    SciTech Connect

    Eliphinstone, R.D.; Jankowska, K.; Murphree, J.S.; Cogger, L.L. )

    1990-05-01

    Viking images obtained throughout 1986 have been utilized in combination with IMP 8 satellite measurements of the interplanetary magnetic fields (IMF) to determine typical northern hemisphere auroral distributions for a variety of IMF B{sub z} positive conditions. Varying B{sub y} has an effect which is consistent with expected results. That is, B{sub y} positive implies high-latitude auroral arcs in the dusk sector while negative B{sub y} gives dawn sector polar arcs. A new result gives significant importance to the B{sub x} component of the IMF. B{sub x} toward the Sun (B{sub y} = 0) gives polar arcs on both dawn and dusk with comparatively weak UV emissions. With B{sub x} away from the Sun (B{sub y} = 0) a single Sun-aligned morning sector polar arc dominates the auroral distribution. Azimuthal angle changes to the IMF of only 45{degree} seem to affect the global auroral distribution with time scales of less than 2-3 hours. Poleward boundaries of the aurora were found to have a strong dependence on the IMF azimuthal angle which varied according to the magnetic local time investigated.

  7. Dynamo generated magnetic configurations in accretion discs and the nature of quasi-periodic oscillations in accreting binary systems

    NASA Astrophysics Data System (ADS)

    Moss, D.; Sokoloff, D.; Suleimanov, V.

    2016-04-01

    Context. Magnetic fields are important for accretion disc structure. Magnetic fields in a disc system may be transported with the accreted matter. They can be associated with either the central body and/or jet, and be fossil or dynamo excited in situ. Aims: We consider dynamo excitation of magnetic fields in accretion discs of accreting binary systems in an attempt to clarify possible configurations of dynamo generated magnetic fields. We first model the entire disc with realistic radial extent and thickness using an alpha-quenching non-linearity. We then study the simultaneous effect of feedback from the Lorentz force from the dynamo-generated field. Methods: We perform numerical simulations in the framework of a relatively simple mean-field model which allows the generation of global magnetic configurations. Results: We explore a range of possibilities for the dynamo number, and find quadrupolar-type solutions with irregular temporal oscillations that might be compared to observed rapid luminosity fluctuations. The dipolar symmetry models with Rα< 0 have lobes of strong toroidal field adjacent to the rotation axis that could be relevant to jet launching phenomena. Conclusions: We have explored and extended the solutions known for thin accretion discs.

  8. Satellite to study earth's magnetic field

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The Magnetic Field Satellite (Magsat) designed to measure the near earth magnetic field and crustal anomalies is briefly described. A scalar magnetometer to measure the magnitude of the earth's crustal magnetic field and a vector magnetometer to measure magnetic field direction as well as magnitude are included. The mission and its objectives are summarized along with the data collection and processing system.

  9. Reynolds stress flow shear and turbulent energy transfer in reversed field pinch configuration

    NASA Astrophysics Data System (ADS)

    Vianello, Nicola; Spolaore, Monica; Serianni, Gianluigi; Regnoli, Giorgio; Spada, Emanuele; Antoni, Vanni; Bergsker, Henric; Drake, James R.

    2003-10-01

    The role of Reynolds Stress tensor on flow generation in turbulent fluids and plasmas is still an open question and the comprehension of its behavior may assist the understanding of improved confinement scenario. It is generally believed that shear flow generation may occur by an interaction of the turbulent Reynolds stress with the shear flow. It is also generally believed that this mechanism may influence the generation of zonal flow shears. The evaluation of the complete Reynolds Stress tensor requires contemporary measurements of its electrostatic and magnetic part: this requirement is more restrictive for Reversed Field Pinch configuration where magnetic fluctuations are larger than in tokamak . A new diagnostic system which combines electrostatic and magnetic probes has been installed in the edge region of Extrap-T2R reversed field pinch. With this new probe the Reynolds stress tensor has been deduced and its radial profile has been reconstructed on a shot to shot basis exploring differen plasma conditions. These profiles have been compared with the naturally occurring velocity flow profile, in particular during Pulsed Poloidal Current Drive experiment, where a strong variation of ExB flow radial profile has been registered. The study of the temporal evolution of Reynolds stress reveals the appearance of strong localized bursts: these are considered in relation with global MHD relaxation phenomena, which naturally occur in the core of an RFP plasma sustaining its configuration.

  10. Transverse magnetic surface plasmons and complete absorption supported by doped graphene in Otto configuration

    NASA Astrophysics Data System (ADS)

    Ramos-Mendieta, F.; Hernndez-Lpez, J. A.; Palomino-Ovando, M.

    2014-06-01

    High sensitivity of the Attenuated Total Reflectance technique for exciting transverse magnetic surface plasmons in free-standing doped graphene is reported; complete agreement with the electromagnetic dispersion relation is numerically demonstrated in the terahertz regime. By reducing the air gap between prism and graphene in the Otto configuration we found that the surface plasmon excitation is weakened, but interference effects arise producing perfect absorption. At 5 THz two dips of zero-reflection were found, one of them with residual plasmonic contribution. Consequently, the reflection can be suppressed by changing the separation between prism and graphene; it is not needed to modify the graphene doping level. Conditions for destructive interference leading to complete absorption are presented and a particular behavior of the evanescent magnetic fields just at perfect absorption is reported

  11. On the magnetic configuration near Venus: EOF modeling and statistical analyses based on Venus Express measurements

    NASA Astrophysics Data System (ADS)

    He, M.; Vogt, J.; Zhang, T.; Rong, Z.

    2015-10-01

    More than 2000 orbits of Venus Express magnetic field measurementsare used for Orthogonal Function (EOF) analysis to study and model the magnetic environment over the Venus northern polar cap. The modeling results extract the dominant coherent variations, separate the known physical phenomenaon different EOFs and identify the most important driving factors. EOF1 represents the magnetic draping configuration of IMF Bz component whereas EOF2 is controlled by IMF By component and presents the draping and piling-up of IMF By. Besides, our analysis illustrates an asymmetric response of magnetic By component to IMF between the ±E hemispheres,constricted over the terminator (about 90-93° Solar Zeniths Angle) below 300km altitude. The magnetic By component increases as the increase of the parallel IMF component in the +E hemisphere but antiparallel IMF component the -E. To detail the asymmetry, we define a new coordinate system referring to the Sun-Venus-VEX plane which is more robust in comparison with the SVE or VSO coordinate system, and develop a new data averaging method which balances the significance and resolution of data representation.Our result suggests the asymmetry is neither resulting from a large plane of current nor a line of current.

  12. A new high performance field reversed configuration operating regime in the C-2 device

    SciTech Connect

    Tuszewski, M.; Smirnov, A.; Thompson, M. C.; Barnes, D.; Binderbauer, M. W.; Brown, R.; Bui, D. Q.; Clary, R.; Conroy, K. D.; Deng, B. H.; Dettrick, S. A.; Douglass, J. D.; Garate, E.; Glass, F. J.; Gota, H.; Guo, H.Y.; Gupta, D.; Gupta, S.; Kinley, J. S.; Knapp, K.; and others

    2012-05-15

    Large field reversed configurations (FRCs) are produced in the C-2 device by combining dynamic formation and merging processes. The good confinement of these FRCs must be further improved to achieve sustainment with neutral beam (NB) injection and pellet fuelling. A plasma gun is installed at one end of the C-2 device to attempt electric field control of the FRC edge layer. The gun inward radial electric field counters the usual FRC spin-up and mitigates the n = 2 rotational instability without applying quadrupole magnetic fields. Better plasma centering is also obtained, presumably from line-tying to the gun electrodes. The combined effects of the plasma gun and of neutral beam injection lead to the high performance FRC operating regime, with FRC lifetimes up to 3 ms and with FRC confinement times improved by factors 2 to 4.

  13. Mathematical modeling of transformation process of structurally unstable magnetic configurations into structurally stable ones in two-dimensional and three-dimensional geometry

    NASA Astrophysics Data System (ADS)

    Inovenkov, Igor; Echkina, Eugenia; Ponomarenko, Loubov

    Magnetic reconnection is a fundamental process in astrophysical, space and laboratory plasma. In essence, it represents a change of topology of the magnetic field caused by readjustment of the structure of the magnetic field lines. This change leads to release of energy accumulated in the field. We consider transformation process of structurally unstable magnetic configurations into the structurally steady ones from the point of view of the сatastrophe theory. Special attention is paid to modeling of evolution of the structurally unstable three-dimensional magnetic fields.

  14. Magnetic levitation configuration incorporating levitation, guidance and linear synchronous motor

    SciTech Connect

    Coffey, H.T.

    1993-10-19

    A propulsion and suspension system for an inductive repulsion type magnetically levitated vehicle which is propelled and suspended by a system which includes propulsion windings which form a linear synchronous motor and conductive guideways, adjacent to the propulsion windings, where both combine to partially encircling the vehicle-borne superconducting magnets. A three phase power source is used with the linear synchronous motor to produce a traveling magnetic wave which in conjunction with the magnets propel the vehicle. The conductive guideway combines with the superconducting magnets to provide for vehicle levitation. 3 figures.

  15. Magnetic levitation configuration incorporating levitation, guidance and linear synchronous motor

    SciTech Connect

    Coffey, Howard T.

    1993-01-01

    A propulsion and suspension system for an inductive repulsion type magnetically levitated vehicle which is propelled and suspended by a system which includes propulsion windings which form a linear synchronous motor and conductive guideways, adjacent to the propulsion windings, where both combine to partially encircling the vehicle-borne superconducting magnets. A three phase power source is used with the linear synchronous motor to produce a traveling magnetic wave which in conjunction with the magnets propel the vehicle. The conductive guideway combines with the superconducting magnets to provide for vehicle leviation.

  16. Magnetic levitation configuration incorporating levitation, guidance and linear synchronous motor

    SciTech Connect

    Coffey, H.T.

    1992-12-31

    A propulsion and suspension system for an inductive repulsion type magnetically levitated vehicle which is propelled and suspended by a system which includes propulsion windings which form a linear synchronous motor and conductive guideways, adjacent to the propulsion windings, where both combine to partially encircling the vehicle-borne superconducting magnets. A three phase power source is used with the linear synchronous motor to produce a traveling magnetic wave which in conjunction with the magnets propel the vehicle. The conductive guideway combines with the superconducting magnets to provide for vehicle leviation.

  17. Tearing relaxation and the globalization of transport in field-reversed configurations

    SciTech Connect

    Steinhauer, Loren; Barnes, D. C.

    2009-09-15

    Tearing instability of field-reversed configurations (FRC) is investigated using the method of neighboring equilibria. It is shown that the conducting wall position in experiment lies very close to the location needed for tearing stability. This strongly suggests that vigorous but benign tearing modes, acting globally, are the engine of continual self-organization in FRCs, i.e., tearing relaxation. It also explains the ''profile consistency'' and anomalous loss rate of magnetic flux. In effect, tearing globalizes the effect of edge-driven transport.

  18. Manipulation of magnetic state in nanostructures by perpendicular anisotropy and magnetic field

    SciTech Connect

    Chen, J. P.; Xie, Y. L.; Chu, P.; Wang, Y. L.; Wang, Z. Q.; Gao, X. S.; Liu, J.-M.

    2014-06-28

    We investigate the transitions of spin configurations in ultrathin nanostructures by tuning the perpendicular anisotropy (K{sub z}) and out-of-plane magnetic field (H), using the Monte Carlo simulation. It is revealed that enhancing the anisotropy K{sub z} can drive the evolution of in-plane vortex state into intriguing saturated magnetization states under various H, such as the bubble domain state and quadruple-block-domain state etc. The spin configurations of these states exhibit remarkable H-dependence. In addition, the strong effects of geometry and size on the spin configurations of nanostructures are observed. In particular, a series of edged states occur in the circular disk-shaped lattices, and rich intricate saturated magnetization patterns appear in big lattices. It is suggested that the magnetic states can be manipulated by varying the perpendicular anisotropy, magnetic field, and geometry/size of the nanostructures. Furthermore, the stability (retention capacity) of the saturated magnetization states upon varying magnetic field is predicted, suggesting the potential applications of these saturated magnetization states in magnetic field-controlled data storages.

  19. Photospheric and coronal magnetic fields

    SciTech Connect

    Sheeley, N.R., Jr. )

    1991-01-01

    Research on small-scale and large-scale photospheric and coronal magnetic fields during 1987-1990 is reviewed, focusing on observational studies. Particular attention is given to the new techniques, which include the correlation tracking of granules, the use of highly Zeeman-sensitive infrared spectral lines and multiple lines to deduce small-scale field strength, the application of long integration times coupled with good seeing conditions to study weak fields, and the use of high-resolution CCD detectors together with computer image-processing techniques to obtain images with unsurpassed spatial resolution. Synoptic observations of large-scale fields during the sunspot cycle are also discussed. 101 refs.

  20. Effect of magnetic configuration on frequency of NBI-driven Alfvn modes in TJ-II

    NASA Astrophysics Data System (ADS)

    Melnikov, A. V.; Ochando, M.; Ascasibar, E.; Castejon, F.; Cappa, A.; Eliseev, L. G.; Hidalgo, C.; Krupnik, L. I.; Lopez-Fraguas, A.; Liniers, M.; Lysenko, S. E.; de Pablos, J. L.; Perfilov, S. V.; Sharapov, S. E.; Spong, D. A.; Jimenez, J. A.; Ufimtsev, M. V.; Breizman, B. N.; HIBP Group; the TJ-II Team

    2014-12-01

    Excitation of modes in the Alfvnic frequency range, 30 kHz < fAE < 300 kHz, was observed in hydrogen plasma heated by hydrogen neutral beam injection (NBI) in the TJ-II heliac. Co-field and counter-field NBI were injected, and the components of the poloidal magnetic field were varied one by one and in combinations, in order to investigate the beam-driven modes over an extended range of the rotational transform values, 1.51<\\unicode{7548} (0)<1.67 . Taking advantage of the unique TJ-II capabilities, a dynamic magnetic configuration experiment with \\unicode{7548} (? , t) variation during discharges has shown strong effects on the mode frequency via both vacuum \\unicode{7548} changes and induced net plasma current. A drastic frequency increase from 50 to 250 kHz was observed for some modes when plasma current as low as 2 kA was induced by small (10%) changes in the vertical field. A comprehensive set of diagnostics including a heavy ion beam probe, magnetic probes and a multi-chord bolometer made it possible to identify the spatial spread of the modes and deduce the internal amplitudes of their plasma density and magnetic field perturbations. A simple analytical model for fAE, based on the local Alfvn eigenmode (AE) dispersion relation, was proposed to characterize the observation. It was shown that all the observations, including vacuum iota and plasma current variations, may be fitted by the model, so the linear mode frequency dependence on \\unicode{7548} (plasma current) and one over square root density dependence present the major features of the NBI-induced AEs in TJ-II, and provide the framework for further experiment-to-theory comparison.

  1. Shear-induced inflation of coronal magnetic fields

    NASA Technical Reports Server (NTRS)

    Klimchuk, James A.

    1989-01-01

    Using numerical models of force-free magnetic fields, the shearing of footprints in arcade geometries leading to an inflation of the coronal magnetic field was examined. For each of the shear profiles considered, all of the field lines become elevated compared with the potential field. This includes cases where the shear is concentrated well away from the arcade axis, such that B(sub z), the component of field parallel to the axis, increases outward to produce an inward B(sub z)squared/8 pi magnetic pressure gradient force. These results contrast with an earlier claim, shown to be incorrect, that field lines can sometimes become depressed as a result of shear. It is conjectured that an inflation of the entire field will always result from the shearing of simple arcade configurations. These results have implications for prominence formation, the interplanetary magnetic flux, and possibly also coronal holes.

  2. Magnetic field studies at jupiter by voyager 1: preliminary results.

    PubMed

    Ness, N F; Acuna, M H; Lepping, R P; Burlaga, L F; Behannon, K W; Neubauer, F M

    1979-06-01

    Results obtained by the Goddard Space Flight Center magnetometers on Voyager 1 are described. These results concern the large-scale configuration of the Jovian bow shock and magnetopause, and the magnetic field in both the inner and outer magnetosphere. There is evidence that a magnetic tail extending away from the planet on the nightside is formed by the solar wind-Jovian field interaction. This is much like Earth's magnetosphere but is a new configuration for Jupiter's magnetosphere not previously considered from earlier Pioneer data. We report on the analysis and interpretation of magnetic field perturbations associated with intense electrical currents (approximately 5 x 10(6) amperes) flowing near or in the magnetic flux tube linking Jupiter with the satellite Jo and induced by the relative motion between Io and the corotating Jovian magnetosphere. These currents may be an important source of heating the ionosphere and interior of Io through Joule dissipation. PMID:17800435

  3. Magnetic field studies at Jupiter by Voyager 1: Preliminary results

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Acuna, M. H.; Lepping, R. P.; Burlaga, L. F.; Behannon, K. W.; Neubauer, F. M.

