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Electric and Magnetic Fields (EMF) RAPID Engineering Program, Project 7: Development of Field Exposure Models
Bracken, T.D.; Rankin, R.F.; Wiley, J.A.
The purpose of this project was to develop a conceptual model for estimating magnetic field (EMF) personal exposure (PE) of individuals or groups and construct a working model using existing data.
EMF in your environment. Magnetic field measurements of everyday electrical devices
Not Available
The publication compares the strength of 60 hertz magnetic fields produced by common electrical items and shows you how their strength diminishes as you move farther away from them. The information presented here has to do with the strength of the magnetic field; however, the authors aren't certain that the strength of the field is the only important consideration. It may turn out that other factors are also important. Future research is likely to reveal that the information given in the publication is only part of the story.
Electric and Magnetic Fields (EMF) RAPID Program Engineering Project 8: FINAL REPORT, Evaluation of Field Reduction Technologies, Volume 1 (Report) and Volume 2 (Appendices)
Commonwealth Associates, Inc.; IIT Research Institute
This draft report consists of two volumes. Volume 1, the main body, contains an introducto~ sectionj an overview of magnetic fields sectio~ and field reduction technology evaluation section. Magnetic field reduction methods are evalpated for transmission lines, distribution Iines,sulxtations, building wiring applkmd machinery, and transportation systems. The evaluation considers effectiveness, co% and other ftiors. Volume 2 contains five appendices, Append~ A presents magnetic field shielding information. Appendices B and C present design assumptions and magnetic field plots for transmission and distribution lines, respectively. Appendices D and E present cost estimate details for transmission and distribution limes, respectively.
Direct torque control of permanent magnet synchronous motors with non-sinusoidal back-EMF
Ozturk, Salih Baris
torque control of permanent magnet synchronous motor (PMSM) with sinusoidal back-EMF is discussed in detail. Secondly, the proposed two-phase conduction mode for DTC of BLDC motors is introduced in the constant torque region. In this control scheme, only...
Magnetic Field Safety Magnetic Field Safety
McQuade, D. Tyler
Magnetic Field Safety Training #12;Magnetic Field Safety Strong Magnetic Fields exist around energized magnets. High magnetic fields alone are a recognized hazard only for personnel with certain medical conditions such as pacemakers, magnetic implants, or embedded shrapnel. In addition, high magnetic
Seattle city light wins EMF lawsuit brought by worker
Warkentin, D. [ed.
Ruling consistent with similar lawsuit outcomes. A Washington state workers` compensation appeals board, in upholding an earlier state agency decision, has ruled that electric and magnetic fields (EMF) did not cause a Seattle City Light worker`s leukemia. The outcome of the case, Pilisuk vs. Seattle City Light, appears to fall in line with decisions in other, similar EMF personal injury lawsuits against electric utilities. Robert Pilisuk, 44, an apprentice and electrician-constructor for Seattle City Light for seven years, died five years ago as a result of acute lymphocytic leukemia. {open_quotes}This was the first thorough examination of the large body of EMF studies by a workers` compensation system,{close_quotes} said Betty Ngan, Seattle assistant city attorney. {open_quotes}The board`s decision is based on the extensive record of testimony taken and an exhaustive review of the studies. The result of this appeal process reflects the state of the science, that there is no proven cause-and -effect relationship between EMF and health effects.{close_quotes}
Electric power high-voltage transmission lines: Design options, cost, and electric and magnetic field levels
Stoffel, J.B.; Pentecost, E.D.; Roman, R.D.; Traczyk, P.A.
This report provides background information about (1) the electric and magnetic fields (EMFs) of high-voltage transmission lines at typical voltages and line configurations and (2) typical transmission line costs to assist on alternatives in environmental documents. EMF strengths at 0 {+-} 200 ft from centerline were calculated for ac overhead lines, and for 345 and 230-kV ac underground line and for a {+-}450-kV dc overhead line. Compacting and height sensitivity factors were computed for the variation in EMFs when line conductors are moved closer or raised. Estimated costs for the lines are presented and discussed so that the impact of using alternative strategies for reducing EMF strengths and the implications of implementing the strategies can be better appreciated.
Electric and Magnetic Fields Facts
This discussion outlines the EMF issue, summarizes the research conducted to date, and describes what Western Area Power Administration is doing to address concerns about EMF.
Magnetic Field Measurement System
Kulesza, Joe; Johnson, Eric; Lyndaker, Aaron; Deyhim, Alex; Waterman, Dave; Blomqvist, K. Ingvar [Advanced Design Consulting USA, 126 Ridge Road, P.O. Box 187, Lansing, NY 14882 (United States); Dunn, Jonathan Hunter [MAX-lab, SE-221 00 Lund (Sweden)
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.
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative1 First Use of Energy for All Purposes (Fuel and Nonfuel), 2002; Level: National5Sales for4,645U.S. DOEThe Bonneville Power AdministrationField Campaign:INEA :Work withJerseyMarketsWhyPressPolicy Doc. ID:call
Low field magnetic resonance imaging
Pines, Alexander (Berkeley, CA); Sakellariou, Dimitrios (Billancourt, FR); Meriles, Carlos A. (Fort Lee, NJ); Trabesinger, Andreas H. (London, GB)
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.
Safety of high speed guided ground transportation systems: Comparison of magnetic and electric fields of conventional and advanced electrified transportation systems. Final report, September 1992-March 1993
Dietrich, F.M.; Feero, W.E.; Jacobs, W.L.
Concerns exist regarding the potential safety, environmental and health effects on the public and on transportation workers due to electrification along new or existing rail corridors, and to proposed maglev and high speed rail operations. Therefore, the characterization of electric and magnetic fields (EMF) produced by both steady (dc) and alternating currents (ac) at power frequency (50 Hz in Europe and 60 Hz in the U.S.) and above, in the Extreme Low Frequency (ELF) range (3-3000 Hz) is of interest. The report summarizes and compares the results of a survey of EMF characteristics (spatial, temporal and frequency bands) for representative conventional railroad and transit and advanced high-speed systems including: the German TR-07 maglev system; the Amtrak Northeast Corridor (NEC) and North Jersey Transit (NJT) trains; the Washington, DC Metrorail (WMATA) and the Boston, MA (MBTA) transit systems; and the French TGV-A high speed rail system. This comprehensive comparative EMF survey produced both detailed data and statistical summaries of EMF profiles, and their variability in time and space. EMF ELF levels for WMATA are also compared to those produced by common environmental sources at home, work, and under power lines, but have specific frequency signatures.
Laboratory Studies of the Effects of Static and Variable Magnetic Fields on Freshwater Fish
Cada, Glenn F [ORNL; Bevelhimer, Mark S [ORNL; Fortner, Allison M [ORNL; Riemer, Kristina P [ORNL; Schweizer, Peter E [ORNL
There is considerable interest in the development of marine and hydrokinetic energy projects in rivers, estuaries, and coastal ocean waters of the United States. Hydrokinetic (HK) technologies convert the energy of moving water in river or tidal currents into electricity, without the impacts of dams and impoundments associated with conventional hydropower or the extraction and combustion of fossil fuels. The Federal Energy Regulatory Commission (FERC) maintains a database that displays the geographical distribution of proposed HK projects in inland and tidal waters (FERC 2012). As of March 2012, 77 preliminary permits had been issued to private developers to study HK projects in inland waters, the development of which would total over 8,000 MW. Most of these projects are proposed for the lower Mississippi River. In addition, the issuance of another 27 preliminary permits for HK projects in inland waters, and 3 preliminary permits for HK tidal projects (totaling over 3,100 MW) were under consideration by FERC. Although numerous HK designs are under development (see DOE 2009 for a description of the technologies and their potential environmental effects), the most commonly proposed projects entail arrays of rotating devices, much like submerged wind turbines, that are positioned in the high-velocity (high energy) river channels. The many diverse HK designs imply a diversity of environmental impacts, but a potential impact common to most is the effect on aquatic organisms of electromagnetic fields (EMF) created by the projects. The submerged electrical generator will emit an EMF into the surrounding water, as will underwater cables used to transmit electricity from the generator to the shore, between individual units in an array (inter-turbine cables), and between the array and a submerged step-up transformer. The electric current moving through these cables will induce magnetic fields in the immediate vicinity, which may affect the behavior or viability of fish and benthic invertebrates (Gill et al. 2005, 2009). It is known that numerous marine and freshwater organisms are sensitive to electrical and magnetic fields, often depending on them for such diverse activities as prey location and navigation (DOE 2009; Normandeau et al. 2011). Despite the wide range of aquatic organisms that are sensitive to EMF and the increasing numbers of underwater electrical transmitting cables being installed in rivers and coastal waters, little information is available to assess whether animals will be attracted, repelled, or unaffected by these new sources of EMF. This knowledge gap is especially significant for freshwater systems, where electrosensitive organisms such as paddlefish and sturgeon may interact with electrical transmission cables. We carried out a series of laboratory experiments to test the sensitivity of freshwater fish and invertebrates to the levels of EMF that are expected to be produced by HK projects in rivers. In this context, EM fields are likely to be emitted primarily by generators in the water column and by transmission cables on or buried in the substrate. The HK units will be located in areas of high-velocity waters that are used as only temporary habitats for most riverine species, so long-term exposure of fish and benthic invertebrates to EMF is unlikely. Rather, most aquatic organisms will be briefly exposed to the fields as they drift downstream or migrate upstream. Because the exposure of most aquatic organisms to EMF in a river would be relatively brief and non-lethal, we focused our investigations on detecting behavioral effects. For example, attraction to the EM fields could result in prolonged exposures to the fields or the HK rotor. On the other hand, avoidance reactions might hinder upstream migrations of fish. The experiments reported here are a continuation of studies begun in FY 2010, which focused on the potential effects of static magnetic fields on snails, clams, and fathead minnows (Cada et al. 2011). Those experiments found little indication that the behaviors of these freshwater species were a
Fast superconducting magnetic field switch
Goren, Yehuda (Mountain View, CA); Mahale, Narayan K. (The Woodlands, TX)
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.
Effects on Freshwater Organisms of Magnetic Fields Associated with Hydrokinetic Turbines
Cada, Glenn F [ORNL; Bevelhimer, Mark S [ORNL; Riemer, Kristina P [ORNL; Turner, Julie W [ORNL
Underwater cables will be used to transmit electricity between turbines in an array (interturbine cables), between the array and a submerged step-up transformer (if part of the design), and from the transformer or array to shore. All types of electrical transmitting cables (as well as the generator itself) will emit EMF into the surrounding water. The electric current will induce magnetic fields in the immediate vicinity, which may affect the behavior or viability of animals. Because direct electrical field emissions can be prevented by shielding and armoring, we focused our studies on the magnetic fields that are unavoidably induced by electric current moving through a generator or transmission cable. These initial experiments were carried out to evaluate whether a static magnetic field, such as would be produced by a direct current (DC) transmitting cable, would affect the behavior of common freshwater fish and invertebrates.
Exposure guidelines for magnetic fields
Miller, G.
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.
Magnetic-field-dosimetry system
Lemon, D.K.; Skorpik, J.R.; Eick, J.L.
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.
Measurements of magnetic field alignment
Kuchnir, M.; Schmidt, E.E.
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.
Are Cluster Magnetic Fields Primordial ?
Robi Banerjee; Karsten Jedamzik
We present results of a detailed and fully non-linear numerical and analytical investigation of magnetic field evolution from the very earliest cosmic epochs to the present. We find that, under reasonable assumptions concerning the efficiency of a putative magnetogenesis era during cosmic phase transitions, surprisingly strong magnetic fields 10^{-13} - 10^{-11} Gauss, on comparatively small scales 100 pc - 10 kpc may survive to the present. Building on prior work on the evolution of magnetic fields during the course of gravitational collapse of a cluster, which indicates that pre-collapse fields of 4\\times 10^{-12} Gauss extant on small scales may suffice to produce clusters with acceptable Faraday rotation measures, we question the widely hold view that cluster magnetic fields may not be entirely of primordial origin.
Determination of Electric-Field, Magnetic-Field, and Electric...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Electric-Field, Magnetic-Field, and Electric-Current Distributions of Infrared Optical Antennas: A Near-Field Determination of Electric-Field, Magnetic-Field, and Electric-Current...
Optical sensor of magnetic fields
Butler, M.A.; Martin, S.J.
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.
Magnetic Resonance Imaging System Based on Earth's Magnetic Field
Stepi?nik, Janez
Magnetic Resonance Imaging System Based on Earth's Magnetic Field Ales Mohoric,1,* Gorazd Planinsic magnetic field can be partly compensated by the receiving coil design and shielding of electromagnetic pick and must be monitored accurately.[8� 10] The importance of NMR in a non-uniform magnetic field
The Plasma Magnet for Deep Space Exploration
Shepherd, Simon
. Expansion is halted by solar wind pressure is in balance with the magnetic pressure from the driven currentsW RF power �Magnetic shielding of spacecraft from high energy solar particles �Magneto-braking in magnetosphere of outer planets �Electrical power generation from back emf on RF field coils from solar plasma
Thermalization in External Magnetic Field
Ali-Akbari, Mohammad
In the AdS/CFT framework meson thermalization in the presence of a constant external magnetic field in a strongly coupled gauge theory has been studied. In the gravitational description the thermalization of mesons corresponds to the horizon formation on the flavour D7-brane which is embedded in the AdS_5 x S^5 background in the probe limit. The apparent horizon forms due to the time-dependent change in the baryon number chemical potential, the injection of baryons in the gauge theory. We will numerically show that the thermalization happens even faster in the presence of the magnetic field on the probe brane. We observe that this reduction in the thermalization time sustains up to a specific value of the magnetic field.
Taylor, C.
D. C. 'Niobium-Titanium Superconducting Material s ', in S.14, 1982 HIGH-FIELD SUPERCONDUCTING ACCELERATOR MAGNETS C.SUMAG-68 HIGH-FIELD SUPERCONDUCTING ACCELERATOR MAGNETS* C.
Turbulence and Magnetic Fields in Clouds
Shantanu Basu
We discuss several categories of models which may explain the IMF, including the possible role of turbulence and magnetic fields.
White, Stephen
Chapter 5 CORONAL MAGNETIC FIELD MEASUREMENTS THROUGH GYRORESONANCE EMISSION Stephen M. White This article reviews the use of gyroresonance emission at radio wavelengths to measure coronal magnetic fields. Keywords: Sun, solar corona, solar magnetic fields, solar radio emission Introduction Since the realization
Magnetic monopole and the nature of the static magnetic field
Xiuqing Huang
We investigate the factuality of the hypothetical magnetic monopole and the nature of the static magnetic field. It is shown from many aspects that the concept of the massive magnetic monopoles clearly is physically untrue. We argue that the static magnetic field of a bar magnet, in fact, is the static electric field of the periodically quasi-one-dimensional electric-dipole superlattice, which can be well established in some transition metals with the localized d-electron. This research may shed light on the perfect unification of magnetic and electrical phenomena.
Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization
Doughty, Frank C. (Plano, TX); Spencer, John E. (Plano, TX)
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.
Magnetic fluid flow phenomena in DC and rotating magnetic fields
Rhodes, Scott E. (Scott Edward), 1981-
An investigation of magnetic fluid experiments and analysis is presented in three parts: a study of magnetic field induced torques in magnetorheological fluids, a characterization and quantitative measurement of properties ...
Discovery of magnetic fields in CPNs
S. Jordan; K. Werner; S. J. O'Toole
For the first time we have directly detected magnetic fields in central stars of planetary nebulae by means of spectro-polarimetry with FORS1 at the VLT. In all four objects of our sample we found kilogauss magnetic fields, in NGC 1360 and LSS1362 with very high significance, while in Abell36 and EGB5 the existence of a magnetic field is probable but with less certainty. This discovery supports the hypothesis that the non-spherical symmetry of most planetary nebulae is caused by magnetic fields in AGB stars. Our high discovery rate demands mechanisms to prevent full conservation of magnetic flux during the transition to white dwarfs.
Baryon onset in a magnetic field
Alexander Haber; Florian Preis; Andreas Schmitt
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.
Transient magnetic field and temperature modeling in large magnet applications
Gurol, H.; Hardy, G.E.; Peck, S.D.; Leung, E. (General Dynamics Corp., San Diego, CA (USA). Space Systems Div.)
This paper discusses a coupled magnetic/thermal model developed to study heat and magnetic field diffusion in conducting materials subject to time-varying external fields. There are numerous applications, both military and commercial. These include: energy storage devices, pulsed power transformers, and electromagnetic launchers. The time scales of interest may range from a magnetic field pulse of a microsecond in an electromagnetic launcher, to hundreds of seconds in an energy storage magnet. The problem can be dominated by either the magnetic field or heat diffusion, depending on the temperature and the material properties of the conductor. In general, heat diffuses much more rapidly in high electrical conductivity materials of cryogenic temperatures. The magnetic field takes longer to diffuse, since screening currents can be rapidly set up which shield the interior of the material from further magnetic field penetration. Conversely, in high resistivity materials, the magnetic field diffuses much more rapidly. A coupled two-dimensional thermal/magnetic model has been developed. The results of this model, showing the time and spatial variation of the magnetic field and temperature, are discussed for the projectile of an electromagnetic launcher.
Bipolar pulse field for magnetic refrigeration
Lubell, Martin S. (Oak Ridge, TN)
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.
Bipolar pulse field for magnetic refrigeration
Lubell, M.S.
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.
Magnetic field topology of accreting white dwarfs
Klaus Reinsch; Fabian Euchner; Klaus Beuermann; Stefan Jordan
We report first results of our systematic investigation of the magnetic field structure of rotating single magnetic white dwarfs and of white dwarfs in magnetic cataclysmic variables. The global magnetic field distributions on the isolated white dwarf HE1045-0908 and the accreting white dwarfs in EF Eri and CP Tuc have been derived from phase-resolved flux and polarization spectra obtained with FORS1 at the ESO VLT using the systematic method of Zeeman tomography.
DC-based magnetic field controller
Kotter, D.K.; Rankin, R.A.; Morgan, J.P.
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.
DC-based magnetic field controller
Kotter, Dale K. (Shelley, ID); Rankin, Richard A. (Ammon, ID); Morgan, John P,. (Idaho Falls, ID)
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.
Primordial Magnetic Fields in False Vacuum Inflation
A. C. Davis; K. Dimopoulos
We show that, during false vacuum inflation, a primordial magnetic field can be created, sufficiently strong to seed the galactic dynamo and generate the observed galactic magnetic fields. Considering the inflaton dominated regime, our field is produced by the Higgs-field gradients, resulting from a grand unified phase transition. The evolution of the field is followed from its creation through to the epoch of structure formation, subject to the relevant constraints. We find that it is possible to create a magnetic field of sufficient magnitude, provided the phase transition occurs during the final 5 e-foldings of the inflationary period.
Magnetic fields in anisotropic relativistic stars
Vladimir Folomeev; Vladimir Dzhunushaliev
Relativistic, spherically symmetric configurations consisting of a gravitating magnetized anisotropic fluid are studied. For such configurations, we obtain static equilibrium solutions with an axisymmetric, poloidal magnetic field produced by toroidal electric currents. The presence of such a field results in small deviations of the shape of the configuration from spherical symmetry. This in turn leads to the modification of an equation for the current and correspondingly to changes in the structure of the internal magnetic field for the systems supported by the anisotropic fluid, in contrast to the case of an isotropic fluid, where such deviations do not affect the magnetic field.
Generation of the magnetic field in jets
V. Urpin
We consider dynamo action under the combined influence of turbulence and large-scale shear in sheared jets. Shear can stretch turbulent magnetic field lines in such a way that even turbulent motions showing mirror symmetry become suitable for generation of a large-scale magnetic field. We derive the integral induction equation governing the behaviour of the mean field in jets. The main result is that sheared jets may generate a large-scale magnetic field if shear is sufficiently strong. The generated mean field is mainly concentrated in a magnetic sheath surrounding the central region of a jet, and it exhibits sign reversals in the direction of the jet axis. Typically, the magnetic field in a sheath is dominated by the component along the jet that can reach equipartition with the kinetic energy of particles, The field in the central region of jets has a more disordered structure.
Graphene Nanoribbon in Sharply Localized Magnetic Fields
Abdulaziz D. Alhaidari; Hocine Bahlouli; Abderrahim El Mouhafid; Ahmed Jellal
We study the effect of a sharply localized magnetic field on the electron transport in a strip (ribbon) of graphene sheet, which allows to give results for the transmission and reflection probability through magnetic barriers. The magnetic field is taken as a single and double delta type localized functions, which are treated later as the zero width limit of gaussian fields. For both field configurations, we evaluate analytically and numerically their transmission and reflection coefficients. The possibility of spacial confinement due to the inhomogeneous field configuration is also investigated.
An EMF Framework for Event-B Developed by
Southampton, University of
API Prover #12;Motivation for Event-B EMF · UML-B reimplementation to give tighter integration Other EMF based models (e.g. UML, Epsilon based) *.bum, *.buc, ... translator UML-B API Marker.... ... Automatically construct rest of URI ... · Project/resource from containing component · List of Names Transient
Permanent magnet edge-field quadrupole
Tatchyn, Roman O. (Mountain View, CA)
Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis.
16,000-rpm Interior Permanent Magnet Reluctance Machine with Brushless Field Excitation
Hsu, J.S.; Burress, T.A.; Lee, S.T.; Wiles, R.H.; Coomer, C.L.; McKeever, J.W.; Adams, D.J.
The reluctance interior permanent magnet (RIPM) motor is currently used by many leading auto manufacturers for hybrid vehicles. The power density for this type of motor is high compared with that of induction motors and switched reluctance motors. The primary drawback of the RIPM motor is the permanent magnet (PM) because during high-speed operation, the fixed PM produces a huge back electromotive force (emf) that must be reduced before the current will pass through the stator windings. This reduction in back-emf is accomplished with a significant direct-axis (d-axis) demagnetization current, which opposes the PM's flux to reduce the flux seen by the stator wires. This may lower the power factor and efficiency of the motor and raise the requirement on the alternate current (ac) power supply; consequently, bigger inverter switching components, thicker motor winding conductors, and heavier cables are required. The direct current (dc) link capacitor is also affected when it must accommodate heavier harmonic currents. It is commonly agreed that, for synchronous machines, the power factor can be optimized by varying the field excitation to minimize the current. The field produced by the PM is fixed and cannot be adjusted. What can be adjusted is reactive current to the d-axis of the stator winding, which consumes reactive power but does not always help to improve the power factor. The objective of this project is to avoid the primary drawbacks of the RIPM motor by introducing brushless field excitation (BFE). This offers both high torque per ampere (A) per core length at low speed by using flux, which is enhanced by increasing current to a fixed excitation coil, and flux, which is weakened at high speed by reducing current to the excitation coil. If field weakening is used, the dc/dc boost converter used in a conventional RIPM motor may be eliminated to reduce system costs. However, BFE supports a drive system with a dc/dc boost converter, because it can further extend the constant power speed range of the drive system and adjust the field for power factor and efficiency gains. Lower core losses at low torque regions, especially at high speeds, are attained by reducing the field excitation. Safety and reliability are increased by weakening the field when a winding short-circuit fault occurs, preventing damage to the motor. For a high-speed motor operating at 16,000-revolutions per minute (rpm), mechanical stress is a challenge. Bridges that link the rotor punching segments together must be thickened for mechanical integrity; consequently, increased rotor flux leakage significantly lowers motor performance. This barrier can be overcome by BFE to ensure sufficient rotor flux when needed.
Magnetic fields in Neutron Stars
Vigan�, Daniele; Miralles, Juan A; Rea, Nanda
Isolated neutron stars show a diversity in timing and spectral properties, which has historically led to a classification in different sub-classes. The magnetic field plays a key role in many aspects of the neutron star phenomenology: it regulates the braking torque responsible for their timing properties and, for magnetars, it provides the energy budget for the outburst activity and high quiescent luminosities (usually well above the rotational energy budget). We aim at unifying this observational variety by linking the results of the state-of-the-art 2D magneto-thermal simulations with observational data. The comparison between theory and observations allows to place two strong constraints on the physical properties of the inner crust. First, strong electrical currents must circulate in the crust, rather than in the star core. Second, the innermost part of the crust must be highly resistive, which is in principle in agreement with the presence of a novel phase of matter so-called nuclear pasta phase.
Magnetic monopole field exposed by electrons
B�ch�, A; Van Tendeloo, G; Verbeeck, J
Magnetic monopoles have provided a rich field of study, leading to a wide area of research in particle physics, solid state physics, ultra-cold gases, superconductors, cosmology, and gauge theory. So far, no true magnetic monopoles were found experimentally. Using the Aharonov-Bohm effect, one of the central results of quantum physics, shows however, that an effective monopole field can be produced. Understanding the effects of such a monopole field on its surroundings is crucial to its observation and provides a better grasp of fundamental physical theory. We realize the diffraction of fast electrons at a magnetic monopole field generated by a nanoscopic magnetized ferromagnetic needle. Previous studies have been limited to theoretical semiclassical optical calculations of the motion of electrons in such a monopole field. Solid state systems like the recently studied 'spin ice' provide a constrained system to study similar fields, but make it impossible to separate the monopole from the material. Free space ...
External-field-free magnetic biosensor
Li, Yuanpeng; Wang, Yi; Klein, Todd; Wang, Jian-Ping, E-mail: email@example.com [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)
In this paper, we report a magnetic nanoparticle (MNP) detection scheme without the presence of any external magnetic field. The proposed magnetic sensor uses a patterned groove structure within the sensor so that no external magnetic field is needed to magnetize the MNPs. An example is given based on a giant magnetoresistance (GMR) sensing device with a spin valve structure. For this structure, the detection of MNPs located inside the groove and near the free layer is demonstrated under no external magnetic field. Micromagnetic simulations are performed to calculate the signal to noise level of this detection scheme. A maximum signal to noise ratio (SNR) of 18.6?dB from one iron oxide magnetic nanoparticle with 8?nm radius is achieved. As proof of concept, this external-field-free GMR sensor with groove structure of 200?nm?�?200?nm is fabricated using a photo and an electron beam integrated lithography process. Using this sensor, the feasibility demonstration of the detection SNR of 9.3?dB is achieved for 30??l magnetic nanoparticles suspension (30?nm iron oxide particles, 1?mg/ml). This proposed external-field-free sensor structure is not limited to GMR devices and could be applicable to other magnetic biosensing devices.
Colour superconductivity in a strong magnetic field
Efrain J. Ferrer; Vivian de la Incera; Cristina Manuel
We explore the effects of an applied strong external magnetic field in a three flavour massless colour superconductor. The long-range component of the B field that penetrates the superconductor enhances some quark condensates, leading to a different condensation pattern. The external field also reduces the flavour symmetries in the system, and thus it changes drastically the corresponding low energy physics. Our considerations are relevant for the study of highly magnetized compact stars.
ECE 390 Electric & Magnetic Fields Catalog Description: Static and quasi-static electric and magnetic fields.
Engineering Magnetics, ECE 593 Structure: Three 80-minute lectures per week Instructors: A. Weisshaar (primaryECE 390 � Electric & Magnetic Fields Catalog Description: Static and quasi-static electric and magnetic fields. Credits: 4 Terms Offered: Fall Prerequisites: MTH 255, ENGR 203 (concurrent enrollment
Discovery of magnetic fields in hot subdwarfs
S. J. O'Toole; S. Jordan; S. Friedrich; U. Heber
We present polarisation measurements of sdB and sdO stars using FORS1 on the VLT. The observations were made as part of a project to determine whether magnetic fields in two super-metal-rich stars can explain their extreme abundance peculiarities. Field strengths of up to ~1.5 kG have been measured at varying levels of significance in each of our six targets, however no clear evidence was found between apparently normal subdwarfs and the metal-rich objects. The origin of the magnetic fields is unknown. We also discuss the implications of our measurements for magnetic flux conservation in late stages of stellar evolution.
Joint HVAC transmission EMF environmental study
Stormshak, F.; Thompson, J. (Oregon State Univ., Corvallis, OR (United States))
This document describes the rationale, procedures, and results of a carefully controlled study conducted to establish whether chronic exposure of female (ewe) Suffolk lambs to the environment of a 500-kV 60-Hz transmission line would affect various characteristics of growth, endocrine function, and reproductive development. This experiment used identical housing and management schemes for control and line-exposed ewes, thus minimizing these factors as contributors to between-group experimental error. Further, throughout the 10-month duration of this study, changes in electric and magnetic fields, audible noise, and weather conditions were monitored continuously by a computerized system. Such measurements provided the opportunity to identify any relationship between environmental factors and biological responses. Because of reports in the literature that electric and magnetic fields alter concentrations of melatonin in laboratory animals, the primary objective of this study was to ascertain whether a similar effect occurs in lambs exposed to a 500-kV a-c line in a natural setting. In addition, onset of puberty, changes in body weight, wool growth, and behavior were monitored. To determine whether the environment of a 500-kV line caused stress in the study animals, serum levels of cortisol were measured. The study was conducted at Bonneville Power Administration's Ostrander Substation near Estacada, Oregon.
About the global magnetic fields of stars
Bychkov, V D; Madej, J
We present a review of observations of the stellar longitudinal (effective) magnetic field ($B_e$) and its properties. This paper also discusses contemporary views on the origin, evolution and structure of $B_e$.
Lunar magnetic field measurements with a cubesat
Garrick-Bethell, Ian
We have developed a mission concept that uses 3-unit cubesats to perform new measurements of lunar magnetic fields, less than 100 meters above the Moon�s surface. The mission calls for sending the cubesats on impact ...
Taylor, C.
D. C. 'Niobium-Titanium Superconducting Material s ', in S.Nb -Ti and Nb3Sn superconductors. , �� ,""" s. S. Clamp, Tie14, 1982 HIGH-FIELD SUPERCONDUCTING ACCELERATOR MAGNETS C.
Magnetic field imaging with atomic Rb vapor
Eugeniy E. Mikhailov; I. Novikova; M. D. Havey; F. A. Narducci
We demonstrate the possibility of dynamic imaging of magnetic fields using electromagnetically induced transparency in an atomic gas. As an experimental demonstration we employ an atomic Rb gas confined in a glass cell to image the transverse magnetic field created by a long straight wire. In this arrangement, which clearly reveals the essential effect, the field of view is about 2 x 2 mm^2 and the field detection uncertainty is 0.14 mG per 10 um x 10 um image pixel.
Laminated magnet field coil sheath
Skaritka, J.R.
A method for manufacturing a magnetic cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible substrate sheath, with the trim coil pattern precisely location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator. 1 fig.
Laminated magnet field coil sheath
Skaritka, John R. (Coram, NY)
a method for manufacturing a magnet cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible sheath, with the trim coil pattern precisely positioned thereon, is accurately positioned at a precise location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator.
Particle decay in Ising field theory with magnetic field
Gesualdo Delfino
The scaling limit of the two-dimensional Ising model in the plane of temperature and magnetic field defines a field theory which provides the simplest illustration of non-trivial phenomena such as spontaneous symmetry breaking and confinement. Here we discuss how Ising field theory also gives the simplest model for particle decay. The decay widths computed in this theory provide the obvious test ground for the numerical methods designed to study unstable particles in quantum field theories discretized on a lattice.
Magnetic nanoparticles for applications in oscillating magnetic field
Peeraphatdit, Chorthip
Enzymatic and thermochemical catalysis are both important industrial processes. However, the thermal requirements for each process often render them mutually exclusive: thermochemical catalysis requires high temperature that denatures enzymes. One of the long-term goals of this project is to design a thermocatalytic system that could be used with enzymatic systems in situ to catalyze reaction sequences in one pot; this system would be useful for numerous applications e.g. conversion of biomass to biofuel and other commodity products. The desired thermocatalytic system would need to supply enough thermal energy to catalyze thermochemical reactions, while keeping the enzymes from high temperature denaturation. Magnetic nanoparticles are known to generate heat in an oscillating magnetic field through mechanisms including hysteresis and relaxational losses. We envisioned using these magnetic nanoparticles as the local heat source embedded in sub-micron size mesoporous support to spatially separate the particles from the enzymes. In this study, we set out to find the magnetic materials and instrumental conditions that are sufficient for this purpose. Magnetite was chosen as the first model magnetic material in this study because of its high magnetization values, synthetic control over particle size, shape, functionalization and proven biocompatibility. Our experimental designs were guided by a series of theoretical calculations, which provided clues to the effects of particle size, size distribution, magnetic field, frequency and reaction medium. Materials of theoretically optimal size were synthesized, functionalized, and their effects in the oscillating magnetic field were subsequently investigated. Under our conditions, the materials that clustered e.g. silica-coated and PNIPAM-coated iron oxides exhibited the highest heat generation, while iron oxides embedded in MSNs and mesoporous iron oxides exhibited the least bulk heating. It is worth noting that the specific loss power of PNIPAM-coated Fe{sub 3}O{sub 4} was peculiarly high, and the heat loss mechanism of this material remains to be elucidated. Since thermocatalysis is a long-term goal of this project, we also investigated the effects of the oscillating magnetic field system for the synthesis of 7-hydroxycoumarin-3-carboxylic acid. Application of an oscillating magnetic field in the presence of magnetic particles with high thermal response was found to effectively increase the reaction rate of the uncatalyzed synthesis of the coumarin derivative compared to the room temperature control.
Plasma heating in a variable magnetic field
Kichigin, G. N., E-mail: firstname.lastname@example.com [Russian Academy of Sciences, Institute of Solar-Terrestrial Physics (Russian Federation)
The problem of particle acceleration in a periodically variable magnetic field that either takes a zero value or passes through zero is considered. It is shown that, each time the field [0]passes through zero, the particle energy increases abruptly. This process can be regarded as heating in the course of which plasma particles acquire significant energy within one field period. This mechanism of plasma heating takes place in the absence of collisions between plasma particles and is analogous to the mechanism of magnetic pumping in collisional plasma considered by Alfven.
Hyperon bulk viscosity in strong magnetic fields
Monika Sinha; Debades Bandyopadhyay
We study the bulk viscosity of neutron star matter including $\\Lambda$ hyperons in the presence of quantizing magnetic fields. Relaxation time and bulk viscosity due to both the non-leptonic weak process involving $\\Lambda$ hyperons and direct Urca processes are calculated here. In the presence of a strong magnetic field of $10^{17}$ G, the hyperon bulk viscosity coefficient is reduced whereas bulk viscosity coefficients due to direct Urca processes are enhanced compared with their field free cases when many Landau levels are populated by protons, electrons and muons.
Discovery of magnetic fields in hot subdwarfs
S. J. O'Toole; S. Jordan; S. Friedrich; U. Heber
We present initial results of a project to measure mean longitudinal magnetic fields in a group of sdB/OB/O stars. The project was inspired by the discovery of three super-metal-rich sdOB stars, each having metals (e.g. Ti, V) enhanced by factors of 10^3 to 10^5. Similar behaviour is observed in chemically peculiar A stars, where strong magnetic fields are responsible for the enrichment. With this in mind, we obtained circularly polarised spectra of two of the super-metal-rich sdOBs, two "normal" sdBs and two sdOs using FORS1 on the ESO/VLT. By examining circular polarisation in the hydrogen Balmer lines and in helium lines, we have detected magnetic fields with strengths of 1-2 kG in most of our targets. This suggests that such fields are relatively common in hot subdwarfs.
Materials Physics Applications: The National High Magnetic Field...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Pulsed Magnetic Field Laboratory of the NHMFL in the form of a 1.4 GVA inertial storage motor-generator for high field pulsed magnets. In addition to the 60 Tesla Long Pulse Magnet...
High magnetic field ohmically decoupled non-contact technology
Wilgen, John (Oak Ridge, TN) [Oak Ridge, TN; Kisner, Roger (Knoxville, TN) [Knoxville, TN; Ludtka, Gerard (Oak Ridge, TN) [Oak Ridge, TN; Ludtka, Gail (Oak Ridge, TN) [Oak Ridge, TN; Jaramillo, Roger (Knoxville, TN) [Knoxville, TN
Methods and apparatus are described for high magnetic field ohmically decoupled non-contact treatment of conductive materials in a high magnetic field. A method includes applying a high magnetic field to at least a portion of a conductive material; and applying an inductive magnetic field to at least a fraction of the conductive material to induce a surface current within the fraction of the conductive material, the surface current generating a substantially bi-directional force that defines a vibration. The high magnetic field and the inductive magnetic field are substantially confocal, the fraction of the conductive material is located within the portion of the conductive material and ohmic heating from the surface current is ohmically decoupled from the vibration. An apparatus includes a high magnetic field coil defining an applied high magnetic field; an inductive magnetic field coil coupled to the high magnetic field coil, the inductive magnetic field coil defining an applied inductive magnetic field; and a processing zone located within both the applied high magnetic field and the applied inductive magnetic field. The high magnetic field and the inductive magnetic field are substantially confocal, and ohmic heating of a conductive material located in the processing zone is ohmically decoupled from a vibration of the conductive material.
Computing nonlinear force free coronal magnetic fields
T. Wiegelmann; T. Neukirch
Knowledge of the structure of the coronal magnetic field is important for our understanding of many solar activity phenomena, e.g. flares and CMEs. However, the direct measurement of coronal magnetic fields is not possible with present methods, and therefore the coronal field has to be extrapolated from photospheric measurements. Due to the low plasma beta the coronal magnetic field can usually be assumed to be approximately force free, with electric currents flowing along the magnetic field lines. There are both observational and theoretical reasons which suggest that at least prior to an eruption the coronal magnetic field is in a nonlinear force free state. Unfortunately the computation of nonlinear force free fields is way more difficult than potential or linear force free fields and analytic solutions are not generally available. We discuss several methods which have been proposed to compute nonlinear force free fields and focus particularly on an optimization method which has been suggested recently. We compare the numerical performance of a newly developed numerical code based on the optimization method with the performance of another code based on an MHD relaxation method if both codes are applied to the reconstruction of a semi-analytic nonlinear force-free solution. The optimization method has also been tested for cases where we add random noise to the perfect boundary conditions of the analytic solution, in this way mimicking the more realistic case where the boundary conditions are given by vector magnetogram data. We find that the convergence properties of the optimization method are affected by adding noise to the boundary data and we discuss possibilities to overcome this difficulty.
Tevzadze, Alexander G. [Faculty of Exact and Natural Sciences, Javakhishvili Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi 0128 (Georgia); Kisslinger, Leonard; Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Brandenburg, Axel, E-mail: firstname.lastname@example.com [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)
We study the evolution of QCD phase transition-generated magnetic fields (MFs) in freely decaying MHD turbulence of the expanding universe. We consider an MF generation model that starts from basic non-perturbative QCD theory and predicts stochastic MFs with an amplitude of the order of 0.02 {mu}G and small magnetic helicity. We employ direct numerical simulations to model the MHD turbulence decay and identify two different regimes: a 'weakly helical' turbulence regime, when magnetic helicity increases during decay, and 'fully helical' turbulence, when maximal magnetic helicity is reached and an inverse cascade develops. The results of our analysis show that in the most optimistic scenario the magnetic correlation length in the comoving frame can reach 10 kpc with the amplitude of the effective MF being 0.007 nG. We demonstrate that the considered model of magnetogenesis can provide the seed MF for galaxies and clusters.
Magnetic field measurements on the sun and implications for stellar magnetic field observations
Sun, W.H.; Giampapa, M.S.; Worden, S.P.
Results of solar magnetic field measurements in plages, sunspot umbrae, and sunspot penumbrae using high spectral resolution, unpolarized infrared H band spectral data are presented. A Fourier deconvolution analysis scheme similar to that utilized for stellar magnetic field measurements is adopted. As an example, a field strength of 3240 + or - 450 G is determined in a sunspot umbra combined with a value of 2000 + or - 180 G in the associated penumbra. These values are compared with a direct measurement of the spot umbra and penumbra field strengths based on the observed separation of the Zeeman components of the magnetically sensitive lines. Possible origins for the discrepancy between the results inferred by these two different techniques are discussed. The Fourier analysis results confirm the widespread occurrence of kilogauss level fields in the solar photosphere. The implications of the solar results for stellar magnetic field measurements are considered. 45 references.
Electric-Field Control of Magnetism Intrinsic magnetoelectric coupling describes the microscopic interaction between magnetic and
Maroncelli, Mark
Electric-Field Control of Magnetism Intrinsic magnetoelectric coupling describes the microscopic interaction between magnetic and electric polarization in a single-phase material. The control of the magnetic of the two interactions. Moderate biaxial compression precipitates local magnetic competition
Sensor for detecting changes in magnetic fields
Praeg, W.F.
A sensor is described for detecting changes in the magnetic field of the equilibrium-field coil of a Tokamak plasma device that comprises a pair of bifilar wires disposed circumferentially, one inside and one outside the equilibrium-field coil. Each is shorted at one end. The difference between the voltages detected at the other ends of the bifilar wires provides a measure of changing flux in the equilibrium-field coil. This difference can be used to detect faults in the coil in time to take action to protect the coil.
Sensor for detecting changes in magnetic fields
Praeg, Walter F. (Palos Park, IL)
A sensor for detecting changes in the magnetic field of the equilibrium-field coil of a Tokamak plasma device comprises a pair of bifilar wires disposed circumferentially, one inside and one outside the equilibrium-field coil. Each is shorted at one end. The difference between the voltages detected at the other ends of the bifilar wires provides a measure of changing flux in the equilibrium-field coil. This difference can be used to detect faults in the coil in time to take action to protect the coil.
Fast field mapping device for cyclotron magnets
Berkes, B.; Brombach, D.; Szavits, O.
The Swiss S.I.N. ring injector cyclotron has four sector magnets. For fast and accurate magnetic field measurements a new type of measuring system has been developed. The magnetic field of the sector magnets is measured in polar coordinates. The standard field map covers a range in radial direction from 240 to 3800 mm and in azimuthal direction from -47 deg. to +47 deg. in steps of 20 mm and 1/4 deg., respectively. Two Hall probes are mounted on a carriage which follows a meandric track. The data are taken in the ''flying'' mode, i.e. two fast DVM's read the values while the carriage is moving at an average speed of approx. 25 cm/sec. The measuring procedure is controlled on line by a small computer and is carried through automatically within roughly 2/one-half/ hr. The process control software contains diagnostic routines for surveying the operation as well as for a smoothing check of the measured data which are written on a magnetic tape at the end of each radial track. 3 refs.
Magnetic fields and density functional theory
Salsbury Jr., Freddie
A major focus of this dissertation is the development of functionals for the magnetic susceptibility and the chemical shielding within the context of magnetic field density functional theory (BDFT). These functionals depend on the electron density in the absence of the field, which is unlike any other treatment of these responses. There have been several advances made within this theory. The first of which is the development of local density functionals for chemical shieldings and magnetic susceptibilities. There are the first such functionals ever proposed. These parameters have been studied by constructing functionals for the current density and then using the Biot-Savart equations to obtain the responses. In order to examine the advantages and disadvantages of the local functionals, they were tested numerically on some small molecules.
Magnetic field-line lengths inside interplanetary magnetic flux ropes
Hu, Qiang; Krucker, Sam
We report on the detailed and systematic study of field-line twist and length distributions within magnetic flux ropes embedded in Interplanetary Coronal Mass Ejections (ICMEs). The Grad-Shafranov reconstruction method is utilized together with a constant-twist nonlinear force-free (Gold-Hoyle) flux rope model to reveal the close relation between the field-line twist and length in cylindrical flux ropes, based on in-situ Wind spacecraft measurements. We show that the field-line twist distributions within interplanetary flux ropes are inconsistent with the Lundquist model. In particular we utilize the unique measurements of magnetic field-line lengths within selected ICME events as provided by Kahler et al. (2011) based on energetic electron burst observations at 1 AU and the associated type III radio emissions detected by the Wind spacecraft. These direct measurements are compared with our model calculations to help assess the flux-rope interpretation of the embedded magnetic structures. By using the differen...
Circular polarization of obliquely propagating whistler wave magnetic field
Bellan, P. M. [Applied Physics, Caltech, Pasadena California 91125 (United States)] [Applied Physics, Caltech, Pasadena California 91125 (United States)
The circular polarization of the magnetic field of obliquely propagating whistler waves is derived using a basis set associated with the wave partial differential equation. The wave energy is mainly magnetic and the wave propagation consists of this magnetic energy sloshing back and forth between two orthogonal components of magnetic field in quadrature. The wave electric field energy is small compared to the magnetic field energy.
Magnetic fields of the W4 superbubble
Gao, X Y; Reich, P; Han, J L; Kothes, R
Superbubbles and supershells are the channels for transferring mass and energy from the Galactic disk to the halo. Magnetic fields are believed to play a vital role in their evolution. We study the radio continuum and polarized emission properties of the W4 superbubble to determine its magnetic field strength. New sensitive radio continuum observations were made at 6 cm, 11 cm, and 21 cm. The total intensity measurements were used to derive the radio spectrum of the W4 superbubble. The linear polarization data were analysed to determine the magnetic field properties within the bubble shells. The observations show a multi-shell structure of the W4 superbubble. A flat radio continuum spectrum that stems from optically thin thermal emission is derived from 1.4 GHz to 4.8 GHz. By fitting a passive Faraday screen model and considering the filling factor fne , we obtain the thermal electron density ne = 1.0/\\sqrt{fne} (\\pm5%) cm^-3 and the strength of the line-of-sight component of the magnetic field B// = -5.0/\\sq...
Measurement of Magnetic Field Using Collaborative AUVs
Idaho, University of
Measurement of Magnetic Field Using Collaborative AUVs Jesse Pentzer, Brendan Crosbie, Thomas Bean, tests using multiple types of AUVs to individually sample bathymetric data and water mass properties, salinity, and temperature data was reported [2]. In 2007, an AUV was equipped to measure water properties
Electro-Mechanical Resonant Magnetic Field Sensor
Temnykh, A B; Temnykh, Alexander B.; Lovelace, Richard V. E.
We describe a new type of magnetic field sensor which is termed an Electro-Mechanical Resonant Sensor (EMRS). The key part of this sensor is a small conductive elastic element with low damping rate and therefore a high Q fundamental mode of frequency $f_1$. An AC current is driven through the elastic element which, in the presence of a magnetic field, causes an AC force on the element. When the frequency of the AC current matches the resonant frequency of the element, maximum vibration of the element occurs and this can be measured precisely by optical means. We have built and tested a model sensor of this type using for the elastic element a length of copper wire of diameter 0.030 mm formed into a loop shape. The wire motion was measured using a light emitting diode photo-transistor assembly. This sensor demonstrated a sensitivity better than 0.001G for an applied magnetic field of $ \\sim 1$G and a good selectivity for the magnetic field direction. The sensitivity can be easily improved by a factor of $\\sim ...
Magnetic Fields in Molecular Cloud Cores
Shantanu Basu
Observations of magnetic field strengths imply that molecular cloud fragments are individually close to being in a magnetically critical state, even though both magnetic field and column density measurements range over two orders of magnitude. The turbulent pressure also approximately balances the self-gravitational pressure. These results together mean that the one-dimensional velocity dispersion $\\sigv$ is proportional to the mean \\Alf speed of a cloud $\\va$. Global models of MHD turbulence in a molecular cloud show that this correlation is naturally satisfied for a range of different driving strengths of the turbulence. For example, an increase of turbulent driving causes a cloud expansion which also increases $\\va$. Clouds are in a time averaged balance but exhibit large oscillatory motions, particularly in their outer rarefied regions. We also discuss models of gravitational fragmentation in a sheet-like region in which turbulence has already dissipated, including the effects of magnetic fields and ion-neutral friction. Clouds with near-critical mass-to-flux ratios lead to subsonic infall within cores, consistent with some recent observations of motions in starless cores. Conversely, significantly supercritical clouds are expected to produce extended supersonic infall.
The measurement and analysis of the magnetic field of a synchrotron light source magnet�
Graf, Udo Werner
In this thesis a unique system is used to measure the magnetic field of a superconducting synchrotron light source magnet. The magnet measured is a superferric dipole C-magnet designed to produce a magnetic field up to 3 Tesla in magnitude. Its...
