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1

Toroidal magnetic field generation device  

International Nuclear Information System (INIS)

Purpose: To facilitate the assembly work and improve the reliability by disposing the main body of a toroidal magnetic field generation device to the inside of a vacuum container. Constitution: Surfaces of a coil container, a feedwater heater and each of the components exposed in vacuum are made of such material and configuration as suitable to the use in superhigh vacuum, and a toroidal electromagnet is cooled by water from outside of the vacuum container. Toroidal magnetic field can be formed in the vacuum by the toroidal magnetic field generation device main body disposed in the vacuum container, whereby complicated steps such as the assembly of the main body of the toroidal magnetic field generation device crossing to the outer circumferential surface of doughnut-shaped pipes can be saved. (Horiuchi, T.)

1981-01-01

2

Magnetic field generation in shock waves  

Energy Technology Data Exchange (ETDEWEB)

The equation which governs the changes in the magnetic field as function of time is given. The first two terms on the right hand side are the convection and diffusion term. The third term represents the source term for magnetic field generation in a plasma due to non-parallel temperature and density gradients. Such gradients develop when a supersonic plasma jet interacts with a background plasma. For large Mach numbers the axial shock compression ratio of the density approaches a limiting value of four while the temperature ratio can increase far above four. Perpendicular to this axial temperature gradient the radial density gradient of the jet is dictated by ion motion. Due to their large thermal velocity, a radial electron temperature gradient relaxes faster than the radial density gradient. This cross product of the dominant gradients, radial density gradient of the jet and shock created axial temperature gradient causes magnetic field generation in azimuthal direction as experimentally observed. Recent numerical simulations, guided by experimental data, provide useful insights and verification of the field generating mechanism. This mechanism for magnetic field generation can occur in a field free region where B = 0, in contrast to the dynamo mechanism which requires an initial seed magnetic field. It may be assumed that this mechanism of magnetic field generation is also of importance under astrophysical conditions.

Schwirzke, F.; Carter, J.P. [Naval Postgraduate School, Monterey, CA (United States). Physics Dept.

1994-12-31

3

Generation of magnetic fields for accelerators with permanent magnets  

International Nuclear Information System (INIS)

Commercially available permanent magnet materials and their properties are reviewed. Advantages and disadvantages of using permanent magnets as compared to electromagnets for the generation of specific magnetic fields are discussed. Basic permanent magnet configurations in multipole magnets and insertion devices are presented. (orig.)

1994-01-26

4

The generation of cosmic magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

Most of the magnetic fields of cosmic objects are generated and maintained by dynamo action of the motions of electrically conducting fluids. A brief survey on observational facts concerning cosmic magnetic fields is given. Some basic principles of magnetofluiddynamics are explained. On this basis essential features of the dynamo theory of cosmic objects are developed, first on the kinematic level and later taking into account the full interaction between magnetic field and motion. Particular attention is paid on mean-field electrodynamics and mean-field magnetofluiddynamics and their application to mean-field dynamo models for objects showing irregular or turbulent motions and magnetic fields. A few explanations are given on dynamos in the Earth and the planets, in the Sun and stellar objects and in galaxies. (orig.)

Raedler, K.H. [Astrophysikalisches Inst. Potsdam (Germany)

2000-07-01

5

Generation of magnetic fields in planets  

International Nuclear Information System (INIS)

The strong and persistent magnetic fields of virtually all classes of cosmic objects are attributed to an active generation process known as the MHD dynamo. The regenerative power of dynamo fluid motions derives from the cyclonic or helical character of convection in rotating bodies. The small-scale, rapid variations in the field are a direct manifestation of the generation process, and the long-term behavior patterns carry important clues about the field's structure and dynamical state. 24 references

1986-01-01

6

Magnetic Field Generation by Relativistic Shear Flows  

Science.gov (United States)

We report PIC simulation results of magnetic field generation by relativistic shear flows. We find that the shear flow boundary layer in initially non-magnetic shear flows is unstable to the growth of oblique 2-stream and Weibel instabilities near the boundary layer. Such instabilities generate current sheets and loops which eventually form nonlinear ordered structures resembling magnetic flux tubes with alternating polarity, orthogonal to the shear flow direction. Peak magnetic fields can reach almost equipartition values. The size and amplitude of such magnetic structures reach a steady state when the free energy input of the shear flow is balanced by turbulence dissipation. Nonthermal particles are efficiently accelerated, likely by the drift-kink instability, into a power-law energy distribution. These results have important implications for many astrophysical settings, including multi-component blazar jets and gamma-ray bursts. This work was supported by NSF AST0909167 and NASA Fermi grants.

Liang, Edison; Boettcher, Markus; Smith, Ian

2011-11-01

7

Magnetic field generation in the underdense plasma  

International Nuclear Information System (INIS)

Magnetic field generation in the underdense plasma due to the nonlinear interaction of an electromagnetic wave and a plasma is investigated. It is shown that the collisional absorption of the electromagnetic wave induces a nonlinear anistropy in the electron pressure tensor, which is responsible for a large source of the dc magnetic field. Six different regimes of interest appear, depending on four characteristic parameters related to the collision rate, the thermal effects, hydrodynamic convection, and the duration of the experiment. The theory is supported by a detailed comparison with recent microwave plasma experiments

1981-01-01

8

Error field generation of solenoid magnets  

Energy Technology Data Exchange (ETDEWEB)

Many applications for large solenoids and solenoidal arrays depend on the high precision of the axial field profile. In cases where requirements of ..delta..B/B for nonaxial fields are on the order of 10/sup -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.

Saunders, J.L.

1982-01-01

9

The ULF Magnetic Fields Generated by Thunderstorms  

Science.gov (United States)

It has long been known that thunderstorms produce strong electric field fluctuations in their immediate vicinity but it has been little recognized that these storms are also a source of strong ULF magnetic field fluctuations (ULF; frequencies less than 5 Hz). Some characteristics of the magnetic field fluctuations were documented for a thunderstorm occurring in 1990 [Fraser-Smith, Geophys. Res. Letts., 20, 467-470, 1993]. We now describe further measurements of these magnetic field changes for an additional intense thunderstorm that passed over the San Francisco Bay area on 8-9 September 1999. The thunderstorm is further characterized by measurements of its associated lightning by the National Lightning Detection Network (NLDN). As compared with the results reported for the 1990 thunderstorm, the new measurements were made by two separate and independently-operated measurement systems. In addition, they have greater time resolution and more components of the magnetic field changes are measured. These thunderstorm-related ULF magnetic field changes must extend up through the electromagnetic-phenomena-rich space between the thunderstorms and the ionosphere and they have the potential to generate both ULF electric currents and ULF hydromagnetic waves in the lower ionosphere. This latter possibility suggests, once again, that thunderstorms may be an important and little studied source of ULF energy in the magnetosphere. In this context, it is important to note that although thunderstorms tend to occur predominantly in the equatorial regions, there can be substantial activity at middle latitudes and even, on occasion, at higher latitudes. As a result, the thunderstorm-related ULF hydromagnetic waves can be injected into the magnetosphere over a broad range of geomagnetic latitudes and not just confined to low latitudes.

Fraser-Smith, A. C.; Kjono, S. N.

2013-12-01

10

Magnetic fields generated by the Rayleigh-Taylor instability  

International Nuclear Information System (INIS)

In the absence of magnetic diffusion the self-generated magnetic field in a plasma is proportional to the fluid vorticity. The ratio of magnetic to fluid energy then shows that self-generated magnetic fields can only affect the Rayleigh Taylor growth rate for large kappa (wavelengths less than a few microns). (author)

1986-01-01

11

Mean magnetic field generation in sheared rotators  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A generalized mean magnetic field induction equation for differential rotators is derived, including a compressibility, and the anisotropy induced on the turbulent quantities from the mean magnetic field itself and a mean velocity shear. Derivations of the mean field equations often do not emphasize that there must be anisotropy and inhomogeneity in the turbulence for mean field growth. The anisotropy from shear is the source of a term involving the product of the mean veloc...

Blackman, Eric G.

1999-01-01

12

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)

2005-01-01

13

High Magnetic Field Generator of Sub-Microsecond Duration  

Directory of Open Access Journals (Sweden)

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

Audrius Grainys

2012-04-01

14

High Magnetic Field Generator of Sub-Microsecond Duration  

Directory of Open Access Journals (Sweden)

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

Audrius Grainys

2012-01-01

15

Generation of magnetic fields in plasmas  

International Nuclear Information System (INIS)

Relativistic and non-relativistic plasma outflows are quite ubiquitous in astrophysical scenarios, as well as in laboratory plasmas. The propagation of relativistic and non- relativistic charged particle beams in background plasmas provides return currents in the opposite direction and interactions between the currents then drive several plasma instabilities involving the longitudinal (electrostatic instabilities) and trans- verse (electromagnetic instability) modes. Such instabilities have been accepted as possible mechanisms for generating spontaneous magnetic fields in extreme astrophysical environments, such as the gamma-ray bursts (GRBs), pulsar magnetosphere, active galactic nuclei (AGN), as well as in laboratory plasmas such as those in inertial confinement fusion schemes. In the present thesis, we have studied several aspects of waves and instabilities in both unmagnetized and magnetized plasmas. We have calculated the linear growth rates of the plasma instabilities that can occur in the presence of counter-propagating anisotropic plasmas (the Weibel instability/filamentation instability) in an unmagnetized plasma, due to the counter-streaming of electrons and positrons in uniform and nonuniform magnetoplasmas, and by a nonstationary ponderomotive force of an electromagnetic wave in a warm plasma. Comprehensive analytical and numerical studies of plasma instabilities have been made to understand possible mechanisms for purely growing magnetic fields in the presence of mobile/immobile ions and (or) cold/mildly hot electron beams. The theory has been developed for a proper understanding of fast as well as slow phenomena in plasmas by using the kinetic, fluid and magnetohydrodynamic (MHD) approaches. Specific applications are presented, including inertial confinement fusion; Gamma- rays bursts (GRBs), and pulsar magnetosphere. We have also studied new and purely growing modes in quantum-plasmas, which happen to be a rapidly growing emerging subfield of plasma physics. We have investigated an oscillatory instability involving dust acoustic-like waves due to a relative drift between the ions and the charged dust particles in quantum dusty magneto-plasma. This study can be of importance in semiconductor plasmas or in astrophysical plasmas, such as those in the cores of white dwarfs

2012-01-01

16

Generation of magnetic fields in plasmas  

Energy Technology Data Exchange (ETDEWEB)