    1979-01-01

    Results obtained by the Goddard Space Flight Center magnetometers on Voyager 1 concerning the large scale configuration of the Jovian bow shock and magnetopause, and the magnetic field in both the inner and outer magnetosphere are highlighted. There is evidence that a magnetic tail extending away from the planet on the nightside is formed by the solar wind-Jovian field interaction. This is much like Earth's magnetosphere but is a new configuration for Jupiter's magnetosphere not previously considered from earlier Pioneer data. Magnetic field perturbations associated with intense electrical currents (approximately 5 x 10 to the 6th power amps) flowing near or in the magnetic flux tube linking Jupiter with the satellite Io and induced by the relative motion between Io and the co-rotating Jovian magnetosphere are analyzed and interpreted. These currents may be an important source of heating the ionosphere and interior of Io through Joule dissipation.

  4. Magnetic field studies at Jupiter by Voyager 1 - Preliminary results

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Acuna, M. H.; Lepping, R. P.; Burlaga, L. F.; Behannon, K. W.; Neubauer, F. M.

    1979-01-01

    Results obtained by the Goddard Space Flight Center magnetometers on Voyager 1 are described. These results concern the large-scale configuration of the Jovian bow shock and magnetopause, and the magnetic field in both the inner and outer magnetosphere. There is evidence that a magnetic tail extending away from the planet on the nightside is formed by the solar wind-Jovian field interaction. This is much like earth's magnetosphere but is a new configuration for Jupiter's magnetosphere not previously considered from earlier Pioneer data. The analysis and interpretation of magnetic field perturbations associated with intense electrical currents (approximately 5 million amperes) flowing near or in the magnetic flux tube linking Jupiter with the satellite Io and induced by the relative motion between Io and the corotating Jovian magnetosphere are reported. These currents may be an important source of heating the ionosphere and interior of Io through Joule dissipation.

  5. A long-lived coronal X-ray arcade. [force-free magnetic field analysis

    NASA Technical Reports Server (NTRS)

    Mcguire, J. P.; Tandberg-Hanssen, E.; Krall, K. R.; Wu, S. T.; Smith, J. B., Jr.; Speich, D. M.

    1977-01-01

    A large, long-lived, soft X-ray emitting arch system observed during a Skylab mission is analyzed. The supposition is that these arches owe their stability to the stable coronal magnetic-field configuration. A global constant alpha force-free magnetic field analysis, is used to describe the arches which stayed in the same approximate position for several solar rotations. A marked resemblance is noted between the theoretical magnetic field configuration and the observed X-ray emmitting feature.

  6. Crystal field and magnetic properties

    NASA Technical Reports Server (NTRS)

    Flood, D. J.

    1977-01-01

    Magnetization and magnetic susceptibility measurements have been made in the temperature range 1.3 to 4.2 K on powdered samples of ErH3. The susceptibility exhibits Curie-Weiss behavior from 4.2 to 2 K, and intercepts the negative temperature axis at theta = 1.05 + or - 0.05 K, indicating that the material is antiferromagnetic. The low field effective moment is 6.77 + or - 0.27 Bohr magnetons per ion. The magnetization exhibits a temperature independent contribution, the slope of which is (5 + or - 1.2) x 10 to the -6th Weber m/kg Tesla. The saturation moment is 3.84 + or - 1 - 0.15 Bohr magnetons per ion. The results can be qualitatively explained by the effects of crystal fields on the magnetic ions. No definitive assignment of a crystal field ground state can be given, nor can a clear choice between cubically or hexagonally symmetric crystal fields be made. For hexagonal symmetry, the first excited state is estimated to be 86 to 100 K above the ground state. For cubic symmetry, the splitting is on the order of 160 to 180 K.

  7. Transverse Magnetic Field Propellant Isolator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2000-01-01

    An alternative high voltage isolator for electric propulsion and ground-based ion source applications has been designed and tested. This design employs a transverse magnetic field that increases the breakdown voltage. The design can greatly enhance the operating range of laboratory isolators used for high voltage applications.

  8. Magnetic properties of TbFe2 particles prepared by magnetic field assisted ball milling

    NASA Astrophysics Data System (ADS)

    Arout Chelvane, J.; Palit, Mithun; Basumatary, Himalay; Pandian, S.

    2013-10-01

    The alloy of TbFe2 was studied by ball milling with and without the presence of external magnetic field. While the structure and powder morphology of the alloy were investigated using scanning electron microscope and X-ray diffraction, the magnetization was investigated using vibrating sample and superconducting quantum interference device magnetometers. The rate of particle reduction with ball milling is comparatively higher in the presence of external magnetic field than without it. Consequently, owing to a large fraction of particles acquiring near single domain configuration under the field assisted milling condition, the coercivity derived from these particles are as high as 6500 Oe than that of particles obtained without the aid of external magnetic field which is around 3850 Oe. The field cooled low temperature magnetization exhibits a large coercivity and skew in the shape of the magnetization curve due to the large anisotropy.

  9. Separation of magnetic field lines

    SciTech Connect

    Boozer, Allen H.

    2012-11-15

    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.

  10. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Krause, Marita

    2015-03-01

    The magnetic field structure in edge-on galaxies observed so far shows a plane-parallel magnetic field component in the disk of the galaxy and an X-shaped field in its halo. The plane-parallel field is thought to be the projected axisymmetric (ASS) disk field as observed in face-on galaxies. Some galaxies addionionally exhibit strong vertical magnetic fields in the halo right above and below the central region of the disk. The mean-field dynamo theory in the disk cannot explain these observed fields without the action of a wind, which also probably plays an important role to keep the vertical scale heights constant in galaxies of different Hubble types and star formation activities, as has been observed in the radio continuum: At ?6 cm the vertical scale heights of the thin disk and the thick disk/halo in a sample of five edge-on galaxies are similar with a mean value of 300 +/- 50 pc for the thin disk and 1.8 +/- 0.2 kpc for the thick disk (a table and references are given in Krause 2011) with our sample including the brightest halo observed so far, NGC 253, with strong star formation, as well as one of the weakest halos, NGC 4565, with weak star formation. If synchrotron emission is the dominant loss process of the relativistic electrons the outer shape of the radio emission should be dumbbell-like as has been observed in several edge-on galaxies like e.g. NGC 253 (Heesen et al. 2009) and NGC 4565. As the synchrotron lifetime t syn at a single frequency is proportional to the total magnetic field strength B t -1.5, a cosmic ray bulk speed (velocity of a galactic wind) can be defined as v CR = h CR /t syn = 2 h z /t syn , where h CR and h z are the scale heights of the cosmic rays and the observed radio emission at this freqnency. Similar observed radio scale heights imply a self regulation mechanism between the galactic wind velocity, the total magnetic field strength and the star formation rate SFR in the disk: v CR ~ B t 1.5 ~ SFR ~ 0.5 (Niklas & Beck 1997).

  11. Magnetic fields in the sun

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1974-01-01

    The observed properties of solar magnetic fields are reviewed, with particular reference to the complexities imposed on the field by motions of the highly conducting gas. Turbulent interactions between gas and field lead to heating or cooling of the gas according to whether the field energy density is less or greater than the maximum kinetic energy density in the convection zone. The field strength above which cooling sets in is 700 gauss. A weak solar dipole field may be primeval, but dynamo action is also important in generating new flux. The dynamo is probably not confined to the convection zone, but extends throughout most of the volume of the sun. Planetary tides appear to play a role in driving the dynamo.

  12. Numerical analyses of trapped field magnet and stable levitation region of HTSC

    SciTech Connect

    Tsuchimoto, M.; Kojima, T.; Waki, H.; Honma, T.

    1995-05-01

    Stable levitation with a permanent magnet and a bulk high {Tc} superconductor (HTSC) is examined numerically by using the critical state model and the frozen field model. Differences between a permanent magnet and a trapped field magnet are first discussed from property of levitation force. Stable levitation region of the HTSC on a ring magnet and on a solenoid coil are calculated with the numerical methods. Obtained results are discussed from difference of the magnetic field configuration.

  13. Fusion proton diagnostic for the C-2 field reversed configuration.

    PubMed

    Magee, R M; Clary, R; Korepanov, S; Smirnov, A; Garate, E; Knapp, K; Tkachev, A

    2014-11-01

    Measurements of the flux of fusion products from high temperature plasmas provide valuable insights into the ion energy distribution, as the fusion reaction rate is a very sensitive function of ion energy. In C-2, where field reversed configuration plasmas are formed by the collision of two compact toroids and partially sustained by high power neutral beam injection [M. Binderbauer et al., Phys. Rev. Lett. 105, 045003 (2010); M. Tuszewski et al., Phys. Rev. Lett. 108, 255008 (2012)], measurements of DD fusion neutron flux are used to diagnose ion temperature and study fast ion confinement and dynamics. In this paper, we will describe the development of a new 3 MeV proton detector that will complement existing neutron detectors. The detector is a large area (50?cm(2)), partially depleted, ion implanted silicon diode operated in a pulse counting regime. While the scintillator-based neutron detectors allow for high time resolution measurements (?100 kHz), they have no spatial or energy resolution. The proton detector will provide 10 cm spatial resolution, allowing us to determine if the axial distribution of fast ions is consistent with classical fast ion theory or whether anomalous scattering mechanisms are active. We will describe in detail the diagnostic design and present initial data from a neutral beam test chamber. PMID:25430264

  14. Fusion proton diagnostic for the C-2 field reversed configuration

    SciTech Connect

    Magee, R. M. Clary, R.; Korepanov, S.; Smirnov, A.; Garate, E.; Knapp, K.; Tkachev, A.

    2014-11-15

    Measurements of the flux of fusion products from high temperature plasmas provide valuable insights into the ion energy distribution, as the fusion reaction rate is a very sensitive function of ion energy. In C-2, where field reversed configuration plasmas are formed by the collision of two compact toroids and partially sustained by high power neutral beam injection [M. Binderbauer et al., Phys. Rev. Lett. 105, 045003 (2010); M. Tuszewski et al., Phys. Rev. Lett. 108, 255008 (2012)], measurements of DD fusion neutron flux are used to diagnose ion temperature and study fast ion confinement and dynamics. In this paper, we will describe the development of a new 3 MeV proton detector that will complement existing neutron detectors. The detector is a large area (50?cm{sup 2}), partially depleted, ion implanted silicon diode operated in a pulse counting regime. While the scintillator-based neutron detectors allow for high time resolution measurements (?100 kHz), they have no spatial or energy resolution. The proton detector will provide 10 cm spatial resolution, allowing us to determine if the axial distribution of fast ions is consistent with classical fast ion theory or whether anomalous scattering mechanisms are active. We will describe in detail the diagnostic design and present initial data from a neutral beam test chamber.

  15. The magnetic field of Jupiter

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.; Ness, N. F.

    1976-01-01

    The paper is concerned mainly with the intrinsic planetary field which dominates the inner magnetosphere up to a distance of 10 to 12 Jovian radii where other phenomena, such as ring currents and diamagnetic effects of trapped charged particles, become significant. The main magnetic field of Jupiter as determined by in-situ observations by Pioner 10 and 11 is found to be relatively more complex than a simple offset tilted dipole. Deviations from a simple dipole geometry lead to distortions of the charged particle L shells and warping of the magnetic equator. Enhanced absorption effects associated with Io and Amalthea are predicted. The results are consistent with the conclusions derived from extensive radio observations at decimetric and decametric wavelengths for the planetary field.

  16. Plasma-gun-assisted field-reversed configuration formation in a conical θ-pinch

    SciTech Connect

    Weber, T. E. Intrator, T. P.; Smith, R. J.

    2015-04-15

    Injection of plasma via an annular array of coaxial plasma guns during the pre-ionization phase of field-reversed configuration (FRC) formation is shown to catalyze the bulk ionization of a neutral gas prefill in the presence of a strong axial magnetic field and change the character of outward flux flow during field-reversal from a convective process to a much slower resistive diffusion process. This approach has been found to significantly improve FRC formation in a conical θ-pinch, resulting in a ∼350% increase in trapped flux at typical operating conditions, an expansion of accessible formation parameter space to lower densities and higher temperatures, and a reduction or elimination of several deleterious effects associated with the pre-ionization phase.

  17. Plasma-gun-assisted field-reversed configuration formation in a conical θ-pinch

    NASA Astrophysics Data System (ADS)

    Weber, T. E.; Intrator, T. P.; Smith, R. J.

    2015-04-01

    Injection of plasma via an annular array of coaxial plasma guns during the pre-ionization phase of field-reversed configuration (FRC) formation is shown to catalyze the bulk ionization of a neutral gas prefill in the presence of a strong axial magnetic field and change the character of outward flux flow during field-reversal from a convective process to a much slower resistive diffusion process. This approach has been found to significantly improve FRC formation in a conical θ-pinch, resulting in a ˜350% increase in trapped flux at typical operating conditions, an expansion of accessible formation parameter space to lower densities and higher temperatures, and a reduction or elimination of several deleterious effects associated with the pre-ionization phase.

  18. Interplanetary Magnetic Field Guiding Relativistic Particles

    NASA Technical Reports Server (NTRS)

    Masson, S.; Demoulin, P.; Dasso, S.; Klein, K. L.

    2011-01-01

    The origin and the propagation of relativistic solar particles (0.5 to few Ge V) in the interplanetary medium remains a debated topic. These relativistic particles, detected at the Earth by neutron monitors have been previously accelerated close to the Sun and are guided by the interplanetary magnetic field (IMF) lines, connecting the acceleration site and the Earth. Usually, the nominal Parker spiral is considered for ensuring the magnetic connection to the Earth. However, in most GLEs the IMF is highly disturbed, and the active regions associated to the GLEs are not always located close to the solar footprint of the nominal Parker spiral. A possible explanation is that relativistic particles are propagating in transient magnetic structures, such as Interplanetary Coronal Mass Ejections (ICMEs). In order to check this interpretation, we studied in detail the interplanetary medium where the particles propagate for 10 GLEs of the last solar cycle. Using the magnetic field and the plasma parameter measurements (ACE/MAG and ACE/SWEPAM), we found widely different IMF configurations. In an independent approach we develop and apply an improved method of the velocity dispersion analysis to energetic protons measured by SoHO/ERNE. We determined the effective path length and the solar release time of protons from these data and also combined them with the neutron monitor data. We found that in most of the GLEs, protons propagate in transient magnetic structures. Moreover, the comparison between the interplanetary magnetic structure and the interplanetary length suggest that the timing of particle arrival at Earth is dominantly determined by the type of IMF in which high energetic particles are propagating. Finally we find that these energetic protons are not significantly scattered during their transport to Earth.

  19. A method to measure specific absorption rate of nanoparticles in colloidal suspension using different configurations of radio-frequency fields

    NASA Astrophysics Data System (ADS)

    Ketharnath, Dhivya; Pande, Rohit; Xie, Leiming; Srinivasan, Srimeenakshi; Godin, Biana; Wosik, Jarek

    2012-08-01

    We report a method for characterization of the efficiency of radio-frequency (rf) heating of nanoparticles (NPs) suspended in an aqueous medium. Measurements were carried out for water suspended 5 nm superparamagnetic iron-oxide NPs with 30 nm dextran matrix for three different configurations of rf electric and magnetic fields. A 30 MHz high-Q resonator was designed to measure samples placed inside a parallel plate capacitor and solenoid coil with or without an rf electric field shield. All components of rf losses were analyzed and rf electric and magnetic field induced heating of NPs and the dispersion medium was determined and discussed.

  20. Oxide superconductors under magnetic field

    NASA Technical Reports Server (NTRS)

    Kitazawa, K.

    1991-01-01

    One of the current most serious problems for the oxide superconductors from the standpoint of practical application is the various novel features derived mainly from their extremely short coherence. In particular, the coherence length so far observed in the cuprate superconductors is in the range of 0.1 nm perpendicular to the CuO2 plane. This seems to be creating most of the difficulties in the device fabrication and in the performance under the magnetic field. Some of the superconducting properties under the magnetic field will be discussed in terms of the short coherence length. A model will be presented based on the gradual strengthening of the pinning force with decrease in temperature and the weak coupling at the grain boundaries. Secondly, the broadening of the superconducting transition under the magnetic field is discussed. This is observed significantly only when the field is applied perpendicular to the basal plane and the relative orientation of the current to the field is insignificant in determining the extent of broadening. Besides, the change in the strength of the pinning force does not affect the width of the broadening. From these observations discussions will be made on a model based on the giant fluctuation. Based on this model, it is predicted that the coherence length along the c-axis will be the single most important material parameter to determine the performance of the superconductor under a strong magnetic field. It seems that BYCO is superior in this regard to Bi- or Tl-systems as far as the performance at 77 K is considered, although another material with the coherence length slightly longer along the c-axis is still highly desired.

  1. Oxide superconductors under magnetic field

    NASA Technical Reports Server (NTRS)

    Kitazawa, K.

    1990-01-01

    One of the current most serious problems for the oxide superconductors from the standpoint of practical application is the various novel features derived mainly from their extremely short coherence. In particular, the coherence length so far observed in the cuprate superconductors is in the range of 0.1 nm perpendicular to the CuO2 plane. This seems to be creating most of the difficulties in the device fabrication and in the performance under the magnetic field. Some of the superconducting properties under the magnetic field will be discussed in terms of the short coherence length. A model will be presented based on the gradual strengthening of the pinning force with decrease in temperature and the weak coupling at the grain boundaries. Secondly, the broadening of the superconducting transition under the magnetic field is discussed. This is observed significantly only when the field is applied perpendicular to the basal plane and the relative orientation of the current to the field is insignificant in determining the extent of the broadening. Besides, the change in the strength of the pinning force does not affect the width of the broadening. From these observations discussions will be made on a model based on the giant fluctuation. Based on this model, it is predicted that the coherence length along the c-axis will be the single most important material parameter to determine the performance of the superconductor under a strong magnetic field. It seems that BYCO is superior in this regard to Bi- or Tl-systems as far as the performance at 77 K is considered, although another material with the coherence length slightly longer along the c-axis is still highly desired.