Primordial magnetic field amplification from turbulent reheating
Calzetta, Esteban [Departamento de F�sica, FCEyN-UBA and IFIBA-CONICET, Cdad. Universitaria, Buenos Aires (Argentina); Kandus, Alejandra, E-mail: firstname.lastname@example.com, E-mail: email@example.com [LATO - DCET - UESC. Rodovia Ilh�us-Itabuna, km 16 s/n, CEP: 45662-900, Salobrinho, Ilh�us-BA (Brazil)
We analyze the possibility of primordial magnetic field amplification by a stochastic large scale kinematic dynamo during reheating. We consider a charged scalar field minimally coupled to gravity. During inflation this field is assumed to be in its vacuum state. At the transition to reheating the state of the field changes to a many particle/anti-particle state. We characterize that state as a fluid flow of zero mean velocity but with a stochastic velocity field. We compute the scale-dependent Reynolds number Re(k), and the characteristic times for decay of turbulence, t{sub d} and pair annihilation t{sub a}, finding t{sub a} << t{sub d}. We calculate the rms value of the kinetic helicity of the flow over a scale L and show that it does not vanish. We use this result to estimate the amplification factor of a seed field from the stochastic kinematic dynamo equations. Although this effect is weak, it shows that the evolution of the cosmic magnetic field from reheating to galaxy formation may well be more complex than as dictated by simple flux freezing.
Journal of Magnetism and Magnetic Materials 281 (2004) 272275 Effects of high magnetic field annealing on texture and
Garmestani, Hamid
Journal of Magnetism and Magnetic Materials 281 (2004) 272275 Effects of high magnetic field annealing on texture and magnetic properties of FePd D.S. Lia, *, H. Garmestania , Shi-shen Yanb , M China c National High Magnetic Field Laboratory, Florida State University, 1800 East Paul Dirac Drive
Magnetic susceptibility and magnetization properties of asymmetric nuclear matter under a strong magnetic field
A. Rabhi; M. A. P�rez-Garc�a; C. Provid�ncia; I. Vida�a
We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields $B \\sim 10^{16} - 10^{17}$ G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for $B > 10^{16}$ G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.
Magnetic Fields in Population III Star Formation
Turk, Matthew J.; Oishi, Jeffrey S.; Abel, Tom; Bryan, Greg
We study the buildup of magnetic fields during the formation of Population III star-forming regions, by conducting cosmological simulations from realistic initial conditions and varying the Jeans resolution. To investigate this in detail, we start simulations from identical initial conditions, mandating 16, 32 and 64 zones per Jeans length, and studied the variation in their magnetic field amplification. We find that, while compression results in some amplification, turbulent velocity fluctuations driven by the collapse can further amplify an initially weak seed field via dynamo action, provided there is sufficient numerical resolution to capture vortical motions (we find this requirement to be 64 zones per Jeans length, slightly larger than, but consistent with previous work run with more idealized collapse scenarios). We explore saturation of amplification of the magnetic field, which could potentially become dynamically important in subsequent, fully-resolved calculations. We have also identified a relatively surprising phenomena that is purely hydrodynamic: the higher-resolved simulations possess substantially different characteristics, including higher infall-velocity, increased temperatures inside 1000 AU, and decreased molecular hydrogen content in the innermost region. Furthermore, we find that disk formation is suppressed in higher-resolution calculations, at least at the times that we can follow the calculation. We discuss the effect this may have on the buildup of disks over the accretion history of the first clump to form as well as the potential for gravitational instabilities to develop and induce fragmentation.
Getting from here to there � energy technology transformation pathways in the EMF-27 scenarios
Krey, Volker; Luderer, Gunnar; Clarke, Leon E.; Kriegler, Elmar
This apper discusses Getting from here to there � energy technology transformation pathways in the EMF-27 scenarios
An EMF Framework for Event-B Developed by
Southampton, University of
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Control of stochasticity in magnetic field lines
Cristel Chandre; Michel Vittot; Guido Ciraolo; Philippe Ghendrih; Ricardo Lima
We present a method of control which is able to create barriers to magnetic field line diffusion by a small modification of the magnetic perturbation. This method of control is based on a localized control of chaos in Hamiltonian systems. The aim is to modify the perturbation locally by a small control term which creates invariant tori acting as barriers to diffusion for Hamiltonian systems with two degrees of freedom. The location of the invariant torus is enforced in the vicinity of the chosen target. Given the importance of confinement in magnetic fusion devices, the method is applied to two examples with a loss of magnetic confinement. In the case of locked tearing modes, an invariant torus can be restored that aims at showing the current quench and therefore the generation of runaway electrons. In the second case, the method is applied to the control of stochastic boundaries allowing one to define a transport barrier within the stochastic boundary and therefore to monitor the volume of closed field lines.
Accretion Discs with Strong Toroidal Magnetic Fields
M. C. Begelman; J. E. Pringle
Simulations and analytic arguments suggest that the turbulence driven by magnetorotational instability (MRI) in accretion discs can amplify the toroidal (azimuthal) component of the magnetic field to a point at which magnetic pressure exceeds the combined gas + radiation pressure in the disc. Arguing from the recent analysis by Pessah and Psaltis, and other MRI results in the literature, we conjecture that the limiting field strength for a thin disc is such that the Alfven speed roughly equals the geometric mean of the Keplerian speed and the gas sound speed. We examine the properties of such magnetically-dominated discs, and show that they resolve a number of outstanding problems in accretion disc theory. The discs would be thicker than standard (Shakura-Sunyaev) discs at the same radius and accretion rate, and would tend to have higher colour temperatures. If they transport angular momentum according to an alpha-prescription, they would be stable against the thermal and viscous instabilities that are found in standard disc models. In discs fuelling active galactic nuclei, magnetic pressure support could also alleviate the restriction on accretion rate imposed by disc self-gravity.
Solar magnetic fields and terrestrial climate
Georgieva, Katya; Kirov, Boian
Solar irradiance is considered one of the main natural factors affecting terrestrial climate, and its variations are included in most numerical models estimating the effects of natural versus anthropogenic factors for climate change. Solar wind causing geomagnetic disturbances is another solar activity agent whose role in climate change is not yet fully estimated but is a subject of intense research. For the purposes of climate modeling, it is essential to evaluate both the past and the future variations of solar irradiance and geomagnetic activity which are ultimately due to the variations of solar magnetic fields. Direct measurements of solar magnetic fields are available for a limited period, but can be reconstructed from geomagnetic activity records. Here we present a reconstruction of total solar irradiance based on geomagnetic data, and a forecast of the future irradiance and geomagnetic activity relevant for the expected climate change.
Fluorescent lamp with static magnetic field generating means
Moskowitz, P.E.; Maya, J.
A fluorescent lamp wherein magnetic field generating means (e.g., permanent magnets) are utilized to generate a static magnetic field across the respective electrode structures of the lamp such that maximum field strength is located at the electrode's filament. An increase in efficacy during operation has been observed. 2 figs.
Localized Magnetic Fields in Arbitrary Directions Using Patterned Nanomagnets
Dunin-Borkowski, Rafal E.
with the option of applying electric fields, for example, to move a quantum dot between regions where the magnetic magnetic films have a long history, for example, in bubble memory,6 but on scales required for spintronic electric fields, for example, to move a quantum dot between regions where the magnetic-field direction
Mapping the magnetic field vector in a fountain clock
Gertsvolf, Marina; Marmet, Louis [National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada)
We show how the mapping of the magnetic field vector components can be achieved in a fountain clock by measuring the Larmor transition frequency in atoms that are used as a spatial probe. We control two vector components of the magnetic field and apply audio frequency magnetic pulses to localize and measure the field vector through Zeeman spectroscopy.
The Use of Small Coolers in a Magnetic Field
Green, Michael A.; Witte, Holger
Small 4 K coolers are used to cool superconducting magnets.These coolers are usually used with high temperature suerconductor (HTS)leads. In most cases, magnet is shielded with iron or active shieldcoils. Thus the field at the cooler is low. There are instances when thecooler must be in a magnetic field. Gifford McMahon (GM) coolers or pulsetube coolers are commercially available to cool the magnets. This paperwill discuss how the two types of coolers are affected by the straymagnetic field. Strategies for using coolers on magnets that generatestray magnetic fields are discussed.
On the control of solidification using magnetic fields and magnetic field Baskar Ganapathysubramanian and Nicholas Zabaras1
Zabaras, Nicholas J.
On the control of solidification using magnetic fields and magnetic field gradients Baskar and Aerospace Engineering, 188 Frank H.T. Rhodes Hall, Cornell University, Ithaca, NY 14853-3801, USA Abstract solidified material can be suitably affected. Most of the magnetic field approaches to melt flow control rely
Magnetic helicity generation from the cosmic axion field
Campanelli, L.; Giannotti, M. [Dipartimento di Fisica, Universita di Ferrara, I-44100 Ferrara (Italy); INFN-Sezione di Ferrara, I-44100 Ferrara (Italy)
The coupling between a primordial magnetic field and the cosmic axion field generates a helical component of the magnetic field around the time in which the axion starts to oscillate. If the energy density of the seed magnetic field is comparable to the energy density of the universe at that time, then the resulting magnetic helicity is about vertical bar H{sub B} vertical bar {approx_equal}(10{sup -20}G){sup 2} kpc and remains constant after its generation. As a corollary, we find that the standard properties of the oscillating axion remain unchanged even in the presence of very strong magnetic fields.
Magnetic Helicity Generation from the Cosmic Axion Field
L. Campanelli; M. Giannotti
The coupling between a primordial magnetic field and the cosmic axion field generates a helical component of the magnetic field around the time in which the axion starts to oscillate. If the energy density of the seed magnetic field is comparable to the energy density of the universe at that time, then the resulting magnetic helicity is about |H_B| \\simeq (10^{-20} G)^2 kpc and remains constant after its generation. As a corollary, we find that the standard properties of the oscillating axion remain unchanged even in the presence of very strong magnetic fields.
Magnetic Field Evolution in Superconducting Neutron Stars
Graber, Vanessa; Glampedakis, Kostas; Lander, Samuel K
The presence of superconducting and superfluid components in the core of mature neutron stars calls for the rethinking of a number of key magnetohydrodynamical notions like resistivity, the induction equation, magnetic energy and flux-freezing. Using a multi-fluid magnetohydrodynamics formalism, we investigate how the magnetic field evolution is modified when neutron star matter is composed of superfluid neutrons, type-II superconducting protons and relativistic electrons. As an application of this framework, we derive an induction equation where the resistive coupling originates from the mutual friction between the electrons and the vortex/fluxtube arrays of the neutron and proton condensates. The resulting induction equation allows the identification of two timescales that are significantly different from those of standard magnetohydrodynamics. The astrophysical implications of these results are briefly discussed.
The origin, evolution and signatures of primordial magnetic fields
Subramanian, Kandaswamy
The universe is magnetized on all scales probed so far. On the largest scales, galaxies and galaxy clusters host magnetic fields at the micro Gauss level coherent on scales up to ten kpc. Recent observational evidence suggests that even the intergalactic medium in voids could host a weak $\\sim 10^{-16}$ Gauss magnetic field, coherent on Mpc scales. An intriguing possibility is that these observed magnetic fields are a relic from the early universe, albeit one which has been subsequently amplified and maintained by a dynamo in collapsed objects. We review here the origin, evolution and signatures of primordial magnetic fields. After a brief summary of magnetohydrodynamics in the expanding universe, we turn to magnetic field generation during inflation and other phase transitions. We trace the linear and nonlinear evolution of the generated primordial fields through the radiation era, including viscous effects. Sensitive observational signatures of primordial magnetic fields on the cosmic microwave background, ...
Graphene transparency in weak magnetic fields
David Valenzuela; Sa�l Hern�ndez-Ortiz; Marcelo Loewe; Alfredo Raya
We carry out an explicit calculation of the vacuum polarization tensor for an effective low-energy model of monolayer graphene in the presence of a weak magnetic field of intensity $B$ perpendicularly aligned to the membrane. By expanding the quasiparticle propagator in the Schwinger proper time representation up to order $(eB)^2$, where $e$ is the unit charge, we find an explicitly transverse tensor, consistent with gauge invariance. Furthermore, assuming that graphene is radiated with monochromatic light of frequency $\\omega$ along the external field direction, from the modified Maxwell's equations we derive the intensity of transmitted light and the angle of polarization rotation in terms of the longitudinal ($\\sigma_{xx}$) and transverse ($\\sigma_{xy}$) conductivities. Corrections to these quantities, both calculated and measured, are of order $(eB)^2/\\omega^4$. Our findings generalize and complement previously known results reported in literature regarding the light absorption problem in graphene from the experimental and theoretical points of view, with and without external magnetic fields.
Rotating-frame gradient fields for magnetic resonance imaging and nuclear magnetic resonance in low fields
Bouchard, Louis-Serge; Pines, Alexander; Demas, Vasiliki
A system and method for Fourier encoding a nuclear magnetic resonance (NMR) signal is disclosed. A static magnetic field B.sub.0 is provided along a first direction. An NMR signal from the sample is Fourier encoded by applying a rotating-frame gradient field B.sub.G superimposed on the B.sub.0, where the B.sub.G comprises a vector component rotating in a plane perpendicular to the first direction at an angular frequency .omega.in a laboratory frame. The Fourier-encoded NMR signal is detected.
Magnetic fields in relativistic collisionless shocks
Santana, Rodolfo; Kumar, Pawan [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Barniol Duran, Rodolfo, E-mail: email@example.com, E-mail: email@example.com, E-mail: email@example.com [Racah Institute for Physics, The Hebrew University, Jerusalem 91904 (Israel)
We present a systematic study on magnetic fields in gamma-ray burst (GRB) external forward shocks (FSs). There are 60 (35) GRBs in our X-ray (optical) sample, mostly from Swift. We use two methods to study ? {sub B} (fraction of energy in magnetic field in the FS): (1) for the X-ray sample, we use the constraint that the observed flux at the end of the steep decline is ? X-ray FS flux; (2) for the optical sample, we use the condition that the observed flux arises from the FS (optical sample light curves decline as ?t {sup �1}, as expected for the FS). Making a reasonable assumption on E (jet isotropic equivalent kinetic energy), we converted these conditions into an upper limit (measurement) on ? {sub B} n {sup 2/(p+1)} for our X-ray (optical) sample, where n is the circumburst density and p is the electron index. Taking n = 1 cm{sup �3}, the distribution of ? {sub B} measurements (upper limits) for our optical (X-ray) sample has a range of ?10{sup �8}-10{sup �3} (?10{sup �6}-10{sup �3}) and median of ?few � 10{sup �5} (?few � 10{sup �5}). To characterize how much amplification is needed, beyond shock compression of a seed magnetic field ?10 ?G, we expressed our results in terms of an amplification factor, AF, which is very weakly dependent on n (AF?n {sup 0.21}). The range of AF measurements (upper limits) for our optical (X-ray) sample is ?1-1000 (?10-300) with a median of ?50 (?50). These results suggest that some amplification, in addition to shock compression, is needed to explain the afterglow observations.
Optical pumping magnetic resonance in high magnetic fields: Characterization of nuclear relaxation during pumping
Augustine, Mathew P.
Optical pumping magnetic resonance in high magnetic fields: Characterization of nuclear relaxation during pumping Matthew P. Augustine and Kurt W. Zilm Department of Chemistry, Yale University, New Haven exchange with optically pumped Rb vapor is investigated in high magnetic field. Operation in a high field
Electric shock and elevated EMF levels due to triplen harmonics
Tran, T.Q.; Conrad, L.E.; Stallman, B.K. [PSI Energy, Inc., Plainfield, IN (United States)] [PSI Energy, Inc., Plainfield, IN (United States)
The increasing use of single phase rectifiers for electric power conversion in residential applications increases harmonic load on utility systems. Many papers have analyzed the effect of these loads on power quality and equipment loadability. However, there are two more critical concerns for harmonic loads served phase to neutral on multi-grounded wye systems. Triplen harmonics, particularly the third, add in the neutral and have little diversity between loads. The higher neutral currents may cause significant problems. Neutral to earth voltages will increase near the substations which could increase stray voltage complaints. The additional neutral current on three phase lines will elevate EMF levels especially in the fringe areas. This paper provides fundamental understanding of triplen harmonic influence on stray voltage and EMF related to multi-grounded wye electric distribution systems.
Large-scale magnetic fields in the inflationary universe
Kazuharu Bamba; Misao Sasaki
The generation of large-scale magnetic fields is studied in inflationary cosmology. We consider the violation of the conformal invariance of the Maxwell field by dilatonic as well as non-minimal gravitational couplings. We derive a general formula for the spectrum of large-scale magnetic fields for a general form of the coupling term and the formula for the spectral index. The result tells us clearly the (necessary) condition for the generation of magnetic fields with sufficiently large amplitude.
Magnetic Fields in Quasar Cores II
G. B. Taylor
Multi-frequency polarimetry with the Very Long Baseline Array (VLBA) telescope has revealed absolute Faraday Rotation Measures (RMs) in excess of 1000 rad/m/m in the central regions of 7 out of 8 strong quasars studied (e.g., 3C 273, 3C 279, 3C 395). Beyond a projected distance of ~20 pc, however, the jets are found to have |RM| < 100 rad/m/m. Such sharp RM gradients cannot be produced by cluster or galactic-scale magnetic fields, but rather must be the result of magnetic fields organized over the central 1-100 pc. The RMs of the sources studied to date and the polarization properties of BL Lacs, quasars and galaxies are shown to be consistent so far with the predictions of unified schemes. The direct detection of high RMs in these quasar cores can explain the low fractional core polarizations usually observed in quasars at centimeter wavelengths as the result of irregularities in the Faraday screen on scales smaller than the telescope beam. Variability in the RM of the core is reported for 3C 279 between observations taken 1.5 years apart, indicating that the Faraday screen changes on that timescale, or that the projected superluminal motion of the inner jet components samples a new location in the screen with time. Either way, these changes in the Faraday screen may explain the dramatic variability in core polarization properties displayed by quasars.
Improving magnet designs with high and low field regions
Bj�rk, R; Smith, A; Pryds, N
A general scheme for increasing the difference in magnetic flux density between a high and a low magnetic field region by removing unnecessary magnet material is presented. This is important in, e.g., magnetic refrigeration where magnet arrays has to deliver high field regions in close proximity to low field regions. Also, a general way to replace magnet material with a high permeability soft magnetic material where appropriate is discussed. As an example these schemes are applied to a two dimensional concentric Halbach cylinder design resulting in a reduction of the amount of magnet material used by 42% while increasing the difference in flux density between a high and a low field region by 45%.
Neutron scattering in magnetic fields (*) W. C. Koehler
Boyer, Edmond
691 Neutron scattering in magnetic fields (*) W. C. Koehler Solid State Division, Oak Ridge. Abstract 2014 The use of magnetic fields in neutron scattering experimentation is reviewed briefly. Two of the scattering sample ; in the second the field acts on the neutron itself. Several examples are discussed
Magnetic Propulsion of Intense Lithium Streams in a Tokamak Magnetic Field
Zakharov, Leonid E.
Magnetic Propulsion of Intense Lithium Streams in a Tokamak Magnetic Field Leonid E. Zakharov the theory of magnetic propulsion of liquid lithium streams and their stability in tokamaks takes into account the propulsion e#11;ect, viscosity and the drag force due to magnetic pumping
Baryon magnetic moments in the background field method
Lee, F X; Zhou, L; Wilcox, W
We present a calculation of the magnetic moments for the baryon octet and decuplet using the background-field method and standard Wilson gauge and fermion actions in the quenched approximation of lattice QCD. Progressively smaller static magnetic fields are introduced on a $24^4$ lattice at beta=6.0 and the pion mass is probed down to about 500 MeV. Magnetic moments are extracted from the linear response of the masses to the background field.
Baryon magnetic moments in the external field method
Lee, F X; Zhou, L; Wilcox, W
We present a calculation of the magnetic moments of the baryon octet and decuplet using the external field method and standard Wilson gauge and fermion actions in the quenched approximation. Progressively smaller static magnetic fields are introduced on a $24^4$ latticeat beta=6.0 and the pion mass is probed down to about 500 MeV. Magnetic moments are extracted from the linear response of the masses to the external field.
Temperature compensated current sensor using reference magnetic field
Yakymyshyn, Christopher Paul (Seminole, FL); Brubaker, Michael Allen (Loveland, CO); Yakymyshyn, Pamela Jane (Seminole, FL)
A method is described to provide temperature compensation and self-calibration of a current sensor based on a plurality of magnetic field sensors positioned around a current carrying conductor. A reference magnetic field generated within the current sensor housing is detected by a separate but identical magnetic field sensor and is used to correct variations in the output signal due to temperature variations and aging.
The St�ckelberg Holographic Superconductors in Constant External Magnetic Field
Jian-Pin Wu
We investigate the St\\"{u}ckelberg holographic superconductor in present of the constant external magnetic field. We observe that a critical value of magnetic field exists as the cases in usual holographic superconductor. Furthermore, we find that the applied magnetic field strongly influence the phase transition of this model and have a jump in the condensate at the critical temperature even for $c_{4}=1$.
Static magnetic field concentration and enhancement using magnetic materials with positive permeability
Sun, F
In this paper a novel compressor for static magnetic fields is proposed based on finite embedded transformation optics. When the DC magnetic field passes through the designed device, the magnetic field can be compressed inside the device. After it passes through the device, one can obtain an enhanced static magnetic field behind the output surface of the device (in a free space region). We can also combine our compressor with some other structures to get a higher static magnetic field enhancement in a free space region. In contrast with other devices based on transformation optics for enhancing static magnetic fields, our device is not a closed structure and thus has some special applications (e.g., for controlling magnetic nano-particles for gene and drag delivery). The designed compressor can be constructed by using currently available materials or DC meta-materials with positive permeability. Numerical simulation verifies good performance of our device.
Electrostatic and Magnetic Fields in Bilayer Graphene
Ahmed Jellal; Ilham Redouani; Hocine Bahlouli
We compute the transmission probability through rectangular potential barriers and p-n junctions in the presence of a magnetic and electric fields in bilayer graphene taking into account the full four bands of the energy spectrum. For energy E higher than the interlayer coupling $\\gamma_1 (E>\\gamma_1)$ two propagation modes are available for transport giving rise to four possible ways for transmission and reflection probabilities. However, when the energy is less then the height of the barrier the Dirac fermions exhibits transmission resonances and only one mode of propagation is available. We study the effect of the interlayer electrostatic potential $\\delta$ and the different geometry parameters of the barrier on the transmission probability.
Mitigated-force carriage for high magnetic field environments
Ludtka, Gerard M; Ludtka, Gail M; Wilgen, John B; Murphy, Bart L
A carriage for high magnetic field environments includes a first work-piece holding means for holding a first work-piece, the first work-piece holding means being disposed in an operable relationship with a work-piece processing magnet having a magnetic field strength of at least 1 Tesla. The first work-piece holding means is further disposed in operable connection with a second work-piece holding means for holding a second work-piece so that, as the first work-piece is inserted into the magnetic field, the second work-piece is simultaneously withdrawn from the magnetic field, so that an attractive magnetic force imparted on the first work-piece offsets a resistive magnetic force imparted on the second work-piece.
Microstructural Modification of a Cast Iron by Magnetic Field Processing
Kenik, Edward A [ORNL; Ludtka, Gail Mackiewicz- [ORNL; Ludtka, Gerard Michael [ORNL; Wilgen, John B [ORNL; Kisner, Roger A [ORNL
The current study deals with the microstructural modification of a nodular cast iron during solidification under the influence of high magnetic fields (up to 18 tesla).
Heat pulse propagation in chaotic three-dimensional magnetic fields
Del-Castillo-Negrete, Diego [Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Blazevski, Daniel [Institute for Mechanical Systems, ETH, Zurich (Switzerland)
Heat pulse propagation in three-dimensional chaotic magnetic fields is studied by numerically solving the parallel heat transport equation using a Lagrangian Green's function (LG) method. The main two problems addressed are: the dependence of the radial transport of heat pulses on the level of magnetic field stochasticity (controlled by the amplitude of the magnetic field perturbation, ?), and the role of reversed shear magnetic field configurations on heat pulse propagation. The role of separatrix reconnection of resonant modes in the shear reversal region, and the role of shearless Cantori in the observed phenomena are also discussed.
Coulomb law and energy levels in a superstrong magnetic field
Vysotsky, M I
Analytical expression for the Coulomb potential in the presence of superstrong magnetic field is derived. Structure of hydrogen levels originating from LLL is analyzed.
Entanglement of two-qubit photon beam by magnetic field
A. D. Levin; D. M. Gitman; R. C. Castro
We have studied the possibility of affecting the entanglement measure of 2-qubit system consisting of two photons with different fixed frequencies but with two arbitrary linear polarizations, moving in the same direction, by the help of an applied external magnetic field. The interaction between the magnetic field and the photons in our model is achieved through intermediate electrons that interact with both the photons and the magnetic field. The possibility of exact theoretical analysis of this scheme is based on known exact solutions that describe the interaction of an electron subjected to an external magnetic field (or a medium of electrons not interacting with each other) with a quantized field of two photons. We adapt these exact solutions to the case under consideration. Using explicit wave functions for the resulting electromagnetic field, we calculate the entanglement measure of the photon beam as a function of the applied magnetic field and parameters of the electron medium.
Development and applications of NMR (nuclear magnetic resonance) in low fields and zero field
Bielecki, A.
This dissertation is about nuclear magnetic resonance (NMR) spectroscopy in the absence of applied magnetic fields. NMR is usually done in large magnetic fields, often as large as can be practically attained. The motivation for going the opposite way, toward zero field, is that for certain types of materials, particularly powdered or polycrystalline solids, the NMR spectra in zero field are easier to interpret than those obtained in high field. 92 refs., 60 figs., 1 tab.
Observation of low magnetic field density peaks in helicon plasma
Barada, Kshitish K.; Chattopadhyay, P. K.; Ghosh, J.; Kumar, Sunil; Saxena, Y. C. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)
Single density peak has been commonly observed in low magnetic field (<100 G) helicon discharges. In this paper, we report the observations of multiple density peaks in low magnetic field (<100 G) helicon discharges produced in the linear helicon plasma device [Barada et al., Rev. Sci. Instrum. 83, 063501 (2012)]. Experiments are carried out using argon gas with m = +1 right helical antenna operating at 13.56 MHz by varying the magnetic field from 0 G to 100 G. The plasma density varies with varying the magnetic field at constant input power and gas pressure and reaches to its peak value at a magnetic field value of {approx}25 G. Another peak of smaller magnitude in density has been observed near 50 G. Measurement of amplitude and phase of the axial component of the wave using magnetic probes for two magnetic field values corresponding to the observed density peaks indicated the existence of radial modes. Measured parallel wave number together with the estimated perpendicular wave number suggests oblique mode propagation of helicon waves along the resonance cone boundary for these magnetic field values. Further, the observations of larger floating potential fluctuations measured with Langmuir probes at those magnetic field values indicate that near resonance cone boundary; these electrostatic fluctuations take energy from helicon wave and dump power to the plasma causing density peaks.
Measuring and shimming the magnetic field of a 4 Tesla MRI magnet
Kyriazis, Georgios
The Biomedical Magnetic Resonance Laboratory (BMRL) of the University of Illinois at Urbana-Champaign (UIUC) has ordered from the Texas Accelerator Center (TAC) a superconducting, self-shielded, solenoidal magnet with a maximum field of 4 Tesla...
Magnetic field-induced phase transformation & power harvesting capabilities in magnetic shape memory alloys
Basaran, Burak
Magnetic Shape Memory Alloys (MSMAs) combine shape-change/deformationrecovery abilities of heat driven conventional shape memory alloys (SMA) and magnetic field driven magnetostrictives through martensitic transformation. They are promising...
Understanding magnetic field reversal mechanisms in mesoscopic magnetic multilayer ring structures
Ng, Bryan
Patterned pseudo spin-valve rings show great promise for device applications due to their non-volatility and variety of stable magnetic states. However, the magnetic reversal of these elements under an applied field is ...
Laboratory Studies of the Short-term Responses of Freshwater Fish to Electromagnetic Fields
Bevelhimer, Mark S [ORNL; Cada, Glenn F [ORNL; Fortner, Allison M [ORNL; Schweizer, Peter E [ORNL; Riemer, Kristina P [ORNL
Hydrokinetic energy technologies are being proposed as an environmentally preferred means of generating electricity from river and tidal currents. Among the potential issues that must be investigated in order to resolve environmental concerns are the effects on aquatic organisms of electromagnetic fields created by underwater generators and transmission cables. The behavioral responses of common freshwater fishes to static and variable electromagnetic fields (EMF) that may be emitted by hydrokinetic projects were evaluated in laboratory experiments. Various fish species were exposed to either static (DC) EMF fields created by a permanent bar magnet or variable (AC) EMF fields created by a switched electromagnet for 48 h, fish locations were recorded with a digital imaging system, and changes in activity level and distribution relative to the magnet position were quantified at 5-min intervals. Experiments with fathead minnows, redear sunfish, striped bass, lake sturgeon, and channel catfish produced mixed results. Except for fathead minnows there was no effect on activity level. Only redear sunfish and channel catfish exhibited a change in distribution relative to the position of the magnet with an apparent attraction to the EMF source. In separate experiments, rapid behavioral responses of paddlefish and lake sturgeon to onset of the AC field were recorded with high-speed video. Paddlefish did not react to a variable, 60-Hz magnetic field like that which would be emitted by an AC generator or cable, but lake sturgeon consistently responded to the variable, AC-generated magnetic field with a variety of altered swimming behaviors. These results will be useful for determining under what circumstances cables or generators need to be positioned to minimize interactions with sensitive species.
Nuclear magnetic absorption line widths in weak magnetic fields with a Robinson oscillator
Flugum, Timothy Lee
NUCLEAR MAGNETIC ABSORPTION LINE WIDTHS IN WEAK MAGNETIC FIELDS WITH A ROBINSON OSCILLATOR A Thesis by TIMOTHY LEE FLUGUM Subnntted to the Graduate College of Texas ARM University in partial fulfillment of the requirement for the degree... of MASTER OF SCIENCE August 19SI Major Subject: Physics NUCLEAR MAGNETIC ABSORPTION LINE WIDTHS IN WEAK MAGNETIC FIELDS WITH A ROBINSON OSCILLATOR A Thesis TIMOTHY LEE FLUGUM Approved as to style and content by: Nelson M. Duller (Chairman...
Development of magnetic separation methods of analysis: magnetic field flow fractionation
Garcia-Ramirez, Jaime
DEVELOPMENT OF MAGNETIC SEPARATION METHODS OF ANALYSIS: MAGNETIC FIELD FLOW FRACTIONATION A Thesis by JAIME GARCIA-RAMIREZ Submitted to the Graduate College of Texas A&M University in partial fulfillment of the requirement for the degree... of MASTER OF SCIENCE August 1980 Major Subject: Chemistry DEVELOPMENT OF MAGNETIC SEPARATION METHODS OF ANALYSIS: MAGNETIC FIELD FLOW FRACTIONATION A Thesis by JAIME GARCIA-RAMIREZ Approved as to style and content by: (Chairman of Committee) 1...
High magnetic field processing of liquid crystalline polymers
Smith, Mark E. (Los Alamos, NM); Benicewicz, Brian C. (Los Alamos, NM); Douglas, Elliot P. (Los Alamos, NM)
A process of forming bulk articles of oriented liquid crystalline thermoset material, the material characterized as having an enhanced tensile modulus parallel to orientation of an applied magnetic field of at least 25 percent greater than said material processed in the absence of a magnetic field, by curing a liquid crystalline thermoset precursor within a high strength magnetic field of greater than about 2 Tesla, is provided, together with a resultant bulk article of a liquid crystalline thermoset material, said material processed in a high strength magnetic field whereby said material is characterized as having a tensile modulus parallel to orientation of said field of at least 25 percent greater than said material processed in the absence of a magnetic field.
High magnetic field processing of liquid crystalline polymers
Smith, M.E.; Benicewicz, B.C.; Douglas, E.P.
A process of forming bulk articles of oriented liquid crystalline thermoset material, the material characterized as having an enhanced tensile modulus parallel to orientation of an applied magnetic field of at least 25 percent greater than said material processed in the absence of a magnetic field, by curing a liquid crystalline thermoset precursor within a high strength magnetic field of greater than about 2 Tesla, is provided, together with a resultant bulk article of a liquid crystalline thermoset material, said material processed in a high strength magnetic field whereby said material is characterized as having a tensile modulus parallel to orientation of said field of at least 25 percent greater than said material processed in the absence of a magnetic field.
Including stereoscopic information in the reconstruction of coronal magnetic fields
T. Wiegelmann; T. Neukirch
We present a method to include stereoscopic information about the three dimensional structure of flux tubes into the reconstruction of the coronal magnetic field. Due to the low plasma beta in the corona we can assume a force free magnetic field, with the current density parallel to the magnetic field lines. Here we use linear force free fields for simplicity. The method uses the line of sight magnetic field on the photosphere as observational input. The value of $\\alpha$ is determined iteratively by comparing the reconstructed magnetic field with the observed structures. The final configuration is the optimal linear force solution constrained by both the photospheric magnetogram and the observed plasma structures. As an example we apply our method to SOHO MDI/EIT data of an active region. In the future it is planned to apply the method to analyse data from the SECCHI instrument aboard the STEREO mission.
Magnetic-field-induced antiferromagnetism in the Kondo lattice
Beach, Kevin S. D. (Kevin Stuart David), 1975-
The half-filled Kondo lattice model, augmented by a Zeeman term, serves as a useful model of a Kondo insulator in an applied magnetic field. A variational mean field analysis of this system on a square lattice, backed up ...
Field quality measurements of a 2-Tesla transmission line magnet
Velev, G.V.; Foster, W.; Kashikhin, V.; Mazur, P.; Oleck, A.; Piekarz, H.; Schlabach, P.; Sylvester, C.; /Fermilab; Wake, M.; /KEK, Tsukuba
A prototype 2-Tesla superconducting transmission line magnet for future hadron colliders was designed, built and tested at Fermilab. The 1.5 m long, combined-function gradient-dipole magnet has a vertical pole aperture of 20 mm. To measure the magnetic field quality in such a small magnet aperture, a specialized rotating coil of 15.2 mm diameter, 0.69 m long was fabricated. Using this probe, a program of magnetic field quality measurements was successfully performed. Results of the measurements are presented and discussed.
Developments in deep brain stimulation using time dependent magnetic fields
Crowther, L.J.; Nlebedim, I.C.; Jiles, D.C.
The effect of head model complexity upon the strength of field in different brain regions for transcranial magnetic stimulation (TMS) has been investigated. Experimental measurements were used to verify the validity of magnetic field calculations and induced electric field calculations for three 3D human head models of varying complexity. Results show the inability for simplified head models to accurately determine the site of high fields that lead to neuronal stimulation and highlight the necessity for realistic head modeling for TMS applications.
Earth's Magnetic Field Measurements for the LCLS Undulators
Hacker, Kirsten
Measurements of the earth's magnetic field at several locations at SLAC were conducted to determine the possible field error contribution from tuning the undulators in a location with a different magnetic field than that which will be found in the undulator hall. An average difference of 0.08 {+-} 0.04 Gauss has been measured between the downward earth's field components in the test facility and SLAC tunnel locations.
Sidewall containment of liquid metal with vertical alternating magnetic fields
Lari, Robert J. (Aurora, IL); Praeg, Walter F. (Palos Park, IL); Turner, Larry R. (Naperville, IL); Battles, James E. (Oak Forest, IL); Hull, John R. (Hinsdale, IL); Rote, Donald M. (Lagrange, IL)
An apparatus for containing molten metal using a magnet producing vertical alternating magnetic field positioned adjacent the area in which the molten metal is to be confined. This invention can be adapted particularly to the casting of metal between counter-rotating rollers with the vertical alternating magnetic field used to confine the molten metal at the edges of the rollers. Alternately, the vertical alternating magnetic field can be used as a flow regulator in casting molten metal from an opening in a channel.
Dynamical Electron Mass in a Strong Magnetic Field
S. -Y. Wang
Motivated by recent interest in understanding properties of strongly magnetized matter, we study the dynamical electron mass generated through approximate chiral symmetry breaking in QED in a strong magnetic field. We reliably calculate the dynamical electron mass by numerically solving the nonperturbative Schwinger-Dyson equations in a consistent truncation within the lowest Landau level approximation. It is shown that the generation of dynamical electron mass in a strong magnetic field is significantly enhanced by the perturbative electron mass that explicitly breaks chiral symmetry in the absence of a magnetic field.
Submillimeter Polarimetry and the Galactic Center Magnetic Field
Novak, Giles
Submillimeter Polarimetry and the Galactic Center Magnetic Field D.T. Chuss NASA Goddard Space Flight Center C.D. Dowell Jet Propulsion Laboratory R.H. Hildebrand University of Chicago G. Novak that of the magnetic field. In addition, we present new Hertz data on the Dust Ridge, an arched structure
Magnetic field modulated dust streams from Jupiter in Interplanetary space
Hamilton, Douglas P.
Magnetic field modulated dust streams from Jupiter in Interplanetary space Alberto Flandes Ciencias�es-Galicia Ciencias Espaciales, Instituto de Geof�isica, UNAM, M�exico. Linda Spilker Jet Propulsion Laboratory is sufficient to allow the planet's magnetic field to accelerate them away from the planet where
Complementary bowtie aperture for localizing and enhancing optical magnetic field
Xu, Xianfan
Complementary bowtie aperture for localizing and enhancing optical magnetic field Nan Zhou, Edward, 2011 Nanoscale bowtie antenna and bowtie aperture antenna have been shown to generate strongly enhanced. In this Letter, we discuss the enhancement of magnetic field intensity of nanoscale complementary bowtie aperture
Magnetic helicity evolution in a periodic domain with imposed field
Axel Brandenburg; William H. Matthaeus
In helical hydromagnetic turbulence with an imposed magnetic field (which is constant in space and time) the magnetic helicity of the field within a periodic domain is no longer an invariant of the ideal equations. Alternatively, there is a generalized magnetic helicity that is an invariant of the ideal equations. It is shown that this quantity is not gauge invariant and that it can therefore not be used in practice. Instead, the evolution equation of the magnetic helicity of the field describing the deviation from the imposed field is shown to be a useful tool. It is demonstrated that this tool can determine steady state quenching of the alpha-effect. A simple three-scale model is derived to describe the evolution of the magnetic helicity and to predict its sign as a function of the imposed field strength. The results of the model agree favorably with simulations.
Plasma-satellite interaction driven magnetic field perturbations
Saeed-ur-Rehman, E-mail: email@example.com [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada); Theoretical Physics Division, PINSTECH, Nilore Islamabad 44000 (Pakistan); Marchand, Richard, E-mail: firstname.lastname@example.com [Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada)
We report the first fully kinetic quantitative estimate of magnetic field perturbations caused by the interaction of a spacecraft with space environment. Such perturbations could affect measurements of geophysical magnetic fields made with very sensitive magnetometers on-board satellites. Our approach is illustrated with a calculation of perturbed magnetic fields near the recently launched Swarm satellites. In this case, magnetic field perturbations do not exceed 20 pT, and they are below the sensitivity threshold of the on-board magnetometers. Anticipating future missions in which satellites and instruments would be subject to more intense solar UV radiation, however, it appears that magnetic field perturbations associated with satellite interaction with space environment, might approach or exceed instruments' sensitivity thresholds.
Plasma expansion in the presence of a dipole magnetic field
Winske, D.; Omidi, N. [Applied Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); SciberNet, Inc., Solana Beach, California 92075 (United States)
Simulations of the initial expansion of a plasma injected into a stationary magnetized background plasma in the presence of a dipole magnetic field are carried out in two dimensions with a kinetic ion, massless fluid electron (hybrid) electromagnetic code. For small values of the magnetic dipole, the injected ions have large gyroradii compared to the scale length of the dipole field and are essentially unmagnetized. As a result, these ions expand, excluding the ambient magnetic field and plasma to form a diamagnetic cavity. However, for stronger magnetic dipoles, the ratio of the gyroradii of the injected ions to the dipole field scale length is small so that they remain magnetized, and hence trapped in the dipole field, as they expand. The trapping and expansion then lead to additional plasma currents and resulting magnetic fields that not only exclude the background field but also interact with the dipole field in a more complex manner that stretches the closed dipole field lines. A criterion to distinguish between the two regimes is derived and is then briefly discussed in the context of applying the results to the plasma sail scheme for the propulsion of small spacecraft in the solar wind.
Faraday rotation: effect of magnetic field reversals
Melrose, D B
The standard formula for the rotation measure, RM, which determines the position angle, $\\psi={\\rm RM}\\lambda^2$, due to Faraday rotation, includes contributions only from the portions of the ray path where the natural modes of the plasma are circularly polarized. In small regions of the ray path where the projection of the magnetic field on the ray path reverses sign (called QT regions) the modes are nearly linearly polarized. The neglect of QT regions in estimating RM is not well justified at frequencies below a transition frequency where mode coupling changes from strong to weak. By integrating the polarization transfer equation across a QT region in the latter limit, I estimate the additional contribution $\\Delta\\psi$ needed to correct this omission. In contrast with a result proposed by \\cite{BB10}, $\\Delta\\psi$ is small and probably unobservable. I identify a new source of circular polarization, due to mode coupling in an asymmetric QT region. I also identify a new circular-polarization-dependent correc...
Melrose, D. B. [SIfA, School of Physics, University of Sydney, NSW 2006 (Australia)
The standard formula for the rotation measure (RM), which determines the position angle, {psi} = RM{lambda}{sup 2}, due to Faraday rotation, includes contributions only from the portions of the ray path where the natural modes of the plasma are circularly polarized. In small regions of the ray path where the projection of the magnetic field on the ray path reverses sign (called QT regions) the modes are nearly linearly polarized. The neglect of QT regions in estimating RM is not well justified at frequencies below a transition frequency where mode coupling changes from strong to weak. By integrating the polarization transfer equation across a QT region in the latter limit, I estimate the additional contribution {Delta}{psi} needed to correct this omission. In contrast with a result proposed by Broderick and Blandford, {Delta}{psi} is small and probably unobservable. I identify a new source of circular polarization, due to mode coupling in an asymmetric QT region. I also identify a new circular-polarization-dependent correction to the dispersion measure at low frequencies.
Cosmic Acceleration and Anisotropic models with Magnetic field
S. K. Tripathy; K. L. Mahanta
Plane symmetric cosmological models are investigated with or without any dark energy components in the field equations. Keeping an eye on the recent observational constraints concerning the accelerating phase of expansion of the universe, the role of magnetic field is assessed. In the absence of dark energy components, magnetic field can favour an accelerating model even if we take a linear relationship between the directional Hubble parameters. In presence of dark energy components in the form of a time varying cosmological constant, the influence of magnetic field is found to be limited.
Magnetic-field sensing coil embedded in ceramic for measuring ambient magnetic field
Takahashi, Hironori
A magnetic pick-up coil for measuring magnetic field with high specific sensitivity, optionally with an electrostatic shield (24), having coupling elements (22) with high winding packing ratio, oriented in multiple directions, and embedded in ceramic material for structural support and electrical insulation. Elements of the coil are constructed from green ceramic sheets (200) and metallic ink deposited on surfaces and in via holes of the ceramic sheets. The ceramic sheets and the metallic ink are co-fired to create a monolithic hard ceramic body (20) with metallized traces embedded in, and placed on exterior surfaces of, the hard ceramic body. The compact and rugged coil can be used in a variety of environments, including hostile conditions involving ultra-high vacuum, high temperatures, nuclear and optical radiation, chemical reactions, and physically demanding surroundings, occurring either individually or in combinations.
Magnetic fields, spots and weather in chemically peculiar stars
O. Kochukhov
New observational techniques and sophisticated modelling methods has led to dramatic breakthroughs in our understanding of the interplay between the surface magnetism, atomic diffusion and atmospheric dynamics in chemically peculiar stars. Magnetic Doppler images, constructed using spectropolarimetric observations of Ap stars in all four Stokes parameters, reveal the presence of small-scale field topologies. Abundance Doppler mapping has been perfected to the level where distributions of many different chemical elements can be deduced self-consistently for one star. The inferred chemical spot structures are diverse and do not always trace underlying magnetic field geometry. Moreover, horizontal chemical inhomogeneities are discovered in non-magnetic CP stars and evolving chemical spots are observed for the first time in the bright mercury-manganese star alpha And. These results show that in addition to magnetic fields, another important non-magnetic structure formation mechanism acts in CP stars.
Observation of Dirac Monopoles in a Synthetic Magnetic Field
Ray, M W; Kandel, S; M�tt�nen, M; Hall, D S
Magnetic monopoles --- particles that behave as isolated north or south magnetic poles --- have been the subject of speculation since the first detailed observations of magnetism several hundred years ago. Numerous theoretical investigations and hitherto unsuccessful experimental searches have followed Dirac's 1931 development of a theory of monopoles consistent with both quantum mechanics and the gauge invariance of the electromagnetic field. The existence of even a single Dirac magnetic monopole would have far-reaching physical consequences, most famously explaining the quantization of electric charge. Although analogues of magnetic monopoles have been found in exotic spin-ices and other systems, there has been no direct experimental observation of Dirac monopoles within a medium described by a quantum field, such as superfluid helium-3. Here we demonstrate the controlled creation of Dirac monopoles in the synthetic magnetic field produced by a spinor Bose-Einstein condensate. Monopoles are identified, in b...
Consistent generation of magnetic fields in axion inflation models
Fujita, Tomohiro; Tada, Yuichiro; Takeda, Naoyuki; Tashiro, Hiroyuki
There has been a growing evidence for the existence of magnetic fields in the extra-galactic regions, while the attempt to associate their origin with the inflationary epoch alone has been found extremely challenging. We therefore take into account the consistent post-inflationary evolution of the magnetic fields that are originated from vacuum fluctuations during inflation. In the model of our interest, the electromagnetic (EM) field is coupled to a pseudo-scalar inflaton $\\phi$ through the characteristic term $\\phi F\\tilde F$, breaking the conformal invariance. This interaction dynamically breaks the parity and enables a continuous production of only one of the polarization states of the EM field through tachyonic instability. The produced magnetic fields are thus helical. We find that the dominant contribution to the observed magnetic fields in this model comes from the modes that leave the horizon near the end of inflation, further enhanced by the tachyonic instability right after the end of inflation. Th...
Magnetic field in holographic superconductor with dark matter sector
Nakonieczny, L; Wysokinski, K I
Based on the analytical technique the effect of the static magnetic field on the s-wave holographic superconductor with dark matter sector of U(1)-gauge field type coupled to the Maxwell field has been examined. In the probe limit, we obtained the mean value of the condensation operator. The nature of the condensate in an external magnetic field as well as the behaviour of the critical field close to the transition temperature has been revealed. The obtained upturn of the critical field curves as a function of temperature, both in four and five spacetime dimensions, is a fingerprint of the strong coupling approach.
On Possible Light-Torsion Mixing in Background Magnetic Field
S. I. Kruglov
The interaction of the light with propagating axial torsion fields in the presence of an external magnetic field has been investigated. Axial torsion fields appearing in higher derivative quantum gravity possess two states, with spin one and zero, with different masses. The torsion field with spin-0 state is a ghost that can be removed if its mass is infinite. We investigate the possibility when the light mixes with the torsion fields resulting in the effect of vacuum birefringence and dichroism. The expressions for ellipticity and the rotation of light polarization axis depending on the coupling constant and the external magnetic field have been obtained.
