WorldWideScience

Sample records for magnetic field generation

  1. Magnetic field generator

    Science.gov (United States)

    Krienin, Frank (Shoreham, NY)

    1990-01-01

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

  2. Magnetic Field Generation in Stars

    Science.gov (United States)

    Ferrario, Lilia; Melatos, Andrew; Zrake, Jonathan

    2015-10-01

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

  3. Magnetic Field Generation in Stars

    CERN Document Server

    Ferrario, Lilia; Zrake, Jonathan

    2015-01-01

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

  4. Primordial Generation of Magnetic Fields

    CERN Document Server

    Pandey, Arun Kumar

    2015-01-01

    We reexamine generation of the primordial magnetic fields, at temperature $T>80$TeV, by applying a consistent kinetic theory framework which is suitably modified to take the quantum anomaly into account. The modified kinetic equation can reproduce the known quantum field theoretic results upto the leading orders. We show that our results qualitatively matches with the earlier results obtained using heuristic arguments. The modified kinetic theory can give the instabilities responsible for generation of the magnetic field due to chiral imbalance in two distinct regimes: a) when the collisions play a dominant role and b) when the primordial plasma can be regarded as collisionless. We argue that the instability developing in the collisional regime can dominate over the instability in the collisionless regime.

  5. Generation of helical magnetic fields from inflation

    OpenAIRE

    Jain, Rajeev Kumar; Durrer, Ruth; Hollenstein, Lukas

    2012-01-01

    The generation of helical magnetic fields during single field inflation due to an axial coupling of the electromagnetic field to the inflaton is discussed. We find that such a coupling always leads to a blue spectrum of magnetic fields during slow roll inflation. Though the helical magnetic fields further evolve during the inverse cascade in the radiation era after inflation, we conclude that the magnetic fields generated by such an axial coupling can not lead to observed fi...

  6. Generation of Magnetic Fields in Cosmology

    OpenAIRE

    Dolgov, A. D.

    2001-01-01

    Mechanisms of generation of magnetic fields in the early universe which could seed the present-day large scale galactic magnetic fields, are briefly reviewed. Three possible ways to create large scale magnetic fields are discussed: breaking of conformal invariance of electromagnetic interactions and inflationary stretching of the field wave length, first order cosmological phase transitions, and chaotic electric currents generated by turbulent flows in the primeval plasma.

  7. Magnetic field generation in Higgs inflation model

    OpenAIRE

    Das, Moumita; Mohanty, Subhendra(Physical Research Laboratory, Ahmedabad, 380009, India)

    2010-01-01

    We study the generation of magnetic field in Higgs-inflation models where the Standard Model Higgs boson has a large coupling to the Ricci scalar. We couple the Higgs field to the Electromagnetic fields via a non- renormalizable dimension six operator suppressed by the Planck scale in the Jordan frame. We show that during Higgs inflation magnetic fields with present value $10^{-6}$ Gauss and comoving coherence length of $100 kpc$ can be generated in the Einstein frame. The p...

  8. The magnetic field gradients generation for magnetic resonance tomography

    International Nuclear Information System (INIS)

    To obtain three-dimensional images in the computerized tomography a gradient of magnetic field should be generated. In this paper the analytical as well as computerized calculations of magnetic coils for such purposes are presented

  9. Magnetic field generation in curved spacetimes

    CERN Document Server

    Mahajan, Swadesh M

    2011-01-01

    Using the generally covariant magnetofluid formalism for a hot plasma, a new curvature (of space time) driven mechanism for generating seed vorticity/magnetic field is presented. The "battery" owes its origin to the interaction between gravity (epitomized in the spatial variation of the metric tensor) and the inhomogeneous plasma thermodynamics. The general relativistic drive for the seed field is evaluated in a simplified model of a hot plasma accreting around a Schwarzschild black hole. Some astrophysical applications are suggested.

  10. RESISTIVE MAGNETIC FIELD GENERATION AT COSMIC DAWN

    International Nuclear Information System (INIS)

    Relativistic charged particles (CRs for cosmic rays) produced by supernova explosion of the first generation of massive stars that are responsible for the reionization of the universe escape into the intergalactic medium, carrying an electric current. Charge imbalance and induction give rise to a return current, j-vectort, carried by the cold thermal plasma which tends to cancel the CR current. The electric field, E-vector =? j-vectort, required to draw the collisional return current opposes the outflow of low-energy CRs and ohmically heats the cold plasma. Owing to inhomogeneities in the resistivity, ?(T), caused by a structure in the temperature, T, of the intergalactic plasma, the electric field possesses a rotational component which sustains Faraday's induction. It is found that a magnetic field is robustly generated throughout intergalactic space at a rate of 10-17 to 10-16 G Gyr-1, until the temperature of the intergalactic medium is raised by cosmic reionization. The magnetic field may seed the subsequent growth of magnetic fields in the intergalactic environment. The role of CR-driven instabilities is discussed, and nonlinear effects are briefly considered.

  11. Error field generation of solenoid magnets

    International Nuclear Information System (INIS)

    Many applications for large solenoids and solenoidal arrays depend on the high precision of the axial field profile. In cases where requirements of ?B/B for nonaxial fields are on the order of 10-4, the actual winding techniques of the solenoid need to be considered. Whereas an ideal solenoid consisting of current loops would generate no radial fields along the axis, in reality, the actual current-carrying conductors must follow spiral or helical paths. A straightforward method for determining the radial error fields generated by coils wound with actual techniques employed in magnet fabrication has been developed. The method devised uses a computer code which models a magnet by sending a single, current-carrying filament along the same path taken by the conductor during coil winding. Helical and spiral paths are simulated using small, straight-line current segments. This technique, whose results are presented in this paper, was used to predict radial field errors for the Elmo Bumpy Torus-Proof of Principle magnet. These results include effects due to various winding methods, not only spiral/helical and layer-to-layer transitions, but also the effects caused by worst-case tolerance conditions both from the conductor and the winding form (bobbin). Contributions made by extraneous circuitry (e.g., overhead buswork and incoming leads) are also mentioned

  12. Primordial magnetic field generated in natural inflation

    Science.gov (United States)

    AlMuhammad, Anwar S.; Lopez-Mobilia, Rafael

    2015-11-01

    We study the simple gauge invariant model {f^2}FF as a way to generate primordial magnetic fields (PMF) in natural inflation (NI). We compute both magnetic and electric spectra generated by the {f^2}FF model in NI for different values of model parameters and find that both de Sitter and power law expansion lead to the same results at sufficiently large number of e-foldings. We also find that the necessary scale invariance property of the PMF cannot be obtained in NI in first order of slow roll limits under the constraint of inflationary potential, V( 0 ) ˜eq 0. Furthermore, if this constraint is relaxed to achieve scale invariance, then the model suffers from the backreaction problem for the co-moving wave number, k ? 8.0× 10^{-7} {Mpc^{-1}} and Hubble parameter, H_i ? 1.25× 10^{-3} {M_{Pl}}. The former can be considered as a lower bound of k and the later as an upper bound of H_i for a model which is free from the backreaction problem. Further, we show that there is a narrow range of the height of the potential ? around {? _{min}} ? 0.00874{M_{{Pl}}} and of k around {k_{min}} ˜ 0.0173{Mp}{{c}^{ - 1}}, at which the energy of the electric field can fall below the energy of the magnetic field. The range of k lies within some observable scales. However, the relatively short range of k presents a challenge to the viability of this model.

  13. Design of CHWHG Type Low Frequency Magnetic Fields Generator

    Directory of Open Access Journals (Sweden)

    Bo Cheng

    2007-01-01

    Full Text Available Highly considering the invariability of magnetic field strength in the Magnetic Field Generators, which used to stimulate rat's nerve cell, surely improve the stimulation performance outcome. A new technique to get an invariable magnetic field strength within Magnetic Field Generator has been proposed, Furthermore it had implemented on microcontroller-based system providing an Alternating Magnetic Field Generator (AMFG with a high performance. The performance of the system is evaluated using two different methods. The results show that the errors are well and acceptable.

  14. High Magnetic Field Generator of Sub-Microsecond Duration

    Directory of Open Access Journals (Sweden)

    Audrius Grainys

    2012-04-01

    Full Text Available The article describes the possibility of generating a micro and sub-microsecond magnetic impulse reaching 1–10 T, investigates various configurations of microcoils and discusses the principal circuit of a magnetic field impulse generator of microsecond duration. The transient processes of current, temperature and magnetic field are calculated applying the finite element method.Article in Lithuanian

  15. Fast ignition studies and magnetic field generation

    International Nuclear Information System (INIS)

    Experiments, theory and simulation have been carried out to describe intense, relativistic short pulse laser interaction with dense plasmas. Magnetic fields of up to 0.7 GGauss have been measured through polarization measurements of high order laser harmonics. Simulation and analytic theory show that these fields are associated with photon momentum deposition. The same mechanism can cause weaker fields in the speckle of long pulse laser in underdense plasmas, leading to termination of SBS. Other magnetic fields in gas-filled hohlraums lead to steep temperature gradients in regions where linear transport fails. A Vlasov-Fokker-Planck code has been developed to study these effects more accurately. (author)

  16. Visualisation of Magnetic Fields Generated by Helmholtz Coils

    Directory of Open Access Journals (Sweden)

    Jozef Suriansky

    2006-01-01

    Full Text Available This article deals with a method of a homogenous magnetic field generation using Helmholtz coils. There is also an experiment of a magnetic field visualisation with a digital image processing performed with a magneto-resistive sensor described. At the end of this article, there is a possibility of permeability measurement using digital images of a magnetic field shown.

  17. Improved Magnetic Field Generation Efficiency and Higher Temperature Spheromak Plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Wood, R D; Hill, D N; McLean, H S; Hooper, E B; Hudson, B F; Moller, J M; Romero-Talamas, C A

    2008-09-15

    New understanding of the mechanisms governing the observed magnetic field generation limits on the sustained spheromak physics experiment has been obtained. Extending the duration of magnetic helicity injection during the formation of a spheromak and optimizing the ratio of injected current to bias flux produce higher magnetic field plasmas with record spheromak electron temperatures. To explore magnetic field buildup efficiency limits, the confinement region geometry was varied resulting in improved field buildup efficiencies.

  18. The Generation of Magnetic Fields Through Driven Turbulence

    OpenAIRE

    Cho, Jungyeon; Vishniac, Ethan T.

    2000-01-01

    We have tested the ability of driven turbulence to generate magnetic field structure from a weak uniform field using three dimensional numerical simulations of incompressible turbulence. We used a pseudo-spectral code with a numerical resolution of up to $144^3$ collocation points. We find that the magnetic fields are amplified through field line stretching at a rate proportional to the difference between the velocity and the magnetic field strength times a constant. Equipar...

  19. Evolution of inflation-generated magnetic field through phase transitions

    OpenAIRE

    Kahniashvili, Tina; Brandenburg, Axel; Campanelli, Leonardo; Ratra, Bharat; Tevzadze, Alexander G.

    2012-01-01

    We study the evolution of an inflation-generated magnetic field, due to its coupling to fluid motions, during cosmological phase transitions. We find that the magnetic field stays almost unchanged on large scales, while on small scales the spectrum is modified in such a way that power at small scales becomes progressively suppressed. We also show that the magnetic field generates turbulent motions in the initially turbulence-free plasma. On large scales, the slope of the res...

  20. Evolution of Primordial Magnetic Fields: From Generation Till Today

    OpenAIRE

    Kahniashvili, Tina; Brandenburg, Axel; Tevzadze, Alexander G.

    2015-01-01

    In this presentation we summarize our previous results concerning the evolution of primordial magnetic fields with and without helicity during the expansion of the Universe. We address different magnetogenesis scenarios such as inflation, electroweak and QCD phase transitions magnetogenesis. A high Reynolds number in the early Universe ensures strong coupling between magnetic field and fluid motions. After generation the subsequent dynamics of the magnetic field is governed ...

  1. RESISTIVE MAGNETIC FIELD GENERATION AT COSMIC DAWN

    OpenAIRE

    Francesco Miniati; Bell, A. R.

    2011-01-01

    Relativistic charged particles (CRs for cosmic rays) produced by supernova explosion of the first generation of massive stars that are responsible for the reionization of the universe escape into the intergalactic medium, carrying an electric current. Charge imbalance and induction give rise to a return current, ? jt , carried by the cold thermal plasma which tends to cancel the CR current. The electric field, ?E = n? jt , required to draw the collisional return current opposes the outflow of...

  2. Generation of Magnetic Fields by a Gravitomagnetic Plasma Battery

    OpenAIRE

    Khanna, Ramon

    1998-01-01

    The generation of magnetic fields by a battery, operating in an ion-electron plasma around a Kerr black hole, is studied in the 3+1 split of the Kerr metric. It is found that the gravitomagnetic contributions to the electron partial pressure are able to drive currents. The strength of the equilibrium magnetic field should be higher than for the classical Biermann battery, which is found to operate in this relativistic context as well, since the gravitomagnetic driving terms ...

  3. Magnetic field generation from non-equilibrium phase transitions

    OpenAIRE

    Boyanovsky, D.; De Vega, H. J.; Simionato, M.

    2002-01-01

    We study the generation of magnetic fields during the stage of particle production resulting from spinodal instabilities during phase transitions out of equilibrium. The main premise is that long-wavelength instabilities that drive the phase transition lead to strong non-equilibrium charge and current fluctuations which generate electromagnetic fields. We present a formulation based on the non-equilibrium Schwinger-Dyson equations that leads to an exact expression for the sp...

  4. Effects of non-linearities on magnetic field generation

    International Nuclear Information System (INIS)

    Magnetic fields are present on all scales in the Universe. While we understand the processes which amplify the fields fairly well, we do not have a ''natural'' mechanism to generate the small initial seed fields. By using fully relativistic cosmological perturbation theory and going beyond the usual confines of linear theory we show analytically how magnetic fields are generated. This is the first analytical calculation of the magnetic field at second order, using gauge-invariant cosmological perturbation theory, and including all the source terms. To this end, we have rederived the full set of governing equations independently. Our results suggest that magnetic fields of the order of 10-30- 10-27 G can be generated (although this depends on the small scale cut-off of the integral), which is largely in agreement with previous results that relied upon numerical calculations. These fields are likely too small to act as the primordial seed fields for dynamo mechanisms

  5. Highly stable and finely tuned magnetic fields generated by permanent magnet assemblies.

    Science.gov (United States)

    Danieli, E; Perlo, J; Blümich, B; Casanova, F

    2013-05-01

    Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Such stand-alone magnets are very attractive for many scientific and engineering areas, but they suffer from poor temporal field stability, which arises from the strong sensitivity of the magnetic materials and mechanical support to temperature variation. In this work, we describe a highly efficient method useful to cancel the temperature coefficient of permanent magnet assemblies in a passive and accurate way. It is based on the combination of at least two units made of magnetic materials with different temperature coefficients arranged in such a way that the ratio of the fields generated by each unit matches the ratio of their effective temperature coefficients defined by both the magnetic and mechanical contributions. Although typically available magnetic materials have negative temperature coefficients, the cancellation is achieved by aligning the fields generated by each unit in the opposite direction. We demonstrate the performance of this approach by stabilizing the field generated by a dipolar Halbach magnet, recently proposed to achieve high field homogeneity. Both the field drift and the homogeneity are monitored via nuclear magnetic resonance spectroscopy experiments. The results demonstrate the compatibility of the thermal compensation approach with existing strategies useful to fine-tune the spatial dependence of the field generated by permanent magnet arrays. PMID:23683185

  6. Early Starbursts and Magnetic Field Generation in Galaxy Clusters

    CERN Document Server

    Völk, H J; Völk, Heinrich J.

    2000-01-01

    We propose a mechanism for the early generation of the mean Intracluster magnetic field in terms of magnetized galactic winds. These winds are the result of starburst phases of the cluster galaxies, assumed to produce the predominant population of early type galaxies in mergers of gas-rich progenitors. After further cluster contraction typical field strengths are $10^{-7}$ Gauss. This estimate may increase to the level of $10^{-6}$ Gauss if more extreme galactic parameters, and subsequent shear amplification of the field are considered. The topology of the field is one of almost unconnected Wind Bubbles with Parker-type spiral field configurations over scales of the distance between galaxies. Further cluster accretion, that continues chaotically in space and time up to the present, will perturb these "large-scale" mean fields on smaller or at best comparable spatial scales. The small scale fields in the resulting turbulent fluctuation spectrum should be able to confine relativistic particles over times longer...

  7. Computational Models for Creating Homogeneous Magnetic Field Generation Systems

    Directory of Open Access Journals (Sweden)

    Gerlys M. Villalobos-Fontalvo

    2013-11-01

    Full Text Available It is increasingly common to use magnetic fields at the cellular level to assess their interaction with biological tissues. The stimulation is usually done with Helmholtz coils which generate a uniform magnetic field in the center of the system. However, assessing cellular behavior with different magnetic field characteristics can be a long and expensive process. For this, it can be used computational models to previously estimate the cellular behavior due to variety of field characteristics prior to in-vitro stimulation in a laboratory. In this paper, we present a methodology for the development of three computational models of homogeneous magnetic field generation systems for possible application in cell stimulation. The models were developed in the Ansys Workbench environment and it was evaluated the magnetic flux density behavior at different configurations. The results were validated with theoretical calculations from the Biot-Savart law. Validated models will be coupled to Ansys APDL environment in order to assess the harmonic response of the system.

  8. Energy confinement and magnetic field generation in the SSPX spheromak

    Energy Technology Data Exchange (ETDEWEB)

    Hudson, B; McLean, H S; Wood, R D; Hooper, E B; Hill, D N; Jayakumar, J; Moller, J; Romero-Talamas, C; Casper, T A; LoDestro, L L; Pearlstein, L D; Johnson, III, J A; Mezonlin, E

    2008-02-11

    The Sustained Spheromak Physics Experiment (SSPX) [E.B. Hooper, et. al., Nuclear Fusion, Vol. 39, No. 7] explores the physics of efficient magnetic field buildup and energy confinement, both essential parts of advancing the spheromak concept. Extending the spheromak formation phase increases the efficiency of magnetic field generation with the maximum edge magnetic field for a given injector current (B/I) from 0.65 T/MA previously to 0.9 T/MA. We have achieved the highest electron temperatures (T{sub e}) recorded for a spheromak with T{sub e} > 500 eV, toroidal magnetic field {approx}1 T and toroidal current ({approx}1 MA) [R.D. Wood, D.N. Hill, H.S. McLean, E.B. Hooper, B.F. Hudson, J.M. Moller, 'Improved magnetic field generation efficiency and higher temperature spheromak plasmas', submitted to Physical Review Letters]. Extending the sustainment phase to > 8 ms extends the period of low magnetic fluctuations (< 1 %) by 50%. The NIMROD 3-D resistive MHD code [C.R. Sovinec, T.A. Gianakon, E.D. Held, S.E. Kruger and D.D. Schnack, The NIMROD Team, Phys. Plasmas 10, 1727 (2003)] reproduces the observed flux amplification {Psi}{sub pol}/{Psi}{sub gun}. Successive gun pulses are demonstrated to maintain the magnetic field in a quasi-steady state against resistive decay. Initial measurements of neutral particle flux in multi-pulse operation show charge-exchange power loss < 1% of gun input power and dominantly collisional majority ion heating. The evolution of electron temperature shows a distinct and robust feature of spheromak formation: a hollow-to-peaked T{sub e}(r) associated with q {approx} 1/2.

  9. Generation of magnetic fields in Einstein-Aether gravity

    CERN Document Server

    Saga, Shohei; Ichiki, Kiyotomo; Sugiyama, Naoshi

    2013-01-01

    Recently the lower bounds of the intergalactic magnetic fields $10^{-16} \\sim 10^{-20}$ Gauss are set by gamma-ray observations while it is unlikely to generate such large scale magnetic fields through astrophysical processes. It is known that large scale magnetic fields could be generated if there exist cosmological vector mode perturbations in the primordial plasma. The vector mode, however, has only a decaying solution in General Relativity if the plasma consists of perfect fluids. In order to investigate a possible mechanism of magnetogenesis in the primordial plasma, here we consider cosmological perturbations in the Einstein-Aether gravity model, in which the aether field can act as a new source of vector metric perturbations and thus of magnetic fields. We estimate the angular power spectra of temperature and B-mode polarization of the Cosmic Microwave Background (CMB) Anisotropies in this model and put a rough constraint on the aether field parameters from latest observations. We then estimate the pow...

  10. Second order semiclassics with self-generated magnetic fields

    DEFF Research Database (Denmark)

    Erdös, Laszlo; Fournais, SØren

    2012-01-01

    We consider the semiclassical asymptotics of the sum of negative eigenvalues of the three-dimensional Pauli operator with an external potential and a self-generated magnetic field B. We also add the field energy ß¿B 2 and we minimize over all magnetic fields. The parameter ß effectively determines the strength of the field. We consider the weak field regime with ßh2 = const > 0, where h is the semiclassical parameter. For smooth potentials we prove that the semiclassical asymptotics of the total energy is given by the non-magnetic Weyl term to leading order with an error bound that is smaller by a factor h 1+e , i.e. the subleading term vanishes. However for potentials with a Coulomb singularity, the subleading term does not vanish due to the non-semiclassical effect of the singularity. Combined with a multiscale technique, this refined estimate is used in the companion paper (Erdos et al. in Scott correction for large molecules with a self-generated magnetic field, Preprint, 2011) to prove the second order Scott correction to the ground state energy of large atoms and molecules.

  11. FORMING CAPABILITIES OF A PULSE MAGNETIC FIELD GENERATOR

    Directory of Open Access Journals (Sweden)

    A. A. Petkov

    2015-04-01

    Full Text Available Purpose. Determination of areas ratio of the parameters of the discharge circuit elements of the generator, which ensure the formation of magnetic field pulses of different shapes. Methodology. Numerical simulation using dimensionless variables that determine the nature of the transition process in the discharge circuit of the generator, and use the procedure for determining the pulse points of meeting the conditions of extremum and the transition through zero. Results. Obtained a description of the formation of the three specific areas of waveforms: oscillatory weakly damped oscillatory strongly damped and unipolar pulse with a monotonic rise and fall values. A relation to the choice of parameters of elements of the discharge circuit of the generator, which formed unipolar pulses with a monotonic rise and fall values. Originality. A completed and extended database that implements the mapping of the formal description of the pulse shape with a description of areas ratio parameters for high-voltage pulse discharge circuit test units, with respect to the pulses of current flowing in the formation of the magnetic field. Practical value. The relations obtained allow to select the parameters of the discharge circuit elements of the generator designed to generate test pulses of magnetic field.

  12. Generation and measurement of pulsed high magnetic field

    CERN Document Server

    Jana, S

    2000-01-01

    Pulsed magnetic field has been generated by discharging a capacitor bank through a 5-layer air-core solenoid. The strength of the magnetic field at its peak has been measured using the voltage induced in various pick-up coils, and also from the Zeeman splitting of an ion having a known g value. Synchronizing a xenon flash at the peak of the magnetic field, this lab-made instrument has been made well suited to study the Zeeman effect, etc. at a temperature of 25 K. As an application of this setup, we have investigated the Zeeman splitting of the sup 4 I sub 9 sub / sub 2-> sup 4 G sub 5 sub / sub 2 transition of the Nd sup 3 sup + -doped CsCdCl sub 3 crystal at 7.8 T, and determined the splitting factors.

  13. Generation of scale invariant magnetic fields in bouncing universes

    Science.gov (United States)

    Sriramkumar, L.; Atmjeet, Kumar; Jain, Rajeev Kumar

    2015-09-01

    We consider the generation of primordial magnetic fields in a class of bouncing models when the electromagnetic action is coupled non-minimally to a scalar field that, say, drives the background evolution. For scale factors that have the power law form at very early times and non-minimal couplings which are simple powers of the scale factor, one can easily show that scale invariant spectra for the magnetic field can arise before the bounce for certain values of the indices involved. It will be interesting to examine if these power spectra retain their shape after the bounce. However, analytical solutions for the Fourier modes of the electromagnetic vector potential across the bounce are difficult to obtain. In this work, with the help of a new time variable that we introduce, which we refer to as the e-Script N-fold, we investigate these scenarios numerically. Imposing the initial conditions on the modes in the contracting phase, we numerically evolve the modes across the bounce and evaluate the spectra of the electric and magnetic fields at a suitable time after the bounce. As one could have intuitively expected, though the complete spectra depend on the details of the bounce, we find that, under the original conditions, scale invariant spectra of the magnetic fields do arise for wavenumbers much smaller than the scale associated with the bounce. We also show that magnetic fields which correspond to observed strengths today can be generated for specific values of the parameters. But, we find that, at the bounce, the backreaction due to the electromagnetic modes that have been generated can be significantly large calling into question the viability of the model. We briefly discuss the implications of our results.

  14. Local trace asymptotics in the self-generated magnetic field

    OpenAIRE

    Ivrii, Victor

    2011-01-01

    We consider a semiclassical asymptotics of local trace for the 3D-Schroedinger operator with self-generated magnetic field; it is given by Weyl expression with O(h^{-1}) error and under standard condition to Hamiltonian trajectories even o(h^{-1}). In comparison to v1,2 errors are corrected, new results are added and more details are provided. Misprint correction in comparison to v3

  15. High magnetic field generation using single-turn coils

    Science.gov (United States)

    Werst, M. D.; Ingram, S. K.; Wehrlen, D. J.; Weldon, W. F.

    1994-07-01

    The advent of the homopolar generator has recently permitted the demonstration of a 20 T on-axis, single turn toroidal magnet. Homopolar generators are inherently high current, low-voltage machines which ideally match the requirements of single-turn coils. Magnetic field levels previously limited by the insulation's thermal and voltage breakdown capability have been surpassed. The entire coil volume is essentially occupied by high strength, high conductivity conductor. A current density of 840 MA/m(sup 2) has been achieved in a 9 cm major radius, toroidal coil with a 9.14 MA, 56 V open-current discharge (sinusoidal pulse, 150 ms). Experimental test results are presented, as well as discussion of the potential for applying this technology to solenoid-type coils. This research is funded by the Texas Atomic Energy Research Foundation.

  16. Glutathione production using magnetic fields generated by magnets

    Scientific Electronic Library Online (English)

    Lucielen Oliveira dos, Santos; Tatiane Araujo, Gonzales; Beatriz Torsani, Úbeda; Ranulfo Monte, Alegre.

    2012-12-01

    Full Text Available The objective of this work was to study the production of GSH by Saccharomyces cerevisiae ATCC 7754 in a fermentor (5 L) using a cell recycle system with magnets. The fermentation conditions were 20°C, 500 rpm, 5% (v/v) of inoculum, pHinitial 5, 1.1 vvm aeration and total fermentation time of 72 h. [...] The time of application of MF ranged from 24, 48 or 72 h. In comparison to the control experiment, the best results were obtained with 72 h of application of MF. The cell concentration reached 19.5 g/L and GSH concentration was 271.9 mg/L that corresponded to an increase of 2.63 and 32.1% compared to the control experiment, respectively.

  17. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    Science.gov (United States)

    Bouda, N. R.; Pritchard, J.; Weber, R. J.; Mina, M.

    2015-05-01

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/-20 V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG1) and MOSFET circuits (HCMFG2) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  18. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    International Nuclear Information System (INIS)

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/?20?V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG1) and MOSFET circuits (HCMFG2) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed

  19. Methods of high current magnetic field generator for transcranial magnetic stimulation application

    Energy Technology Data Exchange (ETDEWEB)

    Bouda, N. R., E-mail: nybouda@iastate.edu; Pritchard, J.; Weber, R. J.; Mina, M. [Department of Electrical and Computer engineering, Iowa State University, Ames, Iowa 50011 (United States)

    2015-05-07

    This paper describes the design procedures and underlying concepts of a novel High Current Magnetic Field Generator (HCMFG) with adjustable pulse width for transcranial magnetic stimulation applications. This is achieved by utilizing two different switching devices, the MOSFET and insulated gate bipolar transistor (IGBT). Results indicate that currents as high as ±1200 A can be generated with inputs of +/?20?V. Special attention to tradeoffs between field generators utilizing IGBT circuits (HCMFG{sub 1}) and MOSFET circuits (HCMFG{sub 2}) was considered. The theory of operation, design, experimental results, and electronic setup are presented and analyzed.

  20. Dynamical quark mass generation in a strong external magnetic field

    International Nuclear Information System (INIS)

    We investigate the effect of a strong magnetic field on dynamical chiral symmetry breaking in quenched and unquenched QCD. To this end we apply the Ritus formalism to the coupled set of (truncated) Dyson-Schwinger equations for the quark and gluon propagator under the presence of an external constant Abelian magnetic field. We discuss the effect of the magnetic field onto the quark condensate and extract the chiral susceptibility.

  1. Internal split field generator

    Science.gov (United States)

    Thundat; Thomas George (Knoxville, TN); Van Neste, Charles W. (Kingston, TN); Vass, Arpad Alexander (Oak Ridge, TN)

    2012-01-03

    A generator includes a coil of conductive material. A stationary magnetic field source applies a stationary magnetic field to the coil. An internal magnetic field source is disposed within a cavity of the coil to apply a moving magnetic field to the coil. The stationary magnetic field interacts with the moving magnetic field to generate an electrical energy in the coil.

  2. On Generation of magnetic field in astrophysical bodies

    CERN Document Server

    Verma, M K

    2001-01-01

    In this letter we compute energy transfer rates from velocity field to magnetic field in MHD turbulence using field-theoretic method. The striking result of our field theoretic calculation is that there is a large energy transfer rate from the large-scale velocity field to the large-scale magnetic field. We claim that the growth of large-scale magnetic energy is primarily due to this transfer. We reached the above conclusion without any linear approximation like that in $\\alpha$-dynamo.

  3. Proposal for generating synthetic magnetic fields in hexagonal optical lattices

    Science.gov (United States)

    Tian, Binbin; Endres, Manuel; Pekker, David

    2015-05-01

    We propose a new approach to generating synthetic magnetic fields in ultra cold atom systems that does not rely on either Raman transitions nor periodic drive. Instead, we consider a hexagonal optical lattice produced by the intersection of three laser beams at 120 degree angles, where the intensity of one or more of the beams is spatially non-uniform. The resulting optical lattice remains hexagonal, but has spatially varying hopping matrix elements. For atoms near the Dirac points, these spatial variations appear as a gauge field, similar to the fictitious gauge field that is induced for for electrons in strained graphene. We suggest that a robust way to generate a gauge field that corresponds to a uniform flux is to aligning three gaussian beams to intersect in an equilateral triangle. Using realistic experimental parameters, we show how the proposed setup can be used to observe cyclotron motion of an atom cloud - the conventional Hall effect and distinct Landau levels - the integer quantum Hall effect.

  4. Generation of scale invariant magnetic fields in bouncing universes

    CERN Document Server

    Sriramkumar, L; Jain, Rajeev Kumar

    2015-01-01

    We consider the generation of primordial magnetic fields in a class of bouncing models when the electromagnetic action is coupled non-minimally to a scalar field that, say, drives the background evolution. For scale factors that have the power law form at very early times and non-minimal couplings which are simple powers of the scale factor, one can easily show that scale invariant spectra for the magnetic fields can arise {\\it before the bounce} for certain values of the indices involved. It will be interesting to examine if these power spectra retain their shape {\\it after the bounce}. However, analytical solutions for the Fourier modes of the electromagnetic vector potential across the bounce are difficult to obtain. In this work, with the help of a new time variable that we introduce, which we refer to as the ${\\rm e}$-${\\cal N}$-fold, we investigate these scenarios numerically. Imposing the initial conditions on the modes in the contracting phase, we numerically evolve the modes across the bounce and eva...

  5. The use of mirror image symmetry in coil winding, applications and advantages in magnetic field generation

    International Nuclear Information System (INIS)

    In this paper, an improved method of winding inductors, transformers and motors is discovered. This invention greatly enhances the ability to generate magnetic fields with a given amount of wire. This invention may be as fundamental to the use of magnetic fields as was Nikola Tesla's use of rotating magnetic fields for the generation of alternating current

  6. CMB spectral distortions from the decay of causally generated magnetic fields

    OpenAIRE

    Wagstaff, Jacques M.; Banerjee, Robi

    2015-01-01

    We improve previous calculations of the CMB spectral distortions due to the decay of primordial magnetic fields. We focus our studies on causally generated magnetic fields at the electroweak and QCD phase transitions. We also consider the decay of helical magnetic fields. We show that the decay of non-helical magnetic fields generated at either the electroweak or QCD scale produce $\\mu$ and $y$-type distortions below $10^{-8}$ which are probably not detectable by a future PI...

  7. Consistent generation of magnetic fields in axion inflation models

    CERN Document Server

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

    2015-01-01

    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...

  8. Magnetic separation technique for environmental water purification by strong magnetic field generator loading HTS bulk magnets

    Energy Technology Data Exchange (ETDEWEB)

    Oka, T., E-mail: okat@eng.niigata-u.ac.j [Niigata University, 8050 Ikarashi-Ninocho, Niigata 950-2181 (Japan); Tanaka, K.; Kimura, T.; Mimura, D.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M. [Niigata University, 8050 Ikarashi-Ninocho, Niigata 950-2181 (Japan); Yokoyama, K. [Ashikaga Institute of Technology, 268-1 Ohmae-cho, Ashikaga, Tochigi 326-8558 (Japan); Yamaguchi, M. [Japanese Super-Conductivity Organization Co., Ltd., 2-1-6 Etchujima, Koto-ku, Tokyo 135-8533 (Japan)

    2010-11-01

    The magnetic separation technique in combination with high temperature superconducting bulk magnets has been investigated to purify the ground water which has been used in the coolant system for the incinerator furnace to cool the burning gas. The experiment has been operated by means of the newly-built alternating channel type magnetic separating device. The separation ratios of ferromagnetic flocks including fine magnetite powder have been estimated by means of the high gradient magnetic separation method with small iron balls filled in the water channels. As the magnetic force acting on the magnetic particle is given by the product of a magnetization of the material and a gradient of magnetic field, and as the ferromagnetic stainless steel balls yield the steep gradient of magnetic field around them in a strong magnetic field, the system has exhibited a quite excellent performance with respect to the separation ratios. The separation ratios of the flocks which contain the magnetite powder with the values more than 50 ppm have remained over 80% for under the flow rates less than 5 L/min.

  9. Magnetic separation technique for environmental water purification by strong magnetic field generator loading HTS bulk magnets

    International Nuclear Information System (INIS)

    The magnetic separation technique in combination with high temperature superconducting bulk magnets has been investigated to purify the ground water which has been used in the coolant system for the incinerator furnace to cool the burning gas. The experiment has been operated by means of the newly-built alternating channel type magnetic separating device. The separation ratios of ferromagnetic flocks including fine magnetite powder have been estimated by means of the high gradient magnetic separation method with small iron balls filled in the water channels. As the magnetic force acting on the magnetic particle is given by the product of a magnetization of the material and a gradient of magnetic field, and as the ferromagnetic stainless steel balls yield the steep gradient of magnetic field around them in a strong magnetic field, the system has exhibited a quite excellent performance with respect to the separation ratios. The separation ratios of the flocks which contain the magnetite powder with the values more than 50 ppm have remained over 80% for under the flow rates less than 5 L/min.

  10. Dynamo-generated magnetic fields in fast rotating single giants

    CERN Document Server

    Konstantinova-Antova, Renada; Schröder, Klaus-Peter; Petit, Pascal

    2009-01-01

    Red giants offer a good opportunity to study the interplay of magnetic fields and stellar evolution. Using the spectro-polarimeter NARVAL of the Telescope Bernard Lyot (TBL), Pic du Midi, France and the LSD technique, we began a survey of magnetic fields in single G-K-M giants. Early results include 6 MF-detections with fast rotating giants, and for the first time a magnetic field was detected directly in an evolved M-giant: EK Boo. Our results could be explained in the terms of $\\alpha$--$\\omega$ dynamo operating in these giants.

  11. MHD turbulence developed and generation of magnetic field

    International Nuclear Information System (INIS)

    Turbulence in a conducting medium presents a critical magnetic Reynolds number, as do the linear dynamos with a given velocity field. Results obtained with the EDQNM model in non linear MHD turbulence (helical or non helical) are given

  12. Consistent generation of magnetic fields in axion inflation models

    Science.gov (United States)

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

    2015-05-01

    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 tilde F 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. The EM field is subsequently amplified by parametric resonance during the period of inflaton oscillation. Once the thermal plasma is formed (reheating), the produced helical magnetic fields undergo a turbulent process called inverse cascade, which shifts their peak correlation scales from smaller to larger scales. We consistently take all these effects into account within the regime where the perturbation of phi is negligible and obtain Beff ~ 10?19 G, indicating the necessity of additional mechanisms to accommodate the observations.

  13. Geometrical generation of cosmic magnetic fields within standard electromagnetism

    Scientific Electronic Library Online (English)

    Christos G., Tsagas; Alejandra, Kandus.

    2005-12-01

    Full Text Available We study the evolution of cosmological magnetic fields in FRW models with curved spatial sections and outline a geometrical mechanism for their superadiabatic amplification on large scales. The mechanism operates within standard electromagnetic theory and applies to FRW universes with open spatial s [...] ections. We discuss the general relativistic nature of the effect and show how it modifies the adiabatic magnetic evolution by reducing the depletion rate of the field. Assuming a universe that is only marginally open today (i.e. for 1-omega0 ~ 10-2), we estimate the main features of the superadiabatically amplified residual field and find that is of astrophysical interest.

  14. Self-generation mechanisms of intense magnetic fields in laser produced plasmas on solid targets

    International Nuclear Information System (INIS)

    Mechanisms of magnetic field self-generation in laser produced plasma are presented. Magnetic field generation due to the thermoelectric sources (Vnsub(e) x VTsub(e)), resonance absorption, ponderomotive forces, some kind of instabilities (modulational, Weibel, Rayleigh-Taylor instabilities) is considered. Estimates or scaling laws for parameters typical for current experiments are given. (author)

  15. Ultra-High Intensity Magnetic Field Generation in Dense Plasma

    Energy Technology Data Exchange (ETDEWEB)

    Fisch, Nathaniel J

    2014-01-08

    I. Grant Objective The main objective of this grant proposal was to explore the efficient generation of intense currents. Whereasthefficient generation of electric current in low-­?energy-­? density plasma has occupied the attention of the magnetic fusion community for several decades, scant attention has been paid to carrying over to high-­?energy-­? density plasma the ideas for steady-­?state current drive developed for low-­?energy-­? density plasma, or, for that matter, to inventing new methodologies for generating electric current in high-­?energy-­?density plasma. What we proposed to do was to identify new mechanisms to accomplish current generation, and to assess the operation, physics, and engineering basis of new forms of current drive in regimes appropriate for new fusion concepts.

  16. Noninvasive Measurements of Magnetic Field Generated by Induced Current within Human Body under Exposure to Very Low Frequency Electromagnetic Fields

    Science.gov (United States)

    Tsukada, Keiji; Kiwa, Toshihiko

    2005-04-01

    We have developed a measurement system for a magnetic field that is generated by the induced ionic current within the human body under exposure to very low frequency electromagnetic fields, and compared the magnetic field strength obtained with those of a magnetomyogram (MMG). The developed system consists of an exposure coil, a magnetic sensor, a lock-in detector, and data acquisition. The waveform characteristics of the magnetic field of the induced current (MFIC) of the abdomen from 1 kHz to 400 Hz are obtained. Compared with the magnetic field strength of abdominal MMG, abdominal MFIC is stronger at an exposure electromagnetic field greater than the ?T order.

  17. Magnetic field generation and amplification in an expanding plasma

    CERN Document Server

    Schoeffler, K M; Fonseca, R A; Silva, L O

    2013-01-01

    Particle-in-cell simulations are used to investigate the formation of magnetic fields, B, in plasmas with perpendicular electron density and temperature gradients. For system sizes, L, comparable to the ion skin depth, d_i, it is shown that B ~ d_i/L, consistent with the Biermann battery effect. However, for large L/d_i, it is found that the Weibel instability (due to electron temperature anisotropy) supersedes the Biermann battery as the main producer of B. The Weibel-produced fields saturate at a finite amplitude (plasma \\beta \\approx 100), independent of L. The magnetic energy spectra below the electron Larmor radius scale is well fitted by power law with slope -16/3, as predicted in Schekochihin et al., Astrophys. J. Suppl. Ser 182, 310 (2009).

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

    OpenAIRE

    Herndon, J. Marvin

    2009-01-01

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

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

    International Nuclear Information System (INIS)

    Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion (ICF) implosions are expected to generate magnetic fields at the gas-ice interface and at the ice-ablator interface. The focus here is on the gas-ice interface where the temperature gradient is the largest. A Hall-MHD model is used to study the magnetic field generation and growth for 2-D single-mode and multimode RTI in a stratified two-fluid plasma, the two fluids being ions and electrons. Self-generated magnetic fields are observed and these fields grow as the RTI progresses via the ?ne×?Te term in the generalized Ohm’s law. Srinivasan et al.[Phys. Rev. Lett. 108, 165002 (2012)] present results of the magnetic field generation and growth, and some scaling studies in 2-dimensions. The results presented here study the mechanism behind the magnetic field generation and growth, which is related to fluid vorticity generation by RTI. The magnetic field wraps around the bubbles and spikes and concentrates in flux bundles at the perturbed gas-ice interface where fluid vorticity is large. Additionally, the results of Srinivasan et al.[Phys. Rev. Lett. 108, 165002 (2012)] are described in greater detail. Additional scaling studies are performed to determine the growth of the self-generated magnetic field as a function of density, acceleration, perturbation wavelength, Atwood number, and ion mass.

  20. Simple method for the generation of multiple homogeneous field volumes inside the bore of superconducting magnets

    Science.gov (United States)

    Chou, Ching-Yu; Ferrage, Fabien; Aubert, Guy; Sakellariou, Dimitris

    2015-07-01

    Standard Magnetic Resonance magnets produce a single homogeneous field volume, where the analysis is performed. Nonetheless, several modern applications could benefit from the generation of multiple homogeneous field volumes along the axis and inside the bore of the magnet. In this communication, we propose a straightforward method using a combination of ring structures of permanent magnets in order to cancel the gradient of the stray field in a series of distinct volumes. These concepts were demonstrated numerically on an experimentally measured magnetic field profile. We discuss advantages and limitations of our method and present the key steps required for an experimental validation.

  1. Generation of a quasistationary magnetic field by intense electromagnetic radiation in a l;mited plasma

    International Nuclear Information System (INIS)

    The effect of plasma formation limitedness on space-time evolution of the generated quasi-stationary magnetic field in a plasma is discussed. The analysis is performed using the simplest two-dimensional case of uniform circular cylinder irradiated by a converging cylindrical wave. The magnetic field generation mechanism is related to electrons trapped by the HF-field of azimuthal harmonic excited in a plasma. It is shown that space-time evolution of magnetic field and its stationary value depend essentially on electric dimensions of a plasma formation and structure of incident HF-field

  2. External split field generator

    Science.gov (United States)

    Thundat, Thomas George (Knoxville, TN); Van Neste, Charles W. (Kingston, TN); Vass, Arpad Alexander (Oak Ridge, TN)

    2012-02-21

    A generator includes a coil disposed about a core. A first stationary magnetic field source may be disposed on a first end portion of the core and a second stationary magnetic field source may be disposed on a second end portion of core. The first and second stationary magnetic field sources apply a stationary magnetic field to the coil. An external magnetic field source may be disposed outside the coil to apply a moving magnetic field to the coil. Electrical energy is generated in response to an interaction between the coil, the moving magnetic field, and the stationary magnetic field.

  3. Generation of magnetic field on the accretion disk around a proto-first-star

    Energy Technology Data Exchange (ETDEWEB)

    Shiromoto, Yuki; Susa, Hajime [Department of Physics, Konan University, Kobe 658-8501 (Japan); Hosokawa, Takashi, E-mail: susa@konan-u.ac.jp [Department of Physics and Research Center for the Early Universe, The University of Tokyo, Tokyo 113-0033 (Japan)

    2014-02-20

    The generation process of a magnetic field around a proto-first-star is studied. Utilizing the recent numerical results of proto-first-star formation based on radiation hydrodynamics simulations, we assess the magnetic field strength generated by the radiative force and the Biermann battery effect. We find that a magnetic field of ?10{sup –9} G is generated on the surface of the accretion disk around the proto-first-star. The field strength on the accretion disk is smaller by two orders of magnitude than the critical value, above which the gravitational fragmentation of the disk is suppressed. Thus, the generated seed magnetic field hardly affect the dynamics of on-site first star formation directly, unless an efficient amplification process is taken into consideration. We also find that the generated magnetic field is continuously blown out from the disk on the outflows to the poles, that are driven by the thermal pressure of photoheated gas. The strength of the diffused magnetic field in low-density regions is ?10{sup –14}-10{sup –13} G at n {sub H} = 10{sup 3} cm{sup –3}, which could play an important role in the next generation star formation, as well as the seeds of the magnetic field in the present-day universe.

  4. Magnetic Field Generation and Zonal Flows in the Gas Giants

    Science.gov (United States)

    Duarte, L.; Wicht, J.; Gastine, T.

    2013-12-01

    The surface dynamics of Jupiter and Saturn is dominated by a banded system of fierce zonal winds. The depth of these winds remains unclear but they are thought to be confined to the very outer envelopes where hydrogen remains molecular and the electrical conductivity is negligible. The dynamo responsible for the dipole dominated magnetic fields of both Gas Giants, on the other hand, likely operates in the deeper interior where hydrogen assumes a metallic state. We present numerical simulations that attempt to model both the zonal winds and the interior dynamo action in an integrated approach. Using the anelastic version of the MHD code MagIC, we explore the effects of density stratification and radial electrical conductivity variations. The electrical conductivity is assumed to remain constant in the thicker inner metallic region and decays exponentially towards the outer boundary throughout the molecular envelope. Our results show that the combination of stronger density stratification (???55) and a weaker conducting outer layer is essential for reconciling dipole dominated dynamo action and a fierce equatorial zonal jet. Previous simulations with homogeneous electrical conductivity show that both are mutually exclusive, with solutions either having strong zonal winds and multipolar magnetic fields or weak zonal winds and dipole dominated magnetic fields. The particular setup explored here allows the equatorial jet to remain confined to the weaker conducting region where is does not interfere with the deeper seated dynamo action. The equatorial jet can afford to remain geostrophic and reaches throughout the whole shell. This is not an option for the additional mid to higher latitude jets, however. In dipole dominated dynamo solutions, appropriate for the Gas Giants, zonal flows remain very faint in the deeper dynamo region but increase in amplitude in the weakly conducting outer layer in some of our simulations. This suggests that the mid to high latitude jets observed on Jupiter and Saturn are a relatively shallow phenomenon remaining confined to the outer few percent in radius.

  5. Generation of Large-Scale Magnetic Fields from Dilaton Inflation in Noncommutative Spacetime

    OpenAIRE

    Bamba, Kazuharu; Yokoyama, J.

    2005-01-01

    Generation of large-scale magnetic fields is studied in dilaton electromagnetism in noncommutative inflationary cosmology, taking into account the effects of the spacetime uncertainty principle motivated by string theory. We show that it is possible to generate large-scale magnetic fields with sufficient strength to account for the observed fields in galaxies and clusters of galaxies through only adiabatic compression without dynamo amplification mechanism in models of power...

  6. Generation of Primordial Magnetic Fields on Linear Over-density Scales

    CERN Document Server

    Naoz, Smadar

    2013-01-01

    Magnetic fields appear to be present in all galaxies and galaxy clusters. Recent measurements indicate that a weak magnetic field may be present even in the smooth low density intergalactic medium. One explanation for these observations is that a seed magnetic field was generated by some unknown mechanism early in the life of the Universe, and was later amplified by various dynamos in nonlinear objects like galaxies and clusters. We show that a primordial magnetic field is expected to be generated in the early Universe on purely linear scales through vorticity induced by scale-dependent temperature fluctuations or equivalently, a spatially varying speed of sound of the gas. Residual free electrons left over after recombination tap into this vorticity to generate magnetic field via the Biermann battery process. Although the battery operates even in the absence of any relative velocity between dark matter and gas at the time of recombination, the presence of such a relative velocity modifies the predicted spati...

  7. Generation of large-scale magnetic fields by small-scale dynamo in shear flows

    CERN Document Server

    Squire, Jonathan

    2015-01-01

    We propose a new mechanism for turbulent mean-field dynamo in which the magnetic fluctuations resulting from a small-scale dynamo drive the generation of large-scale magnetic fields. This is in stark contrast to the common idea that small-scale magnetic fields should be harmful to large-scale dynamo action. These dynamos occur in the presence of large-scale velocity shear and do not require net helicity, resulting from off-diagonal components of the turbulent resistivity tensor as the magnetic analogue of the "shear-current" effect. Given the inevitable existence of non-helical small-scale magnetic fields in turbulent plasmas, as well as the generic nature of velocity shear, the suggested mechanism may help to explain generation of large-scale magnetic fields across a wide range of astrophysical objects.

  8. Generation of Large-Scale Magnetic Fields by Small-Scale Dynamo in Shear Flows

    Science.gov (United States)

    Squire, J.; Bhattacharjee, A.