  2. Erbium doped optical fiber lasers for magnetic field sensing

    NASA Astrophysics Data System (ADS)

    Nascimento, I. M.; Baptista, J. M.; Jorge, P. A. S.; Cruz, J. L.; Andrs, M. V.

    2015-09-01

    In this work two erbium doped optical fiber laser configurations for magnetic field measurement are implemented and compared. The first laser is set-up in a loop configuration and requires only a single FBG (Fiber Bragg Grating), acting as mirror. A second laser employs a simpler linear cavity configuration but requires two FBGs with spectral overlap to form the laser cavity. A bulk magnetostrictive material made of Terfenol-D is attached to the laser FBGs enabling modulation of its operation wavelength by the magnetic field. Moreover, a passive interferometer was developed to demodulate the AC magnetic field information where the corresponding demodulation algorithms were software based. Both configurations are tested and compared with the results showing different sensitivities and resolutions. Better performance was accomplished with the double FBGs linear cavity configuration with a resolution of 0.05 mTRMS in the range of 8 to 16 mTRMS. For the same range the loop configuration attained a resolution of 0.48 mTRMS.

  3. Force-free magnetic fields - Generating functions and footpoint displacements

    NASA Technical Reports Server (NTRS)

    Wolfson, Richard; Verma, Ritu

    1991-01-01

    This paper presents analytic and numerical calculations that explore equilibrium sequences of bipolar force-free magnetic fields in relation to displacments of their magnetic footpoints. It is shown that the appearance of magnetic islands - sometimes interpreted as marking the loss of equilibrium in models of the solar atmosphere - is likely associated only with physically unrealistic footpoint displacements such as infinite separation or 'tearing' of the model photosphere. The work suggests that the loss of equilibrium in bipolar configurations, sometimes proposed as a mechanism for eruptive solar events, probably requires either fully three-dimensional field configurations or nonzero plasma pressure. The results apply only to fields that are strictly bipolar, and do not rule out equilibrium loss in more complex structures such as quadrupolar fields.

  4. Field-aligned accelerations by plasma shocks propagating through interstellar magnetic fields

    SciTech Connect

    Takeuchi, Satoshi

    2012-07-15

    A kinetic model of particle acceleration by plasma shocks is analyzed theoretically and with numerical calculations. The shocks are propagating through weakly magnetized background plasmas, namely interstellar magnetic fields (IMFs). Particles located at the shock front are accelerated parallel to the magnetic field of the shock; this is defined as the field-aligned acceleration (FAA). The cross angle between IMF and the magnetic field of the shock plays an important role in creating the magnetic neutral sheet at the shock front. A test particle trapped by the neutral sheet obtains enormous energy due to the FAA. A reasonable formula for the highest energy gain is derived from theoretical analysis of the relativistic equations of motion. A possible configuration of the electric and magnetic fields in supernova remnants is also proposed by way of example.

  5. Field-aligned accelerations by plasma shocks propagating through interstellar magnetic fields

    NASA Astrophysics Data System (ADS)

    Takeuchi, Satoshi

    2012-07-01

    A kinetic model of particle acceleration by plasma shocks is analyzed theoretically and with numerical calculations. The shocks are propagating through weakly magnetized background plasmas, namely interstellar magnetic fields (IMFs). Particles located at the shock front are accelerated parallel to the magnetic field of the shock; this is defined as the field-aligned acceleration (FAA). The cross angle between IMF and the magnetic field of the shock plays an important role in creating the magnetic neutral sheet at the shock front. A test particle trapped by the neutral sheet obtains enormous energy due to the FAA. A reasonable formula for the highest energy gain is derived from theoretical analysis of the relativistic equations of motion. A possible configuration of the electric and magnetic fields in supernova remnants is also proposed by way of example.

  6. A high-field superferric NMR magnet.

    PubMed

    Huson, F R; Bryan, R N; MacKay, W W; Herrick, R C; Colvin, J; Ford, J J; Pissanetzky, S; Plishker, G A; Rocha, R; Schmidt, W

    1993-01-01

    Strong, extensive magnetic fringe fields are a significant problem with magnetic resonance imaging magnets. This is particularly acute with 4-T, whole-body research magnets. To date this problem has been addressed by restricting an extensive zone around the unshielded magnet or by placing external unsaturated iron shielding around the magnet. This paper describes a solution to this problem which uses superconducting coils closely integrated with fully saturated iron elements. A 4-T, 30-cm-bore prototype, based on this design principle, was built and tested. The 5 G fringe field is contained within 1 meter of the magnet bore along the z axis. Homogeneity of the raw magnetic field is 10 ppm over 30% of the magnet's diameter after passive shimming. Compared with an unshielded magnet, 20% less superconductor is required to generate the magnetic field. Images and spectra are presented to demonstrate the magnet's viability for magnetic resonance imaging and spectroscopy. PMID:8419740

  7. A model for inferring transport rates from observed confinement times in field-reversed configurations

    NASA Astrophysics Data System (ADS)

    Steinhauer, Loren C.; Milroy, Richard D.; Slough, John T.

    1985-03-01

    A one-dimensional transport model is developed to simulate the confinement of plasma and magnetic flux in a field-reversed configuration. Given the resistivity, the confinement times can be calculated. Approximate expressions are found which yield the magnitude and gross profile of the resistivity if the confinement times are known. These results are applied to experimental data from experiments, primarily TRX-1, to uncover trends in the transport properties. Several important conclusions emerge. The transport depends profoundly, and inexplicably, on the plasma formation mode. The inferred transport differs in several ways from the predictions of local lower-hybrid-drift turbulence theory. Finally, the gross resistivity exhibits an unusual trend with xs (separatrix radius rs divided by the conducting wall radius rc ), and is peaked near the magnetic axis for certain predictable conditions.

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

    SciTech Connect

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

    2007-06-26

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

  9. Switchable magnetic bottles and field gradients for particle traps

    NASA Astrophysics Data System (ADS)

    Vogel, Manuel; Birkl, Gerhard; Quint, Wolfgang; von Lindenfels, David; Wiesel, Marco

    2014-01-01

    Versatile methods for the manipulation of individual quantum systems, such as confined particles, have become central elements in current developments in precision spectroscopy, frequency standards, quantum information processing, quantum simulation, and alike. For atomic and some subatomic particles, both neutral and charged, a precise control of magnetic fields is essential. In this paper, we discuss possibilities for the creation of specific magnetic field configurations which find application in these areas. In particular, we pursue the idea of a magnetic bottle which can be switched on and off by transition between the normal and the superconducting phase of a suitable material in cryogenic environments, for example, in trap experiments in moderate magnetic fields. Methods for a fine-tuning of the magnetic field and its linear and quadratic components in a trap are presented together with possible applications.

  10. The HMI Magnetic Field Pipeline

    NASA Astrophysics Data System (ADS)

    Hoeksema, Jon Todd; Liu, Y.; Schou, J.; Scherrer, P.; HMI Science Team

    2009-05-01

    The Helioseismic and Magnetic Imager (HMI) will provide frequent full-disk magnetic field data after launch of the Solar Dynamics Observatory (SDO), currently scheduled for fall 2009. 16 megapixel line-of-sight magnetograms (Blos) will be recorded every 45 seconds. A full set of polarized filtergrams needed to determine the vector magnetic field requires 90 seconds. Quick-look data will be available within a few minutes of observation. Quick-look space weather and browse products must have identified users, and the list currently includes full disk magnetograms, feature identification and movies, 12-minute disambiguated vector fields in active region patches, time evolution of AR indices, synoptic synchronic frames, potential and MHD model results, and 1 AU predictions. A more complete set of definitive science data products will be offered about a day later and come in three types. "Pipeline products, such as full disk vector magnetograms, will be computed for all data on an appropriate cadence. A larger menu of "On Demand products, such as Non-Linear Force Free Field snapshots of an evolving active region, will be produced whenever a user wants them. Less commonly needed "On Request products that require significant project resources, such as a high resolution MHD simulation of the global corona, will be created subject to availability of resources. Further information can be found at the SDO Joint Science Operations Center web page, jsoc.stanford.edu

  11. Magnetic fields and coronal heating

    SciTech Connect

    Golub, L.; Maxson, C.; Rosner, R.; Serio, S.; Vaiana, G.S.

    1980-05-15

    General considerations concerning the scaling properties of magnetic-field--related colonal heating mechanisms are used to build a two-parameter model for the heating of closed coronal regions. The model perdicts the way in which coronal temperature and electron density are related to photospheric magnetic field strength and the size of the region, using the additional constraint provided by the scaling law of rosner, tucker, and Viaiana. The model successfully duplicates the observed scaling of total thermal energy content with total longitudinal flux; it also predict a relation between the coronal energy density (or pressure) and the longitudinal field strength modified by the region scale size. The observational data yield a similar relation, pproportional/sup 1.6/. A parameter of the theory, which is evaluated by fitting to the data, is the product ..cap alpha..upsilon/sub phi/, where ..cap alpha.. is the ratio of azimuthal to longitudinal magnetic field and upsilon/sub phi/ is the effective twisting velocity of the loop footpoints, which supplies the energy for coronal heating.

  12. Dependence of effective internal field of congruent lithium niobate on its domain configuration and stability

    SciTech Connect

    Das, Ranjit E-mail: souvik2cat@gmail.com Ghosh, Souvik E-mail: souvik2cat@gmail.com Chakraborty, Rajib E-mail: souvik2cat@gmail.com

    2014-06-28

    Congruent lithium niobate is characterized by its internal field, which arises due to defect clusters within the crystal. Here, it is shown experimentally that this internal field is a function of the molecular configuration in a particular domain and also on the stability of that particular configuration. The measurements of internal field are done using interferometric technique, while the variation of domain configuration is brought about by room temperature high voltage electric field poling.

  13. Microstability theory for the field reversed configuration. Final report

    SciTech Connect

    Krall, N.A.

    1997-11-05

    This report summarizes the work done in the last contract period. Previous work has been described in Annual Performance Reports. The work carried on under this Research Grant and not included in previous progress and annual reports includes two distinct items. One work is a study of the nonlocal high beta microstability of the FRC (Field Reversed Configuration), which they began sometime ago. This study identified the limiting beta (=4{pi}nT/B{sup 2}) for the mode to remain unstable. The study found that as beta increases, the wavenumbers (k{sub y}, K{sub z}) for maximum growth changes, so that the limiting beta is not the one found by fixing (k{sub y}, K{sub z}) and increasing beta. It also appears that the criterion for nonlocal terms to influence the result, as beta increases, is substantially weaker than might have been thought. The authors identify the parameter that determines this effect. This study is presented as Appendix 1 of this report. The second study is of the effect of collisions on the lower hybrid drift instability. The result is that the effect of collisions is substantially more important than might have been expected. These two studies are in different stages of completion. The second is in fact complete, and could be published virtually as is, although it would benefit from a small amount of numerical analysis. The first study is far richer than the second, in that it includes a variety of regimes and effects. The formulation presented in it could e used as the basis for a series of papers, although in its present stage it is not ready for publication. It is unfortunate, but the level of the research Grant, and its untimely end, did not permit further progress on that study.

  14. Toroidal plasma reactor with low external magnetic field

    NASA Astrophysics Data System (ADS)

    Beklemishev, A. D.; Khayrutdinov, R. R.; Petviashvili, V. I.; Tajima, T.; Gordin, V. A.; Tajima, T.

    1991-01-01

    A toroidal pinch configuration with safety factor q less than 0.5 decreasing from the center to periphery without field reversal is proposed. This is capable of containing high pressure plasma with only small toroidal external magnetic field. Sufficient conditions for magnetohydrodynamic stability are fulfilled in this configuration. The stability is studied by constructing the Lyapunov functional and investigating its extrema both analytically and numerically. Comparison of the Lyapunov stability conditions with the conventional linear theory is carried out. Stable configurations are found with average (beta) near 15 percent, with magnetic field associated mainly with plasma current. The (beta) value calculated with the external magnetic field can be over 100 percent. Fast charged particles produced by fusion reactions are asymmetrically confined by the poloidal magnetic field (and due to the lack of strong toroidal field). They thus generate a current in the noncentral part of plasma to reinforce the poloidal field. This current drive can sustain the monotonic decrease of q with radius.

  15. Investigation of Magnetic Field Topology in Auto-oscillating Discharge

    NASA Astrophysics Data System (ADS)

    Popov, Vyacheslav; Gutorov, Konstantin; Sorokin, Ivan

    The magnetic field structure measurements are necessary for understanding of wave propagation in plasma of the auto-oscillating discharge in the open adiabatic trap PR-2. Measurements were made by the developed system for automatic positioning of magnetic probes placed inside the PR-2 vacuum chamber. All magnetic probes were pre-calibrated using Helmholtz coil. Four different circuit configurations were used to excite oscillations in wide frequency range. Observed frequencies of plasma oscillations using magnetic probes correspond to the circuit resonant frequencies.

  16. High Steady Magnetic Field Processing of Functional Magnetic Materials

    NASA Astrophysics Data System (ADS)

    Rivoirard, Sophie

    2013-07-01

    The materials science community has been enriched for some decades now by the "magneto-science" approach, which consists of applying a magnetic field during material processing. The development of anisotropic properties by applying a steady magnetic field is now a well-established effect in the material processing of magnetic substances, which benefits from the unidirectional and static nature of the field delivered by superconducting magnets. Among other effects, magnetic anisotropy in functional magnetic materials, which arises from the alignment of magnetic moments under external field, can be developed at various structural scales. Magnetic ordering, magnetic patterning, and texturation are at the origin of this anisotropy development. Texture is developed in materials from magnetic orientation due to magnetic forces and torques or from stored energy. In metals and alloys, for instance, this effect can occur either in their liquid state or during solid-state thermomagnetic treatments and can thus impact significantly the material functional magnetic properties. Today's improved superconducting magnet technology allows higher field intensities to be delivered more easily (1 T up to several tens of Teslas) and enables researchers to gather evidence on magnetic field effects that were formerly thought to be negligible. The magneto-thermodynamic effect is one of them and involves the magnetization energy as an additional parameter to tailor microstructures. Control of functional properties can thus result from magnetic monitoring of the phase transformation, and kinetics can be impacted by the magnetic energy contribution.

  17. Note: Manipulation of supersonic atomic beams with static magnetic fields.

    PubMed

    Gardner, Jamie; Castillo-Garza, Rodrigo; Raizen, Mark G

    2013-09-01

    The inhomogeneous magnetic field of a permanent-magnet planar Halbach array is used to either deflect or to specularly reflect a supersonic beam of neutral atoms. Metastable neon and helium beams are tested to experimentally evaluate the performance of this array in a range of configurations. Results are compared with numerical simulations and the device is presented as a high precision tool for the manipulation of neutral atom beams. PMID:24028135

  18. Note: Manipulation of supersonic atomic beams with static magnetic fields

    NASA Astrophysics Data System (ADS)

    Gardner, Jamie; Castillo-Garza, Rodrigo; Raizen, Mark G.

    2013-09-01

    The inhomogeneous magnetic field of a permanent-magnet planar Halbach array is used to either deflect or to specularly reflect a supersonic beam of neutral atoms. Metastable neon and helium beams are tested to experimentally evaluate the performance of this array in a range of configurations. Results are compared with numerical simulations and the device is presented as a high precision tool for the manipulation of neutral atom beams.

  19. The origin of magnetic fields in hot stars

    NASA Astrophysics Data System (ADS)

    Neiner, Coralie; Mathis, Stéphane; Alecian, Evelyne; Emeriau, Constance; Grunhut, Jason; BinaMIcS; MiMeS Collaborations

    2015-10-01

    Observations of stable mainly dipolar magnetic fields at the surface of ~7% of single hot stars indicate that these fields are of fossil origin, i.e. they descend from the seed field in the molecular clouds from which the stars were formed. The recent results confirm this theory. First, theoretical work and numerical simulations confirm that the properties of the observed fields correspond to those expected from fossil fields. They also showed that rapid rotation does not modify the surface dipolar magnetic configurations, but hinders the stability of fossil fields. This explains the lack of correlation between the magnetic field properties and stellar properties in massive stars. It may also explain the lack of detections of magnetic fields in Be stars, which rotate close to their break-up velocity. In addition, observations by the BinaMIcS collaboration of hot stars in binary systems show that the fraction of those hosting detectable magnetic fields is much smaller than for single hot stars. This could be related to results obtained in simulations of massive star formation, which show that the stronger the magnetic field in the original molecular cloud, the more difficult it is to fragment massive cores to form several stars. Therefore, more and more arguments support the fossil field theory.

  20. Field quality aspects of CBA superconducting magnets

    SciTech Connect

    Kahn, S.; Engelmann, R.; Fernow, R.; Greene, A.F.; Herrera, J.; Kirk, H.; Skaritka, J.; Wanderer, P.; Willen, E.