Bose Glass of Quasiparticles in Doped Quantum Magnet Gregory S. Boebinger, National High Magnetic Field Laboratory
Weston, Ken
Bose Glass of Quasiparticles in Doped Quantum Magnet Gregory S. Boebinger, National High Magnetic. This BEC can localize in the presence of disorder caused by Br- doping to form a Bose Glass. The BEC-Bose Glass (BEC-BG) transition can be carefully controlled by magnetic field, allowing us to sensitively
Magnetic anisotropy in Fe-25Cr-12Co-1Si alloy induced by external magnetic field
Qin, Lu-Chang
Magnetic anisotropy in Fe-25Cr-12Co-1Si alloy induced by external magnetic field ZHEN Liang( )1 of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China; 2. Department 27599-3255, USA Received 29 June 2006; accepted 15 January 2007 Abstract: Structural and magnetic
Color superconductivity in a strong external magnetic field
Cristina Manuel
We explore the effects of an applied strong external magnetic field in a three flavor massless color superconductor. The long-range component of the B field that penetrates the superconductor enhances some quark condensates, leading to a different condensation pattern. The external field also reduces the flavor symmetries in the system, and thus it changes drastically the corresponding low energy physics. Our considerations are relevant for the study of highly magnetized compact stars.
Relation between photospheric flow fields and the magnetic field distribution on the solar surface
Simon, G.W.; Title, A.M.; Topka, K.P.; Tarbell, T.D.; Shine, R.A.
Using the technique of local correlation tracking on a 28 minute time sequence of white-light images of solar granulation, the horizontal flow field on the solar surface is measured. The time series was obtained by the Solar Optical Universal Polarimeter (SOUP) on Spacelab 2 (Space Shuttle flight 51-F) and is free from atmospheric blurring and distortion. The SOUP flow fields have been compared with carefully aligned magnetograms taken over a nine hour period at the Big Bear Solar Observatory before, during, and after the SOUP images. The flow field and the magnetic field agree in considerable detail: vectors which define the flow of the white-light intensity pattern (granulation) point toward magnetic field regions, magnetic fields surround flow cells, and magnetic features move along the flow arrows. The projected locations of free particles (corks) in the measured flow field congregate at the same locations where the magnetic field is observed. 31 references.
Constraining primordial magnetic fields with future cosmic shear surveys
Fedeli, C. [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611 (United States); Moscardini, L., E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com [Dipartimento di Astronomia, Universit� di Bologna, Via Ranzani 1, 40127 Bologna (Italy)
The origin of astrophysical magnetic fields observed in galaxies and clusters of galaxies is still unclear. One possibility is that primordial magnetic fields generated in the early Universe provide seeds that grow through compression and turbulence during structure formation. A cosmological magnetic field present prior to recombination would produce substantial matter clustering at intermediate/small scales, on top of the standard inflationary power spectrum. In this work we study the effect of this alteration on one particular cosmological observable, cosmic shear. We adopt the semi-analytic halo model in order to describe the non-linear clustering of matter, and feed it with the altered mass variance induced by primordial magnetic fields. We find that the convergence power spectrum is, as expected, substantially enhanced at intermediate/small angular scales, with the exact amplitude of the enhancement depending on the magnitude and power-law index of the magnetic field power spectrum. Specifically, for a fixed amplitude, the effect of magnetic fields is larger for larger spectral indices. We use the predicted statistical errors for a future wide-field cosmic shear survey, on the model of the ESA Cosmic Vision mission Euclid, in order to forecast constraints on the amplitude of primordial magnetic fields as a function of the spectral index. We find that the amplitude will be constrained at the level of ? 0.1 nG for n{sub B} ? ?3, and at the level of ? 10{sup ?7} nG for n{sub B} ? 3. The latter is at the same level of lower bounds coming from the secondary emission of gamma-ray sources, implying that for high spectral indices Euclid will certainly be able to detect primordial magnetic fields, if they exist. The present study shows how large-scale structure surveys can be used for both understanding the origins of astrophysical magnetic fields and shedding new light on the physics of the pre-recombination Universe.
Magnetic Fields above the Surface of aSuperconductor with Internal Magnetism
Bluhm, Hendrik; /Stanford U., Phys. Dept. /SLAC, SSRl
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.
Weston, Ken
, and Geochemistry 14 MAGNET SCIENCE & TECHNOLOGY Engineering Materials, Instrumentation, and Magnet Technology Magnet Science & Technology 42 7 including Engineering Materials, Instrumentation, and Magnet TechnologyNATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSVOLUME 12 � N0. 1 � 2005 OPERATED BY: FLORIDA STATE
Magnetic Helicity and the Relaxation of Fossil Fields
Avery E. Broderick; Ramesh Narayan
In the absence of an active dynamo, purely poloidal magnetic field configurations are unstable to large-scale dynamical perturbations, and decay via reconnection on an Alfvenic timescale. Nevertheless, a number of classes of dynamo-free stars do exhibit significant, long-lived, surface magnetic fields. Numerical simulations suggest that the large-scale poloidal field in these systems is stabilized by a toroidal component of the field in the stellar interior. Using the principle of conservation of total helicity, we develop a variational principle for computing the structure of the magnetic field inside a conducting sphere surrounded by an insulating vacuum. We show that, for a fixed total helicity, the minimum energy state corresponds to a force-free configuration. We find a simple class of axisymmetric solutions, parametrized by angular and radial quantum numbers. However, these solutions have a discontinuity in the toroidal magnetic field at the stellar surface which will exert a toroidal stress on the surface of the star. We then describe two other classes of solutions, the standard spheromak solutions and ones with fixed surface magnetic fields, the latter being relevant for neutron stars with rigid crusts. We discuss the implications of our results for the structure of neutron star magnetic fields, the decay of fields, and the origin of variability and outbursts in magnetars.
Transient horizontal magnetic fields in solar plage regions
R. Ishikawa; S. Tsuneta; K. Ichimoto; H. Isobe; Y. Katsukawa; B. W. Lites; S. Nagata; T. Shimizu; R. A. Shine; Y. Suematsu; T. D. Tarbell; A. M. Title
We report the discovery of isolated, small-scale emerging magnetic fields in a plage region with the Solar Optical Telescope aboard Hinode. Spectro-polarimetric observations were carried out with a cadence of 34 seconds for the plage region located near disc center. The vector magnetic fields are inferred by Milne-Eddington inversion. The observations reveal widespread occurrence of transient, spatially isolated horizontal magnetic fields. The lateral extent of the horizontal magnetic fields is comparable to the size of photospheric granules. These horizontal magnetic fields seem to be tossed about by upflows and downflows of the granular convection. We also report an event that appears to be driven by the magnetic buoyancy instability. We refer to buoyancy-driven emergence as type1 and convection-driven emergence as type2. Although both events have magnetic field strengths of about 600 G, the filling factor of type1 is a factor of two larger than that of type2. Our finding suggests that the granular convection in the plage regions is characterized by a high rate of occurrence of granular-sized transient horizontal fields.
Modeling spin magnetization transport in a spatially varying magnetic field
Rico A. R. Picone; Joseph L. Garbini; John A. Sidles
We present a framework for modeling the transport of any number of globally conserved quantities in any spatial configuration and apply it to obtain a model of magnetization transport for spin-systems that is valid in new regimes (including high-polarization). The framework allows an entropy function to define a model that explicitly respects the laws of thermodynamics. Three facets of the model are explored. First, it is expressed as nonlinear partial differential equations that are valid for the new regime of high dipole-energy and polarization. Second, the nonlinear model is explored in the limit of low dipole-energy (semi-linear), from which is derived a physical parameter characterizing separative magnetization transport (SMT). It is shown that the necessary and sufficient condition for SMT to occur is that the parameter is spatially inhomogeneous. Third, the high spin-temperature (linear) limit is shown to be equivalent to the model of nuclear spin transport of Genack and Redfield. Differences among the three forms of the model are illustrated by numerical solution with parameters corresponding to a magnetic resonance force microscopy (MRFM) experiment. A family of analytic, steady-state solutions to the nonlinear equation is derived and shown to be the spin-temperature analog of the Langevin paramagnetic equation and Curie's law. Finally, we analyze the separative quality of magnetization transport, and a steady-state solution for the magnetization is shown to be compatible with Fenske's separative mass transport equation.
Magnetic Field Geometry in "Red" and "Blue" BL Lacs
P. Kharb; D. C. Gabuzda; P. Shastri
We compare the systematics of the magnetic field geometry in the "red" low-energy peaked BL Lacs (LBLs) and "blue" high-energy peaked BL Lacs (HBLs) using VLBI polarimetric images. The LBLs are primarily "radio--selected" BL Lacs and the HBLs are primarily "X-ray selected". In contrast to the LBLs, which show predominantly transverse jet magnetic fields, the HBLs show predominantly longitudinal fields. Thus, while the SED peaks of core-dominated quasars, LBLs and HBLs form a sequence of increasing frequency, the magnetic field geometry does not follow an analogous sequence. We briefly investigate possible connections between the observed parsec-scale magnetic field structures and circular polarization measurements in the literature on various spatial scales.
Electromagnetic Waves Reflectance of Graphene -- Magnetic Semiconductor Superlattice in Magnetic Field
Kuzmin, Dmitry A; Shavrov, Vladimir G
Electrodynamic properties of the graphene - magnetic semiconductor - graphene superlattice placed in magnetic field have been investigated theoretically in Faraday geometry with taking into account dissipation processes. Frequency and field dependences of the reflectance, transmittance and absorbtance of electromagnetic waves by such superlattice have been calculated for different numbers of periods of the structure and different sizes of the periods with using a transfer matrix method. The possibility of efficient control of electrodynamic properties of graphene - magnetic semiconductor - graphene superlattice has been shown.
Effects of non-radial magnetic field on measuring magnetic helicity transport across solar photosphere
Song, Yongliang
It is generally believed that the evolution of magnetic helicity has a close relationship with solar activity. Before the launch of SDO, earlier studies have mostly used MDI/SOHO line of sight magnetograms and assumed that magnetic fields are radial when calculating magnetic helicity injection rate from photospheric magnetograms. However, this assumption is not necessarily true. Here we use the vector magnetograms and line of sight magnetograms, both taken by HMI/SDO, to estimate the effects of non-radial magnetic field on measuring magnetic helicity injection rate. We find that: 1) The effect of non-radial magnetic field on estimating tangential velocity is relatively small; 2) On estimating magnetic helicity injection rate, the effect of non-radial magnetic field is strong when active regions are observed near the limb and is relatively small when active regions are close to disk center; 3) The effect of non-radial magnetic field becomes minor if the amount of accumulated magnetic helicity is the only conce...
Heat pipes for use in a magnetic field
Werner, R.W.; Hoffman, M.A.
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.
Universality of critical magnetic field in holographic superconductor
D. Momeni; R. Myrzakulov
In this letter we study aspects of the holographic superconductors analytically in the presence of a constant external magnetic field. We show that the critical temperature and critical magnetic field can be calculated at nonzero temperature. We detect the Meissner effect in such superconductors. A universal relation between black hole mass $ M$ and critical magnetic field $H_c$ is proposed as $\\frac{H_c}{M^{2/3}}\\leq 0.687365$. We discuss some aspects of phase transition in terms of black hole entropy and the Bekenstein's entropy to energy upper bound.
The Stability of Magnetized Rotating Plasmas with Superthermal Fields
Martin E. Pessah; Dimitrios Psaltis
During the last decade it has become evident that the magnetorotational instability is at the heart of the enhanced angular momentum transport in weakly magnetized accretion disks around neutron stars and black holes. In this paper, we investigate the local linear stability of differentially rotating, magnetized flows and the evolution of the magnetorotational instability beyond the weak-field limit. We show that, when superthermal toroidal fields are considered, the effects of both compressibility and magnetic tension forces, which are related to the curvature of toroidal field lines, should be taken fully into account. We demonstrate that the presence of a strong toroidal component in the magnetic field plays a non-trivial role. When strong fields are considered, the strength of the toroidal magnetic field not only modifies the growth rates of the unstable modes but also determines which modes are subject to instabilities. We find that, for rotating configurations with Keplerian laws, the magnetorotational instability is stabilized at low wavenumbers for toroidal Alfven speeds exceeding the geometric mean of the sound speed and the rotational speed. We discuss the significance of our findings for the stability of cold, magnetically dominated, rotating fluids and argue that, for these systems, the curvature of toroidal field lines cannot be neglected even when short wavelength perturbations are considered. We also comment on the implications of our results for the validity of shearing box simulations in which superthermal toroidal fields are generated.
A new magnetic field integral measurement system
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
measurements. b. Second field integral (horizontal and vertical) measurements. c. Multipole components of first field integral measurements. 2. Translation Coil a. Multipole...
Impact of Dynamic Magnetic fields on the CLIC Main Beam
Snuverink, J; Jach, C; Jeanneret, JB; Schulte, D; Stulle, F
The Compact Linear Collider (CLIC) accelerator has strong precision requirements on the position of the beam. The beam position will be sensitive to external dynamic magnetic fields (stray fields) in the nanotesla regime. The impact of these fields on the CLIC main beam has been studied by performing simulations on the lattices and tolerances have been determined. Several mitigation techniques will be discussed.
Magnetic Field Confinement in the Corona: The Role of Magnetic Helicity Accumulation
Mei Zhang; Natasha Flyer; Boon Chye Low
A loss of magnetic field confinement is believed to be the cause of coronal mass ejections (CMEs), a major form of solar activity in the corona. The mechanisms for magnetic energy storage are crucial in understanding how a field may possess enough free energy to overcome the Aly limit and open up. Previously, we have pointed out that the accumulation of magnetic helicity in the corona plays a significant role in storing magnetic energy. In this paper, we investigate another hydromagnetic consequence of magnetic-helicity accumulation. We propose a conjecture that there is an upper bound on the total magnetic helicity that a force-free field can contain. This is directly related to the hydromagnetic property that force-free fields in unbounded space have to be self-confining. Although a mathematical proof of this conjecture for any field configuration is formidable, its plausibility can be demonstrated with the properties of several families of power-law, axisymmetric force-free fields. We put forth mathematical evidence, as well as numerical, indicating that an upper bound on the magnetic helicity may exist for such fields. Thus, the accumulation of magnetic helicity in excess of this upper bound would initiate a non-equilibrium situation, resulting in a CME expulsion as a natural product of coronal evolution.
Influence of primordial magnetic fields on 21 cm emission
Dominik R. G. Schleicher; Robi Banerjee; Ralf S. Klessen
Magnetic fields in the early universe can significantly alter the thermal evolution and the ionization history during the dark ages. This is reflected in the 21 cm line of atomic hydrogen, which is coupled to the gas temperature through collisions at high redshifts, and through the Wouthuysen-Field effect at low redshifts. We present a semi-analytic model for star formation and the build-up of a Lyman alpha background in the presence of magnetic fields, and calculate the evolution of the mean 21 cm brightness temperature and its frequency gradient as a function of redshift. We further discuss the evolution of linear fluctuations in temperature and ionization in the presence of magnetic fields and calculate the effect on the 21 cm power spectrum. At high redshifts, the signal is increased compared to the non-magnetic case due to the additional heat input into the IGM from ambipolar diffusion and the decay of MHD turbulence. At lower redshifts, the formation of luminous objects and the build-up of a Lyman alpha background can be delayed by a redshift interval of 10 due to the strong increase of the filtering mass scale in the presence of magnetic fields. This tends to decrease the 21 cm signal compared to the zero-field case. In summary, we find that 21 cm observations may become a promising tool to constrain primordial magnetic fields.
Dust-Plasma Sheath in an Oblique Magnetic Field
Foroutan, G.; Mehdipour, H. [Physics Department, Faculty of Science, Sahand University of Technology, Tabriz (Iran, Islamic Republic of)
Using numerical simulations of the multi fluid equations the structure of the magnetized sheath near a plasma boundary is studied in the presence of charged dust particles. The dependence of the electron, ion, and dust densities as well as the electrostatic potential, dust charge, and ion normal velocity, on the magnetic field strength and the edge dust number density is investigated.
1 Magnetic Fields and Solar This article describesthe relationshipbetweenmagnetic
reconnection. The free magnetic energy is con- verted to thermal and non- thermal energy to power solar ares, which create thermal emissions and accel- eration of non-thermal particles. The total energy1 Magnetic Fields and Solar Flares This article describesthe relationshipbetweenmagnetic elds
November 18, 2005 Chandra Observations of Magnetic Fields and Relativistic
Schwartz, Daniel
November 18, 2005 Chandra Observations of Magnetic Fields and Relativistic Beaming in Four Quasar microwave background. If particles and magnetic #12;elds are near minimum energy density 1 Harvard CSIRO Australia Telescope National Facility, PO Box 76, Epping NSW 1710, Australia 4 Jet Propulsion
Terahertz radiation detection by field effect transistor in magnetic field S. Boubanga-Tombet,1,a
Levelut, Claire
Terahertz radiation detection by field effect transistor in magnetic field S. Boubanga-Tombet,1,a M; accepted 30 July 2009; published online 19 August 2009 We report on terahertz radiation detection with In
The Stability of Magnetized Rotating Plasmas with Superthermal Fields
Pessah, M E
During the last decade it has become evident that the magnetorotational instability is at the heart of the enhanced angular momentum transport in weakly magnetized accretion disks around neutron stars and black holes. In this paper, we investigate the local linear stability of differentially rotating, magnetized flows and the evolution of the magnetorotational instability beyond the weak-field limit. We show that, when superthermal toroidal fields are considered, both compressibility and magnetic tension terms, related to the curvature of toroidal field lines, should be taken fully into account. We demonstrate that, contrary to the results of most previous investigations, the presence of a toroidal component in the magnetic field plays a crucial role not only in the growth rates of the unstable modes but also in determining which modes are subject to instabilities. We find that, for rotationally supported configurations, the magnetorotational instability is stabilized at low wavenumbers for toroidal Alfven sp...
Magnetic Fields and the Triaxiality of Molecular Cloud Cores
Shantanu Basu
We make the hypothesis that molecular cloud fragments are triaxial bodies with a large scale magnetic field oriented along the short axis. While consistent with theoretical expectations, this idea is supported by magnetic field strength data, which show strong evidence for flattening along the direction of the mean magnetic field. It is also consistent with early submillimeter polarization data, which show that the projected direction of the magnetic field is often slightly misaligned with the projected minor axis of a molecular cloud core, i.e., the offset angle $\\Psi$ is nonzero. We calculate distributions of $\\Psi$ for various triaxial bodies, when viewed from a random set of viewing angles. The highest viewing probability always corresponds to $\\Psi=0^{\\circ}$, but there is a finite probability of viewing all nonzero $\\Psi$, including even $\\Psi =90^{\\circ}$; the average offset typically falls in the range $10^{\\circ}-30^{\\circ}$ for triaxial bodies most likely to satisfy observational and theoretical constraints.
Magnetic Fields in High-Density Stellar Matter
German Lugones
I briefly review some aspects of the effect of magnetic fields in the high density regime relevant to neutron stars, focusing mainly on compact star structure and composition, superconductivity, combustion processes, and gamma ray bursts.
Low-field classroom nuclear magnetic resonance system
Zimmerman, Clarissa Lynette
The goal of this research was to develop a Low-field Classroom NMR system that will enable hands-on learning of NMR and MRI concepts in a Biological-Engineering laboratory course. A permanent magnet system, designed using ...
Ferrofluid surface and volume flows in uniform rotating magnetic fields
Elborai, Shihab M. (Shihab Mahmoud), 1977-
Ferrofluid surface and volume effects in uniform dc and rotating magnetic fields are studied. Theory and corroborating measurements are presented for meniscus shapes and resulting surface driven flows, spin-up flows, and ...
A Holographic Superconductor in an External Magnetic Field
Tameem Albash; Clifford V. Johnson
We study a system of a complex charged scalar coupled to a Reissner-Nordstrom black hole in 3+1 dimensional anti-de Sitter spacetime, neglecting back-reaction. With suitable boundary conditions, the cases of a neutral and purely electric black hole have been studied in various limits and were shown to yield key elements of superconductivity in the dual 2+1 dimensional field theory, forming a condensate below a critical temperature. By adding magnetic charge to the black hole, we immerse the superconductor into an external magnetic field. We show that a family of condensates can form and we examine their structure. For finite magnetic field, they are localized in one dimension with a profile that is exactly solvable, since it maps to the quantum harmonic oscillator. As the magnetic field increases, the condensate shrinks in size, which is reminiscent of the Meissner effect.
Primordial magnetic fields and formation of molecular hydrogen
Shiv K Sethi; Biman B. Nath; Kandaswamy Subramanian
We study the implications of primordial magnetic fields for the thermal and ionization history of the post-recombination era. In particular we compute the effects of dissipation of primordial magnetic fields owing to ambipolar diffusion and decaying turbulence in the intergalactic medium (IGM) and the collapsing halos and compute the effects of the altered thermal and ionization history on the formation of molecular hydrogen. We show that, for magnetic field strengths in the range $2 \\times 10^{-10} {\\rm G} \\la B_0 \\la 2 \\times 10^{-9} {\\rm G}$, the molecular hydrogen fraction in IGM and collapsing halo can increase by a factor 5 to 1000 over the case with no magnetic fields. We discuss the implication of the increased molecular hydrogen fraction on the radiative transfer of UV photons and the formation of first structures in the universe.
Error field and magnetic diagnostic modeling for W7-X
Lazerson, Sam A. [PPPL; Gates, David A. [PPPL; NEILSON, GEORGE H. [PPPL; OTTE, M.; Bozhenkov, S.; Pedersen, T. S.; GEIGER, J.; LORE, J.
The prediction, detection, and compensation of error fields for the W7-X device will play a key role in achieving a high beta (? = 5%), steady state (30 minute pulse) operating regime utilizing the island divertor system [1]. Additionally, detection and control of the equilibrium magnetic structure in the scrape-off layer will be necessary in the long-pulse campaign as bootstrapcurrent evolution may result in poor edge magnetic structure [2]. An SVD analysis of the magnetic diagnostics set indicates an ability to measure the toroidal current and stored energy, while profile variations go undetected in the magnetic diagnostics. An additional set of magnetic diagnostics is proposed which improves the ability to constrain the equilibrium current and pressure profiles. However, even with the ability to accurately measure equilibrium parameters, the presence of error fields can modify both the plasma response and diverter magnetic field structures in unfavorable ways. Vacuum flux surface mapping experiments allow for direct measurement of these modifications to magnetic structure. The ability to conduct such an experiment is a unique feature of stellarators. The trim coils may then be used to forward model the effect of an applied n = 1 error field. This allows the determination of lower limits for the detection of error field amplitude and phase using flux surface mapping. *Research supported by the U.S. DOE under Contract No. DE-AC02-09CH11466 with Princeton University.
Warm inflation in the presence of magnetic fields
Gabriella Piccinelli; Angel Sanchez; Alejandro Ayala; Ana Julia Mizher
We study the effects of primordial magnetic fields on the inflationary potential in the context of a warm inflation scenario. The model, based on global supersymmetry with a new-inflation-type potential and a coupling between the inflaton and a heavy intermediate superfield, is already known to preserve the flatness required for slow-roll conditions even after including thermal contributions. Here we show that the magnetic field makes the potential even flatter, retarding the transition and rendering it smoother.
GUT Cosmic Magnetic Fields in a Warm Inflationary Universe
Arjun Berera; Thomas W. Kephart; Stuart D. Wick
Sources of magnetic fields from grand unified theories are studied in the warm inflation regime. A ferromagnetic Savvidy vacuum scenario is presented that yields observationally interesting large scale magnetic fields. As an intermediate step, a general analysis is made of defect production at the onset of warm inflation and monopole constraints are obtained. Many features of this Savvidy vacuum scenario are applicable within a supercooled inflation regime and these points are discussed.
One-way Ponderomotive Barrier in a Uniform Magnetic Field
I.Y. Dodin; N.J. Fisch
The possibility of an asymmetric ponderomotive barrier in a nonuniform dc magnetic field by high-frequency radiation near the cyclotron resonance for selected plasma species was contemplated in Physics of Plasmas 11 (November 2004) 5046-5064. Here we show that a similar one-way barrier, which reflects particles incident from one side while transmitting those incident from the opposite side, can be produced also in a uniform magnetic field, entirely due to inhomogeneity of high-frequency drive.
Propellantless propulsion in magnetic fields by partially shielded current
Bergamin, L; Pinchook, A
A new device for propellantless propulsion in presence of a magnetic field is discussed. The functional principle shares some features with electrodynamic tethers. However, the tether structure is replaced by a closed wire, which is partially shielded from the magnetic field by means of a superconductor. Therefore, it does not depend on the presence of a plasma. We show that even a relatively small device can yield interesting propulsivet forces for drag compensation or for orbital transfers.
Phase-field simulation of electric-field-induced in-plane magnetic domain switching in magnetic/ferroelectric layered heterostructures
Chen, Long-Qing
). An alternative approach to engineering low electric- field-induced magnetic domain switching at room temperaPhase-field simulation of electric-field-induced in-plane magnetic domain switching in magnetic. Phys. Lett. 99, 182510 (2011) Quantum tunneling of the Bloch point in a magnetic film with strong
Prospects for x-ray polarimetry measurements of magnetic fields in magnetized liner inertial fusion plasmas
Lynn, Alan G., E-mail: email@example.com; Gilmore, Mark [Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131 (United States)
Magnetized Liner Inertial Fusion (MagLIF) experiments, where a metal liner is imploded to compress a magnetized seed plasma may generate peak magnetic fields ?10{sup 4} T (100 Megagauss) over small volumes (?10{sup ?10}m{sup 3}) at high plasma densities (?10{sup 28}m{sup ?3}) on 100 ns time scales. Such conditions are extremely challenging to diagnose. We discuss the possibility of, and issues involved in, using polarimetry techniques at x-ray wavelengths to measure magnetic fields under these extreme conditions.
Collisionless Shocks -- Magnetic Field Generation and Particle Acceleration
J. Trier Frederiksen; C. B. Hededal; T. Haugboelle; A. Nordlund
We present numerical results from plasma particle simulations of collisionless shocks and ultra-relativistic counter-streaming plasmas. We demonstrate how the field-particle interactions lead to particle acceleration behind the shock-front. Further, we demonstrate how ultra relativistic counter-streaming plasmas create large scale patchy magnetic field structures and that these field structures propagate down-stream of the shock front. These results may help explain the origin of the magnetic fields and accelerated electrons responsible for afterglow synchrotron radiation from gamma ray bursts.
Confining potential from interacting magnetic and torsion fields
Patricio Gaete; Jos� A. Hela�el-Neto
Adopting the gauge-invariant but path-dependent variables formalism, we study the coupling of torsion fields with photons in the presence of an external background electromagnetic. We explicitly show that, in the case of a constant electric field strength expectation value, the static potential remains Coulombic, while in the case of a constant magnetic field strength expectation value a confining potential is obtained. This result displays a marked qualitative departure from the usual coupling of axionlike particles with photons in the presence of an external magnetic field.
Magnetic Fields via Polarimetry: Progress of Grain Alignment Theory
A. Lazarian
Most astrophysical systems, e.g. stellar winds, the diffuse interstellar medium, molecular clouds, are magnetized with magnetic fields that influence almost all of their properties. One of the most informative techniques of magnetic field studies is based on the use of starlight polarization and polarized emission arising from aligned dust. How reliable the interpretation of the polarization maps in terms of magnetic fields is the issue that the grain alignment theory addresses. Although grain alignment is a problem of half a century standing, recent progress achieved in the field makes us believe that we are approaching the solution of this mystery. I review basic physical processes involved in grain alignment and discuss the niches for different alignment mechanisms. I show why mechanisms that were favored for decades do not look so promising right now, while the radiative torque mechanism ignored for more than 20 years looks so attractive. I define the observational tests and outline the circumstances when grain alignment theory predicts that new yet untapped information of magnetic field structure is available through polarimetry. In particular, I touch upon mapping magnetic fields in circumstellar regions, interplanetary space and in comet comae.
The influence of the magnetic field on the performance of an active magnetic regenerator (AMR)
Bj�rk, R
The influence of the time variation of the magnetic field, termed the magnetic field profile, on the performance of a magnetocaloric refrigeration device using the active magnetic regeneration (AMR) cycle is studied for a number of process parameters for both a parallel plate and packed bed regenerator using a numerical model. The cooling curve of the AMR is shown to be almost linear far from the Curie temperature of the magnetocaloric material. It is shown that a magnetic field profile that is 10% of the cycle time out of sync with the flow profile leads to a drop in both the maximum temperature span and the maximum cooling capacity of 20-40\\% for both parallel plate and packed bed regenerators. The maximum cooling capacity is shown to depend very weakly on the ramp rate of the magnetic field. Reducing the temporal width of the high field portion of the magnetic field profile by 10% leads to a drop in maximum temperature span and maximum cooling capacity of 5-20%. An increase of the magnetic field from 1 T t...
Influence of Time-Varying External Magnetic Fields on Trapped Fields in Bulk Superconductors
Zou, Jin; Ainslie, Mark D.; Hu, Di; Cardwell, David A.
Large, single-grain bulk high-temperature superconductors (HTS) can trap magnetic fields over 17 T below 30 K and up to 3 T at 77 K, and have significant potential to replace permanent magnets, the fields from which are limited to significantly less...
Study of HTS Wires at High Magnetic Fields
Turrioni, D.; Barzi, E.; Lamm, M.J.; Yamada, R.; Zlobin, A.V.; Kikuchi, A.; /Fermilab
Fermilab is working on the development of high field magnet systems for ionization cooling of muon beams. The use of high temperature superconducting (HTS) materials is being considered for these magnets using Helium refrigeration. Critical current (I{sub c}) measurements of HTS conductors were performed at FNAL and at NIMS up to 28 T under magnetic fields at zero to 90 degree with respect to the sample face. A description of the test setups and results on a BSCCO-2223 tape and second generation (2G) coated conductors are presented.
Fluorescent lamp unit with magnetic field generating means
Grossman, M.W.; George, W.A.
A fluorescent lamp unit having a magnetic field generating means for improving the performance of the fluorescent lamp is disclosed. In a preferred embodiment the fluorescent lamp comprises four longitudinally extending leg portions disposed in substantially quadrangular columnar array and joined by three generally U-shaped portions disposed in different planes. In another embodiment of the invention the magnetic field generating means comprises a plurality of permanent magnets secured together to form a single columnar structure disposed within a centrally located region defined by the shape of lamp envelope. 4 figs.
Tuning magnetic disorder in diluted magnetic semiconductors using high fields to 89 Tesla
Crooker, Scott A [Los Alamos National Laboratory; Samarth, Nitin [PENN STATE U
We describe recent and ongoing studies at the National High Magnetic Field Laboratory at Los Alamos using the new '100 Tesla Multi-Shot Magnet', which is presently delivering fields up to {approx}89 T during its commissioning. We discuss the first experiments performed in this magnet system, wherein the linewidth of low-temperature photoluminescence spectra was used to directly reveal the degree of magnetic alloy disorder 'seen' by excitons in single Zn{sub 0.80}Cd{sub 0.22}Mn{sub 0.08}Se quantum wells. The magnetic potential landscape in II-VI diluted magnetic semiconductors (DMS) is typically smoothed when the embedded Mn{sup 2+} spins align in an applied field. However, an important (but heretofore untested) prediction of current models of compositional disorder is that magnetic alloy fluctuations in many DMS compounds should increase again in very large magnetic fields approaching 100 T. We observed precisely this increase above {approx}70 T, in agreement with a simple model of magnetic alloy disorder.
Patterning of hydrogenated microcrystalline silicon growth by magnetic field
Fejfar, A.; Stuchlik, J.; Mates, T.; Ledinsky, M.; Honda, S.; Kocka, J. [Institute of Physics, Academy of Sciences of the Czech Republic, Cukrovarnicka 10, 162 53 Prague 6 (Czech Republic)
A way of influencing growth of silicon films by magnetic field is demonstrated. Permanent magnet(s) placed under the substrate influenced the discharge in a mixture of silane and hydrogen and led to formation of microcrystalline regions in otherwise amorphous film. The pattern of microcrystalline regions varied with the orientation of the magnetic field. Microscopic study by atomic force microscopy and by micro-Raman spectroscopy revealed that the microcrystalline regions resulted from a higher density of crystalline grain nuclei, increased at the locations where the magnetron effect could be expected. This phenomenon could be used to study the transition between amorphous and microcrystalline growth. Moreover, we suggest it as a kind of 'magnetic lithography' for the preparation of predefined microcrystalline patterns in otherwise amorphous silicon films.
Mechanical design of a high field common coil magnet
Caspi, S.; Chow, K.; Dietderich, D.; Gourlay, S.; Gupta, R.; McInturff, A.; Millos, G.; Scanlan, R.
A common coil design for high field 2-in-1 accelerator magnets has been previously presented as a 'conductor-friendly' option for high field magnets applicable for a Very Large Hadron Collider. This paper presents the mechanical design for a 14 tesla 2-in-1 dipole based on the common coil design approach. The magnet will use a high current density Nb{sub 3}Sn conductor. The design addresses mechanical issues particular to the common coil geometry: horizontal support against coil edges, vertical preload on coil faces, end loading and support, and coil stresses and strains. The magnet is the second in a series of racetrack coil magnets that will provide experimental verification of the common coil design approach.
Localized Axion Photon States in a Strong Magnetic Field
E. I. Guendelman
We consider the axion field and electromagnetic waves with rapid time dependence, coupled to a strong time independent, asymptotically approaching a constant at infinity "mean" magnetic field, which takes into account the back reaction from the axion field and electromagnetic waves with rapid time dependence in a time averaged way. The direction of the self consistent mean field is orthogonal to the common direction of propagation of the axion and electromagnetic waves with rapid time dependence and parallel to the polarization of these electromagnetic waves. Then, there is an effective U(1) symmetry mixing axions and photons. Using the natural complex variables that this U(1) symmetry suggests we find localized planar soliton solutions. These solutions appear to be stable since they produce a different magnetic flux than the state with only a constant magnetic field, which we take as our "ground state". The solitons also have non trivial U(1) charge defined before, different from the uncharged vacuum.
Extragalactic Magnetic Field and the Highest Energy Cosmic Rays
Sangjin Lee; Angela Olinto; Guenter Sigl
The strength and spectrum of the extragalactic magnetic field are still unknown. Its measurement would help answer the question of whether galactic fields are purely a primordial relic or were dynamically enhanced from a much smaller cosmological seed field. In this letter, we show that the composition, spectrum, and directional distribution of extragalactic ultrahigh energy cosmic rays with energies above $\\simeq 10^{18}\\ev$ can probe the large scale component of the extragalactic magnetic field below the present observational upper limit of $10^{-9}$ Gauss. Cosmic ray detectors under construction or currently in the proposal stage should be able to test the existence of the extragalactic magnetic fields on scales of a few to tens of Mpc and strengths in the range $\\simeq 10^{-10} - 10^{-9}$ Gauss.
Nematic order of model goethite nanorods in a magnetic field
H. H. Wensink; G. J. Vroege
We explore the nematic order of model goethite nanorods in an external magnetic field within Onsager-Parsons density functional theory. The goethite rods are represented by monodisperse, charged spherocylinders with a permanent magnetic moment along the rod main axis, forcing the particles to align parallel to the magnetic field at low field strength. The intrinsic diamagnetic susceptibility anisometry of the rods is negative which leads to a preferred perpendicular orientation at higher field strength. It is shown that these counteracting effects may give rise to intricate phase behavior, including a pronounced stability of biaxial nematic order and the presence of reentrant phase transitions and demixing phenomena. The effect of the applied field on the nematic-to-smectic transition will also be addressed.
Apparatus for storing high magnetic fields having reduced mechanical forces and reduced magnetic pollution
Prueitt, M.L.; Mueller, F.M.; Smith, J.L.
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.
Apparatus for storing high magnetic fields having reduced mechanical forces and reduced magnetic pollution
Prueitt, Melvin L. (Los Alamos, NM); Mueller, Fred M. (Los Alamos, NM); Smith, James L. (Los Alamos, NM)
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.
Chapman, Nicholas L.; Matthews, Tristan G.; Novak, Giles [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Davidson, Jacqueline A. [School of Physics, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009 (Australia); Goldsmith, Paul F. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 264-782, Pasadena, CA 91109 (United States); Houde, Martin [Department of Physics and Astronomy, University of Western Ontario, London, ON (Canada); Kwon, Woojin; Looney, Leslie W. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States); Li Zhiyun [Astronomy Department, University of Virginia, Charlottesville, VA 22904 (United States); Matthews, Brenda [Herzberg Institute of Astrophysics, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Peng Ruisheng [Caltech Submillimeter Observatory, 111 Nowelo Street, Hilo, HI 96720 (United States); Vaillancourt, John E. [SOFIA Science Center, Universities Space Research Association, NASA Ames Research Center, MS 232-11, Moffett Field, CA 94035-0001 (United States); Volgenau, Nikolaus H. [California Institute of Technology, Owens Valley Radio Observatory, Big Pine, CA 93513 (United States)
We present 350 {mu}m polarization observations of four low-mass cores containing Class 0 protostars: L483, L1157, L1448-IRS2, and Serp-FIR1. This is the second paper in a larger survey aimed at testing magnetically regulated models for core-collapse. One key prediction of these models is that the mean magnetic field in a core should be aligned with the symmetry axis (minor axis) of the flattened young stellar object inner envelope (aka pseudodisk). Furthermore, the field should exhibit a pinched or hourglass-shaped morphology as gravity drags the field inward toward the central protostar. We combine our results for the four cores with results for three similar cores that were published in the first paper from our survey. An analysis of the 350 {mu}m polarization data for the seven cores yields evidence of a positive correlation between mean field direction and pseudodisk symmetry axis. Our rough estimate for the probability of obtaining by pure chance a correlation as strong as the one we found is about 5%. In addition, we combine together data for multiple cores to create a source-averaged magnetic field map having improved signal-to-noise ratio, and this map shows good agreement between mean field direction and pseudodisk axis (they are within 15 Degree-Sign ). We also see hints of a magnetic pinch in the source-averaged map. We conclude that core-scale magnetic fields appear to be strong enough to guide gas infall, as predicted by the magnetically regulated models. Finally, we find evidence of a positive correlation between core magnetic field direction and bipolar outflow axis.
The National High Magnetic Field Laboratory
Weston, Ken
of Contents Table of contents cHaPTeR 1 The Year in Review 6 cHaPTeR 3 Magnets & Materials 44 cHaPTeR 4 User The year in Review cHaPTeR 1 The Year in Review by Gregory Boebinger, MagLab Director 2012: Another
Dynamics of molecular superrotors in external magnetic field
Korobenko, Aleksey
We excite diatomic oxygen and nitrogen to high rotational states with an optical centrifuge and study their dynamics in external magnetic field. Ion imaging is employed to directly visualize, and follow in time, the rotation plane of molecular superrotors. The two different mechanisms of interaction between the magnetic field and the molecular angular momentum in paramagnetic oxygen and non-magnetic nitrogen lead to the qualitatively different behaviour. In nitrogen, we observe the precession of the molecular angular momentum around the field vector. In oxygen, strong spin-rotation coupling results in faster and richer dynamics, encompassing the splitting of the rotation plane in three separate components. As the centrifuged molecules evolve with no significant dispersion of the molecular wave function, the observed magnetic interaction presents an efficient mechanism for controlling the plane of molecular rotation.
Torsional Oscillations of Relativistic Stars with Dipole Magnetic Fields
H. Sotani; K. D. Kokkotas; N. Stergioulas
We present the formalism and numerical results for torsional oscillations of relativistic stars endowed with a strong dipole magnetic field. We do a systematic search of parameter space by computing torsional mode frequencies for various values of the harmonic index $\\ell$ and for various overtones, using an extended sample of models of compact stars, varying in mass, high-density equation of state and crust model. We show that torsional mode frequencies are sensitive to the crust model if the high-density equation of state is very stiff. In addition, torsional mode frequencies are drastically affected by a dipole magnetic field, if the latter has a strength exceeding roughly $10^{15}$G and we find that the magnetic field effects are sensitive to the adopted crust model. Using our extended numerical results we derive empirical relations for the effect of the magnetic field on torsional modes as well as for the crust thickness. We compare our numerical results to observed frequencies in SGRs and find that certain high-density EoS and mass values are favored over others in the non-magnetized limit. On the other hand, if the magnetic field is strong, then its effect has to be taken into account in attempts to formulate a theory of asteroseismology for magnetars.
Cyclic behavior of solar inter-network magnetic field
Jin, Chunlan
Solar inter-network magnetic field is the weakest component of solar magnetism, but contributes most of the solar surface magnetic flux. The study on its origin has been constrained by the inadequate tempo-spatial resolution and sensitivity of polarization observations. With dramatic advances in spatial resolution and detective sensitivity, solar spectro-polarimetry provided by the Solar Optical Telescope aboard Hinode in an interval from solar minimum to maximum of cycle 24 opens an unprecedented opportunity to study the cyclic behavior of solar inter-network magnetic field. More than 1000 Hinode magnetograms observed from 2007 January to 2014 August are selected in the study. It has been found that there is a very slight correlation between sunspot number and magnetic field at the inter-network flux spectrum. From solar minimum to maximum of cycle 24, the flux density of solar inter-network field is invariant, which is 10$\\pm1$ G. The observations suggest that the inter-network magnetic field does not arise...
Magnetic Propulsion of Intense Lithium Streams in a Tokamak Magnetic Field
Leonid E. Zakharov
The paper gives the theory of magnetic propulsion of liquid lithium streams and their stability in tokamaks. In the approximation of a thin flowing layer the MHD equations are reduced to one integro-differential equation which takes into account the propulsion effect, viscosity and the drag force due to magnetic pumping and other interactions with the magnetic field. A criterion is obtained for the stabilization of the ''sausage'' instability of the streams by centrifugal force.
Quantum field theory in a magnetic field: From quantum chromodynamics to graphene and Dirac semimetals
Miransky, Vladimir A
A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chira...
Locked modes and magnetic field errors in MST
Almagri, A.F.; Assadi, S.; Prager, S.C.; Sarff, J.S.; Kerst, D.W.
In the MST reversed field pinch magnetic oscillations become stationary (locked) in the lab frame as a result of a process involving interactions between the modes, sawteeth, and field errors. Several helical modes become phase locked to each other to form a rotating localized disturbance, the disturbance locks to an impulsive field error generated at a sawtooth crash, the error fields grow monotonically after locking (perhaps due to an unstable interaction between the modes and field error), and over the tens of milliseconds of growth confinement degrades and the discharge eventually terminates. Field error control has been partially successful in eliminating locking.
Brushed permanent magnet DC MLC motor operation in an external magnetic field
Yun, J.; St Aubin, J.; Rathee, S.; Fallone, B. G. [Department of Physics, University of Alberta, 11322-89 Avenue, Edmonton, Alberta T6G 2G7 (Canada) and Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada) and Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Department of Physics, University of Alberta, 11322-89 Avenue, Edmonton, Alberta T6G 2G7 (Canada); Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada) and Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada)
Purpose: Linac-MR systems for real-time image-guided radiotherapy will utilize the multileaf collimators (MLCs) to perform conformal radiotherapy and tumor tracking. The MLCs would be exposed to the external fringe magnetic fields of the linac-MR hybrid systems. Therefore, an experimental investigation of the effect of an external magnetic field on the brushed permanent magnet DC motors used in some MLC systems was performed. Methods: The changes in motor speed and current were measured for varying external magnetic field strengths up to 2000 G generated by an EEV electromagnet. These changes in motor characteristics were measured for three orientations of the motor in the external magnetic field, mimicking changes in motor orientations due to installation and/or collimator rotations. In addition, the functionality of the associated magnetic motor encoder was tested. The tested motors are used with the Varian 120 leaf Millennium MLC (Maxon Motor half leaf and full leaf motors) and the Varian 52 leaf MKII MLC (MicroMo Electronics leaf motor) including a carriage motor (MicroMo Electronics). Results: In most cases, the magnetic encoder of the motors failed prior to any damage to the gearbox or the permanent magnet motor itself. This sets an upper limit of the external magnetic field strength on the motor function. The measured limits of the external magnetic fields were found to vary by the motor type. The leaf motor used with a Varian 52 leaf MKII MLC system tolerated up to 450{+-}10 G. The carriage motor tolerated up to 2000{+-}10 G field. The motors used with the Varian 120 leaf Millennium MLC system were found to tolerate a maximum of 600{+-}10 G. Conclusions: The current Varian MLC system motors can be used for real-time image-guided radiotherapy coupled to a linac-MR system, provided the fringe magnetic fields at their locations are below the determined tolerance levels. With the fringe magnetic fields of linac-MR systems expected to be larger than the tolerance levels determined, some form of magnetic shielding would be required.
Magnetic field diffusion modeling of a small enclosed firing system
Warne, L.K.; Merewether, K.O.
Intense magnetic fields exist in the immediate vicinity of a lightning strike (and near power lines). Conducting barriers increase the rise time (and thus decrease the rise rate) interior to the barrier, but typically do not prevent penetration of the magnetic field, since the lightning current fall time may be larger than the barrier diffusion time. Thus, substantial energy is present in the interior field, although the degradation of rise rate makes it more difficult to couple into electrical circuits. This report assesses the threat posed by the diffusive magnetic field to interior components and wire loops (where voltages are induced). Analytical and numerical bounding analyses are carried out on a pill box shaped conducting barrier to develop estimates for the worst case magnetic field threats inside the system. Worst case induced voltages and energies are estimated and compared with threshold charge voltages and energies on the output capacitor of the system. Variability of these quantities with respect to design parameters are indicated. The interior magnetic field and induced voltage estimates given in this report can be used as excitations for more detailed interior and component models.
Photon and Axion Splitting in an Inhomogeneous Magnetic Field
E. I. Guendelman
The axion photon system in an external magnetic field, when the direction of propagation of axions and photons is orthogonal to the direction of the external magnetic field, displays a continuous axion-photon duality symmetry in the limit the axion mass is neglected. The conservation law that follow in this effective 2+1 dimensional theory from this symmetry is obtained. The magnetic field interaction is seen to be equivalent to first order to the interaction of a complex charged field with an external electric potential, where this ficticious "electric potential" is proportional to the external magnetic field. This allows one to solve for the scattering amplitudes using already known scalar QED results. From the scalar QED analog the axion and the photon are symmetric and antisymmetric combinations of particle and antiparticle. If one considers therefore scattering experiments in which the two spatial dimensions of the effective theory are involved non trivially, one observes that both particle and antiparticle components of photons and axions are preferentially scattered in different directions, thus producing the splitting or decomposition of the photon and axion into their particle and antiparticle components in an inhomogeneous magnetic field. This observable in principle effect is of first order in the axion photon coupling, unlike the "light shining through a wall phenomena ", which is second order.
Magnetic Fields of Uranus and Neptune: Metallic Fluid Hydrogen
Nellis, W J
The magnetic fields of the Ice Giant Planets Uranus and Neptune (U/N) are unique in the solar system. Based on a substantial database measured on Earth for representative planetary fluids at representative dynamic pressures up to 200 GPa (2 Mbar) and a few 1000 K, the complex magnetic fields of U/N are (i) probably made primarily by degenerate metallic fluid H (MFH) at or near the crossover from the H-He envelopes to Ice cores at ~100 GPa (Mbar) pressures and normalized radii of ~90% of the radii of U/N; (ii) because those magnetic fields are made relatively close to the surfaces of U/N, non-dipolar fields can be expected; (iii) the Ice cores are most probably a heterogeneous fluid mixture of H, N, O, C, Fe/Ni and silicate-oxides and their mutual reaction products at high pressures and temperatures; (iv) the shapes of the magnetic fields are probably caused by weak coupling between rotational motions of U/N and convective motions of conducting fluids in dynamos that make those magnetic fields. Ironically, the...
Properties of an axially periodic magnetic field in a betatron
Zvontsov, A.A.; Filinova, V.A.; Chakhlov, V.L.