    2015-10-01

    We propose a new mechanism for a turbulent mean-field dynamo in which the magnetic fluctuations resulting from a small-scale dynamo drive the generation of large-scale magnetic fields. This is in stark contrast to the common idea that small-scale magnetic fields should be harmful to large-scale dynamo action. These dynamos occur in the presence of a large-scale velocity shear and do not require net helicity, resulting from off-diagonal components of the turbulent resistivity tensor as the magnetic analogue of the "shear-current" effect. Given the inevitable existence of nonhelical small-scale magnetic fields in turbulent plasmas, as well as the generic nature of velocity shear, the suggested mechanism may help explain the generation of large-scale magnetic fields across a wide range of astrophysical objects.

  9. Generation of Large-Scale Magnetic Fields by Small-Scale Dynamo in Shear Flows.

    Science.gov (United States)

    Squire, J; Bhattacharjee, A

    2015-10-23

    We propose a new mechanism for a turbulent mean-field dynamo in which the magnetic fluctuations resulting from a small-scale dynamo drive the generation of large-scale magnetic fields. This is in stark contrast to the common idea that small-scale magnetic fields should be harmful to large-scale dynamo action. These dynamos occur in the presence of a large-scale velocity shear and do not require net helicity, resulting from off-diagonal components of the turbulent resistivity tensor as the magnetic analogue of the "shear-current" effect. Given the inevitable existence of nonhelical small-scale magnetic fields in turbulent plasmas, as well as the generic nature of velocity shear, the suggested mechanism may help explain the generation of large-scale magnetic fields across a wide range of astrophysical objects. PMID:26551120

  10. Magnetic field generation in core-sheath jets via the kinetic Kelvin-Helmholtz instability

    Energy Technology Data Exchange (ETDEWEB)

    Nishikawa, K.-I. [Department of Physics, University of Alabama in Huntsville, ZP12, Huntsville, AL 35899 (United States); Hardee, P. E. [Department of Physics and Astronomy, The University of Alabama, Tuscaloosa, AL 35487 (United States); Du?an, I. [Institute of Space Science, Atomistilor 409, Bucharest-Magurele RO-077125 (Romania); Niemiec, J. [Institute of Nuclear Physics PAN, ul. Radzikowskiego 152, 31-342 Kraków (Poland); Medvedev, M. [Department of Physics and Astronomy, University of Kansas, KS 66045 (United States); Mizuno, Y. [Institute of Astronomy, National Tsing-Hua University, Hsinchu, Taiwan 30013 (China); Meli, A. [Department of Physics and Astronomy, University of Gent, Proeftuinstraat 86 B-9000, Gent (Belgium); Sol, H. [LUTH, Observatore de Paris-Meudon, 5 place Jules Jansen, F-92195 Meudon Cedex (France); Zhang, B. [Department of Physics, University of Nevada, Las Vegas, NV 89154 (United States); Pohl, M. [Institut fur Physik und Astronomie, Universität Potsdam, D-14476 Potsdam-Golm (Germany); Hartmann, D. H., E-mail: ken-ichi.nishikawa@nasa.gov [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634 (United States)

    2014-09-20

    We have investigated magnetic field generation in velocity shears via the kinetic Kelvin-Helmholtz instability (kKHI) using a relativistic plasma jet core and stationary plasma sheath. Our three-dimensional particle-in-cell simulations consider plasma jet cores with Lorentz factors of 1.5, 5, and 15 for both electron-proton and electron-positron plasmas. For electron-proton plasmas, we find generation of strong large-scale DC currents and magnetic fields that extend over the entire shear surface and reach thicknesses of a few tens of electron skin depths. For electron-positron plasmas, we find generation of alternating currents and magnetic fields. Jet and sheath plasmas are accelerated across the shear surface in the strong magnetic fields generated by the kKHI. The mixing of jet and sheath plasmas generates a transverse structure similar to that produced by the Weibel instability.

  11. Effects of external magnetic field on harmonics generated in laser interaction with underdense plasma

    International Nuclear Information System (INIS)

    Complete text of publication follows. Generation of harmonic radiation is an important subject of laser plasma interaction and attracts great attention due to a wide range of applications. It has been seen that intense electromagnetic and quasi-static transverse magnetic fields are generated in laser plasma interaction. An extremely intense magnetic field (up to hundreds of MG) has been observed by experimental measurements in interaction of short laser pulses with plasma. These self-generated or applied magnetic fields affect the propagation of the laser pulses. In most laser interactions with homogeneous plasma, odd harmonics of laser frequency are generated. In this paper, we point out the possibility of even harmonics generation when a linearly polarized laser beam propagates in homogeneous plasma in the presence of a transverse magnetic field. It is shown that applying external field induces a transverse current density oscillating twice of the laser field which leds to generation of second harmonic radiation. This current density is derived using the perturbation method, and the steady state amplitude of the second harmonic obtained by solution of the wave equation. By the same procedure the current density and then the steady state amplitude of higher order harmonics are calculated. The efficiency of harmonic generation (the ratio of harmonic power to incident power) is a drastically function of the strength of external magnetic field. It is found that the efficiency of even harmonics is zero in the absence of magnetic field and increases as the magnetic field is increased. For odd harmonics, applying the external magnetic field enhances the generated harmonics as well. The conversion efficiency also increases with increase in plasma density and intensity of the laser beam.

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

    International Nuclear Information System (INIS)

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

  13. The role of rotation on the evolution of dynamo generated magnetic fields in Super Earths

    CERN Document Server

    Zuluaga, Jorge I

    2011-01-01

    Planetary magnetic fields could have a role on the evolution of planetary atmospheres and the required conditions for the emergence and evolution of life (habitability). After briefly review the current efforts to study the evolution of dynamo generated magnetic fields in massive earth-like rocky planets (Super Earths), we take the results from thermal evolution models and updated scaling laws for convection driven magnetodynamos to predict the evolution of the local Rossby number, the basic indicator of core magnetic field geometry and regime. We study the dependence of this property on planetary mass and rotation rate. Previous works have paid Attention only to the evolution of dipolar dominant core magnetic fields assuming rapid rotating planets. Here we extend these results including consistently the effects of rotation on the evolution of planetary magnetic field properties and obtain global constraints to the existence of intense protective magnetic fields in rapidly and slowly rotating Super Earths. We...

  14. Formulation of the spherical harmonic coefficients of the entire magnetic field components generated by magnetic moment and current for shimming

    Science.gov (United States)

    Noguchi, So

    2014-04-01

    For MRI and NMR magnet design, a highly homogeneous and high magnetic field has to be achieved by active and/or passive shimming. The active and passive shimming commonly homogenize the magnetic field around the magnet center by cancellation of the higher terms of a spherical harmonic series than the 0th term. So far, the spherical harmonic expression in the cylindrical coordinate system is well known for a circular coil, a solenoid coil, and magnetization of ferromagnetic material with/without its volume. In a shimming design, only the z-component of an inhomogeneous magnetic field is compensated because it is dominant to the performance of MRI/NMR. However, various kinds of MRI and NMR systems have recently been developed, and these magnets sometimes have an axially asymmetric configuration or generate a tilted magnetic field. Therefore, the entire x-, y-, and z-components have to be homogenized for such magnets. I derive the spherical harmonic expression of the entire components of magnetic field generated by a circular coil, a dipole coil, and a straight line current. In addition, since the entire magnetization components of the ferromagnetic material having the volume contribute the entire components of the magnetic field around the magnet center, I also derive the equations of the spherical harmonic coefficients of the magnetic field generated by ferromagnetic material. Since these equations need a numerical integration, such as the Gauss quadrature integration, the computation accuracy of the spherical harmonic coefficients is investigated against the number of the evaluation points. We can calculate the highly accurate spherical harmonic coefficients with the small number of the evaluation points.

  15. Evaluation of Human Exposure to Magnetic Fields Generated by Electric Power Systems in Complex Configurations

    OpenAIRE

    Kandia, Effrosyni

    2013-01-01

    The international growing concern for the human exposure to magnetic fields generated by electric power lines has unavoidably led to imposing legal limits. Respecting these limits, implies being able to calculate easily and accurately the generated magnetic field also in complex configurations. Twisting of phase conductors is such a case. The consolidated exact and approximated theory regarding a single-circuit twisted three-phase power cable line has been reported along with the proposal of ...

  16. Rayleigh-Taylor instability with self-generated magnetic field and thermal conduction in 2D

    International Nuclear Information System (INIS)

    High energy density laboratory experiments on Rayleigh-Taylor instability in nonlinear regime show the plasma behavior significantly different from classical simulation results. We include the effects of self-generated magnetic field and heat conduction in simulations aiming to improve agreement with experiments. We find maximum magnetic fields generated ?11MG (?=0.091) without heat conduction (k=0), field growth saturated by t=20ns; and ?1.7 MG with heat conduction taken into account. Strong magnetic fields in k=0 simulations affect flow dynamics, new modes are generated. Effect of weaker magnetic fields in simulations with physical values of k is insignificant; the main difference with classical RTI simulations is suppressed small scale features. In none of the simulations are mass extensions observed.

  17. Generation of Magnetic Field on the Accretion Disk around a Proto-First-Star

    CERN Document Server

    Shiromoto, Yuki; Hosokawa, Takashi

    2014-01-01

    The generation process of magnetic field around a proto-first-star is studied. Utilizing the recent numerical result of proto-first-star formation based upon the radiation hydrodynamics simulations, we assess the magnetic field strength generated by the radiative force and the Biermann battery effect. We find that magnetic field of \\sim 10^{-9} G is generated on the surface of the accretion disk around the proto-first-star. The field strength on the accretion disk is smaller by two orders of magnitude than the critical value, above which the gravitational fragmentation of the disk is suppressed. Thus, the generated seed magnetic field hardly affect the dynamics of on-site first star formation directly, unless efficient amplification process is taken into consideration. We also find that the generated magnetic field is continuously blown out from the disk on the outflows to the poles, that are driven by the thermal pressure of photoheated gas. The strength of the diffused magnetic field in low density regions ...

  18. Study of magnetic field expansion using a plasma generator for space radiation active protection

    International Nuclear Information System (INIS)

    There are many active protecting methods including Electrostatic Fields, Confined Magnetic Field, Unconfined Magnetic Field and Plasma Shielding etc. for defending the high-energy solar particle events (SPE) and Galactic Cosmic Rays (GCR) in deep space exploration. The concept of using cold plasma to expand a magnetic field is the best one of all possible methods so far. The magnetic field expansion caused by plasma can improve its protective efficiency of space particles. One kind of plasma generator has been developed and installed into the cylindrical permanent magnet in the eccentric. A plasma stream is produced using a helical-shaped antenna driven by a radio-frequency (RF) power supply of 13.56 MHz, which exits from both sides of the magnet and makes the magnetic field expand on one side. The discharging belts phenomenon is similar to the Earth's radiation belt, but the mechanism has yet to be understood. A magnetic probe is used to measure the magnetic field expansion distributions, and the results indicate that the magnetic field intensity increases under higher increments of the discharge power. (authors)

  19. A precise numerical estimation of the magnetic field generated around recombination

    CERN Document Server

    Fidler, Christian; Pitrou, Cyril

    2015-01-01

    We investigate the generation of magnetic fields from non-linear effects around recombination. As tight-coupling is gradually lost when approaching $z\\simeq 1100$, the velocity difference between photons and baryons starts to increase, leading to an increasing Compton drag of the photons on the electrons. The protons are then forced to follow the electrons due to the electric field created by the charge displacement; the same field, following Maxwell's laws, eventually induces a magnetic field on cosmological scales. Since scalar perturbations do not generate any magnetic field as they are curl-free, one has to resort to second-order perturbation theory to compute the magnetic field generated by this effect. We reinvestigate this problem numerically using the powerful second-order Boltzmann code SONG. We show that: i) all previous studies do not have a high enough angular resolution to reach a precise and consistent estimation of the magnetic field spectrum; ii) the magnetic field is generated up to $z\\simeq ...

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

    CERN Document Server

    Herndon, J Marvin

    2007-01-01

    One of the most fundamental problems in physics has been to understand the nature of the mechanism that generates the geomagnetic field and the magnetic fields of other planets and satellites. For decades, the dynamo mechanism, thought to be responsible for generating the geomagnetic field and other planetary magnetic fields, has been ascribed to convection in each planet's iron-alloy core. Recently, I described the problems inherent in Earth-core convection and proposed instead that the geomagnetic field is produced by convection in the electrically conductive, fluid, fission-product sub-shell of a natural nuclear fission reactor at the center of the Earth, called the georeactor. Here I set forth in detail the commonality in the Solar System of the matter like that of the inside of the Earth, which is my basis for generalizing the concept of planetary magnetic field generation by natural planetocentric nuclear fission reactors.

  1. Control of whistler radiation efficiency of a loop antenna by generation of ambient magnetic field irregularities

    International Nuclear Information System (INIS)

    Electrodynamic means for the control of loop antenna radiation efficiency in plasma is proposed, which can be used in the whistler frequency band. The method is based on the generation, without perturbing the plasma density, of localized ambient magnetic field irregularities in the vicinity of the antenna. In order to produce such irregularities, it is suggested to feed the antenna with additional dc current along with the rf current. Experiments performed in a large laboratory magnetoplasma showed that the generation of localized magnetic field enhancements provides the possibility of increasing the amplitude of the whistlers emitted by the loop antenna. Moreover, experiments have shown that the amplification of the whistlers' signals from the receiving loop antenna fed with additional dc current is observed when a static magnetic field enhancement is generated in the vicinity of the receiver. The experimental data are in good agreement with the theoretical results obtained for comparatively weak ambient magnetic field perturbations

  2. Generation of Vortex Beams with Strong Longitudinally Polarized Magnetic Field by Using a Metasurface

    CERN Document Server

    Veysi, Mehdi; Capolino, Filippo

    2014-01-01

    A novel method of generation and synthesis of azimuthally E-polarized vortex beams is presented. Along the axis of propagation such beams have a strong longitudinally polarized magnetic field where ideally there is no electric field. We show how these beams can be constructed through the interference of Laguerre-Gaussian beams carrying orbital angular momentum. As an example, we present a metasurface made of double-split ring slot pairs and report a good agreement between simulated and analytical results. Both a high magnetic-to-electric-field contrast ratio and a magnetic field enhancement are achieved. We also investigate the metasurface physical constraints to convert a linearly polarized beam into an azimuthally E- polarized beam and characterize the performance of magnetic field enhancement and electric field suppression of a realistic metasurface. These findings are potentially useful for novel optical spectroscopy related to magnetic dipolar transitions and for optical manipulation of particles with sp...

  3. Laser generated wake fields as a new diagnostic tool for magnetized plasmas

    CERN Document Server

    Servin, M; Servin, Martin; Brodin, Gert

    2000-01-01

    In the presence of an external magnetic field, wake fields generated by a short laser pulse can propagate out of the plasma, and thereby provide information about the electron density profile. A method for reconstructing the density profile from a measured wake field spectrum is proposed and a numerical example is given. Finally, we compare our proposal with existing plasma density diagnostic techniques.

  4. Chiral imbalance evolution in dense matter and the generation of magnetic fields in magnetars

    CERN Document Server

    Dvornikov, Maxim

    2015-01-01

    We study the model for the magnetic field generation in a magnetar based on the magnetic field instability driven by the parity violating electroweak interaction between electrons and nucleons in the neutron star matter. Using the quantum field theory methods, we calculate the helicity flip of an electron scattering off protons in dense matter of a neutron star. The influence of the electroweak interaction between electrons and background nucleons on the helicity flip is examined. We also derive the kinetic equation for the chiral imbalance. The evolution of the magnetic field in a magnetar accounting for the correct value of the helicity flip rate is studied.

  5. The generation of magnetic fields in astrophysical bodies. X. Magnetic buoyancy and the solar dynamo

    International Nuclear Information System (INIS)

    The magnetic field appearing as bipolar magnetic regions at the surface of the Sun represents the lines of force from a general azimuthal field of the order of 102 gauss somewhere beneath the surface. The amplification time, as a consequence of the nonuniform rotation, is of the order of 10 years. But magnetic buoyancy brings the azimuthal field up through much of the convective zone in a time rather less than 10 years, raising the question of where the azimuthal field can be retained long enough to be amplified

  6. Evolution of magnetic field generated by the Kelvin-Helmholtz instability

    CERN Document Server

    Modestov, Mikhail; Brodin, Gert; Marklund, Mattias; Brandenburg, Axel

    2014-01-01

    The Kelvin-Helmholtz instability in an ionized plasma is considered with a focus on the generation of magnetic field via the Biermann battery mechanisms. The problem is studied through direct numerical simulations of two counter-directed flows in 2D geometry. The simulations demonstrate the formation of eddies and their further interaction resulting in a large single vortex. At early stages, the generated magnetic field evolves due to the baroclinic term in the induction equation, revealing significantly different structures from the vorticity field, despite the fact that magnetic field and vorticity obey identical equations. At later times, the magnetic field exhibits complex behavior and continues to grow even after a hydrodynamic vortex has developed.

  7. Magnetic field seed generation in plasmas around charged and rotating black holes

    International Nuclear Information System (INIS)

    Previous work by the authors introduced the possibility of generating seed magnetic fields by spacetime curvature and applied it in the vicinity of a Schwarzschild black hole. It was pointed out that it would be worthwhile to consider the effect in other background geometries and particularly in the vicinity of a rotating black hole, which is generically to be expected, astrophysically. In this paper that suggestion is followed up and we calculate generated magnetic field seed due to Reissner–Nördstrom and Kerr spacetimes. The conditions for the drive for the seed of a magnetic field is obtained for charged black holes, finding that in the horizon the drive vanishes. Also, the ?N-force produced by the Kerr black hole is obtained and its relation with the magnetic field seed is discussed, producing a more effective drive. (paper)

  8. Design of pulsed guiding magnetic field for high power microwave generators

    International Nuclear Information System (INIS)

    In this paper, we present a comprehensive study on designing solenoid together with the corresponding power supply system to excite pulsed magnetic field required for high power microwave generators. Particularly, a solenoid is designed and the excited magnetic field is applied to a Ku-band overmoded Cerenkov generator. It is found in experiment that the electron beam is properly guided by the magnetic field and a 1.1 GW high power microwave is achieved at a central frequency of 13.76 GHz. Pulsed solenoid system has the advantages of compactness and low energy consumption, which are of great interest for repetitive operation. The reported studies and results can be generalized to other applications which require magnetic fields

  9. Generation and Properties of Large-Scale Non-axisymmetric Magnetic Fields by Solar Dynamo

    Science.gov (United States)

    Pipin, Valery; Kosovichev, Alexander

    2015-08-01

    Large-scale non-axisymmetric magnetic fields generated by the solar dynamo, and presumably responsible for the phenomenon of "active longitudes", play an important role in the distribution of solar activity and flares. By calculating 3D mean-field dynamo models, we show that nonlinear coupling between axisymmetric and non-axisymmetric modes, e.g. due to the magnetic feedback on the alpha-effect (see, e.g., [1]), can maintain a large-scale non-axisymmetric dynamo process. Non-axisymmetric random fluctuations of dynamo parameters can be another source for the non-axisymmetric magnetic fields on the Sun. Such fluctuations can provide a mechanism of the magnetic energy transfer from the global field to the non-axisymmetric modes. It is shown that the rotational periods of the non-axisymmetric field correspond to the dynamo process operating in the subsurface shear layer which is located in the range of depths 0.85-0.95R. We find that the magnetic helicity conservation quenches generation of the non-axisymmetric dynamo modes as well as it does for the axisymmetric dynamo. It is concluded that the 3D mean-field non-axisymmetric dynamo models can potentially explain the observed distribution of the solar magnetic activity.1. Moss, D.,Non-axisymmetric solar magnetic fields, 1999, MNRAS, 306, 300On 3/18/2015 2:29 PM, Valery Pipin wrote:

  10. Can the turbulent galactic dynamo generate large-scale magnetic fields?

    OpenAIRE

    K.Subramanian

    1997-01-01

    Large-scale magnetic fields in galaxies are thought to be generated by a turbulent dynamo. However the same turbulence also leads to a small-scale dynamo which generates magnetic noise at a more rapid rate. The efficiency of the large-scale dynamo depends on how this noise saturates. We examine this issue taking into account ambipolar drift, which obtains in a galaxy with significant neutral gas. We argue that, (1) the small-scale dynamo generated field does not fill the vol...

  11. Generation of large-scale magnetic fields by small-scale dynamo in shear flows

    OpenAIRE

    Squire, Jonathan; Bhattacharjee, Amitava

    2015-01-01

    We propose a new mechanism for turbulent mean-field dynamo in which the magnetic fluctuations resulting from a small-scale dynamo drive the generation of large-scale magnetic fields. This is in stark contrast to the common idea that small-scale magnetic fields should be harmful to large-scale dynamo action. These dynamos occur in the presence of large-scale velocity shear and do not require net helicity, resulting from off-diagonal components of the turbulent resistivity ten...

  12. Generation of low-frequency electric and magnetic fields during large- scale chemical and nuclear explosions

    Energy Technology Data Exchange (ETDEWEB)

    Adushkin, V.V. [Academy of Sciences, Moscow (Russian Federation). Inst. for Dynamics of the Geospheres; Dubinya, V.A.; Karaseva, V.A.; Soloviev, S.P.; Surkov, V.V. [Lawrence Livermore National Lab., CA (United States)

    1995-06-01

    We discuss the main parameters of the electric field in the surface layer of the atmosphere and the results of the investigations of the natural electric field variations. Experimental investigations of the electromagnetic field for explosions in air are presented. Electromagnetic signals generated by underground nuclear and chemical explosions are discussed and explosions for 1976--1991 are listed. Long term anomalies of the earth`s electromagnetic field in the vicinity of underground explosions were also investigated. Study of the phenomenon of the irreversible shock magnetization showed that in the zone nearest to the explosion the quasistatic magnetic field decreases in inverse proportion to the distance.

  13. GENERATION OF A SEED MAGNETIC FIELD AROUND FIRST STARS: THE BIERMANN BATTERY EFFECT

    International Nuclear Information System (INIS)

    We investigate the generation processes of magnetic fields around first stars. Since first stars are expected to form anisotropic ionization fronts in the surrounding clumpy media, magnetic fields are generated by the effects of radiation force, as well as the Biermann battery effect. We calculated the amplitude of the magnetic field generated by the effects of radiation force around the first stars in a preceding paper but the Biermann battery effects were not taken into account. In this paper, we calculate the generation of magnetic fields by the Biermann battery effect as well as the effects of radiation force, utilizing radiation hydrodynamics simulations. As a result, we find that the generated magnetic field strengths are ?10–19 G – 10–17 G at ?100 pc-1 kpc scale, an order of magnitude larger than the results of our previous study mainly as a result of the Biermann battery effect. We also find that this result is insensitive to various physical parameters including the mass of the source star and the distance between the source and the dense clump, unless we take unlikely values of these parameters.

  14. Generation of Seed Magnetic Field around First Stars: the Biermann Battery Effect

    CERN Document Server

    Doi, Kentaro

    2011-01-01

    We investigate generation processes of magnetic fields around first stars. Since the first stars are expected to form anisotropic ionization fronts in the surrounding clumpy media, magnetic fields are generated by effects of radiation force as well as the Biermann battery effect. We have calculated the amplitude of magnetic field generated by the effects of radiation force around the first stars in the preceding paper, in which the Biermann battery effects are not taken into account.In this paper, we calculate the generation of magnetic fields by the Biermann battery effect as well as the effects of radiation force, utilizing the radiation hydrodynamics simulations. As a result, we find that the generated magnetic field strengths are ~ 10^{-19}G-10^{-17}G at ~ 100pc-1kpc scale mainly by the Biermann battery, which is an order of magnitude larger than the results of our previous study. We also find that this result is insensitive to various physical parameters including the mass of the source star, distance be...

  15. Chaotic dynamics of the magnetic field generated by dynamo action in a turbulent flow

    International Nuclear Information System (INIS)

    We present models related to the results of a recent experiment (the 'VKS experiment') showing the generation of a magnetic field by a fully turbulent flow of liquid sodium. We first discuss the geometry of the mean magnetic field when the two coaxial impellers driving the flow counter-rotate at the same frequency. We then show how we expect this geometry to be modified when the impellers rotate at different frequencies. We also show that, in the latter case, dynamical regimes of the magnetic field can be easily understood from the interaction of modes with dipolar (respectively quadrupolar) symmetry. In particular, this interaction generates magnetic field reversals that have been observed in the experiment and display a hierarchy of timescales similar to the Earth's magnetic field: the duration of the steady phases is widely distributed, but is always much longer than the time needed to switch polarity. In addition to reversals, several other large scale features of the generated magnetic field are obtained when varying the governing parameters of the flow. These results are also understood in the framework of the same model.

  16. High magnetic field multipoles generated by superconductor magnetization within a set of nested superconducting correction coils

    International Nuclear Information System (INIS)

    Correction elements in colliding beam accelerators such as the SSC can be the source of undesirable higher magnetic field multipoles due to magnetization of the superconductor within the corrector. Quadrupole and sextupole correctors located within the main dipole will produce sextupole and decapole due to magnetization of the superconductor within the correction coils. Lumped nested correction coils can produce a large number of skew and normal magnetization multipoles which may have an adverse effect on a stored beam at injection into a high energy colliding beam machine such as the SSC. 6 refs., 2 figs., 2 tabs

  17. Novel layout of a bi-metallic nanoring for magnetic field pulse generation from light

    International Nuclear Information System (INIS)

    Recently Tsiatmas et al proposed using a nanoring made of two different metallic sectors to generate a magnetic pulse from a laser pulse [1]. Non-uniform heating of the ring creates very large temperature gradients, which drive thermoelectric currents, and this creates a localized magnetic field. However, heat from the laser pulse may result in the melting of the nanoring. We propose a symmetric structure made of four metallic sectors, which results in a higher magnetic field generation together with a lower lattice temperature. We also show that the magnetic field depends strongly on the size of the metallic sectors and interpret the results with the help of the electromotive forces, the overall ring resistance, and Biot–Savart law. (paper)

  18. Analysis of the Magnetic Field Effect on Entropy Generation at Thermosolutal Convection in a Square Cavity

    Directory of Open Access Journals (Sweden)

    Ammar Ben Brahim

    2011-05-01

    Full Text Available Thermosolutal convection in a square cavity filled with air and submitted to an inclined magnetic field is investigated numerically. The cavity is heated and cooled along the active walls with a mass gradient whereas the two other walls of the cavity are adiabatic and insulated. Entropy generation due to heat and mass transfer, fluid friction and magnetic effect has been determined in transient state for laminar flow by solving numerically the continuity, momentum energy and mass balance equations, using a Control Volume Finite—Element Method. The structure of the studied flows depends on four dimensionless parameters which are the Grashof number, the buoyancy ratio, the Hartman number and the inclination angle. The results show that the magnetic field parameter has a retarding effect on the flow in the cavity and this lead to a decrease of entropy generation, Temperature and concentration decrease with increasing value of the magnetic field parameter.

  19. Generation of strong magnetic field using 60 mm circle superconducting bulk magnet and its application to magnetron sputtering device

    International Nuclear Information System (INIS)

    To make a practical application of a superconducting bulk magnet (SBM), it is necessary that the SBM generates a strong and stable magnetic field in a working space and the magnet can be handled without any special care that would be needed because of the use of a superconductor. To satisfy these requirements, we have designed a portable and user-friendly magnet system consisting of a small air-cooled type refrigerator and a bulk superconductor. By using the stress-controlling magnetization technique, we could achieve a magnetic flux density of 8.0 T on the bulk surface and 6.5 T over the vacuum chamber surface of the refrigerator, when a 60 mm circle Gd-Ba-Cu-O bulk superconductor reinforced with a 5 mm thick stainless steel ring was magnetized by field cooling in 8.5 T to 27 K. We have confirmed that the bulk magnet system coupled with a battery is quite portable and can be delivered to any location by using a car with an electric power outlet in the cabin. We have constructed a magnetron sputtering device that employs a bulk magnet system delivered from the place of magnetization by this method. This sputtering device exhibits several unique features such as deposition at a very low Ar gas pressure because the magnetic field is 20 times stronger than that obtained by a conventional device in the working space

  20. Experimental and theoretical study of helical explosive electrical current generators with magnetic field compression

    International Nuclear Information System (INIS)

    A generator of electrical energy in which magnetic field compression is achieved by a solid explosive is described. The magnetic flux losses have been calculated for generators of various configurations by the skin depth concept. Calculations take the Joule heating of conductors into account. In helical generators the magnetic flux losses are higher than those calculated by considering diffusion only. Additional losses approximately as important as diffusion losses have already been observed elsewhere on similar devices. Detailed calculations of the motion of the explosively driven inner conductor show that losses come from the jumps encountered by sliding contact moving along the helix. The jumps are caused by little geometrical defects and the consequence on losses is strongly dependent on current intensity. The jumps decrease when the pitch of helix increases. The jumps are detrimental to the efficient use of the explosive energy. With helical generators only 5% of the energy is transferred into magnetic energy

  1. Modeling of High Density and Strong Magnetic Field Generation by Plasma Jet Compression

    International Nuclear Information System (INIS)

    Full text: The main topic is the generation of dense magnetized plasmas and ultra-strong magnetic field for fusion. The principal theoretical result is a demonstration of the feasibility of electromagnetic-driven spherical liner implosions in the cm/?s regime. The field reversed configuration (FRC) and the cusp geometry of the magnetic field (antiprobkotron) are alternate systems with attractive prospects. Preferable choice of plasma confinement in magnetic device may be combined with properties of inertial confinement. The main aim of this work is physical analysis of high temperature plasma (target) confined by magnetic field with taking into account plasma guns (liner) to push and compress plasma of compact configuration. This study points to solution of problem connected with theoretical investigation of methods supplying with magneto inertial fusion (MIF). We consider the value corresponding to the equality of the plasma pressure to the magnetic pressure as the effective magnetic field. Numerical calculation of temporal evolution of the particle balance and plasma power balance were performed to define the minimal requirements for magnetic field on the final stage of the compression. The results show for most prospective regimes minimum effective values B ? 300 T are needed. Results of numerical simulation are presented. This work was supported by Russian Foundation for Basic Research (Project 09-08-00137a) and the U.S. Civilian Research and Development Foundation (CRDF) and the Russian Foundation for Basic Research (RFBR) Cooperative Grants Program (Project 10-08-92500IK). (author)

  2. Effect of transverse magnetic field on generation of electron beam in gas diode

    International Nuclear Information System (INIS)

    One studied experimentally the effect of the transverse magnetic field (0.08 and 0.016 T) on the generation of an electron beam within a gas diode. At U=25 kV gas diode voltage and helium low pressure (45 Torr) the transverse magnetic field is shown to affect the beam current amplitude outside the foil and on its foil cross section distribution. Under the increased pressure values and at generation of an ultra short-time avalanche electron beam (UAEB) in helium, nitrogen and in air the transverse magnetic field is shown to affect negligibly the UAEB amplitude and duration outside the foil. At the generator voltage equal to hundreds of kilovolts a portion of the escaping electrons was found to arrive to the gas diode lateral walls including those from the discharge plasma in the vicinity of a cathode

  3. Generation of a spin-polarized electron beam by multipole magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, Ebrahim, E-mail: ekarimi@uottawa.ca [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada); Grillo, Vincenzo [CNR-Istituto Nanoscienze, Centro S3, Via G Campi 213/a, I-41125 Modena (Italy); Boyd, Robert W. [Department of Physics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, Canada K1N 6N5 (Canada); Institute of Optics, University of Rochester, Rochester, NY 14627 (United States); Santamato, Enrico [Dipartimento di Scienze Fisiche, Università di Napoli “Federico II”, Compl. Univ. di Monte S. Angelo, 80126 Napoli (Italy); Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia, Napoli (Italy)

    2014-03-01

    The propagation of an electron beam in the presence of transverse magnetic fields possessing integer topological charges is presented. The spin–magnetic interaction introduces a nonuniform spin precession of the electrons that gains a space-variant geometrical phase in the transverse plane proportional to the field's topological charge, whose handedness depends on the input electron's spin state. A combination of our proposed device with an electron orbital angular momentum sorter can be utilized as a spin-filter of electron beams in a mid-energy range. We examine these two different configurations of a partial spin-filter generator numerically. The results of this analysis could prove useful in the design of an improved electron microscope. - Highlights: • Theory of generating spin-polarized electron beams. • Interacting electron vortex beams with space-variant magnetic fields. • Bohr–Pauli impossibility of generating spin-polarized free electrons.

  4. Measurements of Self-Generated Magnetic Fields Influence on Electron Heat Conduction in Dense Plasmas

    International Nuclear Information System (INIS)

    Proton radiography measurements of self generated magnetic fields developing in long pulse (ns), high-power laser plasma interactions were employed to investigate the influence of these fields on the propagation of heat flow in dense plasmas. During the experiments, the heat wave propagation speed was measured simultaneously with the fields. These two coupled measurements could give an insight on the limitations of current numerical models of heat transport. They suggest that non locality of heat transport and diffusion of magnetic fields are important to model correctly the interaction.

  5. Theory and experimental show up of axial magnetic fields self-generated in dense laser-produced plasmas

    International Nuclear Information System (INIS)

    The work presented in this thesis concerns the magnetic fields generated in laser produced plasma. A summary of the theoretical and experimental studies concerning the toroidal magnetic fields and realised by different groups of research is presented. Then, we present our original contribution on the generation of axial magnetic fields by the dynamo effect. The experimental work for the detection of magnetic field is based on the Faraday rotation and Zeeman effects. The experimental diagrams are detailed and discussed. The experimental results are presented and compared to the theory. Finaly, we present some consequences of the generation of the axial magnetic fields in laser produced plasma as a discussion of the thermal conductivity

  6. Magnetic field generation by the Weibel instability at temperature gradients in collisionless plasmas

    OpenAIRE

    Fujita, Yutaka; Kato, Tsunehiko N.; Okabe, Nobuhiro

    2006-01-01

    The Weibel instability could be responsible for the generation of magnetic fields in various objects such as gamma-ray bursts, jets from active galactic nuclei, and clusters of galaxies. Using numerical simulations, the development of the Weibel instability at a temperature gradient is studied. It is found that current sheets are first generated at the gradient, and then they are rounded off and turn into current filaments. During this process, return currents are generated ...

  7. Development of FEMAG. Calculation code of magnetic field generated by ferritic plates in the tokamak devices

    Energy Technology Data Exchange (ETDEWEB)

    Urata, Kazuhiro [Japan Atomic Energy Research Inst., Naka, Ibaraki (Japan). Naka Fusion Research Establishment

    2003-03-01

    In design of the future fusion devises in which low activation ferritic steel is planned to use as the plasma facing material and/or the inserts for ripple reduction, the appreciation of the error field effect against the plasma as well as the optimization of ferritic plate arrangement to reduce the toroidal field ripple require calculation of magnetic field generated by ferritic steel. However iterative calculations concerning the non-linearity in B-H curve of ferritic steel disturbs high-speed calculation required as the design tool. In the strong toroidal magnetic field that is characteristic in the tokamak fusion devices, fully magnetic saturation of ferritic steel occurs. Hence a distribution of magnetic charges as magnetic field source is determined straightforward and any iteration calculation are unnecessary. Additionally objective ferritic steel geometry is limited to the thin plate and ferritic plates are installed along the toroidal magnetic field. Taking these special conditions into account, high-speed calculation code ''FEMAG'' has been developed. In this report, the formalization of 'FEMAG' code, how to use 'FEMAG', and the validity check of 'FEMAG' in comparison with a 3D FEM code, with the measurements of the magnetic field in JFT-2M are described. The presented examples are numerical results of design studies for JT-60 modification. (author)

  8. Electron-scale shear instabilities: magnetic field generation and particle acceleration in astrophysical jets

    CERN Document Server

    Alves, E P; Fonseca, R A; Silva, L O

    2014-01-01

    Strong shear flow regions found in astrophysical jets are shown to be important dissipation regions, where the shear flow kinetic energy is converted into electric and magnetic field energy via shear instabilities. The emergence of these self-consistent fields make shear flows significant sites for radiation emission and particle acceleration. We focus on electron-scale instabilities, namely the collisionless, unmagnetized Kelvin-Helmholtz instability (KHI) and a large-scale dc magnetic field generation mechanism on the electron scales. We show that these processes are important candidates to generate magnetic fields in the presence of strong velocity shears, which may naturally originate in energetic matter outburst of active galactic nuclei and gamma-ray bursters. We show that the KHI is robust to density jumps between shearing flows, thus operating in various scenarios with different density contrasts. Multidimensional particle-in-cell (PIC) simulations of the KHI, performed with OSIRIS, reveal the emergen...

  9. Magnetic field generation and evolution in high-energy-density plasmas

    Science.gov (United States)

    Moissard, C.; Deng, W.; Fox, W.; Bhattacharjee, A.

    2014-10-01

    Magnetic reconnection has been proposed to account for many astrophysical phenomena and is inferred to play an important role in fusion. Recent experiments have studied magnetic reconnection in high-energy-density (HED) plasmas at the Vulcan, Omega and Shenguang laser facilities. Plasma bubbles are created by laser irradiation of solid targets. These bubbles self-generate MG-scale magnetic fields, and the collision of pairs of bubbles drives reconnection of this magnetic field. 2D first principles particle-in-cell (PIC) simulations with a collision operator have been used to study the evolution of the magnetic field in these experiments. The ablation of the target is modeled by a Gaussian heating function acting on an initially cold, high density plasma. It is shown that the Biermann battery effect (?T × ?n in generalized Ohm's law) can account quantitatively for the magnetic field produced. However, special attention must be given to the temperature, which can no longer be considered as a scalar in the regime of the experiments. In simulations with a collision operator, the evolution of the magnetic field is compared to Braginskii's transport theory. Results of 3D simulations of magnetic reconnection with the self-consistent Biermann effect will be reported.

  10. The new TORPEX in-vessel toroidal conductor for the generation of a poloidal magnetic field

    International Nuclear Information System (INIS)

    TORoidal Plasma EXperiment (TORPEX) is a Simple Magnetized Torus featuring open helical magnetic field lines obtained from the superposition of a small vertical component on the main toroidal field. This work introduces the experimental setup developed to include a poloidal magnetic field. The toroidal and poloidal fields generate a rotational transform, making the magnetic geometry of TORPEX closer to that of a tokamak. This upgrade opens the possibility to deal with closed and open flux surfaces, as well as with the transition region across the last closed flux surface. The main technical solutions are discussed together with the physical considerations at the basis of the system design. Selected examples of the magnetic configurations accessible with the set of magnetic field coils available on TORPEX are discussed, ranging from single-null X-points to magnetic snowflakes. The simplest magnetic configuration of quasi-circular concentric flux surfaces is tested experimentally. Measurements of the two-dimensional electron plasma density profiles and the particle confinement time are presented, together with the first steps towards the understanding of plasma production mechanisms

  11. Magnetic fields in cosmology

    OpenAIRE

    Dolgov, A. D.

    2003-01-01

    Different mechanisms which may possibly explain existence of magnetic fields on astronomically large scales are described. A recently suggested model of magnetic fields generation slightly before hydrogen recombination is discussed in more detail.

  12. Performance of a Cylindrical Hall-Effect Thruster with Magnetic Field Generated by Permanent Magnets

    Science.gov (United States)

    Polzin, Kurt A.; Raitses, Yevgeny; Fisch, Nathaniel J.

    2008-01-01

    While Hall thrusters can operate at high efficiency at kW power levels, it is difficult to construct one that operates over a broad envelope down to 100W while maintaining an efficiency of 45- 55%. Scaling to low power while holding the main dimensionless parameters constant requires a decrease in the thruster channel size and an increase in the magnetic field strength. Increasing the magnetic field becomes technically challenging since the field can saturate the miniaturized inner components of the magnetic circuit and scaling down the magnetic circuit leaves very little room for magnetic pole pieces and heat shields. An alternative approach is to employ a cylindrical Hall thruster (CHT) geometry. Laboratory model CHTs have operated at power levels ranging from the order of 50 Watts up to 1 kW. These thrusters exhibit performance characteristics which are comparable to conventional, annular Hall thrusters of similar size. Compared to the annular Hall thruster, the CHT has a lower insulator surface area to discharge chamber volume ratio. Consequently, there is the potential for reduced wall losses in the channel of a CHT, and any reduction in wall losses should translate into lower channel heating rates and reduced erosion. This makes the CHT geometry promising for low-power applications. Recently, a CHT that uses permanent magnets to produce the magnetic field topology was tested. This thruster has the promise of reduced power consumption over previous CHT iterations that employed electromagnets. Data are presented for two purposes: to expose the effect different controllable parameters have on the discharge and to summarize performance measurements (thrust, Isp, efficiency) obtained using a thrust stand. These data are used to gain insight into the thruster's operation and to allow for quantitative comparisons between the permanent magnet CHT and the electromagnet CHT.

  13. Generation of magnetic field and electrostatic shock wave driven by counterstreaming pair plasmas

    International Nuclear Information System (INIS)

    By using a two-dimensional (2D) relativistic fully electromagnetic particle-in-cell code, the interaction process of counterstreaming pair (electron-positron) plasmas is investigated. The counterstreaming plasmas become unstable against the collisionless electromagnetic counterstreaming instability, similar to the Weibel instability. In the linear phase, magnetic and electric fields with the scale of skin depth size are generated through the electromagnetic counterstreaming instability. The behavior of plasma in the nonlinear phase is also made clear. The small-scale magnetic fields coalesce with each other, merging through the inverse cascade process which occurs characteristically in 2D dynamics, and change into larger unit. The large-scale magnetic fields propagate more slowly than the initial plasma flow as a low-frequency wave. Behind the magnetic fields, plasmas are isotropically heated by the mixing of counterstreaming plasmas. On the other hand, the electric fields propagate the same as the initial plasma flow. Ahead of the generated magnetic fields, the electric field component along the stream is amplified through the electrostatic counterstreaming instability and the electrostatic shock waves are formed. High-energy particles are also produced from the electrostatic shocks. These simulation results may be applied to the synchrotron gamma-ray burst model

  14. Device for generating toroidal magnetic fields in torus type thermonuclear device

    International Nuclear Information System (INIS)

    Purpose: To obtain a toroidal magnetic field generation device which is simple in structure, capable of accurately mounting toroidal coils and in excellent in durability. Constitution: In a device for generating toroidal magnetic field of tokamak type thermonuclear device, each of the magnet coils support frames made of non-magnetic copper or the like is firmly assembled with a lower support and an upper support and a connection member so as to support the coils withstanding the own weight of the coils, thermal stress and centripetal force, and the both of the inner sides of each support frame at the center is formed with wedge surfaces. Retention rings are firmly fitted to the projections at the lower and the upper portions of the support frames and accurately assembled into the support frames to thereby transmit the centripetal force to the wedge surfaces to receive the withstanding force. (Horiuchi, T.)

  15. Preliminary Results of Performance Measurements on a Cylindrical Hall-Effect Thruster with Magnetic Field Generated by Permanent Magnets

    Science.gov (United States)

    Polzin, K. A.; Raitses, Y.; Merino, E.; Fisch, N. J.

    2008-01-01

    The performance of a low-power cylindrical Hall thruster, which more readily lends itself to miniaturization and low-power operation than a conventional (annular) Hall thruster, was measured using a planar plasma probe and a thrust stand. The field in the cylindrical thruster was produced using permanent magnets, promising a power reduction over previous cylindrical thruster iterations that employed electromagnets to generate the required magnetic field topology. Two sets of ring-shaped permanent magnets are used, and two different field configurations can be produced by reorienting the poles of one magnet relative to the other. A plasma probe measuring ion flux in the plume is used to estimate the current utilization for the two magnetic configurations. The measurements indicate that electron transport is impeded much more effectively in one configuration, implying a higher thrust efficiency. Preliminary thruster performance measurements on this configuration were obtained over a power range of 100-250 W. The thrust levels over this power range were 3.5-6.5 mN, with anode efficiencies and specific impulses spanning 14-19% and 875- 1425 s, respectively. The magnetic field in the thruster was lower for the thrust measurements than the plasma probe measurements due to heating and weakening of the permanent magnets, reducing the maximum field strength from 2 kG to roughly 750-800 G. The discharge current levels observed during thrust stand testing were anomalously high compared to those levels measured in previous experiments with this thruster.

  16. Efficient gradient field generation providing a multi-dimensional arbitrary shifted field-free point for magnetic particle imaging

    Energy Technology Data Exchange (ETDEWEB)

    Kaethner, Christian, E-mail: kaethner@imt.uni-luebeck.de; Ahlborg, Mandy; Buzug, Thorsten M., E-mail: buzug@imt.uni-luebeck.de [Institute of Medical Engineering, Universität zu Lübeck, 23562 Lübeck (Germany); Knopp, Tobias [Thorlabs GmbH, 23562 Lübeck (Germany); Sattel, Timo F. [Philips Medical Systems DMC GmbH, 22335 Hamburg (Germany)

    2014-01-28

    Magnetic Particle Imaging (MPI) is a tomographic imaging modality capable to visualize tracers using magnetic fields. A high magnetic gradient strength is mandatory, to achieve a reasonable image quality. Therefore, a power optimization of the coil configuration is essential. In order to realize a multi-dimensional efficient gradient field generator, the following improvements compared to conventionally used Maxwell coil configurations are proposed: (i) curved rectangular coils, (ii) interleaved coils, and (iii) multi-layered coils. Combining these adaptions results in total power reduction of three orders of magnitude, which is an essential step for the feasibility of building full-body human MPI scanners.

  17. Generation and subwavelength focusing of longitudinal magnetic fields in a metallized fiber tip

    Science.gov (United States)

    Ploss, Daniel; Kriesch, Arian; Pfeifer, Hannes; Banzer, Peter; Peschel, Ulf

    2014-06-01

    We demonstrate experimentally and numerically that in fiber tips as they are used in NSOMs azimuthally polarized electrical fields (|E$_{\\text{azi}}$|$^2$/|E$_{\\text{tot}}$|$^2$ $\\approx$ 55% $\\pm $ 5% for 1.4\\mu m tip aperture diameter and \\lambda$_0$ = 1550nm), respectively subwavelength confined (FWHM $\\approx$ 450nm $\\approx$ \\lambda$_0$/3.5) magnetic fields, are generated for a certain tip aperture diameter (d = 1.4\\mu m). We attribute the generation of this field distribution in metal-coated fiber tips to symmetry breaking in the bend and subsequent plasmonic mode filtering in the truncated conical taper.

  18. Ocean circulation generated magnetic signals

    DEFF Research Database (Denmark)

    Manoj, C.; Kuvshinov, A.; Maus, S.; Luhr, H.

    2006-01-01

    Conducting ocean water, as it flows through the Earth's magnetic field, generates secondary electric and magnetic fields. An assessment of the ocean-generated magnetic fields and their detectability may be of importance for geomagnetism and oceanography. Motivated by the clear identification of ocean tidal signatures in the CHAMP magnetic field data we estimate the ocean magnetic signals of steady flow using a global 3-D EM numerical solution. The required velocity data are from the ECCO ocean c...

  19. Impact of magnetic field parameters and iron oxide nanoparticle properties on heat generation for use in magnetic hyperthermia

    Science.gov (United States)

    Shah, Rhythm R.; Davis, Todd P.; Glover, Amanda L.; Nikles, David E.; Brazel, Christopher S.

    2015-08-01

    Heating of nanoparticles (NPs) using an AC magnetic field depends on several factors, and optimization of these parameters can improve the efficiency of heat generation for effective cancer therapy while administering a low NP treatment dose. This study investigated magnetic field strength and frequency, NP size, NP concentration, and solution viscosity as important parameters that impact the heating efficiency of iron oxide NPs with magnetite (Fe3O4) and maghemite (?-Fe2O3) crystal structures. Heating efficiencies were determined for each experimental setting, with specific absorption rates (SARs) ranging from 3.7 to 325.9 W/g Fe. Magnetic heating was conducted on iron oxide NPs synthesized in our laboratories (with average core sizes of 8, 11, 13, and 18 nm), as well as commercially-available iron oxides (with average core sizes of 8, 9, and 16 nm). The experimental magnetic coil system made it possible to isolate the effect of magnetic field parameters and independently study the effect on heat generation. The highest SAR values were found for the 18 nm synthesized particles and the maghemite nanopowder. Magnetic field strengths were applied in the range of 15.1-47.7 kA/m, with field frequencies ranging from 123 to 430 kHz. The best heating was observed for the highest field strengths and frequencies tested, with results following trends predicted by the Rosensweig equation. An increase in solution viscosity led to lower heating rates in nanoparticle solutions, which can have significant implications for the application of magnetic fluid hyperthermia in vivo.

  20. The generation and amplification of intergalactic magnetic fields in analogue laboratory experiments with high power lasers

    Science.gov (United States)

    Gregori, G.; Reville, B.; Miniati, F.

    2015-11-01

    The advent of high-power laser facilities has, in the past two decades, opened a new field of research where astrophysical environments can be scaled down to laboratory dimensions, while preserving the essential physics. This is due to the invariance of the equations of magneto-hydrodynamics to a class of similarity transformations. Here we review the relevant scaling relations and their application in laboratory astrophysics experiments with a focus on the generation and amplification of magnetic fields in cosmic environment. The standard model for the origin of magnetic fields is a multi stage process whereby a vanishing magnetic seed is first generated by a rotational electric field and is then amplified by turbulent dynamo action to the characteristic values observed in astronomical bodies. We thus discuss the relevant seed generation mechanisms in cosmic environment including resistive mechanism, collision-less and fluid instabilities, as well as novel laboratory experiments using high power laser systems aimed at investigating the amplification of magnetic energy by magneto-hydrodynamic (MHD) turbulence. Future directions, including efforts to model in the laboratory the process of diffusive shock acceleration are also discussed, with an emphasis on the potential of laboratory experiments to further our understanding of plasma physics on cosmic scales.