    1983-01-01

    A series of superconducting dipole magnets for the BNL Colliding Beam Accelerator which were manufactured to have the proper field quality characteristics has been tested. This report presents the analysis of the field harmonics of these magnets.

  1. Anisotropic Magnetism in Field-Structured Composites

    SciTech Connect

    Anderson, Robert A.; Martin, James E.; Odinek, Judy; Venturini, Eugene

    1999-06-24

    Magnetic field-structured-composites (FSCs) are made by structuring magnetic particle suspensions in uniaxial or biaxial (e.g. rotating) magnetic fields, while polymerizing the suspending resin. A uniaxial field produces chain-like particle structures, and a biaxial field produces sheet-like particle structures. In either case, these anisotropic structures affect the measured magnetic hysteresis loops, with the magnetic remanence and susceptibility increased significantly along the axis of the structuring field, and decreased slightly orthogonal to the structuring field, relative to the unstructured particle composite. The coercivity is essentially unaffected by structuring. We present data for FSCs of magnetically soft particles, and demonstrate that the altered magnetism can be accounted for by considering the large local fields that occur in FSCs. FSCS of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the local field effects in combination with the large crystalline anisotropy of this material.

  2. Measurements of Solar Vector Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J. (Editor)

    1985-01-01

    Various aspects of the measurement of solar magnetic fields are presented. The four major subdivisions of the study are: (1) theoretical understanding of solar vector magnetic fields; (3) techniques for interpretation of observational data; and (4) techniques for data display.

  3. Magnetic holes in the solar wind. [(interplanetary magnetic fields)

    NASA Technical Reports Server (NTRS)

    Turner, J. M.; Burlaga, L. F.; Ness, N. F.; Lemaire, J. F.

    1976-01-01

    An analysis is presented of high resolution interplanetary magnetic field measurements from the magnetometer on Explorer 43 which showed that low magnetic field intensities in the solar wind at 1 AU occur as distinct depressions or 'holes'. These magnetic holes are new kinetic-scale phenomena, having a characteristic dimension on the order of 20,000 km. They occurred at a rate of 1.5/day in the 18-day time span (March 18 to April 6, 1971) that was analyzed. Most of the magnetic holes are characterized by both a depression in the absolute value of the magnetic field, and a change in the magnetic field direction; some of these are possibly the result of magnetic merging. However, in other cases the magnetic field direction does not change; such holes are not due to magnetic merging, but might be a diamagnetic effect due to localized plasma inhomogeneities.

  4. Experimental profile evolution of a high-density field-reversed configuration

    SciTech Connect

    Ruden, E. L.; Zhang, Shouyin; Intrator, T. P.; Wurden, G. A.

    2006-12-15

    A field-reversed configuration (FRC) gains angular momentum over time, eventually resulting in an n=2 rotational instability (invariant under rotation by {pi}) terminating confinement. To study this, a laser interferometer probes the time history of line integrated plasma density along eight chords of the high-density ({approx}10{sup 17} cm{sup -3}) field-reversed configuration experiment with a liner. Abel and tomographic inversions provide density profiles during the FRC's azimuthally symmetric phase, and over a period when the rotational mode has saturated and rotates with a roughly fixed profile, respectively. During the latter part of the symmetric phase, the FRC approximates a magnetohydrodynamic (MHD) equilibrium, allowing the axial magnetic-field profile to be calculated from pressure balance. Basic FRC properties such as temperature and poloidal flux are then inferred. The subsequent two-dimensional n=2 density profiles provide angular momentum information needed to set bounds on prior values of the stability relevant parameter {alpha} (rotational to ion diamagnetic drift frequency ratio), in addition to a view of plasma kinematics useful for benchmarking plasma models of higher order than MHD.

  5. Fast Global Imaging of the C-2 Field-Reversed Configuration and Divertor Plasmas

    NASA Astrophysics Data System (ADS)

    Granstedt, Erik; Roquemore, A. L.; Longman, A.; Hayashi, R.; Yankoski, E.; TAE Team

    2014-10-01

    Two high-speed, filtered cameras have been used to view the dynamics of the C-2. Field-Reversed Configuration (FRC) and divertor plasmas. The first used a re-entrant viewport to achieve a global, quasi-axial view of the FRC plasma in order to examine macroscopic plasma evolution, rotation, and non-axisymmetric perturbations. This instrument consisted of a Phantom v7.3 camera coupled to imaging optics via a 15-ft, 1000 800 pixel coherent fiber bundle. A filter wheel was set between shots to view edge-dominated emission from neutral D, C III, or Li I-II, or core-dominated emission from O III-V. Perturbations rotating in the ion diamagnetic direction were observed both during the FRC and after the transition to an open field-line plasma. The divertor instrument consisted of a Phantom v5.2 camera with D? filter and was used to examine divertor neutral density under various gas puffing, magnetic field, and electrode biasing configurations. Both instruments were photometrically calibrated to measure absolute emissivity in order to obtain estimates of neutral and impurity density.

  6. Rotating copper plasmoid in external magnetic field

    SciTech Connect

    Pandey, Pramod K.; Thareja, Raj K.

    2013-02-15

    Effect of nonuniform magnetic field on the expanding copper plasmoid in helium and argon gases using optical emission spectroscopy and fast imaging is presented. We report a peculiar oscillatory rotation of plasmoid in magnetic field and argon ambient. The temporal variation and appearance of the dip in the electron temperature show a direct evidence of the threading and expulsion of the magnetic field lines from the plasmoid. Rayleigh Taylor instability produced at the interface separating magnetic field and plasma is discussed.

  7. Minireview: Biological effects of magnetic fields

    SciTech Connect

    Villa, M.; Mustarelli, P. ); Caprotti, M. )

    1991-01-01

    The literature about the biological effects of magnetic fields is reviewed. The authors begin by discussing the weak and/or time variable fields, responsible for subtle changes in the circadian rhythms of superior animals, which are believed to be induced by same sort of resonant mechanism. The safety issues related with the strong magnetic fields and gradients generated by clinical NMR magnets are then considered. The last portion summarizes the debate about the biological effects of strong and uniform magnetic fields.

  8. Non-Abelian fields in AdS4 spacetime: Axially symmetric, composite configurations

    NASA Astrophysics Data System (ADS)

    Kichakova, Olga; Kunz, Jutta; Radu, Eugen; Shnir, Yasha

    2014-12-01

    We construct new finite-energy regular solutions in Einstein-Yang-Mills-SU(2) theory. They are static, axially symmetric and approach at infinity the anti-de Sitter spacetime background. These configurations are characterized by a pair of integers (m ,n ), where m is related to the polar angle and n to the azimuthal angle, being related to the known flat-space monopole-antimonopole chains and vortex rings. Generically, they describe composite configurations with several individual components, possessing a nonzero magnetic charge, even in the absence of a Higgs field. Such Yang-Mills configurations exist already in the probe limit, with the AdS geometry supplying the attractive force needed to balance the repulsive force of Yang-Mills gauge interactions. The gravitating solutions are constructed by numerically solving the elliptic Einstein-DeTurck-Yang-Mills equations. The variation of the gravitational coupling constant ? reveals the existence of two branches of gravitating solutions which bifurcate at some critical value of ? . The lower-energy branch connects to the solutions in the global AdS spacetime, while the upper branch is linked to the generalized Bartnik-McKinnon solutions in asymptotically flat spacetime. Also, a spherically symmetric, closed-form solution is found as a perturbation around the globally anti-de Sitter vacuum state.

  9. Penetration of plasma across a magnetic field

    NASA Astrophysics Data System (ADS)

    Plechaty, C.; Presura, R.; Wright, S.; Neff, S.; Haboub, A.

    2009-08-01

    Experiments were performed at the Nevada Terawatt Facility to investigate the plasma penetration across an externally applied magnetic field. In experiment, a short-pulse laser ablates a polyethylene laser target, producing a plasma which interacts with an external magnetic field. The mechanism which allows the plasma to penetrate the applied magnetic field in experiment will be discussed.

  10. Superposition of DC magnetic fields by cascading multiple magnets in magnetic loops

    NASA Astrophysics Data System (ADS)

    Sun, Fei; He, Sailing

    2015-09-01

    A novel method that can effectively collect the DC magnetic field produced by multiple separated magnets is proposed. With the proposed idea of a magnetic loop, the DC magnetic field produced by these separated magnets can be effectively superimposed together. The separated magnets can be cascaded in series or in parallel. A novel nested magnetic loop is also proposed to achieve a higher DC magnetic field in the common air region without increasing the DC magnetic field in each magnetic loop. The magnetic loop can be made by a magnetic hose, which is designed by transformation optics and can be realized by the combination of super-conductors and ferromagnetic materials.

  11. Cancellation of the ion deflection due to electron-suppression magnetic field in a negative-ion accelerator

    SciTech Connect

    Chitarin, G.; Agostinetti, P.; Aprile, D.; Marconato, N.; Veltri, P.

    2014-02-15

    A new magnetic configuration is proposed for the suppression of co-extracted electrons in a negative-ion accelerator. This configuration is produced by an arrangement of permanent magnets embedded in one accelerator grid and creates an asymmetric local magnetic field on the upstream and downstream sides of this grid. Thanks to the “concentration” of the magnetic field on the upstream side of the grid, the resulting deflection of the ions due to magnetic field can be “intrinsically” cancelled by calibrating the configuration of permanent magnets. At the same time, the suppression of co-extracted electrons can be improved.

  12. Binary stellar winds. [flow and magnetic field geometry

    NASA Technical Reports Server (NTRS)

    Siscoe, G. L.; Heinemann, M. A.

    1974-01-01

    Stellar winds from a binary star pair will interact with each other along a contact discontinuity. We discuss qualitatively the geometry of the flow and field resulting from this interaction in the simplest case where the stars and winds are identical. We consider the shape of the critical surface (defined as the surface where the flow speed is equal to the sound speed) as a function of stellar separation and the role of shock waves in the flow field. The effect of stellar spin and magnetic sectors on the field configuration is given. The relative roles of mass loss and magnetic torque in the evolution of orbital parameters is discussed.

  13. Binary stellar winds. [flow and magnetic field interactions

    NASA Technical Reports Server (NTRS)

    Siscoe, G. L.; Heinemann, M. A.

    1974-01-01

    Stellar winds from a binary star will interact with each other along a contact discontinuity. We discuss qualitatively the geometry of the flow and field resulting from this interaction in the simplest case where the stars and winds are identical. We consider the shape of the critical surface (defined as the surface where the flow speed is equal to the sound speed) as a function of stellar separation and the role of shock waves in the flow field. The effect of stellar spin and magnetic sectors on the field configuration is given. The relative roles of mass loss and magnetic torque in the evolution of orbital parameters are discussed.

  14. Magnetic Fields in the Star Forming Region S88B

    NASA Astrophysics Data System (ADS)

    Sarma, A. P.; Brogan, C. L.; Bourke, T.; Troland, T. H.; Crutcher, R. M.; Myers, P. C.

    2004-12-01

    We present VLA OH Zeeman observations of the star forming region S88B at 1665 and 1667 MHz. We have combined data from the B and C configurations of the VLA, in order to obtain a high resolution map of the magnetic field (4 arcsec resolution). The line-of-sight field is observed to increase from about 100 microG in the southwest to about 300 microG in the northeast. We shall use our results to examine the importance of the magnetic field in providing support to the cloud.

  15. Convective Flow Induced by Localized Traveling Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    An axisymmetric traveling magnetic field induces a meridional base flow in a cylindrical zone of an electrically conducting liquid. This remotely induced flow can be conveniently controlled, in magnitude and direction, and can have benefits for crystal growth applications. In particular, it can be used to offset natural convection. For long vertical cylinders, non-uniform and localized in the propagating direction, magnetic fields are required for this purpose. Here we investigate a particular form of this field, namely that induced by a set of a few electric current coils. An order of magnitude reduction of buoyancy convection is theoretically demonstrated for a vertical Bridgman crystal growth configuration.

  16. Interplanetary magnetic field data book

    NASA Technical Reports Server (NTRS)

    King, J. H.

    1975-01-01

    An interplanetary magnetic field (IMF) data set is presented that is uniform with respect to inclusion of cislunar IMF data only, and which has as complete time coverage as presently possible over a full solar cycle. Macroscale phenomena in the interplanetary medium (sector structure, heliolatitude variations, solar cycle variations, etc.) and other phenomena (e.g., ground level cosmic-ray events) for which knowledge of the IMF with hourly resolution is necessary, are discussed. Listings and plots of cislunar hourly averaged IMP parameters over the period November 27, 1963, to May 17, 1974, are presented along with discussion of the mutual consistency of the IMF data used herein. The magnetic tape from which the plots and listings were generated, which is available from the National Space Science Data Center (NSSDC), is also discussed.

  17. The Giotto magnetic field investigation

    NASA Technical Reports Server (NTRS)

    Neubauer, F. M.; Musmann, G.; Acuna, M. H.; Burlaga, L. F.; Ness, N. F.; Mariani, F.; Wallis, M.; Ungstrup, E.; Schmidt, H.

    1983-01-01

    The Giotto spacecraft will carry sensors for investigating the interplanetary magnetic field while en route and the interaction between the solar wind magnetoplasma and Halley's Comet neutral gas outflow during close approach. Giotto will carry an outboard biaxial fluxgate system and inboard electronics. The instrumentation draws 1.2 kW and weighs 1.31 kg. Sampling rates will be 28/sec during close encounter, covering selectable ranges from 16 nT to 65,535 nT. In-flight calibration techniques are under development to ensure magnetic cleanliness will be obtained. Measurements are also planned of the inbound bow shock, the magnetosheath and the cometary ionopause. The data will be collected as close as 1000 km from the comet surface.

  18. Bats respond to very weak magnetic fields.

    PubMed

    Tian, Lan-Xiang; Pan, Yong-Xin; Metzner, Walter; Zhang, Jin-Shuo; Zhang, Bing-Fang

    2015-01-01

    How animals, including mammals, can respond to and utilize the direction and intensity of the Earth's magnetic field for orientation and navigation is contentious. In this study, we experimentally tested whether the Chinese Noctule, Nyctalus plancyi (Vespertilionidae) can sense magnetic field strengths that were even lower than those of the present-day geomagnetic field. Such field strengths occurred during geomagnetic excursions or polarity reversals and thus may have played an important role in the evolution of a magnetic sense. We found that in a present-day local geomagnetic field, the bats showed a clear preference for positioning themselves at the magnetic north. As the field intensity decreased to only 1/5th of the natural intensity (i.e., 10 ?T; the lowest field strength tested here), the bats still responded by positioning themselves at the magnetic north. When the field polarity was artificially reversed, the bats still preferred the new magnetic north, even at the lowest field strength tested (10 ?T), despite the fact that the artificial field orientation was opposite to the natural geomagnetic field (P<0.05). Hence, N. plancyi is able to detect the direction of a magnetic field even at 1/5th of the present-day field strength. This high sensitivity to magnetic fields may explain how magnetic orientation could have evolved in bats even as the Earth's magnetic field strength varied and the polarity reversed tens of times over the past fifty million years. PMID:25922944

  19. Revisiting quark stars under the influence of strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Menezes, Debora

    2013-03-01

    Quark matter at finite temperature and subject to strong magnetic fields is possibly present in the early stages of heavy ion collisions and in the interior of protoneutron stars. We use the mean field approximation to investigate this type of quark matter described by the Nambu-Jona-Lasinio model. The energy per baryon of magnetized quark matter becomes more bound than nuclear matter made of iron nuclei, for magnetic fields around 1019 G. When the su(3) NJL model is applied to stellar matter, the maximum mass configurations are always above 1.45 solar masses and may be as high as 1.9 solar masses for a central magnetic field of 1018 G. These numbers are within the masses of observed neutron stars but exclude the recently measured star with 1.97 solar mass.

  20. Cold and ultracold Rydberg atoms in strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Pohl, T.; Sadeghpour, H. R.; Schmelcher, P.

    2009-12-01

    Cold Rydberg atoms exposed to strong magnetic fields possess unique properties which open the pathway for an intriguing many-body dynamics taking place in Rydberg gases, consisting of either matter or anti-matter systems. We review both the foundations and recent developments of the field in the cold and ultracold regime where trapping and cooling of Rydberg atoms have become possible. Exotic states of moving Rydberg atoms, such as giant dipole states, are discussed in detail, including their formation mechanisms in a strongly magnetized cold plasma. Inhomogeneous field configurations influence the electronic structure of Rydberg atoms, and we describe the utility of corresponding effects for achieving tightly trapped ultracold Rydberg atoms. We review recent work on large, extended cold Rydberg gases in magnetic fields and their formation in strongly magnetized ultracold plasmas through collisional recombination. Implications of these results for current antihydrogen production experiments are pointed out, and techniques for the trapping and cooling of such atoms are investigated.

  1. The resistance peak of helicon plasmas at low magnetic fields

    SciTech Connect

    Cho, Suwon

    2006-03-15

    The dispersion characteristics of the radial eigenmodes and resistive loading of helicon plasmas are studied to explain the occurrence of the density peak at low magnetic fields. The plasma resistance is usually found to be large for the eigenmodes near the magnetic field where the fast and slow waves are coupled and can be peaked at low magnetic fields depending on the antenna configuration. It is explained how reflection of the waves at an axial end causes the resistance peak at low magnetic fields for a single loop antenna and the Nagoya type III or helical antenna itself can give rise to the resistance peak regardless of reflection. Finally, the dependence of the resistance peak on the density and the wave frequency is examined to show that the general trend is consistent with experimental observations.