It is shown by solving an equation for the vector potential A (r, z) of the magnetic field that under appropriate conditions the focusing properties of a betatron magnetic field are periodic with respect to the z coordinate. Under these conditions there may be several equilibrium orbits lying in parallel planes z = 0, z = z/sub 01/ xxx, z = mz/sub 01/ in the accelerator. An equation is derived for the distance z/sub 01/ between the equilibrium orbit planes for a given orbit radius r/sub 0/ and field decay exponent n/sub 0/. The operation of such accelerators is described.
Primordial Magnetic Fields from the Post-Inflationary Universe
Takeshi Kobayashi
We explore cosmological magnetogenesis in the post-inflationary universe, when the inflaton oscillates around its potential minimum and the universe is effectively dominated by cold matter. During this epoch prior to reheating, large-scale magnetic fields can be significantly produced by the cosmological background. By considering magnetogenesis both during and after inflation, we demonstrate that magnetic fields stronger than 10^{-15} G can be generated on Mpc scales without having strong couplings in the theory, or producing too large electric fields that would dominate the universe.
Primordial Magnetic Fields from the Post-Inflationary Universe
Kobayashi, Takeshi
We explore cosmological magnetogenesis in the post-inflationary universe, when the inflaton oscillates around its potential minimum and the universe is effectively dominated by cold matter. During this epoch prior to reheating, large-scale magnetic fields can be significantly produced by the cosmological background. By considering magnetogenesis both during and after inflation, we demonstrate that magnetic fields stronger than 10^{-15} G can be generated on Mpc scales without having strong couplings in the theory, or producing too large electric fields that would dominate the universe.
Treating Cancer with Strong Magnetic Fields and Ultrasound
Dr. Friedwardt Winterberg
It is proposed to treat cancer by the combination of a strong magnetic field with intense ultrasound. At the low electrical conductivity of tissue the magnetic field is not frozen into the tissue, and oscillates against the tissue which is brought into rapid oscillation by the ultrasound. As a result, a rapidly oscillating electric field is induced in the tissue, strong enough to disrupt cancer cell replication. Unlike radio frequency waves, which have been proposed for this purpose, ultrasound can be easily focused onto the regions to be treated. This method has the potential for the complete eradication of the tumor.
Simple basis for hydrogenic atoms in magnetic fields
Gallas, J.A.C.
A field-dependent hydrogenic basis is used to obtain the evolution of the energy spectrum of atoms in strong (approx.10/sup 8/ G) and uniform magnetic fields. The basis allows results to be derived analytically. Numerical values for the first 13 excited states of hydrogen are found to be in very good agreement with much more elaborate calculations of Smith et al. and of Brandi. In addition, the possibility of having a remnant type of degeneracy in the presence of the magnetic field is investigated.
Magnetic Fields in Quantum Degenerate Systems and in Vacuum
H. Perez Rojas; E. Rodriguez Querts
We consider self-magnetization of charged and neutral vector bosons bearing a magnetic moment in a gas and in vacuum. For charged vector bosons (W bosons) a divergence of the magnetization in both the medium and the electroweak vacuum occurs for the critical field B=B_{wc}=m_{w}^{2}/e. For B>B_{wc} the system is unstable. This behavior suggests the occurrence of a phase transition at B=B_{c}, where the field is self-consistently maintained. This mechanism actually prevents $B$ from reaching the critical value B_{c}. For virtual neutral vector bosons bearing an anomalous magnetic moment, the ground state has a similar behavior for B=B_{nbc}=m_{nb}^{2}/q . The magnetization in the medium is associated to a Bose-Einstein condensate and we conjecture a similar condensate occurs also in the case of vacuum. The model is applied to virtual electron-positron pairs bosonization in a magnetic field B \\sim B_{pc}\\lesssim 2m_{e}^{2}/e, where m_e is the electron mass. This would lead also to vacuum self-magnetization in QED, where in both cases the symmetry breaking is due to a condensate of quasi-massless particles.
Equilibrium and stability studies of plasmas confined in a dipole magnetic field using magnetic measurements
Karim, Ishtak
The Levitated Dipole Experiment (LDX) is the first experiment of its kind to use a levitated current ring to confine a plasma in a dipole magnetic field. Unlike most other confinement devices, plasma compressibility ...
An Efficient Control of a Series Connected Two-Synchronous Motor 5-Phase with Non Sinusoidal EMF Supplied by a Single 5-leg VSI: Experimental and
Paris-Sud XI, Université de
Synchronous Machines (PMSM) connected in series. Even if the Electro-Motive Force (EMF) are trapezoidal
Magnetic field re-arrangement after prominence eruption
Kopp, R.A.; Poletto, G.
It has long been known that magnetic reconnection plays a fundamental role in a variety of solar events. Although mainly invoked in flare problems, large-scale loops interconnecting active regions, evolving coronal hole boundaries, the solar magnetic cycle itself, provide different evidence of phenomena which involve magnetic reconnection. A further example might be given by the magnetic field rearrangement which occurs after the eruption of a prominence. Since most often a prominence reforms after its disappearance and may be observed at about the same position it occupied before erupting, the magnetic field has to undergo a temporary disruption to relax back, via reconnection, to a configuration similar to the previous one. The above sequence of events is best observable in the case of two-ribbon (2-R) flares but most probably is associated with all filament eruptions. Even if the explanation of the magnetic field rearrangement after 2-R flares in terms of reconnection is generally accepted, the lack of a three-dimensional model capable of describing the field reconfiguration, has prevented, up to now, a thorough analysis of its topology as traced by H..cap alpha../x-ray loops. The purpose of the present work is to present a numerical technique which enables one to predict and visualize the reconnected configuration, at any time t, and therefore allows one to make a significant comparison of observations and model predictions throughout the whole process. 5 refs., 3 figs.
Coil Winding for the Series-Connected Hybrid Magnet Mark D. Bird, National High Magnetic Field Laboratory
Weston, Ken
Coil Winding for the Series-Connected Hybrid Magnet Mark D. Bird, National High Magnetic Field will produce for MagLab users magnetic fields of 36T featuring unprecedented (1ppm) homogeneity. Winding of the superconducting coil, the largest component of the magnet windings, is well underway. The superconducting coil
Baldner, Charles S.; Basu, Sarbani [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT, 06520-8101 (United States); Antia, H. M. [Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005 (India); Larson, Timothy P., E-mail: firstname.lastname@example.com [Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305-4085 (United States)
Normal modes of oscillation of the Sun are useful probes of the solar interior. In this work, we use the even-order splitting coefficients to study the evolution of magnetic fields in the convection zone over solar cycle 23, assuming that the frequency splitting is only due to rotation and a large-scale magnetic field. We find that the data are best fit by a combination of a poloidal field and a double-peaked near-surface toroidal field. The toroidal fields are centered at r {sub 0} = 0.999 R {sub sun} and r = 0.996 R {sub sun} and are confined to the near-surface layers. The poloidal field is a dipole field. The peak strength of the poloidal field is 124 +- 17 G. The toroidal field peaks at 380 +- 30 G and 1.4 +- 0.2 kG for the shallower and deeper fields, respectively. The field strengths are highly correlated with surface activity. The toroidal field strength shows a hysteresis-like effect when compared to the global 10.7 cm radio flux. The poloidal field strength shows evidence of saturation at high activity.
Memorandum Approval of a Permanenet Variance Regarding Static Magnetic Fields at Brookhaven National Laboratory (Variance 1021)
Broader source: Energy.gov [DOE]
Approval of a Permanenet Variance Regarding Static Magnetic Fields at Brookhaven National Laboratory (Variance 1021)
Proposal for study of $\\pi^{-}$ nucleur collisions in nuclear emulsion exposed in a pulsed magnetic field
CERN. Geneva. SPS Experiments Committee
Proposal for study of $\\pi^{-}$ nucleur collisions in nuclear emulsion exposed in a pulsed magnetic field
Electrostatic waves in carbon nanotubes with an axial magnetic field
Abdikian, Alireza [Department of Physics, Malayer University, Malayer 65719-95863 (Iran, Islamic Republic of)] [Department of Physics, Malayer University, Malayer 65719-95863 (Iran, Islamic Republic of); Bagheri, Mehran [Laser and Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran 19835-63113 (Iran, Islamic Republic of)] [Laser and Plasma Research Institute, Shahid Beheshti University, G. C., Evin, Tehran 19835-63113 (Iran, Islamic Republic of)
Based on a linearized hydrodynamic model and within the quasi-static approximation, the dispersion relation of electrostatic waves propagating through single-walled carbon nanotubes subject to an axial magnetic field is theoretically explored. In the classical limit, we obtain two main possible waves which in turn are divided into two branches, a low-frequency acoustical and a high-frequency optical plasmon branch. In the quantum case, we have found that the dispersion relation is substantially modified when the electron wavelength becomes large enough compared to the propagation wavelength of the electrostatic waves in the quantum plasma. We also show that the axial magnetic field manifest itself on the perturbed electron density through the quantum term and gives rise to the propagation of the electrostatic waves within the quantum plasma. As a result, the effect of the magnetic field is pronounced in the plasma dispersion relations in such a way that their curves approach to zero when the magnetic field is weak; and for the strong magnetic field, they asymptotically meet the constant lines.
Potts models with magnetic field: arithmetic, geometry, and computation
Shival Dasu; Matilde Marcolli
We give a sheaf theoretic interpretation of Potts models with external magnetic field, in terms of constructible sheaves and their Euler characteristics. We show that the polynomial countability question for the hypersurfaces defined by the vanishing of the partition function is affected by changes in the magnetic field: elementary examples suffice to see non-polynomially countable cases that become polynomially countable after a perturbation of the magnetic field. The same recursive formula for the Grothendieck classes, under edge-doubling operations, holds as in the case without magnetic field, but the closed formulae for specific examples like banana graphs differ in the presence of magnetic field. We give examples of computation of the Euler characteristic with compact support, for the set of real zeros, and find a similar exponential growth with the size of the graph. This can be viewed as a measure of topological and algorithmic complexity. We also consider the computational complexity question for evaluations of the polynomial, and show both tractable and NP-hard examples, using dynamic programming.
Permanent magnet flowmeter having improved output terminal means
August, Charles (Darien, IL); Myers, Harry J. (Downers Grove, IL)
Disclosed is an improved permanent magnet flowmeter capable of withstanding bending stresses in the direction of induced emf signals. The flowmeter includes a unique terminal arrangement integrally formed with the flowmeter by trepanning opposing wall sections of the flowmeter body. The terminal arrangement provides increased flowmeter sensitivity by increasing the strength of the induced emf signals.
The Cost of Superconducting Magnets as a Function of Stored Energy and Design Magnetic Induction Times the Field Volume
Green, Mike; Green, M.A.; Strauss, B.P.
By various theorems one can relate the capital cost of superconducting magnets to the magnetic energy stored within that magnet. This is particularly true for magnet where the cost is dominated by the structure needed to carry the magnetic forces. One can also relate the cost of the magnet to the product of the magnetic induction and the field volume. The relationship used to estimate the cost the magnet is a function of the type of magnet it is. This paper updates the cost functions given in two papers that were published in the early 1990 s. The costs (escalated to 2007 dollars) of large numbers of LTS magnets are plotted against stored energy and magnetic field time field volume. Escalated costs for magnets built since the early 1990 s are added to the plots.
Magnetic Backgrounds and Noncommutative Field Theory
Richard J. Szabo
This paper is a rudimentary introduction, geared at non-specialists, to how noncommutative field theories arise in physics and their applications to string theory, particle physics and condensed matter systems.
Ewertowski, Bartek; Basu, Shantanu, E-mail: firstname.lastname@example.com [Department of Physics and Astronomy, Western University, London, Ontario N6A 3K7 (Canada)] [Department of Physics and Astronomy, Western University, London, Ontario N6A 3K7 (Canada)
Starting with a mathematical boundary value problem for the magnetic vector potential in an axisymmetric cylindrical coordinate system, we derive a general solution for any arbitrary current distribution using the method of Green's functions. We use this to derive an analytic form for an hourglass magnetic field pattern created by electrical currents that are concentrated near (but not confined within) the equatorial plane of a cylindrical coordinate system. Our solution is not characterized by a cusp at the equatorial plane, as in previous solutions based on a current sheet. The pattern we derive provides a very good fit to hourglass magnetic field patterns emerging from three-dimensional numerical simulations of core formation, and can in principle be used for source-fitting of observed magnetic hourglass patterns.
The Superconducting Magnet Division at Brookhaven National Laboratory (BNL) has been carrying out design, engineering, and technology development of high performance magnets for future accelerators. High Temperature Superconductors (HTS) play a major role in the BNL vision of a few high performance interaction region (IR) magnets that would be placed in a machine about ten years from now. This paper presents the engineering design of a ''react and wind'' Nb{sub 3}Sn magnet that will provide a 12 Tesla background field on HTS coils. In addition, the coil production tooling as well as the most recent 10-turn R&D coil test results will be discussed.
The measurement and analysis of the magnetic field of a synchrotron light source magnet
Graf, Udo Werner
section of the magnet shows the symmetric distribution of the coils about the center line of the magnet. The iron yolk which surrounds the conductors is thermally insulated to enhance the efficiency of the cooling system. The entire magnet assembly... of charged particles in a 21 conductor that are exposed to an electric and a magnetic field. The force experienced by these particles is characterized by the Lorentz Equation, F=q(E+vxB) (3) The conductor used for the Hall probe has the shape of a...
Nuclear Energy Response in the EMF27 Study
Kim, Son H.; Wada, Kenichi; Kurosawa, Atsushi; Roberts, Matthew
The nuclear energy response for mitigating global climate change across eighteen participating models of the EMF27 study is investigated. Diverse perspectives on the future role of nuclear power in the global energy system are evident in the broad range of nuclear power contributions from participating models of the study. In the Baseline scenario without climate policy, nuclear electricity generation and shares span 0 � 66 EJ/ year and 0 - 25% in 2100 for all models, with a median nuclear electricity generation of 39 EJ/year (1,389 GWe at 90% capacity factor) and median share of 9%. The role of nuclear energy increased under the climate policy scenarios. The median of nuclear energy use across all models doubled in the 450 ppm CO2e scenario with a nuclear electricity generation of 67 EJ/year (2,352 GWe at 90% capacity factor) and share of 17% in 2100. The broad range of nuclear electricity generation (11 � 214 EJ/year) and shares (2 - 38%) in 2100 of the 450 ppm CO2e scenario reflect differences in the technology choice behavior, technology assumptions and competitiveness of low carbon technologies. Greater clarification of nuclear fuel cycle issues and risk factors associated with nuclear energy use are necessary for understanding the nuclear deployment constraints imposed in models and for improving the assessment of the nuclear energy potential in addressing climate change.
The Magnetic Fields of Classical T Tauri Stars
Christopher M. Johns-Krull
We report new magnetic field measurements for 14 classical T Tauri stars (CTTSs). We combine these data with one previous field determination in order to compare our observed field strengths with the field strengths predicted by magnetospheric accretion models. We use literature data on the stellar mass, radius, rotation period, and disk accretion rate to predict the field strength that should be present on each of our stars according to these magnetospheric accretion models. We show that our measured field values do not correlate with the field strengths predicted by simple magnetospheric accretion theory. We also use our field strength measurements and literature X-ray luminosity data to test a recent relationship expressing X-ray luminosity as a function of surface magnetic flux derived from various solar feature and main sequence star measurements. We find that the T Tauri stars we have observed have weaker than expected X-ray emission by over an order of magnitude on average using this relationship. We suggest the cause for this is actually a result of the very strong fields on these stars which decreases the efficiency with which gas motions in the photosphere can tangle magnetic flux tubes in the corona.
Conceptual Design of the 45 T Hybrid Magnet at the Nijmegen High Field Magnet Laboratory
Wiegers, SAJ; Bird, M D; Rook, J; Perenboom, J A A J; Wiegers, S A J; Bonito-Oliva, A; den Ouden, A
A 45 T Hybrid Magnet System is being developed at the Nijmegen High Field Magnet Laboratory as part of the Nijmegen Center for Advanced Spectroscopy. The 45 T Hybrid Magnet System will be used in combination with far-infra-red light produced by a Free Electron Laser under construction directly adjacent to the High Field Magnet Laboratory. The superconducting outsert magnet will consist of three CICC coils wound on a single coil form, using Nb3Sn strands. A test program for strand and cable qualification is underway. The CICC will carry 13 kA and the coils will produce 12 T on axis field in a 600 mm warm bore. The nominal operating temperature will be 4.5 K maintained with forced-flow supercritical helium. The insert magnet will produce 33 T at 40 kA in a 32 mm bore consuming 20 MW, and will consist of four coils. The insert magnet will be galvanically and mechanically isolated from the outsert magnet. Complete system availability for users is expected in 2014. In this paper we will report on the conceptual de...
Solar nebula magnetic fields recorded in the Semarkona meteorite
Fu, Roger R.; Weiss, Benjamin P.; Lima, Eduardo A.; Harrison, Richard J.; Bai, Xue-Ning; Desch, Steven J.; Ebel, Denton S.; Suavet, Clement; Wang, Huapei; Glenn, David; Le Sage, David; Kasama, Takeshi; Walsworth, Ronald L.; Kuan, Aaron T.
images of all three vector 492 � components of the magnetic field produced by the sample in the plane of NV sensors using 493 � optically-detected magnetic resonance (ODMR) spectroscopy. In this technique, described by 494 � Le Sage et al. (74... � Figure 1. Dusty olivine-bearing chondrules from the Semarkona meteorite. (A) Optical 224 � photomicrograph of chondrule DOC4 showing the location of dusty olivine grains. Image taken 225 � in reflected light with crossed polarizers. (B) Annular...
Development of fast cooling pulsed magnets at the Wuhan National High Magnetic Field Center
Peng, Tao; Sun, Quqin; Zhao, Jianlong; Jiang, Fan; Li, Liang; Xu, Qiang [Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan (China)] [Wuhan National High Magnetic Field Center, Huazhong University of Science and Technology, Wuhan (China); Herlach, Fritz [Department of Physics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)] [Department of Physics, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)
Pulsed magnets with fast cooling channels have been developed at the Wuhan National High Magnetic Field Center. Between the inner and outer sections of a coil wound with a continuous length of CuNb wire, G10 rods with cross section 4 mm � 5 mm were inserted as spacers around the entire circumference, parallel to the coil axis. The free space between adjacent rods is 6 mm. The liquid nitrogen flows freely in the channels between these rods, and in the direction perpendicular to the rods through grooves provided in the rods. For a typical 60 T pulsed magnetic field with pulse duration of 40 ms, the cooling time between subsequent pulses is reduced from 160 min to 35 min. Subsequently, the same technology was applied to a 50 T magnet with 300 ms pulse duration. The cooling time of this magnet was reduced from 480 min to 65 min.
Towards Integrated Design and Modeling of High Field Accelerator Magnets
Caspi, S.; Ferracin, P.
The next generation of superconducting accelerator magnets will most likely use a brittle conductor (such as Nb{sub 3}Sn), generate fields around 18 T, handle forces that are 3-4 times higher than in the present LHC dipoles, and store energy that starts to make accelerator magnets look like fusion magnets. To meet the challenge and reduce the complexity, magnet design will have to be more innovative and better integrated. The recent design of several high field superconducting magnets have now benefited from the integration between CAD (e.g. ProE), magnetic analysis tools (e.g. TOSCA) and structural analysis tools (e.g. ANSYS). Not only it is now possible to address complex issues such as stress in magnet ends, but the analysis can be better detailed an extended into new areas previously too difficult to address. Integrated thermal, electrical and structural analysis can be followed from assembly and cool-down through excitation and quench propagation. In this paper we report on the integrated design approach, discuss analysis results and point out areas of future interest.
Observation of Dirac Monopoles in a Synthetic Magnetic Field
M. W. Ray; E. Ruokokoski; S. Kandel; M. M�tt�nen; D. S. Hall
Magnetic monopoles --- particles that behave as isolated north or south magnetic poles --- have been the subject of speculation since the first detailed observations of magnetism several hundred years ago. Numerous theoretical investigations and hitherto unsuccessful experimental searches have followed Dirac's 1931 development of a theory of monopoles consistent with both quantum mechanics and the gauge invariance of the electromagnetic field. The existence of even a single Dirac magnetic monopole would have far-reaching physical consequences, most famously explaining the quantization of electric charge. Although analogues of magnetic monopoles have been found in exotic spin-ices and other systems, there has been no direct experimental observation of Dirac monopoles within a medium described by a quantum field, such as superfluid helium-3. Here we demonstrate the controlled creation of Dirac monopoles in the synthetic magnetic field produced by a spinor Bose-Einstein condensate. Monopoles are identified, in both experiments and matching numerical simulations, at the termini of vortex lines within the condensate. By directly imaging such a vortex line, the presence of a monopole may be discerned from the experimental data alone. These real-space images provide conclusive and long-awaited experimental evidence of the existence of Dirac monopoles. Our result provides an unprecedented opportunity to observe and manipulate these quantum-mechanical entities in a controlled environment.
Electric and magnetic fields and field derivatives from lightning stepped leaders and first return strokes measured at distances
Florida, University of
Electric and magnetic fields and field derivatives from lightning stepped leaders and first return; published 5 September 2008. [1] Using electric and magnetic field and field derivative sensors arrayed over-peak width of the stepped-leader/return-stroke electric field waveform; the stepped-leader electric field
Enhancement of accelerating field of microwave cavities by magnetic insulation
Stratakis, D.; Gallardo, J.; Palmer, R.B.
Limitations on the maximum achievable accelerating gradient of microwave cavities can strongly influence the performance, length, and cost of particle accelerators. Gradient limitations are widely believed to be initiated by electron emission from the cavity surfaces. Here, we show that the deleterious effects of field emission are effectively suppressed by applying a tangential magnetic field to the cavity walls. With the aid of numerical simulations we compute the field strength required to insulate an 805 MHz cavity and estimate the cavity's tolerances to typical experimental errors such as magnet misalignments and positioning errors. Then, we review an experimental program, currently under progress, to further study the concept. Finally, we report on two specific examples that illustrate the feasibility of magnetic insulation into prospective particle accelerator applications.
New dynamo pattern revealed by solar helical magnetic fields
Zhang, Hongqi; Pevtsov, A; Gao, Yu; Xu, Haiqing; Sokoloff, D D; Kuzanyan, K
Previously unobservable mirror asymmetry of the solar magnetic field -- a key ingredient of the dynamo mechanism which is believed to drive the 11-year activity cycle -- has now been measured. This was achieved through systematic monitoring of solar active regions carried out for more than 20 years at observatories in Mees, Huairou, and Mitaka. In this paper we report on detailed analysis of vector magnetic field data, obtained at Huairou Solar Observing Station in China. Electric current helicity (the product of current and magnetic field component in the same direction) was estimated from the data and a latitude-time plot of solar helicity during the last two solar cycles has been produced. We find that like sunspots helicity patterns propagate equatorwards but unlike sunspot polarity helicity in each solar hemisphere does not change sign from cycle to cycle - confirming the theory. There are, however, two significant time-latitudinal domains in each cycle when the sign does briefly invert. Our findings she...
Electron vortex beams in a magnetic field and spin filter
Debashree Chowdhury; Banasri Basu; Pratul Bandyopadhyay
We investigate the propagation of electron vortex beams in a magnetic field. It is pointed out that when electron vortex beams carrying orbital angular momentum propagate in a magnetic field, the Berry curvature associated with the scalar electron moving in a cyclic path around the vortex line is modified from that in free space. This alters the spin-orbit interaction, which affects the propagation of nonparaxial beams. The electron vortex beams with tilted vortex lead to spin Hall effect in free space. In presence of a magnetic field in time space we have spin filtering such that either positive or negative spin states emerge in spin Hall currents with clustering of spin $\\frac{1}{2}$ states.
Holographic non-Fermi liquid in a background magnetic field
Basu, Pallab; He Jianyang; Mukherjee, Anindya; Shieh, Hsien-Hang [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, B.C. V6T 1Z1 (Canada)
We study the effects of a nonzero magnetic field on a class of 2+1 dimensional non-Fermi liquids, recently found in [Hong Liu, John McGreevy, and David Vegh, arXiv:0903.2477.] by considering properties of a Fermionic probe in an extremal AdS{sup 4} black hole background. Introducing a similar fermionic probe in a dyonic AdS{sup 4} black hole geometry, we find that the effect of a magnetic field could be incorporated in a rescaling of the probe fermion's charge. From this simple fact, we observe interesting effects like gradual disappearance of the Fermi surface and quasiparticle peaks at large magnetic fields and changes in other properties of the system. We also find Landau level like structures and oscillatory phenomena similar to the de-Haas-van Alphen effect.
Engineering Weyl nodes in Dirac semimetals by a magnetic field
E. V. Gorbar; V. A. Miransky; I. A. Shovkovy
We study the phase diagram of a Dirac semimetal in a magnetic field at a nonzero charge density. It is shown that there exists a critical value of the chemical potential at which a first-order phase transition takes place. At subcritical values of the chemical potential the ground state is a gapped state with a dynamically generated Dirac mass and a broken chiral symmetry. The supercritical phase is the normal (gapless) phase with a nontrivial chiral structure: it is a Weyl semimetal with a pair of Weyl nodes for each of the original Dirac points. The nodes are separated by a dynamically induced chiral shift. The direction of the chiral shift coincides with that of the magnetic field and its magnitude is determined by the quasiparticle charge density, the strength of the magnetic field, and the strength of the interaction. The rearrangement of the Fermi surface accompanying this phase transition is described.
Radiofrequency hydrogen ion source with permanent magnets providing axial magnetic field
Oikawa, Kohei, E-mail: firstname.lastname@example.com; Saito, Yuta; Komizunai, Shota; Takahashi, Kazunori; Ando, Akira [Department of Electrical Engineering, Tohoku University, Sendai 980-8579 (Japan)] [Department of Electrical Engineering, Tohoku University, Sendai 980-8579 (Japan)
Uniform axial magnetic field of about 70 G is applied to a radiofrequency (rf) hydrogen ion source by arrays of permanent magnets. The plasma density and electron temperature downstream of the source and near the magnetic filter are compared with those in the previously described ion source, where the axial field has been applied by two solenoids. The source is operated at ?350 kHz and above 10 kW rf power with a field-effect-transistor-based invertor power supply in 1.5 Pa hydrogen. The results show that the plasma density of ?10{sup 19} m{sup ?3} near the source exit and ?10{sup 18} m{sup ?3} near the magnetic filter can be obtained, which are higher than those with the solenoids.
Chiral Magnetic Effect in Protoneutron Stars and Magnetic Field Spectral Evolution
Sigl, G�nter
We investigate the evolution of the chiral magnetic instability in a protoneutron star and compute the resulting magnetic power and helicity spectra. The instability may act during the early cooling phase of the hot protoneutron star after supernova core collapse, where it can contribute to the buildup of magnetic fields of strength up to the order of $10^{14}$ G. The maximal field strengths generated by this instability, however, depend considerably on the temperature of the protoneutron star, on density fluctuations and turbulence spectrum of the medium. At the end of the hot cooling phase the magnetic field tends to be concentrated around the submillimeter to cm scale, where it is subject to slow resistive damping.
Polarizable vacuum analysis of electric and magnetic fields
Xing-Hao Ye
The electric and magnetic fields are investigated on the basis of quantum vacuum. The analysis of the electromagnetic energy and force indicates that an electric field is a polarized distribution of the vacuum virtual dipoles, and that a magnetic field in vacuum is a rearrangement of the vacuum polarization. It means that an electromagnetic wave is a successional changing of the vacuum polarization in space. Also, it is found that the average half length of the virtual dipoles around an elementary charge is a=2.8 *10^(-15)m. The result leads to the step distribution of the field energy around an electron, the relation between the fine structure constant and the vacuum polarization distribution, and an extremely high energy density of the electromagnetic field.
Quantum field theory in a magnetic field: From quantum chromodynamics to graphene and Dirac semimetals
Vladimir A. Miransky; Igor A. Shovkovy
A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chiral magnetic and separation effects, we also review their possible phenomenological implications in heavy-ion collisions and compact stars. We also discuss the application of the magnetic catalysis ideas for the description of the quantum Hall effect in monolayer and bilayer graphene, and conclude that the generalized magnetic catalysis, including both the magnetic catalysis condensates and the quantum Hall ferromagnetic ones, lies at the basis of this phenomenon. We also consider how an external magnetic field affects the underlying physics in a class of three-dimensional quasirelativistic condensed matter systems, Dirac semimetals. While at sufficiently low temperatures and zero density of charge carriers, such semimetals are expected to reveal the regime of the magnetic catalysis, the regime of Weyl semimetals with chiral asymmetry is realized at nonzero density...
Quantum field theory in a magnetic field: From quantum chromodynamics to graphene and Dirac semimetals
Vladimir A. Miransky; Igor A. Shovkovy
A range of quantum field theoretical phenomena driven by external magnetic fields and their applications in relativistic systems and quasirelativistic condensed matter ones, such as graphene and Dirac/Weyl semimetals, are reviewed. We start by introducing the underlying physics of the magnetic catalysis. The dimensional reduction of the low-energy dynamics of relativistic fermions in an external magnetic field is explained and its role in catalyzing spontaneous symmetry breaking is emphasized. The general theoretical consideration is supplemented by the analysis of the magnetic catalysis in quantum electrodynamics, chromodynamics and quasirelativistic models relevant for condensed matter physics. By generalizing the ideas of the magnetic catalysis to the case of nonzero density and temperature, we argue that other interesting phenomena take place. The chiral magnetic and chiral separation effects are perhaps the most interesting among them. In addition to the general discussion of the physics underlying chiral magnetic and separation effects, we also review their possible phenomenological implications in heavy-ion collisions and compact stars. We also discuss the application of the magnetic catalysis ideas for the description of the quantum Hall effect in monolayer and bilayer graphene, and conclude that the generalized magnetic catalysis, including both the magnetic catalysis condensates and the quantum Hall ferromagnetic ones, lies at the basis of this phenomenon. We also consider how an external magnetic field affects the underlying physics in a class of three-dimensional quasirelativistic condensed matter systems, Dirac semimetals. While at sufficiently low temperatures and zero density of charge carriers, such semimetals are expected to reveal the regime of the magnetic catalysis, the regime of Weyl semimetals with chiral asymmetry is realized at nonzero density...
Transmit field pattern control for high field magnetic resonance imaging with integrated RF current sources�
Kurpad, Krishna Nagaraj
The primary design criterion for RF transmit coils for MRI is uniform transverse magnetic (B1) field. Currently, most high frequency transmit coils are designed as periodic, symmetric structures that are resonant at the ...
Homogenous BSCCO-2212 Round Wires for Very High Field Magnets
Dr. Scott Campbell
The performance demands on modern particle accelerators generate a relentless push towards higher field magnets. In turn, advanced high field magnet development places increased demands on superconducting materials. Nb3Sn conductors have been used to achieve 16 T in a prototype dipole magnet and are thought to have the capability for {approx}18 T for accelerator magnets (primarily dipoles but also higher order multipole magnets). However there have been suggestions and proposals for such magnets higher than 20 T. The High Energy Physics Community (HEP) has identified important new physics opportunities that are enabled by extremely high field magnets: 20 to 50 T solenoids for muon cooling in a muon collider (impact: understanding of neutrinos and dark matter); and 20+ T dipoles and quadrupoles for high energy hadron colliders (impact: discovery reach far beyond present). This proposal addresses the latest SBIR solicitation that calls for grant applications that seek to develop new or improved superconducting wire technologies for magnets that operate at a minimum of 12 Tesla (T) field, with increases up to 15 to 20 T sought in the near future (three to five years). The long-term development of accelerator magnets with fields greater than 20 T will require superconducting wires having significantly better high-field properties than those possessed by current Nb{sub 3}Sn or other A15 based wires. Given the existing materials science base for Bi-2212 wire processing, we believe that Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (Bi-2212) round wires can be produced in km-long piece lengths with properties suitable to meet both the near term and long term needs of the HEP community. The key advance will be the translation of this materials science base into a robust, high-yield wire technology. While the processing and application of A15 materials have advanced to a much higher level than those of the copper oxide-based, high T{sub c} (HTS) counterparts, the HTS materials have the very significant advantage of an extremely high H{sub c2}. For this reason, Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y} (Bi-2212, or 2212) in the form of a multifilamentary Ag alloy matrix composite is beginning to attract the interest of the magnet community for future extremely high-field magnets or magnet-insert coils for 4.2K operation. Fig. 1 shows an example of excellent JE (engineering current density) in Bi-2212 round wire at fields up to 45 T, demonstrating the potential for high field applications of this material. For comparison, the Nb{sub 3}Sn wires used in magnets in the 16-18 T range typically perform with J{sub E} in the range 200-500 A/mm{sup 2}; the Bi-2212 wire retains this level of performance to fields at least as high as 45 T, and probably significantly higher. Bi-2212 conductors have in fact been used to generate a 25 T field in a superconducting insert magnet. These two factors- the very high field critical current performance of Bi-2212, and the already demonstrated capability of this material for high field magnets up to 25 T, strongly suggest this material as a leading contender for the next generation high field superconducting (HFS) wire. This potential was recognized by the US Academy of Science's Committee on Opportunities in High Magnetic Field Science. Their report of the same name specifically calls out the high field potential for this material, and suggests that 30 T magnets appear feasible based on the performance of 2212. There are several requirements for HFS conductors. The most obvious is J{sub E} (B, T), the engineering current density at the field and temperature of operation. As shown in Fig. 1, Bi-2212 excels in this regard. Stability requirements for magnets dictate that the effective filament diameter should be less than 30 micrometers, something that Bi-2212 multifilamentary wire can uniquely satisfy among the HFS superconducting wire technologies. Additional requirements include mechanical properties that prevent stress limitation of J{sub E} at the operating conditions, resistive transition index (n-value) suffic
Ultra-low field nuclear magnetic resonance and magnetic resonance imaging to discriminate and identify materials
Kraus, Robert H. (Los Alamos, NM); Matlashov, Andrei N. (Los Alamos, NM); Espy, Michelle A. (Los Alamos, NM); Volegov, Petr L. (Los Alamos, NM)
An ultra-low magnetic field NMR system can non-invasively examine containers. Database matching techniques can then identify hazardous materials within the containers. Ultra-low field NMR systems are ideal for this purpose because they do not require large powerful magnets and because they can examine materials enclosed in conductive shells such as lead shells. The NMR examination technique can be combined with ultra-low field NMR imaging, where an NMR image is obtained and analyzed to identify target volumes. Spatial sensitivity encoding can also be used to identify target volumes. After the target volumes are identified the NMR measurement technique can be used to identify their contents.
On collisional diffusion in a stochastic magnetic field
Abdullaev, S. S. [Forschungszentrum J�lich GmbH, Institut f�r Energie- und Klimaforschung - Plasmaphysik, EURATOM Association, 52425 J�lich (Germany)] [Forschungszentrum J�lich GmbH, Institut f�r Energie- und Klimaforschung - Plasmaphysik, EURATOM Association, 52425 J�lich (Germany)
The effect of particle collisions on the transport in a stochastic magnetic field in tokamaks is investigated. The model of resonant magnetic perturbations generated by external coils at the plasma edge is used for the stochastic magnetic field. The particle collisions are simulated by a random walk process along the magnetic field lines and the jumps across the field lines at the collision instants. The dependencies of the local diffusion coefficients on the mean free path ?{sub mfp}, the diffusion coefficients of field lines D{sub FL}, and the collisional diffusion coefficients, ?{sub ?} are studied. Based on these numerical data and the heuristic arguments, the empirical formula, D{sub r}=?{sub ?}+v{sub ||}D{sub FL}/(1+L{sub c}/?{sub mfp}), for the local diffusion coefficient is proposed, where L{sub c} is the characteristic length of order of the connection length l{sub c}=?qR{sub 0}, q is the safety factor, R{sub 0} is the major radius. The formula quite well describes the results of numerical simulations. In the limiting cases, the formula describes the Rechester-Rosenbluth and Laval scalings.
Heat pulse propagation in chaotic 3-dimensional magnetic fields
D. del-Castillo-Negrete; D. Blazevski
Heat pulse propagation in $3$-D chaotic magnetic fields is studied by solving the parallel heat transport equation using a Lagrangian-Green's function (LG) method. The LG method provides an efficient and accurate technique that circumvents limitations of finite elements and finite difference methods. The main two problems addressed are: (i) The dependence of the radial transport on the magnetic field stochasticity (controlled by the amplitude of the perturbation, $\\epsilon$); and (ii) The role of reversed shear configurations on pulse propagation. In all the cases considered there are no magnetic flux surfaces. However, radial transport is observed to depend strongly on $\\epsilon$ due to the presence of high-order magnetic islands and Cantori that act as quasi-transport barriers that preclude the radial penetration of heat pulses within physically relevant time scale. The dependence of the magnetic field connection length, $\\ell_B$, on $\\epsilon$ is studied in detail. The decay rate of the temperature maximum, $\\langle T \\rangle_{max}(t)$, the time delay of the temperature response as function of the radius, $\\tau$, and the radial heat flux $\\langle {{\\bf q}\\cdot {\\hat e}_\\psi} \\rangle$, are also studied as functions of the magnetic field stochasticity and $\\ell_B$. In all cases, the scaling of $\\langle T \\rangle_{max}$ with $t$ transitions from sub-diffusive, $\\langle T \\rangle_{max} \\sim t^{-1/4}$, at short times ($\\chi_\\parallel t 10^5$). A strong dependence on $\\epsilon$ is also observed on $\\tau$ and $\\langle {{\\bf q}\\cdot {\\hat e}_\\psi} \\rangle$. The radial propagation of pulses in fully chaotic fields considerably slows down in the shear reversal region and, as a result, $\\tau$, in reversed shear configurations is an order of magnitude longer than the one in monotonic $q$-profiles.
Formation of magnetic discontinuities through superposition of force-free magnetic fields: Periodic boundaries
Kumar, Dinesh; Bhattacharyya, R. [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India)] [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India); Smolarkiewicz, P. K. [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)] [European Centre for Medium-Range Weather Forecasts, Reading RG2 9AX (United Kingdom)
In ideal magnetohydrodynamics characterized by an infinite electrical conductivity, the magnetic flux across an arbitrary fluid surface is conserved in time. The magnetofluid then can be partitioned into contiguous subvolumes of fluid, each of which entraps its own subsystem of magnetic flux. During dynamical evolution of the magnetofluid, these subvolumes press into each other; and in the process, two such subvolumes may come into direct contact while ejecting a third interstitial subvolume. Depending on the orientations of magnetic fields of the two interacting subvolumes, the magnetic field at the common surface of interaction may become discontinuous and a current sheet is formed there. This process of current sheet formation and their subsequent decay is believed to be a plausible mechanism for coronal heating and may also be responsible for various eruptive phenomena at the solar corona. In this work, we explore this theoretical concept through numerical simulations of a viscous, incompressible magnetofluid characterized by infinite electrical conductivity. In particular, we show that if the initial magnetic field is prescribed by superposition of two linear force-free fields with different torsion coefficients, then formation of current sheets are numerically realizable in the neighborhood of magnetic nulls.
Kinetic models of current sheets with a sheared magnetic field
Mingalev, O. V.; Mingalev, I. V.; Mel'nik, M. N. [Russian Academy of Sciences, Polar Geophysical Institute, Cola Science Center (Russian Federation); Artemyev, A. V.; Malova, H. V.; Popov, V. Yu. [Russian Academy of Sciences, Space Research Institute (Russian Federation); Chao, Shen [Chinese Academy of Sciences, Center for Space Science and Applied Research (China); Zelenyi, L. M. [Russian Academy of Sciences, Space Research Institute (Russian Federation)
Thin current sheets, whose existence in the Earth's magnetotail is confirmed by numerous spacecraft measurements, are studied analytically and numerically. The thickness of such sheets is on the order of the ion Larmor radius, and the normal component of the magnetic field (B{sub z}) in the sheet is almost constant, while the tangential (B{sub x}) and shear (B{sub y}) components depend on the transverse coordinate z. The current density in the sheet also has two self-consistent components (j{sub x} and j{sub y}, respectively), and the magnetic field lines are deformed and do not lie in a single plane. To study such quasi-one-dimensional current configurations, two kinetic models are used, in particular, a numerical model based on the particle-in-cell method and an analytical model. The calculated results show that two different modes of the self-consistent shear magnetic field B{sub y} and, accordingly, two thin current sheet configurations can exist for the same input parameters. For the mode with an antisymmetric z profile of the B{sub y} component, the magnetic field lines within the sheet are twisted, whereas the profiles of the plasma density, current density component j{sub y}, and magnetic field component B{sub x} differ slightly from those in the case of a shearless magnetic field (B{sub y} = 0). For the symmetric B{sub y} mode, the magnetic field lines lie in a curved surface. In this case, the plasma density in the sheet varies slightly and the current sheet is two times thicker. Analysis of the dependence of the current sheet structure on the flow anisotropy shows that the sheet thickness decreases significantly with decreasing ratio between the thermal and drift plasma velocities, which is caused by the dynamics of quasi-adiabatic ions. It is shown that the results of the analytical and numerical models are in good agreement. The problems of application of these models to describe current sheets at the magnetopause and near magnetic reconnection regions are discussed.
SQUID-Detected Magnetic Resonance Imaging in MicroteslaFields
Moessle, Michael; Hatridge, Michael; Clarke, John
Magnetic resonance imaging (MRI) has developed into a powerful clinical tool for imaging the human body (1). This technique is based on nuclear magnetic resonance (NMR) of protons (2, 3) in a static magnetic field B{sub 0}. An applied radiofrequency pulse causes the protons to precess about B{sub 0} at their Larmor frequency {nu}{sub 0} = ({gamma}/2{pi})B{sub 0}, where {gamma} is the gyromagnetic ratio; {gamma}/2{pi} = 42.58 MHz/tesla. The precessing protons generate an oscillating magnetic field and hence a voltage in a nearby coil that is amplified and recorded. The application of three-dimensional magnetic field gradients specifies a unique magnetic field and thus an NMR frequency in each voxel of the subject, so that with appropriate encoding of the signals one can acquire a complete image (4). Most clinical MRI systems involve magnetic fields generated by superconducting magnets, and the current trend is to higher magnetic fields than the widely used 1.5-T systems (5). Nonetheless, there is ongoing interest in the development of less expensive imagers operating at lower fields. Commercially available 0.2-T systems based on permanent magnets offer both lower cost and a more open access than their higher-field counterparts, at the expense of signal-to-noise-ratio (SNR) and spatial resolution. At the still lower field of 0.03 mT maintained by a conventional, room-temperature solenoid, Connolly and co-workers (6, 7) obtain good spatial resolution and signal-to-noise ratio (SNR) by prepolarizing the protons in a field B{sub p} of 0.3 T. Prepolarization (8) enhances the magnetic moment of an ensemble of protons over that produced by the lower precession field; after the polarizing field is removed, the higher magnetic moment produces a correspondingly larger signal during its precession in B{sub 0}. Using the same method, Stepisnik et al. (9) obtained MR images in the Earth's magnetic field ({approx} 50 {micro}T). Alternatively, one can enhance the signal amplitude in MRI using laser polarized noble gases such as {sup 3}He or {sup 129}Xe (10-12). Hyperpolarized gases were used successfully to image the human lung in fields on the order of several mT (13-15). To overcome the sensitivity loss of Faraday detection at low frequencies, ultrasensitive magnetometers based on the Superconducting QUantum Interference Device (SQUID) (16) are used to detect NMR and MRI signals (17-24). Recently, SQUID-based MRI systems capable of acquiring in vivo images have appeared. For example, in the 10-mT system of Seton et al. (18) signals are coupled to a SQUID via a superconducting tuned circuit, while Clarke and coworkers (22, 25, 26) developed a system at 132 {micro}T with an untuned input circuit coupled to a SQUID. In a quite different approach, atomic magnetometers have been used recently to detect the magnetization (27) and NMR signal (28) of hyperpolarized gases. This technique could potentially be used for low-field MRI in the future. The goal of this review is to summarize the current state-of-the-art of MRI in microtesla fields detected with SQUIDs. The principles of SQUIDs and NMR are briefly reviewed. We show that very narrow NMR linewidths can be achieved in low magnetic fields that are quite inhomogeneous, with illustrative examples from spectroscopy. After describing our ultralow-field MRI system, we present a variety of images. We demonstrate that in microtesla fields the longitudinal relaxation T{sub 1} is much more material dependent than is the case in high fields; this results in a substantial improvement in 'T{sub 1}-weighted contrast imaging'. After outlining the first attempts to combine microtesla NMR with magnetoencephalography (MEG) (29), we conclude with a discussion of future directions.
Screening magnetic fields by superconductors: A simple model
Caputo, J.-G., E-mail: firstname.lastname@example.com [Laboratoire de Math�matiques, INSA de Rouen, Avenue de l'Universit�, 76801 Saint-Etienne du Rouvray (France); Gozzelino, L.; Laviano, F.; Ghigo, G.; Gerbaldo, R. [Department of Applied Science and Technology, Politecnico di Torino, 10129, Torino (Italy); Noudem, J.; Thimont, Y.; Bernstein, P. [CRISMAT/LUSAC, Physics Department, Universit� de Caen (France)
We introduce a simple approach to evaluate the magnetic field distribution around superconducting samples, based on the London equations; the elementary variable is the vector potential. This procedure has no adjustable parameters, only the sample geometry and the London length, ?, determine the solution. This approach was validated by comparing the induction field calculated to the one measured above MgB{sub 2} disks of different diameters, at 20?K and for applied fields lower than 0.4?T. The model can be applied if the flux line penetration inside the sample can be neglected when calculating the induction field distribution outside the superconductor. We conclude by showing on a cup-shape geometry how one can design a magnetic shield satisfying a specific constraint.
Hull, Charles L. H.; Plambeck, Richard L.; Bower, Geoffrey C.; Heiles, Carl; Meredith Hughes, A. [Astronomy Department and Radio Astronomy Laboratory, University of California, Berkeley, CA 94720-3411 (United States); Bolatto, Alberto D.; Jameson, Katherine; Mundy, Lee; Pound, Marc W. [Astronomy Department and Laboratory for Millimeter-wave Astronomy, University of Maryland, College Park, MD 20742 (United States); Carpenter, John M.; Lamb, James W.; Pillai, Thushara [Department of Astronomy, California Institute of Technology, 1200 E. California Blvd., MC 249-17, Pasadena, CA 91125 (United States); Crutcher, Richard M.; Hakobian, Nicholas S.; Kwon, Woojin; Looney, Leslie W. [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 W Green Street, Urbana, IL 61801 (United States); Fiege, Jason D.; Franzmann, Erica [Department of Physics and Astronomy, University of Manitoba, Winnipeg, MB R3T 2N2 (Canada); Houde, Martin [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Matthews, Brenda C., E-mail: firstname.lastname@example.com [Department of Physics and Astronomy, University of Victoria, 3800 Finnerty Rd., Victoria, BC V8P 5C2 (Canada); and others
We present results of {lambda}1.3 mm dust-polarization observations toward 16 nearby, low-mass protostars, mapped with {approx}2.''5 resolution at CARMA. The results show that magnetic fields in protostellar cores on scales of {approx}1000 AU are not tightly aligned with outflows from the protostars. Rather, the data are consistent with scenarios where outflows and magnetic fields are preferentially misaligned (perpendicular), or where they are randomly aligned. If one assumes that outflows emerge along the rotation axes of circumstellar disks, and that the outflows have not disrupted the fields in the surrounding material, then our results imply that the disks are not aligned with the fields in the cores from which they formed.
Dynamics of Mesoscale Magnetic Field in Diffusive Shock Acceleration
P. H. Diamond; M. A. Malkov
We present a theory for the generation of mesoscale ($kr_{g}\\ll 1$, where $r_{g}$ is the cosmic ray gyroradius) magnetic fields during diffusive shock acceleration. The decay or modulational instability of resonantly excited Alfven waves scattering off ambient density perturbations in the shock environment naturally generates larger scale fields. For a broad spectrum of perturbations, the physical mechanism of energy transfer is random refraction, represented by diffusion of Alfven wave packet in $k-$space. The scattering field can be produced directly by the decay instability or by the Drury instability, a hydrodynamic instability driven by the cosmic ray pressure gradient. This process is of interest to acceleration since it generates waves of longer wavelength, and so enables the confinement and acceleration of higher energy particles. This process also limits the intensity of resonantly generated turbulent magnetic field on $r_{g}$ scales.