  1. The generation of magnetic fields by the Biermann battery and the interplay with the Weibel instability

    CERN Document Server

    Schoeffler, K M; Fonseca, R A; Silva, L O

    2015-01-01

    An investigation of magnetic fields generated in an expanding bubble of plasma with misaligned temperature and density gradients (driving the Biermann battery mechanism) is performed. With gradient scales $L$, large-scale magnetic fields are generated by the Biermann battery mechanism with plasma $\\beta \\sim 1$, as long as $L$ is comparable to the ion inertial length $d_i$. For larger system sizes, $L/d_e > 100$ (where $d_e$ is the electron inertial length), the Weibel instability generates magnetic fields of similar magnitude but with wavenumber $k d_e \\sim 0.2$. In both cases, the growth and saturation of these fields have a weak dependence on mass ratio $m_i/m_e$, indicating electron mediated physics. A scan in system size is performed at $m_i/m_e = 2000$, showing agreement with previous results with $m_i/m_e = 25$. In addition, the instability found at large system sizes is quantitatively demonstrated to be the Weibel instability. Furthermore, magnetic and electric energy spectra at scales below the elect...

  2. Analytical analysis of magnetic field and back electromotive force calculation of an axial-flux permanent magnet synchronous generator with coreless stator

    OpenAIRE

    Virti?, Peter; Pišek, Peter; Mar?i?, Tine; Hadžiselimovi?, Miralem; Štumberger, Bojan

    2012-01-01

    This paper presents the analytical analysis of magnetic field and back electromotive force (back EMF) calculation in an axial flux permanent magnet synchronous generator (AFPMSG) without stator core. For the verification, the numerical analysis [finite element method (FEM)] of magnetic field is accomplished and comparison between analytical and numerical solution of magnetic field is presented. Both analytical and numerical solutions are obtained via magnetic vector potential, respectively. T...

  3. Magnetic Field

    DEFF Research Database (Denmark)

    Olsen, Nils

    2015-01-01

    he Earth has a large and complicated magnetic field, the major part of which is produced by a self-sustaining dynamo operating in the fluid outer core. Magnetic field observations provide one of the few tools for remote sensing the Earth’s deep interior, especially regarding the dynamics of the fluid flow at the top of the core. However, what is measured at or near the surface of the Earth is the superposition of the core field and fields caused by magnetized rocks in the Earth’s crust, by electric currents flowing in the ionosphere, magnetosphere, and oceans, and by currents induced in the Earth by time-varying external fields. These sources have their specific characteristics in terms of spatial and temporal variations, and their proper separation, based on magnetic measurements, is a major challenge. Such a separation is a prerequisite for remote sensing by means of magnetic field observations.

  4. Use of the Magnetic Field Generated by the Internal Distribution of Injected Currents for Electrical Impedance Tomography (MR-EIT)

    OpenAIRE

    Birgül, Y. Ziya ?der and Özlem

    1998-01-01

    In two dimensional conventional Electrical Impedance Tomography (EIT), volume conductor is probed by means of injected currents, and peripheral voltage measurements are used as input to the reconstruction algorithm. The current that flows in the 2D object creates magnetic fields that are perpendicular to the plane of imaging. Such magnetic fields can be measured using magnetic resonance tomography. In this study, use of this magnetic field generated by the injected currents, for the purpose o...

  5. A prevalence of dynamo-generated magnetic fields in the cores of intermediate-mass stars

    CERN Document Server

    Stello, D; Fuller, J; Huber, D; Garcia, R A; Bedding, T R; Bildsten, L; Aguirre, V Silva

    2016-01-01

    Magnetic fields play a role in almost all stages of stellar evolution. Most low-mass stars, including the Sun, show surface fields that are generated by dynamo processes in their convective envelopes. Intermediate-mass stars do not have deep convective envelopes, although 10% exhibit strong surface fields that are presumed to be residuals from the stellar formation process. These stars do have convective cores that might produce internal magnetic fields, and these might even survive into later stages of stellar evolution, but information has been limited by our inability to measure the fields below the stellar surface. Here we use asteroseismology to study the occurrence of strong magnetic fields in the cores of low- and intermediate-mass stars. We have measured the strength of dipolar oscillation modes, which can be suppressed by a strong magnetic field in the core, in over 3600 red giant stars observed by Kepler. About 20% of our sample show mode suppression but this fraction is a strong function of mass. S...

  6. Cosmological Magnetic Fields

    CERN Document Server

    Kunze, Kerstin E

    2013-01-01

    Magnetic fields are observed on nearly all scales in the universe, from stars and galaxies upto galaxy clusters and even beyond. The origin of cosmic magnetic fields is still an open question, however a large class of models puts its origin in the very early universe. A magnetic dynamo amplifying an initial seed magnetic field could explain the present day strength of the galactic magnetic field. However, it is still an open problem how and when this initial magnetic field was created. Observations of the cosmic microwave background (CMB) provide a window to the early universe and might therefore be able to tell us whether cosmic magnetic fields are of primordial, cosmological origin and at the same time constrain its parameters. We will give an overview of the observational evidence of large scale magnetic fields, describe generation mechanisms of primordial magnetic fields and possible imprints in the CMB.

  7. The interrelation between the generation of large-scale electric fields and that of large-scale magnetic fields during inflation

    OpenAIRE

    Bamba, Kazuharu

    2007-01-01

    The interrelation between the generation of large-scale electric fields and that of large-scale magnetic fields due to the breaking of the conformal invariance of the electromagnetic field in inflationary cosmology is studied. It is shown that if large-scale magnetic fields with a sufficiently large amplitude are generated during inflation, the generation of large-scale electric fields is suppressed, and vice versa. Furthermore, a physical interpretation of the result and it...

  8. Magnetic Field

    DEFF Research Database (Denmark)

    Olsen, Nils

    2015-01-01

    he Earth has a large and complicated magnetic field, the major part of which is produced by a self-sustaining dynamo operating in the fluid outer core. Magnetic field observations provide one of the few tools for remote sensing the Earth’s deep interior, especially regarding the dynamics of the fluid flow at the top of the core. However, what is measured at or near the surface of the Earth is the superposition of the core field and fields caused by magnetized rocks in the Earth’s crust, by elect...

  9. External Magnetic Field Reduction Techniques for the Advanced Stirling Radioisotope Generator

    Science.gov (United States)

    Niedra, Janis M.; Geng, Steven M.

    2013-01-01

    Linear alternators coupled to high efficiency Stirling engines are strong candidates for thermal-to-electric power conversion in space. However, the magnetic field emissions, both AC and DC, of these permanent magnet excited alternators can interfere with sensitive instrumentation onboard a spacecraft. Effective methods to mitigate the AC and DC electromagnetic interference (EMI) from solenoidal type linear alternators (like that used in the Advanced Stirling Convertor) have been developed for potential use in the Advanced Stirling Radioisotope Generator. The methods developed avoid the complexity and extra mass inherent in data extraction from multiple sensors or the use of shielding. This paper discusses these methods, and also provides experimental data obtained during breadboard testing of both AC and DC external magnetic field devices.

  10. Fluid theory for quasistatic magnetic field generation in intense laser plasma interaction

    International Nuclear Information System (INIS)

    Based on the ten-moment Grad system of hydrodynamic equations, a self-consistent fluid model is presented for the generation of quasistatic magnetic fields in relativistic intense laser plasma interaction. In this model, the nondiagonal stress tensor is taken into account and the generalized vorticity is proved to be not conserved, which are different from previous ideal fluid models. In the quasistatic approximation, where the low-frequency phase speed vp is much smaller than the electron thermal speed vte, the axial magnetic field Bz and the azimuthal one B? are derived. It is found that the condition vp>>vte used as the cold fluid approximation by previous papers is improper, where the derived Bz is incomplete and one magnetization current for Bz associated with the electron thermal motion does not appear. The profiles of both Bz and B? are analyzed. Their dependence on the laser intensity is discussed

  11. Magnetic field generation and electrostatic shock wave formation driven by counter-streaming pair plasmas

    International Nuclear Information System (INIS)

    By using two-Dimensional (2-D) and 3-D fully electromagnetic and relativistic Particle-In-Cell (PIC) codes, we investigated a collision process of the counter-streaming electron-positron pair plasmas. The collisionless counter-streaming plasmas become unstable against the counter-streaming instability similar to Weibel instability. This instability plays important role in conversion process from particle flow energy to magnetic field energy. We found two kinds of instability in counter-streaming plasmas. The magnetic fields are generated by the electromagnetic counter-streaming instability and the electric fields are formed by the electrostatic two-stream instability. High-energy particles are also produced due to the generated electric fields. In astrophysical plasmas, Gamma-Ray Burst (GRB) can release huge energy over a few seconds in a small volume. It is widely believed that GRB afterglows are observed by synchrotron emission. However, this emission mechanism must require strong magnetic fields in the background. Our simulation results are useful for understanding synchrotron GRB model

  12. Electromotive Force Generation with Hydrogen Release by Salt Water Flow under a Transverse Magnetic Field

    OpenAIRE

    Roberto De Luca

    2011-01-01

    By considering an electrolyte solution in motion in a duct under a transverse magnetic field, we notice that a so called Faraday voltage arises because of the Lorentz force acting on anions and cations in the fluid. When salt water is considered, hydrogen production takes place at one of the electrodes if an electric current, generated by Faraday voltage, flows in an external circuit. The maximum amount of hydrogen production rate is calculated by basic electrochemical concepts.

  13. Generating vorticity and magnetic fields in plasmas in general relativity: spacetime curvature drive

    CERN Document Server

    Asenjo, Felipe A; Qadir, Asghar

    2012-01-01

    Using the generally covariant magnetofluid formalism for a hot plasma, a new spacetime curvature driven mechanism for generating seed vorticity/magnetic field is presented. The ``battery'' owes its origin to the interaction between gravity and the inhomogeneous plasma thermodynamics. The general relativistic drive is evaluated for two simple cases: seed formation in a simplified model of a hot plasma accreting in stable orbits around a Schwarzschild black hole, and for particles in free fall near the horizon. Some astrophysical applications are suggested.

  14. The First Magnetic Fields

    CERN Document Server

    Widrow, Lawrence M; Schleicher, Dominik; Subramanian, Kandaswamy; Tsagas, Christos G; Treumann, Rudolf A

    2011-01-01

    We review current ideas on the origin of galactic and extragalactic magnetic fields. We begin by summarizing observations of magnetic fields at cosmological redshifts and on cosmological scales. These observations translate into constraints on the strength and scale magnetic fields must have during the early stages of galaxy formation in order to seed the galactic dynamo. We examine mechanisms for the generation of magnetic fields that operate prior during inflation and during subsequent phase transitions such as electroweak symmetry breaking and the quark-hadron phase transition. The implications of strong primordial magnetic fields for the reionization epoch as well as the first generation of stars is discussed in detail. The exotic, early-Universe mechanisms are contrasted with astrophysical processes that generate fields after recombination. For example, a Biermann-type battery can operate in a proto-galaxy during the early stages of structure formation. Moreover, magnetic fields in either an early genera...

  15. Nonlinear generation of large-scale magnetic fields in forced spherical shell dynamos

    International Nuclear Information System (INIS)

    In an earlier paper [P. W. Livermore, D. W. Hughes, and S. M. Tobias, ''The role of helicity and stretching in forced kinematic dynamos in a spherical shell'', Phys. Fluids 19, 057101 (2007)], we considered the kinematic dynamo action resulting from a forced helical flow in a spherical shell. Although mean field electrodynamics suggests that the resulting magnetic field should have a significant mean (axisymmetric) component, we found no evidence for this; the dynamo action was distinctly small scale. Here we extend our investigation into the nonlinear regime in which the magnetic field reacts back on the velocity via the Lorentz force. Our main result is somewhat surprising, namely, that nonlinear effects lead to a considerable change in the structure of the magnetic field, its final state having a significant mean component. By investigating the dominant flow-field interactions, we isolate the dynamo mechanism and show schematically how the generation process differs between the kinematic and nonlinear regimes. In addition, we are able to calculate some components of the transport coefficient ? and thus discuss our results within the context of mean field electrodynamics.

  16. Primordial magnetic field constrained from CMB anisotropies,and its generation and evolution before, during and after the BBN

    OpenAIRE

    Dai G. Yamazaki; Ichiki, Kiyotomo; Kajino, Toshitaka; Grant J. Mathews

    2006-01-01

    The primordial magnetic field (PMF) can strongly affect the cosmic microwave background (CMB) power spectrum and the formation of large scale structure. In this presentation, we calculate the CMB temperature anisotropies generated by including a power-law magnetic field at the photon last scattering surface (PLSS). We then deduce an upper limit on the primordial magnetic field based upon our theoretical analysis of the power excess on small angular scales. We have taken into...

  17. Effect of a wiggler magnetic field and the ponderomotive force on the second harmonic generation in laser-plasma interactions

    OpenAIRE

    NOROOZI, Hassan Ranjbar ASKARI and Maryam

    2009-01-01

    In this paper, we consider second harmonic generation and its phase-matching in an underdense plasma in the presence of a wiggler magnetic field. Wiggler magnetic field plays both a dynamic role in producing the traverse harmonic current and a kinematical role in ensuring phase-matching. The inertial ponderomotive force r (\\vec{u} . \\vec \

  18. Significance of self magnetic field in long-distance collimation of laser-generated electron beams

    CERN Document Server

    Chen, Shi; Niu, Yifei; Dan, Jiakun; Chen, Ziyu; Li, Jianfeng

    2014-01-01

    Long-distance collimation of fast electron beams generated by laser-metallic-wire targets has been observed in recent experiments, while the mechanism behind this phenomenon remains unclear. In this work, we investigate in detail the laser-wire interaction processes with a simplified model and Classical Trajectory Monte Carlo simulations, and demonstrate the significance of the self magnetic fields of the beams in the long-distance collimation. Good agreements of simulated image plate patterns with various experiments and detailed analysis of electron trajectories show that the self magnetic fields provide restoring force that is critical for the beam collimation. By studying the wire-length dependence of beam divergence in certain experiments, we clarify that the role of the metallic wire is to balance the space-charge effect and thus maintain the collimation.

  19. Scott Correction for Large Atoms and Molecules in a Self-Generated Magnetic Field

    DEFF Research Database (Denmark)

    Erdös, Laszlo; Fournais, SØren

    2012-01-01

    We consider a large neutral molecule with total nuclear charge Z in non-relativistic quantum mechanics with a self-generated classical electromagnetic field. To ensure stability, we assume that Za2 = ¿0 for a sufficiently small ¿0, where a denotes the fine structure constant. We show that, in the simultaneous limit Z ¿ 8, a ¿ 0 such that ¿ = Za2 is fixed, the ground state energy of the system is given by a two term expansion c1Z7/3 + c2(¿) Z2 + o(Z2). The leading term is given by the non-magnetic Thomas-Fermi theory. Our result shows that the magnetic field affects only the second (so-called Scott) term in the expansion.

  20. Particle Acceleration, Magnetic Field Generation, and Associated Emission in Collisionless Relativistic Jets

    CERN Document Server

    Nishikawa, K -I; Fishiman, G J; Hardee, P

    2008-01-01

    Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), and Galactic microquasar systems usually have power-law emission spectra. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that acceleration occurs within the downstream jet. Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, other two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the jet head. The ``jitter'' radiation from deflected electrons has different properties than synchrotron ra...

  1. Asymptotics of the ground state energy for atoms and molecules in the self-generated magnetic field

    OpenAIRE

    Ivrii, Victor

    2011-01-01

    Asymptotics of the ground state energy of the heavy atoms and molecules in the self-generated magnetic field has been derived and for minimal energy positions of nuclei remainder estimate $O(N^{16/9})$ has been recovered.

  2. Magnetic fields in galaxies

    CERN Document Server

    Beck, Rainer

    2013-01-01

    Most of the visible matter in the Universe is ionized, so that cosmic magnetic fields are quite easy to generate and due to the lack of magnetic monopoles hard to destroy. Magnetic fields have been measured in or around practically all celestial objects, either by in-situ measurements of spacecrafts or by the electromagnetic radiation of embedded cosmic rays, gas or dust. The Earth, the Sun, solar planets, stars, pulsars, the Milky Way, nearby galaxies, more distant (radio) galaxies, quasars and even intergalactic space in clusters of galaxies have significant magnetic fields, and even larger volumes of the Universe may be permeated by "dark" magnetic fields. Information on cosmic magnetic fields has increased enormously as the result of the rapid development of observational methods, especially in radio astronomy. In the Milky Way, a wealth of magnetic phenomena was discovered, which are only partly related to objects visible in other spectral ranges. The large-scale structure of the Milky Way's magnetic fie...

  3. Microwave generation from a cusptron device with a rotating electron beam through a magnetic cusp field

    International Nuclear Information System (INIS)

    At the University of Maryland, high-power microwave generation experiments have been conducted with a relativistic rotating electron beam of 2 MeV, 12 kA, and 10 ns. Radiation is produced via the negative mass instability at various harmonics of the electron cyclotron frequency determined by the interaction of the rotating beam cyclotron modes and the modes of the conducting boundary system. Using a magnetron-type conducting boundary in the beam-wave interaction region, we are able to exercise effective mode control. This kind of device holds promise as a tunable, high-frequency microwave tube with low magnetic fields. A table-top experiment with a non-relativistic electron beam (-6 (I/V /sup 3/2/ ). Passing through a magnetic cusp field, the beam becomes a welldefined rotating hollow beam with 3 cm diameter and 0.2 cm thickness. The name ''cusptron'' is originated from the cusp and the magnetron. The beam dimensions are independent of the beam energy and also of the magnetic field strength

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

    OpenAIRE

    Ivrii, Victor

    2013-01-01

    We consider asymptotics of the ground state energy of heavy atoms and molecules in the self-generatedl magnetic field. Namely, we consider $$ H=((D-A)\\cdot\\boldsymbol{\\sigma})^2-V $$ with $$V=\\sum_{1\\le m\\le M} \\frac{Z_m}{|x-y_m|}$$ and a corresponding Multiparticle Quantum Hamiltonian $$ \\mathsf{H}=\\sum_{1\\le n\\le N} H_{x_n} +\\sum_{1\\le n < n'\\le N}|x_n-x_{n'}|^{-1} $$ on the Fock space $\\wedge _{1\\le n\\le N} L^2(\\mathbb{R}^3, \\mathbb{C}^2)$. Here $A$ is a self-generated ma...

  5. Generating vorticity and magnetic fields in plasmas in general relativity: Spacetime curvature drive

    Energy Technology Data Exchange (ETDEWEB)

    Asenjo, Felipe A.; Mahajan, Swadesh M. [Institute for Fusion Studies, University of Texas at Austin, Texas 78712 (United States); Qadir, Asghar [Centre for Advanced Mathematics and Physics, National University of Sciences and Technology, H12, Islamabad 4400 (Pakistan)

    2013-02-15

    Using the generally covariant magnetofluid formalism for a hot plasma, a spacetime curvature driven mechanism for generating seed vorticity/magnetic field is presented. The 'battery' owes its origin to the interaction between the gravity modified Lorentz factor of the fluid element and the inhomogeneous plasma thermodynamics. The general relativistic drive is evaluated for two simple cases: seed formation in a simplified model of a hot plasma accreting in stable orbits around a Schwarzschild black hole and for particles in free fall near the horizon. Some astrophysical applications are suggested.

  6. Convection and magnetic field generation in the interior of planets (August Love Medal Lecture)

    Science.gov (United States)

    Christensen, U. R.

    2009-04-01

    Thermal convection driven by internal energy plays a role of paramount importance in planetary bodies. Its numerical modeling has been an essential tool for understanding how the internal engine of a planet works. Solid state convection in the silicate or icy mantles is the cause of endogenic tectonic activity, volcanism and, in the case of Earth, of plate motion. It also regulates the energy budget of the entire planet, including that of its core, and controls the presence or absence of a dynamo. The complex rheology of solid minerals, effects of phase transitions, and chemical heterogeneity are important issues in mantle convection. Examples discussed here are the convection pattern in Mars and the complex morphology of subducted slabs that are observed by seismic tomography in the Earth's mantle. Internally driven convection in the deep gas envelopes of the giant planets is possibly the cause for the strong jet streams at the surfaces that give rise to their banded appearance. Modeling of the magnetohydrodynamic flow in the conducting liquid core of the Earth has been remarkably successful in reproducing the primary properties of the geomagnetic field. As an examplefor attempts to explain also secondary properties, I will discuss dynamo models that account for the thermal coupling to the mantle. The understanding of the somewhat enigmatic magnetic fields of some other planets is less advanced. Here I will show that dynamos that operate below a stable conducting layer in the upper part of the planetary core can explain the unusual magnetic field properties of Mercury and Saturn. The question what determines the strength of a dynamo-generated magnetic field has been a matter of debate. From a large set of numerical dynamo simulations that cover a fair range of control parameters, we find a rule that relates magnetic field strength to the part of the energy flux that is thermodynamically available to be transformed into other forms of energy. This rules predicts correctly not only the magnetic field strength of planets with sufficiently simple dynamos (Earth and Jupiter), but also that of rapidly rotating stars.

  7. Microwave generation in interaction of intense electron beam with plasma in mirror magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Kolyada, Y.E.; Kornilov, E.A.; Fainberg, Y.B.; Ognivenko, V.V.; Kiyashko, V.A.; Pedenko, N.S.

    1976-09-01

    The generation of intense microwaves in an interaction of a high-current electron beam with a plasma in a mirror magnetic field is studied experimentally. The plasma is in an open cavity consisting of two mirrors. A microwave power of 60 MW is achieved at a wavelength of 2.5 cm when the electron beam has an energy of 150 keV, a current of 12 kA, and a pulse length of 0.7..mu..sec. The microwave intensity increases with increasing transverse velocity of the beam electrons. The incorporation of feedback in the system consisting of the electron beam, the plasma, and the open cavity results in a contraction of the spectrum and an increase in the generation efficiency.

  8. Plasma circuit breaker in a magnetic field as a high-power ion flux generator

    International Nuclear Information System (INIS)

    It is ascertained that plasma circuit breaker (PCB) in the external magnetic field of acute-anguled geometry in the mode when PCB serves as inductive storage loading is a natural magnetoizolated diode. Using PCB as an ion emitter and as a high-voltage generator it proved possible in case of full electron magnetiuzation to attain the maximum efficiency of the storage. The density of ion current evaluated by the measured energy density for 30 J/cm2 thermocouple and by the energy of 1.5 MeV constitutes 100 A/cm2. The given method of ion generation is very effective when high ion currents with a high energy are required

  9. Global trace asymptotics in the self-generated magnetic field in the case of Coulomb-like singularities

    CERN Document Server

    Ivrii, Victor

    2011-01-01

    We consider a semiclassical asymptotics of local trace for the 3D-Schroedinger operator with self-generated magnetic field in the case when electric potential has one or several Coulomb-like singularities; it is given by Weyl expression plus (magnetic) Scott correction term with O(h^{-4/3}) error provided distance between singularities is large enough.

  10. Shock Structure and Magnetic Fields Generation Associated with Relativistic Jets Unmagnetized Pair Plasma

    Science.gov (United States)

    Niemiec, J.; Nishikawa, K.-I.; Hardee, P.; Pohl, M.; Medvedev, M.; Mizuno, Y.; Zhang, B.; Oka, M.; Sol, H.; Hartmann, D.

    2009-01-01

    Using 3D and 2D particle-in-cell simulations we investigate a shock structure, magnetic field generation, and particle acceleration associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized pair plasma. The simulations use long computational grids which allow to study the formation and dynamics of the system in a spatial and temporal way. We find for the first time a relativistic shock system comparable to a predicted magnetohydrodynamic shock structure consisting of leading and trailing shocks separated by a contact discontinuity. Strong electromagnetic fields resulting from the Weibel two-stream instability are generated in the trailing shock where jet matter is thermalized and decelerated. We analyze the formation and nonlinear development through saturation and dissipation of those fields and associated particle acceleration. In the AGN context the trailing shock corresponds to the jet shock at the head of a relativistic astrophysical jet. In the GRB context this trailing shock can be identified with the bow shock driven by relativistic ejecta. The strong electromagnetic field region in the trailing shock provides the emission site for the hot spot at the leading edge of AGN jets and for afterglow emission from GRBs.

  11. Generation of flat-top pulsed magnetic fields with feedback control approach

    OpenAIRE

    Kohama, Yoshimitsu; Kindo, Koichi

    2015-01-01

    We describe the construction of a simple, compact, and cost-effective feedback system that produces flat-top field profiles in pulsed magnetic fields. This system is designed for use in conjunction with a typical capacitor-bank driven pulsed magnet, and was tested using a 60-T pulsed magnet. With the developed feedback controller, we have demonstrated flat-top magnetic fields as high as 60.64 T with an excellent field stability of +-0.005 T. The result indicates that the fla...

  12. Biological effects from a static magnetic field generated by a 0.5 T Magnetic Resonance system on the enzyme activity of catalase and creatin kinase in rodents

    International Nuclear Information System (INIS)

    The authors investigated possible alterations in the enzyme activity of catalase and isozyme MB-creatin kinase induced by prolonged exposure of laboratory rodents to a static magnetic field generated by a 0.5 T Magnetic Resonance unit. The results seems to exclude any alterations in the activity of catalase and MB-CK after exposure. However some homeostatic mechanism peculiar to multi cellular organisms might act 'in vivo' to adapt to the effects of the static magnetic field during exposure

  13. Generation of flat-top pulsed magnetic fields with feedback control approach

    CERN Document Server

    Kohama, Yoshimitsu

    2015-01-01

    We describe the construction of a simple, compact, and cost-effective feedback system that produces flat-top field profiles in pulsed magnetic fields. This system is designed for use in conjunction with a typical capacitor-bank driven pulsed magnet, and was tested using a 60-T pulsed magnet. With the developed feedback controller, we have demonstrated flat-top magnetic fields as high as 60.64 T with an excellent field stability of +-0.005 T. The result indicates that the flat-top pulsed magnetic field produced features high field stability and an accessible field strength. These features make this system useful for improving the resolution of data with signal averaging.

  14. Effect of the plasma-generated magnetic field on relativistic electron transport.

    Science.gov (United States)

    Nicolaï, Ph; Feugeas, J-L; Regan, C; Olazabal-Loumé, M; Breil, J; Dubroca, B; Morreeuw, J-P; Tikhonchuk, V

    2011-07-01

    In the fast-ignition scheme, relativistic electrons transport energy from the laser deposition zone to the dense part of the target where the fusion reactions can be ignited. The magnetic fields and electron collisions play an important role in the collimation or defocusing of this electron beam. Detailed description of these effects requires large-scale kinetic calculations and is limited to short time intervals. In this paper, a reduced kinetic model of fast electron transport coupled to the radiation hydrodynamic code is presented. It opens the possibility to carry on hybrid simulations in a time scale of tens of picoseconds or more. It is shown with this code that plasma-generated magnetic fields induced by noncollinear temperature and density gradients may strongly modify electron transport in a time scale of a few picoseconds. These fields tend to defocus the electron beam, reducing the coupling efficiency to the target. This effect, that was not seen before in shorter time simulations, has to be accounted for in any ignition design using electrons as a driver. PMID:21867317

  15. Magnetic field distribution in the plasma flow generated by a plasma focus discharge

    Energy Technology Data Exchange (ETDEWEB)

    Mitrofanov, K. N., E-mail: mitrofan@triniti.ru [Troitsk Institute for Innovaiton and Fusion Research (Russian Federation); Krauz, V. I., E-mail: krauz_vi@nrcki.ru; Myalton, V. V.; Velikhov, E. P.; Vinogradov, V. P.; Vinogradova, Yu. V. [National Research Centre Kurchatov Institute (Russian Federation)

    2014-11-15

    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.

  16. Dynamics of radiation losses in Z-pinch plasma with taking into account generation of turbulent magnetic fields

    International Nuclear Information System (INIS)

    We estimated the total radiation losses from argon Z-pinches. Radiation losses due to excitation, di-electronic recombination, Bremsstrahlung, radiative recombination and also ionization, were considered. Each separate ion is analyzed in detail and the influence of density is taken into account. Our pinch dynamics includes Joule heating, anomalous plasma resistance, plasma outflow in Z-direction, electron beam generation, magnetic field pressure, radiation losses. Main novelty of the given model is generation of chaotic/turbulent magnetic fields. It is shown, that turbulent magnetic fields affect the dynamics of plasma parameters. The influence of turbulent magnetic field is analyzed on the dynamics of plasma temperature, density, radiation losses, line emission. (author)

  17. Self-generated magnetic field measurements in TEA-CO2 laser produced plasmas on different targets

    International Nuclear Information System (INIS)

    Results of self-generated magnetic field measurements using differential inductive probes in TEA-CO2 laser produced plasmas on different metallic targets are presented. Dependences of the magnetic field strengths on the incident laser energy, the target material, the target-focus distance and the coordinates of probe position are investigated. The results are correlated to those of some other complementary X-ray emission and ion collection measurements perfopmed in the same reproducible experimental conditions. (authors)

  18. Generation of excited coherent states for a charged particle in a uniform magnetic field

    International Nuclear Information System (INIS)

    We introduce excited coherent states, |?,?;nгЂ‰?a†n|?,?гЂ‰, where n is an integer and states |?,?гЂ‰ denote the coherent states of a charged particle in a uniform magnetic field. States |?,?гЂ‰ minimize the Schrödinger-Robertson uncertainty relation while having the nonclassical properties. It has been shown that the resolution of identity condition is realized with respect to an appropriate measure on the complex plane. Some of the nonclassical features such as sub-Poissonian statistics and quadrature squeezing of these states are investigated. Our results are compared with similar Agarwal’s type photon added coherent states (PACSs) and it is shown that, while photon-counting statistics of |?,?,nгЂ‰ are the same as PACSs, their squeezing properties are different. It is also shown that for large values of |?|, while they are squeezed, they minimize the uncertainty condition. Additionally, it has been demonstrated that by changing the magnitude of the external magnetic field, Bext, the squeezing effect is transferred from one component to another. Finally, a new scheme is proposed to generate states |?,?;nгЂ‰ in cavities.?

  19. Magnetic field enhancement of generation-recombination and shot noise in organic light emitting diodes

    Energy Technology Data Exchange (ETDEWEB)

    Djidjou, T. K.; Basel, Tek; Rogachev, A. [Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112 (United States); Chen, Ying; Shinar, J. [Ames Laboratory-USDOE, and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 (United States)

    2015-03-21

    We have studied the effect of magnetic field on noise in series of 2-methoxy-5-(2?-ethylhexyloxy)-1,4-phenylenevinylene-based organic light emitting diodes with dominant hole injection, dominant electron injection, and balanced electron and hole injection. The noise spectra of the balanced devices revealed the generation-recombination (g-r) noise term, which we associated with bimolecular electron-hole recombination. The presence of the g-r noise term is correlated with the strong organic magnetoresistance (up to 25%) observed in the balanced devices. The noise spectra also have the shot noise contribution with the Fano factor 0.25–0.4. We found that time constant of the g-r term decreases and the magnitude of shot noise increases when magnetic field is applied. This behavior can be consistently explained within the polaron-polaron model of organic magnetoresistance. We have not found any evidence that the magnetoresistance in studied devices is affected by traps.

  20. Isotropic round-wire multifilament cuprate superconductor for generation of magnetic fields above 30 T

    Science.gov (United States)

    Larbalestier, D. C.; Jiang, J.; Trociewitz, U. P.; Kametani, F.; Scheuerlein, C.; Dalban-Canassy, M.; Matras, M.; Chen, P.; Craig, N. C.; Lee, P. J.; Hellstrom, E. E.

    2014-04-01

    Magnets are the principal market for superconductors, but making attractive conductors out of the high-temperature cuprate superconductors (HTSs) has proved difficult because of the presence of high-angle grain boundaries that are generally believed to lower the critical current density, Jc. To minimize such grain boundary obstacles, HTS conductors such as REBa2Cu3O7-x and (Bi, Pb)2Sr2Ca2Cu3O10-x are both made as tapes with a high aspect ratio and a large superconducting anisotropy. Here we report that Bi2Sr2CaCu2O8-x (Bi-2212) can be made in the much more desirable isotropic, round-wire, multifilament form that can be wound or cabled into arbitrary geometries and will be especially valuable for high-field NMR magnets beyond the present 1 GHz proton resonance limit of Nb3Sn technology. An appealing attribute of this Bi-2212 conductor is that, being without macroscopic texture, it contains many high-angle grain boundaries but nevertheless attains a very high Jc of 2,500 A mm-2 at 20 T and 4.2 K. The large potential of the conductor has been demonstrated by building a small coil that generated almost 2.6 T in a 31 T background field. This demonstration that grain boundary limits to high Jc can be practically overcome underlines the value of a renewed focus on grain boundary properties in non-ideal geometries.

  1. Hydrodynamic structures generated by a rotating magnetic field in a cylindrical vessel

    International Nuclear Information System (INIS)

    The hydrodynamic structures arising in a cylinder under the influence of a rotating magnetic field were considered, and the stability of a primary stationary flow in an infinitely long cylinder was investigated by linear approximation. The curves of neutral stability were obtained for a wide range of flow parameters and the calculations generated a single-vortex (in the radial direction) structure of Taylor’s vortices. The flow stability in the infinitely long cylinder was evaluated based on energy balance. The problem of three-dimensional stationary flow of a viscous incompressible conducting liquid induced by a rotating magnetic field in a cylindrical vessel of limited length was solved using an iteration method. The values of the parameters were found for which the iterative process still converges. Numerical experiment made it possible to investigate the arising spatial flow patterns and to track their evolution with changes in the flow parameters. Results of modelling showed the appearance of a three-dimensional structure of Taylor-type vortices in the middle portion of a sufficiently long vessel. The appearance of a double laminar boundary layer was demonstrated under certain conditions of azimuthal velocity distribution along the vessel height at the location of the end-wave vortex. (paper)

  2. Generation of excited coherent states for a charged particle in a uniform magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Mojaveri, B., E-mail: bmojaveri@azaruniv.ac.ir [Department of Physics, Azarbaijan Shahid Madani University, P.O. Box 51745-406, Tabriz (Iran, Islamic Republic of); Dehghani, A., E-mail: a-dehghani@tabrizu.ac.ir, E-mail: alireza.dehghani@gmail.com [Department of Physics, Payame Noor University, P.O. Box 19395-3697, Tehran (Iran, Islamic Republic of)

    2015-04-15

    We introduce excited coherent states, |?,?;nгЂ‰?a{sup †n}|?,?гЂ‰, where n is an integer and states |?,?гЂ‰ denote the coherent states of a charged particle in a uniform magnetic field. States |?,?гЂ‰ minimize the Schrödinger-Robertson uncertainty relation while having the nonclassical properties. It has been shown that the resolution of identity condition is realized with respect to an appropriate measure on the complex plane. Some of the nonclassical features such as sub-Poissonian statistics and quadrature squeezing of these states are investigated. Our results are compared with similar Agarwal’s type photon added coherent states (PACSs) and it is shown that, while photon-counting statistics of |?,?,nгЂ‰ are the same as PACSs, their squeezing properties are different. It is also shown that for large values of |?|, while they are squeezed, they minimize the uncertainty condition. Additionally, it has been demonstrated that by changing the magnitude of the external magnetic field, B{sub ext}, the squeezing effect is transferred from one component to another. Finally, a new scheme is proposed to generate states |?,?;nгЂ‰ in cavities.?.

  3. Magnetic field enhancement of generation-recombination and shot noise in organic light emitting diodes

    Science.gov (United States)

    Djidjou, T. K.; Chen, Ying; Basel, Tek; Shinar, J.; Rogachev, A.

    2015-03-01

    We have studied the effect of magnetic field on noise in series of 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene-based organic light emitting diodes with dominant hole injection, dominant electron injection, and balanced electron and hole injection. The noise spectra of the balanced devices revealed the generation-recombination (g-r) noise term, which we associated with bimolecular electron-hole recombination. The presence of the g-r noise term is correlated with the strong organic magnetoresistance (up to 25%) observed in the balanced devices. The noise spectra also have the shot noise contribution with the Fano factor 0.25-0.4. We found that time constant of the g-r term decreases and the magnitude of shot noise increases when magnetic field is applied. This behavior can be consistently explained within the polaron-polaron model of organic magnetoresistance. We have not found any evidence that the magnetoresistance in studied devices is affected by traps.

  4. An Impulse Induction MHD Generator Having a Magnetic Field with a Radial Component

    International Nuclear Information System (INIS)

    An impulse induction MHD generator with a cylindrical channel has been theoretically and experimentally investigated. Given certain assumptions, it is possible to write the general system of the partial differential equations, which describes the behaviour of the generator. The mean spatial values of the physical quantities are calculated under certain simplifying conditions and a system of the common differential equations is obtained. After separation the common differential equations of the third order for the velocity and the current are found. These equations are homogeneous with constant and identical coefficients. The solution of these equations is not too complicated and information about their time dependence is obtained. The expressions for the power generated and the generator efficiency are found in the usual way. The equation of the volt-ampere characteristic is also obtained and the characteristic of the generator is found not to be, in general, linear. The equations for the case of open-circuit current and short-circuit voltage are derived. These equations are the common differential equations of the second order and their solutions give the possibility of determining two of the parameters of the plasma clusters. The theoretical conclusions are verified experimentally. A plasma gun is the source of the plasma clusters. The pressure is varied over 1.4 x 10-2 to 2 x 10-1 Torr. The magnetic field is 2 x 10-2 T. The electrical conductivity and the mass of the clusters is calculated from the expressions for the open-circuit voltage and short-circuit current. The results of the theoretical and experimental calculations are in acceptable agreement. It is possible to say that the generator will operate and could, after refinement, be used for diagnostics of plasma clusters. (author)

  5. Magnetic fields generated by an induction heating (IH) cook top do not cause genotoxicity in vitro.

    Science.gov (United States)

    Miyakoshi, Junji; Horiuchi, Emi; Nakahara, Takehisa; Sakurai, Tomonori

    2007-10-01

    The use of induction heater (IH) cook tops in homes has become widespread, especially in Japan, but there are concerns about the safety of intermediate frequency (IF) electromagnetic fields associated with these cooking appliances. Since the cellular genotoxicity of IF magnetic fields has not been examined in cultured cells, we examined the effects of these fields at a magnetic flux density of 532 +/- 20 microT at 23 kHz, using an exposure unit with a built-in CO2 incubator. Exposure to the IF magnetic field at 532 microT for 2 h did not affect the growth of CHO-K1 cells and caused no mutagenic effects in bacterial mutation assays. Exposure to the IF magnetic field for 2 h induced neither single nor double DNA strand breaks in comet assays, and caused no significant change in the mutation frequency at the HPRT locus compared to sham exposure. The magnetic field used in this study is more than 80 times higher than the level recommended as safe in the International Commission on Non-ionizing Radiation Protection (ICNIRP) guidelines. From these results, we suggest that exposure to an IF magnetic field for 2 h does not cause cellular genotoxicity in bacteria and in Chinese hamster cells. However, the possibility of effects on other cellular functions remains, and further studies on the cellular effects of IF magnetic fields are required. PMID:17492656

  6. Ultrafast generation of pseudo-magnetic field for valley excitons in WSe2 monolayers

    KAUST Repository

    Kim, J.

    2014-12-04

    The valley pseudospin is a degree of freedom that emerges in atomically thin two-dimensional transition metal dichalcogenides (MX2). The capability to manipulate it, in analogy to the control of spin in spintronics, can open up exciting opportunities. Here, we demonstrate that an ultrafast and ultrahigh valley pseudo-magnetic field can be generated by using circularly polarized femtosecond pulses to selectively control the valley degree of freedom in monolayer MX2. Using ultrafast pump-probe spectroscopy, we observed a pure and valley-selective optical Stark effect in WSe2 monolayers from the nonresonant pump, resulting in an energy splitting of more than 10 milli-electron volts between the K and K? valley exciton transitions. Our study opens up the possibility to coherently manipulate the valley polarization for quantum information applications.

  7. Diffusion and stochastic island generation in the magnetic field line random walk

    International Nuclear Information System (INIS)

    The cross-field diffusion of field lines in stochastic magnetic fields described by the 2D+slab model is studied using a semi-analytic statistical approach, the decorrelation trajectory method. We show that field line trapping and the associated stochastic magnetic islands strongly influence the diffusion coefficients, leading to dependences on the parameters that are different from the quasilinear and Bohm regimes. A strong amplification of the diffusion is produced by a small slab field in the presence of trapping. The diffusion regimes are determined and the corresponding physical processes are identified.

  8. Effects of self-generated electric and magnetic fields in laser-generated fast electron propagation in solid materials: Electric inhibition and beam pinching

    OpenAIRE

    Bernardinello, A; Batani, D; Antonicci, A; Pisani, F; Koenig, M.; Gremillet, L; Amiranoff, F.; Baton, S.; Martinolli, E; Rousseaux, C.; Hall, TA; Norreys, P.; Djaoui, A

    2001-01-01

    We present some experimental results which demonstrate the presence of electric inhibition in the propagation of relativistic electrons generated by intense laser pulses, depending on target conductivity. The use of transparent targets and shadowgraphic techniques has made it possible to evidence electron jets moving at the speed of light, an indication of the presence of self-generated strong magnetic fields.

  9. Self-generated magnetic fields of an air-breakdown plasma produced by two sequential laser pulses

    International Nuclear Information System (INIS)

    The spatial and temporal distribution of the self-generated magnetic fields were measured in a laser spark produced by double pulses in air. When an atmospheric air breakdown is produced by two sequential laser pulses a resonance-like phenomenon occurs which can be used for the study of the dependence of the amplitude of self-generated magnetic field on the time separation. The results are compared with those obtained when plasma in air was ignited on metal and dielectric targets. (D.Gy.)

  10. Transmittal properties of a superconductor-ferromagnetic metamaterial subjected to magnetic fields generated by the permanent magnets

    Science.gov (United States)

    Liu, H.; Li, X. T.; Zhou, P. B.; Zhang, H.; Yang, C.; Ma, G. T.; Wang, R.; Chen, H.; Wang, Z.; Li, N.; Zhang, L.

    2015-09-01

    Superconductor-ferromagnetic (FN) metamaterial with effective magnetic shielding and transmittal properties that allow the cloaking and transferring of static magnetic fields has been introduced. Most metamaterials consist of different arrangements of superconducting and ferromagnetic materials whose performance and feasibility mainly depend on the involved materials, their geometrical distribution and the permeability of each. In this paper, combining the method of transformation optics with the design of metamaterials, we experimentally demonstrated a superconductor-FM metamaterial system, composed of two coaxial cylinders of different lengths, to investigate the influence of the length and the properties of superconducting material on the magnetic transferring properties of the magnetic field produced by the permanent magnets. By comparing the transmittal magnetic field of different cases, the optimal structure has been ultimately achieved in terms of calculating the transmitted magnetic field ratios. The insights attained by the present study are aimed to provide useful implications for the design of wireless energy transmission and increasing the efficiency of magnetic transmittal devices.

  11. Splitting of generated atomic levels in the external electromagnetic and static magnetic fields

    International Nuclear Information System (INIS)

    Splitting of the degenerated 3d- and 4p-levels of the Na atom states is studied in the external linearly-polarized strong electromagnetic and static magnetic fields. It is shown that only in the case when the electromagnetic field is parallel to the magnetic one, splitting is additionally summing from Stark and Zeeman parts. In other cases this phenomenon does not occur

  12. Hydrodynamic structures generated by a rotating magnetic field in a cylindrical vessel

    Science.gov (United States)

    Zibold, A. F.

    2015-02-01

    The hydrodynamic structures arising in a cylinder under the influence of a rotating magnetic field were considered, and the stability of a primary stationary flow in an infinitely long cylinder was investigated by linear approximation. The curves of neutral stability were obtained for a wide range of flow parameters and the calculations generated a single-vortex (in the radial direction) structure of Taylor’s vortices. The flow stability in the infinitely long cylinder was evaluated based on energy balance. The problem of three-dimensional stationary flow of a viscous incompressible conducting liquid induced by a rotating magnetic field in a cylindrical vessel of limited length was solved using an iteration method. The values of the parameters were found for which the iterative process still converges. Numerical experiment made it possible to investigate the arising spatial flow patterns and to track their evolution with changes in the flow parameters. Results of modelling showed the appearance of a three-dimensional structure of Taylor-type vortices in the middle portion of a sufficiently long vessel. The appearance of a double laminar boundary layer was demonstrated under certain conditions of azimuthal velocity distribution along the vessel height at the location of the end-wave vortex. This article was accepted for publication in Fluid Dynamics Research 2014 Vol 46, No 4; which was a special issue consisting of papers from the 5th International Symposium on Bifurcations in Fluid Dynamics. Due to an unfortunate error on the part of the journal, this article was not published with the other articles from this issue.

  13. Relativistic derivations of the electric and magnetic fields generated by an electric point charge moving with constant velocity

    OpenAIRE

    Rothenstein, Bernhard; Popescu, Stefan; Spix, George J.

    2006-01-01

    We propose a simple relativistic derivation of the electric and the magnetic fields generated by an electric point charge moving with constant velocity. Our approach is based on the radar detection of the point space coordinates where the fields are measured. The same equations were previously derived in a relatively complicated way2 based exclusively on general electromagnetic field equations and without making use of retarded potentials or relativistic equations

  14. Hamilton flow generated by field lines near a toroidal magnetic surface

    International Nuclear Information System (INIS)

    A method is described for obtaining the Hamiltonian of a vacuum magnetic field in a given 3D toroidal magnetic surface (superconducting shell). This method is used to derive the expression for the integrable surface Hamiltonian in the form of the expansion of a rotational transform of field lines on embedded near-boundary magnetic surfaces into a Taylor series in the distance from the boundary. This expansion contains the value of the rotational transform and its shear at the boundary surface. It is shown that these quantities are related to the components of the first and second quadratic forms of the boundary surface

  15. Three-magnetic fields

    OpenAIRE

    Koivisto, Tomi S.; Urban, Federico R.

    2011-01-01

    A completely new mechanism to generate the observed amount of large-scale cosmological magnetic fields is introduced in the context of three-form inflation. The amplification of the fields occurs via fourth order dynamics of the vector perturbations and avoids the backreaction problem that plagues most previously introduced mechanisms.

  16. Global trace asymptotics in the self-generated magnetic field in the case of Coulomb-like singularities

    OpenAIRE

    Ivrii, Victor

    2011-01-01

    We consider a semiclassical asymptotics of local trace for the 3D-Schroedinger operator with self-generated magnetic field in the case when electric potential has one or several Coulomb-like singularities; it is given by Weyl expression plus (magnetic) Scott correction term with O(h^{-4/3}) error provided distance between singularities is large enough. Significant improvement and simplification in comparison to v1.

  17. Analysis of the magnetic field distribution in an homopolar generator as a pulse power source of electromagnetic launchers

    Science.gov (United States)

    Azzerboni, B.; Cardelli, E.; Tellini, A.

    1988-01-01

    A circuit-method approach is presented for evaluating the distribution of the current density and the magnetic field following a sudden short circuit in a homopolar generator. The method is applied to analyze the transient armature reaction in a counterrotating homopolar generator placed in a high magnetic field. The machine is divided into a finite number of volume elements, the centers of which are linked to produce a three-dimensional mesh. The branches of the mesh are characterized, like circuit branches, by resistors, capacitors, inductors, magnetic couplings, and independent voltage generators. The symmetries of the machine are used to obtain a reduced two-dimensional plane net. The behavior of the net can be analyzed by conventional analytical or numerical methods.

  18. Primordial magnetic fields at preheating

    OpenAIRE

    Diaz-Gil, A.; Garcia-Bellido, J; Perez, M. Garcia; Gonzalez-Arroyo, A

    2007-01-01

    Using lattice techniques we investigate the generation of long range cosmological magnetic fields during a cold electroweak transition. We will show how magnetic fields arise, during bubble collisions, in the form of magnetic strings. We conjecture that these magnetic strings originate from the alignment of magnetic dipoles associated with EW sphaleron-like configurations. We also discuss the early thermalisation of photons and the turbulent behaviour of the scalar fields af...

  19. Effect of a transverse magnetic field on the generation of electron beams in the gas-filled diode

    Science.gov (United States)

    Baksht, E. H.; Burachenko, A. G.; Erofeev, M. V.; Kostyrya, I. D.; Lomaev, M. I.; Rybka, D. V.; Tarasenko, V. F.

    2008-06-01

    The effect of a transverse magnetic field (0.080 and 0.016 T) on generation of an electron beam in the gas-filled diode is experimentally investigated. It is shown that, at voltage U = 25 kV across the diode and a low helium pressure (45 Torr), the transverse magnetic field influences the beam current amplitude behind a foil and its distribution over the foil cross section. At elevated pressures and under the conditions of ultrashort avalanche electron beam formation in helium, nitrogen, and air, the transverse magnetic field (0.080 and 0.016 T) has a minor effect on the amplitude and duration of the beam behind the foil. It is established that, when the voltage of the pulse generator reaches several hundreds of kilovolts, some runaway electrons (including the electrons from the discharge plasma near the cathode) are incident on the side walls of the diode.