Relativistic and non-relativistic plasma outflows are quite ubiquitous in astrophysical scenarios, as well as in laboratory plasmas. The propagation of relativistic and non- relativistic charged particle beams in background plasmas provides return currents in the opposite direction and interactions between the currents then drive several plasma instabilities involving the longitudinal (electrostatic instabilities) and trans- verse (electromagnetic instability) modes. Such instabilities have been accepted as possible mechanisms for generating spontaneous magnetic fields in extreme astrophysical environments, such as the gamma-ray bursts (GRBs), pulsar magnetosphere, active galactic nuclei (AGN), as well as in laboratory plasmas such as those in inertial confinement fusion schemes. In the present thesis, we have studied several aspects of waves and instabilities in both unmagnetized and magnetized plasmas. We have calculated the linear growth rates of the plasma instabilities that can occur in the presence of counter-propagating anisotropic plasmas (the Weibel instability/filamentation instability) in an unmagnetized plasma, due to the counter-streaming of electrons and positrons in uniform and nonuniform magnetoplasmas, and by a nonstationary ponderomotive force of an electromagnetic wave in a warm plasma. Comprehensive analytical and numerical studies of plasma instabilities have been made to understand possible mechanisms for purely growing magnetic fields in the presence of mobile/immobile ions and (or) cold/mildly hot electron beams. The theory has been developed for a proper understanding of fast as well as slow phenomena in plasmas by using the kinetic, fluid and magnetohydrodynamic (MHD) approaches. Specific applications are presented, including inertial confinement fusion; Gamma- rays bursts (GRBs), and pulsar magnetosphere. We have also studied new and purely growing modes in quantum-plasmas, which happen to be a rapidly growing emerging subfield of plasma physics. We have investigated an oscillatory instability involving dust acoustic-like waves due to a relative drift between the ions and the charged dust particles in quantum dusty magneto-plasma. This study can be of importance in semiconductor plasmas or in astrophysical plasmas, such as those in the cores of white dwarfs.

Shukla, Nitin

2012-07-01

17

Methods of Generation of Ultrahigh Pulsed Magnetic Field.  

Science.gov (United States)

The main obstacles on the way to obtain high magnetic fields in a single turn coil and in an explosive generator are reviewed. It is shown, that reliability achievable magnetic fields in the single turn coil can't exceed about 300 T because of deformation...

S. Golberg M. A. Liberman H. Almstroem

1995-01-01

18

Near field and magnetic field generator for thermal assisted magnetic recording  

International Nuclear Information System (INIS)

We fabricated a generator that produces optical near field and magnetic filed in a nanometer area for achievement of thermally assisted magnetic recording. The generator consists of an embedded wire with a bottleneck structure on a SiO2 substrate. The magnetic field is mainly generated around the bottleneck structure by feeding current through the wire. The near field is produced on an edge of the narrow wire by focusing a laser beam on the bottleneck structure through the backside of the substrate. The generator is anticipated as application to control ordering, chirality, and phase transition of diamagnetic materials in a nano-area. We confirmed the three-dimentional localization of near field in the nanometer size around the bottleneck structure by means of a near field scanning optical microscope

2007-11-20

19

Magnetic Field Correlation as a Measure of Iron-Generated Magnetic Field Inhomogeneities in the Brain  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The magnetic field correlation (MFC) at an applied field level of 3 T was estimated by means of MRI in several brain regions for 21 healthy human adults and one subject with aceruloplasminemia. For healthy subjects, highly elevated MFC values compared to surrounding tissues were found within the basal ganglia. These are argued as being primarily the result of microscopic magnetic field inhomogeneities generated by non-heme brain iron. The MFC in the aceruloplasminemia subject was significantl...

Jensen, Jens H.; Szulc, Kamila; Hu, Cathy; Ramani, Anita; Lu, Hanzhang; Xuan, Liang; Falangola, Maria F.; Chandra, Ramesh; Knopp, Edmond A.; Schenck, John; Zimmerman, Earl A.; Helpren, Joseph A.

2009-01-01

20

Electron beam therapy with coil-generated magnetic fields.  

Science.gov (United States)

This paper presents an initial study on the issues involved in the practical implementation of the use of transverse magnetic fields in electron beam therapy. By using such magnetic fields the dose delivered to the tumor region can increase significantly relative to that deposited to the healthy tissue. Initially we calculated the magnetic fields produced by the Helmholtz coil and modified Helmholtz coil configurations. These configurations, which can readily be used to generate high intensity magnetic fields, approximate the idealized magnetic fields studied in our previous publications. It was therefore of interest to perform a detailed study of the fields produced by these configurations. Electron beam dose distributions for 15 MeV electrons were calculated using the ACCEPTM code for a 3T transverse magnetic field produced by the modified Helmholtz configuration. The dose distribution was compared to those obtained with no magnetic field. The results were similar to those obtained in our previous work, where an idealized step function magnetic field was used and a 3T field was shown to be the optimal field strength. A simpler configuration was also studied in which a single external coil was used to generate the field. Electron dose distributions are also presented for a given geometry and given magnetic field strength using this configuration. The results indicate that this method is more difficult to apply to radiotherapy due to its lack of symmetry and its irregularity. For the various configurations dealt with here, a major problem is the need to shield the magnetic field in the beam propagation volume, a topic that must be studied in detail. PMID:15259653

Nardi, Eran; Barnea, Gideon; Ma, Chang-Ming

2004-06-01

 
 
 
 
21

Electron beam therapy with coil-generated magnetic fields  

International Nuclear Information System (INIS)

This paper presents an initial study on the issues involved in the practical implementation of the use of transverse magnetic fields in electron beam therapy. By using such magnetic fields the dose delivered to the tumor region can increase significantly relative to that deposited to the healthy tissue. Initially we calculated the magnetic fields produced by the Helmholtz coil and modified Helmholtz coil configurations. These configurations, which can readily be used to generate high intensity magnetic fields, approximate the idealized magnetic fields studied in our previous publications. It was therefore of interest to perform a detailed study of the fields produced by these configurations. Electron beam dose distributions for 15 MeV electrons were calculated using the ACCEPTM code for a 3T transverse magnetic field produced by the modified Helmholtz configuration. The dose distribution was compared to those obtained with no magnetic field. The results were similar to those obtained in our previous work, where an idealized step function magnetic field was used and a 3T field was shown to be the optimal field strength. A simpler configuration was also studied in which a single external coil was used to generate the field. Electron dose distributions are also presented for a given geometry and given magnetic field strength using this configuration. The results indicate that this method is more difficult to apply to radiotherapy due to its lack of symmetry and its irregularity. For the various configurations dealt with here, a major problem is the need to shield the magnetic field in the beam propagation volume, a topic that must be studied in detail

2004-06-01

22

Magnetic field structure generation in collisional dusty plasmas  

Science.gov (United States)

A perpendicular ion drift is proposed as a possible mechanism for the generation of magnetic field structures in a highly collisional dusty plasma. The basic dissipation mechanism is assumed to be the dust-neutral momentum exchange, so that plasmas with a small ionization fraction are natural candidates for experiments. The model reduces to a nonlinear partial differential equation for the vector potential. The conditions for linear instability are presented. Possible stationary states are periodic arrangements for the magnetic field, described by a Lienard equation. The fully depleted (ion-dust) case is also considered in detail. Applications of the present work to magnetic field structures in planetary rings, comets and low-temperature dusty plasma experiments are discussed. A necessary condition for the validity of the model is a sufficiently slow time-scale of the generated magnetic fields in dusty plasmas.

Kant Shukla, Padma; Haas, Fernando

2008-11-01

23

Magnetic Field Generation and Electron Acceleration in Relativistic Laser Channel  

International Nuclear Information System (INIS)

The interaction between energetic electrons and a circularly polarized laser pulse inside an ion channel is studied. Laser radiation can be resonantly absorbed by electrons executing betatron oscillations in the ion channel and absorbing angular momentum from the laser. The absorbed angular momentum manifests itself as a strong axial magnetic field (inverse Faraday effect). The magnitude of this magnetic field is calculated and related to the amount of the absorbed energy. Absorbed energy and generated magnetic field are estimated for the small and large energy gain regimes. Qualitative comparisons with recent experiments are also made

2001-01-01

24

Saturation of Magnetorotational Instability through Magnetic Field Generation  

CERN Document Server

The saturation mechanism of Magneto-Rotational Instability (MRI) is examined through analytical quasilinear theory and through nonlinear computation of a single mode in a rotating disk. We find that large-scale magnetic field is generated through the alpha effect (the correlated product of velocity and magnetic field fluctuations) and causes the MRI mode to saturate. If the large-scale plasma flow is allowed to evolve, the mode can also saturate through its flow relaxation. In astrophysical plasmas, for which the flow cannot relax because of gravitational constraints, the mode saturates through field generation only.

Ebrahimi, F; Schnack, D D

2009-01-01

25

Particle Acceleration and Magnetic Field Generation in Shear-Flows  

Science.gov (United States)

We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic (core) jet and an unmagnetized sheath plasma by the kinetic Kelvin-Helmholtz instability for different mass ratios (mi/me = 1, 20, and 1836) and different jet Lorentz factors. We found that electron-positron cases have alternating magnetic fields instead of the DC magnetic fields found in electron-ion cases. We have also investigated particle acceleration and shock structure associated with an unmagnetized relativistic jet propagating into an unmagnetized plasma for electron-positron and electron-ion plasmas. Strong magnetic fields generated in the trailing shock lead to transverse deflection and acceleration of the electrons. We have self-consistently calculated the radiation from the electrons accelerated in the turbulent magnetic fields for different jet Lorentz factors. We find that the synthetic spectra depend on the bulk Lorentz factor of the jet, the jet temperature, and the strength of the magnetic fields generated in the shock.

Nishikawa, K.-I.; Hardee, P.; Mizuno, Y.; Du?an, I.; Zhang, B.; Medvedev, M.; Meli, A.; Choi, E. J.; Min, K. W.; Niemiec, J.; Nordlund, Å.; Frederiksen, J.; Sol, H.; Pohl, M.; Hartmann, D. H.; Marscher, A.; Gómez, J. L.

2014-03-01

26

Propagation of electromagnetically generated wake fields in inhomogeneous magnetized plasmas  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Generation of wake fields by a short electromagnetic pulse in a plasma with an inhomogeneous background magnetic field and density profile is considered, and a wave equation is derived. Transmission and reflection coefficients are calculated in a medium with sharp discontinuities. Particular attention is focused on examples where the longitudinal part of the electromagnetic field is amplified for the transmitted wave. Furthermore, it is noted that the wake field can propagat...