  2. Magnetic field response sensor for conductive media

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

    2009-01-01

    A magnetic field response sensor comprises an inductor placed at a fixed separation distance from a conductive surface to address the low RF transmissivity of conductive surfaces. The minimum distance for separation is determined by the sensor response. The inductor should be separated from the conductive surface so that the response amplitude exceeds noise level by a recommended 10 dB. An embodiment for closed cavity measurements comprises a capacitor internal to said cavity and an inductor mounted external to the cavity and at a fixed distance from the cavity's wall. An additional embodiment includes a closed cavity configuration wherein multiple sensors and corresponding antenna are positioned inside the cavity, with the antenna and inductors maintained at a fixed distance from the cavity's wall.

  3. Magnetic Field Response Sensor For Conductive Media

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

    2006-01-01

    A magnetic field response sensor comprises an inductor placed at a fixed separation distance from a conductive surface to address the low RF transmissivity of conductive surfaces. The minimum distance for separation is determined by the sensor response. The inductor should be separated from the conductive surface so that the response amplitude exceeds noise level by a recommended 10 dB. An embodiment for closed cavity measurements comprises a capacitor internal to said cavity and an inductor mounted external to the cavity and at a fixed distance from the cavity s wall. An additional embodiment includes a closed cavity configuration wherein multiple sensors and corresponding antenna are positioned inside the cavity, with the antenna and inductors maintained at a fixed distance from the cavity s wall.

  4. Magnetic field response sensor for conductive media

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant Douglas (Inventor)

    2010-01-01

    A magnetic field response sensor comprises an inductor placed at a fixed separation distance from a conductive surface to address the low RF transmissivity of conductive surfaces. The minimum distance for separation is determined by the sensor response. The inductor should be separated from the conductive surface so that the response amplitude exceeds noise level by a recommended 10 dB. An embodiment for closed cavity measurements comprises a capacitor internal to said cavity and an inductor mounted external to the cavity and at a fixed distance from the cavity's wall. An additional embodiment includes a closed cavity configuration wherein multiple sensors and corresponding antenna are positioned inside the cavity, with the antenna and inductors maintained at a fixed distance from the cavity's wall.

  5. POLOIDAL MAGNETIC FIELD TOPOLOGY FOR TOKAMAKS WITH CURRENT HOLES

    SciTech Connect

    Puerta, Julio; Martin, Pablo; Castro, Enrique

    2009-07-26

    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.

  6. Levitation performance of the magnetized bulk high- Tc superconducting magnet with different trapped fields

    NASA Astrophysics Data System (ADS)

    Liu, W.; Wang, J. S.; Liao, X. L.; Zheng, S. J.; Ma, G. T.; Zheng, J.; Wang, S. Y.

    2011-03-01

    To a high- Tc superconducting (HTS) maglev system which needs large levitation force density, the magnetized bulk high- Tc superconductor (HTSC) magnet is a good candidate because it can supply additional repulsive or attractive force above a permanent magnet guideway (PMG). Because the induced supercurrent within a magnetized bulk HTSC is the key parameter for the levitation performance, and it is sensitive to the magnetizing process and field, so the magnetized bulk HTSC magnets with different magnetizing processes had various levitation performances, not only the force magnitude, but also its force relaxation characteristics. Furthermore, the distribution and configuration of the induced supercurrent are also important factor to decide the levitation performance, especially the force relaxation characteristics. This article experimentally investigates the influences of different magnetizing processes and trapped fields on the levitation performance of a magnetized bulk HTSC magnet with smaller size than the magnetic inter-pole distance of PMG, and the obtained results are qualitatively analyzed by the Critical State Model. The test results and analyses of this article are useful for the suitable choice and optimal design of magnetized bulk HTSC magnets.

  7. Graphene in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Orlita, Milan; Escoffier, Walter; Plochocka, Paulina; Raquet, Bertrand; Zeitler, Uli

    2013-01-01

    Carbon-based nano-materials, such as graphene and carbon nanotubes, represent a fascinating research area aiming at exploring their remarkable physical and electronic properties. These materials not only constitute a playground for physicists, they are also very promising for practical applications and are envisioned as elementary bricks of the future of the nano-electronics. As for graphene, its potential already lies in the domain of opto-electronics where its unique electronic and optical properties can be fully exploited. Indeed, recent technological advances have demonstrated its effectiveness in the fabrication of solar cells and ultra-fast lasers, as well as touch-screens and sensitive photo-detectors. Although the photo-voltaic technology is now dominated by silicon-based devices, the use of graphene could very well provide higher efficiency. However, before the applied research to take place, one must first demonstrates the operativeness of carbon-based nano-materials, and this is where the fundamental research comes into play. In this context, the use of magnetic field has been proven extremely useful for addressing their fundamental properties as it provides an external and adjustable parameter which drastically modifies their electronic band structure. In order to induce some significant changes, very high magnetic fields are required and can be provided using both DC and pulsed technology, depending of the experimental constraints. In this article, we review some of the challenging experiments on single nano-objects performed in high magnetic and low temperature. We shall mainly focus on the high-field magneto-optical and magneto-transport experiments which provided comprehensive understanding of the peculiar Landau level quantization of the Dirac-type charge carriers in graphene and thin graphite.

  8. Magnetic field sources and their threat to magnetic media

    NASA Technical Reports Server (NTRS)

    Jewell, Steve

    1993-01-01

    Magnetic storage media (tapes, disks, cards, etc.) may be damaged by external magnetic fields. The potential for such damage has been researched, but no objective standard exists for the protection of such media. This paper summarizes a magnetic storage facility standard, Publication 933, that ensures magnetic protection of data storage media.

  9. Harmonic undulator radiations with constant magnetic field

    NASA Astrophysics Data System (ADS)

    Jeevakhan, Hussain; Mishra, G.

    2015-01-01

    Harmonic undulators has been analysed in the presence of constant magnetic field along the direction of main undulator field. The spectrum modifications in harmonic undulator radiations and intensity degradation as a function of constant magnetic field magnitude at fundamental and third harmonics have been evaluated with a numerical integration method and generalised Bessel function. The role of harmonic field to overcome the intensity reduction due to constant magnetic field and energy spread in electron beam has also been demonstrated.

  10. Magnetic Field Diagnostic for Sonoluminescence

    NASA Astrophysics Data System (ADS)

    Chou, Tom; Blackman, Eric G.

    1996-02-01

    This study is motivated by the extraordinary process of single bubble sonoluminescence (SBSL), where an acoustically driven spherical shock is thought to power the emitted radiation. We propose new experiments using an external magnetic field which can induce anisotropies in both the shock propagation and radiation pattern. The effects will depend on the temperature, density, conductivity, and size of the radiating region. Our predictions suggest that such an experiment could serve as an important diagnostic in placing bounds on experimental parameters and understanding the physics of SBSL.

  11. Intensity distribution of strong magnetic fields created by opposing linear Halbach assemblies of permanent magnets

    NASA Astrophysics Data System (ADS)

    eulka, Vclav; Pitora, Jaromr; Les?k, Michal; Straka, Pavel; Ciprian, Dalibor; Foukal, Jaroslav

    2013-11-01

    The work is devoted to the geometrical configuration of permanent magnets on the basis of opposing geometrically linear assemblies (e.g. Halbach arrays) for the generation of strong magnetic fields, which have been theoretically modeled and experimentally verified. The implementation of these opposing assemblies using NdFeB magnets of a total weight of 3.75 kg provided a value of magnetic induction in the middle of an air gap of a width of 20 mm that was higher by 56% in comparison with the simplest possible design. When the air gap width was 3 mm, the induction reached a value of 2.16 T, which represents an increase of more than 100%. Simultaneously, however, unlike in the simplest possible parallel configuration, opposing Halbach assemblies have shown, in the middle of an air gap, a significant decrease of the magnetic induction values when passing from the middle of the assemblies in the direction parallel to the x-axis.

  12. Energy buildup in sheared force-free magnetic fields

    NASA Technical Reports Server (NTRS)

    Wolfson, Richard; Low, Boon C.

    1992-01-01

    Photospheric displacement of the footpoints of solar magnetic field lines results in shearing and twisting of the field, and consequently in the buildup of electric currents and magnetic free energy in the corona. The sudden release of this free energy may be the origin of eruptive events like coronal mass ejections, prominence eruptions, and flares. An important question is whether such an energy release may be accompanied by the opening of magnetic field lines that were previously closed, for such open field lines can provide a route for matter frozen into the field to escape the sun altogether. This paper presents the results of numerical calculations showing that opening of the magnetic field is permitted energetically, in that it is possible to build up more free energy in a sheared, closed, force-free magnetic field than is in a related magnetic configuration having both closed and open field lines. Whether or not the closed force-free field attains enough energy to become partially open depends on the form of the shear profile; the results presented compare the energy buildup for different shear profiles. Implications for solar activity are discussed briefly.

  13. Poisson-Vlasov in a strong magnetic field: A stochastic solution approach

    SciTech Connect

    Vilela Mendes, R.

    2010-04-15

    Stochastic solutions are obtained for the Maxwell-Vlasov equation in the approximation where magnetic field fluctuations are neglected and the electrostatic potential is used to compute the electric field. This is a reasonable approximation for plasmas in a strong external magnetic field. Both Fourier and configuration space solutions are constructed.

  14. Angular Dependence of Exchange Bias and Magnetization Reversal Controlled by Electric-Field-Induced Competing Anisotropies.

    PubMed

    Chen, Aitian; Zhao, Yonggang; Li, Peisen; Zhang, Xu; Peng, Renci; Huang, Haoliang; Zou, Lvkuan; Zheng, Xiaoli; Zhang, Sen; Miao, Peixian; Lu, Yalin; Cai, Jianwang; Nan, Ce-Wen

    2016-01-01

    The combination of exchange-biased systems and ferroelectric materials offers a simple and effective way to investigate the angular dependence of exchange bias using one sample with electric-field-induced competing anisotropies. A reversible electric-field-controlled magnetization reversal at zero magnetic field is also realized through optimizing the anisotropy configuration, holding promising applications for ultralow power magnetoelectric devices. PMID:26540229

  15. Nuclear magnetic resonance apparatus for pulsed high magnetic fields.

    PubMed

    Meier, Benno; Kohlrautz, Jonas; Haase, Jrgen; Braun, Marco; Wolff-Fabris, Frederik; Kampert, Erik; Herrmannsdrfer, Thomas; Wosnitza, Joachim

    2012-08-01

    A nuclear magnetic resonance apparatus for experiments in pulsed high magnetic fields is described. The magnetic field pulses created together with various magnet coils determine the requirements such an apparatus has to fulfill to be operated successfully in pulsed fields. Independent of the chosen coil it is desirable to operate the entire experiment at the highest possible bandwidth such that a correspondingly large temporal fraction of the magnetic field pulse can be used to probe a given sample. Our apparatus offers a bandwidth of up to 20 MHz and has been tested successfully at the Hochfeld-Magnetlabor Dresden, even in a very fast dual coil magnet that has produced a peak field of 94.2 T. Using a medium-sized single coil with a significantly slower dependence, it is possible to perform advanced multi-pulse nuclear magnetic resonance experiments. As an example we discuss a Carr-Purcell spin echo sequence at a field of 62 T. PMID:22938280

  16. Existence of Magnetic Surfaces in 3-D Configurations

    NASA Astrophysics Data System (ADS)

    Turnbull, A. D.

    2006-04-01

    A general expression is derived for the existence of magnetic surfaces in 3-D. The expression is valid in an arbitrary coordinate system, which is important when axisymmetry is violated. In the general case, surfaces exist if and only if a simple 1-D equation, equivalent to B?F, has solutions F with certain desired conditions imposed. For example, F must be periodic in angle-like coordinates and monotonic in radial-like variable, s. Applied to a torus, the fact that surfaces are guaranteed to exist with any special symmetry, drops out trivially from this formulation. One can also use alternative representations for B, such as the Clebsch form, to obtain further insight into the conditions where solutions exist. Analogous expressions are also obtained for the existence of current surfaces. Conditions can then be obtained for the existence of both current and magnetic surfaces, yielding criteria for proper nested flux surfaces. Force balance then imposes additional conditions; for ideal MHD, the key condition is the obvious one that Bx(?xB) can be written as the gradient of a potential, which can then be equated to the pressure.

  17. Configuration-dependent electronic and magnetic properties of graphene monolayers and nanoribbons functionalized with aryl groups

    SciTech Connect

    Tian, Xiaoqing Gu, Juan; Xu, Jian-bin

    2014-01-28

    Graphene monolayers functionalized with aryl groups exhibit configuration-dependent electronic and magnetic properties. The aryl groups were adsorbed in pairs of neighboring atoms in the same sublattice A (different sublattices) of graphene monolayers, denoted as the M{sub 2}{sup AA} (M{sub 2}{sup AB}) configuration. The M{sub 2}{sup AA} configuration behaved as a ferromagnetic semiconductor. The band gaps for the majority and minority bands were 1.1 eV and 1.2 eV, respectively. The M{sub 2}{sup AB} configuration behaved as a nonmagnetic semiconductor with a band gap of 0.8 eV. Each aryl group could induce 1 Bohr magneton (?{sub B}) into the molecule-graphene system. Armchair graphene nanoribbons (GNRs) exhibited the same configuration-dependent magnetic properties as the graphene monolayers. The net spin of the functionalized zigzag GNRs was mainly localized on the edges demonstrating an adsorption site-dependent magnetism. For the zigzag GNRs, both the M{sub 2}{sup AA} and M{sub 2}{sup AB} configurations possibly had a magnetic moment. Each aryl group could induce 1.53.5 ?{sub B} into the molecule-graphene system. There was a metal-to-insulator transition after adsorption of the aryl groups for the zigzag GNRs.

  18. Van der Waals torque induced by external magnetic fields

    SciTech Connect

    Esquivel-Sirvent, R.; Cocoletzi, G. H.; Palomino-Ovando, M.

    2010-01-01

    We present a method for inducing and controlling van der Waals torques between two parallel slabs using a constant magnetic field. The torque is calculated using the Barash theory of dispersive torques. In III–IV semiconductors such as InSb, the effect of an external magnetic field is to induce an optical anisotropy, in an otherwise isotropic material, that will in turn induce a torque. The calculations of the torque are done in the Voigt configuration, with the magnetic field parallel to the surface of the slabs. As a case study we consider a slab made of calcite and a second slab made of InSb. In the absence of magnetic field there is no torque. As the magnetic field increases, the optical anisotropy of InSb increases and the torque becomes different from zero, increasing with the magnetic field. The resulting torque is of the same order of magnitude as that calculated using permanent anisotropicmaterials when the magnetic fields is close to 1 T.

  19. Magnetic field of the magnetosheath

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.

    1975-01-01

    The magnetic field of the magnetosheath is most naturally discussed in terms of its steady state and its fluctuating components. Theory of the steady state field is quite well developed and its essential features have been confirmed by observations. The interplanetary field is convected through the bow shock where its magnitude is increased and its direction changed by the minimal amount necessary to preserve the normal component across the shock. Convection within the magnetosheath usually increases the magnitude still further near the subsolar point and further distortes the direction until the field is aligned approximately tangent to the magnetopause. Fluctuations of the magnetosheath field are very complex, variable and not well understood. Spectral peaks are common features which occur at different frequencies at various times. Perturbation vectors of hydromagnetic waves tend to be aligned with the shock and magnetopause surfaces. Magnetosheath waves may be generated upstream, within the magnetosheath, at the bow shock, or at the magnetopause, but the relative importance of these sources is not known.

  20. The synchronous orbit magnetic field data set

    NASA Technical Reports Server (NTRS)

    Mcpherron, R. L.

    1979-01-01

    The magnetic field at synchronous orbit is the result of superposition of fields from many sources such as the earth, the magnetopause, the geomagnetic tail, the ring current and field-aligned currents. In addition, seasonal changes in the orientation of the earth's dipole axis causes significant changes in each of the external sources. Main reasons for which the synchronous orbit magnetic field data set is a potentially valuable resource are outlined. The primary reason why synchronous magnetic field data have not been used more extensively in magnetic field modeling is the presence of absolute errors in the measured fields. Nevertheless, there exists a reasonably large collection of synchronous orbit magnetic field data. Some of these data can be useful in quantitative modeling of the earth's magnetic field. A brief description is given of the spacecraft, the magnetometers, the standard graphical data displays, and the digital data files.

  1. Transonic Flow Field Analysis for Wing-Fuselage Configurations

    NASA Technical Reports Server (NTRS)

    Boppe, C. W.

    1980-01-01

    A computational method for simulating the aerodynamics of wing-fuselage configurations at transonic speeds is developed. The finite difference scheme is characterized by a multiple embedded mesh system coupled with a modified or extended small disturbance flow equation. This approach permits a high degree of computational resolution in addition to coordinate system flexibility for treating complex realistic aircraft shapes. To augment the analysis method and permit applications to a wide range of practical engineering design problems, an arbitrary fuselage geometry modeling system is incorporated as well as methodology for computing wing viscous effects. Configuration drag is broken down into its friction, wave, and lift induced components. Typical computed results for isolated bodies, isolated wings, and wing-body combinations are presented. The results are correlated with experimental data. A computer code which employs this methodology is described.