  20. Software for evaluating magnetic induction field generated by power lines: implementation of a new algorithm

    International Nuclear Information System (INIS)

    The Regional Environment Protection Agency of Friuli Venezia Giulia (A.R.P.A. F.V.G., Italy) has performed an analysis on existing software designed to calculate magnetic induction field generated by power lines. As far as the agency requirements are concerned the tested programs display some difficulties in the immediate processing of electrical and geometrical data supplied by plant owners, and in certain cases turn out to be inadequate in representing complex configurations of power lines. Furthermore, none of them is preset for cyclic calculus to determine the time evolution of induction in a certain exposure area. Finally, the output data are not immediately importable by ArcView, the G.I.S. used by A.R.P.A. F.V.G., and it is not always possible to implement the territory orography to determine the field at specified heights above the ground. P.h.i.d.e.l., an innovative software, tackles and works out al l the above mentioned problems. The power line wires interested in its implementation are represented by poly lines, and the field is analytically calculated, with no further approximation, not even when more power lines are concerned. Therefore, the obtained results, when compared with those of other programs, are the closest to experimental measurements. The output data can be employed both in G.I.S. and Excel environments, allowing the immediate overlaying of digital cartography and the determining of the 3 and 10 ?T bands, in compliance with the Italian Decree of the President of the Council of Ministers of 8 July 2003. (authors)

  1. Effect of Magnetic Field on Entropy Generation Due to Laminar Forced Convection Past a Horizontal Flat Plate

    OpenAIRE

    Moh'd A. Al-Nimr; Renhe A. Damseh; Mohammed Q. Al-Odat

    2004-01-01

    Magnetic field effect on local entropy generation due to steady two-dimensional laminar forced convection flow past a horizontal plate was numerically investigated. This study was focused on the entropy generation characteristics and its dependency on various dimensionless parameters. The effect of various dimensionless parameters, such as Hartmann number (Ha), Eckert number (Ec), Prandtl number (Pr), Joule heating parameter (R) and the free stream temperature parameter (θ∞) on the en...

  2. Intermediate frequency magnetic field generated by a wireless power transmission device does not cause genotoxicity in vitro.

    Science.gov (United States)

    Shi, Dejing; Zhu, Chunbo; Lu, Rengui; Mao, Shitong; Qi, Yanhua

    2014-10-01

    The aim of this study was to evaluate effects of intermediate frequency magnetic fields (IFMF) generated by a wireless power transmission (WPT) based on magnetic resonance from the perspective of cellular genotoxicity on cultured human lens epithelial cells (HLECs). We evaluated the effects of exposure to 90?kHz magnetic fields at 93.36?µT on cellular genotoxicity in vitro for 2 and 4?h. The magnetic flux density is approximately 3.5 times higher than the reference level recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines. For assessment of genotoxicity, we studied cellular proliferation, apoptosis and DNA damage by Cell Counting Kit-8 (CCK-8) assay, flow cytometry analysis, alkaline comet assay and phosphorylated histone H2AX (?H2AX) foci formation test. We did not detect any effect of a 90?kHz IFMF generated by WPT based on magnetic resonance on cell proliferation, apoptosis, comet assay, and ?H2AX foci formation test. Our results indicated that exposure to 90?kHz IFMF generated by WPT based on magnetic resonance at 93.36?µT for 2 and 4?h does not cause detectable cellular genotoxicity. PMID:25196478

  3. Heat generation ability in AC magnetic field and their computer simulation for Ti tube filled with ferrite powder

    International Nuclear Information System (INIS)

    The heat generation ability of needle-type materials was studied for the application of thermal coagulation therapy in an AC magnetic field. Although the Ti tube without the MgFe2O4 powder or Ti rod showed poor heat generation abilities in an AC magnetic field, the temperature was significantly increased by the presence of ferrite powder in the Ti tube. We confirmed using a computer simulation that the eddy loss of the Ti tube was increased by the enhanced magnetic flux density due to the ferrite powder in the Ti tube. The heat generation of the ferrite filled Ti tube was increased by utilization of the quenched MgFe2O4 powder from elevated temperature. The relative magnetic permeability of the quenched ferrite was enhanced with the decrease in the inverse ratio of the cubic spinel structure. The heat generation ability was increased with the increase in the relative magnetic permeability of the Ti tube with ferrite powder. The calculated joule loss based on the experimental results showed an agreement with those using the computer simulation.

  4. Photon echoes generated by reversing magnetic field gradients in a rubidium vapour

    CERN Document Server

    Hétet, G; Sparkes, B; Oblak, D; Lam, P K; Buchler, B C

    2008-01-01

    We propose a photon echo quantum memory scheme using detuned Raman coupling to long lived ground states. In contrast to previous 3-level schemes based on controlled reversible inhomogeneous broadening that use sequences of $\\pi$-pulses, the scheme does not require accurate control of the coupling dynamics to the ground states. We present a proof of principle experimental realization of our proposal using rubidium atoms in a warm vapour cell. The Raman resonance line is broadened using a magnetic field that varies linearly along the direction of light propagation. Inverting the magnetic field gradient rephases the atomic dipoles and re-emits the light pulse in the forward direction.

  5. Generation of 1.5-kW, 1-THz Coherent Radiation from a Gyrotron with a Pulsed Magnetic Field

    International Nuclear Information System (INIS)

    To cover a so-called terahertz gap in available sources of coherent electromagnetic radiation, the gyrotron with a pulsed solenoid producing up to a 40 T magnetic field has been designed, manufactured, and tested. At a 38.5 T magnetic field, the gyrotron generated coherent radiation at 1.022 THz frequency in 50 ?sec pulses. The microwave power and energy per pulse were about 1.5 kW and 75 mJ, respectively. Details of the gyrotron design, manufacturing, operation and measurements of output radiation are given

  6. Dynamo generation of magnetic field in the white dwarf GD 358

    Science.gov (United States)

    Markiel, J. Andrew; Thomas, John H.; Van Horn, H. M.

    1994-01-01

    On the basis of Whole Earth Telescope observations of the g-mode oscillation spectrum of the white dwarf GD 358, Winget et al. find evidence for significant differential rotation and for a time-varying magnetic field concentrated in the surface layers of this star. Here we argue on theoretical grounds that this magnetic field is produced by an alpha omega dynamo operating in the lower part of a surface convection zone in GD 358. Our argument is based on numerical solutions of the nonlinear, local dynamo equations of Robinson & Durney, with specific parameters based on our detailed models of white-dwarf convective envelopes, and universal constants determined by a calibration with the the Sun's dynamo. The calculations suggest a dynamo cycle period of about 6 years for the fundamental mode, and periods as short as 1 year for the higher-order modes that are expected to dominate in view of the large dynamo number we estimate for GD 358. These dynamo periods are consistent with the changes in the magnetic field of GD 358 over the span of 1 month inferred by Winget et. al. from their observations. Our calculations also suggest a peak dynamo magnetic field strength at the base of the surface convection zone of about 1800 G, which is consistent with the field strength inferred from the observations.

  7. Self-consistent modeling of induced magnetic field in Titan's atmosphere accounting for the generation of Schumann resonance

    Science.gov (United States)

    Béghin, Christian

    2015-02-01

    This model is worked out in the frame of physical mechanisms proposed in previous studies accounting for the generation and the observation of an atypical Schumann Resonance (SR) during the descent of the Huygens Probe in the Titan's atmosphere on 14 January 2005. While Titan is staying inside the subsonic co-rotating magnetosphere of Saturn, a secondary magnetic field carrying an Extremely Low Frequency (ELF) modulation is shown to be generated through ion-acoustic instabilities of the Pedersen current sheets induced at the interface region between the impacting magnetospheric plasma and Titan's ionosphere. The stronger induced magnetic field components are focused within field-aligned arcs-like structures hanging down the current sheets, with minimum amplitude of about 0.3 nT throughout the ramside hemisphere from the ionopause down to the Moon surface, including the icy crust and its interface with a conductive water ocean. The deep penetration of the modulated magnetic field in the atmosphere is thought to be allowed thanks to the force balance between the average temporal variations of thermal and magnetic pressures within the field-aligned arcs. However, there is a first cause of diffusion of the ELF magnetic components, probably due to feeding one, or eventually several SR eigenmodes. A second leakage source is ascribed to a system of eddy-Foucault currents assumed to be induced through the buried water ocean. The amplitude spectrum distribution of the induced ELF magnetic field components inside the SR cavity is found fully consistent with the measurements of the Huygens wave-field strength. Waiting for expected future in-situ exploration of Titan's lower atmosphere and the surface, the Huygens data are the only experimental means available to date for constraining the proposed model.

  8. Diode with magnetic insulation and Br field as a generator of power microsecond ion beam

    International Nuclear Information System (INIS)

    Results of investigations into the generation of microsecond duration high-power ion beam in a plane magnetoisolated diode with an external isolating field with radial distribution are presented. The investigations are conducted using a microsecond generator operating in the regime of generating positive high-voltage ?600 kV amplitude pulses. Ring-type cross section ion beam consisting mainly of H+ and C+ ions is studied. The energy range occupied by the major part of the ions generated makes up 300-500 keV. The complete energy store of the beam extracted from the diode makes up 10 kJ, the generation efficiency is 60%

  9. Magnetic field generation in the lunar core: The role of inner core growth

    Science.gov (United States)

    Scheinberg, A.; Soderlund, K. M.; Schubert, G.

    2015-07-01

    The source of the magnetic field recorded in the lunar crust remains an unresolved problem. The field was most likely produced by a self-sustaining dynamo in the Moon's electrically conducting metal core, but heat flux across the core-mantle boundary was probably insufficient to power a dynamo for the field's currently known duration from 4.2 to 3.56 Ga. Since seismic measurements indicate the existence of a solid iron inner core in addition to a still-liquid iron alloy outer core, inner core solidification and its associated thermochemically driven convection in the outer core could have been responsible for extending the dynamo's lifetime even in the absence of superadiabatic heat flux. Here we present a coupled mantle-core thermal evolution model of the Moon and show that core solidification could explain the onset and shutoff of the lunar dynamo consistent with the global magnetic field inferred from the paleomagnetic record.

  10. High energy micro electron beam generation using chirped laser pulse in the presence of an axial magnetic field

    Science.gov (United States)

    Akou, H.; Hamedi, M.

    2015-10-01

    In this paper, the generation of high-quality and high-energy micro electron beam in vacuum by a chirped Gaussian laser pulse in the presence of an axial magnetic field is numerically investigated. The features of energy and angular spectra, emittances, and position distribution of electron beam are compared in two cases, i.e., in the presence and absence of an external magnetic field. The electron beam is accelerated with higher energy and qualified in spatial distribution in the presence of the magnetic field. The presence of an axial magnetic field improves electron beam spatial quality as well as its gained energy through keeping the electron motion parallel to the direction of propagation for longer distances. It has been found that a 64 ?m electron bunch with about MeV initial energy becomes a 20 ?m electron beam with high energy of the order of GeV, after interacting with a laser pulse in the presence of an external magnetic field.

  11. Study and realization of a power circuit of a superconducting dipole generator of a magnetic field

    International Nuclear Information System (INIS)

    The project of experimental reactor building on controlled fusion (I.T.E.R) needed the development of a superconducting cable made of niobium-tin. Tested with a current of fifty kilo amperes under a twelve tesla constant field, this cable has to be tested under a variable field. The installation of the power circuit of the dipole field generator, consisted to the study and realization of the four following points: an important power cable; a tension protection organ of the dipole, under a seventeen milli Henrys inductance and four kilo amperes; a current regulating system given by the generator; a complete pilot system of the test station

  12. A magnetically isolated diode with B?-field as a generator of high-power microsecond ion beam

    International Nuclear Information System (INIS)

    The results of a study of the generation of a high-power microsecond ion beam in a planar magnetically isolated diode with external radially distributed isolating field are presented. A ring cross-section ion beam consisting mainly of H+ and C+ ions was studied. The energy range of most of the generated ions is 300-500 keV. The total energy stored in the beam extracted from the diode is 10 kJ and the generation efficiency reaches 60%. 5 refs., 4 figs

  13. The magnetic shear-current effect: generation of large-scale magnetic fields by the small-scale dynamo

    CERN Document Server

    Squire, Jonathan

    2015-01-01

    A novel large-scale dynamo mechanism, the magnetic shear-current effect, is discussed and explored. The effect relies on the interaction of magnetic fluctuations with a mean shear flow, meaning the saturated state of the small-scale dynamo can drive a large-scale dynamo -- in some sense the inverse of dynamo quenching. The dynamo is nonhelical, with the mean-field $\\alpha$ coefficient zero, and is caused by the interaction between an off-diagonal component of the turbulent resistivity and the stretching of the large-scale field by shear flow. Following up on previous numerical and analytic work, this paper presents further details of the numerical evidence for the effect, as well as an heuristic description of how magnetic fluctuations can interact with shear flow to produce the required electromotive force. The pressure response of the fluid is fundamental to this mechanism, which helps explain why the magnetic effect is stronger than its kinematic cousin, and the basic idea is related to the well-known lack...

  14. Cosmological magnetic fields

    OpenAIRE

    Olinto, Angela V.

    2000-01-01

    Magnetic fields are observed on nearly all scales in the universe, from stars and galaxies upto galaxy clusters and even beyond. The origin of cosmic magnetic fields is still an open question, however a large class of models puts its origin in the very early universe. A magnetic dynamo amplifying an initial seed magnetic field could explain the present day strength of the galactic magnetic field. However, it is still an open problem how and when this initial magnetic field w...

  15. Effect of self-generated magnetic field on the two-plasmon decay instability in a laser-produced plasma

    International Nuclear Information System (INIS)

    In this paper we have made a theoretical investigation on the two-plasmon decay instability of laser radiation in the presence of the self-generated magnetic field at the quarter-critical density region in a laser-produced plasma. The Vlasov equation in terms of guiding centre coordinates has been employed to obtain the non-linear response of electrons in the plasma. The threshold power density of the incident laser radiation for the two-plasmon decay instability is always exceeded in currently employed power densities in laser-target experiments and above the threshold the growth rate of the instability is quite large. It is also noticed that the self-generated magnetic field enhances the threshold to a large extent, thus drastically reducing the growth rate of the instability. (author)

  16. Magnetic Field Generation and Energy Confinement with Te> 500 eV in the SSPX Spheromak

    Science.gov (United States)

    Hudson, B.

    2007-11-01

    The understanding of confinement and energy transport in spheromaks is key the understanding the physics of spheromak formation and self-organization as well as addressing the feasibility of the concept as a reactor scenario. In the Sustained Spheromak Physics eXperiment (SSPX), increased understanding of the physics in building and sustaining self-organized magnetic equilibria has resulted in record electron temperatures Te> 500 eV and plasma currents of ˜ 1 MA on the magnetic axis. We find that the highest edge magnetic field magnitudes (and correspondingly high Te) is achieved when ?=?0Igun ?gun is near (but slightly below) the Kruskal-Shafranov instability limit ?KS2?L12.6,-1 where L is the length of the flux-conserver (0.5 m). Building on previously reported results, power-balance analysis has shown levels of electron thermal transport ?ebank we are able to highly tailor the gun current to take advantage of the sensitive dependence of spheromak performance on the plasma ?. When in this optimum operating range we also find that the efficiency of field build-up (defined as the ratio of edge poloidal magnetic field to gun current) is increased 20% over prior results, to ˜1.0 T/MA. Additionally this brings the efficiency of spheromak formation into numerical agreement with results from the NIMROD 3-D MHD code. Plasma energy evolution has been studied by taking time-resolved measurements of Te(r) and ne(r) indicating a distinct and robust feature of spheromak formation; a hollow-to-peaked temperature transition with an inverse relationship to the electron density. This feature, as well as sub-microsecond transport, is being studied with the upgrade of the Thomson scattering diagnostic to double-pulse operation. We also present recent results of the impact of charge-exchange losses on overall power balance and estimates of the plasma ion temperature as measured with a neutral particle analyzer.

  17. Effect of Magnetic Field on Entropy Generation Due to Laminar Forced Convection Past a Horizontal Flat Plate

    Directory of Open Access Journals (Sweden)

    Moh'd A. Al-Nimr

    2004-06-01

    Full Text Available Magnetic field effect on local entropy generation due to steady two-dimensional laminar forced convection flow past a horizontal plate was numerically investigated. This study was focused on the entropy generation characteristics and its dependency on various dimensionless parameters. The effect of various dimensionless parameters, such as Hartmann number (Ha, Eckert number (Ec, Prandtl number (Pr, Joule heating parameter (R and the free stream temperature parameter (θ∞ on the entropy generation characteristics is analyzed. The dimensionless governing equations in Cartesian coordinate were solved by an implicit finite difference technique. The solutions were carried out for Ha2=0.5-3, Ec=0.01-0.05, Pr=1-5 and θ∞=1.1-2.5. It was found that, the entropy generation increased with increasing Ha, Ec and R. While, increasing the free stream temperature parameter, and Prandtl number tend to decrease the local entropy generation.

  18. Ocean circulation generated magnetic signals

    DEFF Research Database (Denmark)

    Manoj, C.; Kuvshinov, A.

    2006-01-01

    Conducting ocean water, as it flows through the Earth's magnetic field, generates secondary electric and magnetic fields. An assessment of the ocean-generated magnetic fields and their detectability may be of importance for geomagnetism and oceanography. Motivated by the clear identification of ocean tidal signatures in the CHAMP magnetic field data we estimate the ocean magnetic signals of steady flow using a global 3-D EM numerical solution. The required velocity data are from the ECCO ocean circulation experiment and alternatively from the OCCAM model for higher resolution. We assume an Earth's conductivity model with a surface thin shell of variable conductance with a realistic ID mantle underneath. Simulations using both models predict an amplitude range of +/-2 nT at Swarm altitude (430 km). However at sea level, the higher resolution simulation predicts a higher strength of the magnetic field, as compared to the ECCO simulation. Besides the expected signatures of the global circulation patterns, we find significant seasonal variability of ocean magnetic signals in the Indian and Western Pacific Oceans. Compared to seasonal variation, interannual variations produce weaker signals.

  19. Containment of an adiabatic plasma on magnetic lines of force by a self-generated electrostatic field

    International Nuclear Information System (INIS)

    One component of a three-fluid adiabatic plasma is under certain conditions contained in a restricted region of space by a large-scale electrostatic field generated within the plasma. The containment is discussed here for plasma consisting of ions and two populations of electrons characterized by different pitch angle distribution functions. The 'bouncing' motion of electrons along 'open' fieldlines between a magnetic mirror and an 'electrostatic' mirror produces a velocity distribution function similar to that generated by 'bouncing' particles on 'closed' fieldlines. (Auth.)

  20. ANALYSIS OF LOW TEMPERATURE PLASMA FLOW IN DISC-TYPE MHD GENERATOR IN STRONG MAGNETIC FIELD WITH EXTRATHERMAL IONIZATION

    Directory of Open Access Journals (Sweden)

    Józef Kunc

    1971-01-01

    Full Text Available Basing on the given flow model, low temperature plasma flow equations in disc-type MHD Generator in strong magnetic field are educed, taking into consideration the Hall's Component of Electrical Current. The He-Cs plasma ionization is considered as extrathermal ("electron heating" according to Kerrbrock's Model.The solutions of flow equations for low Mach numbers and numeral calculations based on the given parameters are presented also.The most typical functions for the MHD Generator theory are shown in the form of diagrams.

  1. Evaluation of human exposure to complex waveform magnetic fields generated by arc-welding equipment according to european safety standards

    International Nuclear Information System (INIS)

    In this paper, a procedure is described for the assessment of human exposure to magnetic fields with complex waveforms generated by arc-welding equipment. The work moves from the analysis of relevant guidelines and technical standards, underlining their strengths and their limits. Then, the procedure is described with particular attention to the techniques used to treat complex waveform fields. Finally, the procedure is applied to concrete cases encountered in the workplace. The discussion of the results highlights the critical points in the procedure, as well as those related to the evolution of the technical and exposure standards. (authors)

  2. Generation of a quasisteady electromagnetic field by a distributed magnetic dipole moving in a collisionless plasma

    International Nuclear Information System (INIS)

    The problem of the excitation of quasisteady electromagnetic fields by a moving dipole with a moment directed perpendicularly to its velocity is solved using the linear theory of particle emission based on the kinetic equation for a collisionless plasma. A multipole representation is derived for the fields at large and small distances from the dipole. The quasisteady electromagnetic fields excited by the dipole are squeezed against it. The currents in the plasma screen the field of the dipole, and an anomalous skin region with a typical size r/sub G/ = (?/sub ?/ ??/2 ?/sub p//sub ?/ 2v'/c2v/sub ?/)/sup -1/2/ forms (?/sub p//sub ?/ is the plasma frequency, v' is the velocity of the dipole, v/sub ?/ is the thermal velocity, and c is the velocity of light). In this anomalous skin region, the energy of the dipole is dissipated resonantly and converted into plasma particle energy through the excited quasisteady electromagnetic field. The rate of this process, the radiation resistance, and the stopping force exerted on the dipole are all calculated. An anomalous collisionless magnetic Reynolds number is defined. This Reynolds number characterizes the role played by conductivity effects in a collisionless plasma

  3. Simulation Study of Magnetic Fields Generated by the Electromagnetic Filamentation Instability

    Science.gov (United States)

    Nishikawa, K.-I.; Ramirez-Ruiz, E.; Hardee, P.; Hededal, C. B.; Mizuno, Y.; Fishman, G. J.

    2007-01-01

    We have investigated the effects of plasma instabilities driven by rapid e(sup plus or minus) pair cascades, which arise in the environment of GRB sources as a result of back-scattering of a seed fraction of the original spectrum. The injection of e(sup plus or minus) pairs induces strong streaming motions in the ambient medium. One therefore expects the pair-enriched medium ahead of the forward shock to be strongly sheared on length scales comparable to the radiation front thickness. Using three-dimensional particle-in-cell simulations, we show that plasma instabilities driven by these streaming e(sup plus or minus) pairs are responsible for the excitation of near-equipartition, turbulent magnetic fields. Our results reveal the importance of the electromagnetic filamentation instability in ensuring an effective coupling between e(sup plus or minus) pairs and ions, and may help explain the origin of large upstream fields in GRB shocks.

  4. Ultrafast Generation of Pseudo-magnetic Field for Valley Excitons in WSe2 Monolayers

    OpenAIRE

    Kim, Jonghwan; Hong, Xiaoping; Jin, Chenhao; Shi, Su-Fei; Chang, Chih-Yuan S.; Chiu, Ming-Hui; Li, Lain-Jong; Wang, Feng

    2014-01-01

    A new degree of freedom, the valley pseudospin, emerges in atomically thin two-dimensional transition metal dichalcogenides (MX2) and has attracted great scientific interest. The capability to manipulate the valley pseudospin, in analogy to the control of spin in spintronics, can open up exciting opportunities in valleytronics. Here we demonstrate that an ultrafast and ultrahigh valley pseudomagnetic field can be generated using circularly polarized femtosecond pulses to sel...

  5. Study of self-generated magnetic fields in laser produced plasmas using a three-channel polaro-interferometer

    Science.gov (United States)

    Prasad, Y. B. S. R.; Barnwal, S.; Bolkhovitinov, E. A.; Naik, P. A.; Kamath, M. P.; Joshi, A. S.; Kumbhare, S. R.; Rupasov, A. A.; Gupta, P. D.

    2011-12-01

    Self-generated magnetic fields produced in laser plasmas at moderate laser intensities have been measured using a three-channel polaro-interferometer. The main elements of this device are two birefringent calcite wedges placed between two crossed polarizers. Using this device, the spatial profiles of (a) the rotation angle (polarometry), (b) the electron density (interferometry), and (c) the transmitted probe beam intensity (shadowgraphy) are recorded simultaneously using a digital camera with a large format CCD in a single laser shot. Magnetic fields of 2-4 MG had been estimated in aluminum plasma at laser intensities ˜1013 W/cm2. It is also possible to use this device in other configurations to get time resolved information.

  6. Study of self-generated magnetic fields in laser produced plasmas using a three-channel polaro-interferometer

    International Nuclear Information System (INIS)

    Self-generated magnetic fields produced in laser plasmas at moderate laser intensities have been measured using a three-channel polaro-interferometer. The main elements of this device are two birefringent calcite wedges placed between two crossed polarizers. Using this device, the spatial profiles of (a) the rotation angle (polarometry), (b) the electron density (interferometry), and (c) the transmitted probe beam intensity (shadowgraphy) are recorded simultaneously using a digital camera with a large format CCD in a single laser shot. Magnetic fields of 2-4 MG had been estimated in aluminum plasma at laser intensities ?1013 W/cm2. It is also possible to use this device in other configurations to get time resolved information.

  7. Isotropic round-wire multifilament cuprate superconductor for generation of magnetic fields above 30 T

    CERN Document Server

    Larbalestier, D C; Trociewitz, U P; Kametani, F; Scheuerlein, C; Dalban-Canassy, M; Matras, M; Chen, P; Craig, N C; Lee, P J; Hellstrom, E E

    2014-01-01

    Magnets are the principal market for superconductors, but making attractive conductors out of the high-temperature cuprate superconductors (HTSs) has proved difficult because of the presence of high-angle grain boundaries that are generally believed to lower the critical current density, J$_c$. To minimize such grain boundary obstacles, HTS conductors such as REBa$_2$Cu$_3$O$_{7?x}$ and (Bi, Pb)$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10?x}$ are both made as tapes with a high aspect ratio and a large superconducting anisotropy. Here we report that Bi$_2$2Sr$_2$CaCu$_2$O$_{8?x}$ (Bi-2212) can be made in the much more desirable isotropic, round-wire, multifilament form that can be wound or cabled into arbitrary geometries and will be especially valuable for high-field NMR magnets beyond the present 1 GHz proton resonance limit of Nb$_3$Sn technology. An appealing attribute of this Bi-2212 conductor is that, being without macroscopic texture, it contains many high-angle grain boundaries but nevertheless attains a very hi...

  8. Wide-angle optics with strong magnetic fields for efficient generation of secondary-particle beams

    International Nuclear Information System (INIS)

    Optimization of the conditions for producing beams of secondary particles (positrons, antiproton, ?-mesons) has led to the development of projects at the Institute of Nuclear Physics of the Siberian Branch of the USSR Academy of Sciences aimed at creating optical devices with strong (50 to 300 kOE) pulsed magnetic fields and with a wide range of parameters determined by the type of secondary particles, their energy and the requirements for the beam characteristics. This theme encompasses two areas: the development of so-called parabolic lenses consisting of thin-walled shells of revolution about which current flows and which, by assigning the appropriate shape, facilitate aberration-free focusing of the particles for practically any collection angles, and of cylindrical lenses made of light metal (lithium, sodium) with cross-sectionally uniform current-density distribution for short focusing of beams

  9. Determination of self generated magnetic field and the plasma density using Cotton Mouton polarimetry with two color probes

    Directory of Open Access Journals (Sweden)

    Joshi A.S.

    2013-11-01

    Full Text Available Self generated magnetic fields (SGMF in laser produced plasmas are conventionally determined by measuring the Faraday rotation angle of a linearly polarized laser probe beam passing through the plasma along with the interferogram for obtaining plasma density. In this paper, we propose a new method to obtain the plasma density and the SGMF distribution from two simultaneous measurements of Cotton Mouton polarimetry of two linearly polarized probe beams of different colors that pass through plasma in a direction normal to the planar target. It is shown that this technique allows us to determine the distribution of SGMF and the plasma density without doing interferometry of laser produced plasmas.

  10. Laser-driven shock experiments in pre-compressed water: Implications for magnetic field generation in Icy Giant planets

    Energy Technology Data Exchange (ETDEWEB)

    Lee, K; Benedetti, L R; Jeanloz, R; Celliers, P M; Eggert, J H; Hicks, D G; Moon, S J; Mackinnon, A; Henry, E; Koenig, M; Benuzzi-Mounaix, A; Collins, G W

    2005-11-10

    Laser-driven shock compression of pre-compressed water (up to 1 GPa precompression) produces high-pressure, -temperature conditions in the water inducing two optical phenomena: opacity and reflectivity in the initially transparent water. The onset of reflectivity at infrared wavelengths can be interpreted as a semi-conductor to electronic conductor transition in water and is found at pressures above {approx}130 GPa for single-shocked samples pre-compressed to 1 GPa. This electronic conduction provides an additional contribution to the conductivity required for magnetic field generation in Icy Giant planets like Uranus and Neptune.

  11. Shocks in unmagnetized plasma with a shear flow: Stability and magnetic field generation

    Science.gov (United States)

    Dieckmann, M. E.; Bock, A.; Ahmed, H.; Doria, D.; Sarri, G.; Ynnerman, A.; Borghesi, M.

    2015-07-01

    A pair of curved shocks in a collisionless plasma is examined with a two-dimensional particle-in-cell simulation. The shocks are created by the collision of two electron-ion clouds at a speed that exceeds everywhere the threshold speed for shock formation. A variation of the collision speed along the initially planar collision boundary, which is comparable to the ion acoustic speed, yields a curvature of the shock that increases with time. The spatially varying Mach number of the shocks results in a variation of the downstream density in the direction along the shock boundary. This variation is eventually equilibrated by the thermal diffusion of ions. The pair of shocks is stable for tens of inverse ion plasma frequencies. The angle between the mean flow velocity vector of the inflowing upstream plasma and the shock's electrostatic field increases steadily during this time. The disalignment of both vectors gives rise to a rotational electron flow, which yields the growth of magnetic field patches that are coherent over tens of electron skin depths.

  12. Shocks in unmagnetized plasma with a shear flow: Stability and magnetic field generation

    CERN Document Server

    Dieckmann, M E; Ahmed, H; Doria, D; Sarri, G; Ynnerman, A; Borghesi, M

    2015-01-01

    A pair of curved shocks in a collisionless plasma is examined with a two-dimensional particle-in-cell (PIC) simulation. The shocks are created by the collision of two electron-ion clouds at a speed that exceeds everywhere the threshold speed for shock formation. A variation of the collision speed along the initially planar collision boundary, which is comparable to the ion acoustic speed, yields a curvature of the shock that increases with time. The spatially varying Mach number of the shocks results in a variation of the downstream density in the direction along the shock boundary. This variation is eventually equilibrated by the thermal diffusion of ions. The pair of shocks is stable for tens of inverse ion plasma frequencies. The angle between the mean flow velocity vector of the inflowing upstream plasma and the shock's electrostatic field increases steadily during this time. The disalignment of both vectors gives rise to a rotational electron flow, which yields the growth of magnetic field patches that a...

  13. Effect of an azimuthal magnetic field on neutron generation from a z-pinch

    International Nuclear Information System (INIS)

    An experimental study has been made on neutron emission from a Z-pinch device (with the energ of 15 kJ, minimum current approximately 3.5x105 A, initial current approximately 3x1011 A/s, a porcelain chamber, 28 cm in diameter and 50 cm long), the electrodes of which are short-circuited along the axis of the chamber by a conducting bus. It is shown that, when the azimuthal magnetic field, opposite to the field of the discharge current, is entrapped by plasma, the neutron yield increases 10-30 times. The yield grows with a rod diameter decrease; the dependence of emission on the current density in a pinch is of a threshold nature. The neutron radiation intensity is promoted by a growth of the e. m. f., accelerating deuterons, up to > or approximately 100 kV and by a possible elongation of the current filaments (and lines with H approximately O, respectively). The e. m. f. is excited along a pinch in the process of a deflecting repeated breakdown

  14. The Earth's Magnetic Field

    OpenAIRE

    Edda Lína Gunnarsdóttir 1988

    2012-01-01

    The Earth's magnetic field is essential for life on Earth, as we know it, to exist. It forms a magnetic shield around the planet, protecting it from high energy particles and radiation from the Sun, which can cause damage to life, power systems, orbiting satellites, astronauts and spacecrafts. This report contains a general overview of the Earth's magnetic field. The different sources that contribute to the total magnetic field are presented and the diverse variations in the field are describ...

  15. Geometrical Design of a Scalable Overlapping Planar Spiral Coil Array to Generate a Homogeneous Magnetic Field.

    Science.gov (United States)

    Jow, Uei-Ming; Ghovanloo, Maysam

    2012-12-21

    We present a design methodology for an overlapping hexagonal planar spiral coil (hex-PSC) array, optimized for creation of a homogenous magnetic field for wireless power transmission to randomly moving objects. The modular hex-PSC array has been implemented in the form of three parallel conductive layers, for which an iterative optimization procedure defines the PSC geometries. Since the overlapping hex-PSCs in different layers have different characteristics, the worst case coil-coupling condition should be designed to provide the maximum power transfer efficiency (PTE) in order to minimize the spatial received power fluctuations. In the worst case, the transmitter (Tx) hex-PSC is overlapped by six PSCs and surrounded by six other adjacent PSCs. Using a receiver (Rx) coil, 20 mm in radius, at the coupling distance of 78 mm and maximum lateral misalignment of 49.1 mm (1/?3 of the PSC radius) we can receive power at a PTE of 19.6% from the worst case PSC. Furthermore, we have studied the effects of Rx coil tilting and concluded that the PTE degrades significantly when ? > 60°. Solutions are: 1) activating two adjacent overlapping hex-PSCs simultaneously with out-of-phase excitations to create horizontal magnetic flux and 2) inclusion of a small energy storage element in the Rx module to maintain power in the worst case scenarios. In order to verify the proposed design methodology, we have developed the EnerCage system, which aims to power up biological instruments attached to or implanted in freely behaving small animal subjects' bodies in long-term electrophysiology experiments within large experimental arenas. PMID:24782576

  16. Energy transfer from a homopolar generator to a single turn coil toroidal field magnet

    International Nuclear Information System (INIS)

    The designs of busbars and switches to efficiently transfer energy to the IGNITEX (Texas Fusion Ignition Experiment), single-turn tokamak and to the IGNITEX Technology Demonstrator (ITD) are presented. The IGNITEX machine should produce and control an ignited plasma with ohmic heating alone. A proposed homopolar generator (HPG) power supply formed by 12, 1-GJ HPGs will power the toroidal field (TF) of the full-scale IGNITEX device. The objective of the ITD is to test the design, fabrication procedures, and operation of a single turn, 20 T, TF coil. The ITD will be driven by an existing 60 MJ, 9 MA power supply consisting of six, 10-MJ HPGs located at the Center for Electromechanics at The University of Texas at Austin (CEM-UT). Busbsar design considerations include physical integration, thermal and electromechanical stresses, material properties in liquid nitrogen, effects on circuit response, and resistive and inductive energy dissipation

  17. Ultrafast generation of pseudo-magnetic field for valley excitons in WSe2 monolayers

    Science.gov (United States)

    Kim, Jonghwan; Hong, Xiaoping; Jin, Chenhao; Shi, Su-Fei; Chang, Chih-Yuan S.; Chiu, Ming-Hui; Li, Lain-Jong; Wang, Feng

    2015-03-01

    The valley pseudospin emerges as a new degree of freedom in atomically thin two-dimensional transition metal dichalcogenides (MX2). In analogy to the control of spin in spintronics, the capability to manipulate the valley pseudospin can provide exciting opportunities in valleytronics. Here we present that femtosecond pulses with circular polarization can generate ultrafast and ultrahigh valley pseudomagnetic field in a monolayer MX2. Our polarization-resolved transient absorption measurement shows that the degeneracy of valley exciton transitions at K and K' valley in WSe2 monolayers can be lifted by optical Stark effect from the non-resonant pump. Energy splitting due to the optical Stark effect is linear with both the pump intensity and the inverse of pump detuning. We observe that valley-selective optical Stark effect can create an energy splitting more than 10 meV which corresponds to a pseudomagnetic field over 60 Tesla. Our study demonstrates efficient and ultrafast control of the valley excitons with optical light which can open up the possibility of coherent manipulation of the valley polarization in MX2.

  18. Global coupling at 660 km is proposed to explain plate tectonics and the generation of the earth's magnetic field

    CERN Document Server

    Garai, Jozsef

    2007-01-01

    The presence of low viscosity layers in the mantle is supported by line of geological and geophysical observations. Recent high pressure and temperature investigations indicated that partial carbonate melt should exist at the bottom of the lithosphere and at 660 km. The presence of few percent carbonate melt reduces the viscosity by several order of magnitude. The globally existing 660 km very low viscosity layer allows the development of differential rotation between the upper and lower mantle. This differential rotation between the 660 km outer shell and the rest of the earth offers a plausible explanation for plate tectonics and for the generation of the earth's magnetic field. Simple dynamo model is proposed, which able to reproduce all of the features of the contemporary and, within reasonable uncertainty, the paleomagnetic field. The model is also consistent with geological and geophysical observations.

  19. Applications of the computer codes FLUX2D and PHI3D for the electromagnetic analysis of compressed magnetic field generators and power flow channels

    International Nuclear Information System (INIS)

    The authors present the results of three electromagnetic field problems for compressed magnetic field generators and their associated power flow channels. The first problem is the computation of the transient magnetic field in a two-dimensional model of a helical generator during loading. The second problem is the three-dimensional eddy current patterns in a section of an armature beneath a bifurcation point of a helical winding. The authors' third problem is the calculation of the three-dimensional electrostatic fields in a region known as the post-hole convolute in which a rod connects the inner and outer walls of a system of three concentric cylinders through a hole in the middle cylinder. While analytic solutions exist for many electromagnetic filed problems in cases of special and ideal geometries, the solution of these and similar problems for the proper analysis and design of compressed magnetic field generators and their related hardware require computer simulations

  20. Magnetic fields generated by hydromagnetic dynamos at the low Prandtl number in dependence on the Ekman and magnetic Prandtl numbers.

    Czech Academy of Sciences Publication Activity Database

    Šimkanin, Ján; Hejda, Pavel

    2013-01-01

    Ro?. 217, April (2013), s. 22-30. ISSN 0031-9201 R&D Projects: GA AV ?R IAA300120704 Institutional support: RVO:67985530 Keywords : hydromagnetic dynamo * Prandtl number * magnetic Prandtl number * inertial forces Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 2.398, year: 2013

  1. Magnetic fields of Sun-like stars

    OpenAIRE

    Fares, R

    2013-01-01

    Magnetic fields play an important role at all stages of stellar evolution. In Sun-like stars, they are generated in the outer convective layers. Studying the large-scale magnetic fields of these stars enlightens our understanding of the field properties and gives us observational constraints for the field generation models. In this review, I summarise the current observational picture of the large-scale magnetic fields of Sun-like stars, in particular solar-twins and planet-...

  2. Electroweak Origin of Cosmological Magnetic Fields

    OpenAIRE

    Tornkvist, Ola

    1997-01-01

    Magnetic fields may have been generated in the electroweak phase transition through spontaneous symmetry breaking or through the subsequent dynamical evolution of semiclassical field configurations. Here I demonstrate explicitly how magnetic fields emerge spontaneously in the phase transition also when no gradients of the Higgs field are present. Using a simple model, I show that no magnetic fields are generated, at least initially, from classical two-bubble collisions in a ...

  3. Improved foilless Ku-band transit-time oscillator for generating gigawatt level microwave with low guiding magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Ling, Junpu; He, Juntao, E-mail: hejuntao12@163.com; Zhang, Jiande; Jiang, Tao; Hu, Yi [College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073 (China)

    2014-09-15

    An improved foilless Ku-band transit-time oscillator with low guiding magnetic field is proposed and investigated in this paper. With a non-uniform buncher and a coaxial TM{sub 02} mode dual-resonant reflector, this improved device can output gigawatt level Ku-band microwave with relatively compact radial dimensions. Besides the above virtue, this novel reflector also has the merits of high TEM reflectance, being more suitable for pre-modulating the electron beam and enhancing the conversion efficiency. Moreover, in order to further increase the conversion efficiency and lower the power saturation time, a depth-tunable coaxial collector and a resonant cavity located before the extractor are employed in our device. Main structure parameters of the device are optimized by particle in cell simulations. The typical simulation result is that, with a 380?kV, 8.2?kA beam guided by a magnetic field of about 0.6?T, 1.15?GW microwave pulse at 14.25?GHz is generated, yielding a conversion efficiency of about 37%.

  4. Cosmic Magnetic Fields

    OpenAIRE

    Pino, E. M. Gouveia Dal

    1999-01-01

    Most of the visible matter in the Universe is in a plasma state, or more specifically is composed of ionized or partially ionized gas permeated by magnetic fields. Thanks to recent advances on the theory and detection of cosmic magnetic fields there has been a worldwide growing interest in the study of their role on the formation of astrophysical sources and the structuring of the Universe. In this lecture, I will briefly review the importance of the cosmic magnetic fields b...

  5. Magnetic Field Created by Tile Permanent Magnets

    OpenAIRE

    Ravaud, Romain; Lemarquand, Guy; Lemarquand, Valérie

    2009-01-01

    This paper presents the analytical calculation of the three components of the magnetic field created by tile permanent magnets whose magnetization is either radial or axial. The calculations are based on the coulombian model of permanent magnets. The magnetic field is directly calculated, without the magnetic potential. Both axial and radial magnetization of the tiles are considered. The expressions obtained give the magnetic field in all the space. Such analytical expressions are very useful...

  6. Primordial magnetic fields

    OpenAIRE

    Giovannini, Massimo

    2002-01-01

    The explanation of the observed galactic magnetic fields may require the existence of a primordial magnetic field. Such a field may arise during the early cosmological phase transitions, or because of other particle physics related phenomena in the very early universe reviewed here. The turbulent evolution of the initial, randomly fluctuating microscopic field to a large-scale macroscopic field can be described in terms of a shell model, which provides an approximation to th...

  7. A technical note about Phidel: A new software for evaluating magnetic induction field generated by power lines

    International Nuclear Information System (INIS)

    The Regional Environment Protection Agency of Friuli Venezia Giulia (ARPA FVG, Italy) has performed an analysis on existing software designed to calculate magnetic induction field generated by power lines. As far as the agency's requirements are concerned the tested programs display some difficulties in the immediate processing of electrical and geometrical data supplied by plant owners, and in certain cases turn out to be inadequate in representing complex configurations of power lines. Phidel, an innovative software, tackles and works out all the above-mentioned problems. Therefore, the obtained results, when compared with those of other programs, are the closest to experimental measurements. The output data can be employed both in the GIS and Excel environments, allowing the immediate overlaying of digital cartography and the determining of the 3 and 10 ?T bands, in compliance with the Italian Decree of the President of the Council of Ministers of 8 July 2003. (authors)

  8. Static magnetic fields enhance turbulence

    CERN Document Server

    Pothérat, Alban

    2015-01-01

    More often than not, turbulence occurs under the influence of external fields, mostly rotation and magnetic fields generated either by planets, stellar objects or by an industrial environment. Their effect on the anisotropy and the dissipative behaviour of turbulence is recognised but complex, and it is still difficult to even tell whether they enhance or dampen turbulence. For example, externally imposed magnetic fields suppress free turbulence in electrically conducting fluids (Moffatt 1967), and make it two-dimensional (2D) (Sommeria & Moreau 1982); but their effect on the intensity of forced turbulence, as in pipes, convective flows or otherwise, is not clear. We shall prove that since two-dimensionalisation preferentially affects larger scales, these undergo much less dissipation and sustain intense turbulent fluctuations. When higher magnetic fields are imposed, quasi-2D structures retain more kinetic energy, so that rather than suppressing forced turbulence, external magnetic fields indirectly enha...

  9. Primordial magnetic field limits from cosmological data

    International Nuclear Information System (INIS)

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

  10. Ferromagnetic Domain Wall and Primeval Magnetic Field

    OpenAIRE

    Iwazaki, Aiichi

    1996-01-01

    We show that coherent magnetic field is generated spontaneously when a large domain wall is created in the early universe. It is caused by two dimensional massless fermions bounded to the domain wall soliton. We point out that the magnetic field is a candidate of primordial magnetic field.

  11. Pre-ionization and spectroscopic diagnostic of plasma generated and confined by magnetic fields

    International Nuclear Information System (INIS)

    A ?-pinch system has been constructed with pre-heating devices with a total energy of 2 kJ. During this experiment a He Plasma was studied using the following three different diagnostics. a) Magnetic Probes b) Visible Spectroscopy using the Optical Multichannel Analyser - OMA c) Image Converter Camera. The experimental results have been checked with existing theoretical models. The electrical characteristics of the system were determined with the magnetic probe. The Doppler and Stark broadening effects of the ?o = 4686 (angstrom) (HeII) have been used to determine the ionic temperature and electronic density respectively. The time evolution of these parameters was obtained using the OMA. The dynamics of the plasma were observed by high speed photography. Instabilities in the plasma columm have been observed. Good agreement between the experimental and theoretical values was obtained. (author)

  12. Physics of semiconductors in high magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Ortenberg, M von [Chair for Magnetotransport in Solids, Institute of Physics of the Humboldt University at Berlin, Newtonstrasse 15, D-12489 Berlin (Germany)

    2006-11-15

    A review of experiments on semiconductors in high magnetic fields is presented with special emphasis on transient megagauss fields generated by the singleturn coil and explosive flux-compression. Both, techniques of field generation and the special consequences of transient magnetic fields on the sample system will be discussed thoroughly. In detail several magneto-transmission experiments using 10.6 im wavelength radiation on bulk and nanostructured semiconductors will be presented in addition to special features of magnetization behavior.

  13. Numerical study and modeling of hydrodynamic instabilities in the context of inertial confinement fusion in the presence of self-generated magnetic fields

    International Nuclear Information System (INIS)

    In the context of inertial confinement fusion we investigate effects of magnetic fields on the development in the linear regime of two hydrodynamic instabilities: Richtmyer-Meshkov instability using ideal magnetohydrodynamics and ablative Rayleigh-Taylor instability in both acceleration and deceleration stages. Direct numerical simulations with a linear perturbation code enable us to confirm the stabilizing effect of the component of the magnetic field along the perturbations wave vector. The amplitude doesn't grow linearly in time but experiences oscillations instead. The compressibility taken into account in the code does not affect predictions given by an already existing impulsive and incompressible model. As far as Rayleigh-Taylor instability is concerned we study the effects of self-generated magnetic fields that arise from the development of the instability itself. In the acceleration stage we perform two dimensional simulations in planar geometry. We show that magnetic fields of about 1 T can be generated and that the instability growth transits more rapidly into nonlinear growth with the enhancement of the development of the third harmonic. We also propose an adaptation of an existing model that aims at studying thermal conductivity anisotropy effects, to take into account the effects of the self-generated magnetic fields on the Rayleigh-Taylor instability growth rate. Finally, in the deceleration stage, we perform two dimensional simulations in cylindrical geometry that take into account self-generation of magnetic fields due to the instability development. It reveals magnetic fields of about several thousands of Teslas that are not strong enough though to affect the instability behavior. (author)

  14. Field free line magnetic particle imaging

    CERN Document Server

    Erbe, Marlitt

    2014-01-01

    Marlitt Erbe provides a detailed introduction into the young research field of Magnetic Particle Imaging (MPI) and field free line (FFL) imaging in particular. She derives a mathematical description of magnetic field generation for FFL imaging in MPI. To substantiate the simulation studies on magnetic FFL generation with a proof-of-concept, the author introduces the FFL field demonstrator, which provides the world's first experimentally generated rotated and translated magnetic FFL field complying with the requirements for FFL reconstruction. Furthermore, she proposes a scanner design of consi

  15. Superhorizon magnetic fields

    CERN Document Server

    Campanelli, Leonardo

    2015-01-01

    [Abridged] We analyze the evolution of superhorizon-scale magnetic fields from the end of inflation till today. Whatever is the mechanism responsible for their generation during inflation, we find that a given magnetic mode with wavenumber $k$ evolves, after inflation, according to the values of $k\\eta_e$, $n_{\\mathbf{k}}$, and $\\Omega_k$, where $\\eta_e$ is the conformal time at the end of inflation, $n_{\\mathbf{k}}$ is the number density spectrum of inflation-produced photons, and $\\Omega_k$ is the phase difference between the two Bogolubov coefficients which characterize the state of that mode at the end of inflation. For any realistic inflationary magnetogenesis scenario, we find that $n_{\\mathbf{k}}^{-1} \\ll |k\\eta_e| \\ll 1$, and three evolutionary scenarios are possible: ($i$) $|\\Omega_k \\mp \\pi| = \\mathcal{O}(1)$, in which case the evolution of the magnetic spectrum $B_k(\\eta)$ is adiabatic, $a^2B_k(\\eta) = \\mbox{const}$, with $a$ being the expansion parameter; ($ii$) $|\\Omega_k \\mp \\pi| \\ll |k\\eta_e|$,...

  16. Magnetic field on board

    International Nuclear Information System (INIS)

    Here, the calculation of the magnetic field on board ships is performed, using matrix calculus, in a similar way as when the magnetic field in matter is studied. Thus the final formulas are written in a more compact form and they are obtained through a simpler way, more suitable for the university education. (Author)

  17. Stability of Magnetic Fluids in Magnetic Fields

    OpenAIRE

    I.M. Arefyev; T.A. Arefyeva

    2014-01-01

    Stability of magnetic fluids in magnetic fields is one of the major factors determining the possibility of their practical use and resource of their exploitation. This paper examines the stability of magnetic fluids based on kerosene in constant and variable magnetic fields. It is shown that the synthesized magnetic fluids are stable during long-term exposure to magnetic fields and can be used as the working fluid in a number of magnetic fluid devices.