Servin, Martin; Brodin, Gert

2001-01-01

27

Energy confinement and magnetic field generation in the SSPX spheromak  

International Nuclear Information System (INIS)

The Sustained Spheromak Physics Experiment (SSPX) [Hooper et al., Nuclear Fusion 39, 863 (1999)] 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 (Te) recorded for a spheromak with Te>500 eV, toroidal magnetic field ?1 T, and toroidal current (?1 MA) [Wood et al., 'Improved magnetic field generation efficiency and higher temperature spheromak plasmas', Phys. Rev. Lett. (submitted)]. Extending the sustainment phase to >8 ms extends the period of low magnetic fluctuations (pol/?gun. Successive gun pulses are demonstrated to maintain the magnetic field in a quasisteady state against resistive decay. Initial measurements of neutral particle flux in multipulse operation show charge-exchange power loss e(r) associated with q?1/2

2008-05-01

28

Heat diffusion and magnetic field generation  

International Nuclear Information System (INIS)

In the report of CECAM workshop in 1982 some results of heat diffusion, when the spontaneous B-field is calculated, have been given. Separately, a similar code (magneto-calo-dynamic or MCD code) has been built and it was interesting to compare them. Comparisom has been made during the workshop of October 1983

1983-10-01

29

Relativistic Scott correction in self-generated magnetic fields.  

DEFF Research Database (Denmark)

We consider a large neutral molecule with total nuclear charge Z in a model with self-generated classical magnetic field and where the kinetic energy of the electrons is treated relativistically. To ensure stability, we assume that Za < 2/p, where a denotes the fine structure constant. We are interested in the ground state energy in the simultaneous limit Z ¿ 8, a ¿ 0 such that ¿ = Za is fixed. The leading term in the energy asymptotics is independent of ¿, it is given by the Thomas-Fermi energy of order Z7/3 and it is unchanged by including the self-generated magnetic field. We prove the first correction term to this energy, the so-called Scott correction of the form S(aZ)Z2. The current paper extends the result of Solovej et al. [Commun. Pure Appl. Math. LXIII, 39â??118 (2010)] on the Scott correction for relativistic molecules to include a self-generated magnetic field. Furthermore, we show that the corresponding Scott correction function S, first identified by Solovej et al. [Commun. Pure Appl. Math. LXIII,39â??118 (2010)], is unchanged by including a magnetic field. We also prove new Lieb-Thirring inequalities for the relativistic kinetic energy with magnetic fields.

Erdos, Laszlo; Fournais, Søren

2012-01-01

30

Seed Magnetic Fields Generated by Primordial Supernova Explosions  

CERN Document Server

The origin of the magnetic field in galaxies is an open question in astrophysics. Several mechanisms have been proposed related, in general, with the generation of small seed fields amplified by a dynamo mechanism. In general, these mechanisms have difficulty in satisfying both the requirements of a sufficiently high strength for the magnetic field and the necessary large coherent scales. We show that the formation of dense and turbulent shells of matter, in the multiple explosion scenario of Miranda and Opher (1996, 1997) for the formation of the large-scale structures of the Universe, can naturally act as a seed for the generation of a magnetic field. During the collapse and explosion of Population III objects, a temperature gradient not parallel to a density gradient can naturally be established, producing a seed magnetic field through the Biermann battery mechanism. We show that seed magnetic fields $\\sim 10^{-12}-10^{-14}G$ can be produced in this multiple explosion scenario on scales of the order of clu...

Miranda, O D; Opher, R

1998-01-01

31

Cosmological magnetic fields: generation during inflation and evolution  

CERN Document Server

This paper concerns the generation and evolution of the cosmological (large-scale $\\sim Mpc$) magnetic fields in an inflationary universe. The universe during inflation is represented by de Sitter space-time. We started with the Maxwell equations in spatially flat Friedmann-Robertson-Walker (FRW) Cosmologies. Then we calculated the wave equations of the magnetic field and electric field for the evolution. We consider the input current that was produced from a massless charged scalar complex field. This field minimally coupled to both gravity and the electromagnetic fields. The Lagrangian for massless scalar electrodynamics is then $L=\\sqrt{-g}(D_\\mu\\phi(D^\\mu\\phi)^*-{1/4}F_{\\mu\

Dai, Z

2003-01-01

32

Second order semiclassics with self-generated magnetic fields  

DEFF Research Database (Denmark)

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 �¿B 2 and we minimize over all magnetic fields. The parameter � effectively determines the strength of the field. We consider the weak field regime with �h2 = 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.

Erdös, Laszlo; Fournais, Søren

2012-01-01

33

Entropy Generation in Natural Convection Under an Evanescent Magnetic Field  

International Nuclear Information System (INIS)

We numerically study the effect of an externally-evanescent magnetic field on total entropy generation in conducting and non-reactive fluid enclosed in a square cavity. The horizontal walls of the enclosure are assumed to be insulated while the vertical walls are kept isothermal. A control volume finite element method is used to solve the conservation equations at Prandtl number of 0.71. The values of relaxation time of the magnetic field are chosen, so that the Lorentz force acts only in the transient state of entropy generation in natural convection. The total entropy generation was calculated for fixed value of irreversibility distribution ratio, different relaxation time varying from 0 to 1/5 and Grashof number equal to 105

2009-05-01

34

On the electric and magnetic field generation in expanding plasmas  

International Nuclear Information System (INIS)

This thesis deals with the generation of electric and magnetic fields in expanding plasmas. The theoretical model used to calculate the different field quantities in such plasmas is discussed in part 1 and is in fact an analysis of Ohm's law. A general method is given that decomposes each of the forces terms in Ohm's law in a component that induces a charge separation in the plasma and in a component that can drive current. This decomposition is unambiguous and depends upon the boundary conditions for the electric potential. It is shown that in calculating the electromagnetic field quantities in a plasma that is located in the vicinity of a boundary that imposes constraints on the electric potential, Ohm's law should be analyzed instead of the so-called induction equation. Three applications of the model are presented. A description is given of the unipolar arc discharge where both plasma and sheath effects have been taken into account. Secondly a description is presented of the plasma effects of a cathode spot. The third application of the model deals with the generation of magnetic fields in laser-produced plasmas. The second part of this thesis describes the experiments on a magnetized argon plasma expanding from a cascaded arc. With the use of spectroscopic techniques the electron density, ion temperature and the rotation velocity profiles of the ion gas have been determined. The magnetic field generated by the plasma has been measured with the use of the Zeeman effect. Depending on the channel diameter of the nozzle of the cascaded arc, self-generated magnetic fields with axial components of the order of 1% of the externally applied mangetic field have been observed. From the measured ion rotation it has been concluded that this magnetic field is mainly generated by azimuthal electron currents. The corresponding azimuthal current density is of the order of 15% of the axial current density. The observed ion rotation is caused by electron-ion friction. (author). 77 refs.; 69 figs.; 1 tab

1989-01-01

35

Dark matter and generation of galactic magnetic fields  

CERN Document Server

A mechanism for creation of galactic and intergalactic magnetic fields at a recent cosmological epoch is proposed. We show that in rotating protogalaxies circular electric currents are generated by the interactions of free electrons with dark matter particles while the impact of such interactions on galactic protons is considerably weaker. Light dark matter particles can be efficient for generation of such currents if these particles have some long range interactions. In particular, millicharged warm dark matter particles or light mirror particles with the photon kinetic mixing to the usual matter are considered. The induced currents may be strong enough to create the observed magnetic fields on the galaxy scales without need for a strong dynamo amplification. On the other hand, the angular momentum transfer from the rotating gas to dark matter component could change the dark matter profile and formation of cusps at galactic centers would be inhibited. We also discuss how the global motion of the ionized gas ...

Berezhiani, Zurab; Tkachev, I I

2013-01-01

36

Generation of Seed Magnetic Fields in Primordial Supernova Remnants  

CERN Multimedia

Origin of the magnetic field ubiquitous in the Universe is studied based on the Biermann mechanism, which is expected to work in the non-barotropic region. We perform a series of two-dimensional MHD simulations of the first generation supernova remnant (SNR) expanding in the inhomogeneous interstellar matter (ISM) and study the Biermann mechanism working in the interior of the SNR. Especially, we pay attention to the relaxation process of electron and ion temperatures via the Coulomb interaction. In the early SNR in which the electron temperature is much lower than the ion temperature, the Biermann mechanism is ineffective, since the gradient of electron pressure is small. Magnetic fields begin to be generated just behind the shock front when the electron temperature is sufficiently relaxed. Assuming the explosion energy of 10^52 erg, the total magnetic energy generated reaches about 10^26 erg and does not depend strongly on the parameters of either SNR or ISM. Analytic expression to estimate the magnetic tot...

Hanayama, Hidekazu; Tomisaka, Kohji

2009-01-01

37

PHASE TRANSITION GENERATED COSMOLOGICAL MAGNETIC FIELD AT LARGE SCALES  

International Nuclear Information System (INIS)

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

2011-01-10

38

Tokamak with in situ magnetohydrodynamic generation of toroidal magnetic field  

Science.gov (United States)

A tokamak apparatus includes an electrically conductive metal pressure vessel for defining a chamber and confining liquid therein. A liner disposed within said chamber defines a toroidal space within the liner and confines gas therein. The metal vessel provides an electrically conductive path linking the toroidal space. Liquid metal is forced outwardly through the chamber outside of the toroidal space to generate electric current in the conductive path and thereby generate a toroidal magnetic field within the toroidal space. Toroidal plasma is developed within the toroidal space about the major axis thereof.

Schaffer, Michael J. (San Diego, CA) [San Diego, CA

1986-01-01

39

High magnetic field generation for laser-plasma experiments  

International Nuclear Information System (INIS)

An electromagnetic solenoid was developed to study the effect of magnetic fields on electron thermal transport in laser plasmas. The solenoid, which is driven by a pulsed power system supplying 30 kJ, achieves magnetic fields of 13 T. The field strength was measured on the solenoid axis with a magnetic probe and optical Zeeman splitting. The measurements agree well with analytical estimates. A method for optimizing the solenoid design to achieve magnetic fields exceeding 20 T is presented

2006-11-01

40

Modeling and Measurement of Ocean Generated Magnetic Fields  

Science.gov (United States)

Motion of conductive seawater through the earth's magnetic field will produce magnetic fields. Magnetic fields from motions such as ocean waves and swells are detectable near the ocean's surface but decay rapidly with distance. Non-linear internal waves (NLIWs) generated by mechanisms such as tides over bathymetric features have been predicted to produce magnetic anomalies of .1-1 nT at altitudes of ~ 100 m above the surface (Chave, 1986) due to the large volumes of coherently moving water. An experiment was performed in 2009 by the Defense Research and Development Canada (DRDC) and the US Naval Research Laboratory (NRL) to see if magnetic signatures predicted from oceanographic measurements could be detected by airborne and ocean bottom mounted magnetometers. The test was conducted near the shelf-break off the coast of New Jersey where NLIWs have been observed. Oceanographic measurements were collected by a set of bottom-mounted ADCPs, towed C-T sensors mounted on a "SCANFISH" tow-body, and a hull-mounted ADCP. Magnetic measurements consisted of total-field magnetometers co-located with the bottom mounted ADCPs, three magnetic base-stations (total field and vector) in New Jersey for geomagnetic noise cancellation, and magnetometers aboard two aircraft ( a Canadian National Research Council Convair 580 and the NRL P-3) flown simultaneously with a 20-30 second separation ( corresponding to 2-3 km) along a repeat track over the bottom-mounted sensors. The multiple aircraft and repeat tracks were intended to remove the spatially stationary geologic component. The time-varying geomagnetic signal was extrapolated from the magnetic base-stations to the aircraft measurements. Both aircraft had high quality magnetometers and magnetic-field compensation systems based on co-located vector magnetometers and kinematic GPS. The Convair had two magnetometer and compensation systems mounted in wing-pods with a base-line of ~ 32 m that allowed the calculation of a cross-track gradient. Total-field compensated and edited data from each aircraft and the magnetic base-station data were low-pass filtered and sub-sampled to 4Hz for analysis. Data from the magnetic base-stations exhibit good coherence, as do the data from the ocean-bottom magnetometers. After correction for the geomagnetic component, the two aircraft residuals matched quite closely in both amplitude and phase in many places, but in other places the phase match was poor. This produced an overall poor coherence between the two residuals. However, cross-spectral analysis showed that there was a statistical correlation between the two aircraft residuals in the frequency band 0.02-0.05 Hz (5000-2000 m wavelength for an aircraft flying at 100 m/s). Both the amplitude (0.1-0.2 nT) and wavelength were consistent with predictions computed from the 3-D water velocities and conductivity from the ADCP using a simple model. The predicted undersea magnetic fields correlated well with the measured undersea magnetometer fields at times, but they rarely matched at the "wiggle-for-wiggle" level. More often, it was the statistics that correlated well.