Nuclear magnetic resonances in weak fields
Mitchell, Richard Warren
' The snalInr 30. voltages necessary in this case would allow the use of parallel banks of batteries, which should increase the stability of the cux xwnt. Lf batteries are used as a ycwsr source, no. 6 wire should be a convenient siss for prodcci...&g fields uy to 106 gauss in a sole noid of the dinensions used here. Pour banks of batterissx each bank containing five batteries in serissx should pxxxvide ~te stabili RIGDIILATTOM FXELUi 'Ae two wain difficulties with the pxesent nodulation scheme...
Ground-state magnetic phase diagram of bow-tie graphene nanoflakes in external magnetic field
Sza?owski, Karol, E-mail: email@example.com, E-mail: firstname.lastname@example.com [Department of Solid State Physics, Faculty of Physics and Applied Informatics, University of ?�d?, ul. Pomorska 149/153, 90-236 ?�d? (Poland)
The magnetic phase diagram of a ground state is studied theoretically for graphene nanoflakes of bow-tie shape and various sizes in external in-plane magnetic field. The tight-binding Hamiltonian supplemented with Hubbard term is used to model the electronic structure of the systems in question. The existence of the antiferromagnetic phase with magnetic moments localized at the sides of the bow-tie is found for low field and a field-induced spin-flip transition to ferromagnetic state is predicted to occur in charge-undoped structures. For small nanoflake doped with a single charge carrier, the low-field phase is ferrimagnetic and a metamagnetic transition to ferromagnetic ordering can be forced by the field. The critical field is found to decrease with increasing size of the nanoflake. The influence of diagonal and off-diagonal disorder on the mentioned magnetic properties is studied. The effect of off-diagonal disorder is found to be more important than that of diagonal disorder, leading to significantly widened distribution of critical fields for disordered population of nanoflakes.
Plasma Equilibrium in a Magnetic Field with Stochastic Regions
J.A. Krommes and Allan H. Reiman
The nature of plasma equilibrium in a magnetic field with stochastic regions is examined. It is shown that the magnetic differential equation that determines the equilibrium Pfirsch-Schluter currents can be cast in a form similar to various nonlinear equations for a turbulent plasma, allowing application of the mathematical methods of statistical turbulence theory. An analytically tractable model, previously studied in the context of resonance-broadening theory, is applied with particular attention paid to the periodicity constraints required in toroidal configurations. It is shown that even a very weak radial diffusion of the magnetic field lines can have a significant effect on the equilibrium in the neighborhood of the rational surfaces, strongly modifying the near-resonant Pfirsch-Schluter currents. Implications for the numerical calculation of 3D equilibria are discussed
Ferrofluid aggregates phase transitions in the planar magnetic field
V. F. Kovalenko; M. V. Petrychuk; B. M. Tanygin; S. I. Shulyma
The influence of the cyclic heating and cooling on properties of the aggregates (aka "ferrofluid clusters") in a ferrofluid, which made on the basis of magnetite nanoparticles, are investigated. The heating of the ferrofluid layer with such aggregates leads to equalization of the concentration between high- and low-concentrated phases. The temperature of the equalization of the phase concentrations was determined at different values of an external constant magnetic field, which was applied parallel to the layer of the ferrofluid. The temperature of the destruction of a periodic structure of the magnetic aggregates, which were formed during cooling of a homogeneous phase of the ferrofluid, was obtained at the different values of the applied external magnetic field.
Tunable dynamic response of magnetic gels: impact of structural properties and magnetic fields
Mitsusuke Tarama; Peet Cremer; Dmitry Y. Borin; Stefan Odenbach; Hartmut L�wen; Andreas M. Menzel
Ferrogels and magnetic elastomers feature mechanical properties that can be reversibly tuned from outside through magnetic fields. Here we concentrate on the question how their dynamic response can be adjusted. The influence of three factors on the dynamic behavior is demonstrated using appropriate minimal models: first, the orientational memory imprinted into one class of the materials during their synthesis; second, the structural arrangement of the magnetic particles in the materials; and third, the strength of an external magnetic field. To illustrate the latter point, structural data are extracted from a real experimental sample and analyzed. Understanding how internal structural properties and external influences impact the dominant dynamical properties helps to design materials that optimize the requested behavior.
Localization of disordered bosons and magnets in random fields
Yu, Xiaoquan, E-mail: email@example.com [International School for Advanced Studies (SISSA), via Bonomea 265, 34136 Trieste (Italy) [International School for Advanced Studies (SISSA), via Bonomea 265, 34136 Trieste (Italy); New Zealand Institute for Advanced Study, Centre for Theoretical Chemistry and Physics, Massey University, Auckland 0745 (New Zealand); M�ller, Markus, E-mail: email@example.com [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151 Trieste (Italy)] [The Abdus Salam International Center for Theoretical Physics, Strada Costiera 11, 34151 Trieste (Italy)
We study localization properties of disordered bosons and spins in random fields at zero temperature. We focus on two representatives of different symmetry classes, hard-core bosons (XY magnets) and Ising magnets in random transverse fields, and contrast their physical properties. We describe localization properties using a locator expansion on general lattices. For 1d Ising chains, we find non-analytic behavior of the localization length as a function of energy at ?=0, ?{sup ?1}(?)=?{sup ?1}(0)+A|?|{sup ?}, with ? vanishing at criticality. This contrasts with the much smoother behavior predicted for XY magnets. We use these results to approach the ordering transition on Bethe lattices of large connectivity K, which mimic the limit of high dimensionality. In both models, in the paramagnetic phase with uniform disorder, the localization length is found to have a local maximum at ?=0. For the Ising model, we find activated scaling at the phase transition, in agreement with infinite randomness studies. In the Ising model long range order is found to arise due to a delocalization and condensation initiated at ?=0, without a closing mobility gap. We find that Ising systems establish order on much sparser (fractal) subgraphs than XY models. Possible implications of these results for finite-dimensional systems are discussed. -- Highlights: �Study of localization properties of disordered bosons and spins in random fields. �Comparison between XY magnets (hard-core bosons) and Ising magnets. �Analysis of the nature of the magnetic transition in strong quenched disorder. �Ising magnets: activated scaling, no closing mobility gap at the transition. �Ising order emerges on sparser (fractal) support than XY order.
Lesson Summary Students will learn about the magnetic fields of
Mojzsis, Stephen J.
Lesson Summary Students will learn about the magnetic fields of the Sun and Earth. This activity if they have learned them in another context and you can remind them about those lessons in this activity minutes 1. Read and review the lesson plan 2. Gather required materials 3. Form student teams Exploring
Relationship Between Solar Wind Speed and Coronal Magnetic Field Properties
Fujiki, Ken'ichi; Iju, Tomoya; Hakamada, Kazuyuki; Kojima, Masayoshi
We have studied the relationship between the solar-wind speed $[V]$ and the coronal magnetic-field properties (a flux expansion factor [$f$] and photospheric magnetic-field strength [$B_{\\mathrm{S}}$]) at all latitudes using data of interplanetary scintillation and solar magnetic field obtained for 24 years from 1986 to 2009. Using a cross-correlation analyses, we verified that $V$ is inversely proportional to $f$ and found that $V$ tends to increase with $B_{\\mathrm{S}}$ if $f$ is the same. As a consequence, we find that $V$ has extremely good linear correlation with $B_{\\mathrm{S}}/f$. However, this linear relation of $V$ and $B_{\\mathrm{S}}/f$ cannot be used for predicting the solar-wind velocity without information on the solar-wind mass flux. We discuss why the inverse relation between $V$ and $f$ has been successfully used for solar-wind velocity prediction, even though it does not explicitly include the mass flux and magnetic-field strength, which are important physical parameters for solar-wind accele...
Energy Eigenvalues of Kemmer Equation for a Homogeneous Magnetic Field
A. Havare; K. Sogut
This article illustrates a completely algebraic method to obtain the energy levels of a massive spin-1 particle moving in a constant magnetic field. In the process to obtain the energy levels the wave function was written by harmonic oscillator solutions.
Universal formulae for thermoelectric transport with magnetic field and disorder
Andrea Amoretti; Daniele Musso
We obtain explicit expressions for the thermoelectric transport coefficients of a strongly coupled, planar medium in the presence of an orthogonal magnetic field and disorder. The computations are performed within the gauge/gravity framework, however we propose and argue for a possible universal relevance of the results relying on comparisons and extensions of previous hydrodynamical analyses and experimental data.
A linear helicon plasma device with controllable magnetic field gradient
Barada, Kshitish K.; Chattopadhyay, P. K.; Ghosh, J.; Kumar, Sunil; Saxena, Y. C. [Institute for Plasma Research, Bhat, Gandhinagar, Gujarat 382428 (India)
Current free double layers (CFDLs) are localized potential structures having spatial dimensions - Debye lengths and potential drops of more than local electron temperature across them. CFDLs do not need a current for them to be sustained and hence they differ from the current driven double layers. Helicon antenna produced plasmas in an expanded chamber along with an expanding magnetic field have shown the existence of CFDL near the expansion region. A helicon plasma device has been designed, fabricated, and installed in the Institute for Plasma Research, India to study the role of maximum magnetic field gradient as well as its location with respect to the geometrical expansion region of the chamber in CFDL formation. The special feature of this machine consisting of two chambers of different radii is its capability of producing different magnetic field gradients near the physical boundary between the two chambers either by changing current in one particular coil in the direction opposite to that in other coils and/or by varying the position of this particular coil. Although, the machine is primarily designed for CFDL experiments, it is also capable of carrying out many basic plasma physics experiments such as wave propagation, wave coupling, and plasma instabilities in a varying magnetic field topology. In this paper, we will present the details of the machine construction, its specialties, and some preliminary results about the production and characterization of helicon plasma in this machine.
Massive disk outflows mediated by extreme magnetic fields
Shiber, Sagiv; Soker, Noam
We argue that magnetic fields amplified within a very high accretion-rate disk around main sequence stars can lead to the formation of massive bipolar outflows that can remove most of the disk's mass and energy. This efficient directional removal of energy and mass allows the high accretion-rate disk to be built. We construct thick disks where the magnetic fields are amplified by an Alpha-Omega dynamo in the disk, bringing the fluctuating components of the magnetic field to be much stronger than the large-scale component. By examining the possible activity of the magnetic fields we conclude that main sequence stars can accrete mass at very high rates, up to 0.01Mo/yr for solar type stars, and up to 1Mo/yr for very massive stars. Such energetic outflows can account for the powering of some eruptive objects, such as merging main sequence stars, major eruptions of luminous blue variables, such as the Great Eruption of Eta Carinae, and other intermediate luminosity optical transients (ILOTs; Red Novae; Red Transi...
Triggering for Magnetic Field Measurements of the LCLS Undulators
Hacker, Kirsten
A triggering system for magnetic field measurements of the LCLS undulators has been built with a National Instruments PXI-1002 and a Xylinx FPGA board. The system generates single triggers at specified positions, regardless of encoder sensor jitter about a linear scale.
Constraining Cosmic Magnetic Fields by a Measurement of
Erdmann, Martin
. . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 7 Energy-Energy-Correlations 51 7.1 Definition of Energy-EnergyConstraining Cosmic Magnetic Fields by a Measurement of Energy-Energy-Correlations with the Pierre Ultra High Energy Cosmic Rays 3 2.1 Cosmic Rays with Energies below 4 Ee
Mathematical Modeling of Magnetic Field Profiles in Superconductors
Wetton, Brian
Mathematical Modeling of Magnetic Field Profiles in Superconductors Michael Lindstrom, Brian Wetton, Rob Kiefl March 1, 2011 Abstract One of the defining characteristics of a superconductor is the Meiss results. 1 Introduction to the Problem and the Model Superconductors are materials which exhibit a phase
Universal formulae for thermoelectric transport with magnetic field and disorder
Amoretti, Andrea
We obtain explicit expressions for the thermoelectric transport coefficients of a strongly coupled, planar medium in the presence of an orthogonal magnetic field and disorder. The computations are performed within the gauge/gravity framework, however we propose and argue for a possible universal relevance of the results relying on comparisons and extensions of previous hydrodynamical analyses and experimental data.
Photon-Axion conversions in transversely inhomogeneous magnetic fields
Javier Redondo
We compute the photon-axion conversion probability in an external magnetic field with a strong transverse gradient in the eikonal approximation for plane waves. We find it typically smaller than a comparable uniform case. Some insights into the phenomenon of photon-axion splitting are given.
Spin flip probability of electron in a uniform magnetic field
Hammond, Richard T. [Department of Physics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina and Army Research Office, Research Triangle Park, North Carolina 27703 (United States)
The probability that an electromagnetic wave can flip the spin of an electron is calculated. It is assumed that the electron resides in a uniform magnetic field and interacts with an incoming electromagnetic pulse. The scattering matrix is constructed and the time needed to flip the spin is calculated.
Method for the detection of a magnetic field utilizing a magnetic vortex
Novosad, Valentyn (Chicago, IL); Buchanan, Kristen (Batavia, IL)
The determination of the strength of an in-plane magnetic field utilizing one or more magnetically-soft, ferromagnetic member, having a shape, size and material whereas a single magnetic vortex is formed at remanence in each ferromagnetic member. The preferred shape is a thin circle, or dot. Multiple ferromagnetic members can also be stacked on-top of each other and separated by a non-magnetic spacer. The resulting sensor is hysteresis free. The sensor's sensitivity, and magnetic saturation characteristics may be easily tuned by simply altering the material, size, shape, or a combination thereof to match the desired sensitivity and saturation characteristics. The sensor is self-resetting at remanence and therefore does not require any pinning techniques.
Current induced perpendicular-magnetic-anisotropy racetrack memory with magnetic field assistance
Zhang, Y.; Klein, J.-O.; Chappert, C.; Ravelosona, D. [IEF, University of Paris-Sud, Orsay 91405 (France); UMR8622, CNRS, Orsay 91405 (France); Zhao, W. S., E-mail: email@example.com [IEF, University of Paris-Sud, Orsay 91405 (France); UMR8622, CNRS, Orsay 91405 (France); Electronics and Information Engineering School, University of Beihang, Beijing 100191 (China)
High current density is indispensable to shift domain walls (DWs) in magnetic nanowires, which limits the using of racetrack memory (RM) for low power and high density purposes. In this paper, we present perpendicular-magnetic-anisotropy (PMA) Co/Ni RM with global magnetic field assistance, which lowers the current density for DW motion. By using a compact model of PMA RM and 40?nm design kit, we perform mixed simulation to validate the functionality of this structure and analyze its density potential. Stochastic DW motion behavior has been taken into account and statistical Monte-Carlo simulations are carried out to evaluate its reliability performance.
Development of high temperature superconductors for magnetic field applications
Larbalestier, D.C.
The key requirement for magnetic field applications of high temperature superconductor (HTS) materials is to have conductors with high transport critical current density available for magnet builders. After 3 or 4 years of being without any such object, conductor makers have had recent success in producing simple conductor prototypes. These have permitted the construction of simple HTS magnets having self fields exceeding 1 tesla at 4K. Thus the scientific feasibility of making powerful HTS magnets has been demonstrated. Attention to the technological aspects of making HTS conductors for magnets with strong flux pinning and reduced superconducting granularity is now sensible and attractive. However, extrinsic defects such as filament sausaging, cracking, misaligned grains and other perturbation to long range current flow must be controlled at a low level if the benefit of intrinsic improvements to the critical current density is to be maintained in the conductor form. Due to the great complexity of the HTS materials, there is sometimes confusion as to whether a given sample has an intrinsically or extrinsically limited critical current density. Systematic microstructure variation experiments and resistive transition analysis are shown to be particularly helpful in this phase of conductor development.
Noninvasive valve monitor using constant magnetic and/or DC electromagnetic field
Casada, Donald A. (Knoxville, TN); Haynes, Howard D. (Knoxville, TN)
One or more sources of steady magnetic field are carefully located on the outside of a valve body. The constant magnetic field is transmitted into the valve body and valve internals. A magnetic field detector carefully located on the outside of the valve body detects the intensity of the magnetic field at its location. As the position of a valve internal part is changed, there is an alteration in the magnetic field in the valve, and a consequent change in the detected magnetic field. Changes in the detected signal provide an indication of the position and motion of the valve internals.
Apparatus for unilateral generation of a homogeneous magnetic field
Fukushima, E.; Rath, A.R.; Roeder, S.B.W.
An apparatus for unilaterally producing a substantially homogeneous magnetic field. The apparatus includes two circular electromagnet coils, a small coil and a large coil, which are coaxial with one another and which are separated by a distance equal to one-half the difference in the radius of the two coils. By appropriate selection of electrical currents, which are passed through the coils in opposite directions, a region of homogeneous magnetic field is formed. This region is centered on the common axis of the two coils, at a point on the axis which is at a distance from the small coil equal to one-half the radius of the small coil, and which is on the opposite side of the small coil from the large coil. The apparatus has particular application in the field of diagnostic medical NMR and other NMR applications.
Apparatus for unilateral generation of a homogeneous magnetic field
Fukushima, Eiichi (Los Alamos, NM); Rath, Alan R. (San Diego, CA); Roeder, Stephen B. W. (La Mesa, CA)
An apparatus for unilaterally producing a substantially homogeneous magnetic field. The apparatus includes two circular electromagnet coils, a small coil and a large coil, which are coaxial with one another and which are separated by a distance equal to one-half the difference in the radius of the two coils. By appropriate selection of electrical currents, which are passed through the coil in opposite directions, a region of homogeneous magnetic field is formed. This region is centered on the common axis of the two coils, at a point on the axis which is at a distance from the small coil equal to one-half the radius of the small coil, and which is on the opposite side of the small coil from the large coil. The apparatus has particular application in the field of diagnostic medical NMR and other NMR applications.
Anisotropies in magnetic field evolution and local Lyapunov exponents
Tang, X.Z.; Boozer, A.H.
The natural occurrence of small scale structures and the extreme anisotropy in the evolution of a magnetic field embedded in a conducting flow is interpreted in terms of the properties of the local Lyapunov exponents along the various local characteristic (un)stable directions for the Lagrangian flow trajectories. The local Lyapunov exponents and the characteristic directions are functions of Lagrangian coordinates and time, which are completely determined once the flow field is specified. The characteristic directions that are associated with the spatial anisotropy of the problem, are prescribed in both Lagrangian and Eulerian frames. Coordinate transformation techniques are employed to relate the spatial distributions of the magnetic field, the induced current density, and the Lorentz force, which are usually followed in Eulerian frame, to those of the local Lyapunov exponents, which are naturally defined in Lagrangian coordinates.
Anisotropies in magnetic field evolution and local Lyapunov exponents
Tang, X. Z. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)] [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States); Boozer, A. H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)] [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)
The natural occurrence of small scale structures and the extreme anisotropy in the evolution of a magnetic field embedded in a conducting flow is interpreted in terms of the properties of the local Lyapunov exponents along the various local characteristic (un)stable directions for the Lagrangian flow trajectories. The local Lyapunov exponents and the characteristic directions are functions of Lagrangian coordinates and time, which are completely determined once the flow field is specified. The characteristic directions that are associated with the spatial anisotropy of the problem, are prescribed in both Lagrangian and Eulerian frames. Coordinate transformation techniques are employed to relate the spatial distributions of the magnetic field, the induced current density, and the Lorentz force, which are usually followed in Eulerian frame, to those of the local Lyapunov exponents, which are naturally defined in Lagrangian coordinates. (c) 2000 American Institute of Physics.
Spin Chain in Magnetic Field: Limitations of the Large-N Mean-Field Theory
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Wohlfeld, K.; Chen, Cheng-Chien; van Veenendaal, M.; Devereaux, T.P.
Motivated by the recent success in describing the spin and orbital spectrum of a spin-orbital chain using a large-N mean-field approximation [Phys. Rev. B 91, 165102 (2015)], we apply the same formalism to the case of a spin chain in the external magnetic field. It occurs that in this case, which corresponds to N=2 in the approximation, the large-N mean-field theory cannot qualitatively reproduce the spin excitation spectra at high magnetic fields, which polarize more than 50% of the spins in the magnetic ground state. This, rather counterintuitively, shows that the physics of a spin chain can under some circumstancesmore��be regarded as more complex than the physics of a spin-orbital chain.��less
Rayleigh-Taylor instabilities with sheared magnetic fields
Ruderman, M. S. [Solar Physics and Space Plasma Research Centre (SP2RC), University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Terradas, J.; Ballester, J. L. [Departament de F�sica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)
Magnetic Rayleigh-Taylor (MRT) instabilities may play a relevant role in many astrophysical problems. In this work the effect of magnetic shear on the growth rate of the MRT instability is investigated. The eigenmodes of an interface and a slab model under the presence of gravity are analytically calculated assuming that the orientation of the magnetic field changes in the equilibrium, i.e., there is magnetic shear. We solve the linearized magnetohydrodynamic equations in the incompressible regime. We find that the growth rate is bounded under the presence of magnetic shear. We have derived simple analytical expressions for the maximum growth rate, corresponding to the most unstable mode of the system. These expressions provide the explicit dependence of the growth rate on the various equilibrium parameters. For small angles the growth time is linearly proportional to the shear angle, and in this regime the single interface problem and the slab problem tend to the same result. On the contrary, in the limit of large angles and for the interface problem the growth time is essentially independent of the shear angle. In this regime we have also been able to calculate an approximate expression for the growth time for the slab configuration. Magnetic shear can have a strong effect on the growth rates of the instability. As an application of the results found in this paper we have indirectly determined the shear angle in solar prominence threads using their lifetimes and the estimation of the Alfv�n speed of the structure.
Radio frequency sheaths in an oblique magnetic field
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Myra, James R.; D'Ippolito, Daniel A.
The physics of radio-frequency (rf) sheaths near a conducting surface is studied for plasmas immersed in a magnetic field that makes an oblique angle ? with the surface. A set of one-dimensional equations is developed that describe the dynamics of the time-dependent magnetic presheath and non-neutral Debye sheath. The model employs Maxwell-Boltzmann electrons, and the magnetization and mobility of the ions is determined by the magnetic field strength, and wave frequency, respectively. The angle, ? assumed to be large enough to insure an electron-poor sheath, is otherwise arbitrary. Concentrating on the ion-cyclotron range of frequencies, the equations are solved numericallymore��to obtain the rectified (dc) voltage, the rf voltage across the sheath and the rf current flowing through the sheath. As an application of this model, the sheath voltage-current relation is used to obtain the rf sheath impedance, which in turn gives an rf sheath boundary condition for the electric field at the sheath-plasma interface that can be used in rf wave codes. In general the impedance has both resistive and capacitive contributions, and generalizes previous sheath boundary condition models. The resistive part contributes to parasitic power dissipation at the wall.��less
Height variation of the vector magnetic field in solar spicules
Suarez, D Orozco; Bueno, J Trujillo
Proving the magnetic configuration of solar spicules has hitherto been difficult due to the lack of spatial resolution and image stability during off-limb ground-based observations. We report spectropolarimetric observations of spicules taken in the He I 1083 nm spectral region with the Tenerife Infrared Polarimeter II at the German Vacuum Tower Telescope of the Observatorio del Teide (Tenerife; Canary Islands; Spain). The data provide the variation with geometrical height of the Stokes I, Q, U, and V profiles whose encoded information allows the determination of the magnetic field vector by means of the HAZEL inversion code. The inferred results show that the average magnetic field strength at the base of solar spicules is about 80 gauss and then it decreases rapidly with height to about 30 gauss at a height of 3000 km above the visible solar surface. Moreover, the magnetic field vector is close to vertical at the base of the chromosphere and has mid inclinations (about 50 degree) above 2 Mm height.
Cyclotron dynamics of interacting bosons in artificial magnetic fields
Xiaopeng Li; S. Das Sarma
We study theoretically quantum dynamics of interacting bosons in artificial magnetic fields as engineered in recent ultracold atomic experiments, where quantum cyclotron orbital motion has been observed. With exact numerical simulations and perturbative analyses, we find that interactions induce damping in the cyclotron motion. The damping time is found to be dependent on interaction and tunneling strengths monotonically, while its dependence on magnetic flux is non-monotonic. Sufficiently strong interactions would render bosons dynamically localized inhibiting the cyclotron motion. The damping predicted by us can be construed as an interaction-induced quantum decoherence of the cyclotron motion.
Tokamak with mechanical compression of toroidal magnetic field
Ohkawa, Tihiro (La Jolla, CA)
A tokamak apparatus includes a pressure vessel for defining a reservoir and confining liquid therein. A collapsible toroidal liner disposed within the pressure vessel defines a toroidal space within the liner. Liquid metal fills the reservoir outside said liner. A toroidal magnetic field is developed within the toroidal space about the major axis thereof. A toroidal plasma is developed within the toroidal space about the major axis thereof. Pressure is applied to the liquid metal to collapse the liner and reduce the volume of the toroidal space, thereby increasing the toroidal magnetic flux density therein.
Quantum Mechanics with a Momentum-Space Artificial Magnetic Field
Hannah M. Price; Tomoki Ozawa; Iacopo Carusotto
The Berry curvature is a geometrical property of an energy band which acts as a momentum space magnetic field in the effective Hamiltonian describing single-particle quantum dynamics. We show how this perspective may be exploited to study systems directly relevant to ultracold gases and photonics. Given the exchanged roles of momentum and position, we demonstrate that the global topology of momentum space is crucially important. We propose an experiment to study the Harper-Hofstadter Hamiltonian with a harmonic trap that will illustrate the advantages of this approach and that will also constitute the first realization of magnetism on a torus.
Faraday Rotation Observations of Magnetic Fields in galaxy Clusters
Tracy E. Clarke
The presence of magnetic fields in the intracluster medium in clusters of galaxies has been revealed through several different observational techniques. These fields may be dynamically important in clusters as they will provide additional pressure support to the intracluster medium as well as inhibit transport mechanisms such as thermal conduction. Here, we review the current observational state of Faraday rotation measure studies of the cluster fields. The fields are generally found to be a few to 10 microG in non-cooling core clusters and ordered on scales of 10-20 kpc. Studies of sources at large impact parameters show that the magnetic fields extend from cluster cores to radii of at least 500 kpc. In central regions of cooling core systems the field strengths are often somewhat higher (10-40 microG) and appear to be ordered on smaller scales of a few to 10 kpc. We also review some of the recent work on interpreting Faraday rotation measure observations through theory and numerical simulations. These techniques allow us to build up a much more detailed view of the strength and topology of the fields.
Chapman, Nicholas L.; Goldsmith, Paul F.; Pineda, Jorge L.; Li Di [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 301-429, Pasadena, CA 91109 (United States); Clemens, D. P. [Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Krco, Marko, E-mail: firstname.lastname@example.com [Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States)
We present maps of the plane-of-sky magnetic field within two regions of the Taurus molecular cloud: one in the dense core L1495/B213 filament and the other in a diffuse region to the west. The field is measured from the polarization of background starlight seen through the cloud. In total, we measured 287 high-quality near-infrared polarization vectors in these regions. In L1495/B213, the percent polarization increases with column density up to A{sub V} {approx} 9 mag, the limits of our data. The radiative torques model for grain alignment can explain this behavior, but models that invoke turbulence are inconsistent with the data. We also combine our data with published optical and near-infrared polarization measurements in Taurus. Using this large sample, we estimate the strength of the plane-of-sky component of the magnetic field in nine subregions. This estimation is done with two different techniques that use the observed dispersion in polarization angles. Our values range from 5 to 82 {mu}G and tend to be higher in denser regions. In all subregions, the critical index of the mass-to-magnetic flux ratio is sub-unity, implying that Taurus is magnetically supported on large scales ({approx}2 pc). Within the region observed, the B213 filament takes a sharp turn to the north and the direction of the magnetic field also takes a sharp turn, switching from being perpendicular to the filament to becoming parallel. This behavior can be understood if we are observing the rim of a bubble. We argue that it has resulted from a supernova remnant associated with a recently discovered nearby gamma-ray pulsar.
Use of High Magnetic Field to Control Microstructural Evolution in Metallic and Magnetic Materials
Ludtka, G.M.; Mackiewicz- Ludtka, G.; Wilgen, J.B.; Kisner, R.A.
The Amendment 1, referred to as Phase 2, to the original CRADA NFE-06-00414 added tasks 3 through 7 to the original statement of work that had two main tasks that were successfully accomplished in Phase 1 of this project. In this Phase 2 CRADA extension, extensive research and development activities were conducted using high magnetic field processing effects for the purpose of manipulating microstructure in the SAE 5160 steel to refine grain size isothermally and to develop nanocrystalline spacing pearlite during continuous cooling, and to enhance the formability/forgability of the non-ferrous precipitation hardening magnesium alloy AZ90 by applying a high magnetic field during deformation processing to investigate potential magnetoplasticity in this material. Significant experimental issues (especially non-isothermal conditions evolving upon insertion of an isothermal sample in the high magnetic field) were encountered in the isothermal phase transformation reversal experiments (Task 4) that later were determined to be due to various condensed matter physics phenomenon such as the magnetocaloric (MCE) effect that occurs in the vicinity of a materials Curie temperature. Similarly the experimental deformation rig had components for monitoring deformation/strain (Task 3) that were susceptible to the high magnetic field of the ORNL Thermomagnetic Processing facility 9-T superconducting magnet that caused electronic components to fail or record erroneous (very noisy) signals. Limited experiments on developing nanocrystalline spacing pearlite were not sufficient to elucidate the impact of high magnetic field processing on the final pearlite spacing since significant statistical evaluation of many pearlite colonies would need to be done to be conclusive. Since extensive effort was devoted to resolving issues for Tasks 3 and 7, only results for these focused activities are included in this final CRADA report along with those for Task 7 (described in the Objectives Section of this report).
Formation of Moving Magnetic Features and Penumbral Magnetic Fields with Hinode/SOT
Masahito Kubo; Kiyoshi Ichimoto; Toshifumi Shimizu; Saku Tsuneta; Yoshinori Suematsu; Yukio Katsukawa; Shin'ichi Nagata; Theodore D Tarbell; Richard A Shine; Alan M Title; Zoe A Frank; Bruce W Lites; David Elmore
Vector magnetic fields of moving magnetic features (MMFs) are well observed with the Solar Optical Telescope (SOT) aboard the Hinode satellite. We focus on the evolution of three MMFs with the SOT in this study. We found that an MMF having relatively vertical fields with polarity same as the sunspot is detached from the penumbra around the granules appeared in the outer penumbra. This suggests that granular motions in the outer penumbra are responsible for the disintegration of the sunspot. Two MMFs with polarity opposite to the sunspot are located around the outer edge of horizontal fields extending from the penumbra. This is an evidence that the MMFs with polarity opposite to the sunspot are prolongation of penumbral horizontal fields. Radshifts larger than sonic velocity in the photosphere are detected for some of the MMFs with polarity opposite to the sunspot.
New limits on extragalactic magnetic fields from rotation measures
Pshirkov, Maxim S; Urban, Federico R
We take advantage of the wealth of rotation measures data contained in the NVSS catalogue to derive new, statistically robust, upper limits on the strength of extragalactic magnetic fields. We simulate the extragalactic contribution to the rotation measures for a given field strength and correlation length, by assuming that the electron density follows the distribution of Lyman-$\\alpha$ clouds. Based on the observation that rotation measures from low-luminosity distant radio sources do not exhibit any trend with redshift, while the extragalactic contribution instead grows with distance, we constrain fields with Mpc coherence length to be below 1.2 nG at the $2\\sigma$ level, and fields coherent across the entire observable Universe below 0.5 nG. These limits do not depend on the particular origin of these cosmological fields.
Magnetic Reconnection in the MST Reversed Field Pinch
Crocker, N.E.
Magnetic field line reconnection is a process whereby magnetic field lines which are otherwise topologically preserved by, and frozen into, a plasma can break and reconnect to form field lines with different topologies. It plays a significant role in a wide variety of plasmas, including stellar, space and laboratory plasmas. The focus of this dissertation is the underlying dynamics of reconnection in one particular kind of laboratory plasma: the Reversed Field Pinch (RFP). Specifically, this dissertation reports measurements, made using a pair of insertable diagnostics in conjunction with arrays of magnetic sensing coils positioned near the plasma surface, of the spatial structure of the magnetic and parallel current density fluctuations associated with reconnection in the edge of MST. At least 4 significant results are obtained form such measurements. First we observe direct evidence of reconnection which takes the form of tearing modes in an RFP. Specifically we measure a (radial) magnetic field fluctuation that causes reconnection in the so-called reversal surface, or q = 0 surface, in the edge of MST. Notably this evidence of reconnection at the reversal surface is the first of its kind in an RFP. Second, we measure the radial width of the associated current sheet, or fluctuation in the component of the current density parallel to the equilibrium magnetic field. Such current sheets are a characteristic feature of the reconnection process but their radial widths are sensitive to the specific effects that allow reconnection to occur sometimes call non-ideal effects because reconnection is forbidden by ideal MHD. We compare the observed width to those expected from models of reconnection that incorporate different non-ideal effects in Ohm's law. In particular we see that the observed width is significantly larger than those expected form resistivity in the context of linearly unstable tearing modes and electron inertia. It is a factor of a few larger than the width expected form the electron pressure gradient effect. It is significantly smaller than the width expected from the ion inertia, but this width is not expected to be relevant to a strongly magnetized plasma such as an RFP. Notably it is comparable to the width of the magnetic island produced by the associated tearing mode. This is consistent with expectation for saturated or fully developed resistive tearing modes such as MST is believed to exhibit. It is also consistent with the broadening of a smaller width current sheet through current transport due to parallel streaming of charge carriers (along the field lines of the associated island). Third we obtain estimates of the radial charge transport or radial current density due to streaming charge of carriers along magnetic field lines that results from reconnection in the edge of MST. We find that in contradiction with the theoretical expectation for isolated tearing modes it is non-vanishing and in fact large enough to imply both the existence of another charge transport mechanism to maintain charge neutrality and a significant difference in the radial ion and electron particle fluxes due to parallel streaming of particles. Fourth we interpret the flux surface average of j and b as a J x B force density on the plasma. We observe in agreement with theory and observation for interacting tearing modes in an RFP that the radial structure of the force density during sawtooth crashes is such as to flatten the equilibrium radial gradient in toroidal velocity. We observe also that it is sufficiently large as to imply the existence of other force densities on the plasma.
Enhanced density and magnetic fields in interstellar OH masers
Vincent L. Fish; Mark J. Reid; Karl M. Menten; Thushara Pillai
Aims: We have observed the 6030 and 6035 MHz transitions of OH in high-mass star-forming regions to obtain magnetic field estimates in both maser emission and absorption. Methods: Observations were taken with the Effelsberg 100 m telescope. Results: Our observations are consistent with previous results, although we do detect a new 6030 MHz maser feature near -70 km/s in the vicinity of W3(OH). In absorption we obtain a possible estimate of -1.1 +/- 0.3 mG for the average line-of-sight component of the magnetic field in the absorbing OH gas in K3-50 and submilligauss upper limits for the line-of-sight field strength in DR 21 and W3. Conclusions: These results indicate that the magnetic field strength in the vicinity of OH masers is higher than that of the surrounding, non-masing material, which in turn suggests that the density of masing OH regions is higher than that of their surroundings.
Structure and Dynamics of the Sun's Open Magnetic Field
S. K. Antiochos; C. R. DeVore; J. T. Karpen; Z. Mikic
The solar magnetic field is the primary agent that drives solar activity and couples the Sun to the Heliosphere. Although the details of this coupling depend on the quantitative properties of the field, many important aspects of the corona - solar wind connection can be understood by considering only the general topological properties of those regions on the Sun where the field extends from the photosphere out to interplanetary space, the so-called open field regions that are usually observed as coronal holes. From the simple assumptions that underlie the standard quasi-steady corona-wind theoretical models, and that are likely to hold for the Sun, as well, we derive two conjectures on the possible structure and dynamics of coronal holes: (1) Coronal holes are unique in that every unipolar region on the photosphere can contain at most one coronal hole. (2) Coronal holes of nested polarity regions must themselves be nested. Magnetic reconnection plays the central role in enforcing these constraints on the field topology. From these conjectures we derive additional properties for the topology of open field regions, and propose several observational predictions for both the slowly varying and transient corona/solar wind.
Magnetic Field Created by Tile Permanent R. Ravaud, G. Lemarquand, V. Lemarquand
Boyer, Edmond
, the most common shape for a permanent magnet in electrical engineering11 is certainly the tile, which can1 Magnetic Field Created by Tile Permanent Magnets R. Ravaud, G. Lemarquand, V. Lemarquand Abstract1 This paper presents the analytical calculation of the three components of the magnetic field
Transport of Magnetic Fields in Convective, Accreting Supernova Cores
Christopher Thompson; Norman Murray
We consider the amplification and transport of a magnetic field in the collapsed core of a massive star, including both the region between the neutrinosphere and the shock, and the central, opaque core. An analytical argument explains why rapid convective overturns persist within a newly formed neutron star for roughly 10 seconds ($> 10^3$ overturns), consistent with recent numerical models. A dynamical balance between turbulent and magnetic stresses within this convective layer corresponds to flux densities in excess of $10^{15}$G. Material accreting onto the core is heated by neutrinos and also becomes strongly convective. We compare the expected magnetic stresses in this convective `gain layer' with those deep inside the neutron core. Buoyant motions of magnetized fluid are greatly aided by the intense neutrino flux. We calculate the transport rate through a medium containing free neutrons protons, and electrons, in the limiting cases of degenerate or non-degenerate nucleons. Fields stronger than $\\sim 10^{13}$ G are able to rise through the outer degenerate layers of the neutron core during the last stages of Kelvin-Helmholtz cooling (up to 10 seconds post-collapse), even though these layers have become stable to convection. We also find the equilibrium shape of a thin magnetic flux rope in the dense hydrostatic atmosphere of the neutron star, along with the critical separation of the footpoints above which the rope undergoes unlimited expansion against gravity. The implications of these results for pulsar magnetism are summarized, and applied to the case of late fallback over the first 1,000-10,000 s of the life of a neutron star
Charge-Transfer Induced Magnetic Field Effects of Nano-Carbon Heterojunctions
Qin, Wei; Gong, Maogang; Shastry, Tejas; Hersam, Mark C.; Ren, Shenqiang
Room temperature magnetic field effects have not been definitively observed in either single-walled carbon nanotubes (SWCNTs) or C60 under a small magnetic field due to their weak hyperfine interaction and slight difference of g-factor between...
Periodicity of the solar full-disk magnetic fields
Xiang, N. B.; Qu, Z. N.; Zhai, Q. [National Astronomical Observatories/Yunnan Observatory, CAS, Kunming 650011 (China)
A full-disk solar magnetogram has been measured each day since 1970 January 19, and the daily Magnetic Plage Strength Index (MPSI) and the daily Mount Wilson Sunspot Index (MWSI) were calculated for each magnetogram at the Mount Wilson Observatory. The MPSI and MWSI are used to investigate the periodicity of the solar full-disk magnetic activity through autocorrelation analyses. Just two periods, the solar cycle and the rotation cycle, are determined in both the MPSI (the solar full-disk weak magnetic field activity) and MWSI (the solar full-disk strong magnetic field activity) with no annual signal found. The solar cycle for MPSI (10.83 yr) is found to be obviously longer than that for MWSI (9.77 yr). The rotation cycle is determined to be 26.8 � 0.63 sidereal days for MPSI and 27.4 � 2.4 sidereal days for MWSI. The rotation cycle length for MPSI is found to fluctuate around 27 days within a very small amplitude, but for MWSI it obviously temporally varies with a rather large amplitude. The rotation cycle for MWSI seems longer near solar minimum than at solar maximum. Cross-correlation analyses of daily MPSI and MWSI are carried out, and it is inferred that the MPSI components partly come from relatively early MWSI measurements.
Double Barriers and Magnetic Field in Bilayer Graphene
Ilham Redouani; Ahmed Jellal; Hocine Bahlouli
We study the transmission probability in an AB-stacked bilayer graphene of Dirac fermions scattered by a double barrier structure in the presence of a magnetic field. We take into account the full four bands of the energy spectrum and use the boundary conditions to determine the transmission probability. Our numerical results show that for energies higher than the interlayer coupling, four ways for transmission probabilities are possible while for energies less than the height of the barrier, Dirac fermions exhibits transmission resonances and only one transmission channel is available. We show that, for AB-stacked bilayer graphene, there is no Klein tunneling at normal incident. We find that the transmission displays sharp peaks inside the transmission gap around the Dirac point within the barrier regions while they are absent around the Dirac point in the well region. The effect of the magnetic field, interlayer electrostatic potential and various barrier geometry parameters on the transmission probabilities are also discussed.
Cryogenic properties of dispersion strengthened copper for high magnetic fields
Toplosky, V. J.; Han, K.; Walsh, R. P. [National High Magnetic Field Laboratory, Tallahassee, FL 32310 (United States); Swenson, C. A. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)
Cold deformed copper matrix composite conductors, developed for use in the 100 tesla multi-shot pulsed magnet at the National High Magnetic Field Laboratory (NHMFL), have been characterized. The conductors are alumina strengthened copper which is fabricated by cold drawing that introduces high dislocation densities and high internal stresses. Both alumina particles and high density of dislocations provide us with high tensile strength and fatigue endurance. The conductors also have high electrical conductivities because alumina has limited solubility in Cu and dislocations have little scattering effect on conduction electrons. Such a combination of high strength and high conductivity makes it an excellent candidate over other resistive magnet materials. Thus, characterization is carried out by tensile testing and fully reversible fatigue testing. In tensile tests, the material exceeds the design criteria parameters. In the fatigue tests, both the load and displacement were measured and used to control the amplitude of the tests to simulate the various loading conditions in the pulsed magnet which is operated at 77 K in a non-destructive mode. In order to properly simulate the pulsed magnet operation, strain-controlled tests were more suitable than load controlled tests. For the dispersion strengthened coppers, the strengthening mechanism of the aluminum oxide provided better tensile and fatigue properties over convention copper.
Circuitry, systems and methods for detecting magnetic fields
Kotter, Dale K. (Shelley, ID) [Shelley, ID; Spencer, David F. (Idaho Falls, ID) [Idaho Falls, ID; Roybal, Lyle G. (Idaho Falls, ID) [Idaho Falls, ID; Rohrbaugh, David T. (Idaho Falls, ID) [Idaho Falls, ID
Circuitry for detecting magnetic fields includes a first magnetoresistive sensor and a second magnetoresistive sensor configured to form a gradiometer. The circuitry includes a digital signal processor and a first feedback loop coupled between the first magnetoresistive sensor and the digital signal processor. A second feedback loop which is discrete from the first feedback loop is coupled between the second magnetoresistive sensor and the digital signal processor.
A. M. Egorov; G. G. Likhachev; A. I. Studenikin
A review of the neutrino conversion and oscillations among the two neutrino species (active and sterile) induced by strong twisting magnetic field is presented and implications to neutrinos in neutron star, supernova, the Sun and interstellar galactic media are discussed. The ``cross-boundary effect" (CBE) (i.e., a possible conversion of one half of neutrinos of the bunch from active into sterile specie) at the surface of neutron star is also studied for a realistic neutron star structure.
Adiabatic expansion and magnetic fields in AGN jets
A. B. Pushkarev; Y. Y. Kovalev; A. P. Lobanov
Results of high-resolution simultaneous multi-frequency 8.1-15.4 GHz VLBA polarimetric observations of relativistic jets in active galactic nuclei (the MOJAVE-2 project) are analyzed. We compare characteristics of VLBI features with jet model predictions and test if adiabatic expansion is a dominating mechanism for the evolution of relativistic shocks in parsec-scale AGN jets. We also discuss magnetic field configuration, both predicted by the model and deduced from electric vector position angle measurements.
Conference Summary: The Cosmic Agitator - Magnetic Fields in the Galaxy
T. H. Troland; C. Heiles; A. P. Sarma; G. J. Ferland; R. M. Crutcher; C. L. Brogan
We present a summary of the conference "The Cosmic Agitator: Magnetic Fields in the Galaxy" held in Lexington KY in 2008 Mar 26-29. The presentation draws primarily from material in the slides prepared for the Conference Summary by one of us (Carl Heiles). Interested readers may navigate to the conference web site given in the paper to view the posted presentations in detail.
Ballistic dynamics of Dirac particles in electro-magnetic fields
Josef Mehringer; Edgardo Stockmeyer
Investigating properties of two-dimensional Dirac operators coupled to an electric and a magnetic field (perpendicular to the plane) requires in general unbounded (vector-) potentials. If the system has a certain symmetry, the fields can be described by one-dimensional potentials $V$ and $A$. Assuming that $|A|<|V|$ outside some arbitrary large ball, we show that absolutely continuous states of the effective Dirac operators spread ballistically. These results are based on well-known methods in spectral dynamics together with certain new Hilbert-Schmidt bounds. We use Lorentz boosts to derive these new estimates.
Planck 2015 results. XIX. Constraints on primordial magnetic fields
Ade, P A R; Arnaud, M; Arroja, F; Ashdown, M; Aumont, J; Baccigalupi, C; Ballardini, M; Banday, A J; Barreiro, R B; Bartolo, N; Battaner, E; Benabed, K; Beno�t, A; Benoit-L�vy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Bucher, M; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Catalano, A; Chamballu, A; Chiang, H C; Chluba, J; Christensen, P R; Church, S; Clements, D L; Colombi, S; Colombo, L P L; Combet, C; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; D�sert, F -X; Diego, J M; Dolag, K; Dole, H; Donzelli, S; Dor�, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; En�lin, T A; Eriksen, H K; Fergusson, J; Finelli, F; Florido, E; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Giard, M; Giraud-H�raud, Y; Gjerl�w, E; Gonz�lez-Nuevo, J; G�rski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Hansen, F K; Hanson, D; Harrison, D L; Helou, G; Henrot-Versill�, S; Hern�ndez-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Keih�nen, E; Keskitalo, R; Kim, J; Kisner, T S; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; L�hteenm�ki, A; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leahy, J P; Leonardi, R; Lesgourgues, J; Levrier, F; Liguori, M; Lilje, P B; Linden-V�rnle, M; L�pez-Caniego, M; Lubin, P M; Mac�as-P�rez, J F; Maggio, G; Maino, D; Mandolesi, N; Mangilli, A; Martin, P G; Mart�nez-Gonz�lez, E; Masi, S; Matarrese, S; Mazzotta, P; McGehee, P; Meinhold, P R; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Mitra, S; Miville-Desch�nes, M -A; Molinari, D; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Moss, A; Munshi, D; Murphy, J A; Naselsky, P; Nati, F; Natoli, P; Netterfield, C B; N�rgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Oppermann, N; Oxborrow, C A; Paci, F; Pagano, L; Pajot, F; Paoletti, D; Pasian, F; Patanchon, G; Perdereau, O; Perotto, L; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Popa, L; Pratt, G W; Pr�zeau, G; Prunet, S; Puget, J -L; Rachen, J P; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Rosset, C; Rossetti, M; Roudier, G; Rubi�o-Mart�n, J A; Ruiz-Granados, B; Rusholme, B; Sandri, M; Santos, D; Savelainen, M; Savini, G; Scott, D; Seiffert, M D; Shellard, E P S; Shiraishi, M; Spencer, L D; Stolyarov, V; Stompor, R; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Umana, G; Valenziano, L; Valiviita, J; Van Tent, B; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; Yvon, D; Zacchei, A; Zonca, A
We predict and investigate four types of imprint of a stochastic background of primordial magnetic fields (PMFs) on the cosmic microwave background (CMB) anisotropies: the impact of PMFs on the CMB spectra; the effect on CMB polarization induced by Faraday rotation; magnetically-induced non-Gaussianities; and the magnetically-induced breaking of statistical isotropy. Overall, Planck data constrain the amplitude of PMFs to less than a few nanogauss. In particular, individual limits coming from the analysis of the CMB angular power spectra, using the Planck likelihood, are $B_{1\\,\\mathrm{Mpc}}< 4.4$ nG (where $B_{1\\,\\mathrm{Mpc}}$ is the comoving field amplitude at a scale of 1 Mpc) at 95% confidence level, assuming zero helicity, and $B_{1\\,\\mathrm{Mpc}}< 5.6$ nG when we consider a maximally helical field. For nearly scale-invariant PMFs we obtain $B_{1\\,\\mathrm{Mpc}}<2.1$ nG and $B_{1\\,\\mathrm{Mpc}}<0.7$ nG if the impact of PMFs on the ionization history of the Universe is included in the analysis...