  18. Computer code for generating a magnetic field free region in an OHMIC heating coil system

    International Nuclear Information System (INIS)

    A computer code was developed which allows the user to specify any arbitrary straight or curved line along which the ohmic heating coils will be placed. This line is chosen so as to avoid interference with TF coils, vacuum vessels, structural supports, etc. The number of equal turns or groups of turns to be used in the ohmic heating system is then read into the program. The computer code returns the exact location of each turn along the specified line so as to minimize the stray field within the volume bounded by the line. As an example of the efficacy of this code to produce a field free region the PDX device required a flux value of approximately 10 KG. As the coil boundary is traversed at 61 cm the stray field value falls sharply to give values of approximately 8 gauss at the plasma edge located at 100 cm and a complete null at 140 cm

  19. N-flationary magnetic fields

    CERN Document Server

    Anber, M M; Anber, Mohamed M.; Sorbo, Lorenzo

    2007-01-01

    There is increasing interest in the role played by pseudo Nambu-Goldstone bosons (pNGBs) in the construction of string-inspired models of inflation. In these models the inflaton is expected to be coupled to gauge fields, and will lead to the generation of magnetic fields that can be of cosmological interest. We study the production of such fields mainly focusing on the model of N-flation, where the collective effect of several pNGBs drives inflation. Because the produced fields are maximally helical, inverse cascade processes in the primordial plasma increase significantly their coherence length. We discuss under what conditions inflation driven by pNGBs can account for the observed cosmological magnetic fields. A constraint on the parameters of this class of inflationary scenarios is also derived by requiring that the magnetic field does not backreact on the inflating background.

  20. Thermally radiative three-dimensional flow of Jeffrey nanofluid with internal heat generation and magnetic field

    Science.gov (United States)

    Shehzad, S. A.; Abdullah, Z.; Alsaedi, A.; Abbasi, F. M.; Hayat, T.

    2016-01-01

    This research work addresses the three-dimensional hydromagnetic flow of Jeffrey fluid with nanoparticles. Flow is generated by a bidirectional stretching surface. The effects of thermal radiation and internal heat generation are encountered in energy expressions. More realistic convective boundary conditions at the surface are employed instead of constant surface temperature and mass species conditions. Boundary layer assumptions lead to the governing non-linear mathematical model. Resulting equations through momentum, energy and mass species are made dimensionless using suitable variables. The solution expressions of dimensionless velocities, temperature and nanoparticle concentration have been computed for the convergent series solutions. The impacts of interesting parameters on the dimensionless quantities are displayed and interpreted. The values of physical quantities are computed and analyzed.

  1. Magnetic fields in the early universe

    OpenAIRE

    Subramanian, Kandaswamy

    2009-01-01

    The observed galactic magnetic fields may have a primordial origin. I briefly review the observations, their interpretation in terms of the dynamo theory, and the current limits on cosmological magnetic fields. Several possible mechanisms for generating a primordial magnetic field are then discussed. Turbulence and the evolution of the microscopic fields to macroscopic fields is described in terms of a shell model, which provides an approximation to the full magnetohydrodyna...

  2. Passive Magnetic Shielding in Gradient Fields

    CERN Document Server

    Bidinosti, C P

    2013-01-01

    The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied. It is found that for concentric cylindrical or spherical shells of high permeability material, higher order multipoles in the magnetic field are shielded progressively better, by a factor related to the order of the multipole. In regard to the design of internal coil systems for the generation of uniform internal fields, we show how one can take advantage of the coupling of the coils to the innermost magnetic shield to further optimize the uniformity of the field. These results demonstrate quantitatively a phenomenon that was previously well-known qualitatively: that the resultant magnetic field within a passively magnetically shielded region can be much more uniform than the applied magnetic field itself. Furthermore we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields clos...

  3. The Braginskii model of the Rayleigh-Taylor instability. I. Effects of self-generated magnetic fields and thermal conduction in two dimensions

    Science.gov (United States)

    Modica, Frank; Plewa, Tomasz; Zhiglo, Andrey

    2013-12-01

    There exists a substantial disagreement between computer simulation results and high-energy density laboratory experiments of the Rayleigh-Taylor instability [1]. Motivated by the observed discrepancies in morphology and growth rates, we attempt to bring simulations and experiments into better agreement by extending the classic purely hydrodynamic model to include self-generation of magnetic fields and anisotropic thermal conduction.

  4. The Braginskii model of the Rayleigh-Taylor instability. I. Effects of self-generated magnetic fields and thermal conduction in two dimensions

    CERN Document Server

    Modica, Frank; Zhiglo, Andrey

    2013-01-01

    (abridged) There exists a substantial disagreement between computer simulation results and high-energy density laboratory experiments of the Rayleigh-Taylor instability Kuranz et al. (2010). We adopt the Braginskii formulation for transport in hot, dense plasma, implement and verify the additional physics modules, and conduct a computational study of a single-mode RTI in two dimensions with various combinations of the newly implemented modules. We find that magnetic fields reach levels on the order of 11 MG in the absence of thermal conduction. We observe denting of the RT spike tip and generation of additional higher order modes as a result of these fields. Contrary to interpretation presented in earlier work Nishiguchi (2002), the additional mode is not generated due to modified anisotropic heat transport effects but due to dynamical effect of self-generated magnetic fields. The main effects of thermal conduction are a reduction of the RT instability growth rate (by about 20% for conditions considered here)...

  5. Magnetic fields in the early universe

    CERN Document Server

    Subramanian, Kandaswamy

    2009-01-01

    We give a pedagogical introduction to two aspects of magnetic fields in the early universe. We first focus on how to formulate electrodynamics in curved space time, defining appropriate magnetic and electric fields and writing Maxwell equations in terms of these fields. We then specialize to the case of magnetohydrodynamics in the expanding universe. We emphasize the usefulness of tetrads in this context. We then review the generation of magnetic fields during the inflationary era, deriving in detail the predicted magnetic and electric spectra for some models. We discuss potential problems arising from back reaction effects and from the large variation of the coupling constants required for such field generation.

  6. Dynamically Generated Anomalous Magnetic Moment in Massless QED

    OpenAIRE

    Ferrer, Efrain J.; de la Incera, Vivian

    2009-01-01

    In this paper we investigate the non-perturbative generation of an anomalous magnetic moment for massless fermions in the presence of an external magnetic field. In the context of massless QED in a magnetic field, we prove that the phenomenon of magnetic catalysis of chiral symmetry breaking, which has been associated in the literature with dynamical mass generation, is also responsible for the generation of a dynamical anomalous magnetic moment. As a consequence, the degene...

  7. Magnet Free Generators - 3rd Generation Wind Turbine Generators

    DEFF Research Database (Denmark)

    Jensen, Bogi Bech; Mijatovic, Nenad

    2013-01-01

    This paper presents an introduction to superconducting wind turbine generators, which are often referred to as 3rd generation wind turbine generators. Advantages and challenges of superconducting generators are presented with particular focus on possible weight and efficiency improvements. A comparison of the rare earth usage in different topologies of permanent magnet generators and superconducting generators is also presented.

  8. Electric & Magnetic Fields

    Science.gov (United States)

    ... Contents Description Electric and magnetic fields (EMFs) are invisible areas of energy, often referred to as radiation ... Freedom of Information Act Office of Inspector General Web Policies & Notices Contact Us Department of Health & Human ...

  9. The generation of magnetic field via convective motions in the photosphere, Alvén waves, and the origin of chromospheric spicules

    Science.gov (United States)

    Kropotkin, A. P.

    2011-12-01

    The basis is laid out for a theory relating various phenomena in the solar atmosphere, including localized concentrations of magnetic field at the bases of coronal magnetic arches, chromospheric spicules, twisted coronal magnetic flux tubes, and flows of energy carried by Alfvén waves propagating upward into the corona. The structure of photospheric currents localized in the vicinity of supergranule boundaries and excited by convective motions is studied. These currents exist primarily in a "dynamo layer" of sharply enhanced transverse conductivity, which forms in the weakly ionized thermal photospheric plasma located in the solar gravitational field. The motions of the electrons and ions in this layer have appreciably different characters: the ions are collisionly driven by the flows of neutral atoms, while the electrons drift in the crossed electric and magnetic fields. The electric field supporting the current arises due to the polarization of the electrons and ions. This field also gives rise to Alfvén perturbations that propagate upward into the corona, together with their associated longitudinal currents. The character of this "loading" makes the system of fields and currents uniquely defined. Moreover, the momentum flux carried by these Alfvén waves should be transferred to the cool chromospheric gas, facilitating the vertical ejection of this gas in the form of spicules, as was first proposed in 1992 by Haerendel.

  10. Conservative numerical methods for a two-temperature resistive MHD model with self-generated magnetic field term

    Directory of Open Access Journals (Sweden)

    Imbert-Gérard Lise-Marie

    2011-11-01

    Full Text Available We propose numerical methods on Cartesian meshes for solving the 2-D axisymmetric two-temperature resistivive magnetohydrodynamics equations with self-generated magnetic field and Braginskii’s [1] closures. These rely on a splitting of the complete system in several subsystems according to the nature of the underlying mathematical operator. The hyperbolic part is solved using conservative high-order dimensionally split Lagrange-remap schemes whereas semi-implicit diffusion operators have been developed for the thermal and resistive conduction equations. Source terms are treated explictly. Numerical results on the deceleration phase of an ICF implosion test problem are proposed, a benchmark which was initially proposed in [2]. Nous proposons dans cet article des méthodes numériques pour les équations de la magnétohydrodynamique résistive à deux températures avec champ magnétique auto-généré et relations de fermeture de Braginskii [1] en géométrie 2-D axisymétrique sur maillage cartésien. Celles-ci sont basées sur une décomposition du système complet selon la nature des opérateurs mathématiques sous-jacents. La partie hyperbolique est résolue par des schémas conservatifs Lagrange-projection d’ordre élevé en directions alternées tandis que des opérateurs de diffusion semi-implicites ont été développés pour les équations de conduction thermique et résistive. Les termes sources sont traités de manière explicite. Des résultats numériques sur un cas-test simulant la phase de décélération d’une implosion de capsule FCI sont proposés, ce benchmark ayant été initialement présenté dans [2].

  11. Magnetic field dosimeter development

    International Nuclear Information System (INIS)

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

  12. Generation of nuclear magnetic resonance images

    International Nuclear Information System (INIS)

    Two generation techniques of nuclear magnetic resonance images, the retro-projection and the direct transformation method are studied these techniques are based on the acquisition of NMR signals which phases and frequency components are codified in space by application of magnetic field gradients. The construction of magnet coils is discussed, in particular a suitable magnet geometry with polar pieces and air gap. The obtention of image contrast by T1 and T2 relaxation times reconstructed from generated signals using sequences such as spin-echo, inversion-recovery and stimulated echo, is discussed. The mathematical formalism of matrix solution for Bloch equations is also presented. (M.C.K.)

  13. On the possibility of generating and/or sustaining the reversed field pinch configurations by means of a transverse rotating magnetic field

    International Nuclear Information System (INIS)

    The generation of plasma currents using rotating fields is examined. Numerical studies show that, provided the amplitude of the applied rotating field exceeds some value, it completely penetrates the plasma and sets the electrons rotating. An experiment is described which uses this technique to generate a reversed field configuration. Attention is drawn to the usefulness of the technique in generating the equilibrium currents appropriate to a variety of plasma-field configurations

  14. Magnetic Resonance Imaging of time-varying magnetic fields from therapeutic devices

    OpenAIRE

    Hernandez-Garcia, Luis; Bhatia, Vivek; Prem-Kumar, Krishan; Ulfarsson, Magnus

    2013-01-01

    While magnetic resonance imaging of static magnetic fields generated by external probes has been previously demonstrated, there is an unmet need to image time-varying magnetic fields, such as those generated by transcranial magnetic stimulators or radiofrequency hyperthermia probes. A method to image such time-varying magnetic fields is introduced in this work. This article presents the theory behind the method and provides proof of concept by imaging time-varying magnetic fields generated by...

  15. Trapped magnetic field measurements on HTS bulk by peak controlled pulsed field magnetization

    International Nuclear Information System (INIS)

    For the past several years, we have studied the high-temperature superconducting (HTS) synchronous motor assembled with melt-textured Gd-Ba-Cu-O bulk magnets. If the single pulse field magnetizes a bulk effectively, size of electrical motor will become small for the strong magnetic field of the HTS magnets without reducing output power of motor. In the previous study, we showed that the HTS bulk was magnetized to excellent cone-shape magnetic field distribution by using the waveform control pulse magnetization (WCPM) method. The WCPM technique made possible the active control of the waveform on which magnetic flux motion depended. We generated the pulse waveform with controlled risetime for HTS bulk magnetization to suppress the magnetic flux motion which decreases magnetization efficiency. The pulsed maximum magnetic flux density with slow risetime is not beyond the maximum magnetic flux density which is trapped by the static field magnetization. But, as for applying the pulse which has fast risetime, the magnetic flux which exceed greatly the threshold penetrates the bulk and causes the disorder of the trapped magnetic distribution. This fact suggests the possibility that the threshold at pulsed magnetization influences the dynamic magnetic flux motion. In this study, Gd-Ba-Cu-O bulk is magnetized by the controlled arbitrary trapezoidal shape pulse, of which the maximum magnetic flux density is controlled not to exceed the threshold. We will present the trapped magnetic characteristics and the technique to generate the controlled pulsed field.

  16. Control of chaotic magnetic fields in tokamaks

    Scientific Electronic Library Online (English)

    I. L., Caldas; R. L., Viana; M. S. T., Araujo; A., Vannucci; E. C. da, Silva; K., Ullmann; M. V. A. P., Heller.

    2002-12-01

    Full Text Available Chaotic magnetic field lines play an important role in plasma confinement by tokamaks. They can either be generated in the plasma as a result of natural instabilities or artifficially produced by external conductors, like resonant helical windings and ergodic magnetic limiters. This is a review of w [...] orks carried out at the Universidade de São Paulo and Universidade Federal do Paraná on theoretical and experimental aspects of generation and control of chaotic magnetic field lines in tokamaks.

  17. Magnetic field control device

    International Nuclear Information System (INIS)

    The device of the present invention enables PID control to provide high speed response upon conducting feedback control of magnetic fields for confining plasmas of a thermonuclear device. That is, the device of the present invention receives a detection signal VB from a detection coil which is in proportion to a differentiated value of magnetic fields, together with a measured value Bdf for magnetic fields as an input. A signal prepared by intaking VB in the form of negative feedback control to a PI control signal obtained by proportionating/integration of a deviation between the Bdf and an aimed magnetic field value Brf, is defined as a control signal. The control signal is outputted to an electromagnet coil power source. D control, which has not be realized in the existent device, can be attained in the present invention, in addition to PI control. As a result, response speed of the magnetic field device can be improved compared with the prior art. (I.S.)

  18. ISR Radial Field Magnet

    CERN Multimedia

    1983-01-01

    There were 37 (normal) + 3 (special) Radial Field magnets in the ISR to adjust vertically the closed orbit. Gap heights and strengths were 200 mm and .12 Tm in the normal magnets, 220 mm and .18 Tm in the special ones. The core length was 430 mm in both types. Due to their small length as compared to the gap heights the end fringe field errors were very important and had to be compensated by suitably shaping the poles. In order to save on cables, as these magnets were located very far from their power supplies, the coils of the normal type magnets were formed by many turns of solid cpper conductor with some interleaved layers of hollow conductor directly cooled by circulating water

  19. Indoor localization using magnetic fields

    Science.gov (United States)

    Pathapati Subbu, Kalyan Sasidhar

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

  20. Assessment of Foetal Exposure to the Homogeneous Magnetic Field Harmonic Spectrum Generated by Electricity Transmission and Distribution Networks

    Directory of Open Access Journals (Sweden)

    Serena Fiocchi

    2015-04-01

    Full Text Available During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity quality assessment, in this study the exposure of high-resolution three-dimensional models of foetuses to the whole harmonic content of a uniform magnetic field with a fundamental frequency of 50 Hz, was assessed. The results show that the main contribution in terms of induced electric fields to the foetal exposure is given by the fundamental frequency component. The harmonic components add some contributions to the overall level of electric fields, however, due to the extremely low permitted amplitude of the harmonic components with respect to the fundamental, their amplitudes are low. The level of the induced electric field is also much lower than the limits suggested by the guidelines for general public exposure, when the amplitude of the incident magnetic field is set at the maximum permitted level.

  1. Assessment of foetal exposure to the homogeneous magnetic field harmonic spectrum generated by electricity transmission and distribution networks.

    Science.gov (United States)

    Fiocchi, Serena; Liorni, Ilaria; Parazzini, Marta; Ravazzani, Paolo

    2015-04-01

    During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF) have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity quality assessment, in this study the exposure of high-resolution three-dimensional models of foetuses to the whole harmonic content of a uniform magnetic field with a fundamental frequency of 50 Hz, was assessed. The results show that the main contribution in terms of induced electric fields to the foetal exposure is given by the fundamental frequency component. The harmonic components add some contributions to the overall level of electric fields, however, due to the extremely low permitted amplitude of the harmonic components with respect to the fundamental, their amplitudes are low. The level of the induced electric field is also much lower than the limits suggested by the guidelines for general public exposure, when the amplitude of the incident magnetic field is set at the maximum permitted level. PMID:25837346

  2. Isotope separation by magnetic fields

    International Nuclear Information System (INIS)

    One of the isotopes of an element having several isotopes can be separated from the others in a dense, neutral plasma. Thus initially a neutral plasma is prepared including the element in question. This may consist of positive ions and negative electrons or alternatively of positive and negative ions, or else of a mixture of positive ions, negative ions and electrons. The plasma may then be injected into a magnetic field or may be generated in the field where more energy is imparted to a selected isotope than to the others. Finally, the isotopes are separated from each other on the basis of their differential energies. For example, the selected isotope may be given more energy than the others by stimulating it within the plasma at its resonant frequency which may be close to the cyclotron frequency, either by an electric field or by a magnetic field. In order to excite the other isotope, a different resonant frequency is required which depends on the plasma density, the relative concentration of electrons if the plasma contains electrons, the strength of the magnetic field, the ratio of charge to mass of the isotope, and possibly on the physical parameters of the plasma apparatus itself, such as the ratio of the length of the plasma column to its radius. The more energetic isotope may be separated by energy dependent chemical reactions, it may be collected by a positively biased probe or else the isotopes may be separated from each other by magnetic fields or in various other ways

  3. Solar Magnetic Fields

    Indian Academy of Sciences (India)

    J. O. Stenflo

    2008-03-01

    Since the structuring and variability of the Sun and other stars are governed by magnetic fields, much of present-day stellar physics centers around the measurement and understanding of the magnetic fields and their interactions. The Sun, being a prototypical star, plays a unique role in astrophysics, since its proximity allows the fundamental processes to be explored in detail. The PRL anniversary gives us an opportunity to look back at past milestones and try to identify the main unsolved issues that will be addressed in the future.

  4. Distributed generation induction and permanent magnet generators

    CERN Document Server

    Lai, L

    2007-01-01

    Distributed power generation is a technology that could help to enable efficient, renewable energy production both in the developed and developing world. It includes all use of small electric power generators, whether located on the utility system, at the site of a utility customer, or at an isolated site not connected to the power grid. Induction generators (IGs) are the cheapest and most commonly used technology, compatible with renewable energy resources. Permanent magnet (PM) generators have traditionally been avoided due to high fabrication costs; however, compared with IGs they are more reliable and productive. Distributed Generation thoroughly examines the principles, possibilities and limitations of creating energy with both IGs and PM generators. It takes an electrical engineering approach in the analysis and testing of these generators, and includes diagrams and extensive case study examples o better demonstrate how the integration of energy sources can be accomplished. The book also provides the ...

  5. N-flationary magnetic fields

    OpenAIRE

    Anber, Mohamed M.; Sorbo, Lorenzo

    2006-01-01

    There is increasing interest in the role played by pseudo Nambu-Goldstone bosons (pNGBs) in the construction of string-inspired models of inflation. In these models the inflaton is expected to be coupled to gauge fields, and will lead to the generation of magnetic fields that can be of cosmological interest. We study the production of such fields mainly focusing on the model of N-flation, where the collective effect of several pNGBs drives inflation. Because the produced fie...

  6. Dissipation of the sectored heliospheric magnetic field near the heliopause: a mechanism for the generation of anomalous cosmic rays

    OpenAIRE

    Drake, J. F.; Opher, M.; Swisdak, M.; Chamoun, J. N.

    2009-01-01

    The recent observations of the anomalous cosmic ray (ACR) energy spectrum as Voyagers 1 and 2 crossed the heliospheric termination shock have called into question the conventional shock source of these energetic particles. We suggest that the sectored heliospheric magnetic field, which results from the flapping of the heliospheric current sheet, piles up as it approaches the heliopause, narrowing the current sheets that separate the sectors and triggering the onset of collis...

  7. Surface magnetic field measurement with magnetic shielding.

    Czech Academy of Sciences Publication Activity Database

    Perevertov, Oleksiy

    2010-01-01

    Ro?. 61, ?. 7 (2010), 66-68. ISSN 1335-3632 Grant ostatní: AV?R(CZ) M100100906 Institutional research plan: CEZ:AV0Z10100520 Keywords : magnetic hysteresis * magnetic field measurement * magnetic shielding * extrapolation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.270, year: 2010

  8. High magnetic fields science and technology

    CERN Document Server

    Miura, Noboru

    2003-01-01

    This three-volume book provides a comprehensive review of experiments in very strong magnetic fields that can only be generated with very special magnets. The first volume is entirely devoted to the technology of laboratory magnets: permanent, superconducting, high-power water-cooled and hybrid; pulsed magnets, both nondestructive and destructive (megagauss fields). Volumes 2 and 3 contain reviews of the different areas of research where strong magnetic fields are an essential research tool. These volumes deal primarily with solid-state physics; other research areas covered are biological syst

  9. High field superconducting magnets

    Science.gov (United States)

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

    2011-01-01

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

  10. High magnetic field MRI system

    International Nuclear Information System (INIS)

    A high field superconducting magnet, 4-5 T in central magnetic field, is required for magnetic resonance spectroscopic imaging (MRSI) on 31P, essential nuclei for energy metabolism of human body. This paper reviews superconducting magnets for high field MRSI systems. Examples of the cross-sectional image and the spectrum of living animals are shown in the paper. (author)

  11. Parametric study of a variable-magnetic-field-based energy-selection system for generating a spread-out Bragg peak with a laser-accelerated proton beam

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dae-Hyun; Suh, Tae-Suk [The Catholic University of Korea, Seoul (Korea, Republic of); Kang, Young-Nam [Seoul St. Mary' s Hospital, The Catholic University of Korea, Seoul (Korea, Republic of); Yoo, Seung-Hoon [CHA Bundang Medical Center, CHA University, Seongnam (Korea, Republic of); Pae, Ki-Hong [Gwangju Institute of Science and Technology, Gwangju (Korea, Republic of); Shin, Dong-Ho; Lee, Se-Byeong [National Cancer Center, Goyang (Korea, Republic of)

    2013-01-15

    Laser-based proton beam acceleration, which produces broad energy spectra, is unsuitable for direct clinical use. Thus, employing an energy selection system is necessary. The purpose of the present study was to investigate a method whereby a variable magnetic field could be employed with an energy selection system to generate a spread-out Bragg peak (SOBP). For energy selection, particle transport and dosimetric property measurements, the Geant4 toolkit was implemented. The energy spectrum of the laser-accelerated proton beam was acquired using a particle-in-cell simulation. The hole size and the position of the energy selection collimator were varied in order to determine the effects of those parameters on the dosimetric properties. To generate an SOBP, we changed the magnetic field in the energy selection system for each beam weighting factor during beam irradiation. The overall results of this study suggest that the use of an energy selection system with a variable magnetic field can effectively generate an SOBP suitable for proton radiation therapy applications.

  12. Magnetic fields in the sun

    Science.gov (United States)

    Mullan, D. J.

    1974-01-01

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

  13. Programmable shunt valves: in vitro assessment of safety of the magnetic field generated by a portable game machine.

    Science.gov (United States)

    Nakashima, Koji; Nakajo, Takato; Kawamo, Michiari; Kato, Akihito; Ishigaki, Seiichiro; Murakami, Hidetomo; Imaizumi, Yohichi; Izumiyama, Hitoshi

    2011-01-01

    Cerebrospinal fluid (CSF) shunts are frequently used to treat hydrocephalus. The use of a programmable shunt valve allows physicians to easily change the opening pressure. Since patients with adjustable CSF shunt valves may use portable game machines, the permanent magnets in these machines may alter the shunt valve programmed settings or permanently damage the device. This study investigated the risk of unintentional valve adjustment associated with the use of game machines in patients with programmable CSF shunt valves. Four adjustable valves from 4 different manufacturers, Sophysa Polaris model SPV (Polaris valve), Miethke proGAV (proGAV), Codman Hakim programmable valve (CHPV), and Strata II small valve (Strata valve), were evaluated. Magnetic field interactions were determined using the portable game machine, Nintendo DS Lite (DS). The maximum distance between the valve and the DS that affected the valve pressure setting was measured by x-ray cinematography. The Polaris valve and proGAV were immune to unintentional reprogramming by the DS. However, the settings of the CHPV and Strata valves were randomly altered by the DS. Patients with an implanted shunt valve should be made aware of the risks posed by the magnetic fields associated with portable game machines and commonly used home electronics. PMID:21946726

  14. Sensor-less Field Oriented Control of Wind Turbine Driven Permanent Magnet Synchronous Generator Using Flux Linkage and Back EMF Estimation Methods

    OpenAIRE

    Porselvi Thayumanavan; Ranganath Muthu; Jeyasudha Sankararaman

    2014-01-01

    The study aims at the speed control of the wind turbine driven Permanent Magnet Synchronous Generator (PMSG) by sensor-less Field Oriented Control (FOC) method. Two methods of sensor-less FOC are proposed to control the speed and torque of the PMSG. The PMSG and the full-scale converter have an increasing market share in variable speed Wind Energy Conversion System (WECS). When compared to the Induction Generators (IGs), the PMSGs are smaller, easier to control and more efficient. In addition...

  15. Relaxed plasmas in external magnetic fields

    International Nuclear Information System (INIS)

    The extension of the theory of relaxed plasmas to external magnetic fields whose field lines intersect the wall is concisely formulated and then applied to the Extrap experiment [J. R. Drake, Plasma Phys. Controlled Fusion 26, 387 (1984)]. It is found that the external octupole field, though not affecting the phenomenon of current saturation, inhibits field reversal at parts of the wall if it is sufficiently strong to generate magnetic x points within the plasma

  16. Magnetic fields in the cosmos

    International Nuclear Information System (INIS)

    Although only a small part of available energy in the universe is invested in magnetic fields, they are responsible for most of the continual violent activity in the cosmos. There is a single, generic explanation for the ability of bodies as different as a dense, cold planet and a tenuous hot galactic disk to generate a magnetic field. The explanation, first worked out for the earth, comes from the discipline of magnetohydrodynamics. The cosmos is filled with fluids capable of carrying electric currents. The magnetic fields entrained in these fluids are stretched and folded by the fluid motion, gaining energy in the process. In other words, the turbulent fluids function as dynamos. However, the dynamo mechanism by itself cannot account for the exceptionally strong field of some stars. Because of such gaps in information, the rival hypothesis that there are primordial fields cannot be disproved. The balance of evidence, however, indicates that the planets, sun, most stars and the galaxy function as colossal dynamos. (SC)

  17. Radial magnetic field in magnetic confinement device

    Science.gov (United States)

    Xiong, Hao; Liu, Ming-Hai; Chen, Ming; Rao, Bo; Chen, Jie; Chen, Zhao-Quan; Xiao, Jin-Shui; Hu, Xi-Wei

    2015-09-01

    The intrinsic radial magnetic field (Br) in a tokamak is explored by the solution of the Grad-Shafranov equation in axisymmetric configurations through an expansion of the four terms of the magnetic surfaces. It can be inferred from the simulation results that at the core of the device, the tokamak should possess a three-dimensional magnetic field configuration, which could be reduced to a two-dimensional one when the radial position is greater than 0.6a. The radial magnetic field and the amzimuthal magnetic field have the same order of magnitude at the core of the device. These results can offer a reference for the analysis of the plasma instability, the property of the core plasma, and the magnetic field measurement. Project supported by the Special Domestic Program of ITER, China (Grant No. 2009GB105003).

  18. Magnetic Field Issues in Magnetic Resonance Imaging.

    Science.gov (United States)

    Petropoulos, Labros Spiridon

    Advances in Magnetic Resonance Imaging depend on the capability of the available hardware. Specifically, for the main magnet configuration, using derivative constraints, we can create a static magnetic field with reduced levels of inhomogeneity over a prescribed imaging volume. In the gradient coil, the entire design for the axial elliptical coil, and the mathematical foundation for the transverse elliptical coil have been presented. Also, the design of a self-shielded cylindrical gradient coil with a restricted length has been presented. In order to generate gradient coils adequate for head imaging without including the human shoulders in the design, asymmetric cylindrical coils in which the gradient center is shifted axially towards the end of a finite cylinder have been introduced and theoretical as well as experimental results have been presented. In order to eliminate eddy current effects in the design of the non-shielded asymmetric gradient coils, the self-shielded asymmetric cylindrical gradient coil geometry has been introduced. Continuing the development of novel geometries for the gradient coils, the complete set of self-shielded cylindrical gradient coils, which are designed such that the x component of the magnetic field varies linearly along the three traditional gradient axes, has been presented. In order to understand the behavior of the rf field inside a dielectric object, a mathematical model is briefly presented. Although specific methods can provide an indication of the rf behavior inside a loosely dielectric object, finite element methodology is the ultimate approach for modeling the human torso and generating an accurate picture for the shape of the rf field inside this dielectric object. For this purpose we have developed a 3D finite element model, using the Coulomb gauge condition as a constraint. Agreement with the heterogeneous multilayer planar model has been established, while agreement with theoretical results from the spherical model and experimental results from the cylindrical model at 170 M H z is very good and provides an encouraging sign for using this finite element approach for modeling the rf inside the human body. (Abstract shortened by UMI.).

  19. Coronal Magnetic Field Models

    Science.gov (United States)

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

    2015-07-01

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

  20. Magnetic Field Topology in Jets

    Science.gov (United States)

    Gardiner, T. A.; Frank, A.

    2000-01-01

    We present results on the magnetic field topology in a pulsed radiative. jet. For initially helical magnetic fields and periodic velocity variations, we find that the magnetic field alternates along the, length of the jet from toroidally dominated in the knots to possibly poloidally dominated in the intervening regions.

  1. Miniaturized Air-Driven Planar Magnetic Generators

    Directory of Open Access Journals (Sweden)

    Jingjing Zhao

    2015-10-01

    Full Text Available This paper presents the design, analysis, fabrication and testing of two miniaturized air-driven planar magnetic generators. In order to reduce the magnetic resistance torque, Generator 1 establishes a static magnetic field by consisting a multilayer planar coil as the stator and two multi-pole permanent-magnet (PM rotors on both sides of the coil. To further decrease the starting torque and save more space, Generator 2 adopts the multilayer planar coil as the rotor and the multi-pole PMs as the stator, eliminating the casing without compromising the magnetic structure or output performance. The prototypes were tested gathering energy from wind which can work at a low wind speed of 1~2 m/s. Prototype of Generator 1 is with a volume of 2.61 cm3 and its normalized voltage reaches 485 mV/krpm. Prototype of Generator 2 has a volume of 0.92 cm3 and a normalized voltage as high as 538 mV/krpm. Additionally, output voltage can be estimated at better than 96% accuracy by the theoretical model developed in this paper. The two micro generators are capable of producing substantial electricity with little volume to serve as compact power conversion devices.

  2. Magnetic field reversal and magnetic circuit in a thermally driven MHD dynamo

    International Nuclear Information System (INIS)

    Mechanism of magnetic field generation in a celestial body is investigated numerically. As a minimal model we study the dynamics of a Boussinesq MHD fluid confined between two rotating concentric spheres of uniform temperature. Five pairs of thermally driven convection columns are formed, which are robust against magnetic field generation. The activity of the magnetic field changes randomly in time. The global structure of the magnetic field outside the outer sphere is reversed rather periodically. It is also observed that closed bundles of strong magnetic field lines connecting two nearest anticyclonic convection columns are generated synchronously with the magnetic field reversal. (author)

  3. The Galactic Magnetic Field

    Science.gov (United States)

    Jansson, Ronnie; Farrar, Glennys R.

    2012-12-01

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

  4. THE GALACTIC MAGNETIC FIELD

    International Nuclear Information System (INIS)

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

  5. The Galactic Magnetic Field

    CERN Document Server

    Jansson, Ronnie

    2012-01-01

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

  6. THE GALACTIC MAGNETIC FIELD

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-12-10

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

  7. Five years of magnetic field management

    International Nuclear Information System (INIS)

    The extensive publicity of epidemiological studies inferring correlation between 60 Hz magnetic fields and childhood leukemia prompted world wide research programs that have as a goal to determine if low frequency magnetic fields represent any risk for the general population, children or utility workers. While supporting this research effort through EPRI, Con Edison embarked on a technical research program aimed to: characterize magnetic fields as to intensity and variation in time; and investigate practical means to manage these magnetic fields through currently known methods. The final goal of these research projects is to establish viable methods to reduce magnetic field intensity to desired values at reasonable distances from the sources. This goal was pursued step by step, starting with an inventory of the main sources of magnetic fields in substations, distribution and transmission facilities and generating plants. The characterization of the sources helped to identify typical cases and select specific cases, far practical applications. The next step was to analyze the specific cases and develop design criteria for managing the magnetic fields in new installations. These criteria included physical arrangement of equipment based oil calculation of magnetic fields, cancellation effect, desired maximum field intensity at specific points and shielding with high magnetic permeability metals (mu-metal and steel). This paper summarizes the authors' experiences and shows the results of the specific projects completed in recent years

  8. Highly-efficient source of collimated multi-MeV photons driven by radiation reaction of an electron beam in a self-generated magnetic field

    CERN Document Server

    Stark, D J; Arefiev, A V

    2015-01-01

    The rapid development of high brilliance X-ray radiation sources is revolutionizing physics, chemistry, and biology research through their novel applications. Another breakthrough is anticipated with the construction of next-generation laser facilities which will operate at intensities beyond $10^{23}$ $\\mathrm{W/cm^2}$, leading to higher yield, shorter wavelength radiation sources. We use numerical simulations to demonstrate that a source of collimated multi-MeV photons with conversion efficiency comparable to the one expected for these facilities is achievable at an order of magnitude lower in intensity, within reach of the existing facilities. In the optimal setup, the laser pulse irradiates a bulk solid-density target, heating the target electrons and inducing relativistic transparency. As the pulse then propagates, it generates a beam of energetic electrons which in turn drives a strong azimuthal magnetic field. This field significantly enhances the radiation reaction for the electrons, yielding tens of ...

  9. Optimization of superconductivity properties in MgB2 Wires and tapes to generate high magnetic fields

    International Nuclear Information System (INIS)

    We present, in this work, a study of the effects of doping, heat treatments and mechanisms of deformation, over the microstructure and superconducting properties of powder in tube (PIT) MgB2 wires and tapes.We observed that nano-SiC doping improves the critical current density (Jc) and the upper critical field (Hc2).The combined use of doping and Hot Isostatic Pressing (HIPing), produces samples with high density and improves Jc s.We studied the influence of number and temperature of intermediate heat treatments (TTI), during the fabrication of wires and tapes.We observed that TTI made at low temperature (oC), results in wires and tapes with better microstructure than those made at high temperature.Moreover, the increment of the heat treatments numbers at high temperature, decreases the quality of microstructure and Jc.In the study of sheaths materials, we observed that the Jc values measured by magnetization in Ti sheath samples are two order of magnitude larger than the values measured by transport, which indicates macroscopic fracture problems.On other hand, we fabricated tapes with excellent Jc values (104A/cm2 at 4K and 7T), which are similar to those of samples made with HIPing.This tape presents some degree of grains alignment, as a consequence of rolling.We observed Jc anisotropy in both transport and magnetization measurements in a range between 4 and 26K, and the same effect in Hc2.The anisotropy factor in Jc increase with applied field, while the anisotropy in Hc2 is constant with temperature (Hc2 parallel Hc2 perpendicular ?1.2).Finally, we observed that carbon nanotubes doping improves Hc2 and this effects is most important at temperatures below 5K.This increase in Hc2 was predicted by Gurevich [45], as an effect of modification in scattering coefficient between electronics bands of MgB2 by doping

  10. The National High Magnetic Field Laboratory

    Science.gov (United States)

    Jaime, M.; Lacerda, A.; Takano, Y.; Boebinger, G. S.

    2006-11-01

    The National High Magnetic Field Laboratory, established in 1990 with support from the National Science Foundation, the State of Florida, and the US Department of Energy, is a facility open to external users around the world. The experimental capabilities are distributed in three campuses. In Tallahassee, Florida, continuous magnetic fields are produced by means of superconducting and resistive magnets reaching fields of up to 33T (resistive), and 45T (hybrid). EMR, ICR, and a 900MHz wide bore NMR magnet are also available. The facility in Gainesville, Florida, is devoted to generating extremely low temperatures in the presence of external magnetic fields (15T, down to 0.4mK), and large MRI imaging capabilities. In Los Alamos, New Mexico, a 9 kV-capable capacitor bank and a number of different liquid Nitrogen-cooled resistive magnets produce repetitive pulses up to 75 T and now a single-shot pulsed up to 300T.

  11. Antimagnets: Controlling magnetic fields with superconductor-metamaterial hybrids

    OpenAIRE

    Sanchez, Alvaro; Navau, Carles; Prat, Jordi; Chen, Du-Xing

    2011-01-01

    Magnetism is very important in science and technology, from magnetic recording to energy generation to trapping cold atoms. Physicists have managed to master magnetism - to create and manipulate magnetic fields- almost at will. Surprisingly, there is at least one property which until now has been elusive: how to 'switch off' the magnetic interaction of a magnetic material with existing magnetic fields without modifying them. Here we introduce the antimagnet, a design to conc...

  12. Comparison of adjustable permanent magnetic field sources

    DEFF Research Database (Denmark)

    BjØrk, Rasmus; Bahl, Christian Robert Haffenden

    2010-01-01

    A permanent magnet assembly in which the flux density can be altered by a mechanical operation is often significantly smaller than comparable electromagnets and also requires no electrical power to operate. In this paper five permanent magnet designs in which the magnetic flux density can be altered are analyzed using numerical simulations, and compared based on the generated magnetic flux density in a sample volume and the amount of magnet material used. The designs are the concentric Halbach cylinder, the two half Halbach cylinders, the two linear Halbach arrays and the four and six rod mangle. The concentric Halbach cylinder design is found to be the best performing design, i.e. the design that provides the most magnetic flux density using the least amount of magnet material. A concentric Halbach cylinder has been constructed and the magnetic flux density, the homogeneity and the direction of the magnetic field are measured and compared with numerical simulation and a good agrement is found.

  13. Galactic Magnetic Fields as a consequence of Inflation

    OpenAIRE

    Dimopoulos, Konstantinos

    2001-01-01

    The generation of a magnetic field in the Early Universe is considered, due to the gravitational production of the Z-boson field during inflation. Scaled to the epoch of galaxy formation this magnetic field suffices to trigger the galactic dynamo and explain the observed galactic magnetic fields. The mechanism is independent of the inflationary model.

  14. The origin of large scale magnetic fields

    OpenAIRE

    K.Subramanian

    1996-01-01

    Magnetic fields correlated on several kiloparsec scales are seen in spiral galaxies. Their origin could be due to the winding up of a primordial cosmological field or due to amplification of a small seed field by a turbulent galactic dynamo. Both options have difficulties: There is no known battery mechanism for producing the required primordial field. Equally the turbulent dynamo may self destruct before being able to produce the large scale field, due to excess generation ...

  15. Manifestations of Magnetic Field Inhomogeneities

    Indian Academy of Sciences (India)

    Lawrence Rudnick

    2011-12-01

    Both observations and simulations reveal large inhomogeneities in magnetic field distributions in diffuse plasmas. Incorporating these inhomogeneities into various calculations can significantly change the inferred physical conditions. In extragalactic sources, e.g., these can compromise analyses of spectral ageing, which I will illustrate with some current work on cluster relics. I also briefly re-examine the old issue of how inhomogeneous fields affect particle lifetimes; perhaps not surprisingly, the next generation of radio telescopes are unlikely to find many sources that can extend their lifetimes from putting relativistic electrons into a low-field ‘freezer’. Finally, I preview some new EVLA results on the complex relic in Abell 2256, with implications for the interspersing of its relativistic and thermal plasmas.

  16. Observations of magnetic fields in hot stars

    OpenAIRE

    Petit, V.

    2010-01-01

    The presence of magnetic fields at the surfaces of many massive stars has been suspected for decades, to explain the observed properties and activity of OB stars. However, very few genuine high-mass stars had been identified as magnetic before the advent of a new generation of powerful spectropolarimeters that has resulted in a rapid burst of precise information about the magnetic properties of massive stars. During this talk, I will briefly review modern methods used to dia...

  17. Dynamically generated anomalous magnetic moment in massless QED

    International Nuclear Information System (INIS)

    In this paper we investigate the non-perturbative generation of an anomalous magnetic moment for massless fermions in the presence of an external magnetic field. In the context of massless QED in a magnetic field, we prove that the phenomenon of magnetic catalysis of chiral symmetry breaking, which has been associated in the literature with dynamical mass generation, is also responsible for the generation of a dynamical anomalous magnetic moment. As a consequence, the degenerate energy of electrons in Landau levels higher than zero exhibits Zeeman splitting. We explicitly report the splitting for the first Landau level and find the non-perturbative Lande g-factor and Bohr magneton. We anticipate that a dynamically generated anomalous magnetic moment will be a universal feature of theories with magnetic catalysis. Our findings can be important for condensed planar systems as graphene, as well as for highly magnetized dense systems as those forming the core of compact stars.

  18. The Heliospheric Magnetic Field

    Directory of Open Access Journals (Sweden)

    Mathew J. Owens

    2013-11-01

    Full Text Available The heliospheric magnetic field (HMF is the extension of the coronal magnetic field carried out into the solar system by the solar wind. It is the means by which the Sun interacts with planetary magnetospheres and channels charged particles propagating through the heliosphere. As the HMF remains rooted at the solar photosphere as the Sun rotates, the large-scale HMF traces out an Archimedean spiral. This pattern is distorted by the interaction of fast and slow solar wind streams, as well as the interplanetary manifestations of transient solar eruptions called coronal mass ejections. On the smaller scale, the HMF exhibits an array of waves, discontinuities, and turbulence, which give hints to the solar wind formation process. This review aims to summarise observations and theory of the small- and large-scale structure of the HMF. Solar-cycle and cycle-to-cycle evolution of the HMF is discussed in terms of recent spacecraft observations and pre-spaceage proxies for the HMF in geomagnetic and galactic cosmic ray records.

  19. Fast superconducting magnetic field switch

    Science.gov (United States)

    Goren, Y.; Mahale, N.K.

    1996-08-06

    The superconducting magnetic switch or fast kicker magnet is employed with electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater that the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. 6 figs.

  20. Helical magnetic fields via baryon asymmetry

    CERN Document Server

    Piratova, Eduard F; Hortúa, Héctor J

    2014-01-01

    There is strong observational evidence for the presence of large-scale magnetic fields MF in galaxies and clusters, with strength $\\sim \\mu$G and coherence lenght on the order of Kpc. However its origin remains as an outstanding problem. One of the possible explanations is that they have been generated in the early universe. Recently, it has been proposed that helical primordial magnetic fields PMFs, could be generated during the EW or QCD phase transitions, parity-violating processes and predicted by GUT or string theory. Here we concentrate on the study of two mechanisms to generate PMFs, the first one is the $\

  1. Magnetic monopole field exposed by electrons

    CERN Document Server

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

    2013-01-01

    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 ...

  2. High magnetic field ohmically decoupled non-contact technology

    Science.gov (United States)

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

    2009-05-19

    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.

  3. Relaxed plasmas in external magnetic fields

    International Nuclear Information System (INIS)

    The well-known theory of relaxed plasmas (Taylor states) is extended to external magnetic fields whose field lines intersect the conducting toroidal boundary. Application to an axially symmetric, large-aspect-ratio torus with circular cross section shows that the maximum pinch ratio, and hence the phenomenon of current saturation, is independent of the external field. The relaxed state is explicitly given for an external octupole field. In this case, field reversal is inhibited near parts of the boundary if the octupole generates magnetic x-points within the plasma. (orig.)

  4. Anomalous Global Strings and Primordial Magnetic Fields

    OpenAIRE

    Brandenberger, Robert H.; Zhang, Xinmin

    1998-01-01

    We propose a new mechanism for the generation of primordial magnetic fields, making use of the magnetic fields which are induced by anomalous global strings which couple to electromagnetism via Wess-Zumino type interactions. This mechanism can be realized in QCD by utilizing pion strings, global vortices which appear in the linear sigma model which describes physics below the QCD confinement scale. During the chiral symmetry breaking phase transition, pion strings can be pro...

  5. Magnetic fields in massive stars

    OpenAIRE

    Hubrig, S.

    2007-01-01

    Although indirect evidence for the presence of magnetic fields in high-mass stars is regularly reported in the literature, the detection of these fields remains an extremely challenging observational problem. We review the recent discoveries of magnetic fields in different types of massive stars and briefly discuss strategies for spectropolarimetric observations to be carried out in the future.

  6. Improved efficiency of heat generation in magnetic nanoparticle hyperthermia

    OpenAIRE

    Racz, J.; Chatel, P.F. de; Szabo, I. A.; Szunyogh, L.; Nandori, I.

    2015-01-01

    The deterministic Landau-Lifshitz-Gilbert equation has been used to investigate the nonlinear dynamics of magnetization and the specific loss power in magnetic nanoparticles with uniaxial anisotropy driven by a rotating magnetic field. We show that a more efficient heat generation by magnetic nanoparticles is possible if the direction of the rotating external field changes periodically and we suggest its possible experimental realization in cancer therapy which requires the ...

  7. Evolution of primordial magnetic fields in mean-field approximation

    OpenAIRE

    Campanelli, LeonardoDipartimento di Fisica, Università di Bari, 70126, Bari, Italy

    2014-01-01

    We study the evolution of phase-transition-generated cosmic magnetic fields coupled to the primeval cosmic plasma in the turbulent and viscous free-streaming regimes. The evolution laws for the magnetic energy density and the correlation length, both in the helical and the non-helical cases, are found by solving the autoinduction and Navier–Stokes equations in the mean-field approximation. Analytical results are derived in Minkowski spacetime and then extended to the case of a Friedmann unive...

  8. Magnetic-field-controlled reconfigurable semiconductor logic.

    Science.gov (United States)

    Joo, Sungjung; Kim, Taeyueb; Shin, Sang Hoon; Lim, Ju Young; Hong, Jinki; Song, Jin Dong; Chang, Joonyeon; Lee, Hyun-Woo; Rhie, Kungwon; Han, Suk Hee; Shin, Kyung-Ho; Johnson, Mark

    2013-02-01

    Logic devices based on magnetism show promise for increasing computational efficiency while decreasing consumed power. They offer zero quiescent power and yet combine novel functions such as programmable logic operation and non-volatile built-in memory. However, practical efforts to adapt a magnetic device to logic suffer from a low signal-to-noise ratio and other performance attributes that are not adequate for logic gates. Rather than exploiting magnetoresistive effects that result from spin-dependent transport of carriers, we have approached the development of a magnetic logic device in a different way: we use the phenomenon of large magnetoresistance found in non-magnetic semiconductors in high electric fields. Here we report a device showing a strong diode characteristic that is highly sensitive to both the sign and the magnitude of an external magnetic field, offering a reversible change between two different characteristic states by the application of a magnetic field. This feature results from magnetic control of carrier generation and recombination in an InSb p-n bilayer channel. Simple circuits combining such elementary devices are fabricated and tested, and Boolean logic functions including AND, OR, NAND and NOR are performed. They are programmed dynamically by external electric or magnetic signals, demonstrating magnetic-field-controlled semiconductor reconfigurable logic at room temperature. This magnetic technology permits a new kind of spintronic device, characterized as a current switch rather than a voltage switch, and provides a simple and compact platform for non-volatile reconfigurable logic devices. PMID:23364687

  9. PERMANENT-MAGNET INDUCTION GENERATORS: AN OVERVIEW

    OpenAIRE

    K. S. S. RAMAKRISHNAN; PAWAN SHARMA; Bhatti, T. S.

    2011-01-01

    The advantage of using a permanent-magnet induction generator (PMIG) instead of a conventional induction generator is its ability to suppress inrush current during system linking when synchronous input is performed. Induction machines excited with permanent-magnet (PM) are called permanent-magnet induction generators. This paper presents an exhaustive survey of the literature discussing the classification of permanent-magnet machines, process of permanent-magnet excitation and voltage build-u...

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

    CERN Document Server

    Adorno, T C; Shabad, A E

    2014-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

    Adorno, T.C. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); University of Florida, Department of Physics, Gainesville, FL (United States); Gitman, D.M. [Universidade de Sao Paulo, Instituto de Fisica, Caixa Postal 66318, Sao Paulo, SP (Brazil); Tomsk State University, Department of Physics, Tomsk (Russian Federation); Shabad, A.E. [P. N. Lebedev Physics Institute, Moscow (Russian Federation)

    2014-04-15

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

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

    International Nuclear Information System (INIS)

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

  13. Optimization of Cryogenic and Superconducting Magnetic Systems for MHD Generators

    International Nuclear Information System (INIS)

    Increasing the strength of the magnetic field within the working volume of an MHD generator results in a considerable increase in the power density and consequently a reduction in the weight of the generator and in the unit power cost. Strong magnetic fields can be obtained by means of iron-free magnetic systems in which either super pure metals or superconducting alloys cooled by liquid gases are used in the windings. The best windings cross-section for producing a uniform magnetic field in the rectangular working region is chosen. With an iron-free magnetic system incorporating windings of such configuration the weight can be reduced to a minimum. The authors present the calculations for producing uniform magnetic fields of high intensity in the working volume of the MHD duct by means of iron-free magnetic systems. The properties of these systems are compared in the paper. (author)

  14. Space applications of superconductivity - High field magnets

    Science.gov (United States)

    Fickett, F. R.