Liang, R.; Avera, W. E.; Nelson, J.; Brozena, J. M.

2011-12-01

 
 
 
 
41

Glutathione production using magnetic fields generated by magnets  

Directory of Open Access Journals (Sweden)

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.

Lucielen Oliveira dos Santos

2012-12-01

42

Glutathione production using magnetic fields generated by magnets  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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.

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

43

Generation and evolution of magnetic fields in the gravitomagnetic field of a Kerr Black Hole  

CERN Document Server

I study the generation and evolution of magnetic fields in the plasma surrounding a rotating black hole. Attention is focused on effects of the gravitomagnetic potential. The gravitomagnetic force appears as battery term in the generalized Ohm's law. The generated magnetic field should be stronger than fields generated by the classical Biermann battery. The coupling of the gravitomagnetic potential with electric fields appears as gravitomagnetic current in Maxwell's equations. In the magnetohydrodynamic induction equation, this current re-appears as source term for the poloidal magnetic field, which can produce closed magnetic structures around an accreting black hole. In principle, even self-excited axisymmetric dynamo action is possible, which means that Cowling's anti dynamo theorem does not hold in the Kerr metric. Finally, the structure of a black hole driven current is studied.

Khanna, R

1999-01-01

44

Particle Acceleration, Magnetic Field Generation and Emission from Relativistic Jets  

Science.gov (United States)

Nonthermal radiation observed from astrophysical systems containing relativistic jets and shocks, e.g., active galactic nuclei (AGNs), gamma-ray bursts (GRBs), supernova remnants, and Galactic microquasar systems usually have power-law emission spectra. Fermi acceleration is the mechanism usually assumed for the acceleration of particles in astrophysical environments. Recent PIC simulations using injected relativistic electron-ion (electro-positron) jets show that particle acceleration occurs within the downstream jet, rather than by the scattering of particles back and forth across the shock as in Fermi acceleration. 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 spectral 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. We will review recent PIC simulations of relativistic jets and try to make a connection with observations.

Nishikawa, K.-I.; Hardee, P.; Hededal, C.; Mizuno, Yosuke; Fishman, G. Jerry; Hartmann, D. H.

2006-01-01

45

Magnetocaloric effect: permanent magnet array for generation of high magnetic fields  

Science.gov (United States)

The magnetocaloric effect (MCE), the heating or cooling of magnetic materials in a magnetic field, is unusually large in the Gd_5(Si_xGe_1-x)4 alloy system. Normally the maximum in the MCE occurs at the Curie temperature (Tc) because the spin entropy change is a maximum. By suitable selection of the composition of this alloy system the Curie temperature can be changed over the range 25 K for x = 0 to 340 K for x =1, and the composition range around x = 0.5 exhibits the largest magnetocaloric effect. In order to increase the amount of heat exchanged the change in applied magnetic field should be as large as possible, and in this research values above 1.5 Tesla are suggested. We have studied a permanent magnet array based on NdFeB, which with a remanent magnetization of only 1.2 Tesla can still generate a magnetic flux density, or magnetic induction B of 2-3 Tesla. In order to generate the high magnetic induction in the absence of a power supply, a modified hollow cylindrical permanent magnet array (HCPMA) has been designed to produce the required strength of magnetic field. Soft magnetic materials including permalloy (NiFe) were used for focusing the magnetic field in the central region. The magnitude of the magnetic flux density at the center was about 2 Tesla. The magnitude and homogeneity of the magnetic field for this design are comparable with the conventional C-shaped yoke and HCPMA. This can be easily adapted for a low power rotary system in which the magnetocaloric material can be exposed alternately to high and low magnetic fields so that it can accept and reject heat from its surroundings.

Lee, Seong-Jae; Kenkel, John; Jiles, David

2002-03-01

46

Internal split field generator  

Energy Technology Data Exchange (ETDEWEB)

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.

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

2012-01-03

47

Laser light absorption and harmonic generation due to self-generated magnetic fields  

International Nuclear Information System (INIS)

It is shown that self-generated magnetic fields can play a significant role in laser light absorption. Even normally incident light will then be resonantly absorbed. Computer simulations and theoretical estimates for this absorption and the concomitant harmonic generation are given for parameters characteristic of some recent experiments

1976-11-12

48

High Magnetic Field Generation for Laser-Plasma Experiments.  

Science.gov (United States)

An electromagnetic solenoid was developed to study the effect of magnetic fields on electron thermal transport in laser plasmas. The solenoid, which is driven by a pulsed power system suppling 30 kJ, achieves magnetic fields of 13 T. The field strength wa...

B. B. Pollock D. Price D. H. Froula J. Bower J. Satariano J. S. Ross P. F. Davis S. Fulkerson

2006-01-01

49

Generation of large scale magnetic fields by coupling to curvature and dilaton field  

CERN Multimedia

We investigate the generation of large scale magnetic fields in the universe from quantum fluctuations produced in the inflationary stage. By coupling these quantum fluctuations to the dilaton field and Ricci scalar, we show that the magnetic fields with the strength observed today can be produced. We consider two situations: First, the evolution of dilaton ends at the onset of the reheating stage. Second, the dilaton continues its evolution after reheating and then decays. In both cases, we come back to the usual Maxwell equations after inflation and then calculate present magnetic fields.

Zavareh, A Akhtari; Mirza, B

2007-01-01

50

Generation of the large scale magnetic fields by coupling to curvature and dilaton field  

Directory of Open Access Journals (Sweden)

Full Text Available  We investigate the generation of large scale magnetic fields in the universe from quantum fluctuations that are produced in the inflationary stage. By coupling these quantum fluctuations to the dilaton field and Ricci scalar, we show that the magnetic fields with the strength observed today can be produced. We consider two situations. First, the evolution of dilaton ends by starting the reheating stage. Second, the dilaton continues its evolution after reheating and then decays. We here consider the first case. In both cases, we come back to the usual Maxwell equations after inflation and then calculate present magnetic fields.

A. Akhtari Zavareh

2006-06-01

51

Generation of large scale magnetic fields by coupling to curvature and dilation field  

International Nuclear Information System (INIS)

We investigate the generation of large scale magnetic fields in the universe from quantum fluctuations produced in the inflationary stage. By coupling these quantum fluctuations to the dilaton field and Ricci scalar, we show that the magnetic fields with the strength observed today can be produced. We consider two situations: First, the evolution of dilaton ends at the onset of the reheating stage. Second, the dilaton continues its evolution after reheating and then decays. In both cases, we come back to the usual Maxwell equations after inflation and then calculate present magnetic fields. (author)

2007-05-01

52

Generation of the large scale magnetic fields by coupling to curvature and dilaton field  

International Nuclear Information System (INIS)

We investigate the generation of large scale magnetic fields in the universe from quantum fluctuations that are produced on the inflationary stage. By coupling these quantum fluctuations to the dilation field and Ricci scalar, we show that the magnetic fields with the strength observed today can be produced. We consider two situations. First, the evolution of dilation ends by starting the reheating stage. Second, the dila ton continues its evolution after reheating and then decays. We here consider the first case. In both cases, we come back to the usual Maxwell equations after inflation and then calculate present magnetic fields

2006-01-01

53

Poloidal magnetic field generation in laser plasma interaction  

International Nuclear Information System (INIS)

The generation of poloidal magnetic field in an inhomogeneous cold, collisionless plasma by an elliptically polarized Gaussian laser beam is presented. It has been shown that self generated magnetic field (SGMF) of the order of mega Gauss is introduced by the laser inhomogeneity effect even for a normal incident Gaussian beam in both uniform and non-uniform plasmas and scales as I0?. Numerically it has been estimated that for homogeneous laser beam (using focal spot radius ? density scale length), I0?1020 Wm-2, ??1.06 ?m, incident angle ?0?22.5 degree, n0?5 x 1026 m-3, the poloidal SGMF (Bx)?0.115 MG, whereas for CO2 laser (??10.6 ?m) with I0?1018 Wm-2, n0?5 x 1024 m-3, the authors get a Bx?1.4 tesla. For inhomogeneous laser beam incident almost normally the authors get an induced poloidal SGMG?0.39 MG for I0?1020 Wm-2 and ??1.06 ?m which is shown as independent of the density profile structure

1999-01-01

54

Magnetic energy dissipation and mean magnetic field generation in planar convection driven dynamos  

CERN Document Server

A numerical study of dynamos in rotating convecting plane layers is presented which focuses on magnetic energies and dissipation rates, and the generation of mean fields (where the mean is taken over horizontal planes). The scaling of the magnetic energy with the flux Rayleigh number is different from the scaling proposed in spherical shells, whereas the same dependence of the magnetic dissipation length on the magnetic Reynolds number is found for the two geometries. Dynamos both with and without mean field exist in rapidly rotating convecting plane layers.

Tilgner, A

2014-01-01

55

On Generation of magnetic field in astrophysical bodies  

CERN Multimedia

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.