  2. Stabilization and saturation of the ideal tilt mode in a driven annular field-reversed configuration

    NASA Astrophysics Data System (ADS)

    Pierce, W. F.; Jarboe, T. R.; Brooks, R. D.

    1995-03-01

    The coaxial slow source (CSS) is a device that was designed as a means of forming annular field-reversed configurations (AFRCs) for magnetic fusion on relatively slow (50-100 ?s) time scales. Such configurations are predicted to be ideally unstable to magnetohydrodynamic tilting modes in which one-half of the torus shifts in the positive axial direction and the other half in the negative direction. These instabilities have been observed to grow and saturate at finite amplitude in the CSS as formation progresses. Stable operating regimes of fill pressure/loop voltage space have also been found. The relatively cold temperature (2 eV) of the plasma gives rise to a high classical resistivity, placing the Lundquist number (ratio of resistive to Alfvn time scales) between 0.5 and 10.0. It is proposed that resistivity, along with other dissipation mechanisms such as viscosity and ion-neutral friction, are responsible for the observed stability. Experiments were performed to explore these stability issues. A nonlinear, dynamical systems stability model that accounts for the effects of inductive current drive and dissipation has also been developed, and shows some agreement with the experimental results. The findings of this study are significant for two reasons: (1) It is one of the few clear observations of tilting modes in a FRC-like geometry; and (2) it provides an experimental study of ideally unstable modes in a configuration that does not escape the low Lundquist number regime, finding that the configuration appears stable below a Lundquist number of 0.5.

  3. Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization

    DOEpatents

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

    2000-12-19

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

  4. Magnetic phase diagram of graphene nanorings in an electric field.

    PubMed

    Zhou, Aiping; Sheng, Weidong

    2015-10-14

    Magnetic properties of graphene nanorings are investigated in the presence of an electric field. Within the formalism of Hubbard model, the graphene nanorings of various geometric configurations are found to exhibit rich phase diagram. For a nanoring system which has degenerate states at the Fermi level, the system is shown to undergo an abrupt phase transition from the antiferromagnetic to a nonmagnetic state in an electric field applied cross its zigzag edges. However, the nanoring is found to always stay in the antiferromagnetic state when the electric field is applied cross its armchair edges. For the other nanoring system with a finite single-particle gap, the magnetic moments of its antiferromagnetic ground state is seen to decrease gradually to zero with the electric field applied cross the zigzag edges. When the electric field is applied cross the armchair edges, the nanoring is shown to undergo several magnetic phase transitions before settling itself in a nonmagnetic ordering. PMID:26401952

  5. Magnetic field generation by rotating black holes

    NASA Technical Reports Server (NTRS)

    Leahy, D. A.; Vilenkin, A.

    1981-01-01

    A new mechanism of cosmic magnetic field generation is discussed. Neutrinos asymmetrically emitted by rotating black holes scatter on protons and produce a proton current which generates the magnetic field. It is shown that this mechanism can in principle produce a seed field sufficiently strong to account for present galactic fields.

  6. Near-Field Magnetic Dipole Moment Analysis

    NASA Technical Reports Server (NTRS)

    Harris, Patrick K.

    2003-01-01

    This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective magnetic dipole moment model. The model is most accurate with the earth s geomagnetic field cancelled in a spherical region bounded by the measurement magnetometers with a minimum radius large enough to enclose the magnetic source. Considerably enhanced spacecraft magnetic testing is offered by using this technique in conjunction with a computer-controlled magnetic field measurement system. Such a system, with real-time magnetic field display capabilities, has been incorporated into other existing magnetic measurement facilities and is also used at remote locations where transport to a magnetics test facility is impractical.

  7. Superconducting and hybrid systems for magnetic field shielding

    NASA Astrophysics Data System (ADS)

    Gozzelino, L.; Gerbaldo, R.; Ghigo, G.; Laviano, F.; Truccato, M.; Agostino, A.

    2016-03-01

    In this paper we investigate and compare the shielding properties of superconducting and hybrid superconducting/ferromagnetic systems, consisting of cylindrical cups with an aspect ratio of height/radius close to unity. First, we reproduced, by finite-element calculations, the induction magnetic field values measured along the symmetry axis in a superconducting (MgB2) and in a hybrid configuration (MgB2/Fe) as a function of the applied magnetic field and of the position. The calculations are carried out using the vector potential formalism, taking into account simultaneously the non-linear properties of both the superconducting and the ferromagnetic material. On the basis of the good agreement between the experimental and the computed data we apply the same model to study the influence of the geometric parameters of the ferromagnetic cup as well as of the thickness of the lateral gap between the two cups on the shielding properties of the superconducting cup. The results show that in the considered non-ideal geometry, where the edge effect in the flux penetration cannot be disregarded, the superconducting shield is always the most efficient solution at low magnetic fields. However, a partial recovery of the shielding capability of the hybrid configuration occurs if a mismatch in the open edges of the two cups is considered. In contrast, at high magnetic fields the hybrid configurations are always the most effective. In particular, the highest shielding factor was found for solutions with the ferromagnetic cup protruding over the superconducting one.

  8. Magnetic field waves at Uranus

    NASA Technical Reports Server (NTRS)

    Smith, Charles W.; Goldstein, Melvyn L.; Lepping, Ronald P.; Mish, William H.; Wong, Hung K.

    1994-01-01

    The research efforts funded by the Uranus Data Analysis Program (UDAP) grant to the Bartol Research Institute (BRI) involved the study of magnetic field waves associated with the Uranian bow shock. Upstream wave studies are motivated as a study of the physics of collisionless shocks. Collisionless shocks in plasmas are capable of 'reflecting' a fraction of the incoming thermal particle distribution and directing the resulting energetic particle motion back into the upstream region. Once within the upstream region, the backward streaming energetic particles convey information of the approaching shock to the supersonic flow. This particle population is responsible for the generation of upstream magnetic and electrostatic fluctuations known as 'upstream waves', for slowing the incoming wind prior to the formation of the shock ramp, and for heating of the upstream plasma. The waves produced at Uranus not only differed in several regards from the observations at other planetary bow shocks, but also gave new information regarding the nature of the reflected particle populations which were largely unmeasurable by the particle instruments. Four distinct magnetic field wave types were observed upstream of the Uranian bow shock: low-frequency Alfven or fast magnetosonic waves excited by energetic protons originating at or behind the bow shock; whistler wave bursts driven by gyrating ion distributions within the shock ramp; and two whistler wave types simultaneously observed upstream of the flanks of the shock and argued to arise from resonance with energetic electrons. In addition, observations of energetic particle distributions by the LECP experiment, thermal particle populations observed by the PLS experiment, and electron plasma oscillations recorded by the PWS experiment proved instrumental to this study and are included to some degree in the papers and presentations supported by this grant.

  9. Magnetic field gradient effects on magnetic fluid stabilization

    NASA Astrophysics Data System (ADS)

    Zahn, Markus; Rosensweig, R. E.

    1987-03-01

    The penetrating finger instability which develops when a less viscous fluid pushes a more viscous fluid can be stabilized through the use of a magnetizable fluid in the presence of a magnetic field tangential to the interface. A uniform magnetic field only stabilizes suitably short waves travelling along the field lines. Transverse waves of all wavelengths and orientations are also stabilized if the tangential magnetic field is non-uniform with field decreasing in the direction away from the magnetically permeable fluid. Confirming experiments are described using laboratory sandpacks.

  10. Deformable homeotropic nematic droplets in a magnetic field

    NASA Astrophysics Data System (ADS)

    Otten, Ronald H. J.; van der Schoot, Paul

    2012-10-01

    We present a Frank-Oseen elasticity theory for the shape and structure of deformable nematic droplets with homeotropic surface anchoring in the presence of a magnetic field. Inspired by recent experimental observations, we focus on the case where the magnetic susceptibility is negative, and find that small drops have a lens shape with a homogeneous director field for any magnetic-field strength, whereas larger drops are spherical and have a radial director field, at least if the magnetic field is weak. For strong magnetic fields the hedgehog configuration transforms into a split-core line defect that, depending on the anchoring strength, can be accompanied by an elongation of the tactoid itself. We present a three-dimensional phase diagram that shows the tactoid shape and director field for a given anchoring strength, tactoid size, and magnetic-field strength. Our findings rationalize the different shapes and structures that recently have been observed experimentally for nematic droplets found in dispersions of gibbsite platelets in two types of solvent.

  11. Magnetic field observations in Comet Halley's coma

    NASA Astrophysics Data System (ADS)

    Riedler, W.; Schwingenschuh, K.; Yeroshenko, Ye. G.; Styashkin, V. A.; Russell, C. T.

    1986-05-01

    During the encounter with Comet Halley, the magnetometer (MISCHA) aboard the Vega 1 spacecraft observed an increased level of magnetic field turbulence, resulting from an upstream bow wave. Both Vega spacecraft measured a peak field strength of 70-80 nT and observed draping of magnetic field lines around the cometary obstacle. An unexpected rotation of the magnetic field vector was observed, which may reflect either penetration of magnetic field lines into a diffuse layer related to the contact surface separating the solar-wind and cometary plasma, or the persistence of pre-existing interplanetary field structures.

  12. Overview of C-2 field-reversed configuration experiment plasma diagnosticsa)

    NASA Astrophysics Data System (ADS)

    Gota, H.; Thompson, M. C.; Tuszewski, M.; Binderbauer, M. W.

    2014-11-01

    A comprehensive diagnostic suite for field-reversed configuration (FRC) plasmas has been developed and installed on the C-2 device at Tri Alpha Energy to investigate the dynamics of FRC formation as well as to understand key FRC physics properties, e.g., confinement and stability, throughout a discharge. C-2 is a unique, large compact-toroid merging device that produces FRC plasmas partially sustained for up to ˜5 ms by neutral-beam (NB) injection and end-on plasma-guns for stability control. Fundamental C-2 FRC properties are diagnosed by magnetics, interferometry, Thomson scattering, spectroscopy, bolometry, reflectometry, and NB-related fast-ion/neutral diagnostics. These diagnostics (totaling >50 systems) are essential to support the primary goal of developing a deep understanding of NB-driven FRCs.

  13. Overview of C-2 field-reversed configuration experiment plasma diagnostics

    SciTech Connect

    Gota, H. Thompson, M. C.; Tuszewski, M.; Binderbauer, M. W.

    2014-11-15

    A comprehensive diagnostic suite for field-reversed configuration (FRC) plasmas has been developed and installed on the C-2 device at Tri Alpha Energy to investigate the dynamics of FRC formation as well as to understand key FRC physics properties, e.g., confinement and stability, throughout a discharge. C-2 is a unique, large compact-toroid merging device that produces FRC plasmas partially sustained for up to ?5 ms by neutral-beam (NB) injection and end-on plasma-guns for stability control. Fundamental C-2 FRC properties are diagnosed by magnetics, interferometry, Thomson scattering, spectroscopy, bolometry, reflectometry, and NB-related fast-ion/neutral diagnostics. These diagnostics (totaling >50 systems) are essential to support the primary goal of developing a deep understanding of NB-driven FRCs.

  14. Field-Reversed Configuration Formation Scheme Utilizing a Spheromak and Solenoid Induction

    SciTech Connect

    Gerhardt, S. P.; Belova, E. V.; Yamada, M.; Ji, H.; Ren, B.; McGeehan, B.; Inomoto, M.

    2008-06-12

    A new field-reversed configuration (FRC) formation technique is described, where a spheromak transitions to a FRC with inductive current drive. The transition is accomplished only in argon and krypton plasmas, where low-n kink modes are suppressed; spheromaks with a lighter majority species, such as neon and helium, either display a terminal tilt-mode, or an n=2 kink instability, both resulting in discharge termination. The stability of argon and krypton plasmas through the transition is attributed to the rapid magnetic diffusion of the currents that drive the kink-instability. The decay of helicity during the transition is consistent with that expected from resistivity. This observation indicates a new scheme to form a FRC plasma, provided stability to low-n modes is maintained, as well as a unique situation where the FRC is a preferred state.

  15. Full 180 Magnetization Reversal with Electric Fields

    PubMed Central

    Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.

    2014-01-01

    Achieving 180 magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180 magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90 magnetization rotations, thereby leading to full 180 magnetization reversals. PMID:25512070

  16. Magnetic field effects on microwave absorbing materials

    NASA Technical Reports Server (NTRS)

    Goldberg, Ira; Hollingsworth, Charles S.; Mckinney, Ted M.

    1991-01-01

    The objective of this program was to gather information to formulate a microwave absorber that can work in the presence of strong constant direct current (DC) magnetic fields. The program was conducted in four steps. The first step was to investigate the electrical and magnetic properties of magnetic and ferrite microwave absorbers in the presence of strong magnetic fields. This included both experimental measurements and a literature survey of properties that may be applicable to finding an appropriate absorbing material. The second step was to identify those material properties that will produce desirable absorptive properties in the presence of intense magnetic fields and determine the range of magnetic field in which the absorbers remain effective. The third step was to establish ferrite absorber designs that will produce low reflection and adequate absorption in the presence of intense inhomogeneous static magnetic fields. The fourth and final step was to prepare and test samples of such magnetic microwave absorbers if such designs seem practical.

  17. Stability of topological charge of magnetic skyrmion configurations

    NASA Astrophysics Data System (ADS)

    Jalil, M. B. A.; Tan, S. G.; Siu, Z. B.; Gan, W.; Purnama, I.; Lew, W. S.

    2016-02-01

    We analyze the topological charge of a skyrmion qs, and the corresponding Hall conductivity σxy, which can serve as an electrical read-out for skyrmion-based memory. We derived the general form of the Dzyaloshinskii-Moriya (DM) interaction for any arbitrary orientation of the DM vector D. Based on the DM interaction energy, we obtained the dependence the skyrmion helicity angle γ on the orientation of D. We showed via general mathematical arguments, the topological nature of the skyrmionic charge qs, and its independence of γ and specific details of the interior of the skyrmion (e.g., its core size). Finally, we showed via numerical micromagnetics the stability of qs under varying applied B-fields till the annihilation field, despite the drastic reduction in the skyrmion core size.

  18. Interaction Forces Between Multiple Bodies in a Magnetic Field

    NASA Technical Reports Server (NTRS)

    Joffe, Benjamin

    1996-01-01

    Some of the results from experiments to determine the interaction forces between multiple bodies in a magnetic field are presented in this paper. It is shown how the force values and the force directions depend on the configuration of the bodies, their relative positions to each other, and the vector of the primary magnetic field. A number of efficient new automatic loading and assembly machines, as well as manipulators and robots, have been created based on the relationship between bodies and magnetic fields. A few of these patented magnetic devices are presented. The concepts involved open a new way to design universal grippers for robot and other kinds of mechanisms for the manipulation of objects. Some of these concepts can be used for space applications.

  19. Exploring Magnetic Fields with a Compass

    ERIC Educational Resources Information Center

    Lunk, Brandon; Beichner, Robert

    2011-01-01

    A compass is an excellent classroom tool for the exploration of magnetic fields. Any student can tell you that a compass is used to determine which direction is north, but when paired with some basic trigonometry, the compass can be used to actually measure the strength of the magnetic field due to a nearby magnet or current-carrying wire. In this…

  20. Deformation of Water by a Magnetic Field

    ERIC Educational Resources Information Center

    Chen, Zijun; Dahlberg, E. Dan

    2011-01-01

    After the discovery that superconducting magnets could levitate diamagnetic objects, researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields, which was given the name "The Moses Effect." Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary…

  1. Magnetic field inhomogeneity in superconducting composites

    NASA Astrophysics Data System (ADS)

    Golosovsky, M.; Bontemps, N.; Davidov, D.; Waysand, G.

    1996-03-01

    The distribution of a static magnetic field in the composites consisting of YBCO powder in paraffin wax as function of temperature and volume fraction of YBCO is studied using ESR and magnetization techniques. We show that the field distribution is determined by the magnetization and the demagnetizing factor of the superconducting particles.

  2. Exploring Magnetic Fields with a Compass

    ERIC Educational Resources Information Center

    Lunk, Brandon; Beichner, Robert

    2011-01-01

    A compass is an excellent classroom tool for the exploration of magnetic fields. Any student can tell you that a compass is used to determine which direction is north, but when paired with some basic trigonometry, the compass can be used to actually measure the strength of the magnetic field due to a nearby magnet or current-carrying wire. In this

  3. Deformation of Water by a Magnetic Field

    ERIC Educational Resources Information Center

    Chen, Zijun; Dahlberg, E. Dan

    2011-01-01

    After the discovery that superconducting magnets could levitate diamagnetic objects, researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields, which was given the name "The Moses Effect." Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary

  4. Baryon onset in a magnetic field

    NASA Astrophysics Data System (ADS)

    Haber, Alexander; Preis, Florian; Schmitt, Andreas

    2016-01-01

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

  5. Magnetic field effect on charged Brownian swimmers

    NASA Astrophysics Data System (ADS)

    Sandoval, M.; Velasco, R. M.; Jiménez-Aquino, J. I.