Magnetic field gradients in solar wind plasma and geophysics periods
A. Bershadskii
Using recent data obtained by Advanced Composition Explorer (ACE) the pumping scale of the magnetic field gradients of the solar wind plasma has been calculated. This pumping scale is found to be equal to 24h $\\pm$ 2h. The ACE spacecraft orbits at the L1 libration point which is a point of Earth-Sun gravitational equilibrium about 1.5 million km from Earth. Since the Earth's magnetosphere extends into the vacuum of space from approximately 80 to 60,000 kilometers on the side toward the Sun the pumping scale cannot be a consequence of the 24h-period of the Earth's rotation. Vise versa, a speculation is suggested that for the very long time of the coexistence of Earth and of the solar wind the weak interaction between the solar wind and Earth could lead to stochastic synchronization between the Earth's rotation and the pumping scale of the solar wind magnetic field gradients. This synchronization could transform an original period of the Earth's rotation to the period close to the pumping scale of the solar wind magnetic field gradients.
How are Forbush decreases related with interplanetary magnetic field enhancements ?
Arunbabu, K P; Dugad, S R; Gupta, S K; Hayashi, Y; Kawakami, S; Mohanty, P K; Oshima, A; Subramanian, P
Aims. Forbush decrease (FD) is a transient decrease followed by a gradual recovery in the observed galactic cosmic ray intensity. We seek to understand the relationship between the FDs and near-Earth interplanetary magnetic field (IMF) enhancements associated with solar coronal mass ejections (CMEs). Methods. We use muon data at cutoff rigidities ranging from 14 to 24 GV from the GRAPES-3 tracking muon telescope to identify FD events. We select those FD events that have a reasonably clean profile, and magnitude > 0.25%. We use IMF data from ACE/WIND spacecrafts. We look for correlations between the FD profile and that of the one hour averaged IMF. We ask if the diffusion of high energy protons into the large scale magnetic field is the cause of the lag observed between the FD and the IMF. Results. The enhancement of the IMF associated with FDs occurs mainly in the shock-sheath region, and the turbulence level in the magnetic field is also enhanced in this region. The observed FD profiles look remarkably simil...
Electric Fields and Chiral Magnetic Effect in Cu + Au Collisions
Wei-Tian Deng; Xu-Guang Huang
The non-central Cu + Au collisions can create strong out-of-plane magnetic fields and in-plane electric fields. By using the HIJING model, we study the general properties of the electromagnetic fields in Cu + Au collisions at 200 GeV and their impacts on the charge-dependent two-particle correlator $\\gamma_{q_1q_2}=$ (see main text for definition) which was used for the detection of the chiral magnetic effect (CME). Compared with Au + Au collisions, we find that the in-plane electric fields in Cu + Au collisions can strongly suppress the two-particle correlator or even reverse its sign if the lifetime of the electric fields is long. Combining with the expectation that if $\\gamma_{q_1q_2}$ is induced by elliptic-flow driven effects we would not see such strong suppression or reversion, our results suggest to use Cu + Au collisions to test CME and understand the mechanisms that underlie $\\gamma_{q_1q_2}$.
The influence of a magnetic field on turbulent heat transfer of a high Prandtl number fluid
Nakaharai, H. [Department of Advanced Energy Engineering Science, Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, Kasuga-kouen 6-1, Kasuga, Fukuoka 816-8580 (Japan); Takeuchi, J.; Morley, N.B.; Abdou, M.A. [Mechanical and Aerospace Engineering Department, University of California, Los Angeles, CA 90095-1597 (United States); Yokomine, T. [Faculty of Energy Engineering Science, Kyushu University, Kasuga-kouen 6-1, Kasuga, Fukuoka 816-8580 (Japan); Kunugi, T. [Department of Nuclear Engineering, Kyoto University, Yoshida, Sakyo, Kyoto 606-8501 (Japan); Satake, S. [Department of Applied Electronics, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510 (Japan)
The influence of a transverse magnetic field on the local and average heat transfer of an electrically conducting, turbulent fluid flow with high Prandtl number was studied experimentally. The mechanism of heat transfer modification due to magnetic field is considered with aid of available numerical simulation data for turbulent flow field. The influence of the transverse magnetic field on the heat transfer was to suppress the temperature fluctuation and to steepen the mean temperature gradient in near-wall region in the direction parallel to the magnetic field. The mean temperature gradient is not influenced compared to the temperature fluctuation in the direction vertical to the magnetic field. (author)
Strongest non-destructive magnetic field: world record set at 100-tesla level
- 1 - Strongest non-destructive magnetic field: world record set at 100-tesla level March 22, 2012), the scientists achieved a whopping 100.75 tesla--a magnetic field nearly 100 times more powerful than a junkyard and insulators. The 100-tesla level is roughly equivalent to 2 million times Earth's magnetic field. #12;- 2
Compressing magnetic fields with high-energy lasersa... J. P. Knauer,1,b
Compressing magnetic fields with high-energy lasersa... J. P. Knauer,1,b O. V. Gotchev,1,2,3 P. Y, Rochester, New York 14623, USA 3 Department of Mechanical Engineering, University of Rochester, 250 East-driven magnetic-field compression producing a magnetic field of tens of megaGauss is reported for the first time
Temperature compensated and self-calibrated current sensor using reference magnetic field
Yakymyshyn, Christopher Paul (Seminole, FL); Brubaker, Michael Allen (Loveland, CO); Yakymyshyn, Pamela Jane (Seminole, FL)
A method is described to provide temperature compensation and self-calibration of a current sensor based on a plurality of magnetic field sensors positioned around a current carrying conductor. A reference magnetic field generated within the current sensor housing is detected by the magnetic field sensors and is used to correct variations in the output signal due to temperature variations and aging.
Spectral Mapping of Protein Torsion Angles National High Magnetic Field Laboratory
Weston, Ken
Spectral Mapping of Protein Torsion Angles National High Magnetic Field Laboratory NMR Spectroscopy spectra. #12;Spectral Mapping of Protein Torsion Angles National High Magnetic Field Laboratory NMR, in recording signals that are dependent on the orientation of the atoms with respect to the magnetic field, we
Limits on guiding center and gyrokinetic plasma models in 3D magnetic fields
D field: magnetic field torsion and coordinate system twisting � GC higher order validity and global, as seen when moving in that direction. � Magnetic field torsion ^b � � ^b is the twisting of the field.) � Torsion also introduces twisting of the local field-tied orthogonal coordinate sys- tem, R = (^e1)�^e2
Linear metric and temperature fluctuations of a charged plasma in a primordial magnetic field
Haba, Z
We discuss tensor metric perturbations in a magnetic field around the homogeneous Juttner equilibrium of massless particles in an expanding universe. We solve the Liouville equation and derive the energy-momentum tensor up to linear terms in the metric and in the magnetic field.The term linear in the magnetic field is different from zero if the total charge of the primordial plasma is non-zero. We obtain an analytic formula for temperature fluctuations treating the tensor metric perturbations and the magnetic field as independent random variables. Assuming a cutoff on large momenta of the magnetic spectral function we show that the presence of the magnetic field can discriminate only low multipoles in the multipole expansion of temperature fluctuations. In such a case the term linear in the magnetic field can be more important than the quadratic one (corresponding to the fluctuations of the pure magnetic field).
High-precision description and new properties of a spin-1 particle in a magnetic field
Alexander J. Silenko
The exact Foldy-Wouthuysen Hamiltonian is derived for a pointlike spin-1 particle with a normal magnetic moment in a nonuniform magnetic field. For a uniform magnetic field, it is exactly separated into terms linear and quadratic in spin. New unexpected properties of a particle with an anomalous magnetic moment are found. Spin projections of a particle moving in a uniform magnetic field are not integer and the tensor polarization is asymmetric in the plane orthogonal to the field. Previously described spin-tensor effects caused by the tensor magnetic polarizability exist not only for nuclei but also for pointlike particles.
Stellar coronal magnetic fields and star-planet interaction
Lanza, A F
Evidence of magnetic interaction between late-type stars and close-in giant planets is provided by the observations of stellar hot spots rotating synchronously with the planets and showing an enhancement of chromospheric and X-ray fluxes. We investigate star-planet interaction in the framework of a magnetic field model of a stellar corona, considering the interaction between the coronal field and that of a planetary magnetosphere moving through the corona. The energy budget of the star-planet interaction is discussed assuming that the planet may trigger a release of the energy of the coronal field by decreasing its relative helicity. The observed intermittent character of the star-planet interaction is explained by a topological change of the stellar coronal field, induced by a variation of its relative helicity. The model predicts the formation of many prominence-like structures in the case of highly active stars owing to the accumulation of matter evaporated from the planet inside an azimuthal flux rope in ...
Anisotropic nanostructured magnets by magnetic-field-assisted processing Chuan-bing Rong, Van Vuong Nguyen, and J. Ping Liua
Liu, J. Ping
. In this paper, we report our recent work in preparing anisotropic bonded magnets consisting of SmCo5 nanocrystalline particles. The work involved synthesis of nanocrystalline hard magnetic SmCo5 particles by ball of the c-axis of the SmCo5 grains upon the magnetic-field-assisted ball milling, while the grain size
Effect of primordial magnetic fields on the ionization history
Chluba, Jens; Finelli, Fabio; Rubino-Martin, Jose-Alberto
Primordial magnetic fields (PMF) damp at scales smaller than the photon diffusion and free-streaming scale. This leads to heating of ordinary matter (electrons and baryons), which affects both the thermal and ionization history of our Universe. Here, we study the effect of heating due to ambipolar diffusion and decaying magnetic turbulence. We find that changes to the ionization history computed with recfast are significantly overestimated when compared with CosmoRec. The main physical reason for the difference is that the photoionization coefficient has to be evaluated using the radiation temperature rather than the matter temperature. A good agreement with CosmoRec is found after changing this aspect. Using Planck 2013 data and considering only the effect of PMF-induced heating, we find an upper limit on the r.m.s. magnetic field amplitude of B0 < 1.1 nG (95% c.l.) for a stochastic background of PMF with a nearly scale-invariant power spectrum. We also discuss uncertainties related to the approximations ...
Electromagnetic waves reflection, transmission and absorption by graphene - magnetic semiconductor - graphene sandwich-structure in magnetic field: Faraday geometry
Kuzmin, Dmitry A; Shavrov, Vladimir G
Electrodynamic properties of the graphene - magnetic semiconductor - graphene sandwich-structure have been investigated theoretically with taking into account the dissipation processes. Influence of graphene layers on electromagnetic waves propagation in graphene - semi-infinte magnetic semiconductor and graphene - magnetic semiconductor - graphene sandwich-structure has been analyzed. Frequency and field dependences of the reflectance, transmittance and absorbtance of electromagnetic waves by such structure have been calculated. The size effects associated with the thickness of the structure have been analyzed. The possibility of efficient control of electrodynamic properties of graphene - magnetic semiconductor - graphene sandwich structure by an external magnetic field has been shown.
Effects of chiral imbalance and magnetic field on pion superfluidity and color superconductivity
Cao, Gaoqing
The effects of chiral imbalance and external magnetic field on pion superfluidity and color superconductivity are investigated in extended Nambu--Jona-Lasinio models. We take Schwinger approach to treat the interaction between charged pion condensate and magnetic field at finite isospin density and include simultaneously the chiral imbalance and magnetic field at finite baryon density. For the superfluidity, the chiral imbalance and magnetic field lead to catalysis and inverse catalysis effects, respectively. For the superconductivity, the chiral imbalance enhances the critical baryon density, and the magnetic field results in a de Haas--van Alphan oscillation on the phase transition line.
The role of renewable energy in climate stabilization: results from the EMF27
Paris-Sud XI, Universit� de
The role of renewable energy in climate stabilization: results from the EMF27 scenarios Gunnar the role of renewable energy in climate change mitigation. Renewables currently supply approximately 18, renewables are the most important long-term mitigation option for power supply. Wind energy is competitive
Strong magnetic fields and inhomogeneity in the solar corona
White, S.M.; Kundu, M.R.; Gopalswamy, N. (Maryland Univ., College Park (USA))
It is shown that fields of 1800 G can exist in the corona based on observations of gyroresonance emission at 15 GHz at coronal temperatures. The strong fields occur in a small source radiating in the extraordinary (x) mode over the penumbra of a large symmetric sunspot. The optically-thin ordinary mode emission from the region shows a nearby peak at only 36,000 K which may be due to a sunspot plume, and a hole over the umbra consistent with the expected low-density material there. The x-mode source is highly asymmetric, despite the apparent symmetry of the sunspot, and its appearance and location imply that the strongest magnetic fields in the corona are localized in a compact flux tube. 21 refs.
Collective Modes of Chiral Kinetic Theory in Magnetic Field
Mikhail Stephanov; Ho-Ung Yee; Yi Yin
We study collective excitations in systems described by chiral kinetic theory in external magnetic field. We consider high-temperature weak-coupling plasma, as well as high-density Landau Fermi liquid with interaction not restricted to be weak. We show that chiral magnetic wave (CMW) emerges in hydrodynamic regime (at frequencies smaller than collision relaxation rate) and the CMW velocity is determined by thermodynamic properties only. We find that in a plasma of opposite chiralities, at frequencies smaller than the chirality-flipping rate, the CMW excitation turns into a vector-like diffusion mode. In the interacting Fermi liquid, the CMW turns into the Landau zero sound mode in the high-frequency collisionless regime.
Collective Modes of Chiral Kinetic Theory in Magnetic Field
Stephanov, Mikhail; Yin, Yi
We study collective excitations in systems described by chiral kinetic theory in external magnetic field. We consider high-temperature weak-coupling plasma, as well as high-density Landau Fermi liquid with interaction not restricted to be weak. We show that chiral magnetic wave (CMW) emerges in hydrodynamic regime (at frequencies smaller than collision relaxation rate) and the CMW velocity is determined by thermodynamic properties only. We find that in a plasma of opposite chiralities, at frequencies smaller than the chirality-flipping rate, the CMW excitation turns into a vector-like diffusion mode. In the interacting Fermi liquid, the CMW turns into the Landau zero sound mode in the high-frequency collisionless regime.
Magnetic-field dependent trap loss of ultracold metastable helium
J. S. Borbely; R. van Rooij; S. Knoop; W. Vassen
We have experimentally studied the magnetic-field dependence of the decay of a Bose-Einstein condensate of metastable 4He atoms confined in an optical dipole trap, for atoms in the m=+1 and m=-1 magnetic substates, and up to 450 G. Our measurements confirm long-standing calculations of the two-body loss rate coefficient that show an increase above 50 G. We demonstrate that for m=-1 atoms, decay is due to three-body recombination only, with a three-body loss rate coefficient of 6.5(0.4)(0.6)10^(-27)cm^6s^(-1), which is interesting in the context of universal few-body theory. We have also searched for a recently-predicted d-wave Feshbach resonance, but did not observe it.
Thermal and high magnetic field treatment of materials and associated apparatus
Kisner, Roger A.; Wilgen, John B.; Ludtka, Gerard M.; Jaramillo, Roger A.; Mackiewicz-Ludtka, Gail
An apparatus and method for altering characteristics, such as can include structural, magnetic, electrical, optical or acoustical characteristics, of an electrically-conductive workpiece utilizes a magnetic field within which the workpiece is positionable and schemes for thermally treating the workpiece by heating or cooling techniques in conjunction with the generated magnetic field so that the characteristics of the workpiece are effected by both the generated magnetic field and the thermal treatment of the workpiece.
Thermal and high magnetic field treatment of materials and associated apparatus
Kisner, Roger A.; Wilgen, John B.; Ludtka, Gerard M.; Jaramillo, Roger A.; Mackiewicz-Ludtka, Gail
An apparatus and method for altering characteristics, such as can include structural, magnetic, electrical, optical or acoustical characteristics, of an electrically-conductive workpiece utilizes a magnetic field within which the workpiece is positionable and schemes for thermally treating the workpiece by heating or cooling techniques in conjunction with the generated magnetic field so that the characteristics of the workpiece are effected by both the generated magnetic field and the thermal treatment of the workpiece.
Low pressure arc discharge lamp apparatus with magnetic field generating means
Grossman, M.W.; George, W.A.; Maya, J.
A low-pressure arc discharge apparatus having a magnetic field generating means for increasing the output of a discharge lamp is disclosed. The magnetic field generating means, which in one embodiment includes a plurality of permanent magnets, is disposed along the lamp for applying a constant transverse magnetic field over at least a portion of the positive discharge column produced in the arc discharge lamp operating at an ambient temperature greater than about 25 C. 3 figs.
Weak magnetic field effects on chiral critical temperature in a nonlocal Nambu--Jona-Lasinio model
M. Loewe; F. Marquez; C. Villavicencio; R. Zamora
In this article we study the nonlocal Nambu--Jona-Lasinio model with a Gaussian regulator in the chiral limit. Finite temperature effects and the presence of a homogeneous magnetic field are considered. The magnetic evolution of the critical temperature for chiral symmetry restoration is then obtained. Here we restrict ourselves to the case of low magnetic field values, being this a complementary discussion to the exisiting analysis in nonlocal models in the strong magnetic field regime.
BTA Magnet Field Map Archive and MAD Model
This note publishes some and information that has resided in private files. The attached tables were provided by Joseph Skelly from his archives. They show magnetic field measurements versus excitation current for the Booster to AGS transfer line quadrupoles and dipoles based on field measurements [we believe] were done by the Magnet Division. Also given are Ed Blesser's fifth order fits of field versus current. The results are given in 'Tesla' or T-M/M. These tables are attached to provide an archive of this data. The MAD model of the BTA line does have the same values as shown in the attached fits so the transfer was correct. MAD uses as its 'gradient' for quads Tesla per meter normalized to rigidity [B-rho]. The model of the BTA line in use uses the T-M/M given in the tables divided by the length to give T M which is then normalized by Brho. Thus, the input to the model appears to be correct. The original model is also attached as part of a memo by Skelly describing it.
An observational test of magnetospheric magnetic field mapping
Weiss, L.A.; Thomsen, M.F.; Reeves, G.D.; Hones, E.W.; McComas, D.J.
The distortion of the geomagnetic field is a key signature of the response of the magnetosphere to the solar wind input. A number of empirical models have been devised to estimate the magnetic field direction and magnitude at any point within the magnetosphere under a variety of conditions. We describe a technique whereby the field-line mapping predicted by such models is tested by matching measurements of magnetospheric plasma energy spectra obtained by Los Alamos instruments at geosynchronous orbit with spectra obtained by instruments on the polar-orbiting DMSP satellites (at an altitude of about 800 km) at times when the two satellites are in approximate magnetic conjugacy. With up to three geosynchronous satellites and as many as four DMSP satellites in operation at any given time, there are a very large number of such two-satellite conjunctions, allowing the model mappings to be tested under a wide range of local times and geomagnetic activity. Preliminary results from the application of this technique are presented for one week of data from March, 1991.
Ultrasensitive magnetic field detection using a single artificial atom
Mustafa Bal; Chunqing Deng; Jean-Luc Orgiazzi; Florian Ong; Adrian Lupascu
Efficient detection of magnetic fields is central to many areas of research and has important practical applications ranging from materials science to geomagnetism. High sensitivity detectors are commonly built using direct current-superconducting quantum interference devices (DC-SQUIDs) or atomic systems. Here we use a single artificial atom to implement an ultrahigh sensitivity magnetometer with a size in the micron range. The artificial atom is a superconducting two-level system at low temperatures, operated in a way similar to atomic magnetometry. The high sensitivity results from quantum coherence combined with strong coupling to magnetic field. By employing projective measurements, we obtain a sensitivity of $2.7\\, \\t{pT}/\\sqrt{\\t{Hz}}$ at 10 MHz. We discuss feasible improvements that will increase the sensitivity by over one order of magnitude. The intrinsic sensitivity of this method to AC fields in the 100 kHz - 10 MHz range compares favourably with DC-SQUIDs and atomic magnetometers of equivalent spatial resolution. This result illustrates the potential of artificial quantum systems for sensitive detection and related applications.
Perfect 2-d quadrupole fields from permanent magnets
Lee, E.P.; Vella, M. [Lawrence Berkeley National Lab., CA (United States). Accelerator and Fusion Research Div.
Consider the 13-beam channel array shown in Figure 1. It is asserted that, under mathematically ideal assumptions, a pure quadrupole field is centered in each of the 13 beam channel boxes. An identical quadrupole field (for {bar H}, not {bar B}) is also centered in each of the 4 boxes containing 4 magnetic wedges located near the center of the system. An iron yoke ({mu} = {infinity}) with the displayed zig-zag shape provides a boundary condition (H{sub {parallel}} = 0) that makes the 13 channels equivalent to a portion of an infinite array. A similar array can be readily drawn for any number of beams. The quadrupole gradient in the beam channels is B{prime} = M{sub o}/2b, where M{sub o} is the remnant field of the magnetic wedges, and the channel diameter (wedge-to-wedge) is 2b. Note that a unit cell of the array, containing one beam, has diameter 2{radical}2 b (viewed from 45{degree} tilt) so its area is 8 b{sup 2}. A significant advantage of this design over those using dipolar blocks is the large fraction of cross section devoted to beam channels (50% vs 25%). Application to a heavy ion fusion driver is discussed.
Romano, P.; Guglielmino, S. L. [INAF-Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95125 Catania (Italy); Frasca, D.; Zuccarello, F. [Dipartimento di Fisica e Astronomia-Sezione Astrofisica, Universita di Catania, Via S. Sofia 78, I-95125 Catania (Italy); Ermolli, I. [INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monte Porzio Catone (Italy); Tritschler, A.; Reardon, K. P., E-mail: email@example.com [National Solar Observatory/Sacramento Peak, P.O. Box 62, Sunspot, NM 88349-0062 (United States)
We present results from the analysis of high-resolution spectropolarimetric and spectroscopic observations of the solar photosphere and chromosphere, obtained shortly before the formation of a penumbra in one of the leading polarity sunspots of NOAA active region 11490. The observations were performed at the Dunn Solar Telescope of the National Solar Observatory on 2012 May 28, using the Interferometric Bidimensional Spectrometer. The data set is comprised of a 1 hr time sequence of measurements in the Fe I 617.3 nm and Fe I 630.25 nm lines (full Stokes polarimetry) and in the Ca II 854.2 nm line (Stokes I only). We perform an inversion of the Fe I 630.25 nm Stokes profiles to derive magnetic field parameters and the line-of-sight (LOS) velocity at the photospheric level. We characterize chromospheric LOS velocities by the Doppler shift of the centroid of the Ca II 854.2 nm line. We find that, before the formation of the penumbra, an annular zone of 3''-5'' width is visible around the sunspot. In the photosphere, we find that this zone is characterized by an uncombed structure of the magnetic field although no visible penumbra has formed yet. We also find that the chromospheric LOS velocity field shows several elongated structures characterized by downflow and upflow motions in the inner and outer parts of the annular zone, respectively.
Analysis of Biological Effects and Limits of Exposure to Weak Magnetic Fields
Halgamuge, Malka N.
to weak magnetic fields and geomagnetic field to elucidate the main points of contention. Most of the weak excitation and cardio stimulation can be caused due to the current induced in the body from high power fields [2]. The energy absorption rate of these high power magnetic fields is measured by the specific
Dependence of Brownian and N�el relaxation times on magnetic field strength
Deissler, Robert J., E-mail: firstname.lastname@example.com; Wu, Yong; Martens, Michael A. [Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106 (United States)] [Department of Physics, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106 (United States)
Purpose: In magnetic particle imaging (MPI) and magnetic particle spectroscopy (MPS) the relaxation time of the magnetization in response to externally applied magnetic fields is determined by the Brownian and N�el relaxation mechanisms. Here the authors investigate the dependence of the relaxation times on the magnetic field strength and the implications for MPI and MPS. Methods: The Fokker�Planck equation with Brownian relaxation and the Fokker�Planck equation with N�el relaxation are solved numerically for a time-varying externally applied magnetic field, including a step-function, a sinusoidally varying, and a linearly ramped magnetic field. For magnetic fields that are applied as a step function, an eigenvalue approach is used to directly calculate both the Brownian and N�el relaxation times for a range of magnetic field strengths. For N�el relaxation, the eigenvalue calculations are compared to Brown's high-barrier approximation formula. Results: The relaxation times due to the Brownian or N�el mechanisms depend on the magnitude of the applied magnetic field. In particular, the N�el relaxation time is sensitive to the magnetic field strength, and varies by many orders of magnitude for nanoparticle properties and magnetic field strengths relevant for MPI and MPS. Therefore, the well-known zero-field relaxation times underestimate the actual relaxation times and, in particular, can underestimate the N�el relaxation time by many orders of magnitude. When only N�el relaxation is present�if the particles are embedded in a solid for instance�the authors found that there can be a strong magnetization response to a sinusoidal driving field, even if the period is much less than the zero-field relaxation time. For a ferrofluid in which both Brownian and N�el relaxation are present, only one relaxation mechanism may dominate depending on the magnetic field strength, the driving frequency (or ramp time), and the phase of the magnetization relative to the applied magnetic field. Conclusions: A simple treatment of N�el relaxation using the common zero-field relaxation time overestimates the relaxation time of the magnetization in situations relevant for MPI and MPS. For sinusoidally driven (or ramped) systems, whether or not a particular relaxation mechanism dominates or is even relevant depends on the magnetic field strength, the frequency (or ramp time), and the phase of the magnetization relative to the applied magnetic field.
Tokamak with in situ magnetohydrodynamic generation of toroidal magnetic field
Schaffer, Michael J. (San Diego, CA)
A tokamak apparatus includes an electrically conductive metal pressure vessel for defining a chamber and confining liquid therein. A liner disposed within said chamber defines a toroidal space within the liner and confines gas therein. The metal vessel provides an electrically conductive path linking the toroidal space. Liquid metal is forced outwardly through the chamber outside of the toroidal space to generate electric current in the conductive path and thereby generate a toroidal magnetic field within the toroidal space. Toroidal plasma is developed within the toroidal space about the major axis thereof.
Confined System with Rashba Coupling in Constant Magnetic Field
Mohammed El Bouziani; Rachid Houca; Ahmed Jellal
We study a two dimensional system of electrons with Rashba coupling in the constant magnetic field $B$ and confining potential. We algebraically diagonalize the corresponding Hamiltonian to end up with the solutions of the energy spectrum. In terms of two kinds of operator we construct two symmetries and discuss the filling of the shells with electrons for strong and weak $B$. Subsequently, we show that our system is sharing some common features with quantum optics where the exact operator solutions for the basics Jaynes-Cummings variables are derived from our results. An interesting limit is studied and the corresponding quantum dynamics is recovered.
System having unmodulated flux locked loop for measuring magnetic fields
Ganther, Jr., Kenneth R. (Olathe, KS); Snapp, Lowell D. (Blue Springs, MO)
A system (10) for measuring magnetic fields, wherein the system (10) comprises an unmodulated or direct-feedback flux locked loop (12) connected by first and second unbalanced RF coaxial transmission lines (16a, 16b) to a superconducting quantum interference device (14). The FLL (12) operates for the most part in a room-temperature or non-cryogenic environment, while the SQUID (14) operates in a cryogenic environment, with the first and second lines (16a, 16b) extending between these two operating environments.
Weston, Ken
Phase-field simulation of strain-induced domain switching in magnetic thin films
Chen, Long-Qing
Phase-field simulation of strain-induced domain switching in magnetic thin films Jia-Mian Hu, G of the Bloch point in a magnetic film with strong uniaxial magnetic anisotropy Low Temp. Phys. 37, 690 (2011) Evolution of magnetic bubble domains in manganite films Appl. Phys. Lett. 99, 042503 (2011) 360� domain wall
Weston, Ken
, and Geochemistry 16 MAGNET SCIENCE & TECHNOLOGY Engineering Materials, Instrumentation, and Magnet Technology 20NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSSPECIAL EDITION VOLUME 13 � N0. 1 � 2006 SUPPORTED HIGHLIGHTS FROM Life Sciences Chemistry Magnet Science & Technology Condensed Matter Page 15 #12;NHMFLREPORTS
Torsional oscillations of a magnetar with a tangled magnetic field
Link, Bennett
We propose a scenario for the quasi-periodic oscillations observed in magnetar flares wherein a tangled component of the stellar magnetic field introduces nearly isotropic stress that gives the fluid core of the star an effective shear modulus. In a simple, illustrative model of constant density, the tangled field eliminates the problematic Alfv\\'en continuum that would exist in the stellar core for an organized field. For a tangled field energy density comparable to that inferred from the measured dipole fields of $\\sim 10^{15}$ G in SGRs 1806-20 and 1900+14, torsional modes exist with fundamental frequencies of about 20 Hz, and mode spacings of $\\sim 10$ Hz. For fixed stellar mass and radius, the model has only one free parameter, and can account for {\\em every} observed QPO under 160 Hz to within 3 Hz for both SGRs 1806-20 and 1900+14. The combined effects of stratification and crust stresses generally decrease the frequencies of torsional oscillations by $<10$% for overtones and increase the lowest-fre...
Weston, Ken
, recognized as the world leader in magnet science, engineering, and experimental infrastructureNATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSVOLUME 11 � N0.2 � 2004 OPERATED BY: FLORIDA STATE: National High Magnetic Field Laboratory 1800 East Paul Dirac Drive Tallahassee, Florida 32310-3706 Tel: 850
Proton radiography of magnetic field produced by ultra-intense laser irradiating capacity-coil target
Wang, W W; Chen, J; Cai, H B; He, S K; Zhou, W M; Shan, L Q; Lu, F; Wu, Y C; Hong, W; Liu, D X; Bi, B; Zhang, F; Xue, F B; Li, B Y; Zhang, B; He, Y L; He, W; Jiao, J L; Dong, K G; Zhang, F Q; Deng, Z G; Zhang, Z M; Cui, B; Han, D; Zhou, K N; Wang, X D; Zhao, Z Q; Cao, L F; Zhang, B H; He, X T; Gu, Y Q
Ultra-intense ultra-short laser is firstly used to irradiate the capacity-coil target to generate magnetic field. The spatial structure and temporal evolution of huge magnetic fields were studied with time-gated proton radiography method. A magnetic flux density of 40T was measured by comparing the proton deflection and particle track simulations. Although the laser pulse duration is only 30fs, the generated magnetic field can last for over 100 picoseconds. The energy conversion efficiency from laser to magnetic field can reach as high as ~20%. The results indicate that tens of tesla (T) magnetic field could be produced in many ultra intense laser facilities around the world, and higher magnetic field could be produced by picosecond lasers.
Molten metal feed system controlled with a traveling magnetic field
Praeg, Walter F. (Palos Park, IL)
A continuous metal casting system in which the feed of molten metal is controlled by means of a linear induction motor capable of producing a magnetic traveling wave in a duct that connects a reservoir of molten metal to a caster. The linear induction motor produces a traveling magnetic wave in the duct in opposition to the pressure exerted by the head of molten metal in the reservoir so that p.sub.c =p.sub.g -p.sub.m where p.sub.c is the desired pressure in the caster, p.sub.g is the gravitational pressure in the duct exerted by the force of the head of molten metal in the reservoir, and p.sub.m is the electromagnetic pressure exerted by the force of the magnetic field traveling wave produced by the linear induction motor. The invention also includes feedback loops to the linear induction motor to control the casting pressure in response to measured characteristics of the metal being cast.
Thermoelectric Conductivities at Finite Magnetic Field and the Nernst Effect
Keun-Young Kim; Kyung Kiu Kim; Yunseok Seo; Sang-Jin Sin
We study electric, thermoelectric, and thermal conductivities of a strongly correlated system in the presence of magnetic field by gauge/gravity duality. We consider a general class of Einstein-Maxwell-Dilaton theory with axion fields imposing momentum relaxation. Analytic general formulas for DC conductivities and the Nernst signal are derived in terms of the black hole horizon data. For an explicit model study we analyse in detail the dyonic black hole modified by momentum relaxation. In this model, the Nernst signal shows a typical vortex-liquid effect when momentum relaxation effect is comparable to chemical potential. We compute all AC electric, thermoelectric, and thermal conductivities by numerical analysis and confirms that their zero frequency limits precisely reproduce our analytic formulas, which is a non-trivial consistency check of our methods. We discuss the momentum relaxation effect on conductivities including cyclotron resonance poles.
Ferrofluid nucleus phase transitions in an external uniform magnetic field
B. M. Tanygin; S. I. Shulyma; V. F. Kovalenko; M. V. Petrychuk
Phase transition between massive dense phase and diluted superparamagnetic phase is studied by means of direct molecular dynamics simulation. Equilibrium structures of ferrofluid aggregate nucleus are obtained for different values of temperature and external magnetic field magnitude. For the ferrofluid phase diagram (coordinates "field-temperature"): approximate match of experiment and simulation is shown. Obtained phase coexistence curve has opposite trend compare to some of known theoretical results. This contradiction is related to postulating and comparing of the free energy of only simplest ferrofluid structures: diluted superparamagnetic phase, linear chains of the particles, and dense globes. The present results provide more fine structure of transition from "linear chains" to "dense globes" phase, e.g. through the ring assembly structure.
Thermoelectric Conductivities at Finite Magnetic Field and the Nernst Effect
Kim, Keun-Young; Seo, Yunseok; Sin, Sang-Jin
We study electric, thermoelectric, and thermal conductivities of a strongly correlated system in the presence of magnetic field by gauge/gravity duality. We consider a general class of Einstein-Maxwell-Dilaton theory with axion fields imposing momentum relaxation. Analytic general formulas for DC conductivities and the Nernst signal are derived in terms of the black hole horizon data. For an explicit model study we analyse in detail the Dyonic black hole modified by momentum relaxation effect. In this model, the Nernst signal shows a typical vortex-liquid effect when momentum relaxation effect is comparable to chemical potential. We compute all AC electric, thermal, and thermal conductivities by numerical analysis and confirms that their zero frequency limits precisely reproduce our analytic formulas, which is a non-trivial consistency check of our methods. We discuss the momentum relaxation effect on conductivities including cyclotron frequencies.
Magnetohydrodynamic turbulent cascade of coronal loop magnetic fields
Rappazzo, A. F. [Instituto de Astrofisica de Canarias, E-38200 La Laguna, Tenerife (Spain); Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States); Bartol Research Institute, Department of Physics and Astronomy, University of Delaware, Delaware 19716 (United States); Velli, M. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)
The Parker model for coronal heating is investigated through a high resolution simulation. An inertial range is resolved where fluctuating magnetic energy E{sub M}(k{sub perpendicular}){proportional_to}k{sub perpendicular}{sup -2.7} exceeds kinetic energy E{sub K}(k{sub perpendicular}){proportional_to}k{sub perpendicular}{sup -0.6}. Increments scale as {delta}b{sub l}{approx_equal}l{sup -0.85}and {delta}u{sub l}{approx_equal}l{sup +0.2} with velocity increasing at small scales, indicating that magnetic reconnection plays a prime role in this turbulent system. We show that spectral energy transport is akin to standard magnetohydrodynamic (MHD) turbulence even for a system of reconnecting current sheets sustained by the boundary. In this new MHD turbulent cascade, kinetic energy flows are negligible while cross-field flows are enhanced, and through a series of ''reflections'' between the two fields, cascade more than half of the total spectral energy flow.
High Magnetic Field Multipoles Generated by Superconductor Magnetization within a Set of Nested Superconducting Correction Coils
Green, M.A.
magnetization of the superconductor in the long correctorsMultipoles Generated by Superconductor Magnetization WithinMULTIPOLES GENERATED BY SUPERCONDUCTOR MAGNETIZATION WITHIN
Memorandum, Approval of a Permanent Variance Regarding Static Magnetic Fields at Brookhaven National Laboratory (Variance 102 1)
Broader source: Energy.gov [DOE]
Approval of a Permanenet Variance Regarding Static Magnetic Fields at Brookhaven National Laboratory (Variance 1021)
Magnetic resonance studies of cement based materials in inhomogeneous magnetic fields
Boguszynska, Joanna [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, Poznan (Poland); Brown, Marc C.A. [School of Physical Sciences, University of Kent, Canterbury, Kent, CT2 7NR (United Kingdom); McDonald, Peter J. [School of Electronics and Physical Sciences, University of Surrey, Surrey, GU2 7XH (United Kingdom)]. E-mail: email@example.com; Mitchell, Jonathan [School of Electronics and Physical Sciences, University of Surrey, Surrey, GU2 7XH (United Kingdom); Mulheron, Mike [School of Engineering, University of Surrey, Surrey, GU2 7XH (United Kingdom); Tritt-Goc, Jadwiga [Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, Poznan (Poland); Verganelakis, Dimitris A. [Department of Chemical Engineering, University of Cambridge, Cambridge, CB2 3RA (United Kingdom)
Single-sided magnets give hope that Nuclear Magnetic Resonance (NMR) might in future be used for in situ characterisation of hydration and water transport in the surface layers of concrete slabs. Towards that end, a portable NMR-MOUSE (MObile Universal Surface Explorer) has been used to follow the hydration of gypsum based plaster, a Portland cement paste and concrete mortar. The results compare favourably to those obtained using a standard laboratory bench-top spectrometer. Further, stray field imaging (STRAFI) based methods have been used with embedded NMR detector coils to study water transport across a mortar/topping interface. The measured signal amplitudes are found to correlate with varying sample conditions.
First experiments probing the collision of parallel magnetic fields using laser-produced plasmas
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Rosenberg, M. J.; Li, C. K.; Fox, W.; Igumenshchev, I.; Seguin, F. H.; Town, R. P.; Frenje, J. A.; Stoeckl, C.; Glebov, V.; Petrasso, R. D.
Novel experiments to study the strongly-driven collision of parallel magnetic fields in ?~10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell (PIC) simulations predict a stronger flux compressionmore��and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.��less
First experiments probing the collision of parallel magnetic fields using laser-produced plasmas
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Rosenberg, M. J. [Plasma Science and Fusion Center and Massachusetts Institute of Technology, Cambridge, MA (United States); Li, C. K. [Plasma Science and Fusion Center and Massachusetts Institute of Technology, Cambridge, MA (United States); Fox, W. [Princeton Plasma Physics Laboratory, Princeton, NJ (United States)] (ORCID:000000016289858X); Igumenshchev, I. [University of Rochester, NY (United States). Laboratory for Laser Energetics; Seguin, F. H. [Plasma Science and Fusion Center and Massachusetts Institute of Technology, Cambridge, MA (United States); Town, R. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Frenje, J. A. [Plasma Science and Fusion Center and Massachusetts Institute of Technology, Cambridge, MA (United States)] (ORCID:0000000168460378); Stoeckl, C. [University of Rochester, NY (United States). Laboratory for Laser Energetics; Glebov, V. [University of Rochester, NY (United States). Laboratory for Laser Energetics; Petrasso, R. D. [Plasma Science and Fusion Center and Massachusetts Institute of Technology, Cambridge, MA (United States)] (ORCID:0000000258834054)
Novel experiments to study the strongly-driven collision of parallel magnetic fields in ?~10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell (PIC) simulations predict a stronger flux compression and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.
First experiments probing the collision of parallel magnetic fields using laser-produced plasmas
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Rosenberg, M. J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts (United States); Li, C. K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; Fox, W. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543, USA] (ORCID:000000016289858X); Igumenshchev, I. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA; S??guin, F. H. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA; Town, R. P. [Lawrence Livermore National Laboratory, Livermore, California 94550, USA; Frenje, J. A. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA] (ORCID:0000000168460378); Stoeckl, C. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA; Glebov, V. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623, USA; Petrasso, R. D. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA] (ORCID:0000000258834054)
Novel experiments to study the strongly-driven collision of parallel magnetic fields in �~10, laser-produced plasmas have been conducted using monoenergetic proton radiography. These experiments were designed to probe the process of magnetic flux pileup, which has been identified in prior laser-plasma experiments as a key physical mechanism in the reconnection of anti-parallel magnetic fields when the reconnection inflow is dominated by strong plasma flows. In the present experiments using colliding plasmas carrying parallel magnetic fields, the magnetic flux is found to be conserved and slightly compressed in the collision region. Two-dimensional (2D) particle-in-cell (PIC) simulations predict a stronger flux compression and amplification of the magnetic field strength, and this discrepancy is attributed to the three-dimensional (3D) collision geometry. Future experiments may drive a stronger collision and further explore flux pileup in the context of the strongly-driven interaction of magnetic fields.
High Field Magnetization measurements of uranium dioxide single crystals (P08358- E003-PF)
K. Gofryk; N. Harrison; M. Jaime
Conclusions: Our preliminary high field magnetic measurements of UO2 are consistent with a complex nature of the magnetic ordering in this material, compatible with the previously proposed non-collinear 3-k magnetic structure. Further extensive magnetic studies on well-oriented (<100 > and <111>) UO2 crystals are planned to address the puzzling behavior of UO2 in both antiferromagnetic and paramagnetic states at high fields.
Electric Field Control of Ferromagnetism and Magnetic Devices Using Multiferroics
Heron, John Thomas
deplete holes from a magnetic semiconductor (InMnAs) using aof holes in the magnetic semiconductor while the black arrowto investigate magnetic semiconductors in his group. I had
Testing a Solar Coronal Magnetic Field Extrapolation Code with the Titov-Demoulin Magnetic Flux Rope Model
Jiang, Chaowei
In the solar corona, magnetic flux rope is believed to be a fundamental structure accounts for magnetic free energy storage and solar eruptions. Up to the present, the extrapolation of magnetic field from boundary data is the primary way to obtain fully three-dimensional magnetic information of the corona. As a result, the ability of reliable recovering coronal magnetic flux rope is important for coronal field extrapolation. In this paper, our coronal field extrapolation code (CESE-MHD-NLFFF, Jiang & Feng 2012) is examined with an analytical magnetic flux rope model proposed by Titov & Demoulin (1999), which consists of a bipolar magnetic configuration holding an semi-circular line-tied flux rope in force-free equilibrium. By using only the vector field in the bottom boundary as input, we test our code with the model in a representative range of parameter space and find that the model field is reconstructed with high accuracy. Especially, the magnetic topological interfaces formed between the flux rop...
Collisionless magnetic reconnection in the presence of a sheared velocity field
Faganello, M. [Ecole Polytechnique, LPP, Palaiseau, 91128 (France); Pegoraro, F.; Califano, F. [Department of Physics, University of Pisa and CNISM, Pisa, 56127 (Italy); Marradi, L. [Department of Physics, University of Pisa and CNISM, Pisa, 56127 (Italy)] [Universite de Nice Sophia Antipolis, CNRS, Observatoire de la Cote d'Azur, 06304 Nice (France)
The linear theory of magnetic field lines reconnection in a two-dimensional configuration in the presence of a (Kelvin-Helmholtz stable) sheared velocity field is investigated within a single fluid model, where the onset of magnetic field line reconnection is made possible by the effect of electron inertia in the so called large DELTA{sup '} regime.
Weston, Ken
NATIONAL HIGH MAGNETIC FIELD LABORATORY REPORTSSPRING EDITION VOLUME 13 � N0. 2 � 2006 SUPPORTED BY OF FLORIDA � LOS ALAMOS NATIONAL LABORATORY Pulsed Field Facility: Heat caPacity in tHe 20 t dilution ReFRigeRatoR tRiPle Resonance PRobe #12;NHMFLREPORTS C O N T E N T S Published by: National High Magnetic Field
High Field Magnet R&D in the USA
Gourlay, S.A.
beam instmmentation, accelerator physics shIdies, and designShldy in terms of accelerator physics and magnet design.magnet technology and accelerator physics and approach the
artificial magnetic fields: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Galea 2003-02-10 74 Magnetic anisotropy of elongated thin ferromagnetic nano-islands for artificial spin ice arrays Physics Websites Summary: Magnetic anisotropy of elongated thin...
Gravitational waves interacting with a spinning charged particle in the presence of a uniform magnetic field
D. B. Papadopoulos
The equations which determine the response of a spinning charged particle moving in a uniform magnetic field to an incident gravitational wave are derived in the linearized approximation to general relativity. We verify that 1) the components of the 4-momentum, 4-velocity and the components of the spinning tensor, both electric and magnetic moments, exhibit resonances and 2) the co-existence of the uniform magnetic field and the GW are responsible for the resonances appearing in our equations. In the absence of the GW, the magnetic field and the components of the spin tensor decouple and the magnetic resonances disappear.
On the delayed gas breakdown in a ringing theta-pinch with bias magnetic field
Meeks, Warner C.; Rovey, Joshua L. [Mechanical and Aerospace Engineering, Missouri University of Science and Technology, Rolla, Missouri 65409-0050 (United States)
A single particle model and particle-in-cell simulations are used to elucidate the breakdown physics in a ringing theta-pinch with a bias magnetic field. Previous experimental results show that gas breakdown occurs when the bias magnetic field is nullified by the theta-pinch magnetic field. The analyses presented here agree with the experimental results and show that electron kinetic energy does not exceed the ionization threshold of deuterium until the net magnetic field is approximately zero. Despite the presence of a strong electric field, the gyromotion of electrons within the bias magnetic field prevents them from gaining energy necessary to ionize the gas. Parametric analysis of the peak electron energy as a function of the bias and pre-ionization magnetic fields reveals that: (1) when the bias magnetic field is Almost-Equal-To 97% of the pre-ionization magnetic field, peak electron energies are highly erratic resulting in poor overall ionization, and (2) full ionization with repeatable behavior requires a pre-ionization to bias magnetic field ratio of approximately 2 to 1 or higher.
Assessing human exposure to power-frequency electric and magnetic fields
Kaune, W.T. [EM Factors, Richland, WA (United States)
This paper reviews published literature and current problems relating to the assessment of occupational and residential human exposures to power-frequency electric and magnetic fields. Available occupational exposure data suggest that the class of job titles known as electrical workers may be an effective surrogate for time-weighted-average (TWA) magnetic-field (but not electric-field) exposure. Current research in occupational-exposure assessment is directed to the construction of job-exposure matrices based on electric- and magnetic-field measurements and estimates of worker exposures to chemicals and other factors of interest. Recent work has identified five principal sources of residential magnetic fields: electric power transmission lines, electric power distribution lines, ground currents, home wiring, and home appliances. Existing residential-exposure assessments have used one or more of the following techniques: questionnaires, wiring configuration coding, theoretical field calculations, spot electric- and magnetic-field measurements, fixed-site magnetic-field recordings, personal-exposure measurements, and geomagnetic-field measurements. Available normal-power magnetic-field data for residences differ substantially between studies. It is not known if these differences are due to geographical differences, differences in measurement protocols, or instrumentation differences. Available data suggest, but are far from proving, that spot measurements may be more effective than wire codes as predictors of long-term historical magnetic-field exposure. Two studies find that away-from-home TWA magnetic-field exposures are less variable than at home exposures. The importance of home appliances as contributors to total residential magnetic-field exposure is not known at this time. It also is not known what characteristics (if any) of residential electric and magnetic fields are determinants of human health effects. 41 refs., 9 figs., 10 tabs.