    1979-01-01

    The paper discusses developments in superconducting magnets and their applications in space technology. Superconducting magnets are characterized by high fields (to 15T and higher) and high current densities combined with low mass and small size. The superconducting materials and coil design are being improved and new high-strength composites are being used for magnet structural components. Such problems as maintaining low cooling temperatures (near 4 K) for long periods of time and degradation of existing high-field superconductors at low strain levels can be remedied by research and engineering. Some of the proposed space applications of superconducting magnets include: cosmic ray analysis with magnetic spectrometers, energy storage and conversion, energy generation by magnetohydrodynamic and thermonuclear fusion techniques, and propulsion. Several operational superconducting magnet systems are detailed.

  15. Cosmic Magnetic Fields - An Overview

    Science.gov (United States)

    Wielebinski, Richard; Beck, Rainer

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

  16. Primordial magnetic fields from preheating at the electroweak scale

    OpenAIRE

    Díaz-Gil, Alejandrondrés; García-Bellido, Juan; García Pérez, Margarita; González-Arroyo, Antonio

    2008-01-01

    We analyze the generation of helical magnetic fields during preheating in a model of low-scale electroweak (EW) hybrid inflation. We show how the inhomogeneities in the Higgs field, resulting from tachyonic preheating after inflation, seed the magnetic fields in a way analogous to that predicted by Vachaspati and Cornwall in the context of the EW symmetry breaking. At this stage, the helical nature of the generated magnetic fields is linked to the non-trivial winding of the ...

  17. Review: Magnetic fields of O stars

    CERN Document Server

    Wade, G A

    2014-01-01

    Since 2002, strong, organized magnetic fields have been firmly detected at the surfaces of about 10 Galactic O-type stars. In this paper I will review the characteristics of the inferred fields of individual stars, as well as the overall population. I will discuss the extension of the 'magnetic desert', first inferred among the A-type stars, to O stars up to 60 solar masses. I will discuss the interaction of the winds of the magnetic stars with the fields above their surfaces, generating complex 'dynamical magnetosphere' structures detected in optical and UV lines, and in X-ray lines and continuum. Finally, I will discuss the detection of a small number of variable O stars in the LMC and SMC that exhibit spectral characteristics analogous to the known Galactic magnetic stars, and that almost certainly represent the first known examples of extra-Galactic magnetic stars.

  18. Non-spot magnetic fields

    International Nuclear Information System (INIS)

    The Glossary is designed to be a technical dictionary that will provide solar workers of various specialties, students, other astronomers and theoreticians with concise information on the nature and the properties of phenomena of solar and solar-terrestrial physics. Each term, or group of related terms, is given a concise phenomenological and quantitative description, including the relationship to other phenomena and an interpretation in terms of physical processes. The references are intended to lead the non-specialist reader into the literature. This section deals with: general, polar and large-scale magnetic fields; sector structure; unipolar magnetic region; magnetic puka; network field; magnetic hills; magnetic element or fluxule; magnetic rope; magnetic filament; magnetic microturbulence; crossover effect; magnetograph; Stokesmeter; and lambdameter or recording Doppler comparator. (B.R.H.)

  19. Magnetic Fields Induced in the Solid Earth and Oceans

    DEFF Research Database (Denmark)

    Kuvshinov, Alexei; Olsen, Nils

    2005-01-01

    Electromagnetic induction in the Earth's interior is an important contributor to the near-Earth magnetic field. Oceans play a special role in the induction, due to their relatively high conductance of large lateral variability. Electric currents that generate secondary magnetic fields are induced in the oceans by two different sources: by time varying external magnetic fields, and by motion of the conducting ocean water through the Earth's main magnetic field. Significant progress in the accurat...

  20. Biermann Mechanism in Primordial Supernova Remnant and Seed Magnetic Fields

    OpenAIRE

    Hanayama, Hidekazu; Takahashi, Keitaro; Kotake, Kei; Oguri, Masamune; Ichiki, Kiyotomo; Ohno, Hiroshi

    2005-01-01

    We study generation of magnetic fields by the Biermann mechanism in the pair-instability supernovae explosions of first stars. The Biermann mechanism produces magnetic fields in the shocked region between the bubble and interstellar medium (ISM), even if magnetic fields are absent initially. We perform a series of two-dimensional magnetohydrodynamic simulations with the Biermann term and estimate the amplitude and total energy of the produced magnetic fields. We find that ma...

  1. Wuhan pulsed high magnetic field center

    OpenAIRE

    Liang LI; PENG, TAO; Ding, Honfa; Han, Xiaotao; Ding, Tonghai; Chen, Jin; Wang, Junfeng; Xie, Jianfeng; Wang, Shaoliang; Duan, Xianzhong; Wang, Cheng; Herlach, Fritz; Vanacken, Johan; Pan, Yuan

    2008-01-01

    Wuhan pulsed high magnetic field facility is under development. Magnets of bore sizes from 12 to 34 mm with the peak field in the range of 50 to 80 T have been designed. The pulsed power supplies consists of a 12 MJ, 25 kV capacitor bank and a 100 MVA/100 MJ flywheel pulse generator. A prototype 1 MJ, 25 kV capacitor bank is under construction. Five magnets wound with CuNb wire and copper wire reinforced internally with Zylon fiber composites and externally with stainless steel shells have be...

  2. Characteristics of magnetic field induction inside a module of a magnetic separator ?????????????? ???????? ???? ? ?????? ?????????? ??????????

    Directory of Open Access Journals (Sweden)

    Sandulyak Anna Aleksandrovna

    2013-05-01

    Full Text Available Characteristics of magnetic separators are analyzed in the article. Magnetic separators are used to treat various construction materials. Unfortunately, the nature of the magnetic field, generated in their operating zone, is generally not taken into account by their designers. Academic publications fail to provide any detailed basic characteristics of the field induction emitted by magnetic separators in the course of their operation.Magnetic systems of any magnetic separator have a modular structure; they consist of several modules. Single and opposite magnetic elements are usually integrated into one module within a system having permanent magnets. If opposite magnetic elements are used, magnetic field intensity inside the module increases.In this study, characteristics of magnetic induction for single magnetic elements inside various modules of magnetic separators were assessed in a laboratory experiment. Similar characteristics of magnetic induction for single and twin (opposite magnetic elements were compared. In the module consisting of two opposed magnetic elements, the magnetic field becomes stronger compared to the field of a single magnetic element. Magnetic induction in the module recedes as the distance between magnetic elements increases, because of the isolation of the field generated by the opposed magnetic elements.The authors have proven the feasibility and expediency of employment of the superposition principle used to obtain the resulting characteristics. It may be employed to substitute modeling by calculations.???????????????? ???????? ?????????????? ???????? ?????????? ???? ??? ????????? ????????? ? ????????? ??????? ????????? ???????????. ???????????? ?????????????? ???????? ?????????? ???? ??? ????????? ? ????????? ????????? ????????? ??????. ? ??????, ????????? ? ???? ?????????????? ????????? ?????????, ???? ??????????? ?? ????????? ? ????? ?????????? ?????????? ????????, ???? ?? ???? ?????????? ???????????? ?????????? ??????? ???????? ? ?????? ????????? ?? ???? ??? ???????? «??????????» ????????? ?????, ??????????? ??????????????? ?????????? ??????????.???????? ??????????? ? ???????????? ???????????????? ????????????? ???????? ???????????? ??? ???????????? ?????????????? ?????????????? ???????? ???? ????? ??????????????? ?????????? ?????????? ??? ?????? ????????? ????????????? ?????????.

  3. NMR in pulsed magnetic field

    KAUST Repository

    Abou-Hamad, Edy

    2011-09-01

    Nuclear magnetic resonance (NMR) experiments in pulsed magnetic fields up to 30.4 T focused on 1H and 93Nb nuclei are reported. Here we discuss the advantage and limitation of pulsed field NMR and why this technique is able to become a promising research tool. © 2011 Elsevier Inc. All Rights Reserved.

  4. Magnetic fields in O stars

    OpenAIRE

    Nazé, Yaël

    2013-01-01

    Over the last decade, large-scale, organized (generally dipolar) magnetic fields with a strength between 0.1 and 20 kG were detected in dozens of OB stars. This contribution reviews the impact of such magnetic fields on the stellar winds of O-stars, with emphasis on variability and X-ray emission.

  5. Magnetic Field Amplification via Protostellar Disc Dynamos

    CERN Document Server

    Dyda, Sergei; Ustyugova, Galina V; Koldoba, Alexander V; Wasserman, Ira

    2015-01-01

    We model the generation of a magnetic field in a protostellar disc using an \\alpha-dynamo and perform axisymmetric magnetohydrodynamics (MHD) simulations of a T Tauri star. We find that for small values of the dimensionless dynamo parameter $\\alpha_d$ the poloidal field grows exponentially at a rate ${\\sigma} \\propto {\\Omega}_K \\sqrt{\\alpha_d}$ , before saturating to a value $\\propto \\sqrt{\\alpha_d}$ . The dynamo excites dipole and octupole modes, but quadrupole modes are suppressed, because of the symmetries of the seed field. Initial seed fields too weak to launch MHD outflows are found to grow sufficiently to launch winds with observationally relevant mass fluxes of order $10^{-9} M_{\\odot}/\\rm{yr}$ for T Tauri stars. For large values of $\\alpha_d$ magnetic loops are generated over the entire disc. These quickly come to dominate the disc dynamics and cause the disc to break up due to the magnetic pressure.

  6. Magnetic fields in nearby galaxies

    OpenAIRE

    Fletcher, Andrew

    2011-01-01

    Observations of synchrotron radiation and the Faraday rotation of its polarized component allow us to investigate the magnetic properties of the diffuse interstellar medium in nearby galaxies, on scales down to roughly one hundred parsecs. All disc galaxies seem to have a mean, or regular, magnetic field component that is ordered on length scales comparable to the size of the galaxy as well as a random magnetic field of comparable or greater strength. I present an overview o...

  7. The MAVEN Magnetic Field Investigation

    Science.gov (United States)

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

    2015-06-01

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

  8. Discontinuities in the Magnetic Field near Enceladus

    Science.gov (United States)

    Simon, S.; Saur, J.; van Treeck, S.; Kriegel, H.; Dougherty, M. K.

    2014-12-01

    The plasma interaction of Saturn's icy moon Enceladus generates a hemisphere coupling current system that directly connects the giant planet's northern and southern polar magnetosphere. Based on Cassini magnetometer observations from all 20 targeted Enceladus flybys between 2004 and 2014, we study the magnetic field discontinuities associated with these hemisphere coupling currents. We identify a total number of 11 events during which the magnetic field was discontinuous at the surface of the Enceladus fluxtube (defined by the bundle of magnetic field lines tangential to the solid body of the moon). A Minimum Variance Analysis is applied to calculate the surface normals of these discontinuities. In agreement with theoretical expectations, the normals are found to be perpendicular to the surface of the Enceladus fluxtube. The variation of the hemisphere coupling currents with Enceladean longitude leaves a clear imprint in the strengths of the observed magnetic field jumps as well.

  9. Conformal anomaly and primordial magnetic fields

    CERN Document Server

    Agullo, Ivan

    2013-01-01

    The conformal symmetry of the quantized electromagnetic field breaks down in curved space-time. We point out that this conformal anomaly is able to generate a sizable magnetic field during a phase of slow-roll inflation. Such primordial magnetism is characterized by the expectation value of the squared of the magnetic field for comoving observers, which at leading order in slow-roll takes the value $\\ =\\frac{8}{15(4\\pi)^2}\\, H^4\\epsilon$, where $\\epsilon$ is the standard slow-roll parameter. This result is insensitive to the intrinsic ambiguities of renormalization in curved space-times. The information in the quantum state gets diluted during inflation and does not affect the prediction. A primordial field of this strength is able to seed the observed cosmic magnetism.

  10. On a Babcock-Leighton Solar Dynamo Model with a Deep-seated Generating Layer for the Toroidal Magnetic Field. IV.

    Science.gov (United States)

    Durney, Bernard R.

    1997-09-01

    The study is continued of a dynamo model of the Babcock-Leighton type (i.e., the surface eruptions of toroidal magnetic field are the source for the poloidal field) with a thin, deep seated layer (GL), for the generation of the toroidal field, B?. The partial differential equations satisfied by B? and by the vector potential for the poloidal field are integrated in time with the help of a second order time- and space-centered finite different scheme. Axial symmetry is assumed; the gradient of the angular velocity in the GL is such that within this layer a transition to uniform rotation takes place; the meridional motion, transporting the poloidal field to the GL, is poleward and about 3 m s-1 at the surface; the radial diffusivity ?r equals 5 × 109 cm2 s-1, and the horizontal diffusivity ?? is adjusted to achieve marginal stability. The initial conditions are: a negligible poloidal field, and a maximum value of |B?| in the GL equal to 1.5 × Bcr, where Bcr is a prescribed field. For every time step the maximum value of |B?| in the GL is computed. If this value exceeds Bcr, then there is eruption of a flux tube (at the latitude corresponding to this maximum) that rises radially to the surface. Only one eruption is allowed per time step (?t) and B? in the GL is unchanged as a consequence of the eruption. The ensemble of eruptions is the source for the poloidal field, i.e., no use is made of a mean field equation relating the poloidal with the toroidal field. For a given value of ?t, and since the problem is linear, the solutions scale with Bcr. Therefore, the equations need to be solved for one value of Bcr only. Since only one eruption is allowed per time step, the dependence of the solutions on ?t needs to be studied. Let Ft be an arbitrary numerical factor (= 3 for example) and compare the solutions of the equations for (Bcr, ?t) and (Bcr, ?t/3). It is clear that there will be 3 times as many eruptions in the second case (with the shorter time step) than in the first case. However, if the erupted flux in case one is multiplied by 3, then the solutions for this case become nearly identical to those of case two (?t is shorter than any typical time of the system, and the difference due to the unequal time steps is negligible). Therefore, varying the time step is equivalent to keeping ?t fixed while multiplying the erupted flux by an appropriate factor. In the numerical calculations ?t was set equal to 105 s. The factor Ft can then be interpreted as the number of eruptions per 105 s. The integration of the equations shows that there is a transition in the nature of the solutions for Ft ~ 2.5. For Ft 2.5, the eruptions occur for ? greater than ~ ?/4, where ? is the polar angle. Furthermore, for Ft 2.5. The factor Ft is an arbitrary parameter in the model and an appeal to observations is necessary. We set Bcr = 103 G. In the model, the magnetic flux of erupting magnetic tubes, is then about 3 × 1021 G, of the order of the solar values. For this value of Bcr and for the value of Ft (~2.5) at which the transition takes place, the total erupted flux in 10 years is about 0.85 × 1025 Mx in remarkable agreement with the total erupted flux during a solar cycle. Concerning the dynamo models studied here, a major drawback encountered in previous papers has been the eruptions at high latitudes, which entail unrealistically large values for the radial magnetic field at the poles. The results of this paper provide a major step forward in the resolution of this difficulty.

  11. Fully relativistic self-consistent field under a magnetic field.

    Science.gov (United States)

    Reynolds, Ryan D; Shiozaki, Toru

    2015-06-14

    We present a gauge-invariant implementation of the four-component Dirac-Hartree-Fock method for simulating the electronic structure of heavy element complexes in magnetic fields. The additional cost associated with the magnetic field is shown to be only 10-13% of that at zero field. The Dirac-Hartree-Fock wave function is constructed from gauge-including atomic orbitals. The so-called restricted magnetic balance is used to generate 2-spinor basis functions for the small component. The molecular integrals for the Coulomb and Gaunt interactions are computed using density fitting. Our efficient, parallel implementation allows for simulating the electronic structure of molecules containing more than 100 atoms with a few heavy elements under magnetic fields. PMID:25310527

  12. Antimagnets: controlling magnetic fields with superconductor-metamaterial hybrids

    International Nuclear Information System (INIS)

    Magnetism is very important in various areas of science and technology, ranging from magnetic recording through energy generation to trapping cold atoms. Physicists have managed to master magnetism-to create and manipulate magnetic fields-almost at will. Surprisingly, there is at least one property that has been elusive until now: how to 'switch off' the magnetic interaction of a magnetic material with existing magnetic fields without modifying them. Here we introduce the antimagnet, a design that conceals the magnetic response of a given volume from its exterior, without altering the external magnetic fields, in some respects analogous to recent theoretical proposals for cloaking electromagnetic waves with metamaterials. However, unlike these devices, which require extreme material properties, our device is feasible and needs only two kinds of available materials: superconductors and isotropic magnetic materials. Antimagnets may have applications in magnetic-based medical techniques such as magnetic resonance imaging or in reducing the magnetic signature of vessels or planes.

  13. Antimagnets: controlling magnetic fields with superconductor-metamaterial hybrids

    Science.gov (United States)

    Sanchez, Alvaro; Navau, Carles; Prat-Camps, Jordi; Chen, Du-Xing

    2011-09-01

    Magnetism is very important in various areas of science and technology, ranging from magnetic recording through energy generation to trapping cold atoms. Physicists have managed to master magnetism—to create and manipulate magnetic fields—almost at will. Surprisingly, there is at least one property that has been elusive until now: how to ‘switch off’ the magnetic interaction of a magnetic material with existing magnetic fields without modifying them. Here we introduce the antimagnet, a design that conceals the magnetic response of a given volume from its exterior, without altering the external magnetic fields, in some respects analogous to recent theoretical proposals for cloaking electromagnetic waves with metamaterials. However, unlike these devices, which require extreme material properties, our device is feasible and needs only two kinds of available materials: superconductors and isotropic magnetic materials. Antimagnets may have applications in magnetic-based medical techniques such as magnetic resonance imaging or in reducing the magnetic signature of vessels or planes.

  14. New circumstellar magnetic field diagnostics

    OpenAIRE

    Nordsieck, K. H.

    2001-01-01

    In this paper I will discuss new magnetic field diagnostics and instrumentation for an area of astrophysics where magnetic field observations have been difficult - circumstellar material. Such diagnostics would be particularly relevant to star formation and evolution. Stellar photosphere diagnostics include the Zeeman effect and atomic scattering diagnostics like the Hanle Effect and atomic alignment. The Zeeman Effect is in general not sensitive enough for the field strengt...

  15. Venus magnetic field and magnetosphere

    International Nuclear Information System (INIS)

    Magnetic field investigations have been conducted in the distance of 1500-3000 km and 1-6Rsub(?) from the Venus, where Rsub(?) - is the Venus radius. Magnetic field complex topology, observed at the Venus night side form ''Venera-9,10'' satellites is explained by the Venus having its own weak magnetic field and the action of outer source fields. There is a magnetic stub on the planet night side, in which 2 bunches of lines of force, devided by neutral layer, are directed from the planet (to the north of equator) and to the planet (to the south of equator). The magnetic stub narrows at approaching to the planet and is located inside the planet geometric shade near the planet. The planet magnetic field effects but slightly the character of the planet flow-around by the sun wind. The stub topology depends on the polarity mark and force of field in the planet transfer zone. The ''overuniting'' processes of magnetospheric field and fields of outer sources present permanent process in the Venus magnetosphere. Notwithstanding the weakness of the Venus field, it is similar to geomagnetic one in a model way, provided the planet rotation peculiarities are taken into account

  16. Magnetic field near the center on the baby cyclotron

    International Nuclear Information System (INIS)

    With the AVF cyclotron, the relative distribution of magnetic field changes when the magnitude of the field varies for a wide range. This change is large in the central region. The change of the relative magnetic field, however, may be suppressed in magnitude by employing a physical configuration that alleviates local saturations of iron at the magnetic pole surfaces. This paper covers a recently generated magnetic field featuring the relative field distribution in the central region of a type 3015 baby cyclotron that has successfully been held more or less steady from a 1.5 Tsl below 1.0 Tsl in average magnetic field. (author)

  17. Magnetic Field Amplification in Young Galaxies

    CERN Document Server

    Schober, Jennifer; Klessen, Ralf S

    2013-01-01

    The Universe at present is highly magnetized, with fields of the order of a few 10^-5 G and coherence lengths larger than 10 kpc in typical galaxies like the Milky Way. We propose that the magnetic field was amplified to this values already during the formation and the early evolution of the galaxies. Turbulence in young galaxies is driven by accretion as well as by supernova (SN) explosions of the first generation of stars. The small-scale dynamo can convert the turbulent kinetic energy into magnetic energy and amplify very weak primordial magnetic seed fields on short timescales. The amplification takes place in two phases: in the kinematic phase the magnetic field grows exponentially, with the largest growth on the smallest non-resistive scale. In the following non-linear phase the magnetic energy is shifted towards larger scales until the dynamo saturates on the turbulent forcing scale. To describe the amplification of the magnetic field quantitatively we model the microphysics in the interstellar medium ...

  18. Solenoid magnet with homogeneous magnet field

    International Nuclear Information System (INIS)

    This is preferably used in NMR imaging. It includes several attached coils, preferably Bitter coils, and some parameters such as coil length, coil spire thickness and outer diameter are chosen to get the field homogeneity and to optimize the product power-mass of the magnet

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

    CERN Document Server

    Subramanian, Kandaswamy

    2015-01-01

    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, ...

  20. Hyperthermia generated with ferucarbotran (Resovist®) in an alternating magnetic field enhances cisplatin-induced apoptosis of cultured human oral cancer cells.

    Science.gov (United States)

    Sato, Itaru; Umemura, Masanari; Mitsudo, Kenji; Kioi, Mitomu; Nakashima, Hideyuki; Iwai, Toshinori; Feng, Xianfeng; Oda, Kayoko; Miyajima, Akiyoshi; Makino, Ayako; Iwai, Maki; Fujita, Takayuki; Yokoyama, Utako; Okumura, Satoshi; Sato, Motohiko; Eguchi, Haruki; Tohnai, Iwai; Ishikawa, Yoshihiro

    2014-05-01

    Hyperthermia is a promising anti-cancer treatment in which the tissue temperature is increased to 42-45 °C, and which is often used in combination with chemotherapy or radiation therapy. Our aim in the present work was to examine the feasibility of combination therapy for oral cancer with cisplatin and hyperthermia generated with ferucarbotran (Resovist(®); superparamagnetic iron oxide) in an alternating magnetic field (AMF). First, we established that administration of ferucarbotran at the approved dosage for magnetic resonance imaging provides an iron concentration sufficient to increase the temperature to 42.5 °C upon exposure to AMF. Then, we examined the effect of cisplatin combined with ferucarbotran/AMF-induced hyperthermia on cultured human oral cancer cells (HSC-3 and OSC-19). Cisplatin alone induced apoptosis of cancer cells in a dose-dependent manner, as is well known. However, the combination of cisplatin with ferucarbotran/AMF was significantly more effective than cisplatin alone. This result suggests that it might be possible to reduce the clinically effective dosage of cisplatin by administering it in combination with ferucarbotran/AMF-induced hyperthermia, thereby potentially reducing the incidence of serious cisplatin-related side effects. Further work seems justified to evaluate simultaneous thermo-chemotherapy as a new approach to anticancer therapy. PMID:24619404

  1. Assessment of Foetal Exposure to the Homogeneous Magnetic Field Harmonic Spectrum Generated by Electricity Transmission and Distribution Networks

    OpenAIRE

    Fiocchi, Serena; Liorni, Ilaria; Parazzini, Marta; Ravazzani, Paolo

    2015-01-01

    During the last decades studies addressing the effects of exposure to Extremely Low Frequency Electromagnetic Fields (ELF-EMF) have pointed out a possible link between those fields emitted by power lines and childhood leukaemia. They have also stressed the importance of also including in the assessment the contribution of frequency components, namely harmonics, other than the fundamental one. Based on the spectrum of supply voltage networks allowed by the European standard for electricity qua...

  2. LOCAL MAGNETIC FIELD DATA PROCESSING

    Directory of Open Access Journals (Sweden)

    Ivan Ostroumov

    2015-04-01

    Full Text Available The article represents the methodology for estimation of the Earth’s magnetic field characteristics for a particular area. It is proposed to use a group of sensors inside of a tablet or a cell phone as a measurement device. We used typical sensors raw data like pitch, roll, yaw (from gyros; components of magnetic field intensity vectors (from magnetometers; latitude, longitude, altitude (from global positioning sensor. We represent the result of intensity vector components estimation for particular area. It is stated that the most important characteristics of magnetic fieldare horizontal and vertical components of intensity vector and inclination and declination angles. In addition, we compared the received results with magnetic field forecast, according to the world magnetic model.

  3. Neutron scattering in magnetic fields

    International Nuclear Information System (INIS)

    The use of magnetic fields in neutron scattering experimentation is reviewed briefly. Two general areas of application can be distinguished. In one the field acts to change the properties of the scattering sample; in the second the field acts on the neutron itself. Several examples are discussed. Precautions necessary for high precision polarized beam measurements are reviewed. 33 references

  4. Magnetic fields in neutron stars

    OpenAIRE

    Vigano?, Daniele

    2013-01-01

    This work aims at studying how magnetic fields affect the observational properties and the long-term evolution of isolated neutron stars, which are the strongest magnets in the universe. The extreme physical conditions met inside these astronomical sources complicate their theoretical study, but, thanks to the increasing wealth of radio and X-ray data, great advances have been made over the last years. A neutron star is surrounded by magnetized plasma, the so-called magnetos...

  5. ISR split-field magnet

    CERN Multimedia

    1974-01-01

    The Split-Field-Magnet at the ISR with arrays of multiwire proportional chambers installed in its large aperture. The detection system is now in full action for experiments and the first results have been reported.

  6. ISR split-field magnet

    CERN Multimedia

    1975-01-01

    The experimental apparatus used at intersection 4 around the Split-Field Magnet by the CERN-Bologna Collaboration (experiment R406). The plastic scintillator telescopes are used for precise pulse-height and time-of-flight measurements.

  7. Transport in ergodic magnetic fields

    International Nuclear Information System (INIS)

    Solution of a 3D problem based on a numerical treatment of macroscopic fluid equations is shown to be necessary to describe a stochastic scrape-off layer in the framework of the theory of transport in an ergodic magnetic field. The transport of a stochastic magnetic field within the bulk plasma is also considered. Here the drift kinetic equation is solved with the ansatz for the distribution function to deviate only a little from the Maxwellian. A local fluctuating stochastic magnetic field and electric field are considered and transport is found by averaging over the unperturbed magnetic surfaces. Due to collisions the diffusion coefficient is much larger than given by the Rosenbluth, Rechester formula

  8. Comparison of alignment tensors generated for native tRNAVal using magnetic fields and liquid crystalline media

    International Nuclear Information System (INIS)

    Residual dipolar couplings (RDCs) complement standard NOE distance and J-coupling torsion angle data to improve the local and global structure of biomolecules in solution. One powerful application of RDCs is for domain orientation studies, which are especially valuable for structural studies of nucleic acids, where the local structure of a double helix is readily modeled and the orientations of the helical domains can then be determined from RDC data. However, RDCs obtained from only one alignment media generally result in degenerate solutions for the orientation of multiple domains. In protein systems, different alignment media are typically used to eliminate this orientational degeneracy, where the combination of RDCs from two (or more) independent alignment tensors can be used to overcome this degeneracy. It is demonstrated here for native E. coli tRNAVal that many of the commonly used liquid crystalline alignment media result in very similar alignment tensors, which do not eliminate the 4-fold degeneracy for orienting the two helical domains in tRNA. The intrinsic magnetic susceptibility anisotropy (MSA) of the nucleobases in tRNAVal was also used to obtain RDCs for magnetic alignment at 800 and 900 MHz. While these RDCs yield a different alignment tensor, the specific orientation of this tensor combined with the high rhombicity for the tensors in the liquid crystalline media only eliminates two of the four degenerate orientations for tRNAVal. Simulations are used to show that, in optimal cases, the combination of RDCs obtained from liquid crystalline medium and MSA-induced alignment can be used to obtain a unique orientation for the two helical domains in tRNAVal

  9. Black Holes and Magnetic Fields

    OpenAIRE

    Hejda, Filip; Bi?ák, Ji?í

    2015-01-01

    We briefly summarise the basic properties of spacetimes representing rotating, charged black holes in strong axisymmetric magnetic fields. We concentrate on extremal cases, for which the horizon surface gravity vanishes. We investigate their properties by finding simpler spacetimes that exhibit their geometries near degenerate horizons. Employing the simpler geometries obtained by near-horizon limiting description we analyse the Meissner effect of magnetic field expulsion fr...

  10. Black Holes and Magnetic Fields

    CERN Document Server

    Hejda, Filip

    2015-01-01

    We briefly summarise the basic properties of spacetimes representing rotating, charged black holes in strong axisymmetric magnetic fields. We concentrate on extremal cases, for which the horizon surface gravity vanishes. We investigate their properties by finding simpler spacetimes that exhibit their geometries near degenerate horizons. Employing the simpler geometries obtained by near-horizon limiting description we analyse the Meissner effect of magnetic field expulsion from extremal black holes.

  11. Sensor-less Field Oriented Control of Wind Turbine Driven Permanent Magnet Synchronous Generator Using Flux Linkage and Back EMF Estimation Methods

    Directory of Open Access Journals (Sweden)

    Porselvi Thayumanavan

    2014-05-01

    Full Text Available The study aims at the speed control of the wind turbine driven Permanent Magnet Synchronous Generator (PMSG by sensor-less Field Oriented Control (FOC method. Two methods of sensor-less FOC are proposed to control the speed and torque of the PMSG. The PMSG and the full-scale converter have an increasing market share in variable speed Wind Energy Conversion System (WECS. When compared to the Induction Generators (IGs, the PMSGs are smaller, easier to control and more efficient. In addition, the PMSG can operate at variable speeds, so that the maximum power can be extracted even at low or medium wind speeds. Wind turbines generally employ speed sensors or shaft position encoders to determine the speed and the position of the rotor. In order to reduce the cost, maintenance and complexity concerned with the sensor, the sensor-less approach has been developed. This study presents the sensor-less control techniques using the flux-linkage and the back EMF estimation methods. Simulations for both the methods are carried out in MATLAB/SIMULINK. The simulated waveforms of the reference speed, the measured speed, the reference torque, the measured torque and rotor position are shown for both the methods.

  12. Study of marine magnetic field

    Digital Repository Service at National Institute of Oceanography (India)

    Bhattacharya, G.C.

    to that of a magnet, as if there is a powerful bar magnet at the center of the Earth aligned close to the axis of rotation of the Earth with lines of force passing between northern and southern hemispheres. However, this magnet is not aligned exactly... along the axis of rotation but is presently tilted by 11.5° with respect to the axis of rotation, and so the magnetic north as given by a compass, generally differs from geographic or ‘true north’. The places where the axis of the geomagnetic field...

  13. Magnetic Fields in Spiral Galaxies

    OpenAIRE

    Beck, Rainer

    2015-01-01

    Radio synchrotron emission is a powerful tool to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30\\mu G) and in central starburst regions (50-100\\mu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbule...

  14. Cosmic Microwave Background Radiation anisotropy with primordial magnetic fields

    OpenAIRE

    Koh, Seoktae; Lee, Chul H.

    2000-01-01

    Galactic magnetic fields are observed of order $\\sim 10^{-6}G$, but their origin is not definitely known yet. In this paper we consider the primordial magnetic fields generated in the early universe and analyse their effects on the density perturbations and the CMBR anisotropy. We assume that the random magnetic fields have the power law spectrum and satisfy the force-free field condition. The peak heights of the CMBR anisotropy are shown to be shifted upward depending o...

  15. Magnetic nanoparticles for applications in oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Peeraphatdit, Chorthip

    2010-12-15

    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.

  16. Magnetic field effect on hemin

    Science.gov (United States)

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

    2001-12-01

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

  17. Distortion of magnetic field and magnetic force of a brushless dc motor due to deformed rubber magnet

    Science.gov (United States)

    Lee, C. J.; Jang, G. H.

    2008-04-01

    This paper investigates the distortion of magnetic field of a brushless dc (BLDC) motor due to deformed rubber magnet. Global or local deformation of rubber magnet in the BLDC motor is mathematically modeled by using the Fourier series. Distorted magnetic field is calculated by using the finite element method, and unbalanced magnetic force is calculated by using the Maxwell stress tensor. When the rubber magnet is globally or locally deformed, the unbalanced magnetic force has the frequencies with the first harmonic and the harmonics of slot number ±1. However, the harmonic deformation with multiple of common divisor of pole and slot does not generate unbalanced magnetic force due to the rotational symmetry.

  18. Ultralow Magnetic Fields and Gravity Probe B Gyroscope Readout

    Science.gov (United States)

    Mester, J. C.; Lockhart, J. M.; Muhlfelder, B.; Murray, D. O.; Taber, M. A.

    We describe the generation of an ultralow magnetic field of materials control program. A high performance magnetic shield system is required for the proper function of gyroscope readout. The readout system employs a dc SQUID to measure the London moment generated by the superconducting gyro rotor in order to resolve sub-milliarcsecond changes in the gyro spin direction. In addition to a low residual dc magnetic field, attenuation of external field variation is required to be 1012 at the gyro positions. We discuss the measurement of the dc magnetic field and ac attenuation factor and the performance of the readout system

  19. The effects of self-generated and applied magnetic fields on the computation of flow over a Mars return aerobrake

    Science.gov (United States)

    Palmer, Grant

    1991-01-01

    A CFD technique is developed to calculate the electromagnetic phenomena simultaneously with the fluid flow in the shock layer over an axisymmetric blunt body in a thermal-equilibrium chemical-nonequilibrium environment. The flowfield is solved using an explicit time-marching, first-order spatially accurate scheme. The electromagnetic phenomena are coupled to the real-gas flow solver through an iterative procedure. The electromagnetic terms introduce a strong stiffness, which was overcome by using significantly smaller time steps for the electromagnetic conservation equation. The technique is applied in calculating the flow over a Mars return aerobrake vehicle entering the Earth's atmosphere. For the case where no external field is applied, the electromagnetic effects have little impact on the flowfield.

  20. Magnetic fields a comprehensive theoretical treatise for practical use

    CERN Document Server

    Knoepfel, Heinz E

    2000-01-01

    A unique resource for physicists and engineers working with magnetic fieldsAn understanding of magnetic phenomena is essential for anyone working on the practical application of electromagnetic theory. Magnetic Fields: A Comprehensive Theoretical Treatise for Practical Use provides physicists and engineers with a thorough treatment of the magnetic aspects of classical electromagnetic theory, focusing on key issues and problems arising in the generation and application of magnetic fields. From magnetic potentials and diffusion phenomena to magnetohydrodynamics and properties of matter-topics are carefully selected for their relevance to the theoretical framework as well as current technologies

  1. Magnetic Field System of PERC

    International Nuclear Information System (INIS)

    Full text: The beam station PERC (Proton Electron Radiation Channel) is a new kind of spectrometer for neutron beta decay experiments, aiming to achieve precise measurements of energy spectra of electrons and protons (e-/p+) from free neutron decay, as well as various angular correlation coefficients that represent the properties of the weak and strong interactions. The main instrument of PERC provides a static magnetic eld supported by a series of superconducting magnets, to collect and guide the charged decay e-/p+ particles from the decay to the detection area. To obtain high efficiencies and suppressed error levels, the strengths of the magnetic eld have a functional distribution, with which the e-/p+ can be selected and defined due to their emission angles. In order to realize precise measurements, the decay e-/p+ are required to be transported with distortion of the observables below 10-4. Hence the functional magnetic fields must be well defined and homogeneous. To fulfill the requirements of systematics and physics, the magnet system of PERC is delicately designed with a dromedary geometry. The properties of the magnetic fields, the e-/p+ behaviors and the systematic effects are well studied in the simulations. Additionally, the practical and experimental factors are considered in the design of PERC, including the manufacture requirements, the tolerances of the field functions due to external influences, the properties of superconducting wire, and the magnetic forces and torques on the components. (author)

  2. Quench limits in the next generation of magnets

    OpenAIRE

    Todesco, E.

    2014-01-01

    Several projects around the planet aim at building a new generation of superconducting magnets for particle accelerators, relying on Nb3Sn conductor, with peak fields in the range of 10-15 T. In this paper we give an overview of the main challenges for protecting this new generation of magnets. The cases of isolated short magnets, in which the energy can be extracted on an external dump resistor, and chain of long magnets, which have to absorb their stored energy and have to...

  3. The formation of regular interarm magnetic fields in spiral galaxies

    Science.gov (United States)

    Moss, D.; Stepanov, R.; Krause, M.; Beck, R.; Sokoloff, D.

    2015-06-01

    Context. Observations of regular magnetic fields in several nearby galaxies reveal magnetic arms situated between the material arms. The nature of these magnetic arms is a topic of active debate. Previously, we found a hint that taking into account the effects of injections of small-scale magnetic fields (e.g. generated by turbulent dynamo action) into the large-scale galactic dynamo can result in magnetic arm formation. Aims: We now investigate the joint roles of an arm/interarm turbulent diffusivity contrast and injections of small-scale magnetic field on the formation of large-scale magnetic field ("magnetic arms") in the interarm region. Methods: We use the relatively simple "no-z" model for the galactic dynamo. This involves projection onto the galactic equatorial plane of the azimuthal and radial magnetic field components; the field component orthogonal to the galactic plane is estimated from the solenoidality condition. Results: We find that the addition of diffusivity gradients to the effects of magnetic field injections makes the magnetic arms much more pronounced. In particular, the regular magnetic field component becomes larger in the interarm space than that within the material arms. Conclusions: The joint action of the turbulent diffusivity contrast and small-scale magnetic field injections (with the possible participation of other effects previously suggested) appears to be a plausible explanation for the phenomenon of magnetic arms.

  4. On the relationship between quadrupolar magnetic field and collisionless reconnection

    Energy Technology Data Exchange (ETDEWEB)

    Smets, R., E-mail: roch.smets@lpp.polytechnique.fr; Belmont, G. [LPP, University P. and M. Curie, CNRS, Ecole Polytechnique, F-91128 Palaiseau (France); Aunai, N. [IRAP, University Paul Sabatier, F-31028 Toulouse (France); Boniface, C. [CEA/DAM, DIF, F-91297 Arpajon (France); Fuchs, J. [LULI, Ecole Polytechnique, CNRS, CEA, University P. and M. Curie, F-91128 Palaiseau (France)

    2014-06-15

    Using hybrid simulations, we investigate the onset of fast reconnection between two cylindrical magnetic shells initially close to each other. This initial state mimics the plasma structure in High Energy Density Plasmas induced by a laser-target interaction and the associated self-generated magnetic field. We clearly observe that the classical quadrupolar structure of the out-of-plane magnetic field appears prior to the reconnection onset. Furthermore, a parametric study reveals that, with a non-coplanar initial magnetic topology, the reconnection onset is delayed and possibly suppressed. The relation between the out-of-plane magnetic field and the out-of-plane electric field is discussed.

  5. About possibility to measure an electric dipole moment (EDM) of nuclei in the range $10^{-27} \\div 10^{-32}$ $e \\cdot cm$ in experiments for search of time-reversal violating generation of magnetic and electric fields

    OpenAIRE

    Baryshevsky, Vladimir

    2004-01-01

    The possibility to measure an electric dipole moment (EDM) of nuclei in the range $10^{-27} \\div 10^{-32}$ $e \\cdot cm$ in experiments for search of time-reversal violating generation of magnetic and electric fields is discussed.

  6. Transformation Optics for Controlling DC Magnetic Field

    OpenAIRE

    Sun, Fei

    2014-01-01

    Based on the form-invariant of Maxwell’s equations under coordinate transformations, we extend the theoryof transformation optics to transformation magneto-statics, which can design magnets through coordinatetransformations. Some novel DC magnetic field illusions created by magnets (e.g. rescaling magnets,cancelling magnets and overlapping magnets) are designed and verified by numerical simulations. Ourresearch will open a new door to designing magnets and controlling DC magnetic fields.

  7. Influence of clamping plate permeability and metal screen structures on three-dimensional magnetic field and eddy current loss in end region of a turbo-generator by numerical analysis

    Science.gov (United States)

    Likun, Wang; Weili, Li; Yi, Xue; Chunwei, Guan

    2013-11-01

    A significant problem of turbogenerators on complex end structures is overheating of local parts caused by end losses in the end region. Therefore, it is important to investigate the 3-D magnetic field and eddy current loss in the end. In end region of operating large turbogenerator at thermal power plants, magnetic leakage field distribution is complex. In this paper, a 3-D mathematical model used for the calculation of the electromagnetic field in the end region of large turbo-generators is given. The influence of spatial locations of end structures, the actual shape and material of end windings, clamping plate, and copper screen are considered. Adopting the time-step finite element (FE) method and taking the nonlinear characteristics of the core into consideration, a 3-D transient magnetic field is calculated. The objective of this paper is to investigate the influence of clamping plate permeability and metal screen structures on 3-D electromagnetic field distribution and eddy current loss in end region of a turbo-generator. To reduce the temperature of copper screen, a hollow metal screen is proposed. The eddy current loss, which is gained from the 3D transient magnetic field, is used as heat source for the thermal field of end region. The calculated temperatures are compared with test data.

  8. Magnetic Fields in Spiral Galaxies

    CERN Document Server

    Beck, Rainer

    2015-01-01

    Radio synchrotron emission is a powerful tool to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30\\mu G) and in central starburst regions (50-100\\mu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15\\mu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the interg...

  9. The Protogalactic Origin for Cosmic Magnetic Fields

    CERN Document Server

    Kulsrud, R M; Ostriker, J P; Ryu, D; Kulsrud, Russell M.; Cen, Renyue; Ostriker, Jeremiah P.; Ryu, Dongsu

    1996-01-01

    It is demonstrated that strong magnetic fields are produced from a zero initial magnetic field during the pregalactic era, when galaxies are first forming. Their development proceeds in three phases. In the first phase, weak magnetic fields are created by the Biermann battery mechanism, acting in shocked parts of the intergalactic medium where caustics form and intersect. In the second phase, these weak magnetic fields are amplified to strong magnetic fields by the Kolmogoroff turbulence endemic to gravitational structure formation of galaxies. During this second phase, the magnetic fields reach saturation with the turbulent power, but they are coherent only on the scale of the smallest eddy. In the third phase, the magnetic field strength increases to equipartition with the turbulent energy, and the coherence length of the magnetic fields increases to the scale of the largest turbulent eddy, comparable to the scale of the entire galaxy. The resulting magnetic field represents a galactic magnetic field of pri...

  10. Magnetic Field Limits on SGRs

    CERN Document Server

    Rothschild, R E; Lingenfelter, R E

    1999-01-01

    We measure the period and spin-down rate for SGR 1900+14 during the quiescient period two years before the recent interval of renewed burst activity. We find that the spin-down rate doubled during the burst activity which is inconsistent with both mangetic dipole driven spin down and a magnetic field energy source for the bursts. We also show that SGRs 1900+14 and 1806-20 have braking indices of $\\sim$1 which indicate that the spin-down is due to wind torques and not magnetic dipole radiation. We further show that a combination of dipole radiation, and wind luminosity, coupled with estimated ages and present spin parameters, imply that the magnetic fields of SGRs 1900+14 and 1806-20 are less than the critical field of 4$\\times10^{13}$ G and that the efficiency for conversion of wind luminosity to x-ray luminosity is <2%.

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

    Science.gov (United States)

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

    2009-05-19

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

  12. Velocity and magnetic field structures in a magnetohydrodynamic dynamo

    International Nuclear Information System (INIS)

    Computer simulation of the magnetohydrodynamic dynamo in a rotating spherical shell geometry is performed. The convection velocity and the magnetic field structures are investigated in detail when the magnetic field is exponentially growing. It is found that the magnetic energy is strongly localized in space. The energy is generated when toroidal field lines are stretched by the fluid flows in columnar convection cells. copyright 1997 American Institute of Physics

  13. Magnetic Fields at Largest Universal Strengths: Overview

    Science.gov (United States)

    Beskin, V. S.; Balogh, A.; Falanga, M.; Treumann, R. A.

    2015-10-01

    A brief review is given about the role strong magnetic fields play in the universe. We list the main observational and theoretical achievements treated in the following chapters including a number of open questions which future research is going to attack. Strong fields in the universe exceed any large scale fields by several orders of magnitude, at first glance suggesting that their generation mechanisms would be different. However, it is believed that gravitational collapse and magnetic flux conservation is responsible for the amplification of fields generated in the progenitors to the observed strengths. In this sense the extremely strong fields are mainly fossil, and their variety confirms the different masses and stages where the collapse comes to rest, at the lightest in white dwarfs and at the strongest in magnetars, which are a particular class of neutron stars with strongly inhomogeneous particularly structured crust. Various effects related to the detection of such fields, radiation generation and consequences for the environment are pointed out and referred to the relevant chapters in this volume.

  14. Polar Magnetic Field Data

    Science.gov (United States)

    Russell, Christopher T.; Hoffman, Robert (Technical Monitor)

    2002-01-01

    At this writing we have received all the CDROMs for the grant period. We have completed generating our timing tables past September 20, 2001. The calibration of the instrument has been checked for the entire mission up to the end of December 2000 and the key parameters provided to the project until the end of December 2000. These data are available to other experimenters over the web at http://www-ssc.igpp.ucla.edu/forms/polar/. High resolution spun data, 8 samples per see, have been created up to November, 2000 and have been made available to the community over the world wide web. This is a new data set that was a major effort this year. Our near term plans are to continue to provide key parameter data to the Polar project with the highest possible speed and to continue to reduce all high resolution magnetometer data and provide these data to the scientific community over the web.

  15. Focus on Materials Analysis and Processing in Magnetic Fields

    Directory of Open Access Journals (Sweden)

    Yoshio Sakka, Noriyuki Hirota, Shigeru Horii and Tsutomu Ando

    2009-01-01

    Full Text Available Recently, interest in the applications of feeble (diamagnetic and paramagnetic magnetic materials has grown, whereas the popularity of ferromagnetic materials remains steady and high. This trend is due to the progress of superconducting magnet technology, particularly liquid-helium-free superconducting magnets that can generate magnetic fields of 10 T and higher. As the magnetic energy is proportional to the square of the applied magnetic field, the magnetic energy of such 10 T magnets is in excess of 10 000 times that of conventional 0.1 T permanent magnets. Consequently, many interesting phenomena have been observed over the last decade, such as the Moses effect, magnetic levitation and the alignment of feeble magnetic materials. Researchers in this area are widely spread around the world, but their number in Japan is relatively high, which might explain the success of magnetic field science and technology in Japan.Processing in magnetic fields is a rapidly expanding research area with a wide range of promising applications in materials science. The 3rd International Workshop on Materials Analysis and Processing in Magnetic Fields (MAP3, which was held on 14–16 May 2008 at the University of Tokyo, Japan, focused on various topics including magnetic field effects on chemical, physical, biological, electrochemical, thermodynamic and hydrodynamic phenomena; magnetic field effects on the crystal growth and processing of materials; diamagnetic levitation, the magneto-Archimedes effect, spin chemistry, magnetic orientation, control of structure by magnetic fields, magnetic separation and purification, magnetic-field-induced phase transitions, properties of materials in high magnetic fields, the development of NMR and MRI, medical applications of magnetic fields, novel magnetic phenomena, physical property measurement by magnetic fields, and the generation of high magnetic fields.This focus issue compiles 13 key papers selected from the proceedings of MAP3. Other papers of the proceedings are published in Journal of Physics: Conference Series. Tournier and Beaugnon review experimental texturing in metallic melts by cooling in magnetic fields, which is modeled in detail in a study by Tournier. Wang et al provide further experimental results on the solidification of Mn-90.4 wt % Sb alloy in magnetic fields. The orientations of grains and particles induced by magnetic fields is reported by Horii et al (rare-earth-doped cuprates, Tanaka et al (barium-bismuth titanate ceramics, Liu and Schwartz (Bi2Sr2CaCu2Ox/AgMg wires and Tsuda and Sakka (carbon nanotubes. Gielen et al present a model of how to quantify a molecular alignment using magnetic birefringence, and Ando et al simulate the movement of feeble particles in magnetic fields. Hirota et al report the experimental control of the lattice constant in a triangular lattice of feeble magnetic particles. The size separation of diamagnetic particles by magnetic fields is experimentally studied by Tarn et al and theoretically studied by Fukui et al. A setup measuring x-ray diffraction patterns in magnetic fields up to 5 T and temperatures above 200 oC has been developed by Mitsui et al.We hope that this focus issue will help readers to understand several aspects of materials analysis and processing in magnetic fields at the frontier of the science.

  16. Chiral transition with magnetic fields

    CERN Document Server

    Ayala, Alejandro; Mizher, Ana Julia; Rojas, Juan Cristobal; Villavicencio, Cristian

    2014-01-01

    We study the nature of the chiral transition for an effective theory with spontaneous breaking of symmetry, where charged bosons and fermions are subject to the effects of a constant external magnetic field. The problem is studied in terms of the relative intensity of the magnetic field with respect to the mass and the temperature. When the former is the smallest of the scales, we present a suitable method to obtain magnetic and thermal corrections up to ring order at high temperature. By these means, we solve the problem of the instability in the boson sector for these theories, where the squared masses, taken as functions of the order parameter, can vanish and even become negative. The solution is found by considering the screening properties of the plasma, encoded in the resummation of the ring diagrams at high temperature. We also study the case where the magnetic field is the intermediate of the three scales and explore the nature of the chiral transition as we vary the field strength, the coupling const...