    2016-01-01

    We calculate the effective diffusion of a spherical self-propelled charged particle swimming at low Reynolds number, and subject to a time-dependent magnetic field and thermal agitation. We find that the presence of an external magnetic field may reduce or enhance (depending on the type of swimming and magnetic field applied) the swimmer's effective diffusion, hence we get another possible strategy to control its displacement. For swimmers performing reciprocal motion, and under an oscillating time-dependent magnetic field, mechanical resonance appears when the swimmer and magnetic frequencies coincide, thus enhancing the particle's effective diffusion. Our analytical results are compared with Brownian Dynamics simulations and we obtain excellent agreement.

  6. Analysis of magnetic field levels at KSC

    NASA Technical Reports Server (NTRS)

    Christodoulou, Christos G.

    1994-01-01

    The scope of this work is to evaluate the magnetic field levels of distribution systems and other equipment at Kennedy Space Center (KSC). Magnetic fields levels in several operational areas and various facilities are investigated. Three dimensional mappings and contour are provided along with the measured data. Furthermore, the portion of magnetic fields generated by the 60 Hz fundamental frequency and the portion generated by harmonics are examined. Finally, possible mitigation techniques for attenuating fields from electric panels are discussed.

  7. Magnetic field signatures of substorms on high-latitude field lines in the nighttime magnetosphere.

    NASA Technical Reports Server (NTRS)

    Fairfield, D. H.

    1973-01-01

    Two types of magnetic field changes are repeatedly observed in the high-latitude nightside magnetosphere in association with magnetic substorms. One type of field change occurs on field lines associated with the high-latitude part of the auroral oval and is characterized by a sudden decrease in the field strength accompanied by an abrupt perturbation in the field declination angle. These changes are attributed to field-aligned sheet currents flowing on the high-latitude boundary of an expanding plasma sheet following substorms. A second type of field change observed on polar cap field lines is a decrease in field inclination during substorms. This type of change is regarded as a further manifestation of the changing field configuration during substorms and can be described in terms of azimuthal currents.

  8. High-magnetic-field MHD-generator program

    NASA Astrophysics Data System (ADS)

    Nakamura, T.; Eustis, R. H.; Mitchner, M.; Self, S. A.; Koester, J. K.; Kruger, C. H.

    1981-07-01

    Progress in an experimental and theoretical program designed to investigate MHD channel phenomena which are important at high magnetic fields is described. The areas of research include nonuniformity effects, boundary layers, Hall field breakdown, the effects of electrode configuration and current concentrations, and studies of steady-state combustion disk and linear channels in an existing 6 Tesla magnet of small dimensions. In the study of the effects of nonuniformities, experiments were performed to test a multi-channel, fiber optics diagnostic system that yields time-resolved temperature profiles in an MHD chanel. For the study of magneto-acoustic fluctuation phenomena, a one dimensional model was developed to describe the performance of a non-ideal MHD generator with a generalized electrical configuration. A two dimensional MHD computer code was developed which predicts the dependence on electrode and insulator dimensions of the onset of interelectrode Hall field breakdown, as initiated either by breakdown in the insulator or in the plasma.

  9. Ion energy distribution function measurements in the Irvine Field Reversed Configuration

    NASA Astrophysics Data System (ADS)

    Roche, Thomas; Garate, Eusebio; Harris, Wayne; Heidbrink, William; McWilliams, Roger; Trask, Erik

    2009-11-01

    A gridded ion energy analyzer has been constructed to measure the ion energy distribution function in the Irvine Field Reversed Configuration (IFRC). Three grids provide Debye shielding, electron rejection and ion energy selection, respectively. It has an acceptance angle of ˜20 degrees. Due to a large, negative, floating potential a fast (17 MHz bandwidth) optocoupler is used to decouple the signal from earth ground. A dummy collector is also used to subtract background noise pickup. Ion current flows in the negative theta direction in the IFRC. Measurements have been taken both parallel and anti-parallel to the current near the magnetic null. These measurements have shown that a shifted Maxwellian, with peak energy of ˜18 eV, can be fit to the ion energy distribution function. This number agrees with the upper limit of 20 eV previously placed on the peak by a time of flight diagnosticfootnotetext W. S. Harris et al., Rev. Sci. Instrum. 79, 10F313 (2008). Coupling of the distribution function measurements with magnetic field measurements will determine the distribution of orbit types in the IFRC, specifically the ratio of betatron to drift type particle orbits.

  10. Abnormal Magnetic Field Effects on Electrogenerated Chemiluminescence

    NASA Astrophysics Data System (ADS)

    Pan, Haiping; Shen, Yan; Wang, Hongfeng; He, Lei; Hu, Bin

    2015-03-01

    We report abnormal magnetic field effects on electrogenerated chemiluminescence (MFEECL) based on triplet emission from the Ru(bpy)3Cl2-TPrA electrochemical system: the appearance of MFEECL after magnetic field ceases. In early studies the normal MFEECL have been observed from electrochemical systems during the application of magnetic field. Here, the abnormal MFEECL suggest that the activated charge-transfer [Ru(bpy)33+ TPrA] complexes may become magnetized in magnetic field and experience a long magnetic relaxation after removing magnetic field. Our analysis indicates that the magnetic relaxation can gradually increase the density of charge-transfer complexes within reaction region due to decayed magnetic interactions, leading to a positive component in the abnormal MFEECL. On the other hand, the magnetic relaxation facilitates an inverse conversion from triplets to singlets within charge-transfer complexes. The inverse triplet --> singlet conversion reduces the density of triplet light-emitting states through charge-transfer complexes and gives rise to a negative component in the abnormal MFEECL. The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFEECL after ceasing magnetic field. Nevertheless, our experimental studies may reveal un-usual magnetic behaviors with long magnetic relaxation from the activated charge-transfer [Ru(bpy)33+ TPrA] complexes in solution at room temperature.

  11. DIFFUSION OF MAGNETIC FIELD AND REMOVAL OF MAGNETIC FLUX FROM CLOUDS VIA TURBULENT RECONNECTION

    SciTech Connect

    Santos-Lima, R.; De Gouveia Dal Pino, E. M.; Lazarian, A.; Cho, J.

    2010-05-01

    The diffusion of astrophysical magnetic fields in conducting fluids in the presence of turbulence depends on whether magnetic fields can change their topology via reconnection in highly conducting media. Recent progress in understanding fast magnetic reconnection in the presence of turbulence reassures that the magnetic field behavior in computer simulations and turbulent astrophysical environments is similar, as far as magnetic reconnection is concerned. This makes it meaningful to perform MHD simulations of turbulent flows in order to understand the diffusion of magnetic field in astrophysical environments. Our studies of magnetic field diffusion in turbulent medium reveal interesting new phenomena. First of all, our three-dimensional MHD simulations initiated with anti-correlating magnetic field and gaseous density exhibit at later times a de-correlation of the magnetic field and density, which corresponds well to the observations of the interstellar media. While earlier studies stressed the role of either ambipolar diffusion or time-dependent turbulent fluctuations for de-correlating magnetic field and density, we get the effect of permanent de-correlation with one fluid code, i.e., without invoking ambipolar diffusion. In addition, in the presence of gravity and turbulence, our three-dimensional simulations show the decrease of the magnetic flux-to-mass ratio as the gaseous density at the center of the gravitational potential increases. We observe this effect both in the situations when we start with equilibrium distributions of gas and magnetic field and when we follow the evolution of collapsing dynamically unstable configurations. Thus, the process of turbulent magnetic field removal should be applicable both to quasi-static subcritical molecular clouds and cores and violently collapsing supercritical entities. The increase of the gravitational potential as well as the magnetization of the gas increases the segregation of the mass and magnetic flux in the saturated final state of the simulations, supporting the notion that the reconnection-enabled diffusivity relaxes the magnetic field + gas system in the gravitational field to its minimal energy state. This effect is expected to play an important role in star formation, from its initial stages of concentrating interstellar gas to the final stages of the accretion to the forming protostar. In addition, we benchmark our codes by studying the heat transfer in magnetized compressible fluids and confirm the high rates of turbulent advection of heat obtained in an earlier study.

  12. Bipolar pulse field for magnetic refrigeration

    DOEpatents

    Lubell, M.S.

    1994-10-25

    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.

  13. Bipolar pulse field for magnetic refrigeration

    DOEpatents

    Lubell, Martin S. (Oak Ridge, TN)

    1994-01-01

    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.

  14. Formation of a White-Light Jet Within a Quadrupolar Magnetic Configuration

    NASA Astrophysics Data System (ADS)

    Filippov, Boris; Koutchmy, Serge; Tavabi, Ehsan

    2013-08-01

    We analyze multi-wavelength and multi-viewpoint observations of a large-scale event viewed on 7 April 2011, originating from an active-region complex. The activity leads to a white-light jet being formed in the outer corona. The topology and evolution of the coronal structures were imaged in high resolution using the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO). In addition, large field-of-view images of the corona were obtained using the Sun Watcher using Active Pixel System detector and Image Processing (SWAP) telescope onboard the PRoject for Onboard Autonomy (PROBA2) microsatellite, providing evidence for the connectivity of the coronal structures with outer coronal features that were imaged with the Large Angle Spectrometric Coronagraph (LASCO) C2 on the S olar and Heliospheric Observatory (SOHO). The data sets reveal an Eiffel-tower type jet configuration extending into a narrow jet in the outer corona. The event starts from the growth of a dark area in the central part of the structure. The darkening was also observed in projection on the disk by the Solar TErrestrial RElations Observatory-Ahead (STEREO-A) spacecraft from a different point of view. We assume that the dark volume in the corona descends from a coronal cavity of a flux rope that moved up higher in the corona but still failed to erupt. The quadrupolar magnetic configuration corresponds to a saddle-like shape of the dark volume and provides a possibility for the plasma to escape along the open field lines into the outer corona, forming the white-light jet.

  15. On Magnetic Field Generation Mechanisms in Astrophysics

    NASA Astrophysics Data System (ADS)

    Cherny, O. G.

    Magnetic chemically peculiar stars (CP stars) are characterized by a strong magnetic field, peculiar chemical composition and slow rotation. Since the origin and evolution of CP stars may be responsible for such unusual features, understanding the mechanisms of generation of the magnetic field is one of the ways to learn more about the CP star characteristics. At present there are two mechanisms of magnetic field generation considered in astrophysics, a fossil field hypothesis and turbulent dynamo theory. However, there is another mechanism of magnetic field generation. All the elementary particles including the most abundant, i. e. the protons, electrons, neutrons, have their own angular momenta and the corresponding magnetic momenta. Microscopic magnetic fields are determined generally by these magnetic momenta. Provided that microscopic magnetic fields are aligned, large-scale magnetic fields may be generated, which has been proved in the experiments of Barnett, Einstein and de Haas. This phenomenon is best illustrated by the experiments with iron. Analysis performed in the current study showed that all the large bodies of the Solar System have both an iron-nickel core and a magnetic field, which is proportional to the planet's core volume and its rotational velocity. We hypothesize that the reason for this phenomenon is a magnetic interaction of ferromagnetic materials, which occurred during the formation of the Solar System. We show that the magnitude of the magnetic field of the Earth and a change of magnetic field polarity can be explained by the gyromagnetic effect. In the beginning of formation of the Solar System the prospective Sun was the main attractive center. Therefore, there is a possibility that the Sun contains a massive (relative to the Earth) iron-nickel core.

  16. Application peculiarities of magnetic materials for protection from magnetic fields

    NASA Astrophysics Data System (ADS)

    Wai, P.; Dmitrenko, V.; Grabchikov, S.; Vlasik, K.; Novikov, A.; Petrenko, D.; Trukhanov, V.; Ulin, S.; Uteshev, Z.; Chernysheva, V.; Shustov, A.

    2016-02-01

    In different materials for magnetic shields, the maximum permeability is achieved for different values of the magnetic field. This determines the choice of material. So for protection from magnetic fields strength of 10 - 150 A/m it is advisable to apply the amorphous ribbon 84KXCP. For stronger fields (more than 400 A/m) it is recommended to use MFS based on Ni20Fe80. Use of these materials allows creating an effective shield working in a wide range of magnetic field strengths.

  17. Instantaneous configuration of the geomagnetic field inferred from the low-altitude isotropic boundaries: modeling and observations

    NASA Astrophysics Data System (ADS)

    Ilie, Raluca; Ganushkina, Natalia; Toth, Gabor; Liemohn, Michael

    2015-04-01

    Understanding the interplay between ionospheric, auroral and magnetospheric phenomena requires detailed knowledge of Earths magnetic field geometry under various solar wind conditions. This geometry is directly relevant to the magnetic field mapping between different regions of near-Earth space.To evaluate the instantaneous geomagnetic field configuration we probe the isotropic boundaries (IB) of energetic particles measured at low altitudes. Those are interpreted as the boundary between the regions of adiabatic and stochastic particle motion in the equatorial magnetotail and provide information regarding the degree of magnetic field stretching.We investigate the topology and dynamics of the magnetotail current during active and quiet times as de- pendent on solar wind and IMF parameters based on NOAA/POES MEPED and DMSP SSJ/4 measurements in combination with global magnetospheric simulations using the Space Weather Modeling Framework (SWMF).The extensive NOAA/POES MEPED low-altitude data sets give the locations of isotropic boundaries, which are used to extract information regarding particle distributions and field structure in the source regions in the magnetosphere.We present a comparison between the magnetic field lines with the observed IB latitude and those com- puted from the SWMF using the theoretical relation for IB locations in the magnetotail, i.e. where the ratio between curvature radius and Larmor radius is close to 8. This investigation assesses the accuracy of the model magnetic field and the structure of the magnetotail. The results are examined in relation to the solar wind and IMF conditions to determine the corresponding configuration and dynamics of the magnetotail.

  18. Beam Fields in an Integrated Cavity, Coupler and Window Configuration

    SciTech Connect

    Weathersby, Stephen; Novokhatski, Alexander; /SLAC

    2010-02-10

    In a multi-bunch high current storage ring, beam generated fields couple strongly into the RF cavity coupler structure when beam arrival times are in resonance with cavity fields. In this study the integrated effect of beam fields over several thousand RF periods is simulated for the complete cavity, coupler, window and waveguide system of the PEP-II B-factory storage ring collider. We show that the beam generated fields at frequencies corresponding to several bunch spacings for this case gives rise to high field strength near the ceramic window which could limit the performance of future high current storage rings such as PEP-X or Super B-factories.

  19. Benzene at 1 GHz. Magnetic field-induced fine structure

    NASA Astrophysics Data System (ADS)

    Heist, L. M.; Poon, C.-D.; Samulski, E. T.; Photinos, D. J.; Jokisaari, J.; Vaara, J.; Emsley, J. W.; Mamone, S.; Lelli, M.

    2015-09-01

    The deuterium NMR spectrum of benzene-d6 in a high field spectrometer (1 GHz protons) exhibits a magnetic field-induced deuterium quadrupolar splitting ??. The magnitude of ?? observed for the central resonance is smaller than that observed for the 13C satellite doublets ???. This difference, ?(??) = ??? - ??, is due to unresolved fine structure contributions to the respective resonances. We determine the origins of and simulate this difference, and report pulse sequences that exploit the connectivity of the peaks in the 13C and 2H spectra to determine the relative signs of the indirect coupling, JCD, and ??. The positive sign found for ?? is consonant with the magnetic field biasing of an isolated benzene molecule-the magnetic energy of the aromatic ring is lowest for configurations where the C6 axis is normal to the field. In the neat liquid the magnitude of ?? is decreased by the pair correlations in this prototypical molecular liquid.

  20. Stepped Impedance Resonators for High Field Magnetic Resonance Imaging

    PubMed Central

    Akgun, Can E.; DelaBarre, Lance; Yoo, Hyoungsuk; Sohn, Sung-Min; Snyder, Carl J.; Adriany, Gregor; Ugurbil, Kamil; Gopinath, Anand; Vaughan, J. Thomas

    2014-01-01

    Multi-element volume radio-frequency (RF) coils are an integral aspect of the growing field of high field magnetic resonance imaging (MRI). In these systems, a popular volume coil of choice has become the transverse electromagnetic (TEM) multi-element transceiver coil consisting of microstrip resonators. In this paper, to further advance this design approach, a new microstrip resonator strategy in which the transmission line is segmented into alternating impedance sections referred to as stepped impedance resonators (SIRs) is investigated. Single element simulation results in free space and in a phantom at 7 tesla (298 MHz) demonstrate the rationale and feasibility of the SIR design strategy. Simulation and image results at 7 tesla in a phantom and human head illustrate the improvements in transmit magnetic field, as well as, RF efficiency (transmit magnetic field versus SAR) when two different SIR designs are incorporated in 8-element volume coil configurations and compared to a volume coil consisting of microstrip elements. PMID:23508243

  1. Magnetic field waves at Uranus

    NASA Technical Reports Server (NTRS)

    Smith, Charles W.; Goldstein, Melvyn L.; Lepping, Ronald P.; Mish, William H.; Wong, Hung K.