Weston, Ken
UPPort scientists neWs FroM tHe dc FieLd FaciLitY: QUantUM HaLL eFFect in graPHene at HigH Magnetic FieLds ed NEARING COMPLETION 14 NEWS FROM THE DC FIELD FACILITY QuantuM Hall effect In grapHene at HIgH MagnetIc f
Apparatus and method for generating a magnetic field by rotation of a charge holding object
Gerald, II, Rex E. (Brookfield, IL); Vukovic, Lela (Westchester, IL); Rathke, Jerome W. (Homer Glenn, IL)
A device and a method for the production of a magnetic field using a Charge Holding Object that is mechanically rotated. In a preferred embodiment, a Charge Holding Object surrounding a sample rotates and subjects the sample to one or more magnetic fields. The one or more magnetic fields are used by NMR Electronics connected to an NMR Conductor positioned within the Charge Holding Object to perform NMR analysis of the sample.
SU-E-J-233: A Facility for Radiobiological Experiments in a Large Magnetic Field
Carlone, M; Heaton, R; Keller, H [Princess Margaret Hospital, Toronto, ON (Canada); University of Toronto, Toronto, ON (Canada); Wouters, B [Ontario Cancer Institute, Toronto, ON (Canada); University of Toronto, Toronto, ON (Canada); Jaffray, D [Princess Margaret Hospital, Toronto, ON (Canada); Ontario Cancer Institute, Toronto, ON (Canada); University of Toronto, Toronto, ON (Canada)
Purpose: There is considerable interest in developing medical linear accelerators with integrated image guidance by MRI. Less work has been done on the fundamental biology of cell survival in the presence of a strong magnetic field. The purpose of this work is to describe an experimental system capable of measuring cell survival response in the types of MRI-linac systems currently under development. Methods: We have integrated a cobalt irradiator with a solenoid magnet. The solenoid magnet has inner diameter of 10 cm. To enable measurement of the biological effects as a function of depth, we are utilizing the sliced gel technique, in which cells are embedded and fixed within a gelatin matrix. Irradiated cells at defined positions (sub mm resolution) can subsequently be recovered and assessed for cell survival or other biological effects. Results: The magnetic field profile in the solenoid has a peak magnetic field 36 cm below the top edge of the magnet bore and can be placed at and SAD of 100 cm. At a solenoid current of 35 A, the peak magnetic field is 0.25 T. The dose rate of the cobalt irradiator is 16 cGy/min at 100 cm SAD. EBT3 film was used to demonstrate the system functionality. It was irradiated at 1 cm depth at 100 cm SSD with a 4�4 field to 1.5 Gy in a 0.25 T magnetic field. The dose profile was similar between this film and the control exposure without magnetic field. Conclusion: Integrating a cobalt irradiator with a high field magnet is demonstrated. The magnetic field at the cobalt defining head was minimal and did not interfere with the functioning of this unit. Cell survival experiments can be reproduced exactly in the presence or absence of a magnetic field since a resistive magnet is used.
Path Integral Confined Dirac Fermions in a Constant Magnetic Field
Abdeldjalil Merdaci; Ahmed Jellal; Lyazid Chetouani
We consider Dirac fermion confined in harmonic potential and submitted to a constant magnetic field. The corresponding solutions of the energy spectrum are obtained by using the path integral techniques. For this, we begin by establishing a symmetric global projection, which provides a symmetric form for the Green function. Based on this, we show that it is possible to end up with the propagator of the harmonic oscillator for one charged particle. After some transformations, we derive the normalized wave functions and the eigenvalues in terms of different physical parameters and quantum numbers. By interchanging quantum numbers, we show that our solutions possed interesting properties. The density of current and the non-relativistic limit are analyzed where different conclusions are obtained.
Formation of current filaments and magnetic field generation in a quantum current-carrying plasma
Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of)] [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Taghadosi, M. R.; Majedi, S.; Khorashadizadeh, S. M. [Physics Department, University of Birjand, Birjand (Iran, Islamic Republic of)] [Physics Department, University of Birjand, Birjand (Iran, Islamic Republic of)
The nonlinear dynamics of filamentation instability and magnetic field in a current-carrying plasma is investigated in the presence of quantum effects using the quantum hydrodynamic model. A new nonlinear partial differential equation is obtained for the spatiotemporal evolution of the magnetic field in the diffusion regime. This equation is solved by applying the Adomian decomposition method, and then the profiles of magnetic field and electron density are plotted. It is shown that the saturation time of filamentation instability increases and, consequently, the instability growth rate and the magnetic field amplitude decrease in the presence of quantum effects.
Spectroscopic Determination of the Magnetic Fields in Exploding Wire and X-pinch Plasmas
Hammer, David A.
In this report, we summarize the progress that was made toward developing a new magnetic field diagnostic known as Zeeman Broadening for current carrying high energy density plasmas.
Origin of the resonant dependence of the instability current in a magnetic field
Nevirkovets, I.P.; Rudenko, E.M.
The instability current in the case of Sn--I--Sn tunnel junctions in weak magnetic fields is investigated in detail. (AIP)
Phase Transition in Ferromagnetic Ising Models with Non-Uniform External Magnetic Fields
Rodrigo Bissacot; Leandro Cioletti
In this article we study the phase transition phenomenon for the Ising model under the action of a non-uniform external magnetic field. We show that the Ising model on the hypercubic lattice with a summable magnetic field has a first-order phase transition and, for any positive (resp. negative) and bounded magnetic field, the model does not present the phase transition phenomenon whenever $\\liminf h_i> 0$, where ${\\bf h} = (h_i)_{i \\in \\Z^d}$ is the external magnetic field.
Shinnaga, Hiroko; Phillips, Thomas G. [California Institute of Technology Submillimeter Observatory, 111 Nowelo Street, Hilo, HI 96720 (United States); Novak, Giles [Department of Physics and Astronomy, Northwestern University, 633 Clark Street Evanston, IL 60208 (United States); Vaillancourt, John E. [Stratospheric Observatory for Infrared Astronomy, Universities Space Research Association, NASA Ames Research Center, Moffet Field, CA 94035 (United States); Machida, Masahiro N. [Department of Earth and Planetary Sciences, Faculty of Sciences, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581 (Japan); Kataoka, Akimasa [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Tomisaka, Kohji [National Astronomical Observatory of Japan and Department of Astronomy, School of Physical Sciences, Graduate University for Advanced Studies (SOKENDAI), Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan); Davidson, Jacqueline; Houde, Martin [School of Physics, University of Western Australia, 35 Stirling Highway, Crawley WA 6009, Perth (Australia); Dowell, C. Darren [Jet Propulsion Laboratory, California Institute of Technology, MS 169-506, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Leeuw, Lerothodi [SETI Institute, 515 North Whisman Avenue, Mountain View, CA 94043 (United States)
We measured polarized dust emission at 350 {mu}m toward the high-mass star-forming massive dense clump IRAS 20126+4104 using the SHARC II Polarimeter, SHARP, at the Caltech Submillimeter Observatory. Most of the observed magnetic field vectors agree well with magnetic field vectors obtained from a numerical simulation for the case when the global magnetic field lines are inclined with respect to the rotation axis of the dense clump. The results of the numerical simulation show that rotation plays an important role on the evolution of the massive dense clump and its magnetic field. The direction of the cold CO 1-0 bipolar outflow is parallel to the observed magnetic field within the dense clump as well as the global magnetic field, as inferred from optical polarimetry data, indicating that the magnetic field also plays a critical role in an early stage of massive star formation. The large-scale Keplerian disk of the massive (proto)star rotates in an almost opposite sense to the clump's envelope. The observed magnetic field morphology and the counterrotating feature of the massive dense clump system provide hints to constrain the role of magnetic fields in the process of high-mass star formation.
Dispersion relation and growth rate in a Cherenkov free electron laser: Finite axial magnetic field
Kheiri, Golshad; Esmaeilzadeh, Mahdi [Department of Physics, Iran University of Science and Technology, Tehran 16844 (Iran, Islamic Republic of)] [Department of Physics, Iran University of Science and Technology, Tehran 16844 (Iran, Islamic Republic of)
A theoretical analysis is presented for dispersion relation and growth rate in a Cherenkov free electron laser with finite axial magnetic field. It is shown that the growth rate and the resonance frequency of Cherenkov free electron laser increase with increasing axial magnetic field for low axial magnetic fields, while for high axial magnetic fields, they go to a saturation value. The growth rate and resonance frequency saturation values are exactly the same as those for infinite axial magnetic field approximation. The effects of electron beam self-fields on growth rate are investigated, and it is shown that the growth rate decreases in the presence of self-fields. It is found that there is an optimum value for electron beam density and Lorentz relativistic factor at which the maximum growth rate can take place. Also, the effects of velocity spread of electron beam are studied and it is found that the growth rate decreases due to the electron velocity spread.
Electron-cyclotron damping of helicon waves in low diverging magnetic fields
Lafleur, T.; Charles, C.; Boswell, R. W. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia)
Particle-in-cell simulations are performed to investigate wave propagation and absorption behavior of low-field (B{sub 0}<5 mT) helicon waves in the presence of a diverging magnetic field. The 1D electromagnetic simulations, which include experimental external magnetic field profiles, provide strong evidence for electron-cyclotron damping of helicon waves in the spatially decaying nonuniform magnetic field. For a dipole-type magnetic field configuration, the helicon waves are absence in the downstream (lower field) region of the plasma and are observed to be completely absorbed. As the magnetic field is changed slightly however, wave damping decreases, and waves are able to propagate freely downstream, confirming previous experimental measurements of this phenomenon.
Helium gas bubble trapped in liquid helium in high magnetic field
Bai, H., E-mail: firstname.lastname@example.com; Hannahs, S. T.; Markiewicz, W. D.; Weijers, H. W. [National High Magnetic Field Laboratory, Florida State University, Tallahassee, Florida 32310 (United States)
High magnetic field magnets are used widely in the area of the condensed matter physics, material science, chemistry, geochemistry, and biology at the National High Magnetic Field Laboratory. New high field magnets of state-of-the-art are being pursued and developed at the lab, such as the current developing 32?T, 32?mm bore fully superconducting magnet. Liquid Helium (LHe) is used as the coolant for superconducting magnets or samples tested in a high magnetic field. When the magnetic field reaches a relatively high value the boil-off helium gas bubble generated by heat losses in the cryostat can be trapped in the LHe bath in the region where BzdBz/dz is less than negative 2100 T{sup 2}/m, instead of floating up to the top of LHe. Then the magnet or sample in the trapped bubble region may lose efficient cooling. In the development of the 32?T magnet, a prototype Yttrium Barium Copper Oxide coil of 6 double pancakes with an inner diameter of 40?mm and an outer diameter of 140?mm was fabricated and tested in a resistive magnet providing a background field of 15?T. The trapped gas bubble was observed in the tests when the prototype coil was ramped up to 7.5?T at a current of 200?A. This letter reports the test results on the trapped gas bubble and the comparison with the analytical results which shows they are in a good agreement.
Arrangement for measuring the field angle of a magnetic field as a function of axial position within a magnet bore tube
Pidcoe, Stephen V. (Bonita, CA); Zink, Roger A. (Desoto, TX); Boroski, William N. (Aurora, IL); McCaw, William R. (Burr Ridge, IL)
An arrangement for measuring the field angle of a magnetic field as a function of axial position within a magnet bore tube of a magnet such as is used with the Superconducting Super Collider (SSC). The arrangement includes a magnetic field alignment gauge that is carried through the magnet bore tube by a positioning shuttle in predetermined increments. The positioning shuttle includes an extensible body assembly which is actuated by an internal piston arrangement. A pair of spaced inflatable cuffs are carried by the body assembly and are selectively actuated in cooperation with pressurizing of the piston to selectively drive the positioning shuttle in an axial direction. Control of the shuttle is provided by programmed electronic computer means located exteriorly of the bore tube and which controls valves provided pressurized fluid to the inflatable cuss and the piston arrangement.
Chiral dynamics in a magnetic field from the functional renormalization group
Kazuhiko Kamikado; Takuya Kanazawa
We investigate the quark-meson model in a magnetic field using the exact functional renormalization group equation beyond the local-potential approximation. Our truncation of the effective action involves anisotropic wave function renormalization for mesons, which allows us to investigate how the magnetic field distorts the propagation of neutral mesons. Solving the flow equation numerically, we find that the transverse velocity of mesons decreases with the magnetic field at all temperatures, which is most prominent at zero temperature. The meson screening masses and the pion decay constants are also computed. The constituent quark mass is found to increase with magnetic field at all temperatures, resulting in the crossover temperature that increases monotonically with the magnetic field. This tendency is consistent with most model calculations but not with the lattice simulation performed at the physical point. Our work suggests that the strong anisotropy of meson propagation may not be the fundamental origin of the inverse magnetic catalysis.
Flavoured Large N Gauge Theory on a Compact Space with an External Magnetic Field
Veselin G. Filev; Matthias Ihl
The phase structure of flavoured N=2 SYM on a three sphere in an external magnetic field is studied. The pairing effect of the magnetic field competes with the dissociating effect of the Casimir free energy, leading to an interesting phase structure of confined and deconfined phases separated by a critical curve of a first order quantum phase transition. At vanishing magnetic field the phase transition is of a third order. For sufficiently strong magnetic field, the only stable phase is the confined phase and magnetic catalysis of chiral symmetry breaking is realized. The meson spectra of the theory exhibit Zeeman splitting and level crossing and feature a finite jump at the phase transition between the confined and deconfined phases. At strong magnetic field the ground state has a massless mode corresponding to the Goldstone boson associated with the spontaneously broken U(1) R-symmetry analogous to the eta' meson in QCD.
Study of the electric field formation in a multi-cusped magnetic field
Liu, Hui, E-mail: firstname.lastname@example.com; Yu, Daren, E-mail: email@example.com [Lab of Plasma Propulsion, Mail Box 458, Harbin Institute of Technology (HIT), Harbin 150001 (China); Wu, Huan; Zhao, Yinjian; Ma, Chengyu; Wang, Di; Wei, Haoyu [School of Energy Science and Engineering, Harbin Institute of Technology (HIT), Harbin 150001 (China)
The multi-cusped field thruster is a kind of electric thruster adopting a cusped magnetic field to achieve a potentially longer lifetime. It is observed in some experiments that the main electric potential drop forms near the exhaust plane, but the formation mechanism of the electric field in this kind of thrusters is not fully clear yet. Based on the analysis of the electron movement, a 2D Particle-in-Cell plus Monte Carlo model is built to reveal the difference of the constraint to electrons between the central leak path and the lateral region of the thruster. Electron trajectories from cathode are analyzed furthermore. It is found that the central leak path inside the discharge channel may play a significant role in the formation of the main electric potential drop near the exhaust plane.
Magnetoconvection and dynamo coefficients III: alpha-effect and magnetic pumping in the rapid rotation regime
P. J. K�pyl�; M. J. Korpi; M. Ossendrijver; M. Stix
Aims. The alpha- and gamma-effects, which are responsible for the generation and turbulent pumping of large scale magnetic fields, respectively, due to passive advection by convection are determined in the rapid rotation regime corresponding to the deep layers of the solar convection zone. Methods. A 3D rectangular local model is used for solving the full set of MHD equations in order to compute the electromotive force (emf), E = , generated by the interaction of imposed weak gradient-free magnetic fields and turbulent convection with varying rotational influence and latitude. By expanding the emf in terms of the mean magnetic field, E_i = a_ij , all nine components of a_ij are computed. The diagonal elements of a_ij describe the alpha-effect, whereas the off-diagonals represent magnetic pumping. The latter is essentially the advection of magnetic fields by means other than the underlying large-scale velocity field. Comparisons are made to analytical expressions of the coefficients derived under the first-order smoothing approximation (FOSA). Results. In the rapid rotation regime the latitudinal dependence of the alpha-components responsible for the generation of the azimuthal and radial fields does not exhibit a peak at the poles, as is the case for slow rotation, but at a latitude of about 30 degrees. The magnetic pumping is predominantly radially down- and latitudinally equatorward as in earlier studies. The numerical results compare surprisingly well with analytical expressions derived under first-order smoothing, although the present calculations are expected to lie near the limits of the validity range of FOSA.
Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma
Woolley, Robert D. (Hillsborough, NJ)
A method and apparatus for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring. A strain gauge is mounted on the first spring, and electronic means to continually monitor strain gauge resistance variations is provided. Electronic means for providing a known current pulse waveform to be periodically injected into each coil to create a time-varying torque on the rotor assembly in the toroidal direction causes mechanical strain variations proportional to the torque in the mounting means and springs so that strain gauge measurement of the variation provides periodic magnetic field measurements independent of the magnetic field measured by the electronic integrators.
Method and apparatus for steady-state magnetic measurement of poloidal magnetic field near a tokamak plasma
Woolley, R.D.
A method and apparatus are disclosed for the steady-state measurement of poloidal magnetic field near a tokamak plasma, where the tokamak is configured with respect to a cylindrical coordinate system having z, phi (toroidal), and r axes. The method is based on combining the two magnetic field principles of induction and torque. The apparatus includes a rotor assembly having a pair of inductive magnetic field pickup coils which are concentrically mounted, orthogonally oriented in the r and z directions, and coupled to remotely located electronics which include electronic integrators for determining magnetic field changes. The rotor assembly includes an axle oriented in the toroidal direction, with the axle mounted on pivot support brackets which in turn are mounted on a baseplate. First and second springs are located between the baseplate and the rotor assembly restricting rotation of the rotor assembly about its axle, the second spring providing a constant tensile preload in the first spring. A strain gauge is mounted on the first spring, and electronic means to continually monitor strain gauge resistance variations is provided. Electronic means for providing a known current pulse waveform to be periodically injected into each coil to create a time-varying torque on the rotor assembly in the toroidal direction causes mechanical strain variations proportional to the torque in the mounting means and springs so that strain gauge measurement of the variation provides periodic magnetic field measurements independent of the magnetic field measured by the electronic integrators. 6 figs.
Dynamics of the O(N) model in a strong magnetic background field as a modified noncommutative field theory
Jafari Salim, Amir [Department of Physics, Sharif University of Technology, P.O. Box 11365-9161, Tehran (Iran, Islamic Republic of); Sadooghi, Neda [Institute for Studies in Theoretical Physics and Mathematics (IPM), School of Physics, P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)
In the presence of a strong magnetic field, the effective action of a composite scalar field in a scalar O(N) model is derived using two different methods. First, in the framework of world-line formalism, the 1PI n-point vertex function for the composites is determined in the limit of a strong magnetic field. Then, the n-point effective action of the composites is calculated in the regime of lowest Landau level dominance. It is shown that in the limit of a strong magnetic field, the results coincide and an effective field theory arises which is comparable with the conventional noncommutative field theory. In contrast to the ordinary case, however, the UV/IR mixing is absent in this modified noncommutative field theory.
Nanoscale Diffusion Studies of Lipid Membranes National High Magnetic Field Laboratory
Weston, Ken
Magnetic Resonance Imaging & Spectroscopy User Facility, University of Florida Chemical Engineering We haveNanoscale Diffusion Studies of Lipid Membranes National High Magnetic Field Laboratory Advanced for the facility's future use. This will serve to enhance infrastructure for research and education at the Magnet
SUMMERVOLUME 14 No.31 SUMMER 2007 VOLUME 14 NO. 3 NATIONAL HIGH MAGNETIC FIELD LABORATORY
Weston, Ken
a team of engineers capable of pushing magnetic fields to new highs? you already know the answer to announce that a key person who helped lead the magnet engineering team to world prominence no longer has of the Magnet Science & Technology group, as well as its chief engineer. In addition to keeping many balls
Uhlmann, Gunther
of reversible systems 36 6.4. Generic local boundary rigidity 38 Appendix A. Geometry of magnetic systems 42 A.1. Santal´o's formula 45 A.5. Index form of a magnetic geodesic 46 Appendix B. Study of a certain classTHE BOUNDARY RIGIDITY PROBLEM IN THE PRESENCE OF A MAGNETIC FIELD NURLAN S. DAIRBEKOV, GABRIEL P
Cosmic rays and the magnetic field of the nearby starburst galaxy NGC 253
V. Heesen; R. -J. Dettmar; M. Krause; R. Beck
Using radio polarimetry we study the connection between the transport of cosmic rays (CR's), the three-dimensional magnetic field structure, and features of other ISM phases in the halo of NGC 253. We present a new sensitive radio continuum map of NGC 253 obtained from combined VLA and Effelsberg observations at lambda 6.2 cm. We find a prominent radio halo with a scaleheight of the thick radio disk of 1.7 kpc. The linear dependence between the local scaleheight of the vertical continuum emission and the cosmic ray electron (CRE) lifetime requires a vertical CR bulk speed of 270 km s^-1. The magnetic field structure of NGC 253 resembles an ``X''-shaped configuration where the orientation of the large-scale magnetic field is plane-parallel only in the inner regions of the disk and at small distances from the galactic midplane. At larger galactocentric radii and further away from the midplane the vertical component becomes important. This is most clearly visible at the location of the ``radio spur'' southeast of the nucleus, where the magnetic field orientation is almost vertical. We made a simple model for the dominant toroidal (r,phi) magnetic field component using a spiral magnetic field with prescribed inclination and pitch angle. The residual poloidal (r,phi,z) magnetic field component which was revealed by subtracting the model from the observations shows a distinct ``X''-shaped magnetic field orientation centered on the nucleus. The orientation angle of the poloidal magnetic field is consistent with a magnetic field transport described by the superposition of the vertical CR bulk speed and the rotation velocity. Hence, we propose a disk wind which transports cosmic rays, magnetic field, and (partially) ionized gas from the disk into the halo.
Guo Fan; Li Shengtai; Li Hui; Li, David [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Giacalone, Joe; Jokipii, J. R. [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721 (United States)
We have performed extensive two-dimensional magnetohydrodynamic simulations to study the amplification of magnetic fields when a supernova blast wave propagates into a turbulent interstellar plasma. The blast wave is driven by injecting high pressure in the simulation domain. The interstellar magnetic field can be amplified by two different processes, occurring in different regions. One is facilitated by the fluid vorticity generated by the 'rippled' shock front interacting with the background turbulence. The resulting turbulent flow keeps amplifying the magnetic field, consistent with earlier work. The other process is facilitated by the growth of the Rayleigh-Taylor instability at the contact discontinuity between the ejecta and the shocked medium. This can efficiently amplify the magnetic field and tends to produce the highest magnetic field. We investigate the dependence of the amplification on numerical parameters such as grid-cell size and on various physical parameters. We show that the magnetic field has a characteristic radial profile such that the downstream magnetic field gets progressively stronger away from the shock. This is because the downstream magnetic field needs a finite time to reach the efficient amplification, and will get further amplified in the Rayleigh-Taylor region. In our simulation, we do not observe a systematic strong magnetic field within a small distance to the shock. This indicates that if the magnetic-field amplification in supernova remnants indeed occurs near the shock front, other processes such as three-dimensional instabilities, plasma kinetics, and/or cosmic ray effect may need to be considered to explain the strong magnetic field in supernova remnants.
Nonideal evolution of nonaxisymmetric, force-free magnetic fields in a magnetar
Mastrano, Alpha
Recent numerical magnetohydrodynamic calculations by Braithwaite and collaborators support the `fossil field' hypothesis regarding the origin of magnetic fields in compact stars and suggest that the resistive evolution of the fossil field can explain the reorganisation and decay of magnetar magnetic fields. Here, these findings are modelled analytically by allowing the stellar magnetic field to relax through a quasistatic sequence of nonaxisymmetric, force-free states, by analogy with spheromak relaxation experiments, starting from a random field. Under the hypothesis that the force-free modes approach energy equipartition in the absence of resistivity, the output of the numerical calculations is semiquantitatively recovered: the field settles down to a linked poloidal-toroidal configuration, which inflates and becomes more toroidal as time passes. A qualitatively similar (but not identical) end state is reached if the magnetic field evolves by exchanging helicity between small and large scales according to a...
Nanoscale magnetic field mapping with a single spin scanning probe magnetometer
Rondin, L.; Tetienne, J.-P.; Spinicelli, P.; Roch, J.-F.; Jacques, V. [Laboratoire de Photonique Quantique et Moleculaire, Ecole Normale Superieure de Cachan and CNRS UMR 8537, 94235 Cachan Cedex (France); Dal Savio, C.; Karrai, K. [Attocube systems AG, Koeniginstrasse 11A RGB, Munich 80539 (Germany); Dantelle, G. [Laboratoire de Physique de la Matiere Condensee, Ecole Polytechnique and CNRS UMR 7643, 91128 Palaiseau (France); Thiaville, A.; Rohart, S. [Laboratoire de Physique des Solides, Universite Paris-Sud and CNRS UMR 8502, 91405 Orsay (France)
We demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique on the electron spin resonance frequency of a single nitrogen-vacancy defect placed at the apex of an atomic force microscope tip. In addition, we report an all-optical magnetic imaging technique which is sensitive to large off-axis magnetic fields, thus extending the operation range of diamond-based magnetometry. Both techniques are illustrated by using a magnetic hard disk as a test sample. Owing to the non-perturbing and quantitative nature of the magnetic probe, this work should open up numerous perspectives in nanomagnetism and spintronics.
High-frequency electric field measurement using a toroidal antenna
Lee, Ki Ha (Lafayette, CA)
A simple and compact method and apparatus for detecting high frequency electric fields, particularly in the frequency range of 1 MHz to 100 MHz, uses a compact toroidal antenna. For typical geophysical applications the sensor will be used to detect electric fields for a wide range of spectrum starting from about 1 MHz, in particular in the frequency range between 1 to 100 MHz, to detect small objects in the upper few meters of the ground. Time-varying magnetic fields associated with time-varying electric fields induce an emf (voltage) in a toroidal coil. The electric field at the center of (and perpendicular to the plane of) the toroid is shown to be linearly related to this induced voltage. By measuring the voltage across a toroidal coil one can easily and accurately determine the electric field.
Nonlinear force-free modeling of the solar coronal magnetic field
T. Wiegelmann
The coronal magnetic field is an important quantity because the magnetic field dominates the structure of the solar corona. Unfortunately direct measurements of coronal magnetic fields are usually not available. The photospheric magnetic field is measured routinely with vector magnetographs. These photospheric measurements are extrapolated into the solar corona. The extrapolated coronal magnetic field depends on assumptions regarding the coronal plasma, e.g. force-freeness. Force-free means that all non-magnetic forces like pressure gradients and gravity are neglected. This approach is well justified in the solar corona due to the low plasma beta. One has to take care, however, about ambiguities, noise and non-magnetic forces in the photosphere, where the magnetic field vector is measured. Here we review different numerical methods for a nonlinear force-free coronal magnetic field extrapolation: Grad-Rubin codes, upward integration method, MHD-relaxation, optimization and the boundary element approach. We briefly discuss the main features of the different methods and concentrate mainly on recently developed new codes.
Effect of the terrestrial magnetic field on direct-current measurements in underground pipelines
Dzhala, R.M.; Dikmarova, L.P.; Kornienko, V.Yu.
The effect of the secondary field of an underground pipeline, magnetized by the terrestrial magnetic field, on noncontacting measurements of direct current flowing in it is discussed. The systematic errors of three known measurement methods are compared. A method based on the measurement of the difference between the field components parallel to the terrestrial field component orthogonal to the pipline is identified as the most accurate. 5 refs., 3 figs.
Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields
Epstein, Arthur J. (Columbus, OH); Morin, Brian G. (Columbus, OH)
The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors.
Molecular based magnets comprising vanadium tetracyanoethylene complexes for shielding electromagnetic fields
Epstein, A.J.; Morin, B.G.
The invention presents a vanadium tetracyanoethylene solvent complex for electromagnetic field shielding, and a method for blocking low frequency and magnetic fields using these vanadium tetracyanoethylene compositions. The compositions of the invention can be produced at ambient temperature and are light weight, low density and flexible. The materials of the present invention are useful as magnetic shields to block low frequency fields and static fields, and for use in cores in transformers and motors. 21 figs.
Presented by the National High Magnetic Field Laboratory
Weston, Ken
! Cooling holes on the Bitter plates let cold water run through the magnet so it doesn't get too hot. l magnets found in houses. The answers will fit into the crossword puzzle below. ACROSS Where you store milk
Gas Kinetic Study of Magnetic Field Effects on Plasma Plumes
Ebersohn, Frans 1987-
Plasma flow physics in magnetic nozzles must be clearly understood for optimal design of plasma propulsion devices. Toward that end, in this thesis we: i) perform an extensive literature survey of magnetic nozzle physics, ii) assess the validity...
ac magnetic field: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
contract No. DE-AC02-76CH00016. Abstract A common coil design concept for 2-in-1 superconduct- ing Gupta, Ramesh 126 Anisotropy of magnetic emulsions induced by magnetic and...
ac magnetic fields: Topics by E-print Network
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
contract No. DE-AC02-76CH00016. Abstract A common coil design concept for 2-in-1 superconduct- ing Gupta, Ramesh 126 Anisotropy of magnetic emulsions induced by magnetic and...
Magnetic field distribution in the plasma flow generated by a plasma focus discharge
Mitrofanov, K. N., E-mail: email@example.com [Troitsk Institute for Innovaiton and Fusion Research (Russian Federation); Krauz, V. I., E-mail: email@example.com; Myalton, V. V.; Velikhov, E. P.; Vinogradov, V. P.; Vinogradova, Yu. V. [National Research Centre Kurchatov Institute (Russian Federation)
The magnetic field in the plasma jet propagating from the plasma pinch region along the axis of the chamber in a megajoule PF-3 plasma focus facility is studied. The dynamics of plasma with a trapped magnetic flow is analyzed. The spatial sizes of the plasma jet region in which the magnetic field concentrates are determined in the radial and axial directions. The magnetic field configuration in the plasma jet is investigated: the radial distribution of the azimuthal component of the magnetic field inside the jet is determined. It is shown that the magnetic induction vector at a given point in space can change its direction during the plasma flight. Conclusions regarding the symmetry of the plasma flow propagation relative to the chamber axis are drawn.
Approach to fabricating Co nanowire arrays with perpendicular anisotropy: Application of a magnetic field during deposition
Ge, Shihui; Li, Chao; Ma, Xiao; Li, Wei; Xi, Li; Li, C. X.
Cobalt (Co) nanowire arrays were electrodeposited into the pores of polycarbonate membranes. A magnetic field parallel or perpendicular to the membrane plane was applied during deposition to control the wire growth. X-ray diffraction, transmission electron microscopy, and vibrating sample magnetometer were employed to investigate the structure as well as the magnetic properties of the nanowire arrays. The results show that the magnetic field applied during deposition strongly influences the growth of Co nanowires, inducing variations in their crystalline structure and magnetic properties. The sample deposited with the field perpendicular to the membrane plane exhibits a perpendicular magnetic anisotropy with greatly enhanced coercivity and squareness as a result of the preferred growth of Co grains with the c axis perpendicular to the film plane. In contrast, the deposition in a parallel magnetic field forces Co grains to grow with the c axis parallel to the film plane, resulting in in-plane anisotropy. {copyright} 2001 American Institute of Physics.
Temperature measurement of axisymmetric flames under the influence of magnetic field using Talbot interferometry
Agarwal, Shilpi, E-mail: firstname.lastname@example.com, E-mail: email@example.com, E-mail: firstname.lastname@example.com; Kumar, Manoj, E-mail: email@example.com, E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com; Shakher, Chandra, E-mail: firstname.lastname@example.com, E-mail: email@example.com, E-mail: email@example.com [Instrument Design Development Centre, Indian Institute of Technology Delhi, HauzKhas, New Delhi - 110016 (India)
Combustion process control is related with ecological improvement and the problem of energy efficiency; hence it has a wide interest at both economical and scientific levels. Application of a magnetic field is one of the most promising methods of combustion control. The presence of magnetic field induces the changes in flame behavior. The effect of uniform magnetic field developed by permanent magnet is studied by Talbot interferometry using circular gratings. Experimental results show a small decrease in flame temperature and increase in flame dimensions.
Steel characteristics measurement system using Barkhausen jump sum rate and magnetic field intensity and method of using same
Kohn, Gabriel (Omer, IL); Hicho, George (Derwood, MD); Swartzendruber, Lydon (New Carrollton, MD)
A steel hardness measurement system and method of using same are provided for measuring at least one mechanical or magnetic characteristic of a ferromagnetic sample as a function of at least one magnetic characteristic of the sample. A magnetic field generator subjects the sample to a variable external magnetic field. The magnetic field intensity of the magnetic field generated by the magnetic field generating means is measured and a signal sensor is provided for measuring Barkhausen signals from the sample when the sample is subjected to the external magnetic field. A signal processing unit calculates a jump sum rate first moment as a function of the Barkhausen signals measured by the signal sensor and the magnetic field intensity, and for determining the at least one mechanical or magnetic characteristic as a function of the jump sum rate first moment.
Steel characteristics measurement system using Barkhausen jump sum rate and magnetic field intensity and method of using same
Kohn, G.; Hicho, G.; Swartzendruber, L.
A steel hardness measurement system and method of using same are provided for measuring at least one mechanical or magnetic characteristic of a ferromagnetic sample as a function of at least one magnetic characteristic of the sample. A magnetic field generator subjects the sample to a variable external magnetic field. The magnetic field intensity of the magnetic field generated by the magnetic field generating means is measured and a signal sensor is provided for measuring Barkhausen signals from the sample when the sample is subjected to the external magnetic field. A signal processing unit calculates a jump sum rate first moment as a function of the Barkhausen signals measured by the signal sensor and the magnetic field intensity, and for determining the at least one mechanical or magnetic characteristic as a function of the jump sum rate first moment. 7 figs.
NHMFL Breaks the 100 Tesla Barrier Gregory S. Boebinger, National High Magnetic Field Laboratory
Weston, Ken
NHMFL Breaks the 100 Tesla Barrier Gregory S. Boebinger, National High Magnetic Field Laboratory. 109no. 31 12404-12407 On March 22nd 2012, the NHMFL Pulsed Field Facility broke the 100T tesla barrier, setting a world record of 100.75 tesla for a non-destructive magnet. By using advanced
General relativistic simulations of black hole-neutron star mergers: Effects of magnetic fields
Zachariah B. Etienne; Yuk Tung Liu; Vasileios Paschalidis; Stuart L. Shapiro
As a neutron star (NS) is tidally disrupted by a black hole (BH) companion at the end of a BH-NS binary inspiral, its magnetic fields will be stretched and amplified. If sufficiently strong, these magnetic fields may impact the gravitational waveforms, merger evolution and mass of the remnant disk. Formation of highly-collimated magnetic field lines in the disk+spinning BH remnant may launch relativistic jets, providing the engine for a short-hard GRB. We analyze this scenario through fully general relativistic, magnetohydrodynamic (GRMHD) BHNS simulations from inspiral through merger and disk formation. Different initial magnetic field configurations and strengths are chosen for the NS interior for both nonspinning and moderately spinning (a/M=0.75) BHs aligned with the orbital angular momentum. Only strong interior (Bmax~10^17 G) initial magnetic fields in the NS significantly influence merger dynamics, enhancing the remnant disk mass by 100% and 40% in the nonspinning and spinning BH cases, respectively. However, detecting the imprint of even a strong magnetic field may be challenging for Advanced LIGO. Though there is no evidence of mass outflows or magnetic field collimation during the preliminary simulations we have performed, higher resolution, coupled with longer disk evolutions and different initial magnetic field configurations, may be required to definitively assess the possibility of BHNS binaries as short-hard GRB progenitors.
Forecasting change of the magnetic field using core surface flows and ensemble Kalman filtering
Forecasting change of the magnetic field using core surface flows and ensemble Kalman filtering C-based observatories. We therefore present a method using Ensemble Kalman Filtering (EnKF) to produce an optimal (2009), Forecasting change of the magnetic field using core surface flows and ensemble Kalman filtering
Effect of a magnetic field on the two-phonon Raman scattering in C. Faugeras,1
Boyer, Edmond
Effect of a magnetic field on the two-phonon Raman scattering in graphene C. Faugeras,1 P. Kossacki spectrum of graphene (the two-phonon peak near 2700 cm-1) in an external magnetic field applied perpendicular to the graphene crystal plane at liquid helium temperature. A shift to lower frequency
Shell-instability generated waves by low energy electrons on converging magnetic field lines
California at Berkeley, University of
Shell-instability generated waves by low energy electrons on converging magnetic field lines D of observations of such shell type distributions having positive slope in velocity space at low energies, about 10´cre´au (2006), Shell-instability generated waves by low energy electrons on converging magnetic field lines
Plasma transport in a converging magnetic field with applications to helicon plasma thrusters
Choueiri, Edgar
.1, which represents a new design criteria for helicon plasma thrusters. I. Introduction ElectrodelessPlasma transport in a converging magnetic field with applications to helicon plasma thrusters IEPC University, Princeton, New Jersey, 08540, USA Plasma transport in the convergent magnetic field region
Effects of geometry and impurities on quantum rings in magnetic fields RID D-3014-2009
Aichinger, M.; Chin, Siu A.; Krotscheck, E.; Rasanen, E.
We investigate the effects of impurities and changing ring geometry on the energetics of quantum rings under different magnetic field strengths. We show that as the magnetic field and/or the electron number are/is increased, both the quasiperiodic...
Paris-Sud XI, Universit� de
TORSIONAL SHEAR FLOW OF LONG PITCH CHOLESTERIC MESOPHASES IN ELECTRIC AND MAGNETIC FIELDS J. WAHL Physikalisches Institut der Universitat, D44 Munster, Germany Abstract. -- Torsional shear [1] and vertical. -- In vertical electric (or magnetic) fields thin cholesteric layers with homeotropic boun- daries and small
Remote control of ion channels and neurons through magnetic-field heating of nanoparticles
Ferkey, Denise
Remote control of ion channels and neurons through magnetic-field heating of nanoparticles Heng. Here, we show an approach based on radio-frequency magnetic-field heating of nanoparticles to remotely targeted to specific proteins on the plasma membrane of cells expressing TRPV1, and heated by a radio
To be submitted to ApJ Letters Particle acceleration in stressed coronal magnetic fields
Vlahos, Loukas
To be submitted to ApJ Letters Particle acceleration in stressed coronal magnetic fields R an analysis of particle acceleration in a model of the complex magnetic field environment in the flaring solar a relativistic test particle code. It is shown that both ions and electrons are accelerated readily
A field-reversed magnetic configuration and applications of high-temperature FRC plasma
Ryzhkov, S. V., E-mail: email@example.com [Bauman Moscow State Technical University (Russian Federation)
As applied to a tokomak, a magnetic trap for confinement of a plasma with an inverted field or a magnetic field reversed configuration (FRC) is one of the most promising alternatives of the systems with high {beta}. A brief review of the latest data on FRC and potential directions of using such configurations in addition to energy generation in thermonuclear reactors (TNRs) is proposed.
The Effect of Magnetic Field on the Performance of Low-Power Cylindrical Hall Thrusters
The Effect of Magnetic Field on the Performance of Low-Power Cylindrical Hall Thrusters IEPC-2005-099 Presented at the 29th International Electric Propulsion Conference, Princeton University, October 31 for scaling down. The effect of the magnetic field on the discharge characteristics and efficiency of the low
Scattering of Polarized Radiation by Atoms in Magnetic and Electric Fields
Yee Yee Oo; K. N. Nagendra; Sharath Ananthamurthy; G. Ramachandran
The polarization of radiation by scattering on an atom embedded in combined external quadrupole electric and uniform magnetic fields is studied theoretically. Analytic formulae are derived for the scattering phase matrix. Limiting cases of scattering under Zeeman effect, and Hanle effect in weak magnetic fields are discussed.
The Evolution of Cosmic Magnetic Fields: From the Very Early Universe, to Recombination, to the Present
Robi Banerjee; Karsten Jedamzik
(abridged) A detailed examination of the evolution of stochastic magnetic fields between high cosmic temperatures and the present epoch is presented. A simple analytical model matching the results of the 3D MHD simulations allows for the prediction of present day magnetic field correlation lengths and energy. Our conclusions are multi fold. (a) Initial primordial fields with only a small amount of helicity are evolving into maximally helical fields. (b) There exists a correlation between the strength of the magnetic field, B, at the peak of it's spectrum and the location of the peak, given at the present epoch by: B ~ 5x10^{-12} (L/kpc) Gauss, where L is the correlation length determined by the initial magnetic field. (c) Concerning studies of generation of cosmic microwave background (CMBR) anisotropies due to primordial magnetic fields of B~10^{-9} Gauss on ~ 10 Mpc scales, such fields are not only impossible to generate in early causal magnetogenesis scenarios but also seemingly ruled out by distortions of the CMBR spectrum due to magnetic field dissipation on smaller scales and the overproduction of cluster magnetic fields. (d) The most promising detection possibility of CMBR distortions due to primordial magnetic fields may be on much smaller scales at higher multipoles l~10^6 where the signal is predicted to be the strongest. (e) It seems possible that magnetic fields in clusters of galaxies are entirely of primordial origin, without invoking dynamo amplification. Such fields would be of (pre-collapse) strength 10^{-12} - 10^{-11} Gauss with correlation lengths in the kpc range, and would also exist in voids of galaxies.
Dose response of selected ion chambers in applied homogeneous transverse and longitudinal magnetic fields
Reynolds, M. [Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Fallone, B. G. [Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Departments of Oncology and Physics, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Rathee, S. [Department of Medical Physics, Cross Cancer Institute, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada); Department of Oncology, Medical Physics Division, University of Alberta, 11560 University Avenue, Edmonton, Alberta T6G 1Z2 (Canada)
Purpose: The magnetic fields of an integrated MR-Linac system will alter the paths of electrons that produce ions in the ionization chambers. The dose response of selected ion chambers is evaluated in the presence of varying transverse and longitudinal magnetic fields. The investigation is useful in calibration of therapeutic x-ray beams associated with MR-Linac systems. Methods: The Monte Carlo code PENELOPE was used to model the irradiation of NE2571, and PR06C ionization chambers in the presence of a transverse and longitudinal (with respect to the photon beam) magnetic fields of varying magnitude. The long axis of each chamber was simulated both parallel and perpendicular to the incident photon beam for each magnetic field case. The dose deposited in each chamber for each case was compared to the case with zero magnetic field by means of a ratio. The PR06C chamber's response was measured in the presence of a transverse magnetic field with field strengths ranging from 0.0 to 0.2 T to compare to simulated results. Results: The simulations and measured data show that in the presence of a transverse magnetic field there is a considerable dose response (maximum of 11% near 1.0 T in the ion chambers investigated, which depends on the magnitude of magnetic field, and relative orientation of the magnetic field, radiation beam, and ion chamber. Measurements made with the PR06C chamber verify these results in the region of measurement. In contrast, a longitudinal magnetic field produces only a slight increase in dose response (2% at 1.5 T) that rises slowly with increasing magnetic field and is seemingly independent of chamber orientation. Response trends were similar for the two ion chambers and relative orientations considered, but slight variations are present from chamber to chamber. Conclusions: Care must be taken when making ion chamber measurements in a transverse magnetic field. Ion chamber responses vary not only with transverse field strength, but with chamber orientation and type, and can be considerable. Longitudinal magnetic fields influence ion chamber responses relatively little (2% at 1.5 T), and only at field strengths in excess of 1.0 T.
Magnetic-field control of near-field radiative heat transfer and the realization of highly tunable hyperbolic thermal emitters
Moncada-Villa, Edwin; Garcia-Vidal, Francisco J; Garcia-Martin, Antonio; Cuevas, Juan Carlos
We present a comprehensive theoretical study of the magnetic field dependence of the near-field radiative heat transfer (NFRHT) between two parallel plates. We show that when the plates are made of doped semiconductors, the near-field thermal radiation can be severely affected by the application of a static magnetic field. We find that irrespective of its direction, the presence of a magnetic field reduces the radiative heat conductance, and dramatic reductions up to 700% can be found with fields of about 6 T at room temperature. We show that this striking behavior is due to the fact that the magnetic field radically changes the nature of the NFRHT. The field not only affects the electromagnetic surface waves (both plasmons and phonon polaritons) that normally dominate the near-field radiation in doped semiconductors, but it also induces hyperbolic modes that progressively dominate the heat transfer as the field increases. In particular, we show that when the field is perpendicular to the plates, the semicond...
New High Field Magnet for Neutron Scattering at Hahn-Meitner Institute
M Steiner; D A Tennant; P Smeibidl
Abstract. The Berlin Neutron Scattering Center BENSC at the Hahn-Meitner-Institute (HMI) is a user facility for the study of structure and dynamics of condensed matter with neutrons and synchrotron radiation with special emphasis on experiments under extreme conditions. Neutron scattering is uniquely suited to study magnetic properties on a microscopic length scale, because neutrons have comparable wavelengths and, due to their magnetic moment, they interact with the atomic magnetic moments. Magnetic interactions and magnetic phenomena depend on thermodynamic parameters like magnetic field, temperature and pressure. At HMI special efforts are being made to offer outstanding sample environments such as very low temperatures or high magnetic fields or combination of both. For the future a dedicated instrument for neutron scattering at extreme fields is under construction, the Extreme Environment Diffractometer ExED. For this instrument the existing superconducting magnets as well as a future hybrid system can be used. The highest fields, above 30 T will be produced by the planned series-connected hybrid magnet system, designed and constructed in collaboration with the National High Magnetic Field Laboratory, Tallahassee, FL. 1.
Spin-lattice dynamics simulation of external field effect on magnetic order of ferromagnetic iron
Chui, C. P. [Department of Electronic and Information Engineering, the Hong Kong Polytechnic University (Hong Kong)] [Department of Electronic and Information Engineering, the Hong Kong Polytechnic University (Hong Kong); Zhou, Yan, E-mail: firstname.lastname@example.com [Department of Physics, the University of Hong Kong (Hong Kong)] [Department of Physics, the University of Hong Kong (Hong Kong)
Modeling of field-induced magnetization in ferromagnetic materials has been an active topic in the last dozen years, yet a dynamic treatment of distance-dependent exchange integral has been lacking. In view of that, we employ spin-lattice dynamics (SLD) simulations to study the external field effect on magnetic order of ferromagnetic iron. Our results show that an external field can increase the inflection point of the temperature. Also the model provides a better description of the effect of spin correlation in response to an external field than the mean-field theory. An external field has a more prominent effect on the long range magnetic order than on the short range counterpart. Furthermore, an external field allows the magnon dispersion curves and the uniform precession modes to exhibit magnetic order variation from their temperature dependence.
$?$ mesons in strong abelian magnetic field in SU(3) lattice gauge theory
E. V. Luschevskaya; O. A. Kochetkov; O. V. Larina; O. V. Teryaev
We explore the masses of neutral and charged $\\rho$ mesons in strong abelian magnetic field in $SU(3)$ gluodynamics. The behaviour of the ground state energy of these particles in the external magnetic field depends on its spin projection $s_z$ on the axis of external magnetic field. The masses of $\\rho^0$ meson with $s_z=\\pm 1$ increase with the field. The masses of $\\rho^{\\pm}$ mesons with zero spin also grow with the magnetic field. The ground state energies of $\\rho^{-}$ meson with $s_z=-1$ and $\\rho^{+}$ meson with $s_z=+1$ diminish as a function of the field, while the energies of $\\rho^{+}$ meson with $s_z=-1$ and $\\rho^{-}$ meson with $s_z=+1$ rise with the field value.
Effect of trapping in a degenerate plasma in the presence of a quantizing magnetic field
Shah, H. A.; Iqbal, M. J.; Qureshi, M. N. S. [Department of Physics, GC University, Lahore 54000 (Pakistan); Tsintsadze, N. [Department of Physics, GC University, Lahore 54000 (Pakistan); Institute of Physics, Tbilisi 0177 (Georgia); Masood, W. [Theoretical Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan)
Effect of trapping as a microscopic phenomenon in a degenerate plasma is investigated in the presence of a quantizing magnetic field. The plasma comprises degenerate electrons and non-degenerate ions. The presence of the quantizing magnetic field is discussed briefly and the effect of trapping is investigated by using the Fermi-Dirac distribution function. The linear dispersion relation for ion acoustic wave is derived in the presence of the quantizing magnetic field and its influence on the propagation characteristics of the linear ion acoustic wave is discussed. Subsequently, fully nonlinear equations for ion acoustic waves are used to obtain the Sagdeev potential and the investigation of solitary structures. The formation of solitary structures is studied both for fully and partially degenerate plasmas in the presence of a quantizing magnetic field. Both compressive and rarefactive solitons are obtained for different conditions of temperature and magnetic field.