Verma, M K

2001-01-01

56

Magnetic-moment field generation in the reflection region in a cold magnetized plasma  

Energy Technology Data Exchange (ETDEWEB)

Magnetization due to a magnetic moment contributes to the non-oscillating magnetic field in a plasma. The dynamics of classically bound electrons in the presence of an applied circularly polarized strong electromagnetic field in the reflection region generates this field. The special case of its resonant generation when the frequency of a right circularly polarized wave is equal to the ion gyration frequency is studied here. Another source of non-oscillating magnetization is the interaction of electromagnetic fields, including fields in the Alfven-wave frequency range, with a cold collisionless fully ionized magnetized plasma also in the reflection region. The induced field from a left circularly polarized field at Alfven-wave frequencies is paramagnetic, inversely proportional to the square of the ambient field and independent of the mass per particle of both electrons and ions. The induced field from a right circularly polarized field at Alfven-wave frequencies is diamagnetic, inversely proportional to the cube of the ambient field and depends directly on the plasma mass density. (author).

Das, C.; Bera, B.; Chakraborty, B.; Khan, M. (Jadavpur Univ., Calcutta (India). Dept. of Mathematics)

1993-10-01

57

Magnetic field generation by surface plasma wave over a rippled metallic surface  

Energy Technology Data Exchange (ETDEWEB)

A surface plasma wave propagating over the rippled metallic surface produces static magnetic field via nonlinear coupling of electron velocity with density ripple. The generated magnetic field shows a resonant enhancement at particular values of ripple number. Magnetic field strength is also sensitive to plasma density and decreases at lower plasma densities. The generated magnetic field over a rippled metallic field is larger by an order of magnitude as compared to a planar metallic surface.

Parashar, J. [Department of Applied Physics, Samrat Ashok Technological Institute, Vidisha (M.P.) 464001 (India)

2013-04-15

58

Projectile-power-compressed magnetic-field pulse generator  

International Nuclear Information System (INIS)

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

1983-06-13

59

Langmuir turbulence equations with the self-generated magnetic field  

Energy Technology Data Exchange (ETDEWEB)

Starting from the dynamical plasma equations with the help of relaxed Zakharov simplification assumptions, and through taking use of the time-averaged two-time-scale two-fluid plasma description, the Zakharov equations (ZE) are generalized to contain the self-generated magnetic field. The generalized Zakharov equations (GZE) are a set of three coupled equations and of seventh-order nonlinearity with an amplification factor in almost all nonlinear terms of GZE. The conclusion that electron nonlinearities other than those appearing in ZE are not important and that the ion nonlinearities may be important when Langmuir turbulence level is fairly high, which was obtained through using both particle-in-cell (PIC) simulations and numerically integrating ZE by Newman [ital et] [ital al]. [Phys. Fluids B [bold 2], 2600 (1990)] and Clark [ital et] [ital al]. [Phys. Fluids B [bold 4], 708 (1992)], is demonstrated by the theoretical analysis given in this paper.

Li, L.H. (Purple Mountain Observatory, Academia Sinica, Nanjing (China))

1993-02-01

60

Inflationary susceptibilities, duality and large-scale magnetic fields generation  

CERN Multimedia

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

Giovannini, Massimo

2013-01-01

 
 
 
 
61

Magnetic flux concentrations from dynamo-generated fields  

CERN Document Server

The mean-field theory of magnetized stellar convection gives rise to the two possibility of distinct instabilities: the large-scale dynamo instability, operating in the bulk of the convection zone, and a negative effective magnetic pressure instability (NEMPI) operating in the strongly stratified surface layers. The latter might be important in connection with magnetic spot formation, but the growth rate of NEMPI is suppressed with increasing rotation rates, although recent direct numerical simulations (DNS) have shown a subsequent increase in the growth rate. We examine quantitatively whether this increase in the growth rate of NEMPI can be explained by an alpha squared mean-field dynamo, and whether both NEMPI and the dynamo instability can operate at the same time. We use both DNS and mean-field simulations (MFS) to solve the underlying equations numerically either with or without an imposed horizontal field. We use the test-field method to compute relevant dynamo coefficients. DNS show that magnetic flux ...

Jabbari, Sarah; Losada, Illa R; Kleeorin, Nathan; Rogachevskii, Igor

2014-01-01

62

Dynamo-generated magnetic fields in fast rotating single giants  

CERN Multimedia

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.

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

2009-01-01

63

Z: A Fast Pulsed Power Generator for Ultra-High Magnetic Field Generation  

Energy Technology Data Exchange (ETDEWEB)

Advances in fast, pulsed-power technologies have resulted in the development of very high current drivers that have current rise times - 100 ns. The largest such pulsed power drive r today is the new Z accelerator located at Sandia National Laboratories in Albuquerque, New Mexico. Z is capable of delivering more than 20 MA with a time-to-peak of 105 ns to low inductance (- 1 nH)loads. Such large drivers are capable of directly generating magnetic fields approaching 3 kT in small, 1 -cm3, volumes. In addition to direct field generation, Z can be used to compress an applied, axial seed field with a plasma. Flux compression scheme~: are not new and are, in fact, the basis of all explosive flux-compression generators but we propose the use of plasma armatures rather than solid, conducting armatures. We will present experimental results from the Z accelerator in which magnetic fields - 2 kT are generated and measured with several diagnostics. Issues such as energy loss in solid conductors and dynamic response of current-carrying conductors to very large magnetic fields will be reviewed in context with Z experiments. We will describe planned flux-compression experiments that are expected to create the highest-magnitude uniform-field volumes yet attained in the laboratory.

Asay, J.R.; Bailey, J.E.; Bernard, M.A.; Hall, C.A.; McDaniel, D.H.; Spielman, R.B.; Struve, K.W.; Stygar, W.A.

1998-11-04

64

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Shiromoto, Yuki; Susa, Hajime; Hosokawa, Takashi

2014-01-01

65

Self-Collimation and Magnetic Field Generation of Astrophysical Jets  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A novel model for collimation and transport of electron-positron-ion jets is presented. Analytical results show that the filamentary structures can be sustained by self-induced toroidal magnetic fields permeating through the filaments, whose widths significantly expand in the pair-dominant regimes. The magnetic field strength reflects a characteristic of equipartition of excess kinetic energy of the jets. It is also shown that growth of the hoselike instability is strongly s...

Honda, Mitsuru; Honda, Yasuko S.

2002-01-01

66

Particle Acceleration, Magnetic Field Generation in Relativistic Shocks  

Science.gov (United States)

Shock acceleration is an ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created in the shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating through an ambient plasma with and without initial magnetic fields. We find only small differences in the results between no ambient and weak ambient parallel magnetic fields. Simulations show that the Weibel instability created in the collisionless shock front accelerates particles perpendicular and parallel to the jet propagation direction. New simulations with an ambient perpendicular magnetic field show the strong interaction between the relativistic jet and the magnetic fields. The magnetic fields are piled up by the jet and the jet electrons are bent, which creates currents and displacement currents. At the nonlinear stage, the magnetic fields are reversed by the current and the reconnection may take place. Due to these dynamics the jet and ambient electron are strongly accelerated in both parallel and perpendicular directions.

Nishikawa, Ken-Ichi; Hardee, P.; Hededal, C. B.; Richardson, G.; Sol, H.; Preece, R.; Fishman, G. J.

2005-01-01

67

Effects of self-generated magnetic field on rayleigh-taylor instability  

International Nuclear Information System (INIS)

Scaling of the self-generated magnetic field generated by Rayleigh-Taylor instability and a new aspect of the instability in the acceleration of the laser fusion target are presented. The scaling is derived from linear analysis and compared with the simulation result. Electron heat conduction affected by the self-generated magnetic field causes the configuration change of surface perturbation, higher mode generation and steepening of the field. The field restrains the heat flux and produces a temperature gradient nonparallel to the density gradient in plasmas. This thermoelectric current generates a magnetic field larger than the initial field with certain parameters. These phenomena are observed in the hydrodynamic simulations. (author)

2002-01-01

68

The spontaneous generation of magnetic and chromomagnetic fields at high temperature in the standard model  

International Nuclear Information System (INIS)

The spontaneous generation of magnetic and chromomagnetic fields at high temperature is investigated in the standard model. The consistent effective potential including the one-loop and the daisy diagrams of all boson and fermion fields is calculated. The mixing of the generated fields due to the quark loop diagram is studied in detail. It is found that the quark contribution increases the magnetic and chromomagnetic field strengths as compared with the separate generation of fields. The magnetized vacuum state is stable due to the magnetic gauge field masses included in the daisy diagrams. Some applications of the results obtained are discussed. (orig.)

2002-09-01

69

The spontaneous generation of magnetic and chromomagnetic fields at high temperature in the Standard Model  

CERN Document Server

The spontaneous generation of the magnetic and chromomagnetic fields at high temperature is investigated in the Standard Model. The consistent effective potential including the one-loop and the daisy diagrams of all boson and fermion fields is calculated. The mixing of the generated fields due to the quark loop diagram is studied in detail. It is found that the quark contribution increases the magnetic and chromomagnetic field strengths as compared with the separate generation of fields. The magnetized vacuum state is stable due to the magnetic gauge field masses included in the daisy diagrams. Some applications of the results obtained are discussed.

Demchik, V I

2001-01-01

70

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Doi, Kentaro; Susa, Hajime

2011-01-01

71

System for generating double-pulsed magnetic fields in a kicker magnet  

International Nuclear Information System (INIS)

Two bunched beams are accelerated in the 1A ring of JHF. They are extracted for meson experiments and for neutron experiments successively. Therefore, the extraction kicker magnet should generate double-pulsed magnetic fields at intervals of about 100 ?sec, with a repetition rate of 50 Hz. In order to test the feasibility of generating double pulses, we used two sets of thyratron housings and a kicker magnet for the KEK-PS-extraction system, which has an impedance of 25 ?. Using a thyratron cathode-loaded system, the first firing induces a second misfire by a rapid voltage drop of the second thyratron cathode. A thyratron anode-loaded system does not have the above-mentioned trouble, and has succeeded in generating the desired double pulses with half of the voltage required for the usual operation of JHF (? 80kV). (author)

1991-03-01

72

Higher 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 Superconducting Super Collider (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. Multipole magnetization field components have been measured within the HERA storage ring dipole magnets. Calculations of these components using the SCMAG04 code, which agree substantially with the measured multipoles, are presented in the report. As a result, in the proposed continuous correction winding for the SSC, dipoles have been replaced with lumped correction elements every six dipole magnets (about 120 meters apart). Nested lumped correction elements will also produce undesirable higher magnetization multipoles. This report shows a method by which the higher multipole generated by nested correction elements can be identified. (author)

1990-09-01

73

Magnetic guide field generation in collisionless current sheets  

Directory of Open Access Journals (Sweden)

Full Text Available In thin (?< few ?i collisionless current sheets in a space plasma like the magnetospheric tail or magnetopause current layer, magnetic fields can grow from thermal fluctuation level by the action of the non-magnetic Weibel instability (Weibel, 1959. The instability is driven by the counter-streaming electron inflow from the "ion diffusion" (ion inertial Hall region into the inner current (electron inertial region after thermalisation by the two-stream instability. Under magnetospheric tail conditions it takes ~50 e-folding times (~100 s for the Weibel field to reach observable amplitudes |bW|~1 nT. In counter-streaming inflows these fields are of guide field type.