    1991-01-01

    The proposed research efforts funded by the UDAP grant to the BRI involve the study of magnetic field waves associated with the Uranian bow shock. This is a collaborative venture bringing together investigators at the BRI, Southwest Research Institute (SwRI), and Goddard Space Flight Center (GSFC). In addition, other collaborations have been formed with investigators granted UDAP funds for similar studies and with investigators affiliated with other Voyager experiments. These investigations and the corresponding collaborations are included in the report. The proposed effort as originally conceived included an examination of waves downstream from the shock within the magnetosheath. However, the observations of unexpected complexity and diversity within the upstream region have necessitated that we confine our efforts to those observations recorded upstream of the bow shock on the inbound and outbound legs of the encounter by the Voyager 2 spacecraft.

  2. Parallel heat transport in integrable and chaotic magnetic fields

    SciTech Connect

    Del-Castillo-Negrete, Diego B; Chacon, Luis

    2012-01-01

    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 chal- lenging: (i) The extreme anisotropy between the parallel (i.e., along the magnetic field), , and the perpendicular, , conductivities ( / may exceed 1010 in fusion plasmas); (ii) Magnetic field lines chaos which in general complicates (and may preclude) the construction of magnetic field line coordinates; and (iii) Nonlocal parallel transport in the limit of small collisionality. 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 geom- etry. 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 chain), 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 closures, is non-diffusive, thus casting doubts on the appropriateness of the applicability of quasilinear diffusion descriptions. General conditions for the existence of non-diffusive, multivalued flux-gradient relations in the temperature evolution are derived.

  3. Parallel heat transport in integrable and chaotic magnetic fields

    SciTech Connect

    Castillo-Negrete, D. del; Chacon, L.

    2012-05-15

    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.

  4. Reconstruction of equilibrium magnetic configurations in the Globus-M spherical tokamak

    NASA Astrophysics Data System (ADS)

    Sakharov, N. V.; Voronin, A. V.; Gusev, V. K.; Kavin, A. A.; Kamenshchikov, S. N.; Lobanov, K. M.; Minaev, V. B.; Novokhatsky, A. N.; Patrov, M. I.; Petrov, Yu. V.; Shchegolev, P. B.

    2015-12-01

    The results of reconstruction of equilibrium magnetic configurations in the Globus-M spherical tokamak by means of the EFIT code and by the method of movable filaments with the use of the data from magnetic measurements are compared. The EFIT code allows one to completely reconstruct the magnetic configuration by solving the Grad-Shafranov equation. In the method of movable filaments, the distribution of the toroidal current flowing through the plasma is described by a set of infinitely thin current-carrying rings. In this method, the last closed magnetic surface (LCMS) and the open surfaces lying beyond the LCMS are calculated. Using both methods, the coordinates of the regions where the separatrix strikes the divertor plates were determined. The results obtained agree well with the distributions of the temperature over the tungsten divertor tiles measured using an IR camera.

  5. Magnetic Configuration Effects on Fast Ion Losses Induced by Fast Ion Driven Toroidal Alfvn Eigenmodes in the Large Helical Device

    NASA Astrophysics Data System (ADS)

    Ogawa, K.; Isobe, M.; Toi, K.; Watanabe, F.; A. Spong, D.; Shimizu, A.; Osakabe, M.; S. Darrow, D.; Ohdachi, S.; Sakakibara, S.; LHD Experiment Group

    2012-04-01

    Beam-ion losses induced by fast-ion-driven toroidal Alfvn eigenmodes (TAE) were measured with a scintillator-based lost fast-ion probe (SLIP) in the large helical device (LHD). The SLIP gave simultaneously the energy E and the pitch angle ? = arccos(?///?) distribution of the lost fast ions. The loss fluxes were investigated for three typical magnetic configurations of Rax_vac = 3.60 m, 3.75 m, and 3.90 m, where Rax_vac is the magnetic axis position of the vacuum field. Dominant losses induced by TAEs in these three configurations were observed in the E/? regions of 50~190 keV/40, 40~170 keV/25, and 30~190 keV/30, respectively. Lost-ion fluxes induced by TAEs depend clearly on the amplitude of TAE magnetic fluctuations, Rax_vac and the toroidal field strength Bt. The increment of the loss fluxes has the dependence of (bTAE/Bt)s. The power s increases from s = 1 to 3 with the increase of the magnetic axis position in finite beta plasmas.

  6. Magnetic Configuration Effects on Fast Ion Losses Induced by Fast Ion Driven Toroidal Alfven Eigenmodes in the Large Helical Device

    SciTech Connect

    Ogawa, K.; Isobe, M.; Watanabe, F.; Spong, Donald A; Shimizu, A.; Osakabe, M.; Ohdachi, S.; Sakakibara, S.

    2012-01-01

    Beam-ion losses induced by fast-ion-driven toroidal Alfven eigenmodes (TAE) were measured with a scintillator-based lost fast-ion probe (SLIP) in the large helical device (LHD). The SLIP gave simultaneously the energy E and the pitch angle chi = arccos(v(parallel to)/v) distribution of the lost fast ions. The loss fluxes were investigated for three typical magnetic configurations of R{sub ax{_}vac} = 3.60 m, 3.75 m, and 3.90 m, where R{sub ax{_}vac} is the magnetic axis position of the vacuum field. Dominant losses induced by TAEs in these three configurations were observed in the E/chi regions of 50 similar to 190 keV/40 degrees, 40 similar to 170 keV/25 degrees, and 30 similar to 190 keV/30 degrees, respectively. Lost-ion fluxes induced by TAEs depend clearly on the amplitude of TAE magnetic fluctuations, R{sub ax{_}vac} and the toroidal field strength B{sub t}. The increment of the loss fluxes has the dependence of (b{sub TAE}/B{sub t}){sup s}. The power s increases from s = 1 to 3 with the increase of the magnetic axis position in finite beta plasmas.

  7. Multiple Ribbons of a M1.6 Flare Related to the Magnetic Configuration of the NOAA AR 365

    NASA Astrophysics Data System (ADS)

    Chandra, R.; Schmieder, B.; Aulanier, G.; Malherbe, M. J.

    2008-09-01

    The aim of this paper is to understand the magnetic configuration of an active region NOAA 365 and its evolution before and after the occurrence of a M1.6 flare in order to understand the magnetic origin of the flare and its development at particularly the ribbons. We analyze a M1.6 flare occurring in the active region NOAA 365, using space instruments (SOHO/MDI, EIT, TRACE, RHESSI) as well as ground based instruments i.e. the MSDP spectrograph of the Meudon solar tower. The analysis of the magnetic topology of the region is done by using a force-free field linear extrapolation code of the photospheric field proposed in the database FROMAGE. Two series of ribbons are identified, signature of the reconnection, the main ribbons in the center of the active region and secondary ribbons at the periphery of the active region. The main ribbons have a `J' shape, typical shape for large emerging flux tube. The secondary ribbons are explained by the magnetic configuration.

  8. A Field-Sweep/Field-Lock System for Superconducting Magnets-Application to High-Field EPR

    PubMed Central

    Maly, Thorsten; Bryant, Jeff; Ruben, David; Griffin, Robert G.

    2007-01-01

    We describe a field-lock/field-sweep system for the use in superconducting magnets. The system is based on a commercially available field mapping unit and a custom designed broad-band 1H-NMR probe. The NMR signal of a small water sample is used in a feedback loop to set and control the magnetic field to high accuracy. The current instrumental configuration allows field sweeps of 0.4 T and a resolution of up to 10-5 T (0.1 G) and the performance of the system is demonstrated in a high-field electron paramagnetic resonance (EPR) application. The system should also be of utility in other experiments requiring precise and reproducible sweeps of the magnetic field such as DNP, ENDOR or PELDOR. PMID:17027306

  9. Effect of magnetic field profile on the anode fall in a Hall-effect thruster discharge

    SciTech Connect

    Dorf, L.; Raitses, Y.; Fisch, N.J.

    2006-05-15

    The effect of the magnetic field configuration on the anode fall in an E-vectorxB-vector discharge of a Hall thruster is studied both experimentally and theoretically. Plasma potential, electron temperature, and plasma density in the near-anode region are measured with a biased probe in three configurations of the magnetic field. It is observed that the anode fall in a Hall thruster can be changed from negative to positive by creating a magnetic field configuration with a zero magnetic field region. Similar configurations are utilized in some advanced Hall thrusters, like an ATON thruster. Results of the measurements are employed to model a Hall thruster with different magnetic field configurations, including the one with a zero-field region. Different anode sheath regimes observed experimentally are used to set the boundary conditions for the quasineutral plasma. Numerical solutions obtained with a hydrodynamic quasi-one-dimensional model suggest that varying the magnetic field configuration affects the electron mobility both inside and outside the channel, as well as the plasma density distribution along the axis.

  10. Vector Tomography Inversion for the 3D Coronal Magnetic Field Based on CoMP data

    NASA Astrophysics Data System (ADS)

    Kramar, M.; Lin, H.; Tomczyk, S.; Inhester, B.; Davila, J. M.

    2011-12-01

    Magnetic fields in the solar corona dominates the gas pressure and therefore determine the static and dynamic properties of the corona. Direct measurement of the coronal magnetic field is one of the most challenging problems in observational solar astronomy and recently a significant progress has been achieved here with deployment of the HAO Coronal Multichannel Polarimeter (CoMP). The instrument provides polarization measurements of Fe XIII 10747 A forbidden line emission. The observed polarization depends on magnetic field through the Hanle and Zeeman effects. However, because the coronal measurements are integrated over line-of-site (LOS), it is impossible to derive the configuration of the coronal magnetic field from a single observation (from a single viewing direction). The vector tomography techniques based on measurements from several viewing directions has the potential to resolve the 3D coronal magnetic field structure over LOS. Because of the non-linear character of the Hanle effect, the reconstruction result based on such data is not straightforward and depends on the particular coronal field configuration. Therefore we study here what is the sensitivity of the vector tomographic inversion to sophisticated (MHD) coronal magnetic field models. For several important cases of magnetic field configuration, it has been found that even just Stokes-Q and -U data (supplied with 3D coronal density and temperature) can be used in vector tomography to provide a realistic 3D coronal magnetic field configuration. This vector tomograpic technique is applied to CoMP data.

  11. Asymptotic analysis of force-free magnetic fields of cylindrical symmetry

    NASA Technical Reports Server (NTRS)

    Sturrock, P. A.; Antiochos, S. K.; Roumeliotis, G.

    1995-01-01

    It is known from computer calculations that if a force-free magnetic-field configuration is stressed progressively by footpoint displacements, the configuration expands and approaches the open configuration with the same surface flux distribution, and, in the process, the energy of the field increases progressively. Analysis of a simple model of force-free fields of cylindrical symmetry leads to simple asymptotic expressions for the extent and energy of such a configuration. The analysis is carried through for both spherical and planar source surfaces. According to this model, the field evolves in a well-behaved manner with no indication of instability or loss of equilibrium.

  12. Swarm: ESA's Magnetic Field Mission

    NASA Astrophysics Data System (ADS)

    Plank, G.; Floberghagen, R.; Menard, Y.; Haagmans, R.

    2013-12-01

    Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme, and is scheduled for launch in fall 2013. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution using a constellation of three identical satellites. The mission shall deliver data that allow access to new insights into the Earth system by improved scientific understanding of the Earth's interior and near-Earth electromagnetic environment. After launch and triple satellite release at an initial altitude of about 490 km, a pair of the satellites will fly side-by-side with slowly decaying altitude, while the third satellite will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission science goals are to provide a unique view into Earth's core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently in the final stage of the development phase, will be addressed. A consortium of European scientific institutes is developing a distributed processing system to produce geophysical (Level 2) data products for the Swarm user community. The setup of the Swarm ground segment and the contents of the data products will be addressed. In case the Swarm satellites are already in orbit, a summary of the on-going mission operations activities will be given. More information on Swarm can be found at www.esa.int/esaLP/LPswarm.html.

  13. DC-based magnetic field controller

    DOEpatents

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

    1994-01-01

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

  14. DC-based magnetic field controller

    DOEpatents

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

    1994-05-31

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

  15. Representation of magnetic fields in space

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1975-01-01

    Several methods by which a magnetic field in space can be represented are reviewed with particular attention to problems of the observed geomagnetic field. Time dependence is assumed to be negligible, and five main classes of representation are described by vector potential, scalar potential, orthogonal vectors, Euler potentials, and expanded magnetic field.

  16. Static uniform magnetic fields and amoebae

    SciTech Connect

    Berk, S.G.; Srikanth, S.; Mahajan, S.M.; Ventrice, C.A.

    1997-03-01

    Three species of potentially pathogenic amoebae were exposed to 71 and 106.5 mT from constant homogeneous magnetic fields and examined for inhibition of population growth. The number of amoebae for three species was significantly less than controls after a 72 h exposure to the magnetic fields when the temperature was 20 C or above. Axenic cultures, i.e., cultures grown without bacteria, were significantly affected after only 24 h. In 20 of 21 tests using the three species, the magnetic field significantly inhibited the growth of amoebae. In one test in which the temperature was 20 C for 48 h, exposure to the magnetic field was not inhibitory. Final numbers of magnetic field-exposed amoebae ranged from 9 to 72% lower than the final numbers of unexposed controls, depending on the species. This research may lead to disinfection strategies utilizing magnetic fields for surfaces on which pathogenic amoebae may proliferate.

  17. Experimental study of the formation of field-reversed configurations employing high-order multipole fields

    NASA Astrophysics Data System (ADS)

    Slough, J. T.; Hoffman, A. L.

    1990-04-01

    A high-order multipole ``barrier'' field was applied at the vacuum tube wall in the TRX experiment [Phys. Fluids B 1, 840 (1989)] during both the preionization and field reversal phases of field-reversed configuration (FRC) formation. Use of this field during field reversal resulted in a significant reduction of impurities as well as increased flux trapping. With a large enough B? at the wall, sheath detachment from the wall became apparent, and flux loss through the sheath became negligible (<10%). At larger wall B? (>1.5 kG), destructive rotational spin-up occurred, driven by Hall current forces. When the multipole barrier field was also applied during either axial discharge or ringing theta current preionization, a very symmetric and uniform breakdown of the fill gas was achieved. In particular, using ringing theta preionization, complete ionization of the fill gas was accomplished with purely inductive fields of remarkably low magnitude, where Ez?3 V/cm, and E??20 V/cm. Due to the improved ionization symmetry, about 65% to 75% of the lift-off flux (flux remaining after field reversal) could be retained through the remaining formation processes into an equilibrium FRC. Using the multipole field during both preionization and formation, it was possible to form FRC's with good confinement with greater than 3 mWb of trapped flux at 15 mTorr D2 or H2 in a 10 cm radius device. Values of s in excess of 4 could be achieved in this manner.

  18. Ion pump using cylindrically symmetric spindle magnetic field

    NASA Astrophysics Data System (ADS)

    Rashid, M. H.

    2012-11-01

    For all accelerators and many research and industries, excellent vacuum conditions are required and the highest possible pumping rates are necessary. For most applications the standard ion sputtering pump (ISP) meets these requirements and is optimal for financial point of view also. The physical principle of the ISP is well known and many companies manufacture variety of ISP. Most of them use dipole magnetic field produced by permanent magnet and electric dipole field between the electrodes in which tenuous plasma is created because of interaction of between the relatively fast electrons slow residual gas atoms. Performance of an ISP depends basically on the electron cloud density in between the titanium electrodes but in the available present configurations no consideration has been given to electron confinement which needs a mirror magnetic field. If this is incorporated it will make a robust ISP surely; furthermore, the requirement of constant feeding of high voltage to electrodes for supplying sufficient number of electrons will be reduced too. A study has been performed to create sufficient rotationally symmetric spindle magnetic field (SMF) with inherent presence of magnetic mirror effect to electron motion to confine them for longer time for enhancing the density of electron cloud between the electrodes. It will lessen the electric power feeding the electrodes and lengthen their life-time. Construction of further compact and robust ISP is envisaged herein. The field simulation using the commercially available permanent magnet together with simulation of electron motion in such field will be presented and discussed in the paper.

  19. Magnetic field sensor for isotropically sensing an incident magnetic field in a sensor plane

    NASA Technical Reports Server (NTRS)

    Pant, Bharat B. (Inventor); Wan, Hong (Inventor)

    2001-01-01

    A magnetic field sensor that isotropically senses an incident magnetic field. This is preferably accomplished by providing a magnetic field sensor device that has one or more circular shaped magnetoresistive sensor elements for sensing the incident magnetic field. The magnetoresistive material used is preferably isotropic, and may be a CMR material or some form of a GMR material. Because the sensor elements are circular in shape, shape anisotropy is eliminated. Thus, the resulting magnetic field sensor device provides an output that is relatively independent of the direction of the incident magnetic field in the sensor plane.

  20. Magnetic field effects on plasma ionization balance

    SciTech Connect

    Weisheit, J.C.

    1995-12-31

    Magnetic fields give rise to several phenomena that can significantly affect ionization balance in a plasma. Theoretical models commonly used to determine the charge state distribution (viz., ) of ions in non-magnetized plasmas are reviewed first, for both equilibrium and non-equilibrium situations. Then, after a brief survey of laboratory and cosmic plasmas with strong fields, B > 10{sup 6} Gauss, some of the ways such magnetic fields influence are highlighted. Most key problems have yet to be tackled.