  17. Quench limits in the next generation of magnets

    CERN Document Server

    Todesco, E

    2013-01-01

    Several projects around the planet aim at building a new generation of superconducting magnets for particle accelerators, relying on Nb3Sn conductor, with peak fields in the range of 10-15 T. In this paper we give an overview of the main challenges for protecting this new generation of magnets. The cases of isolated short magnets, in which the energy can be extracted on an external dump resistor, and chain of long magnets, which have to absorb their stored energy and have to rely on quench heaters, are discussed. We show that this new generation of magnets can pose special challenges, related to both the large current density and to the energy densities.

  18. Instability of ferrofluid magnetic drops under magnetic field

    OpenAIRE

    Bacri, J.C.; Salin, D.

    1982-01-01

    We have followed the evolution of the shape of ferrofluid magnetic drops in presence of a magnetic field. The prolate ellipsoid shape of the drop becomes unstable for a certain magnetic field threshold : the drop jumps from a slightly elongated shape to a much more elongated shape. When decreasing the magnetic field the same feature occurs for a smaller threshold. This instability is simply understood from a balance between magnetic energy and interfacial tension energy.

  19. The energy budget of stellar magnetic fields

    CERN Document Server

    See, V; Vidotto, A A; Donati, J -F; Folsom, C P; Saikia, S Boro; Bouvier, J; Fares, R; Gregory, S G; Hussain, G; Jeffers, S V; Marsden, S C; Morin, J; Moutou, C; Nascimento, J D do; Petit, P; Rosen, L; Waite, I A

    2015-01-01

    Spectropolarimetric observations have been used to map stellar magnetic fields, many of which display strong bands of azimuthal fields that are toroidal. A number of explanations have been proposed to explain how such fields might be generated though none are definitive. In this paper, we examine the toroidal fields of a sample of 55 stars with magnetic maps, with masses in the range 0.1-1.5$\\,{\\rm M}_\\odot$. We find that the energy contained in toroidal fields has a power law dependence on the energy contained in poloidal fields. However the power index is not constant across our sample, with stars less and more massive than 0.5$\\,{\\rm M}_\\odot$ having power indices of 0.72$\\pm$0.08 and 1.25$\\pm$0.06 respectively. There is some evidence that these two power laws correspond to stars in the saturated and unsaturated regimes of the rotation-activity relation. Additionally, our sample shows that strong toroidal fields must be generated axisymmetrically. The latitudes at which these bands appear depend on the ste...

  20. The energy budget of stellar magnetic fields

    Science.gov (United States)

    See, V.; Jardine, M.; Vidotto, A. A.; Donati, J.-F.; Folsom, C. P.; Boro Saikia, S.; Bouvier, J.; Fares, R.; Gregory, S. G.; Hussain, G.; Jeffers, S. V.; Marsden, S. C.; Morin, J.; Moutou, C.; do Nascimento, J. D.; Petit, P.; Rosén, L.; Waite, I. A.

    2015-11-01

    Spectropolarimetric observations have been used to map stellar magnetic fields, many of which display strong bands of azimuthal fields that are toroidal. A number of explanations have been proposed to explain how such fields might be generated though none are definitive. In this paper, we examine the toroidal fields of a sample of 55 stars with magnetic maps, with masses in the range 0.1-1.5 M?. We find that the energy contained in toroidal fields has a power-law dependence on the energy contained in poloidal fields. However the power index is not constant across our sample, with stars less and more massive than 0.5 M? having power indices of 0.72 ± 0.08 and 1.25 ± 0.06, respectively. There is some evidence that these two power laws correspond to stars in the saturated and unsaturated regimes of the rotation-activity relation. Additionally, our sample shows that strong toroidal fields must be generated axisymmetrically. The latitudes at which these bands appear depend on the stellar rotation period with fast rotators displaying higher latitude bands than slow rotators. The results in this paper present new constraints for future dynamo studies.

  1. Contribution of the background magnetic field and magnetic fields of active regions and sunspots to the solar mean magnetic field

    International Nuclear Information System (INIS)

    The influence of the background magnetic fields, magnetic fields of active regions and sunspots on the solar general fields is studied. The mean field has been measured by the small tower solar telescope at the Crimean Astrophysical Observatory for the period from 6.06.74 to 15.09.74. The background and magnetic field of active regions data are oftained from literature sources. By means of the correlation analysis correlation coefficients of general field intensity with background fields magnetic flux 0,87+-0,027 with resultant magnetic flux from active regions 0,75+-0,075 and with resultant spot magnetic flux 0,11+-0,097 Background fields of the central solar zone make the main contribution to the general field. Magnetic fluxes from active regions and spots make a substantial contribution to the general field, in case the background field flux being small

  2. Experimental Study on Current Decay Characteristics of Persistent Current HTS Magnet by Alternating Magnetic Field

    Science.gov (United States)

    Park, Young Gun; Lee, Chang Young; Hwang, Young Jin; Lee, Woo Seung; Lee, Jiho; Jo, Hyun Chul; Chung, Yoon Do; Ko, Tae Kuk

    This paper deals with a current decay characteristics of a high temperature superconducting (HTS) magnet operated in persistent current mode (PCM). In superconducting synchronous machine applications such as linear synchronous motor (LSM), the superconducting coil is designed to operate in the PCM to obtain steady magnetic field with DC transport current. This superconducting magnet operates on a direct current, but it can be exposed to alternating magnetic field due to the armature winding. When the magnet is subjected to an external time-varying magnetic field, it is possible to result in a decay of the current in PCM system due to AC loss. In this research, a PCM system with armature coil which generates time-varying magnetic field was fabricated to verify current decay characteristics by external alternating magnetic field. The current decay rate was measured by using a hall sensor as functions of amplitude and frequency of armature coil.

  3. Nonlinear spin-wave excitations at low magnetic bias fields.

    Science.gov (United States)

    Bauer, Hans G; Majchrak, Peter; Kachel, Torsten; Back, Christian H; Woltersdorf, Georg

    2015-01-01

    Nonlinear magnetization dynamics is essential for the operation of numerous spintronic devices ranging from magnetic memory to spin torque microwave generators. Examples are microwave-assisted switching of magnetic structures and the generation of spin currents at low bias fields by high-amplitude ferromagnetic resonance. Here we use X-ray magnetic circular dichroism to determine the number density of excited magnons in magnetically soft Ni80Fe20 thin films. Our data show that the common model of nonlinear ferromagnetic resonance is not adequate for the description of the nonlinear behaviour in the low magnetic field limit. Here we derive a model of parametric spin-wave excitation, which correctly predicts nonlinear threshold amplitudes and decay rates at high and at low magnetic bias fields. In fact, a series of critical spin-wave modes with fast oscillations of the amplitude and phase is found, generalizing the theory of parametric spin-wave excitation to large modulation amplitudes. PMID:26374256

  4. Spontaneous excitation of magnetic fields and collapse dynamics in a Langmuir plasma

    International Nuclear Information System (INIS)

    Various aspects of the spontaneous generation of magnetic fields in a Langmuir plasma are discussed. It is shown that the correct general expression for the ponderomotive force leads to the solenoidal current responsible for the magnetic-field generation. The ponderomotive-force expression and also the magnetic-field generation equations from a two-time-scale two-fluid description are derived. A kinetic approach is used to derive the magnetic-field generation equations. A virial theorem is used to show that the self-generated magnetic field does not stabilize the wave collapse. (author)

  5. Oxide superconductors under magnetic field

    Science.gov (United States)

    Kitazawa, K.

    1991-01-01

    One of the current most serious problems for the oxide superconductors from the standpoint of practical application is the various novel features derived mainly from their extremely short coherence. In particular, the coherence length so far observed in the cuprate superconductors is in the range of 0.1 nm perpendicular to the CuO2 plane. This seems to be creating most of the difficulties in the device fabrication and in the performance under the magnetic field. Some of the superconducting properties under the magnetic field will be discussed in terms of the short coherence length. A model will be presented based on the gradual strengthening of the pinning force with decrease in temperature and the weak coupling at the grain boundaries. Secondly, the broadening of the superconducting transition under the magnetic field is discussed. This is observed significantly only when the field is applied perpendicular to the basal plane and the relative orientation of the current to the field is insignificant in determining the extent of broadening. Besides, the change in the strength of the pinning force does not affect the width of the broadening. From these observations discussions will be made on a model based on the giant fluctuation. Based on this model, it is predicted that the coherence length along the c-axis will be the single most important material parameter to determine the performance of the superconductor under a strong magnetic field. It seems that BYCO is superior in this regard to Bi- or Tl-systems as far as the performance at 77 K is considered, although another material with the coherence length slightly longer along the c-axis is still highly desired.

  6. Evolution of primordial magnetic fields in mean-field approximation

    CERN Document Server

    Campanelli, Leonardo

    2013-01-01

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

  7. Galactic and intergalactic magnetic fields

    CERN Document Server

    Klein, Ulrich

    2014-01-01

    This course-tested textbook conveys the fundamentals of magnetic fields and relativistic plasma in diffuse cosmic media, with a primary focus on phenomena that have been observed at different wavelengths. Theoretical concepts are addressed wherever necessary, with derivations presented in sufficient detail to be generally accessible.In the first few chapters the authors present an introduction to various astrophysical phenomena related to cosmic magnetism, with scales ranging from molecular clouds in star-forming regions and supernova remnants in the Milky Way, to clusters of galaxies. Later c

  8. Magnetic fields of accreting pulsars

    OpenAIRE

    Doroshenko, Victor

    2011-01-01

    Accreting pulsars are rotating, highly magnetized neutron stars in binary systems which emit pulsed X-rays. This emission is powered by the gravitational energy of the plasma accreted from a non degenerate companion funneled onto the polar caps of the neutron star by the magnetic field, and thermalized to X-rays either in the impact with the surface of the neutron star, or in the so-called accretion column. Although discovered more than forty years ago many aspects of the emission form accret...

  9. Primordial magnetic fields from the string network

    CERN Document Server

    Horiguchi, Kouichirou; Sugiyama, Naoshi

    2016-01-01

    Cosmic strings are a type of cosmic defect formed by a symmetry-breaking phase transition in the early universe. Individual strings would have gathered to build a network, and their dynamical motion would induce scalar--, vector-- and tensor--type perturbations. In this paper, we focus on the vector mode perturbations arising from the string network based on the one scale model and calculate the time evolution and the power spectrum of the associated magnetic fields. We show that the relative velocity between photon and baryon fluids induced by the string network can generate magnetic fields over a wide range of scales based on standard cosmology. We obtain the magnetic field spectrum before recombination as $a^2B(k,z)\\sim4\\times10^{-16}G\\mu/((1+z)/1000)^{4.25}(k/{\\rm Mpc}^{-1})^{3.5}$ Gauss on super-horizon scales, and $a^2B(k,z)\\sim2.4\\times10^{-17}G\\mu/((1+z)/1000)^{3.5}(k/{\\rm Mpc}^{-1})^{2.5}$ Gauss on sub-horizon scales in co-moving coordinates. This magnetic field grows up to the end of recombination, ...

  10. Magnetic field tomography, helical magnetic fields and Faraday depolarization

    OpenAIRE

    Horellou, Cathy; Fletcher, Andrew

    2014-01-01

    Wide-band radio polarization observations offer the possibility to recover information about the magnetic fields in synchrotron sources, such as details of their three-dimensional configuration, that has previously been inaccessible. The key physical process involved is the Faraday rotation of the polarized emission in the source (and elsewhere along the wave's propagation path to the observer). In order to proceed, reliable methods are required for inverting the signals obs...

  11. High-magnetic-field research collaborations

    International Nuclear Information System (INIS)

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The purpose of this project was to develop collaborations with the academic community to exploit scientific research potential of the pulsed magnetic fields that might be possible with electrically pulsed devices, as well as magneto-cumulative generators. The author started with a campaign of experiments using high-explosive-driven flux compression generators. The campaign's objective was to explore completely novel ideas in condensed-matter physics and chemistry. The initiative was very successful in pulling together top researchers from around the world

  12. Demagnetizing fields in active magnetic regenerators

    DEFF Research Database (Denmark)

    Nielsen, Kaspar Kirstein; Bahl, Christian R.H.; Smith, Anders

    2014-01-01

    A magnetic material in an externally applied magnetic field will in general experience a spatially varying internal magnetic field due to demagnetizing effects. When the performance of active magnetic regenerators (AMRs) is evaluated using numerical models the internal field is often assumed to be spatially constant and equal to the applied field, thus neglecting the demagnetizing field. Furthermore, the experimental magnetocaloric properties used (adiabatic temperature change, isothermal entrop...

  13. A Vorticity-Magnetic Field Dynamo Instability

    OpenAIRE

    Blackman, Eric G; Chou, Tom

    1997-01-01

    We generalize the mean field magnetic dynamo to include local evolution of the mean vorticity in addition to the mean magnetic field. The coupled equations exhibit a general mean field dynamo instability that enables the transfer of turbulent energy to the magnetic field and vorticity on larger scales. The growth of the vorticity and magnetic field both require helical turbulence which can be supplied by an underlying global rotation. The dynamo coefficients are derived incl...

  14. RESICALC: Magnetic field modeling program

    International Nuclear Information System (INIS)

    RESICALC, Version 1.0, is a Microsoft Windows application that describes the magnetic field environment produced by user-defined arrays of transmission lines, distribution lines, and custom conductors. These arrays simulate specific situations that may be encountered in real-world community settings. RESICALC allows the user to define an area or ''world'' that contains the transmission and/or distribution lines, user-defined conductors, and locations of residences. The world contains a ''reference grid'' within which RESICALC analyzes the magnetic field environment due to all conductors within the world. Unique physical parameters (e.g., conductor height and spacing) and operating characteristics can be assigned to all electrical conductors. RESICALC's output is available for the x, y, z axis separately, the resultant (the three axes added in quadrature), and the major axis, each in three possible formats: a three-dimensional map of the magnetic field, two dimensional-contours, and as a table with statistical values. All formats may be printed, accompanied by a three-dimensional view of the world the user has drawn. The view of the world and the corresponding three-dimensional field map may be adjusted to the elevation and rotation angle of the user's preference

  15. Mesoscopic persistent currents in a strong magnetic field

    OpenAIRE

    Ginossar, E; Glazman, LI; Ojanen, T.; von Oppen, F; Shanks, WE; Bleszynski-Jayich, AC; Harris, JGE

    2010-01-01

    Recent precision measurements of mesoscopic persistent currents in normal-metal rings rely on the interaction between the magnetic moment generated by the current and a large applied magnetic field. Motivated by this technique, we extend the theory of mesoscopic persistent currents to include the effect of the finite thickness of the ring and the resulting penetration of the large magnetic field. We discuss both the sample-specific typical current and the ensemble-averaged c...

  16. Higher dimensional black holes in external magnetic fields

    OpenAIRE

    Ortaggio, Marcello

    2004-01-01

    We apply a Harrison transformation to higher dimensional asymptotically flat black hole solutions, which puts them into an external magnetic field. First, we magnetize the Schwarzschild-Tangherlini metric in arbitrary spacetime dimension n>=4. The thus generated exact solution of the Einstein-Maxwell equations describes a static black hole immersed in a Melvin "fluxbrane", and generalizes previous results by Ernst for the case n=4. The magnetic field deforms the shape of the...

  17. Magnetic flux generator for balanced membrane loudspeaker

    DEFF Research Database (Denmark)

    Rehder, Jörg; Rombach, Pirmin

    2002-01-01

    This paper reports the development of a magnetic flux generator with an application in a hearing aid loudspeaker produced in microsystem technology (MST). The technology plans for two different designs for the magnetic flux generator utilizing a softmagnetic substrate or electroplated NiCoFe as core material are presented and the production and characterization of four different mono- and double-layer planar coil types are reported.

  18. Superposition of DC magnetic fields by cascading multiple magnets in magnetic loops

    Science.gov (United States)

    Sun, Fei; He, Sailing

    2015-09-01

    A novel method that can effectively collect the DC magnetic field produced by multiple separated magnets is proposed. With the proposed idea of a magnetic loop, the DC magnetic field produced by these separated magnets can be effectively superimposed together. The separated magnets can be cascaded in series or in parallel. A novel nested magnetic loop is also proposed to achieve a higher DC magnetic field in the common air region without increasing the DC magnetic field in each magnetic loop. The magnetic loop can be made by a magnetic hose, which is designed by transformation optics and can be realized by the combination of super-conductors and ferromagnetic materials.

  19. Explaining Mercury's peculiar magnetic field

    Science.gov (United States)

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

    2014-05-01

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

  20. Graphene-enhanced, internal-magnetic-field-generated Rabi oscillations in metal-coated Si-SiO2 photoconductive detectors

    CERN Document Server

    Nalla, Venkatram; Loh, Kian Ping; Ji, Wei

    2013-01-01

    We report our demonstration of Rabi oscillations in Si-SiO2-Al photoconductive devices with nanosecond laser pulses of a few nJ at room temperature without external magnetic fields. Zeeman splitting of spin quantum states of dopants in silicon is achieved with internal magnetic fields produced by the Al film under excitation of laser pulses. Rabi oscillation frequency is 15 MHz and 25 MHz when photocurrent direction is perpendicular and parallel, respectively, to the propagation direction of linearly-polarized, 532-nm, 7-ns laser pulses. Insertion of graphene buffer layer between Al and SiO2 provides a three-fold enhancement in Rabi oscillation amplitude. This simple-structured, low-cost device operated at room temperature should open a new avenue for future spin-based electronics and optoelectronics.

  1. Statistics of Magnetic Fields for OB Stars

    CERN Document Server

    Kholtygin, A F; Drake, N A; Bychkov, V D; Bychkova, L V; Chountonov, G A; Burlakova, T E; Valyavin, G G

    2010-01-01

    Based on an analysis of the catalog of magnetic fields, we have investigated the statistical properties of the mean magnetic fields for OB stars. We show that the mean effective magnetic field ${\\cal B}$ of a star can be used as a statistically significant characteristic of its magnetic field. No correlation has been found between the mean magnetic field strength ${\\cal B}$ and projected rotational velocity of OB stars, which is consistent with the hypothesis about a fossil origin of the magnetic field. We have constructed the magnetic field distribution function for B stars, $F({\\cal B})$, that has a power-law dependence on ${\\cal B}$ with an exponent of $\\approx -1.82$. We have found a sharp decrease in the function $F({\\cal B})$F for ${\\cal B}\\lem 400 G$ that may be related to rapid dissipation of weak stellar surface magnetic fields.

  2. Evolution of magnetic field in interacting galaxies

    CERN Document Server

    Drzazga, Robert T; Jurusik, Wojciech

    2012-01-01

    Not much is currently known about how galaxy interactions affect an evolution of galactic magnetic fields. Here, for the first time, we explore a global evolution of magnetic fields with the advance of interaction process.

  3. What Are Electric and Magnetic Fields? (EMF)

    Science.gov (United States)

    ... magnetic fields? Electric and magnetic fields (EMF) are invisible lines of force that surround any electrical device. ... Kids Fun & Games Parents & Teachers Stories Little Kids Web Policies NIEHS Staff: Update This Page Office of ...

  4. Sliding Phases via Magnetic Fields

    CERN Document Server

    Sondhi, S L; Yang, Kun

    2001-01-01

    We show that three dimensional "sliding" analogs of the Kosterlitz-Thouless phase, in stacked classical two-dimensional XY models and quantum systems of coupled Luttinger Liquids, can be enlarged by the application of a parallel magnetic field, which has the effect of increasing the scaling dimensions of the most relevant operators that can perturb the critical sliding phases. Within our renormalization group analysis, we also find that for the case of coupled Luttinger liquids, this effect is interleaved with the onset of the integer quantum Hall effect for weak interactions and fields. We comment on experimental implications for a conjectured smectic metal phase in the cuprates.

  5. The interplanetary magnetic field from a time-dependent solar magnetic field

    International Nuclear Information System (INIS)

    Effects of the time dependence of the sun's magnetic field upon the interplanetary field in the solar wind are considered. General expressions for the interplanetary field are developed under the assumptions that the radial component of the sun's field at some reference surface r0 can be described in terms of spherical harmonics with coefficients which are functions of time represented by Fourier series and that the solar wind expands radially in a steady state flow. Some of the simplest field configurations are examined in additional detail. It is shown that the variation in the sun's field may produce elliptically polarized fluctuations in the interplanetary field; may generate field strengths in the theta direction, i.e., the north-south direction, that are comparable in magnitude to the spiral field; may produce B/sub theta/ with nonzero averages over significant periods of time; and may produce systematic deviations from the nominal steady state spiral angle over such periods

  6. Simulations of magnetic fields in filaments

    OpenAIRE

    Bruggen, M; Ruszkowski, M.; Simionescu, A.; Hoeft, M; Vecchia, C. Dalla

    2005-01-01

    The intergalactic magnetic field within filaments should be less polluted by magnetised outflows from active galaxies than magnetic fields in clusters. Therefore, filaments may be a better laboratory to study magnetic field amplification by structure formation than galaxy clusters which typically host many more active galaxies. We present highly resolved cosmological AMR simulations of magnetic fields in the cosmos and make predictions about the evolution and structure of ma...

  7. Megagauss field generation by the magnetodynamic cumulation on method

    International Nuclear Information System (INIS)

    Experiments data are given on generation of a strong magnetic field by compressing magnetic flux with a conducting cylindrical liner accelerated under the effect of magnetic pressure (magnetodynamic cumulation). The magnetic field for the liner acceleration has been generated by a one-loop solenoid. The total power capacity of the battery for the solenoid pulse supply made Up 700 kJ. The liner is made of aluminium. The liner is 145 mm long, the wall thickness is 2 mm, external diameter is 108 mm, weight is 250 g. The initial magnetic field inside the liner (approximately 10 kGs) has been generated as a result of the 1.5x10-2 F condenser battery discharge (190 kJ at 5 kV). Phases of aluminium liner collapse are shown. The liner kinetic energy acquired during acceleration reached 100 kJ. The experiments have shown a possibility of generating a strong magnetic field of the intensity over 106 Gs as well as the magnetic field 100 times as strong

  8. Saturated magnetic field amplification at supernova shocks

    CERN Document Server

    Luo, Qinghuan

    2009-01-01

    Cosmic-ray streaming instabilities at supernova shocks are discussed in the quasilinear diffusion formalism which takes into account the feedback effect of wave growth on the cosmic ray streaming motion. In particular, the nonresonant instability that leads to magnetic field amplification in the short wavelength regime is considered. The linear growth rate is calculated using kinetic theory for a streaming distribution. We show that the nonresonant instability is actually driven by a compensating current in the background plasma. The nonresonant instability can develop into a nonlinear regime generating turbulence. The saturation of the amplified magnetic fields due to particle diffusion in the turbulence is derived analytically. It is shown that the evolution of parallel and perpendicular cosmic-ray pressures is predominantly determined by nonresonant diffusion. However, the saturation is determined by resonant diffusion which tends to reduce the streaming motion through pitch angle scattering. The saturated...

  9. Electroweak strings, sphalerons and magnetic fields

    CERN Document Server

    Vachaspati, T

    1994-01-01

    We describe electroweak strings and their ability to carry Chern-Simons number. Certain string configurations, for any \\theta_W, carry Chern-Simons number equal to that of the sphaleron and we conjecture that such strings are ``extended sphalerons''. The production of electroweak strings during the phase transition is discussed and it is suggested that electroweak strings could survive long enough for them to play a role in baryogenesis. Finally the issue of magnetic field generation during the electroweak phase transition is addressed and several points not discussed in the existing literature are clarified. A connection is made between electroweak strings and magnetic fields produced at the phase transition. (Based on the talk presented at the NATO workshop on ``Electroweak Physics and the Early Universe'', in Sintra, March 1994)

  10. Solenoid magnet with homogeneous magnetic field

    International Nuclear Information System (INIS)

    This resistive magnet is used noticeably for NMR imaging. It includes many coils, preferably Bitter coils; and some parameters as coil length, distances between coils, their outer diameter are chosen to optimize the product power-mass of the magnet

  11. Pulsed magnetic field distribution near conducting rings

    International Nuclear Information System (INIS)

    Measurements and calculations of the magnetic field distribution in the vicinity of stainless steel rings immersed in a pulsed magnetic field are compared. The computer code TRIDIF is found to produce results in good agreement with the measurements. The perturbations in magnetic field due to the rings are found to be considerably less than one would expect from one-dimensional skin depth considerations

  12. Optical magnetic ?ux generation in superconductor

    Indian Academy of Sciences (India)

    Masayoshi Tonouchi

    2002-05-01

    The generation of the magnetic ?ux quanta inside the superconductors is studied as a new effect to destroy superconductivity using femtosecond (fs) laser. The vortices are successfully generated in the YBa2Cu3O$_{7-\\delta}$ thin ?lm striplines by the fs laser. It is revealed that the vortex distribution in the strip re?ects the fs laser beam pro?le.

  13. Magnetic Helicity and Large Scale Magnetic Fields: A Primer

    CERN Document Server

    Blackman, Eric G

    2014-01-01

    Magnetic fields of laboratory, planetary, stellar, and galactic plasmas commonly exhibit significant order on large temporal or spatial scales compared to the otherwise random motions within the hosting system. Such ordered fields can be measured in the case of planets, stars, and galaxies, or inferred indirectly by the action of their dynamical influence, such as jets. Whether large scale fields are amplified in situ or a remnant from previous stages of an object's history is often debated for objects without a definitive magnetic activity cycle. Magnetic helicity, a measure of twist and linkage of magnetic field lines, is a unifying tool for understanding large scale field evolution for both mechanisms of origin. Its importance stems from its two basic properties: (1) magnetic helicity is typically better conserved than magnetic energy; and (2) the magnetic energy associated with a fixed amount of magnetic helicity is minimized when the system relaxes this helical structure to the largest scale available. H...

  14. Magnetic field calculation for 2.45 GHz permanent magnet high intensity ECR ion source development

    International Nuclear Information System (INIS)

    We push forward the development that aimed at increase in intensity of a proton beam in the RCNP cyclotron facility. We started development of a 2.45 GHz permanent magnet ECR ion source to generate a high intensity proton beam. The 2.45 GHz ECR ion source SILHI using superconducting solenoid coils was first developed at CEA/Saclay to produce a high intensity proton beam. They also developed a compact 2.45 GHz ECR ion source with a permanent magnet, but the proton intensity is limited to 70% of the first ion source. We have designed the 2.45 GHz permanent magnet ECR ion source by a magnetic field calculation OPERA-3D/TOSCA to achieve higher performance than SILHI. In order to generate a magnetic field (875 Gauss) satisfying an ECR condition, we arranged three rings-shaped permanent magnets to form a magnetic field distribution like the solenoid lens magnetic field of SILHI. We optimized a radial width and the thickness in the axial direction of the magnets, a position and thickness of the iron plate for correcting magnetic field distribution, a position and thickness of the iron for preventing electric discharge of the extraction electrode. I report the results of magnetic field calculations and the design of the ion source. (author)

  15. Magnetic-Field-Tunable Superconducting Rectifier

    Science.gov (United States)

    Sadleir, John E.

    2009-01-01

    Superconducting electronic components have been developed that provide current rectification that is tunable by design and with an externally applied magnetic field to the circuit component. The superconducting material used in the device is relatively free of pinning sites with its critical current determined by a geometric energy barrier to vortex entry. The ability of the vortices to move freely inside the device means this innovation does not suffer from magnetic hysteresis effects changing the state of the superconductor. The invention requires a superconductor geometry with opposite edges along the direction of current flow. In order for the critical current asymmetry effect to occur, the device must have different vortex nucleation conditions at opposite edges. Alternative embodiments producing the necessary conditions include edges being held at different temperatures, at different local magnetic fields, with different current-injection geometries, and structural differences between opposite edges causing changes in the size of the geometric energy barrier. An edge fabricated with indentations of the order of the coherence length will significantly lower the geometric energy barrier to vortex entry, meaning vortex passage across the device at lower currents causing resistive dissipation. The existing prototype is a two-terminal device consisting of a thin-film su - perconducting strip operating at a temperature below its superconducting transition temperature (Tc). Opposite ends of the strip are connected to electrical leads made of a higher Tc superconductor. The thin-film lithographic process provides an easy means to alter edge-structures, current-injection geo - metries, and magnetic-field conditions at the edges. The edge-field conditions can be altered by using local field(s) generated from dedicated higher Tc leads or even using the device s own higher Tc superconducting leads.

  16. Energy of Alfven waves generated during magnetic reconnection

    CERN Document Server

    Wang, L C; Ma, Z W; Zhang, X; Lee, L C

    2015-01-01

    A new method for the determination of the Alfven wave energy generated during magnetic reconnection is introduced and used to analyze the results from two-dimensional MHD simulations. It is found that the regions with strong Alfven wave perturbations almost coincide with that where both magnetic-field lines and flow-stream lines are bent, suggesting that this method is reliable for identifying Alfven waves. The magnetic energy during magnetic reconnection is mainly transformed into the thermal energy. The conversion rate to Alfven wave energy from the magnetic energy is strongly correlated to the magnetic reconnection rate. The maximum conversion rate at the time with the peak reconnection rate is found to be only about 4% for the cases with the plasma beta=0.01,0.1, and 1.0.

  17. Hypernuclear matter in strong magnetic field

    International Nuclear Information System (INIS)

    Compact stars with strong magnetic fields (magnetars) have been observationally determined to have surface magnetic fields of order of 1014–1015 G, the implied internal field strength being several orders larger. We study the equation of state and composition of dense hypernuclear matter in strong magnetic fields in a range expected in the interiors of magnetars. Within the non-linear Boguta–Bodmer–Walecka model we find that the magnetic field has sizable influence on the properties of matter for central magnetic field B?1017 G, in particular the matter properties become anisotropic. Moreover, for the central fields B?1018 G, the magnetized hypernuclear matter shows instability, which is signalled by the negative sign of the derivative of the pressure parallel to the field with respect to the density, and leads to vanishing parallel pressure at the critical value Bcr?1019 G. This limits the range of admissible homogeneously distributed fields in magnetars to fields below the critical value Bcr

  18. Recombination era magnetic fields from axion dark matter

    CERN Document Server

    Banik, Nilanjan

    2015-01-01

    We introduce a new mechanism for generating magnetic fields in the recombination era. This Harrison-like mechanism utilizes vorticity in baryons that is sourced through the Bose-Einstein condensate of axions via gravitational interactions. The magnetic fields generated are on the galactic scales $\\sim 10\\,{\\rm kpc}$ and have a magnitude of the order of $B\\sim10^{-23}\\,{\\rm G}$ today. The field has a greater magnitude than those generated from other mechanisms relying on second order perturbation theory, and is sufficient to provide a seed for battery mechanisms.

  19. Magnetic characteristics of magnetic compound fluid (MCF) under DC and AC magnetic fields

    International Nuclear Information System (INIS)

    We experimentally investigated the magnetic permeability of three intelligent fluids-magnetic fluid (MF), magneto-rheological fluid (MRF), and magnetic compound fluid (MCF)-under an AC magnetic field and their magnetization under a DC magnetic field. MCF is a magnetically responsive fluid composed of MF and MRF, as developed by Shimada in 2001. With the increase in the number of nm-sized magnetite or ?m-sized iron particles, the magnetic permeability of the fluids under an AC magnetic field and magnetization under a DC magnetic field increases. These results can be considered to depend on the particle cluster in a solvent. Therefore, we observed the formation of the clusters extracted from the fluids by using the technique proposed by Shimada. When the magnetic permeability under an AC magnetic field and magnetization under a DC magnetic field increase, the size of the clusters becomes smaller and the density of the clusters in the solvent becomes larger

  20. Apparatuses and methods for generating electric fields

    Science.gov (United States)

    Scott, Jill R; McJunkin, Timothy R; Tremblay, Paul L

    2013-08-06

    Apparatuses and methods relating to generating an electric field are disclosed. An electric field generator may include a semiconductive material configured in a physical shape substantially different from a shape of an electric field to be generated thereby. The electric field is generated when a voltage drop exists across the semiconductive material. A method for generating an electric field may include applying a voltage to a shaped semiconductive material to generate a complex, substantially nonlinear electric field. The shape of the complex, substantially nonlinear electric field may be configured for directing charged particles to a desired location. Other apparatuses and methods are disclosed.

  1. Analysis of brushless DC generator incorporating an axial field coil

    International Nuclear Information System (INIS)

    Highlights: ? Magnetic analysis and experiment of a three-phase field assisted BLDC generator. ? Confirm the accuracy of the predicted flux-linkage by 2-D FE analysis. ? Confirm the accuracy of the FE analysis results by coupling the FE and BE method. ? Control the output voltage to a desired level by control the amplitude of the If. ? Compatible with any application that requires variable speed operation. -- Abstract: This paper describes the magnetic analysis and experiment of a three-phase field assisted brushless DC (BLDC) generator. Unlike conventional BLDC generators, the permanent magnet is replaced with an assisted field winding. The stator and rotor are constructed with two dependent magnetically sets, in which each stator set includes nine salient poles with coil windings, and the rotor comprises of six salient poles. Other pole combinations also are possible. This construction is similar to a homopolar inductor alternator. The DC current in the assisted field winding produces axial flux which makes the rotor magnetically polarized at its ends. The magnetic field flows axially through the rotor shaft and closes through the stator teeth and the machine housing. To evaluate the generator performance, two types of analysis, namely the numerical technique and the experimental study have been utilized. In the numerical analysis, 2-D finite element (FE) analysis has been carried out using a MagNet CAD package (Infolytica Corporation Ltd.), to confirm the accuracy of the predicted flux-linkage characteristics, whereas in the experimental study, a prototype BLDC generator was constructed for verifying the actual performance. Furthermore, the evaluation method based on a hybrid numerical method coupling the finite element (FE) analysis and boundary element (BE) method, has been carried out to confirm the accuracy of the 2-D FE analysis simulation results. It provides not only confirmations of the investigation in results but also exact illustration for magnetic field distribution for this complex generator geometry.

  2. Analysis of brushless DC generator incorporating an axial field coil

    Energy Technology Data Exchange (ETDEWEB)

    Moradi, Hassan, E-mail: H_moradi@sbu.ac.i [Department of Electrical and Computer Engineering, Shahid Beheshti University, GC, Tehran (Iran, Islamic Republic of); Afjei, E. [Department of Electrical and Computer Engineering, Shahid Beheshti University, GC, Tehran (Iran, Islamic Republic of)

    2011-07-15

    Highlights: {yields} Magnetic analysis and experiment of a three-phase field assisted BLDC generator. {yields} Confirm the accuracy of the predicted flux-linkage by 2-D FE analysis. {yields} Confirm the accuracy of the FE analysis results by coupling the FE and BE method. {yields} Control the output voltage to a desired level by control the amplitude of the I{sub f}. {yields} Compatible with any application that requires variable speed operation. -- Abstract: This paper describes the magnetic analysis and experiment of a three-phase field assisted brushless DC (BLDC) generator. Unlike conventional BLDC generators, the permanent magnet is replaced with an assisted field winding. The stator and rotor are constructed with two dependent magnetically sets, in which each stator set includes nine salient poles with coil windings, and the rotor comprises of six salient poles. Other pole combinations also are possible. This construction is similar to a homopolar inductor alternator. The DC current in the assisted field winding produces axial flux which makes the rotor magnetically polarized at its ends. The magnetic field flows axially through the rotor shaft and closes through the stator teeth and the machine housing. To evaluate the generator performance, two types of analysis, namely the numerical technique and the experimental study have been utilized. In the numerical analysis, 2-D finite element (FE) analysis has been carried out using a MagNet CAD package (Infolytica Corporation Ltd.), to confirm the accuracy of the predicted flux-linkage characteristics, whereas in the experimental study, a prototype BLDC generator was constructed for verifying the actual performance. Furthermore, the evaluation method based on a hybrid numerical method coupling the finite element (FE) analysis and boundary element (BE) method, has been carried out to confirm the accuracy of the 2-D FE analysis simulation results. It provides not only confirmations of the investigation in results but also exact illustration for magnetic field distribution for this complex generator geometry.

  3. Analysis of magnetic field plasma interactions using microparticles as probes

    Science.gov (United States)

    Dropmann, Michael; Laufer, Rene; Herdrich, Georg; Matthews, Lorin S.; Hyde, Truell W.

    2015-08-01

    The interaction between a magnetic field and plasma close to a nonconductive surface is of interest for both science and technology. In space, crustal magnetic fields on celestial bodies without atmosphere can interact with the solar wind. In advanced technologies such as those used in fusion or spaceflight, magnetic fields can be used to either control a plasma or protect surfaces exposed to the high heat loads produced by plasma. In this paper, a method will be discussed for investigating magnetic field plasma interactions close to a nonconductive surface inside a Gaseous Electronics Conference reference cell employing dust particles as probes. To accomplish this, a magnet covered by a glass plate was exposed to a low power argon plasma. The magnetic field was strong enough to magnetize the electrons, while not directly impacting the dynamics of the ions or the dust particles used for diagnostics. In order to investigate the interaction of the plasma with the magnetic field and the nonconductive surface, micron-sized dust particles were introduced into the plasma and their trajectories were recorded with a high-speed camera. Based on the resulting particle trajectories, the accelerations of the dust particles were determined and acceleration maps over the field of view were generated which are representative of the forces acting on the particles. The results show that the magnetic field is responsible for the development of strong electric fields in the plasma, in both horizontal and vertical directions, leading to complex motion of the dust particles.

  4. Jupiter's magnetic field and magnetosphere

    Science.gov (United States)

    Smith, E. J.; Davis, L., Jr.; Jones, D. E.

    1976-01-01

    The Jovian magnetosphere is described on the basis of observations made by vector helium magnetometers aboard Pioneers 10 and 11. The results obtained from the two encounters are combined without emphasizing details peculiar to either of them. It is shown that near the planet, Jupiter's field is that of an eccentric tilted dipole with some admixture of higher-order terms; in this respect, it is similar to the earth's field, although it is 10 times as strong and has the opposite polarity. The magnetic field measurements reveal the existence of 3 distinct regions within the magnetosphere: outer magnetosphere, inner magnetosphere, and middle magnetosphere. The properties of these three regions are discussed, with observations being explained in terms of plausible physical causes. The observations are compared with several large-scale models of the entire magnetosphere. These observations do not favor models based on the continual outflow or convection of plasma from the Jovian magnetosphere in the vicinity of the equator.

  5. A magnetic minirobot with anchoring and drilling ability in tubular environments actuated by external magnetic fields

    Science.gov (United States)

    Choi, K.; Jeon, S. M.; Nam, J. K.; Jang, G. H.

    2015-05-01

    We propose a magnetic minirobot with anchoring and drilling ability (MMAD) controlled by an external magnetic field. The proposed MMAD can navigate through a tubular environment, such as human blood vessels, actuated by a magnetic gradient and uniform rotating magnetic field. It can also generate an anchoring motion, which stably holds the position of the MMAD under pulsatile flow, in order to drill and unclog obstructed blood vessels. The operating conditions of the MMAD were examined by investigating the magnetic torques, and the holding force of the MMAD was measured by a force sensing resistor. Finally, we performed various experiments in a tubular environment to verify the validity of the proposed MMAD.

  6. Study and Measurement of Glidarc Driven by Magnetic Field

    International Nuclear Information System (INIS)

    Non-thermal plasma at atmosphere was generated through glidarc discharge driven by magnetic field and observed by using a high speed charge coupled device (CCD) and photo multiplier tube (PMT). The arc diameter projecting in the direction of arc motion (front-viewed diameter) and the diameter projecting in the perpendicular direction of arc motion (side-viewed diameter) were measured. The effect of both the arc current and the magnetic field was analysed. The front-viewed diameter was compared with the side-viewed one. Simultaneously the electric-field intensity was measured directly and analysed by considering the effect of the external magnetic field and arc current.

  7. The formation of regular interarm magnetic fields in spiral galaxies

    CERN Document Server

    Moss, David; Krause, Marita; Beck, Rainer; Sokoloff, Dmitri

    2015-01-01

    Observations of several nearby galaxies of regular magnetic fields reveal magnetic arms situated between the material arms. The nature of these magnetic arms is a topic of active debate. Previously we found a hint that taking into account the effects of injections of small-scale magnetic fields generated, e.g., by turbulent dynamo action, into the large-scale galactic dynamo can result in magnetic arm formation. We now investigate the joint roles of an arm/interarm turbulent diffusivity contrast and injections of small-scale magnetic field on the formation of large-scale magnetic field ("magnetic arms") in the interarm region. We use the relatively simple "no-$z$" model for the galactic dynamo. This involves projection on to the galactic equatorial plane of the azimuthal and radial magnetic field components; the field component orthogonal to the galactic plane is estimated from the solenoidality condition. We find that addition of diffusivity gradients to the effect of magnetic field injections makes the magn...

  8. Magnetization reversal of ferromagnetic nanoparticles under inhomogeneous magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Joonyeon [Nano Device Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of)]. E-mail: presto@kist.re.kr; Yi, Hyunjung [Nano Device Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Cheol Koo, Hyun [Nano Device Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Mironov, V.L. [Institute for Physics of Microstructures RAS, 603950, GSP-105, Nizhny Novgorod (Russian Federation); Gribkov, B.A. [Institute for Physics of Microstructures RAS, 603950, GSP-105, Nizhny Novgorod (Russian Federation); Fraerman, A.A. [Institute for Physics of Microstructures RAS, 603950, GSP-105, Nizhny Novgorod (Russian Federation); Gusev, S.A. [Institute for Physics of Microstructures RAS, 603950, GSP-105, Nizhny Novgorod (Russian Federation); Vdovichev, S.N. [Institute for Physics of Microstructures RAS, 603950, GSP-105, Nizhny Novgorod (Russian Federation)

    2007-02-15

    We investigated remagnetization processes in ferromagnetic nanoparticles under inhomogeneous magnetic field induced by the tip of magnetic force microscope (MFM) in both theoretical and empirical ways. Systematic MFM observations were carried out on arrays of submicron-sized elliptical ferromagnetic particles of Co and FeCr with different sizes and periods. It clearly reveals the distribution of remanent magnetization and processes of local remagnetization of individual ferromagnetic particles. Modeling of remagnetization processes in ferromagnetic nanoparticles under magnetic field induced by MFM probe was performed on the base of Landau-Lifshitz-Gilbert equation for magnetization. MFM-induced inhomogeneous magnetic field is very effective to control the magnetic state of individual ferromagnetic nanoparticles as well as to create different distribution of magnetic field in array of ferromagnetic nanoparticles.

  9. Magnetization reversal of ferromagnetic nanoparticles under inhomogeneous magnetic field

    International Nuclear Information System (INIS)

    We investigated remagnetization processes in ferromagnetic nanoparticles under inhomogeneous magnetic field induced by the tip of magnetic force microscope (MFM) in both theoretical and empirical ways. Systematic MFM observations were carried out on arrays of submicron-sized elliptical ferromagnetic particles of Co and FeCr with different sizes and periods. It clearly reveals the distribution of remanent magnetization and processes of local remagnetization of individual ferromagnetic particles. Modeling of remagnetization processes in ferromagnetic nanoparticles under magnetic field induced by MFM probe was performed on the base of Landau-Lifshitz-Gilbert equation for magnetization. MFM-induced inhomogeneous magnetic field is very effective to control the magnetic state of individual ferromagnetic nanoparticles as well as to create different distribution of magnetic field in array of ferromagnetic nanoparticles

  10. Gravitational waves from the evolution of magnetic field after electroweak epoch

    OpenAIRE

    Tomalak, Oleksandr; Shtanov, Yuri

    2014-01-01

    It was recently demonstrated that the evolution of helical magnetic field in the primordial plasma at temperatures $T\\gtrsim10$ MeV is affected by the phenomenon of chiral quantum anomaly in the electroweak model, leading to a possibility of self-sustained existence of magnetic field and chiral asymmetry in the electronic distribution. This may serve as a mechanism for generating primordial magnetic field in the early universe. Violent magnetic-field generation may lead to p...

  11. Aligned electric and magnetic Weyl fields

    OpenAIRE

    Sáez, Joan Josep Ferrando Juan Antonio

    2003-01-01

    We analyze the spacetimes admitting a direction for which the relative electric and magnetic Weyl fields are aligned. We give an invariant characterization of these metrics and study the properties of its Debever null vectors. The directions 'observing' aligned electric and magnetic Weyl fields are obtained for every Petrov type. The results on the no existence of purely magnetic solutions are extended to the wider class having homothetic electric and magnetic Weyl fields.

  12. Cluster Magnetic Fields from Galactic Outflows

    OpenAIRE

    Donnert, J.; Dolag, K.; Lesch, H.; Müller, E

    2008-01-01

    We performed cosmological, magneto-hydrodynamical simulations to follow the evolution of magnetic fields in galaxy clusters, exploring the possibility that the origin of the magnetic seed fields are galactic outflows during the star-burst phase of galactic evolution. To do this we coupled a semi-analytical model for magnetized galactic winds as suggested by \\citet{2006MNRAS.370..319B} to our cosmological simulation. We find that the strength and structure of magnetic fields ...

  13. Polar plumes' orientation and the Sun's global magnetic field

    CERN Document Server

    de Patoul, Judith; Cameron, Robert

    2013-01-01

    We characterize the orientation of polar plumes as a tracer of the large-scale coronal magnetic field configuration. We monitor in particular the north and south magnetic pole locations and the magnetic opening during 2007-2008 and provide some understanding of the variations in these quantities. The polar plume orientation is determined by applying the Hough-wavelet transform to a series of EUV images and extracting the key Hough space parameters of the resulting maps. The same procedure is applied to the polar cap field inclination derived from extrapolating magnetograms generated by a surface flux transport model. We observe that the position where the magnetic field is radial (the Sun's magnetic poles) reflects the global organization of magnetic field on the solar surface, and we suggest that this opens the possibility of both detecting flux emergence anywhere on the solar surface (including the far side) and better constraining the reorganization of the corona after flux emergence.

  14. The origin of large scale magnetic fields

    CERN Document Server

    Subramanian, K

    1996-01-01

    Magnetic fields correlated on several kiloparsec scales are seen in spiral galaxies. Their origin could be due to the winding up of a primordial cosmological field or due to amplification of a small seed field by a turbulent galactic dynamo. Both options have difficulties: There is no known battery mechanism for producing the required primordial field. Equally the turbulent dynamo may self destruct before being able to produce the large scale field, due to excess generation of small scale power. The current status of these difficulties is discussed. The resolution could depend on the nature of the saturated field produced by the small scale dynamo. We argue that the small scale fields do not fill most of the volume of the fluid and instead concentrate into intermittent ropes, with their peak value of order equipartition fields, and radii much smaller than their lengths. In this case these fields neither drain significant energy from the turbulence nor convert eddy motion of the turbulence on the outer scale t...

  15. Control of Permanent Magnet Synchronous Generator for large wind turbines

    DEFF Research Database (Denmark)

    Busca, Cristian; Stan, Ana-Irina; Stanciu, Tiberiu; Stroe, Daniel Ioan

    2010-01-01

    Direct Torque Control (DTC) and Field Oriented Control (FOC) are the most dominant control strategies used in generators for wind turbines. In this paper both control methods were implemented on a Permanent Magnet Synchronous Generator (PMSG). The variable speed wind turbine with full scale power converter topology was chosen for design. Parameters from a 2 MW wind turbine were used for system modeling. All the components of the wind turbine system (WTS), except the DC-link and the grid site con...

  16. Black holes and magnetic fields.

    Czech Academy of Sciences Publication Activity Database

    Bi?ák, J.; Karas, Vladimír; Ledvinka, T.

    Cambridge : Cambridge University Press, 2007 - (Karas, V.; Matt, G.), s. 139-144 ISBN 978-0-521-86347-6. ISSN 1743-9213. - (Proceedings of the International Astronomical Union. S238). [Symposium of the International Astronomical Union /238./. Praha (CZ), 21.08.2006-25.08.2006] R&D Projects: GA ?R GA202/06/0041; GA MŠk(CZ) LC06014 Institutional research plan: CEZ:AV0Z10030501 Keywords : black hole physics * magnetic fields Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics

  17. Origin of the magnetic fields in the giant planets

    Science.gov (United States)

    Smoluchowski, R.

    1979-01-01

    The paper discusses origin of the magnetic fields in the giant planets. Recent data on the generation of these fields provide conclusions on giant planets; the Jovian magnetic field can be of primordial origin or generated by a thermally driven dynamo, and the expected Saturnian field can be accounted for thermally or by a precessionally driven dynamo. The presence of a 0.1 gauss field on Uranus presents a problem because the so far unobserved thermal flux and convection may be too low, and if such a dynamo were to operate then the field should show seasonal variations. A conductive shell on Neptune similar to that on Uranus appears to be much thinner, but it is likely that Neptune has a magnetic field which is too weak to lead to observable electromagnetic variations.

  18. Magnetic Fields from the Electroweak Phase Transition

    OpenAIRE

    Tornkvist, Ola

    1998-01-01

    I review some of the mechanisms through which primordial magnetic fields may be created in the electroweak phase transition. I show that no magnetic fields are produced initially from two-bubble collisions in a first-order transition. The initial field produced in a three-bubble collision is computed. The evolution of fields at later times is discussed.