W. Baumjohann

2010-03-01

74

Magnetic noises generated by plants in microgravity: effect of external magnetic fields.  

Science.gov (United States)

Magnetic Noises Generated by Plants in Microgravity, Effect of External Magnetic Field. N. Bogatina(1), N. Sheykina(1), E. Kordyum(2). (1) B.Verkin Institute for Low Temperature Physics&Engineering of National Academy of Sciences of Ukraine, Kharkov, Ukraine (2) N.Cholodny Institute of Botany of National Academy of Sciences of Ukraine, Kiev, Ukraine. e-mail:bogatina@ilt.kharkov.ua/Fax: 38-0572-322370. The object of the work is to determine the correlation between the magnetic noises generated by plants and accelaration value during their development in microgravity. The amplitude of magnetic noise spectral density will be mesured. Its dependence on the magnitude of gravity accelaration and magnitudes of static and alternating magnetic fields is supposed to reflect the mechanisms of gravi- and magnitopercrption. We shall try to answer the guestion whether the same mechanism or different mechanisms are responsible for gravi- and magnitopercrption. The gravitropic reaction of plants is needed to be studied simultaneously with observation of magnetic noises. The measurements in microgravity have to be fulfilled by a flux-gate magnetometer connected with Philips spectroanalyser There are two directions of experiments. The first one is experiments that will be carried out on Earth under the conditions of weakening of gravitational force. The preliminary parameters of the required magnetic fields have to be determined in these experiments. The second one is the same experiment in the space. These experiments are supposed to allow us to define the mechanisms of a gravitropic reaction of plants because any motion of ions ( indolil-acetic ions, for instance) is accompanied by an increase of magnetic noise. The experimental results obtained under onGround conditions by using the superconducting technique wwithout weakening the weight force are disscussed. .

Bogatina, N.; Sheykina, N.; Kordyum, E.

75

Magnetic field generation in Rayleigh-Taylor unstable inertial confinement fusion plasmas.  

Science.gov (United States)

Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion implosions are expected to generate magnetic fields. A Hall-MHD model is used to study the field generation by 2D single-mode and multimode RTI in a stratified two-fluid plasma. Self-generated magnetic fields are predicted and these fields grow as the RTI progresses via the ?n(e)×?T(e) term in the generalized Ohm's law. Scaling studies are performed to determine the growth of the self-generated magnetic field as a function of density, acceleration, Atwood number, and perturbation wavelength. PMID:22680725

Srinivasan, Bhuvana; Dimonte, Guy; Tang, Xian-Zhu

2012-04-20

76

A simple mechanism for the generation of Earth's magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Based on the ideal gas model, the dielectric polarization of mantle is achieved, the physical-mathematical model is constructed and the estimate calculation of a dipole of Earth's magnetic field with the considering of rotation, parameters of density and temperature, potential of ionization and static dielectric constant (relative dielectric permittivity), chemical compound of substance in Earth's mantle is executed.

Styazhkin, Oleg V.

2011-01-01

77

Internal Magnetic Field Measurements in STX Generated FRCs  

Science.gov (United States)

The internal magnetic field probes installed in the STX experiment at the Redmond Plasma Physics laboratory are designed to provide a one dimensional internal magnetic field profile of a 25 eV 10^19 m-3 FRC. The probe consists of 24 1cm × 1mm 8 turn coils interconnected like a chain to provide information on the RMF field components. This probe can be swept through the vacuum chamber to provide field information for different points throughout the FRC. The coils themselves are made with one mil magnet wire (half mil insulation). Structural and thermal support for the field coils is provided by a 53 mil ID × 78 mil OD berylium oxide tube capped with a boron nitride tip. Berylium oxide is an insulator with good thermal diffusivity/ablation properties. Calculations and test results indicate minimal perturbations to the plasma caused by the probe. Information on the construction methods employed as well as physical and external electrical design will be presented along with representative experimental results. This work is funded by the USDOE. www.aa.washington.edu/AERP/RPPL

Andreason, Samuel; Miller, Ken; Slough, John

1999-11-01

78

Geometrical generation of cosmic magnetic fields within standard electromagnetism  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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.

Christos G., Tsagas; Alejandra, Kandus.

79

Apparatus for unilateral generation of a homogeneous magnetic field  

Energy Technology Data Exchange (ETDEWEB)

An apparatus for unilaterally producing a substantially homogeneous magnetic field. The apparatus includes two circular electromagnet coils, a small coil and a large coil, which are coaxial with one another and which are separated by a distance equal to one-half the difference in the radius of the two coils. By appropriate selection of electrical currents, which are passed through the coil in opposite directions, a region of homogeneous magnetic field is formed. This region is centered on the common axis of the two coils, at a point on the axis which is at a distance from the small coil equal to one-half the radius of the small coil, and which is on the opposite side of the small coil from the large coil. The apparatus has particular application in the field of diagnostic medical NMR and other NMR applications.

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

1988-01-01

80

Ultra-High Intensity Magnetic Field Generation in Dense Plasma  

Energy Technology Data Exchange (ETDEWEB)

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.

Fisch, Nathaniel J

2014-01-08

 
 
 
 
81

SSWL and BWL: finite element models of compressed magnetic field current generators  

Energy Technology Data Exchange (ETDEWEB)

Documentation is presented for two new computer codes modeling the behavior of compressed magnetic field current generators. Code output results for the typical generator configurations are presented and compared to experimental results. (auth)

Tucker, T.J.; Leeman, J.E.

1976-01-01

82

Magnetic-Field Generation and Amplification in an Expanding Plasma  

Science.gov (United States)

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 di, it is shown that B˜di/L, consistent with the Biermann battery effect. However, for large L/di, 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 ??100), independent of L. The magnetic energy spectra below the electron Larmor radius scale are well fitted by the power law with slope -16/3, as predicted by Schekochihin et al. [Astrophys. J. Suppl. Ser. 182, 310 (2009)].

Schoeffler, K. M.; Loureiro, N. F.; Fonseca, R. A.; Silva, L. O.

2014-05-01

83

The generation of the earth magnetic field. Pt. 1  

International Nuclear Information System (INIS)

The only possibility to produce the magnetic field of the earth is the dynamo-effect of a flow in the conducting fluid core of the earth. Theoretically it is possible to construct detailed models for the geodynamo, although only first attempts are made in this direction. The first part of this paper deals with the kinematics of the dynamo problem in general and particularly with the homogenious dynamo. (orig.)

1976-10-01

84

Dynamical mass generation in strong coupling Quantum Electrodynamics with weak magnetic fields  

CERN Multimedia

We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics in the presence of magnetic fields using Schwinger-Dyson equations. We show that, contrary to the case where the magnetic field is strong, in the weak field limit eB << m(0)^2, where m(0) is the value of the dynamically generated mass in the absence of the magnetic field, masses are generated above a critical value of the coupling and that this value is the same as in the case with no magnetic field. We carry out a numerical analysis to study the magnetic field dependence of the mass function above critical coupling and show that in this regime the dynamically generated mass and the chiral condensate for the lowest Landau level increase proportionally to (eB)^2.

Ayala, A; Raya, A; Rojas, E; Ayala, Alejandro; Bashir, Adnan; Raya, Alfredo; Rojas, Eduardo

2006-01-01

85

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Herndon, J. Marvin

2009-01-01

86

Wake field generation and nonlinear evolution in a magnetized electron-positron-ion plasma  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The nonlinear propagation of a circularly polarized electromagnetic (CPEM) wave in a strongly magnetized electron-positron-ion plasma is investigated. Two coupled equations describing the interaction between a high-frequency CPEM wave and the low-frequency electrostatic wake field are derived. It is found that the generation of the wake fields partly depends on the presence of the ion species and the external magnetic field. The wake field generation in turn leads to deceleration and frequenc...

Shukla, P. K.; Brodin, G.; Marklund, M.; Stenflo, Lennart

2008-01-01

87

Observation of magnetic field generation via the Weibel instability in interpenetrating plasma flows  

CERN Document Server

As the ejecta from supernovae or other energetic astrophysical events stream through the interstellar media, this plasma is shaped by instabilities that generate electric and magnetic fields. Among these instabilities, the Weibel filamentation instability plays a particularly important role, as it can generate significant magnetic fields in an initially un-magnetized medium. It is theorized that these Weibel fields are responsible for the observed gamma-ray burst light curve, particle acceleration in shock waves, and for providing seed fields for larger-scale cosmological magnetic structures. While the presence of these instability-generated fields has been inferred from astrophysical observation and predicted in simulation, observation in experiments is challenging. Here we report direct observation of well-organized, large-amplitude, filamentary magnetic fields associated with the Weibel instability in a scaled laboratory experiment. The experimental images, captured with proton radiography, are shown to be...

Huntington, C M; Ross, J S; Zylstra, A B; Drake, R P; Froula, D H; Gregori, G; Kugland, N L; Kuranz, C C; Levy, M C; Li, C K; Meinecke, J; Morita, T; Petrasso, R; Plechaty, C; Remington, B A; Ryutov, D D; Sakawa, Y; Spitkovsky, A; Takabe, H; Park, H -S

2013-01-01

88

Self generating magnetic field of superconductor under the cooling process; Chodendotai reikyakuji no jiko hassei jikai  

Energy Technology Data Exchange (ETDEWEB)

When we try to form a very low magnetic field environment using a superconducting wall like a cylinder, we expect magnetic flux is expelled from the superconductor under the cooling process by Meissner effect. It has been believed that, at least, if we cool a superconductor in a zero field environment, the superconductor has no magnetic fluxsoid. However, we found that, in actual, a self generating magnetic flux under the cooling process result in a magnetic field so larger than we expect to form a very low magnetic field environment. In this paper, we describe experiments and the mechanism of the self- generation of magnetic flux under the cooling process. 10 refs., 8 figs., 2 tabs.

Matsuba, H.; Irisawa, D.; Yahara, A.; Imai, K. [The Furukawa Electric Co. Ltd., Tokyo (Japan)

1998-10-01

89

The spontaneous generation of magnetic fields at high temperature in a supersymmetric theory  

CERN Document Server

The spontaneous generation of magnetic and chromomagnetic fields at high temperature in the minimal supersymmetric standard model (MSSM) is investigated. The consistent effective potential including the one-loop and the daisy diagrams of all bosons and fermions is calculated and the magnetization of the vacuum is observed. The mixing of the generated fields due to the quark and s-quark loop diagrams and the role of superpartners are studied in detail. It is found that the contribution of these diagrams increases the magnetic and chromomagnetic field strengths as compared with the case of a separate generation of fields. The magnetized vacuum state is found to be stable due to the magnetic masses of gauge fields included in the daisy diagrams. Applications of the results obtained are discussed. A comparison with the standard model case is done.