The ionization rate under a general magnetic field for microwave breakdown
Wang, Huihui, E-mail: firstname.lastname@example.com; Meng, Lin; Liu, Dagang; Liu, Laqun [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)
The ionization rate under an extra magnetic field is studied by theory and particle-in-cell/Monte Carlo Collision simulations. The result shows that a magnetic field always decreases the ionization rate if ?(3)???{sub m}, while it may increase the ionization rate if ?(3)??>??{sub m}. The effect of the magnetic field on the ionization rate fades away when the angle between the magnetic field and the electric filed approaches to zero. Furthermore, the peak ionization rate among different magnetic fields is almost independent of ?. This peak ionization rate is in direct proportion to the gas pressure in the low pressure region, while it is about in inverse proportion to the gas pressure in the high pressure region.
Conlon, Paul A.; Gallagher, Peter T. [Astrophysics Research Group, School of Physics, Trinity College Dublin, Dublin 2 (Ireland)
The three-dimensional magnetic topology of a solar active region (NOAA 10956) was reconstructed using a linear force-free field extrapolation constrained using the twin perspectives of STEREO. A set of coronal field configurations was initially generated from extrapolations of the photospheric magnetic field observed by the Michelson Doppler Imager on SOHO. Using an EUV intensity-based cost function, the extrapolated field lines that were most consistent with 171 A passband images from the Extreme UltraViolet Imager on STEREO were identified. This facilitated quantitative constraints to be placed on the twist ({alpha}) of the extrapolated field lines, where {nabla} x B = {alpha}B. Using the constrained values of {alpha}, the evolution in time of twist, connectivity, and magnetic energy were then studied. A flux emergence event was found to result in significant changes in the magnetic topology and total magnetic energy of the region.
Passive Superconducting Flux Conservers for Rotating-Magnetic-Field-Driven Field-Reversed Configurations
E. Oz, C.E. Myers, M.R. Edwards, B. Berlinger, A. Brooks, and S.A. Cohen
The Princeton Field-Reversed Configuration (PFRC) experiment employs an odd-parity rotating magnetic field (RMFo) current drive and plasma heating system to form and sustain high-? plasmas. For radial confinement, an array of coaxial, internal, passive, flux-conserving (FC) rings applies magnetic pressure to the plasma while still allowing radio-frequency RMFo from external coils to reach the plasma. The 3 ms pulse duration of the present experiment is limited by the skin time (?fc) of its room-temperature copper FC rings. To explore plasma phenomena with longer characteristic times, the pulse duration of the next-generation PFRC-2 device will exceed 100 ms, necessitating FC rings with (?fc > 300 ms. In this paper we review the physics of internal, discrete, passive FCs and describe the evolution of the PFRC's FC array. We then detail new experiments that have produced higher performance FC rings that contain embedded high-temperature superconducting (HTS) tapes. Several HTS tape winding configurations have been studied and a wide range of extended skin times, from 0.4 s to over 103 s, has been achieved. The new FC rings must carry up to 3 kA of current to balance the expected PFRC-2 plasma pressure, so the dependence of the HTS-FC critical current on the winding configuration and temperature was also studied. From these experiments, the key HTS-FC design considerations have been identified and HTS-FC rings with the desired performance characteristics have been produced.
Bernal, Cristian G.; Page, Dany; Lee, William H., E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com [Departamento de Astrofisica Teorica, Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Mexico, D.F. 04510 (Mexico)
We present magnetohydrodynamic numerical simulations of the late post-supernova hypercritical accretion to understand its effect on the magnetic field of the newborn neutron star. We consider as an example the case of a magnetic field loop protruding from the star's surface. The accreting matter is assumed to be non-magnetized, and, due to the high accretion rate, matter pressure dominates over magnetic pressure. We find that an accretion envelope develops very rapidly, and once it becomes convectively stable, the magnetic field is easily buried and pushed into the newly forming neutron star crust. However, for low enough accretion rates the accretion envelope remains convective for an extended period of time and only partial submergence of the magnetic field occurs due to a residual field that is maintained at the interface between the forming crust and the convective envelope. In this latter case, the outcome should be a weakly magnetized neutron star with a likely complicated field geometry. In our simulations we find the transition from total to partial submergence to occur around M-dot {approx}10 M{sub sun} yr{sup -1}. Back-diffusion of the submerged magnetic field toward the surface, and the resulting growth of the dipolar component, may result in a delayed switch-on of a pulsar on timescales of centuries to millennia.
The Magnificent Seven: Magnetic fields and surface temperature distributions
F. Haberl
Presently seven nearby radio-quiet isolated neutron stars discovered in ROSAT data and characterized by thermal X-ray spectra are known. They exhibit very similar properties and despite intensive searches their number remained constant since 2001 which led to their name ``The Magnificent Seven''. Five of the stars exhibit pulsations in their X-ray flux with periods in the range of 3.4 s to 11.4 s. XMM-Newton observations revealed broad absorption lines in the X-ray spectra which are interpreted as cyclotron resonance absorption lines by protons or heavy ions and / or atomic transitions shifted to X-ray energies by strong magnetic fields of the order of 10^13 G. New XMM-Newton observations indicate more complex X-ray spectra with multiple absorption lines. Pulse-phase spectroscopy of the best studied pulsars RX J0720.4-3125 and RBS 1223 reveals variations in derived emission temperature and absorption line depth with pulse phase. Moreover, RX J0720.4-3125 shows long-term spectral changes which are interpreted as due to free precession of the neutron star. Modeling of the pulse profiles of RX J0720.4-3125 and RBS 1223 provides information about the surface temperature distribution of the neutron stars indicating hot polar caps which have different temperatures, different sizes and are probably not located in antipodal positions.
Gamma-ray burst spectrum with decaying magnetic field
Zhao, Xiaohong; Bai, Jinming [Yunnan Observatory, Chinese Academy of Sciences, P.O. Box 110, 650011 Kunming (China); Li, Zhuo [Department of Astronomy and Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Liu, Xuewen; Zhang, Bin-bin; M�sz�ros, Peter, E-mail: email@example.com, E-mail: email@example.com [Department of Astronomy and Astrophysics and Department of Physics, The Pennsylvania State University, University Park, PA 16802 (United States)
In the internal shock model for gamma-ray bursts (GRBs), the synchrotron spectrum from the fast cooling electrons in a homogeneous downstream magnetic field (MF) is too soft to produce the low-energy slope of GRB spectra. However, the MF may decay downstream with distance from the shock front. Here we show that the synchrotron spectrum becomes harder if electrons undergo synchrotron and inverse-Compton cooling in a decaying MF. To reconcile this with the typical GRB spectrum with low-energy slope ?F {sub ?}??, the postshock MF decay time must be comparable to the cooling time of the bulk electrons (corresponding to a MF decaying length typically of ?10{sup 5} skin depths); that the inverse-Compton cooling should dominate synchrotron cooling after the MF decay time; and/or that the MF decays with comoving time roughly as B?t {sup �1.5}. An internal shock synchrotron model with a decaying MF can account for the majority of GRBs with low-energy slopes not harder than ?{sup 4/3}.
Asymmetric neutrino production in magnetized proto-neutron stars in fully relativistic mean-field approach
Maruyama, Tomoyuki [College of Bioresource Sciences, Nihon University, Fujisawa 252-8510 (Japan); Kajino, Toshitaka; Hidaka, Jun; Takiwaki, Tomoya [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Yasutake, Nobutoshi [Department of Physics, Chiba Institute of Technology, Narashino 275-0023 (Japan); Kuroda, Takami [Department of Physics, University of Basel, CH-4056 Basel (Switzerland); Cheoun, Myung-Ki [Department of Physics, Soongsil University, Seoul, 156-743 (Korea, Republic of); Ryu, Chung-Yeol [General Education Curriculum Center, Hanyang University, Seoul, 133-791 (Korea, Republic of); Mathews, Grant J. [Center of Astrophysics, Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States)
We calculate the neutrino production cross-section in the proto-neutron-star matter under a strong magnetic field in the relativistic mean-field approach. We introduce a new parameter-set which can reproduce the 1.96 solar mass neutron star. We find that the production process increases emitted neutrinos along the direction parallel to the magnetic field and decrease those along its opposite direction. It means that resultant asymmetry due to the neutrino absorption and scattering process in the magnetic field becomes larger by the addition of the neutrino production process.
New measurements of magnetic fields of roAp stars with FORS1 at the VLT
S. Hubrig; T. Szeifert; M. Schoeller; G. Mathys; D. W. Kurtz
Magnetic fields play a key role in the pulsations of rapidly oscillating Ap (roAp) stars since they are a necessary ingredient of all pulsation excitation mechanisms proposed so far. This implies that the proper understanding of the seismological behaviour of the roAp stars requires knowledge of their magnetic fields. However, the magnetic fields of the roAp stars are not well studied. Here we present new results of measurements of the mean longitudinal field of 14 roAp stars obtained from low resolution spectropolarimetry with FORS1 at the VLT.
A loss-based, magnetic field sensor implemented in a ferrofluid infiltrated microstructured polymer optical fiber
Candiani, A. [Foundation for Research and Technology-Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), Heraklion 70013 Greece (Greece); Department of Information Engineering (DII), University of Parma, Parma 43124 (Italy); Argyros, A.; Leon-Saval, S. G.; Lwin, R. [Institute of Photonics and Optical Science (IPOS), School of Physics, The University of Sydney, Sydney (Australia); Selleri, S. [Department of Information Engineering (DII), University of Parma, Parma 43124 (Italy); Pissadakis, S., E-mail: firstname.lastname@example.com [Foundation for Research and Technology-Hellas (FORTH), Institute of Electronic Structure and Laser (IESL), Heraklion 70013 Greece (Greece)
We report an in-fiber magnetic field sensor based on magneto-driven optical loss effects, while being implemented in a ferrofluid infiltrated microstructured polymer optical fiber. We demonstrate that magnetic field flux changes up to 2000 gauss can be detected when the magnetic field is applied perpendicular to the fiber axis. In addition, the sensor exhibits high polarization sensitivity for the interrogated wavelengths, providing the possibility of both field flux and direction measurements. The underlying physical and guidance mechanisms of this sensing transduction are further investigated using spectrophotometric, light scattering measurements, and numerical simulations, suggesting photonic Hall effect as the dominant physical, transducing mechanism.
Primary beam steering due to field leakage from superconducting SHMS magnets
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Moore, M.H.; Waidyawansa, B.P.; Covrig, S.; Carlini, R.; Benesch, J.
Simulations of the magnetic fields from the Super High Momentum Spectrometer in Hall C at Thomas Jefferson National Accelerator Facility show significant field leakage into the region of the primary beam line between the target and the beam dump. Without mitigation, these remnant fields will steer the unscattered beam enough to limit beam operations at small scattering angles. Presented here are magnetic field simulations of the spectrometer magnets and a solution using optimal placement of a minimal amount of shielding iron around the beam line.
Measurements of electric and magnetic fields in the Waianae, Hawaii area
Mantiply, E.D.
During November 27--30, 1990, the US Environmental Protection Agency (EPA) conducted a measurement survey of electric and magnetic field levels along the southwest coast of Oahu, Hawaii. These measurements were requested by the State of Hawaii to determine the levels of radiofrequency (RF) electric and magnetic fields near Naval radio transmitters at Lualualei. The objective was to determine maximum fields in residential areas. This report documents the measurement results. Also, a few measurements were made of extremely-low-frequency (ELF) electric and magnetic fields at 60 hertz, the frequency used for electrical power.
Primary Beam Steering Due to Field Leakage from Superconducting SHMS Magnets
Michael H. Moore; Buddhini P. Waidyawansa; Silviu Covrig; Roger Carlini; Jay Benesch
Simulations of the magnetic fields from the Super High Momentum Spectrometer in Hall C at Thomas Jefferson National Accelerator Facility show significant field leakage into the region of the primary beam line between the target and the beam dump. Without mitigation, these remnant fields will steer the unscattered beam enough to limit beam operations at small scattering angles. Presented here are magnetic field simulations of the spectrometer magnets and a solution using optimal placement of a minimal amount of shielding iron around the beam line.
The role of renewable energy in climate stabilization: results from the EMF 27 scenarios
Luderer, Gunnar; Krey, Volker; Calvin, Katherine V.; Merrick, James; Mima, Silvana; Pietzcker, Robert; Van Vliet, Jasper; Wada, Kenichi
This paper uses the EMF27 scenarios to explore the role of renewable energy (RE) in climate change mitigation. Currently RE supplies almost 20 % of global electricity demand. Almost all EMF27 mitigation scenarios show a strong increase in renewable power production, with a substantial ramp-up of wind and solar power deployment. In many scenarios, renewables are the most important long-term mitigation option for power supply. Wind energy is competitive even without climate policy, whereas the prospects of solar photovoltaics (PV) are highly contingent on the ambitiousness of climate policy. Bioenergy is an important and versatile energy carrier; however�with the exception of low temperature heat�there is less scope for renewables other than biomass for non-electric energy supply. Despite the important role of wind and solar power in climate change mitigation scenarios with full technology availability, limiting their deployment has a relatively small effect on mitigation costs, if nuclear and carbon capture and storage (CCS)�which can serve as substitutes in low-carbon power supply�are available. Limited bioenergy availability in combination with limited wind and solar power by contrast, results in a more substantial increase in mitigation costs. While a number of robust insights emerge, the results on renewable energy deployment levels vary considerably across the models. An in-depth analysis of a subset of EMF27 reveals substantial differences in modeling approaches and parameter assumptions. To a certain degree, differences in model results can be attributed to different assumptions about technology costs, resource potentials and systems integration.
Axion production and CMB spectral distortion in cosmological tangled magnetic field
Damian Ejlli
Axion production due to photon-axion mixing in tangled magnetic field(s) prior to recombination epoch and magnetic field damping can generate cosmic microwave background (CMB) spectral distortions. In particular, contribution of both processes to CMB $\\mu$ distortion in the case of resonant photon-axion mixing is studied. Assuming that magnetic field power spectrum is approximated by a power law $P_B(k)\\propto k^n$ with spectral index $n$, it is shown that for magnetic field cut-off scales $172.5$ pc $\\leq \\lambda_B\\leq 4\\times 10^3$ pc, axion contribution to CMB $\\mu$ distortion is subdominant in comparison with magnetic field damping in the cosmological plasma. Using COBE upper limit on $\\mu$ and for magnetic field scale $\\lambda_B\\simeq 415$ pc, weaker limit in comparison with other studies on the magnetic field strength ($B_0\\leq 8.5\\times 10^{-8}$ G) up to a factor 10 for the DFSZ axion model and axion mass $m_a\\geq 2.6\\times 10^{-6}$ eV is found. A forecast for the expected sensitivity of PIXIE/PRISM on $\\mu$ is also presented.
Axion production and CMB spectral distortion in cosmological tangled magnetic field
Ejlli, Damian
Axion production due to photon-axion mixing in tangled magnetic field(s) prior to recombination epoch and magnetic field damping can generate cosmic microwave background (CMB) spectral distortions. In particular, contribution of both processes to CMB $\\mu$ distortion in the case of resonant photon-axion mixing is studied. Assuming that magnetic field power spectrum is approximated by a power law $P_B(k)\\propto k^n$ with spectral index $n$, it is shown that for magnetic field cut-off scales $172.5$ pc $\\leq \\lambda_B\\leq 4\\times 10^3$ pc, axion contribution to CMB $\\mu$ distortion is subdominant in comparison with magnetic field damping in the cosmological plasma. Using COBE upper limit on $\\mu$ and for magnetic field scale $\\lambda_B\\simeq 415$ pc, weaker limit in comparison with other studies on the magnetic field strength ($B_0\\leq 8.5\\times 10^{-8}$ G) up to a factor 10 for the DFSZ axion model and axion mass $m_a\\geq 2.6\\times 10^{-6}$ eV is found. A forecast for the expected sensitivity of PIXIE/PRISM on...
Decoupling between torsion and magnetic fields in bouncing cosmology and galactic dynamo seeds
Garcia de Andrade; Angel Ferrandez
Recently Salim et al [JCAP (2007)], have shown that galactic dynamo seeds can be possibly attainable in bouncing cosmological models with QED Lagrangeans. In this paper we generalise their result by include torsion of spacetime in bouncing cosmology. It is shown that by considering a semi-minimal photon-torsion coupling and a Lagrangean of the type $RF^{2}$ it is possible to find a fast decoupling between magnetic and torsion fields in the contracting phases of the universe. Besides torsion field decays as $K\\sim{a^{2/3}}$ while the magnetic field grows as $B\\sim{a^{-5.5}}$ thus explaining the fast decoupling between the two fields. It is expected that at some point of the contracting phase the amplification of the magnetic field may give rise to a enough strong magnetic field to seed a galactic dynamo.
Production of large volume, strongly magnetized laser-produced plasmas by use of pulsed external magnetic fields
Albertazzi, B. [LULI, Ecole Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); INRS-EMT, Varennes, Quebec J3X 1S2 (Canada); Beard, J.; Billette, J.; Portugall, O. [LNCMI, UPR 3228, CNRS-UFJ-UPS-INSA, 31400 Toulouse (France); Ciardi, A. [LERMA, Observatoire de Paris, Ecole Normale Superieure, Universite Pierre et Marie Curie, CNRS UMR 8112, Paris (France); Vinci, T.; Albrecht, J.; Chen, S. N.; Da Silva, D.; Hirardin, B.; Nakatsutsumi, M.; Romagnagni, L.; Simond, S.; Veuillot, E.; Fuchs, J. [LULI, Ecole Polytechnique, CNRS, CEA, UPMC, 91128 Palaiseau (France); Burris-Mog, T.; Dittrich, S.; Herrmannsdoerfer, T.; Kroll, F.; Nitsche, S. [Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden (Germany); and others
The production of strongly magnetized laser plasmas, of interest for laboratory astrophysics and inertial confinement fusion studies, is presented. This is achieved by coupling a 16 kV pulse-power system. This is achieved by coupling a 16 kV pulse-power system, which generates a magnetic field by means of a split coil, with the ELFIE laser facility at Ecole Polytechnique. In order to influence the plasma dynamics in a significant manner, the system can generate, repetitively and without debris, high amplitude magnetic fields (40 T) in a manner compatible with a high-energy laser environment. A description of the system and preliminary results demonstrating the possibility to magnetically collimate plasma jets are given.
Influence of direct URCA processes in a strong magnetic field on dynamics of collapsing star envelope
A. A. Gvozdev; I. S. Ognev
Direct URCA processes in a collapsing star envelope with a strong magnetic field are investigated. It is shown that in the toroidal magnetic field these processes can develope a torque which quickly unwinds an envelope. A general expression for a force density along the field direction is obtained. An influence of the neutrino unwinding effect on a dynamics of the collapsar envelope is discussed and numerically estimated.
Measuring Magnetic Fields Near and Far with the SKA via the Zeeman Effect
Robishaw, Timothy; Surcis, Gabriele; Vlemmings, Wouter; Richards, A M S; Etoka, Sandra; Bourke, Tyler; Fish, Vincent; Gray, Malcolm; Imai, Hiroshi; Kramer, Busaba; McBride, James; Momjian, Emmanuel; Sarma, Anuj; Zijlstra, Albert
The measurement of Zeeman splitting in spectral lines---both in emission and absorption---can provide direct estimates of the magnetic field strength and direction in atomic and molecular clouds, both in our own Milky Way and in external galaxies. This method will probe the magnetic field in the warm and cold neutral components of the interstellar medium, providing a complement to the extensive SKA Faraday studies planning to probe the field in the ionized components.
Electron-Positron Pair Production by an Electron in a Magnetic Field Near the Process Threshold
O. P. Novak; R. I. Kholodov; P. I. Fomin
The electron-positron pair production by an electron in a strong magnetic field near the process threshold is considered. The process is shown to be more probable if the spin of the initial electron is oriented along the field. In this case, the probability of the process is $\\sim10^{13} s^{-1}$ when the magnetic field strength is $H=4\\cdot 10^{12}$ G.
Influence of high magnetic field on the luminescence of Eu{sup 3+}-doped glass ceramics
Jiang, Wei; Chen, Weibo; Chen, Ping; Xu, Beibei; Zheng, Shuhong; Guo, Qiangbing; Liu, Xiaofeng, E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027 (China); Zhang, Junpei; Han, Junbo [Wuhan National High Magnetic field Center, Huazhong University of Science and Technology, Wuhan, Hubei 430074 (China); Qiu, Jianrong, E-mail: email@example.com, E-mail: firstname.lastname@example.com [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou, Zhejiang 310027 (China); State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou, Guangdong 510640 (China)
Rare earth (RE) doped materials have been widely exploited as the intriguing electronic configuration of RE ions offers diverse functionalities from optics to magnetism. However, the coupling of magnetism with photoluminescence (PL) in such materials has been rarely reported in spite of its fundamental significance. In the present paper, the effect of high pulsed magnetic field on the photoluminescence intensity of Eu{sup 3+}-doped nano-glass-ceramics has been investigated. In our experiment, Eu-doped oxyfluoride glass and glass ceramic were prepared by the conventional melt-quenching process and controlled heat treatment. The results demonstrate that the integrated PL intensity of Eu{sup 3+} decreases with the enhancement of magnetic field, which can be interpreted in terms of cooperation effect of Zeeman splitting and magnetic field induced change in site symmetry. Furthermore, as a result of Zeeman splitting, both blue and red shift in the emission peaks of Eu{sup 3+} can be observed, and this effect becomes more prominent with the increase of magnetic field. Possible mechanisms associated with the observed magneto-optical behaviors are suggested. The results of the present paper may open a new gate for modulation of luminescence by magnetic field and remote optical detection of magnetic field.
Ground Magnetics At San Francisco Volcanic Field Area (Warpinski...
Area Exploration Technique Ground Magnetics Activity Date Usefulness not indicated DOE-funding Unknown Notes Northern Arizona University has re-assessed the existing exploration...
Photo of the Week: Controlling Chaos with Magnetic Fields | Department...
Broader source: Energy.gov (indexed) [DOE]
Favorites from Photo of the Week This 1978 photo shows two workers inside the Mirror Fusion Test Facility, a magnetic confinement fusion device designed and built at Lawrence...
Structure, dynamical impact and origin of magnetic fields in nearby galaxies in the SKA era
Beck, Rainer; Colafrancesco, Sergio; Dettmar, Ralf-J�rgen; Ferri�re, Katia; Fletcher, Andrew; Heald, George; Heesen, Volker; Horellou, Cathy; Krause, Marita; Lou, Yu-Qing; Mao, Sui Ann; Paladino, Rosita; Schinnerer, Eva; Sokoloff, Dmitry; Stil, Jeroen; Tabatabaei, Fatemeh
Magnetic fields are an important ingredient of the interstellar medium (ISM). Besides their importance for star formation, they govern the transport of cosmic rays, relevant to the launch and regulation of galactic outflows and winds, which in turn are pivotal in shaping the structure of halo magnetic fields. Mapping the small-scale structure of interstellar magnetic fields in many nearby galaxies is crucial to understand the interaction between gas and magnetic fields, in particular how gas flows are affected. Elucidation of the magnetic role in, e.g., triggering star formation, forming and stabilising spiral arms, driving outflows, gas heating by reconnection and magnetising the intergalactic medium has the potential to revolutionise our physical picture of the ISM and galaxy evolution in general. Radio polarisation observations in the very nearest galaxies at high frequencies (>= 3 GHz) and with high spatial resolution (<= 5") hold the key here. The galaxy survey with SKA1 that we propose will also be a...
The mitigating effect of magnetic fields on Rayleigh-Taylor unstable inertial confinement fusion plasmas
Srinivasan, Bhuvana; Tang, Xian-Zhu [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
Rayleigh-Taylor (RT) instabilities at interfaces of disparate mass densities have long been known to generate magnetic fields during inertial confinement fusion implosions. An externally applied magnetic field can also be efficiently amplified by RT instabilities. The focus here is on magnetic field generation and amplification at the gas-ice interface which is RT unstable during the deceleration phase of the implosion. RT instabilities lead to undesirable mix of hot and cold plasmas which enhances thermal energy loss and tends to produce a more massive warm-spot instead of a hot-spot. Two mechanisms are shown here to mitigate the thermal energy loss from the hot-spot. The first mechanism is the reduction of electron thermal conductivity with interface-aligned magnetic fields. This can occur through self-generated magnetic fields via the Biermann battery effect as well as through externally applied magnetic fields that undergo an exponential growth via the stretch-and-fold magnetohydrodynamic dynamo. Self-generated magnetic fields during RT evolution can result in a factor of 2?10 decrease in the electron thermal conductivity at the gas-ice interface, while externally applied magnetic fields that are compressed to 6�1000 T at the onset of deceleration (corresponding to pre-implosion external fields of 0.06�10 T) could result in a factor of 2�500 reduction in electron thermal conductivity at the gas-ice interface. The second mechanism to mitigate thermal energy loss from the hot-spot is to decrease the interface mixing area between the hot and cold plasmas. This is achieved through large external magnetic fields of 1000 T at the onset of deceleration which damp short-wavelength RT modes and long-wavelength Kelvin-Helmholtz modes thus significantly slowing the RT growth and reducing mix.
Distortion-free magnetic resonance imaging in the zero-field limit
Kelso, Nathan; Lee, Seung-Kyun; Bouchard, Louis-S.; Demas, Vasiliki; Muck, Michael; Pines, Alexander; Clarke, John
MRI is a powerful technique for clinical diagnosis and materials characterization. Images are acquired in a homogeneous static magnetic field much higher than the fields generated across the field of view by the spatially encoding field gradients. Without such a high field, the concomitant components of the field gradient dictated by Maxwell's equations lead to severe distortions that make imaging impossible with conventional MRI encoding. In this paper, we present a distortion-free image of a phantom acquired with a fundamentally different methodology in which the applied static field approaches zero. Our technique involves encoding with pulses of uniform and gradient field, and acquiring the magnetic field signals with a SQUID. The method can be extended to weak ambient fields, potentially enabling imaging in the Earth's field without cancellation coils or shielding. Other potential applications include quantum information processing and fundamental studies of long-range ferromagnetic interactions.
Observation of magnetic field lines in the vicinity of a superconductor with the naked eye
Yoshihiko Saito
Meissner effect and pinning effect are clearly observed with the naked eye. A GdBaCuO high-temperature superconductor (HTS) disk fabricated by Nippon Steel Corporation, a 100mm cubic NdFeB sintered magnet, and iron wires coated by colored are used. When the HTS is put in the magnetic field of the magnet, it can be observed by the wires that the magnetic field lines are excluded from the superconductor (Meissner effect) as well as are pinned in the superconductor (pinning effect).
Relationship of sunspot magnetic fields to umbral sizes in return flux theory
Osherovich, V.A.; Garcia, H.A.
The relationship between the relative size of a sunspot umbra and the relative magnitude of the magnetic field at the outer edge of the penumbra is studied. It is found that the sunspot magnetic topology is composed of two magnetic regimes, one consisting of open field lines emerging from the core and extending to infinity, and the second consisting of lines returning to the photosphere. The relative quantity of the return magnetic flux is closely associated with the size of the umbra relative to the penumbra. 31 references.
Scripta Materialia 52 (2004) 461-466 Effect of 30 Tesla Magnetic Field on Transformations in a
Cambridge, University of
Scripta Materialia 52 (2004) 461-466 Effect of 30 Tesla Magnetic Field on Transformations transforms to ferrite. Thus, a 30 Tesla magnetic field can raise transformation temperatures by ~90°C during
Radiation from Small-Scale Magnetic Field Turbulence: Implications for Gamma-Ray Bursts and Laboratory Astrophysical Plasmas
Reynolds, Sarah J
Relativistic charged particles moving within regions of small-scale magnetic field turbulence radiate as they undergo transverse accelerations reflective of the magnetic field variation along the particle's path. For a ...
The effect of magnetic field on bistability in 1D photonic crystal doped by magnetized plasma and coupled nonlinear defects
Mehdian, H.; Mohammadzahery, Z.; Hasanbeigi, A. [Department of Physics and Institute for Plasma Research, Kharazmi University, 49 Dr Mofatteh Avenue, Tehran 15614 (Iran, Islamic Republic of)] [Department of Physics and Institute for Plasma Research, Kharazmi University, 49 Dr Mofatteh Avenue, Tehran 15614 (Iran, Islamic Republic of)
In this work, we study the defect mode and bistability behavior of 1-D photonic band gap structure with magnetized plasma and coupled nonlinear defects. The transfer matrix method has been employed to investigate the magnetic field effect on defect mode frequency and bistability threshold. The obtained results show that the frequency of defect mode and bistability threshold can be altered, without changing the structure of the photonic multilayer. Therefore, the bistability behavior of the subjected structure in the presence of magnetized plasma can be utilized in manufacturing wide frequency range devices.
Largeamplitude compressive "sawtooth" magnetic field oscillations in the Martian magnetosphere
California at Berkeley, University of
, including a bow shock, a magne- tosheath, an ionosphere, and an extended wake region consisting of two and dynamic and thermal pressure from various ion species in the Martian magne- tosphere differ greatly from order of altitude) a bow shock, a magnetic pileup boundary (MPB) where magnetic pressure increases
Real-Time Magnetic Field Pitch Angle Estimation with a Motional Stark Effect Diagnostic Using Kalman Filtering
Real-Time Magnetic Field Pitch Angle Estimation with a Motional Stark Effect Diagnostic Using Kalman Filtering
Observations of Multi-Resonance Effect in ELM Control with Magnetic Perturbation Fields on the JET Tokamak
Observations of Multi-Resonance Effect in ELM Control with Magnetic Perturbation Fields on the JET Tokamak
Magnetic field instability in a neutron star driven by the electroweak electron-nucleon interaction versus the chiral magnetic effect
Maxim Dvornikov; Victor B. Semikoz
We show that the Standard Model electroweak interaction of ultrarelativistic electrons with nucleons ($eN$ interaction) in a neutron star (NS) permeated by a seed large-scale helical magnetic field provides its growth up to $\\gtrsim 10^{15}\\thinspace\\text{G}$ during a time comparable with the ages of young magnetars $\\sim 10^4\\thinspace\\text{yr}$. The magnetic field instability originates from the parity violation in the $eN$ interaction entering the generalized Dirac equation for right and left massless electrons in an external uniform magnetic field. We calculate the averaged electric current given by the solution of the modified Dirac equation containing an extra current for right and left electrons (positrons), which turns out to be directed along the magnetic field. Such current includes both a changing chiral imbalance of electrons and the $eN$ potential given by a constant neutron density in NS. Then we derive the system of the kinetic equations for the chiral imbalance and the magnetic helicity which accounts for the $eN$ interaction. By solving this system, we show that a sizable chiral imbalance arising in a neutron protostar due to the Urca-process $e^-_\\mathrm{L} + p\\to N + \
The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Magnetohydrodynamics Simulation Module for the Global Solar Corona
Hayashi, Keiji; Liu, Yang; Bobra, Monica G; Sun, Xudong D; Norton, Aimee A
Time-dependent three-dimensional magnetohydrodynamics (MHD) simulation modules are implemented at the Joint Science Operation Center (JSOC) of Solar Dynamics Observatory (SDO). The modules regularly produce three-dimensional data of the time-relaxed minimum-energy state of the solar corona using global solar-surface magnetic-field maps created from Helioseismic Magnetic Imager (HMI) full-disk magnetogram data. With the assumption of polytropic gas with specific heat ratio of 1.05, three types of simulation products are currently generated: i) simulation data with medium spatial resolution using the definitive calibrated synoptic map of the magnetic field with a cadence of one Carrington rotation, ii) data with low spatial resolution using the definitive version of the synchronic frame format of the magnetic field, with a cadence of one day, and iii) low-resolution data using near-real-time (NRT) synchronic format of the magnetic field on daily basis. The MHD data available in the JSOC database are three-dimen...
Zeeman tomography of magnetic white dwarfs, I. Reconstruction of the field geometry from synthetic spectra
F. Euchner; S. Jordan; K. Beuermann; B. T. Gaensicke; F. V. Hessmann
We have computed optical Zeeman spectra of magnetic white dwarfs for field strengths between 10 and 200MG and effective temperatures between 8000 and 40000K. They form a database containing 20628 sets of flux and circular polarization spectra. A least-squares optimization code based on an evolutionary strategy can recover relatively complex magnetic field topologies from phase-resolved synthetic Zeeman spectra of rotating magnetic white dwarfs. We consider dipole and quadrupole components which are non-aligned and shifted off-centre. The model geometries include stars with a single high-field spot and with two spots separated by approx. 90 degrees. The accuracy of the recovered field structure increases with the signal-to-noise ratio of the input spectra and is significantly improved if circular polarization spectra are included in addition to flux spectra. We discuss the strategies proposed so far to unravel the field geometries of magnetic white dwarfs.
Wave breaking phenomenon of lower-hybrid oscillations induced by a background inhomogeneous magnetic field
Maity, Chandan; Chakrabarti, Nikhil [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064 (India); Sengupta, Sudip [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India)
In a fluid description, we study space-time evolution of lower hybrid modes in a cold quasi-neutral homogeneous plasma in presence of a background inhomogeneous magnetic field. Within a linear analysis, a dispersion relation with inhomogeneous magnetic field shows 'phase mixing' of such oscillations. A manifestation of 'phase mixing' is shown in 'mode coupling.' By using Lagrangian variables, an exact solution is presented in parametric form of this nonlinear time dependent problem. It is demonstrated that initially excited lower hybrid modes always break via phase mixing phenomenon in presence of an inhomogeneous magnetic field. Breaking of such oscillations is revealed by the appearance of spikes in the plasma density profile.
The Energy Eigenvalues of the Two Dimensional Hydrogen Atom in a Magnetic Field
A. Soylu; O. Bayrak; I. Boztosun
In this paper, the energy eigenvalues of the two dimensional hydrogen atom are presented for the arbitrary Larmor frequencies by using the asymptotic iteration method. We first show the energy eigenvalues for the no magnetic field case analytically, and then we obtain the energy eigenvalues for the strong and weak magnetic field cases within an iterative approach for $n=2-10$ and $m=0-1$ states for several different arbitrary Larmor frequencies. The effect of the magnetic field on the energy eigenvalues is determined precisely. The results are in excellent agreement with the findings of the other methods and our method works for the cases where the others fail.
External magnetic field influence on H{sub {alpha}} line in abnormal glow discharge
Obradovic, B.M.; Dojcinovic, I.P.; Kuraica, M.M.; Puric, J. [Faculty of Physics, University of Belgrade, P.O. Box 368, 11001 Belgrade (Serbia and Montenegro) and Center for Science and Development of Technology, Obilicev Venac 26, 11001 Belgrade (Serbia and Montenegro)
Influence of the external axial magnetic field on the hydrogen H{sub {alpha}} line profiles in an abnormal glow discharge has been studied. It has been found that the applied magnetic field predominantly increases the intensity of central component of the characteristic excessively broadened H{sub {alpha}} profile. Magnetic filed causes helical motion of electrons along the electric field lines and prolongs their trajectories increasing the number of collisions with matrix gas. This explains the increase of the central component of H{sub {alpha}} profile and can be regarded as an experimental proof for the main contribution of electron excitation to that part of the profile.
Thin film limits for Ginzburg--Landau with strong applied magnetic fields
Stan Alama; Lia Bronsard; Bernardo Galv�o-Sousa
In this work, we study thin-film limits of the full three-dimensional Ginzburg-Landau model for a superconductor in an applied magnetic field oriented obliquely to the film surface. We obtain Gamma-convergence results in several regimes, determined by the asymptotic ratio between the magnitude of the parallel applied magnetic field and the thickness of the film. Depending on the regime, we show that there may be a decrease in the density of Cooper pairs. We also show that in the case of variable thickness of the film, its geometry will affect the effective applied magnetic field, thus influencing the position of vortices.
Efficiency enhancement of anomalous-Doppler electron cyclotron masers with tapered magnetic field
Xie, Chao-Ran; Hou, Zhi-Ling [Beijing Key Laboratory of Harmful Chemicals Analysis and School of Science, Beijing University of Chemical Technology, Beijing 100029 (China)] [Beijing Key Laboratory of Harmful Chemicals Analysis and School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Kong, Ling-Bao, E-mail: email@example.com, E-mail: firstname.lastname@example.com [School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China) [School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China); Beijing Key Laboratory of Harmful Chemicals Analysis and School of Science, Beijing University of Chemical Technology, Beijing 100029 (China); Liu, Pu-Kun, E-mail: email@example.com, E-mail: email@example.com; Du, Chao-Hai [School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China)] [School of Electronics Engineering and Computer Science, Peking University, Beijing 100871 (China); Jin, Hai-Bo [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China)] [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China)
The efficiency of slow-wave electron cyclotron masers (ECM) is usually low, thus limiting the practical applications. Here, a method of tapered magnetic field is introduced for the efficiency enhancement of the slow-wave ECM. The numerical calculations show that the tapered magnetic-field method can enhance the efficiency of slow-wave ECM significantly. The effect of beam electron velocity spread on the efficiency has also been studied. Although the velocity spread reduces the efficiency, a great enhancement of efficiency can still be obtained by the tapered magnetic field method.
Concerning the existence of a 'turbulent' magnetic field in the quiet Sun
R. Manso Sainz; E. Landi Degl'Innocenti; J. Trujillo Bueno
We report on the a5F-y5F* multiplet of Ti I and its interest for the study of 'turbulent' magnetic fields in the quiet solar photosphere. In particular, we argue that the sizable scattering polarization signal of the 4536 \\AA line (whose lower and upper levels have Land\\'e factors equal to zero), relative to the rest of the lines in the multiplet, gives direct evidence for the existence of an ubiquitous, unresolved magnetic field. We cannot determine precisely the strength of the magnetic field, but its very existence is evidenced by the differential Hanle effect technique that this Ti I multiplet provides.
California at Berkeley, University of
THE MAGNETIC FIELD PILE-UP AND DENSITY DEPLETION IN THE MARTIAN MAGNETOSHEATH: A COMPARISON Global Surveyor (MGS) and theWind spacecraft we show that the region of magnetic field pile of the terrestrial magnetopause when the magnetic field piles up against the obstacle and particles in the pile
Propagation of shear Alven waves in two-ion species plasmas confined by a nonuniform magnetic field
California at Los Angles, University of
Propagation of shear Alven waves in two-ion species plasmas confined by a nonuniform magnetic field for waves originally propagating along the magnetic field direction. Calculations are performed for waves propagating across the confinement magnetic field, typically the compressional or fast Alfven wave
Wave Turbulence on the Surface of a Ferrofluid in a Magnetic Field Francois Boyer and Eric Falcon*
Falcon, Eric
Wave Turbulence on the Surface of a Ferrofluid in a Magnetic Field Franc�ois Boyer and Eric Falcon the observation of wave turbulence on the surface of a ferrofluid mechanically forced and submitted to a static normal magnetic field. We show that magnetic surface waves arise only above a critical field. The power
Wave turbulence on the surface of a ferrofluid submitted to a magnetic field Francois Boyer and Eric Falcon
Paris-Sud XI, Universit� de
Wave turbulence on the surface of a ferrofluid submitted to a magnetic field Fran�cois Boyer the observation of wave turbulence on the surface of a ferrofluid mechanically forced and submitted to a static normal magnetic field. We show that magnetic surface waves arise only above a critical field. The power
Reply to "Comment on `Microwave vortex dissipation of superconducting Nd-Ce-Cu-O epitaxial films in high magnetic fields' "
Yeh, Nai-Chang
in high magnetic fields' " N.-C. Yeh1 and D. M. Strayer2 1Department of Physics, California Institute of Technology, Pasadena, California 91125, USA 2 Jet Propulsion Laboratory, California Institute of Technology of these modes are insensitive to the application of external magnetic fields, be- cause magnetic fields do
Field representation of a watt balance magnet by partial profile measurements
Li, Shisong; Zhao, Wei; Huang, Songling
Permanent magnets with high-permeability yokes have been widely used in watt balances for supplying a robust and strong magnetic field at the coil position. Subjected to the mechanical realization, only several $B_r(z)$ (radial magnetic field along the vertical direction) profiles can be measured by coils for field characterization. In this article, we present an algorithm that can construct the global magnetic field of the air gap based on $N(N\\geq1)$ additional measurements of $B_r(z)$ profiles. The proposed algorithm is realized by polynomially estimating the $B_z(r)$ function with analysis of basic relations between two magnetic components in air gap, i.e., $B_r(r,z)$ and $B_z(r,z)$, following the Maxwell's equations. The algorithm, verified by FEM simulations, can characterize the three-dimensional contribution of the magnetic field for a watt balance magnet with acceptable accuracy, which would supply basic field parameters for alignment and misalignment corrections.
The crucial role of surface magnetic fields for the solar dynamo
Cameron, Robert
Sunspots and the plethora of other phenomena occuring in the course of the 11-year cycle of solar activity are a consequence of the emergence of magnetic flux at the solar surface. The observed orientations of bipolar sunspot groups imply that they originate from toroidal (azimuthally orientated) magnetic flux in the convective envelope of the Sun. We show that the net toroidal magnetic flux generated by differential rotation within a hemisphere of the convection zone is determined by the emerged magnetic flux at the solar surface and thus can be calculated from the observed magnetic field distribution. The main source of the toroidal flux is the roughly dipolar surface magnetic field at the polar caps, which peaks around the minima of the activity cycle.
Repulsive trap for two electrons in a magnetic field A. D. Chepelianskii1
Shepelyansky, Dima
of crossed electric and magnetic fields. It is found that near one antidot the electron pair can be trapped for a long time, and the escape rate from such a trap is proportional to the square of a weak electric field field. Experiments with antidot lattices were car- ried out by different experimental groups see, e
Nonideal evolution of nonaxisymmetric, force-free magnetic fields in a magnetar
Alpha Mastrano; Andrew Melatos
Recent numerical magnetohydrodynamic calculations by Braithwaite and collaborators support the `fossil field' hypothesis regarding the origin of magnetic fields in compact stars and suggest that the resistive evolution of the fossil field can explain the reorganisation and decay of magnetar magnetic fields. Here, these findings are modelled analytically by allowing the stellar magnetic field to relax through a quasistatic sequence of nonaxisymmetric, force-free states, by analogy with spheromak relaxation experiments, starting from a random field. Under the hypothesis that the force-free modes approach energy equipartition in the absence of resistivity, the output of the numerical calculations is semiquantitatively recovered: the field settles down to a linked poloidal-toroidal configuration, which inflates and becomes more toroidal as time passes. A qualitatively similar (but not identical) end state is reached if the magnetic field evolves by exchanging helicity between small and large scales according to an $\\alpha$-dynamo-like, mean-field mechanism, arising from the fluctuating electromotive force produced by the initial random field. The impossibility of matching a force-free internal field to a potential exterior field is discussed in the magnetar context.
Stationary components of HeI in strong magnetic fields - a tool to identify magnetic DB white dwarfs
S. Jordan; P. Schmelcher; W. Becken
In only three of the 61 known magnetic white dwarfs helium has been identified unambiguously while about 20% of all non-magnetic stars of this class are known to contain HeI or HeII. Until recently, data for HeI data were available only for magnetic fields below 20MG. This changed with the publication of extensive data by the group in Heidelberg. The corresponding calculations have now been completed for the energetically lowest five states of singlet and triplet symmetry for the subspaces with |m| <= 3; selected calculations have been performed for even higher excitations. In strongly magnetized white dwarfs only line components are visible whose wavelengths vary slowly with respect to the magnetic field, particularly stationary components which have a wavelength minimum or maximum in the range of the magnetic fields strengths on the stellar surface. In view of the many ongoing surveys finding white dwarfs we want to provide the astronomical community with a tool to identify helium in white dwarfs for fields up to 5.3GG. To this end we present all calculated helium line components whose wavelengths in the UV, optical, and near IR vary slowly enough with respect to the field strength to produce visible absorption features. We also list all stationary line components in this spectral range. Finally, we find series of minima and maxima which occur as a result of series of extremal transitions to increasingly higher excitations. We estimated the limits for 8 series which can possibly give rise to additional absorption in white dwarf spectra; one strong absorption feature in GD229 which is yet unexplained by stationary components is very close to two estimated series limits.
FURMAN NMR SAFETY INFORMATION Standard safety guidelines have been put in place for work around the high-field magnets, and all users
Earth's magnetic field 6.0 x 10-5 T at the equator Refrigerator Magnet .0100-.0150 T MRI Medical the high-field magnets, and all users must take proper precautions to prevent expensive instrument damage and serious personal injury, including death. NMR Magnetic Field Strength � Remember: The magnetic field
Biological Effects of Electrical and Magnetic Fields: Is It Real?�
Durham, M. O.
this conflict. The model is a composite energy approach that identifies the classical, thermal electromagnetic interaction as well as a completely independent electric and independent magnetic component. An overview of the biological investigations is presented...
Interstellar Hydroxyl Masers in the Galaxy. II. Zeeman Pairs and the Galactic Magnetic Field
Vincent L. Fish; Mark J. Reid; Alice L. Argon; Karl M. Menten
We have identified and classified Zeeman pairs in the survey by Argon, Reid, & Menten of massive star-forming regions with 18 cm (2 Pi 3/2, J = 3/2) OH maser emission. We have found a total of more than 100 Zeeman pairs in more than 50 massive star-forming regions. The magnetic field deduced from the Zeeman splitting has allowed us to assign an overall line-of-sight magnetic field direction to many of the massive star-forming regions. Combining these data with other data sets obtained from OH Zeeman splitting, we have looked for correlations of magnetic field directions between star-forming regions scattered throughout the Galaxy. Our data do not support a uniform, Galactic-scale field direction, nor do we find any strong evidence of magnetic field correlations within spiral arms. However, our data suggest that in the Solar neighborhood the magnetic field outside the Solar circle is oriented clockwise as viewed from the North Galactic Pole, while inside the Solar circle it is oriented counterclockwise. This pattern, including the magnetic field reversal near the Sun, is in agreement with results obtained from pulsar rotation measures.
Singular Limits for Thin Film Superconductors in Strong Magnetic Fields - Maan Field Model for Thin Films
Stan Alama; Lia Bronsard; Bernardo Galv�o-Sousa
We consider singular limits of the three-dimensional Ginzburg-Landau functional for a superconductor with thin-film geometry, in a constant external magnetic field. The superconducting domain has characteristic thickness on the scale $\\eps>0$, and we consider the simultaneous limit as the thickness $\\eps\\rightarrow 0$ and the Ginzburg-Landau parameter $\\kappa\\rightarrow\\infty$. We assume that the applied field is strong (on the order of $\\eps^{-1}$ in magnitude) in its components tangential to the film domain, and of order $\\log\\kappa$ in its dependence on $\\kappa$. We prove that the Ginzburg-Landau energy $\\Gamma$-converges to an energy associated with a two-obstacle problem, posed on the planar domain which supports the thin film. The same limit is obtained regardless of the relationship between $\\eps$ and $\\kappa$ in the limit. Two illustrative examples are presented, each of which demonstrating how the curvature of the film can induce the presence of both (positively oriented) vortices and (negatively oriented) antivortices coexisting in a global minimizer of the energy.
Classification of instability modes in a model of aluminium reduction cells with a uniform magnetic field
(sodium aluminium fluoride) by an electric current of 350-500kA, which passes vertically down fromClassification of instability modes in a model of aluminium reduction cells with a uniform magnetic reduction cells in the presence of a uniform, vertical, background magnetic field is presented