  19. Magnetic field ripple measurement of the J-PARC MR main magnets

    International Nuclear Information System (INIS)

    Magnetic field ripple has been measured for the main magnets of the J-PARC main ring. The power supplies generate the current ripple of the order of 10-5 - 10-4 for the frequencies of 150 Hz and the harmonics. Standing waves have been observed for the ripple distribution in the magnet chain. The propagation has been described with the transmission line parameters of the inductance and resistance of the magnet and the capacitance of the cable. Most of the ripples of 150 Hz and the harmonics have been generated in the common mode and the standing wave distribution was anti-symmetrical. Magnetic field ripple by the common mode current ripple has been cancelled with the symmetric cabling. The field ripple was further suppressed with resistors connected in parallel with the magnet coils. The measured ripple distribution was in a good agreement with the calculation of LTspice. (author)

  20. The levitation characteristics of the magnetic substances using trapped HTS bulk annuli with various magnetic field distributions

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S.B., E-mail: kim@ec.okayama-u.ac.jp [Graduate School of Natural Science and Technology, Okayama University, 3-1-1, Tsushima-Naka, Kita-ku, Okayama 700-8530 (Japan); Ikegami, T.; Matsunaga, J.; Fujii, Y. [Graduate School of Natural Science and Technology, Okayama University, 3-1-1, Tsushima-Naka, Kita-ku, Okayama 700-8530 (Japan); Onodera, H. [Japan Science and Technology Agency–Core Research for Evolutional Science and Technology (JST–CREST), Tokyo 102-0076 (Japan)

    2013-11-15

    Highlights: •The spherical solenoid magnet can make a various magnetic field distributions. •We generated a large magnetic gradient at inner space of HTS bulks. •The levitation height of samples was improved by the reapplied field method. •The levitation height depends on the variation rate of magnetic field gradient. -- Abstract: We have been investigating the levitation system without any mechanical contact which is composed of a field-cooled ring-shaped high temperature superconducting (HTS) bulks [1]. In this proposed levitation system, the trapped magnetic field distributions of stacked HTS bulk are very important. In this paper, the spherical solenoid magnet composed of seven solenoid coils with different inner and outer diameters was designed and fabricated as a new magnetic source. The fabricated spherical solenoid magnet can easily make a homogeneous and various magnetic field distributions in inner space of stacked HTS bulk annuli by controlling the emerging currents of each coil. By using this spherical solenoid magnet, we tried to make a large magnetic field gradient in inner space of HTS bulk annuli, and it is very important on the levitation of magnetic substances. In order to improve the levitation properties of magnetic substances with various sizes, the external fields were reapplied to the initially trapped HTS bulk magnets. We could generate a large magnetic field gradient along the axial direction in inner space of HTS bulk annuli, and obtain the improved levitation height of samples by the proposed reapplied field method.

  1. Full 180° Magnetization Reversal with Electric Fields

    Science.gov (United States)

    Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.

    2014-01-01

    Achieving 180° magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180° magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90° magnetization rotations, thereby leading to full 180° magnetization reversals. PMID:25512070

  2. Model for charged dust expansion across a magnetic field

    International Nuclear Information System (INIS)

    Plasma fluctuations arise in the boundary region between charged dust clouds and background plasmas. A self-consistent computational model is developed to study expansion of a charged dust cloud across a magnetic field, creation of the inhomogeneous boundary layer and associated processes. The charging of the dust particulates produces a boundary layer and associated ambipolar electric field. This ambipolar field provides a source for low frequency dust acoustic waves in unmagnetized plasmas. A background magnetic field if sufficiently strong, may impact the dust acoustic wave evolution and dust density structures due to E×B and diamagnetic current generation. The dust acoustic density fluctuation generation across a strong magnetic field (?pe/?ce?1) may be suppressed as compared to an unmagnetized dusty plasma, which will be discussed. Fluctuations generated at longer timescales propagating along the dust boundary layer will also be investigated in the lower hybrid and dust lower hybrid frequency range. Applications to space and laboratory plasmas are discussed

  3. Model for charged dust expansion across a magnetic field

    Science.gov (United States)

    Fu, H.; Scales, W. A.

    2013-07-01

    Plasma fluctuations arise in the boundary region between charged dust clouds and background plasmas. A self-consistent computational model is developed to study expansion of a charged dust cloud across a magnetic field, creation of the inhomogeneous boundary layer and associated processes. The charging of the dust particulates produces a boundary layer and associated ambipolar electric field. This ambipolar field provides a source for low frequency dust acoustic waves in unmagnetized plasmas. A background magnetic field if sufficiently strong, may impact the dust acoustic wave evolution and dust density structures due to E ×B and diamagnetic current generation. The dust acoustic density fluctuation generation across a strong magnetic field (?pe/?ce?1) may be suppressed as compared to an unmagnetized dusty plasma, which will be discussed. Fluctuations generated at longer timescales propagating along the dust boundary layer will also be investigated in the lower hybrid and dust lower hybrid frequency range. Applications to space and laboratory plasmas are discussed.

  4. Spin dephasing in a magnetic dipole field

    Science.gov (United States)

    Ziener, C. H.; Kampf, T.; Reents, G.; Schlemmer, H.-P.; Bauer, W. R.

    2012-05-01

    Transverse relaxation by dephasing in an inhomogeneous field is a general mechanism in physics, for example, in semiconductor physics, muon spectroscopy, or nuclear magnetic resonance. In magnetic resonance imaging the transverse relaxation provides information on the properties of several biological tissues. Since the dipole field is the most important part of the multipole expansion of the local inhomogeneous field, dephasing in a dipole field is highly important in relaxation theory. However, there have been no analytical solutions which describe the dephasing in a magnetic dipole field. In this work we give a complete analytical solution for the dephasing in a magnetic dipole field which is valid over the whole dynamic range.

  5. Pulse field magnetization of a ring-shaped bulk superconductor

    International Nuclear Information System (INIS)

    We have studied the pulse field magnetization of a YBCO bulk superconducting ring. In the experiments a 6 ms pulse magnetic field was applied to a ring-shaped YBCO superconductor with a 46 mm outer diameter, 16 mm inner diameter and 15 mm height, which was cooled by liquid nitrogen (77 K). Then, trapped magnetic field profiles were measured with a Hall sensor. For example, a single 1.2 T pulse field generated a hollow profile of the trapped magnetic field. In addition, the finite element method was used to solve the coupled problem of thermal and electromagnetic fields, where the power-n model was adopted for the E-J (E is the electric field and J is the current density) relation in the superconductor. A comparison between the results of experiment and analysis has shown that n=6 gave good agreement between them. We have also discussed the current density distribution, temperature distribution, etc. (author)

  6. Constraining Primordial Magnetic Fields with Future Cosmic Shear Surveys

    CERN Document Server

    Fedeli, C

    2012-01-01

    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. We use the predicted ...

  7. Radiation from Relativistic Shocks with Turbulent Magnetic Fields

    Science.gov (United States)

    Nishkawa, K.; Medvedev, M.; Zhang, B.; Hardee, P.; Niemiec, J.; Mizuno, A.; Nordlund, A.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Oka, M.; Fishman, J.

    2009-01-01

    Recent PIC simulations of relativistic electron-positron (electron-ion) jets injected into a stationary medium show that particle acceleration occurs at shocked region. The simulation results show that the Weibel instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields. These magnetic fields contribute to the electron's transverse deflection behind the shock. The "jitter" radiation from deflected electrons in turbulent magnetic fields has different properties than synchrotron radiation which is calculated in a uniform magnetic field. This jitter radiation may be important to understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets, and supernova remnants. New recent calculation of spectra with various different Lorentz factors of jets (two electrons) and initial magnetic fields. New spectra based on small simulations will be presented.

  8. Antimagnets: controlling magnetic fields with superconductor-metamaterial hybrids

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez, Alvaro; Navau, Carles; Prat-Camps, Jordi; Chen Duxing, E-mail: alvar.sanchez@uab.cat [Grup d' Electromagnetisme, Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona, Catalonia (Spain)

    2011-09-15

    Magnetism is very important in various areas of science and technology, ranging from magnetic recording through energy generation to trapping cold atoms. Physicists have managed to master magnetism-to create and manipulate magnetic fields-almost at will. Surprisingly, there is at least one property that has been elusive until now: how to 'switch off' the magnetic interaction of a magnetic material with existing magnetic fields without modifying them. Here we introduce the antimagnet, a design that conceals the magnetic response of a given volume from its exterior, without altering the external magnetic fields, in some respects analogous to recent theoretical proposals for cloaking electromagnetic waves with metamaterials. However, unlike these devices, which require extreme material properties, our device is feasible and needs only two kinds of available materials: superconductors and isotropic magnetic materials. Antimagnets may have applications in magnetic-based medical techniques such as magnetic resonance imaging or in reducing the magnetic signature of vessels or planes.

  9. Deformation of Water by a Magnetic Field

    Science.gov (United States)

    Chen, Zijun; Dahlberg, E. Dan

    2011-01-01

    After the discovery that superconducting magnets could levitate diamagnetic objects, researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields, which was given the name "The Moses Effect." Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary…

  10. Exploring Magnetic Fields with a Compass

    Science.gov (United States)

    Lunk, Brandon; Beichner, Robert

    2011-01-01

    A compass is an excellent classroom tool for the exploration of magnetic fields. Any student can tell you that a compass is used to determine which direction is north, but when paired with some basic trigonometry, the compass can be used to actually measure the strength of the magnetic field due to a nearby magnet or current-carrying wire. In this…

  11. Is the mystery of cosmic magnetic fields solved?

    OpenAIRE

    Durrer, Ruth

    2006-01-01

    Observing astrophysical magnetic fields is difficult. Nonetheless, fields of surprisingly consistent amplitudes on the order of microgauss have been discovered in many galaxies and clusters of galaxies. So far, the generation of these fields has remained a mystery. For a long time, scientists tried to conceive of a mechanism by which tiny primordial fields would be created in the early universe. Later, during gravitational collapse, such fields could be amplified--for example, by means of a d...

  12. Magnetic fields in the Venus ionosphere

    International Nuclear Information System (INIS)

    Qualitative analysis of non-stationary plasma and magnetic field convection in the daytime Venus atmosphere and comparison of various hypothesis of large-scale field and magnetic force line cords in ionosphere on the base of plasma convection picture are conducted. It is shown that the observed large-scale field or the magnetic belt in the Venus daytime inosphere appears to be a result of evolution of solar wind magnetic field pressed through ionosphere; the magnetic field upper boundary runs in the vicinity of the phtochemical equilibrium area upper boundary. With regard to plasma convection and results of investigation into the venus ionopause stability, the destruction of interplanetary magnetic field pressed through ionosphere under high dynamic solar wind pressure appears to be the most probable source of magnetic cords in the lower ionosphere of Venus

  13. Superconducting strip in an oblique magnetic field

    CERN Document Server

    Mikitik, G P; Indenbom, M V

    2004-01-01

    As an example for a seemingly simple but actually intricate problem, the Bean critical state is studied in a superconducting strip of finite thickness d and width 2w >> d placed in an oblique magnetic field. The analytical solution is obtained to leading order in the small parameter d/w. The critical state depends on how the applied magnetic field is switched on, e.g., at constant tilt angle, or first the perpendicular and then the parallel field component. For these two basic scenarios the distributions of current density and magnetic field are obtained in the critical states. In particular, we find the shapes of the flux-free core and of the lines separating regions with opposite direction of the critical currents, the detailed magnetic field lines (along the vortex lines), and both components of the magnetic moment. The component of the magnetic moment parallel to the strip plane is a nonmonotonic function of the applied magnetic field.

  14. Wide field polarimetry and cosmic magnetism

    OpenAIRE

    Beck, Rainer

    2009-01-01

    The SKA and its precursors will open a new era in the observation of cosmic magnetic fields and help to understand their origin. In the SKADS polarization simulation project, maps of polarized intensity and RM of the Milky Way, galaxies and halos of galaxy clusters were constructed, and the possibilities to measure the evolution of magnetic fields in these objects were investigated. The SKA will map interstellar magnetic fields in nearby galaxies and intracluster fields in n...

  15. Atoms in extreme strong magnetic fields

    International Nuclear Information System (INIS)

    The discovery of extremly strong magnetic fields up to 109T in compact cosmic objects is responsible for a new chapter in quantum mechanics: ''Matter in extremly strong magnetic fields''. In the presence of such fields the Coulomb-binding-force is dominated by the Lorentz-force, the atoms are strongly deformed to nearly one-dimensional objects, and all properties are anisotropic. The dramatic influence of the magnetic field is demonstrated for the hydrogen atom. (orig.)

  16. The Origin of Cosmic Magnetic Fields

    OpenAIRE

    Tornkvist, Ola

    2000-01-01

    In this talk, I review a number of particle-physics models that lead to the creation of magnetic fields in the early universe and address the complex problem of evolving such primordial magnetic fields into the fields observed today. Implications for future observations of the Cosmic Microwave Background (CMB) are discussed. Focussing on first-order phase transitions in the early universe, I describe how magnetic fields arise in the collision of expanding true-vacuum bubbles...

  17. The Origin of Magnetic Fields in Galaxies

    OpenAIRE

    de Souza, Rafael S; R. Opher

    2009-01-01

    Microgauss magnetic fields are observed in all galaxies at low and high redshifts. The origin of these intense magnetic fields is a challenging question in astrophysics. We show here that the natural plasma fluctuations in the primordial universe (assumed to be random), predicted by the Fluctuation-Dissipation-Theorem, predicts $\\sim 0.034 \\mu G$ fields over $\\sim 0.3$ kpc regions in galaxies. If the dipole magnetic fields predicted by the Fluctuation-Dissipation-Theore...

  18. Dynamic shielding of the magnetic fields

    OpenAIRE

    RAU, M.; COSTANDACHE, D.; BALTAG, O.; IFTEMIE, A.; Rau, I.

    2010-01-01

    The paper presents a comparative study of the methods used to control and compensate the direct and alternative magnetic fields. Two frequently used methods in the electromagnetic compatibility of the complex biomagnetism installations were analyzed. The two methods refer to the use of inductive magnetic field sensors (only for alternative fields) and of fluxgate magnetometers as active transducers which measures both the direct and alternative components of the magnetic field. The applica...

  19. Electrolytic tiltmeters inside magnetic fields: Some observations

    International Nuclear Information System (INIS)

    We present observations of the electrolytic clinometers behaviour inside magnetic field environments introducing phenomenological expressions to account for the measured output voltage variations as functions of field gradients and field strengths

  20. Magnetic flux generation and transport in cool stars

    CERN Document Server

    I??k, Emre; Schüssler, Manfred

    2011-01-01

    The Sun and other cool stars harbouring outer convection zones manifest magnetic activity in their atmospheres. The connection between this activity and the properties of a deep-seated dynamo generating the magnetic flux is not well understood. By employing physical models, we study the spatial and temporal characteristics of the observable surface field for various stellar parameters. We combine models for magnetic flux generation, buoyancy instability, and transport, which encompass the entire convection zone. The model components are: (1) a thin-layer alpha-Omega dynamo at the base of the convection zone; (2) buoyancy instabilities and the rise of flux tubes through the convection zone in 3D, which provides a physically consistent determination of emergence latitudes and tilt angles; and (3) horizontal flux transport at the surface. For solar-type stars and rotation periods longer than about 10 days, the latitudinal dynamo waves generated by the deep-seated alpha-Omega dynamo are faithfully reflected by th...

  1. Spin transfer torque generated magnetic droplet solitons (invited)

    Energy Technology Data Exchange (ETDEWEB)

    Chung, S. [Materials Physics, School of ICT, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Mohseni, S. M. [Materials Physics, School of ICT, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); NanOsc AB, Electrum 205, 164 40 Kista (Sweden); Department of Physics, Shahid Beheshti University, G.C., Evin, Tehran 19839 (Iran, Islamic Republic of); Sani, S. R. [Materials Physics, School of ICT, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); NanOsc AB, Electrum 205, 164 40 Kista (Sweden); Iacocca, E.; Dumas, R. K.; Pogoryelov, Ye. [Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Anh Nguyen, T. N. [Materials Physics, School of ICT, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Laboratory for Nanotechnology (LNT), Vietnam National University - Ho Chi Minh City (VNU-HCM), Ho Chi Minh City (Viet Nam); Muduli, P. K. [Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016 (India); Eklund, A. [Devices and Circuits, School of ICT, KTH Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Hoefer, M. [Department of Mathematics, North Carolina State University, Raleigh, North Carolina 27695 (United States); Åkerman, J., E-mail: johan.akerman@physics.gu.se [Materials Physics, School of ICT, Royal Institute of Technology, Electrum 229, 164 40 Kista (Sweden); Department of Physics, University of Gothenburg, 412 96 Gothenburg (Sweden); NanOsc AB, Electrum 205, 164 40 Kista (Sweden)

    2014-05-07

    We present recent experimental and numerical advancements in the understanding of spin transfer torque generated magnetic droplet solitons. The experimental work focuses on nano-contact spin torque oscillators (NC-STOs) based on orthogonal (pseudo) spin valves where the Co fixed layer has an easy-plane anisotropy, and the [Co/Ni] free layer has a strong perpendicular magnetic anisotropy. The NC-STO resistance and microwave signal generation are measured simultaneously as a function of drive current and applied perpendicular magnetic field. Both exhibit dramatic transitions at a certain current dependent critical field value, where the microwave frequency drops 10 GHz, modulation sidebands appear, and the resistance exhibits a jump, while the magnetoresistance changes sign. We interpret these observations as the nucleation of a magnetic droplet soliton with a large fraction of its magnetization processing with an angle greater than 90°, i.e., around a direction opposite that of the applied field. This interpretation is corroborated by numerical simulations. When the field is further increased, we find that the droplet eventually collapses under the pressure from the Zeeman energy.

  2. Dynamic shielding of the magnetic fields

    Directory of Open Access Journals (Sweden)

    RAU, M.

    2010-11-01

    Full Text Available The paper presents a comparative study of the methods used to control and compensate the direct and alternative magnetic fields. Two frequently used methods in the electromagnetic compatibility of the complex biomagnetism installations were analyzed. The two methods refer to the use of inductive magnetic field sensors (only for alternative fields and of fluxgate magnetometers as active transducers which measures both the direct and alternative components of the magnetic field. The applications of the dynamic control of the magnetic field are: control of the magnetic field of the military ships, control of parasite magnetic field produced by power transformers and the electrical networks, protection of the mass spectrometers, electronic microscopes, SQUID and optical pumping magnetometers for applications in biomagnetism.

  3. Next generation IR magnets for hadron colliders

    CERN Document Server

    Gupta, R; Cozzolino, J P; Escallier, J; Ganetis, G; Harrison, M; Wanderer, P J; 10.1109/TASC.2003.812666

    2003-01-01

    Brookhaven National Laboratory (BNL) is developing "React & Wind" designs and technology for building long high field accelerator magnets. This paper presents the R&D program for interaction region (IR) magnets made with "Rutherford" cable for the luminosity upgrade of the Large Hadron Collider (LHC). This paper will introduce a few new end design concepts that make the bend radius of the cable in the end independent of the coil aperture. These designs are suitable for building magnets with "React & Wind" technology. (6 refs).

  4. Sudden flux change studies in high field superconducting accelerator magnets

    Energy Technology Data Exchange (ETDEWEB)

    Feher, S.; Bordini, B.; Carcagno, R.; Makulski, A.; Orris, D.F.; Pischalnikov, Y.M.; Sylvester, C.; Tartaglia, M.; Tompkins, J.C.; Zlobin, A.V.; /Fermilab

    2004-10-01

    As part of the High Field Magnet Program at Fermilab many magnets have been tested which utilize multi strand Rutherford type cable made of state-of-the art Nb{sub 3}Sn strands. During these magnet tests we observed sudden flux changes by monitoring coil voltages and the magnetic field close to the magnets. These flux changes might be linked to magnet instabilities. The voltage spike signals were correlated with quench antenna signals, a strong indication that these are magnet phenomena. With a new high resolution voltage spike detection system, we were able to observe the detailed structure of the spikes. Two fundamentally different signal shapes were distinguished, most likely generated by different mechanisms.

  5. Quarks and gluons in a magnetic field

    CERN Document Server

    Watson, Peter

    2013-01-01

    The quark gap equation under the rainbow truncation, with two versions of a phenomenological one-gluon exchange interaction and in the presence of a uniform magnetic field is considered. It is argued that in order to describe the quark condensate in the limit of vanishing magnetic fields, one must sum over the Landau levels. The resulting chiral quark condensate rises quadratically for small magnetic fields and linearly for large fields, in qualitative agreement with various recent lattice results. It is observed that when discussing quarks, the magnitude of the magnetic field must be considered relative to the scale of the strong interaction.

  6. Cosmological magnetic fields as string dynamo seeds and axion fields in torsioned spacetime

    International Nuclear Information System (INIS)

    In this paper two examples of the generation cosmological magnetic fields (CMF) are given. The first is the string dynamo seed cosmological magnetic field estimated as Bseed?10-24 Gauss from a static spin polarised cylinder in Einstein-Cartan-Maxwell spacetime. The string dynamo seeds from a static spin polarised cylinder is given by B??2R2 where ? is the spin-torsion density while R is the string radius. The B-field value above is able to seed galactic dynamo. In the BBN the magnetic fields around 1012 Gauss give rise to a string radius as small as 1017lP where lP is the Planck length. The second is the CMF from axionic torsion field which is given by Bseed?10-27 Gauss which is stronger than the primordial magnetic field BBICEP2?10-30 Gauss from the BICEP2 recent experiment on primordial gravitational waves and cosmological inflation to axionic torsion. The interaction Lagrangean between axionic torsion scalar ? and magnetic fields used in this last example is given by f2(?)F??F??. A similar lagrangean has been used by K. Bamba et al. [JCAP 10 (2012) 058] so generate magnetic fields without dynamo action. Since axionic torsion can be associated with axionic domain walls both examples discussed here could be consider as topological defects examples of the generation of primordial magnetic fields in universes endowed with spacetime torsion

  7. Nonlinear physics of twisted magnetic field lines

    International Nuclear Information System (INIS)

    Twisted magnetic field lines appear commonly in many different plasma systems, such as magnetic ropes created through interactions between the magnetosphere and the solar wind, magnetic clouds in the solar wind, solar corona, galactic jets, accretion discs, as well as fusion plasma devices. In this paper, we study the topological characterization of twisted magnetic fields, nonlinear effect induced by the Lorentz back reaction, length-scale bounds, and statistical distributions. (author)

  8. Dynamics of Chromospheric Upflows and Underlying Magnetic Fields

    CERN Document Server

    Yurchyshyn, Vasyl; Goode, Phil

    2013-01-01

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

  9. The role of multipolar magnetic fields in pulsar magnetospheres

    CERN Document Server

    Asséo, E; Asseo, Estelle; Khechinashvili, David

    2002-01-01

    We explore the role of complex multipolar magnetic fields in determining physical processes near the surface of rotation powered pulsars. We model the actual magnetic field as the sum of global dipolar and star-centered multipolar fields. In configurations involving axially symmetric and uniform multipolar fields, 'neutral points' and 'neutral lines' exist close to the stellar surface. Also, the curvature radii of magnetic field lines near the stellar surface can never be smaller than the stellar radius, even for very high order multipoles. Consequently, such configurations are unable to provide an efficient pair creation process above pulsar polar caps, necessary for plasma mechanisms of generation of pulsar radiation. In configurations involving axially symmetric and non-uniform multipoles, the periphery of the pulsar polar cap becomes fragmented into symmetrically distributed narrow sub-regions where curvature radii of complex magnetic field lines are less than the radius of the star. The pair production p...

  10. Effects of solar magnetic field on cosmic rays

    International Nuclear Information System (INIS)

    Aspects of the problem of galactic cosmic ray propagation, including inversion of the solar total magnetic field and an analysis of data related to the heliomagnetic cycle are discussed. It is noted that the global structure of the solar magnetic field results in an additional flux of galactic cosmic rays generated by curvature and gradient drifts. An analysis of heliomagnetic cycle data shows that the latitudinal gradient results in a N-S asymmetry, with the amplitude of the effect growing with depth in the atmosphere. The inversion of the solar total magnetic field, drift effects, and other space distributions are found to contribute to a 22-year cycle of solar activity

  11. Magnetic fields in young supernova remnants

    Science.gov (United States)

    Lou, Yu-Qing

    1994-06-01

    Magnetic field strengths in several young Type I supernova remnants (SNRs), such as those associated with SN 1572, 1604, 1006, have been previously inferred from radio synchrotron observations to be of the order of approximately 10-4 - 10-3 G, which greatly exceeds the typical magnetic field strength of several microgauss in ambient interstellar media (ISM). Existing radio polarization studies indicate that projected large-scale magnetic fields tend to orient in the radial direction with several percent in excess within shells of these SNRs. We propose in this Letter that magnetic fields in these young SNRs could mainly originate from magnetized envelopes or magnetospheres of their presupernova progenitors, presumably magnetic white dwarfs, and that magnetic fields entrained in stellar ejecta roughly scale as approximately r-1. The inferred excess of radial alignment for magnetic fields in these young SNRs could result from the Rayleigh-Taylor instability and/or the presence of large-scale random helices of magnetic field lines with their axes meandering through the SNR shell. Molecular clouds and clumps of stellar materials surrounding the presupernova progenitor could also produce radial magnetic fields from transverse fields as the SNR expands into the ISM.

  12. Magnetic nanoparticle sensing: decoupling the magnetization from the excitation field

    OpenAIRE

    Reeves, Daniel B; Weaver, John B

    2014-01-01

    Remote sensing of magnetic nanoparticles has exciting applications for magnetic nanoparticle hyperthermia and molecular detection. We introduce, simulate, and experimentally demonstrate an innovation---a sensing coil that is geometrically decoupled from the excitation field---for magnetic nanoparticle spectroscopy that increases the flexibility and capabilities of remote detection. The decoupling enhances the sensitivity absolutely; to small amounts of nanoparticles, and rel...

  13. Nonlinear energy dissipation of magnetic nanoparticles in oscillating magnetic fields

    Science.gov (United States)

    Soto-Aquino, D.; Rinaldi, C.

    2015-11-01

    The heating of magnetic nanoparticle suspensions subjected to alternating magnetic fields enables a variety of emerging applications such as magnetic fluid hyperthermia and triggered drug release. Rosensweig (2002) [25] obtained a model for the heat dissipation rate of a collection of non-interacting particles. However, the assumptions made in this analysis make it rigorously valid only in the limit of small applied magnetic field amplitude and frequency (i.e., values of the Langevin parameter that are much less than unity and frequencies below the inverse relaxation time). In this contribution we approach the problem from an alternative point of view by solving the phenomenological magnetization relaxation equation exactly for the case of arbitrary magnetic field amplitude and frequency and by solving a more accurate magnetization relaxation equation numerically. We also use rotational Brownian dynamics simulations of non-interacting magnetic nanoparticles subjected to an alternating magnetic field to estimate the rate of energy dissipation and compare the results of the phenomenological theories to the particle-scale simulations. The results are summarized in terms of a normalized energy dissipation rate and show that Rosensweig's expression provides an upper bound on the energy dissipation rate achieved at high field frequency and amplitude. Estimates of the predicted dependence of energy dissipation rate, quantified as specific absorption rate (SAR), on magnetic field amplitude and frequency, and particle core and hydrodynamic diameter, are also given.

  14. Effects of external axial magnetic field on fast electron propagation

    International Nuclear Information System (INIS)

    A scheme employing an external axial magnetic field is proposed to diagnose the intrinsic divergence of laser-generated fast electron beams, and this is studied numerically with hybrid simulations. The maximum beam radius of fast electrons increases with the initial divergence and decreases with the amplitude of the axial magnetic field. It is indicated that the intrinsic divergence of fast electrons can be inferred from measurements of the beam radius at different depth under the axial field. The proposed scheme here may be useful for future fast ignition experiments and in other applications of laser-generated fast electron beams.

  15. Idea Generation in Highly Institutionalized Fields

    DEFF Research Database (Denmark)

    Agoguè, Marine; Boxenbaum, Eva

    2014-01-01

    The early phase of innovation processes in highly institutionalized fields relies on the capabilities of actors to generate new ideas that break with the field frame. Informed by a dominant logic, a field frame shapes collective cognition and can thus prevent the generation of new ideas and block innovation. An important question facing innovation research is thus how actors can generate ideas that break with the field frame in highly institutionalized fields? To answer this question, we draw on...

  16. Constraints on Primordial Magnetic Fields from Inflation

    CERN Document Server

    Green, Daniel

    2015-01-01

    We present generic bounds on magnetic fields produced from cosmic inflation. By investigating field bounds on the vector potential, we constrain both the quantum mechanical production of magnetic fields and their classical growth in a model independent way. For classical growth, we show that only if the reheating temperature is as low as T_{reh} <~ 10^2 MeV can magnetic fields of 10^{-15} G be produced on Mpc scales in the present universe. For purely quantum mechanical scenarios, even stronger constraints are derived. Our bounds on classical and quantum mechanical scenarios apply to generic theories of inflationary magnetogenesis with a two-derivative time kinetic term for the vector potential. In both cases, the magnetic field strength is limited by the gravitational back-reaction of the electric fields that are produced simultaneously. As an example of quantum mechanical scenarios, we construct vector field theories whose time diffeomorphisms are spontaneously broken, and explore magnetic field generati...

  17. On the origin of cosmic magnetic fields

    International Nuclear Information System (INIS)

    We review the extensive and controversial literature concerning how the cosmic magnetic fields pervading nearly all galaxies and clusters of galaxies actually got started. Some observational evidence supports a hypothesis that the field is already moderately strong at the beginning of the life of a galaxy and its disc. One argument involves the chemical abundance of the light elements Be and B, while a second one is based on the detection of strong magnetic fields in very young high red shift galaxies. Since this problem of initial amplification of cosmic magnetic fields involves important plasma problems it is obvious that one must know the plasma in which the amplification occurs. Most of this review is devoted to this basic problem and for this it is necessary to devote ourselves to reviewing studies that take place in environments in which the plasma properties are most clearly understood. For this reason the authors have chosen to restrict themselves almost completely to studies of dynamos in our Galaxy. It is true that one can get a much better idea of the grand scope of galactic fields in extragalactic systems. However, most mature galaxies share the same dilemma as ours of overcoming important plasma problems. Since the authors are both trained in plasma physics we may be biased in pursuing this approach, but we feel it is justified by the above argument. In addition we feel we can produce a better review by staying close to that which we know best. In addition we have chosen not to consider the saturation problem of the galactic magnetic field since if the original dynamo amplification fails the saturation question does not arise. It is generally accepted that seed fields, whose strength is of order 10-20 G, easily spring up in the era preceding galaxy formation. Several mechanisms have been proposed to amplify these seed magnetic fields to a coherent structure with the microgauss strengths of the currently observed galactic magnetic fields. The standard and most popular mechanism is the ?-? mean field dynamo theory developed by a number of people in the late sixties. This theory and its application to galactic magnetic fields is discussed in considerable detail in this review. We point out certain difficulties with this theory that make it seem unlikely that this is the whole story. The main difficulty with this as the only such amplification mechanism is rooted in the fact that, on galactic scales, flux is constant and is frozen in the interstellar medium. This implies that flux must be removed from the galactic discs, as is well recognized by the standard theory. For our Galaxy this turns out to be a major problem, since unless the flux and the interstellar mass are somehow separated, some interstellar mass must also be removed from the deep galactic gravitational well. This is very difficult. It is pointed out that unless the field has a substantial field strength, much larger than that of the seed fields, this separation can hardly happen. And of course, it must if the ?-? dynamo is to start from the ultra weak seed field. (It is our philosophy, expressed in this review, that if an origin theory is unable to create the magnetic field in our Galaxy it is essentially incomplete.) Thus, it is more reasonable for the first and largest amplification to occur before the Galaxy forms, and the matter embedded in the field is gravitationally trapped. Two such mechanisms are discussed for such a pregalactic origin; (1) they are generated in the turbulence of the protogalaxy and (2) the fields come from giant radio jets. Several arguments against a primordial origin are also discussed, as are ways around them. Our conclusion as to the most likely origin of cosmic magnetic fields is that they are first produced at moderate field strengths by primordial mechanisms and then changed and their strength increased to their present value and structure by a galactic disc dynamo. The primordial mechanisms have not yet been seriously developed, and this preliminary amplification of the magnetic fi elds is still very open. If

  18. FLINESH computer code for magnetic fields calculation

    International Nuclear Information System (INIS)

    This paper describes the 'FLINESH' computer code for magnetic fields calculation developed for the simulation of field configurations in plasma magnetic confinement devices. The expressions for the poloidal field and flux, the program structure and the input parameters description are presented, and also the analysis of the graphic output possibilities. (L.C.J.A.). 12 refs, 14 figs, 2 tabs

  19. Cosmic Magnetic Fields from Particle Physics

    OpenAIRE

    Tornkvist, Ola

    2000-01-01

    I review a number of particle-physics models that lead to the creation of magnetic fields in the early universe and address the complex problem of evolving such primordial magnetic fields into the fields observed today. Implications for future observations of the Cosmic Microwave Background (CMB) are briefly discussed.

  20. Synchrotron Applications of High Magnetic Fields

    International Nuclear Information System (INIS)

    This workshop aims at discussing the scientific potential of X-ray diffraction and spectroscopy in magnetic fields above 30 T. Pulsed magnetic fields in the range of 30 to 40 T have recently become available at Spring-8 and the ESRF (European synchrotron radiation facility). This document gathers the transparencies of the 6 following presentations: 1) pulsed magnetic fields at ESRF: first results; 2) X-ray spectroscopy and diffraction experiments by using mini-coils: applications to valence state transition and frustrated magnet; 3) R5(SixGe1-x)4: an ideal system to be studied in X-ray under high magnetic field?; 4) high field studies at the Advanced Photon Source: present status and future plans; 5) synchrotron X-ray diffraction studies under extreme conditions; and 6) projects for pulsed and steady high magnetic fields at the ESRF

  1. Synchrotron Applications of High Magnetic Fields

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2006-07-01

    This workshop aims at discussing the scientific potential of X-ray diffraction and spectroscopy in magnetic fields above 30 T. Pulsed magnetic fields in the range of 30 to 40 T have recently become available at Spring-8 and the ESRF (European synchrotron radiation facility). This document gathers the transparencies of the 6 following presentations: 1) pulsed magnetic fields at ESRF: first results; 2) X-ray spectroscopy and diffraction experiments by using mini-coils: applications to valence state transition and frustrated magnet; 3) R{sub 5}(Si{sub x}Ge{sub 1-x}){sub 4}: an ideal system to be studied in X-ray under high magnetic field?; 4) high field studies at the Advanced Photon Source: present status and future plans; 5) synchrotron X-ray diffraction studies under extreme conditions; and 6) projects for pulsed and steady high magnetic fields at the ESRF.

  2. Earth's lithospheric magnetic field determined to spherical harmonic degree 90 from CHAMP satellite measurements

    DEFF Research Database (Denmark)

    Maus, S.; Rother, M.; Hemant, K.; Stolle, C.; Luhr, H.; Kuvshinov, A.; Olsen, Nils

    2006-01-01

    The CHAMP magnetic field mission is providing highly reliable measurements from which the global lithospheric magnetic field can be determined in unprecedented resolution and accuracy. Using almost 5 yr of data, we derive our fourth generation lithospheric field model termed MF4, which is expanded to spherical harmonic degree and order 90. After subtracting from the full magnetic field observations predicted fields from an internal field model up to degree 15, an external field model up to degre...

  3. International Geomagnetic Reference Field: the 12th generation

    DEFF Research Database (Denmark)

    Thébault, Erwan; Finlay, Chris

    2015-01-01

    The 12th generation of the International Geomagnetic Reference Field (IGRF) was adopted in December 2014 by the Working Group V-MOD appointed by the International Association of Geomagnetism and Aeronomy (IAGA). It updates the previous IGRF generation with a definitive main field model for epoch 2010.0, a main field model for epoch 2015.0, and a linear annual predictive secular variation model for 2015.0-2020.0. Here, we present the equations defining the IGRF model, provide the spherical harmonic coefficients, and provide maps of the magnetic declination, inclination, and total intensity for epoch 2015.0 and their predicted rates of change for 2015.0-2020.0. We also update the magnetic pole positions and discuss briefly the latest changes and possible future trends of the Earth’s magnetic field.

  4. EIT waves and coronal magnetic field diagnostics

    OpenAIRE

    Chen, P F

    2009-01-01

    Magnetic field in the solar lower atmosphere can be measured by the use of the Zeeman and Hanle effects. In contrast, the coronal magnetic field well above the solar surface, which directly controls various eruptive phenomena, can not be precisely measureed with the traditional techniques. Several attempts are being made to probe the coronal magnetic field, such as force-free extrapolation based on the photospheric magnetograms, gyroresonance radio emissions, and coronal sei...

  5. The Magnetic Field of Planet Earth

    DEFF Research Database (Denmark)

    Hulot, G.; Finlay, Chris; Constable, C. G.; Olsen, Nils; Mandea, M.

    2010-01-01

    The magnetic field of the Earth is by far the best documented magnetic field of all known planets. Considerable progress has been made in our understanding of its characteristics and properties, thanks to the convergence of many different approaches and to the remarkable fact that surface rocks have quietly recorded much of its history. The usefulness of magnetic field charts for navigation and the dedication of a few individuals have also led to the patient construction of some of the longest s...

  6. Minimizing magnetic fields for precision experiments

    CERN Document Server

    Altarev, I; Lins, T; Marino, M G; Nießen, B; Petzoldt, G; Reisner, M; Stuiber, S; Sturm, M; Singh, J T; Taubenheim, B; Rohrer, H K; Schläpfer, U

    2015-01-01

    An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a linear improvement in the systematic reach and a 40 % improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

  7. Minimizing magnetic fields for precision experiments

    Science.gov (United States)

    Altarev, I.; Fierlinger, P.; Lins, T.; Marino, M. G.; Nießen, B.; Petzoldt, G.; Reisner, M.; Stuiber, S.; Sturm, M.; Taggart Singh, J.; Taubenheim, B.; Rohrer, H. K.; Schläpfer, U.

    2015-06-01

    An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here, we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a 40% improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

  8. Helical cosmological magnetic fields from extra-dimensions

    Science.gov (United States)

    Atmjeet, Kumar; Seshadri, T. R.; Subramanian, Kandaswamy

    2015-05-01

    We study the inflationary generation of helical cosmological magnetic fields in a higher-dimensional generalization of the electromagnetic theory. For this purpose, we also include a parity breaking piece to the electromagnetic action. The evolution of an extra-dimensional scale factor allows the breaking of conformal invariance of the effective electromagnetic action in 1 +3 dimensions required for such generation. Analytical solutions for the vector potential can be obtained in terms of Coulomb wave-functions for some special cases. We also present numerical solutions for the vector potential evolution in more general cases. In the presence of a higher-dimensional cosmological constant there exist solutions for the scale factors in which both normal and extra dimensional space either inflate or deflate simultaneously with the same rate. In such a scenario, with the number of extra dimensions D =4 , a scale invariant spectrum of helical magnetic field is obtained. The net helicity arises, as one helical mode comes to dominate over the other at the superhorizon scales. A magnetic field strength of the order of 10-9 G can be obtained for the inflationary scale H ?1 0-3 Mpl . Weaker fields will be generated for lower scales of inflation. Magnetic fields generated in this model respects the bounds on magnetic fields by Planck and ? -ray observations (i.e., 10-16 G

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-15

    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.

  10. Fe{sub 3}Si nanoparticles for alternating magnetic field heating

    Energy Technology Data Exchange (ETDEWEB)

    Jing Ying; He, Shi-Hai; Wang Jianping, E-mail: jpwang@umn.edu [University of Minnesota, Department of Electrical and Computer Engineering, Center for Micromagnetics and Information Technologies (MINT) (United States)

    2013-04-15

    In this paper, Fe{sub 3}Si nanoparticles were fabricated and studied for alternating magnetic field heating. High-magnetic-moment and large magnetic anisotropy energy barrier were found for those particles through the temperature-dependent magnetic characterization and dynamic coercivity analysis. Although a large hysteresis area was expected for the nanoparticles to generate appreciable heat, it is not necessary so when only the criteria of saturation magnetization and magnetic anisotropy energy barrier are fulfilled. Heating performance of Fe{sub 3}Si nanoparticles was investigated. Field-dependent magnetic characterization unravels the fact that sufficient switching of magnetic nanoparticles is critical for heat generation.

  11. Origin of magnetic fields and overdense cosmology

    International Nuclear Information System (INIS)

    The problem of the origin of galactic magnetic fields is investigated. The investigation is carried out in the framework of V.A. Ambartsumian's overdense cosmology conceptions. The hypothesis has been discussed that the observable at the present time galactic magnetic fields are shown to be the remnants of the dipole magnetic fields of protogalaxies-superhadrons. It is concluded that the detailed development of the problem on the origin of galactic magnetic fields is related to the general problems of galactic evolution and to the necessity of plotting the basic theory of superhadrons

  12. The Humboldt High Magnetic Field Center at Berlin

    Energy Technology Data Exchange (ETDEWEB)

    Hansel, S; Mueller, H-U; Anh, T T; Richter, B; Rossmann, H; Ortenberg, M von [Magnetotransport in Solids, Department of Physics, Humboldt-Universitaet zu Berlin, Newtonstrasse 15, 12489 Berlin (Germany)

    2006-11-15

    The Humboldt High Magnetic Field Center is operated by the Chair for Magnetotransport in Solids of the Department of Physics of the Humboldt-Universitaet zu Berlin. It provides DC-magnetic fields up to 20 T, pulsed nondestructive fields of up to 60 T and megagauss fields of up to 331 T using a single-turn coil generator for experimental application focusing on solid state physics. Magneto-optical investigations are carried out in the MIR, NIR and visible wavelength range as well as transport and magnetization experiments. The facility is open to the scientific community and welcomes users within the European project EuroMagNET. The laboratory will be closed in fall 2006 but its experimental facilities will be further accessible to the community in other labs. The single-turn coil generator will be transferred to LNCMP, Toulouse, France, continuing to provide applicable megagauss fields to the European Community.

  13. Novel Topological Effects in Dense QCD in a Magnetic Field

    CERN Document Server

    Ferrer, E J

    2015-01-01

    We show that in dense QCD an axion field can be dynamically generated as the phase of the dual chiral density wave condensate that forms in the presence of a magnetic field. The coupling of the axion with the external magnetic field leads to several macroscopically observable effects. They are the generation of an anomalous uniform electric charge proportional to the magnetic field, the induction of a nondissipative anomalous Hall current, a linear magnetoelectric effect, and the formation of an axion polariton due to the fluctuations of the axion field at finite temperature. Connection to topological insulators, as well as possible observable signatures in heavy-ion collisions and neutron stars are all highlighted.

  14. Magnetotransport in a spatially modulated magnetic field

    Scientific Electronic Library Online (English)

    G.M., Gusev; A. A., Quivy; J.R., Leite; A. A., Bykov; N.T., Moshegov; V.M., Kudryashev; A.I., Toropov; Yu.V., Nastaushev.

    1999-12-01

    Full Text Available We have measured the Shubnikov de Haas (SdH) oscillations of a nonplanar two-dimensional electron gas (2DEG) fabricated by overgrowth of a GaAs/AlGaAs heterojunction on a pre-patterned substrate. When placed in a uniform external magnetic field B, the field normal to the nonplanar 2DEG is spatially [...] modulated, and electrons experience a nonuniform magnetic field. In a tilted magnetic field, the SdH oscillations are much more strongly damped than in a field perpendicular to the substrate. We consider several mechanisms and conclude that the electron scattering by the magnetic field spatial uctuations plays a main role in the transport properties of a nonplanar 2DEG at low magnetic field.

  15. Analytical estimation of the Earth's magnetic field scale

    CERN Document Server

    Bologna, Mauro

    2012-01-01

    In this paper we analytically estimate the magnetic field scale of planets with physical core conditions similar to that of Earth from a statistical point of view. We evaluate the magnetic field on the basis of the physical parameters of the center of the planet, such as density, temperature, and core size. We look at the contribution of the Peltier-Seebeck effect on the magnetic field, showing that an electrical thermal current can exist in a rotating fluid sphere. Finally, we apply our calculations to Earth and Jupiter. In each case we show that the thermal generation of currents leads to a magnetic field scale comparable to the observed fields of the two planets.

  16. High concentration ferronematics in low magnetic fields

    International Nuclear Information System (INIS)

    We investigated experimentally the magneto-optical and dielectric properties of magnetic-nanoparticle-doped nematic liquid crystals (ferronematics). Our studies focus on the effect of the very small orienting bias magnetic field Bbias, and that of the nematic director pretilt at the boundary surfaces in our systems sensitive to low magnetic fields. Based on the results we assert that Bbias is not necessarily required for a detectable response to low magnetic fields, and that the initial pretilt, as well as the aggregation of the nanoparticles play an important (though not yet explored enough) role. - Highlights: • Response to low magnetic fields was detected in high concentration ferronematics. • The role of the orienting bias magnetic field is discussed. • The influence of the pretilt angle and that of the aggregation is described. • Doping the liquid crystal with nanoparticles does not change the birefringence. • The phase transition temperature of the nematic does not change with doping

  17. Principles of power frequency magnetic field management

    International Nuclear Information System (INIS)

    At the most general level, magnetic field management is the creation, elimination, or modification of sources in order to alter the spatial distribution of magnetic fields over some region of space. The two main options for magnetic field management are source modification (elimination or modification of original sources) and cancellation (creation of new sources). Source modification includes any changes in the layout or location of field sources, elimination of ground paths, or any options that increase the distance between sources and regions of interest. Cancellation involves the creation of new magnetic field sources, passive and/or active that produce magnetic fields that are opposite to the original fields in the region of interest. Shielding using materials of high conductivity and/or high permeability falls under the cancellation option. Strategies for magnetic field management, whether they are source modification or cancellation, typically vary on a case to case basis depending on the regions of interest, the types of sources and resulting complexity of the field structure, the field levels, and the attenuation requirements. This paper gives an overview of magnetic field management based on fundamental concepts. Low field design principles are described, followed by a structured discussion of cancellation and shielding. The two basic material shielding mechanisms, induced current shielding, and flux-shunting are discussed

  18. Solar Force-free Magnetic Fields

    Directory of Open Access Journals (Sweden)

    Thomas Wiegelmann

    2012-09-01

    Full Text Available The structure and dynamics of the solar corona is dominated by the magnetic field. In most areas in the corona magnetic forces are so dominant that all non-magnetic forces like plasma pressure gradient and gravity can be neglected in the lowest order. This model assumption is called the force-free field assumption, as the Lorentz force vanishes. This can be obtained by either vanishing electric currents (leading to potential fields or the currents are co-aligned with the magnetic field lines. First we discuss a mathematically simpler approach that the magnetic field and currents are proportional with one global constant, the so-called linear force-free field approximation. In the generic case, however, the relation between magnetic fields and electric currents is nonlinear and analytic solutions have been only found for special cases, like 1D or 2D configurations. For constructing realistic nonlinear force-free coronal magnetic field models in 3D, sophisticated numerical computations are required and boundary conditions must be obtained from measurements of the magnetic field vector in the solar photosphere. This approach is currently of large interests, as accurate measurements of the photospheric field become available from ground-based (for example SOLIS and space-born (for example Hinode and SDO instruments. If we can obtain accurate force-free coronal magnetic field models we can calculate the free magnetic energy in the corona, a quantity which is important for the prediction of flares and coronal mass ejections. Knowledge of the 3D structure of magnetic field lines also help us to interpret other coronal observations, e.g., EUV images of the radiating coronal plasma.

  19. Strangelets under strong magnetic fields

    CERN Document Server

    Fune, E Lopez

    2012-01-01

    In this thesis is studied three of the fundamental properties of clusters of matter made of quarks u, d and s called strangelets: the energy per baryon, the radius and the electric charge, all in the presence of intense magnetic fields and finite temperature. Two cases will take our attention: unpaired phase strangelets, where there is no restriction to the number of flavors of quarks, and a particular case of the color superconducting phase, where exists a restriction to the quark numbers and an additional energy gap. We study the stability of strangelets, measured by the energy per baryon, to compare later with that of the 56Fe : the most stable isotope known in nature. We employ the Liquid Drop formalism of the Bag Model MIT to describe the interaction between quarks. We conclude that the field effects tend to decrease the energy per baryon of strangelets and temperature produces the opposite effect. It is also shown that strangelets in the color superconducting phase are more stable than those in the unpa...

  20. Primordial magnetic fields from preheating at the electroweak scale

    CERN Document Server

    Diaz-Gil, Andres; Perez, Margarita Garcia; Gonzalez-Arroyo, Antonio

    2008-01-01

    We analyze the generation of helical magnetic fields during preheating in a model of low-scale electroweak (EW) hybrid inflation. We show how the inhomogeneities in the Higgs field, resulting from tachyonic preheating after inflation, seed the magnetic fields in a way analogous to that predicted by Vachaspati and Cornwall in the context of the EW symmetry breaking. At this stage, the helical nature of the generated magnetic fields is linked to the non-trivial winding of the Higgs-field. We analyze non-perturbatively the evolution of these helical seeds through the highly non-linear stages of symmetry breaking (SB) and beyond. Electroweak SB occurs via the nucleation and growth of Higgs bubbles which squeeze the magnetic fields into string-like structures. The W-boson charge density clusters in lumps around the magnetic strings. After symmetry breaking, a detailed analysis of the magnetic field Fourier spectrum shows two well differentiated components: a UV radiation tail at a temperature T ~ 0.23 m_higgs slow...