Demchik, V I

2003-01-01

90

The spontaneous generation of magnetic fields at high temperature in a supersymmetric theory  

International Nuclear Information System (INIS)

The spontaneous generation of magnetic and chromomagnetic fields at high temperature in the minimal supersymmetric standard model is investigated. The consistent effective potential including the one-loop and the daisy diagrams of all bosons and fermions is calculated and the magnetization of the vacuum is observed. The mixing of the generated fields due to the quark and s-quark loop diagrams and the role of superpartners are studied in detail. It is found that the contribution of these diagrams increases the magnetic and chromomagnetic field strengths as compared with the case of a separate generation of fields. The magnetized vacuum state is found to be stable due to the magnetic masses of gauge fields included in the daisy diagrams. Applications of the results obtained are discussed. A comparison with the standard model case is given. (orig.)

2003-04-01

91

Magnetic Field Generation in Core-Sheath Jets via the Kinetic Kelvin-Helmholtz Instability  

CERN Multimedia

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 which 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 transverse structure similar to that produced by the Weibel instability.

Nishikawa, K -I; Dutan, I; Niemiec, J; Medvedev, M; Mizuno, Y; Meli, A; Sol, H; Zhang, B; Pohl, M; Hartmann, D H

2014-01-01

92

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

Science.gov (United States)

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 ma...

M. A. Green

1990-01-01

93

Dynamical mass generation in QED with magnetic fields: arbitrary field strength and coupling constant  

CERN Multimedia

We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics, in the presence of magnetic fields of arbitrary strength, by solving the Schwinger-Dyson equation (SDE) for the fermion self-energy in the rainbow approximation. We employ the Ritus eigenfunction formalism which provides a neat solution to the technical problem of summing over all Landau levels. It is well known that magnetic fields catalyze the generation of fermion mass m for arbitrarily small values of electromagnetic coupling \\alpha. For intense fields it is also well known that m \\propto \\sqrt eB. Our approach allows us to span all regimes of parameters \\alpha and eB. We find that m \\propto \\sqrt eB provided \\alpha is small. However, when \\alpha increases beyond the critical value \\alpha_c which marks the onslaught of dynamical fermion masses in vacuum, we find m \\propto \\Lambda, the cut-off required to regularize the ultraviolet divergences. Our method permits us to verify the results available in l...

Rojas, Eduardo; Bashir, Adnan; Raya, Alfredo

2008-01-01

94

Octupolar out-of-plane magnetic field structure generation during collisionless magnetic reconnection in a stressed X-point collapse  

CERN Document Server

The out-of-plane magnetic field, generated by fast magnetic reconnection, during collisionless, stressed $X$-point collapse, was studied with a kinetic, 2.5D, fully electromagnetic, relativistic particle-in-cell numerical code, using both closed (flux conserving) and open boundary conditions on a square grid. It was discovered that the well known quadrupolar structure in the out-of-plane magnetic field gains four additional regions of opposite magnetic polarity, emerging near the corners of the simulation box, moving towards the $X$-point. The emerging, outer, magnetic field structure has opposite polarity to the inner quadrupolar structure, leading to an overall octupolar structure. Using Ampere's law and integrating electron and ion currents, defined at grid cells, over the simulation domain, contributions to the out-of-plane magnetic field from electron and ion currents were determined. The emerging regions of opposite magnetic polarity were shown to be the result of ion currents. Magnetic octupolar struct...

von der Pahlen, J Graf

2014-01-01

95

Quasistatic magnetic fields generated by a nonrelativistic intense laser pulse in uniform underdense plasma  

International Nuclear Information System (INIS)

Quasistatic magnetic fields generated by nonrelativistic intense linearly polarized (LP) and circularly polarized (CP) laser pulses in an initially uniform underdense plasma in the collision-dominated limit are investigated analytically. Using a selfconsistent analytical model, we perform a detailed derivation of quasistatic magnetic fields in the laser pulse envelope in the collision-dominated limit to obtain exact analytical expressions for magnetic fields and discuss the dependence of magnetic fields on laser and plasma parameters. Equations for quasistatic magnetic fields including both axial component Bz and the azimuthal one B? are derived simultaneously from such a selfconsistent model. The dependence of quasistatic magnetic field on incident laser intensity, transverse focused radius of laser pulse, electron density and electron temperature is discussed. (cross-disciplinary physics and related areas of science and technology)

2010-07-01

96

Precise Measurement of a Magnetic Field Generated by the Electromagnetic Flux Compression Technique  

CERN Document Server

The precision of the values of a magnetic field generated by electromagnetic flux compression was investigated in ultra-high magnetic fields of up to 700 T. In an attempt to calibrate the magnetic field measured by pickup coils, precise Faraday rotation (FR) measurements were conducted on optical (quartz and crown) glasses. A discernible "turn-around" phenomenon was observed in the FR signal as well as the pickup coils before the end of a liner implosion. We found that the magnetic field measured by pickup coils should be corrected by taking into account the high-frequency response of the signal transmission line. Near the peak magnetic field, however, the pickup coils failed to provide reliable values, leaving the FR measurement as the only method to precisely measure an extremely high magnetic fields.

Nakamura, D; Matsuda, Y H; Takeyama, S

2013-01-01

97

Nonlinear Generation of shear flows and large scale magnetic fields by small scale  

Science.gov (United States)

EGU2009-233 Nonlinear Generation of shear flows and large scale magnetic fields by small scale turbulence in the ionosphere by G. Aburjania Contact: George Aburjania, g.aburjania@gmail.com,aburj@mymail.ge

Aburjania, G.

2009-04-01

98

Generation of Magnetic Fields Near Kelvin-Helmholtz Instability Region in Pair Plasmas  

DEFF Research Database (Denmark)

We present the simulation results by using a two-dimensional electromagnetic and relativistic particle-in-cell (PIC) code that quasi-static magnetic field can be generated in the Kelvin-Helmholtz instability region in unmagnetized pair plasmas.

Nakayama, T.; Sakai, J.-I.

1999-01-01

99

Open Circuit Field Distribution and Induced Voltage of a Cylindrical Permanent Magnet Linear Generator  

Directory of Open Access Journals (Sweden)

Full Text Available This paper deals with the analytical computation of the magnetic field of a cylindrical permanent magnet linear generator. It offers an alternative solution to the magnetic field problem. A new approach to solve Poisson equation using Struve function is introduced and it offers a simple but accurate analytical estimation to the calculation of the open circuit flux density and induced voltage. The finite element analysis simulation is performed to validate the analytical calculation.

Wijono

2007-01-01

100

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

Kandia, Effrosyni

2013-01-01

 
 
 
 
101

The spontaneous generation of magnetic fields at high temperature in a supersymmetric theory  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The spontaneous generation of magnetic and chromomagnetic fields at high temperature in the minimal supersymmetric standard model (MSSM) is investigated. The consistent effective potential including the one-loop and the daisy diagrams of all bosons and fermions is calculated and the magnetization of the vacuum is observed. The mixing of the generated fields due to the quark and s-quark loop diagrams and the role of superpartners are studied in detail. It is found that the co...

Demchik, V. I.; Skalozub, V. V.

2002-01-01

102

Effect of an External Oriented Magnetic Field on Entropy Generation in Natural Convection  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The influence of an external oriented magnetic field on entropy generation in natural convection for air and liquid gallium is numerically studied in steady-unsteady states by solving the mass, the momentum and the energy conservation equations. Entropy generation depends on five parameters which are: the Prandtl number, the irreversibility coefficients, the inclination angle of the magnetic field, the thermal Grashof and the Hartmann numbers. Effects of these parameters on total and local ir...

Atef El Jery; Nejib Hidouri; Mourad Magherbi; Ammar Ben Brahim

2010-01-01

103

Generation of Seed Magnetic Field around First Stars:Effects of Radiation Force  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We investigate seed magnetic field generation in the early universe by radiation force of first stars. In the previous study with steady assumption, large amplitudes(10^{-15} G for first stars, 10^{-11}G for QSOs) are predicted. In this study, we formulate this issue in unsteady framework. Then, we consider a specific model of magnetic field generation around a very massive first star. Consequently, 1) we find steady assumption is not valid in realistic situation, and 2) obt...

Ando, Masashi; Doi, Kentaro; Susa, Hajime

2010-01-01

104

Manufacturing method for coil conductors to generate strong magnetic field  

International Nuclear Information System (INIS)

A cylindrical member comprising copper/chromium alloy steel is formed. A central hole is perforated at the center of the cylindrical member for passing coolants. A wedge is attached to the central hole and struck by a static pressure press to extend the central hole. In this case, pressing force of the wedge is applied to the inner surface of the central hole of the cylindrical member, by which the central hole undergoes cold working to provide a metal tissues with large intramolecular density, and the inner surface of the central hole is hardened. Mechanical fabrication and electric discharge machining are applied to the outer surface of the cylindrical member and the wall surface of the central hole. Subsequently, spiral grooves are formed on the surface of the cylindrical member. A durability in view of strength is increased by hardening the inner surface of the central hole of the coil conductor, the coil conductor has sufficient resistance against strong magnetic fields if occur. (I.N.)

1992-08-24

105

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

CERN Multimedia

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 ...

Shiromoto, Yuki; Hosokawa, Takashi

2014-01-01

106

Generation of Seed Magnetic Field around First Stars:Effects of Radiation Force  

CERN Multimedia

We investigate seed magnetic field generation in the early universe by radiation force of first stars. In the previous study with steady assumption, large amplitudes(10^{-15} G for first stars, 10^{-11}G for QSOs) are predicted. In this study, we formulate this issue in unsteady framework. Then, we consider a specific model of magnetic field generation around a very massive first star. Consequently, 1) we find steady assumption is not valid in realistic situation, and 2) obtain much smaller magnetic field strength than predicted by Langer et al. (2003). In addition, we find momentum transfer process during photoionization is more important than Thomson scattering. The resultant magnetic flux density around the first star is < 10^{-19}G. These seed magnetic field will not affect subsequent star formation in the neighbor of first stars.

Ando, Masashi; Susa, Hajime

2010-01-01

107

GENERATION OF SEED MAGNETIC FIELD AROUND FIRST STARS: EFFECTS OF RADIATION FORCE  

International Nuclear Information System (INIS)

We investigate seed magnetic field generation in the early universe by the radiation force of first stars. In a previous study with the steady assumption, large amplitudes (?10-15 G for first stars, ?10-11 G for QSOs) are predicted. In this study, we formulate this issue in an unsteady framework. Then, we consider a specific model of magnetic field generation around a very massive first star. Consequently, we (1) find that the steady assumption is not valid in realistic situations and (2) obtain a much smaller magnetic field strength than that predicted by Langer et al. In addition, we find that the momentum transfer process during photoionization is more important than Thomson scattering. The resultant magnetic flux density around the first star is ?-19 G. This seed magnetic field will not affect subsequent star formation in the neighborhood of first stars.

2010-06-20

108

Magnetic field generation during the collision of electron-ion plasma clouds  

DEFF Research Database (Denmark)

We present the results of analytical studies and computer simulations of electron-ion plasma cloud collisions using 2D3V particle-in-cell and 2D two-fluid collisionless relativistic codes. We address the problem covering the generation of a quasistatic magnetic field. Using relativistic two-fluid equations for the two counterstreaming electron populations: we show with the help of linear theory that the generation of a magnetic field can be associated with the "electromagnetic counterstreaming instability". Two-dimensional (2D) particle-in-cell provide good agreement with the results of linear theory. We show that the quasistatic magnetic field undergoes a collisionless change of structure, leading to large-scale, long-lived structures. These processes may be important for the understanding of magnetic field generation in laser plasmas and in space plasmas in the regions where two stellar winds collide.

Kazimura, Yoshihiro; Califano, Francesco

1998-01-01

109

Effect of an External Oriented Magnetic Field on Entropy Generation in Natural Convection  

Directory of Open Access Journals (Sweden)

Full Text Available The influence of an external oriented magnetic field on entropy generation in natural convection for air and liquid gallium is numerically studied in steady-unsteady states by solving the mass, the momentum and the energy conservation equations. Entropy generation depends on five parameters which are: the Prandtl number, the irreversibility coefficients, the inclination angle of the magnetic field, the thermal Grashof and the Hartmann numbers. Effects of these parameters on total and local irreversibilities as well as on heat transfer and fluid flow are studied. It was found that the magnetic field tends to decrease the convection currents, the heat transfer and entropy generation inside the enclosure. Influence of inclination angle of the magnetic field on local irreversibility is then studied.

Atef El Jery

2010-05-01

110

Scaling laws for a self-generated axial magnetic field in laser-produced plasma  

International Nuclear Information System (INIS)

The generation of an axial magnetic field caused by the interaction of standing waves formed by two counterpropagating, elliptically polarized electromagnetic waves with a laser-produced plasma has been investigated. Study of the variation of magnetization with different powers and wavelengths available from Nd--glass and CO2 lasers shows that induced axial magnetization increases linearly with an increase in power for all wavelengths and increases exponentially with the wavelengths for different laser powers at a particular plasma density. The variation of magnetization with plasma density reveals that the peak value of magnetization occurs below the critical density (n/sub c/) for a particular wavelength and power. Scaling laws for the induced axial magnetic field have been given. The poloidal fields arising from such mechanisms are important in the lateral energy and axial energy transport mechanisms. Such a field inhibits lateral energy transport, but axial energy propagation may be increased

1988-01-01

111

Evolution of magnetic field generated by the Kelvin-Helmholtz instability  

CERN Document Server

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.

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

2014-01-01

112

Magnetic field amplification and generation in hypervelocity meteoroid impacts with application to lunar paleomagnetism  

Energy Technology Data Exchange (ETDEWEB)

A one-dimensional numerical model for the expansion of impact-produced vapor clouds is used to investigate magnetic field generation mechanisms in events such as meteor collisions with the moon. The resulting cloud properties, such as ionization fraction, electrical conductivity, radial expansion velocity, mass density, and energy density are estimated. The model is initiated with the peak shock states and pressure thresholds for incipient and complete vaporization of anorthosite lunar surface materials by iron and GA composition meteorites. The expansion of the spherical gas cloud into a vacuum was traced with a one-dimensional explicit lagrangian hydrodynamic code. The hypervelocity impact plasmas produced are found to be significant in the amplitudes and orientations of the magnetic fields generated. An ambient magnetic field could have been provided by the core dynamo, which would have interacted with the expanding plasmas and formed induced paleomagnetic fields. Several other field-contribution mechanisms are discussed and discarded as potential remanent magnetism contributors.

Hood, L.L.; Vickery, A.

1984-11-15

113

Magnetic field amplification and generation in hypervelocity meteoroid impacts with application to lunar paleomagnetism  

International Nuclear Information System (INIS)

A one-dimensional numerical model for the expansion of impact-produced vapor clouds is used to investigate magnetic field generation mechanisms in events such as meteor collisions with the moon. The resulting cloud properties, such as ionization fraction, electrical conductivity, radial expansion velocity, mass density, and energy density are estimated. The model is initiated with the peak shock states and pressure thresholds for incipient and complete vaporization of anorthosite lunar surface materials by iron and GA composition meteorites. The expansion of the spherical gas cloud into a vacuum was traced with a one-dimensional explicit lagrangian hydrodynamic code. The hypervelocity impact plasmas produced are found to be significant in the amplitudes and orientations of the magnetic fields generated. An ambient magnetic field could have been provided by the core dynamo, which would have interacted with the expanding plasmas and formed induced paleomagnetic fields. Several other field-contribution mechanisms are discussed and discarded as potential remanent magnetism contributors

1984-11-15

114

Magnetic field amplification and generation in hypervelocity meteoroid impacts with application to lunar paleomagnetism  

Science.gov (United States)

A one-dimensional numerical model for the expansion of impact-produced vapor clouds is used to investigate magnetic field generation mechanisms in events such as meteor collisions with the moon. The resulting cloud properties, such as ionization fraction, electrical conductivity, radial expansion velocity, mass density, and energy density are estimated. The model is initiated with the peak shock states and pressure thresholds for incipient and complete vaporization of anorthosite lunar surface materials by iron and GA composition meteorites. The expansion of the spherical gas cloud into a vacuum was traced with a one-dimensional explicit lagrangian hydrodynamic code. The hypervelocity impact plasmas produced are found to be significant in the amplitudes and orientations of the magnetic fields generated. An ambient magnetic field could have been provided by the core dynamo, which would have interacted with the expanding plasmas and formed induced paleomagnetic fields. Several other field-contribution mechanisms are discussed and discarded as potential remanent magnetism contributors.

Hood, L. L.; Vickery, A.

1984-11-01

115

Role of charged gauge fields in generating magnetic seed fields in bubble collisions during the cosmological electroweak phase transition  

International Nuclear Information System (INIS)

We calculate the magnetic field generated during bubble collisions in a first-order electroweak phase transition that may occur for some choices of parameters in the minimal supersymmetric standard model. We derive equations of motion from the electroweak Lagrangian that couple the Higgs field and the gauge fields of the standard model sector. We show that for sufficiently gentle collisions, where the Higgs field is relatively unperturbed in the bubble overlap region, the equations of motion can be linearized so that in the absence of fermions the charged W± fields are the source of the electromagnetic current for generating the seed fields. Solutions of the equations of motion for the charged gauge fields and Maxwell's equations for the magnetic field in O(1,2) space-time symmetry are expressed in closed form by applying boundary conditions at the time of collision. Our results indicate that the magnetic fields generated by charged W± fields in the collision are comparable to those found in previous work. The magnetic fields so produced could seed galactic and extra-galactic magnetic fields observed today

2008-01-15

116

Crossed-magnetic-field experiments on stacked second generation superconducting tapes: Reduction of the demagnetization effects  

Science.gov (United States)

The crossed-magnetic-field effect on the demagnetization factor of stacked second generation (2G) high temperature superconducting tapes is presented. The superconducting sample was initially magnetized along the c-axis by the field cooling magnetization method and after achieving the magnetic relaxation of the sample, an extensive set of experimental measurements for different amplitudes of an applied ac magnetic field parallel to the ab-plane was performed. On the one hand, a striking reduction of the demagnetization factor compared with the reported values for superconducting bulks is reported. On the other hand, the demagnetization factor increases linearly with the amplitude of the ac transverse magnetic field confirming the universal linear behavior for the magnetic susceptibility predicted by Brandt [Phys. Rev. B 54, 4246 (1996)]. The study has been also pursued at different frequencies of the ac transverse magnetic field in order to determine the influence of this parameter on the demagnetization factor measurements. We report an even lower demagnetization factor as long as the frequency of the transverse magnetic field increases. Thus, the significant reduction on the demagnetization factor that we have found by using stacked 2G-superconducting tapes, with higher mechanical strength compared with the one of superconducting bulks, makes to this configuration a highly attractive candidate for the future development of more efficient high-power density rotating machines and strong magnet applications.

Baghdadi, M.; Ruiz, H. S.; Coombs, T. A.

2014-06-01

117

Generation of quasi static magnetic field in the relativistic laser-plasma interactions  

Energy Technology Data Exchange (ETDEWEB)

The magnetic field generation by a relativistic laser light impinging on a thin target at oblique incidence is investigated using a two dimensional particle-in-cell simulation. We have found that the surface magnetic field inhibits the electron transport into the plasma and restricts the electron motion of the low energies at the surface for {theta} = 75 degrees. When the incident angle is larger than a certain critical angle, a magnetic field will restrict electron motion strongly. The existence of the critical angle, which restricts the electron transport, is well consistent with the theory. (authors)

Susumu, Kato; Yoshiro, Owadano [National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki (Japan); Tatsufumi, Nakamura; Kunioki, Mima; Hideo, Nagatomo [Osaka Univ., Institute of Laser Engineering (ILE), Suita, Osaka (Japan); Yasuhiko, Sentoku [Nevada Univ., Dept. of Physics, Reno, NV (United States)

2004-07-01

118

Evaluation of generated field in magnetic-particle testing using rotating field  

International Nuclear Information System (INIS)

In yoke method magnetic-particle testing, it is necessary to perform the testing at least two times by changing the direction of magnetization. In a rotating field type magnetizer using a three-phase alternating current (AC), any directional flaw can be detected by a single testing. In this research, the distributions of the rotating magnetic flux density were evaluated by measuring this density using Hall elements (in three directions) and by numerical analysis. The distributions of the magnetic flux density around the flaw were also evaluated by numerical analysis. The distribution of the rotating magnetic flux density near the central part of the magnetizer was made clear, and it was confirmed that the distribution became more uniform by equalizing the impedance of each coil of the magnetizer. (author)

2009-08-01

119

Theory of nonlinear particle acceleration at shocks and self-generation of the magnetic field  

CERN Multimedia

We present some recent developments in the theory of particle acceleration at shock fronts in the presence of dynamical reaction of the accelerated particles and self-generation of magnetic field due to streaming instability. The spectra of accelerated particles, the velocity, magnetic field and temperature profiles can be calculated in this approach anywhere in the precursor and in the downstream region. The implications for the origin of cosmic rays and for the phenomenology of supernova remnants will be discussed.

Blasi, Pasquale

2007-01-01

120

Brief communication "Modeling tornado dynamics and the generation of infrasound, electric and magnetic fields"  

Directory of Open Access Journals (Sweden)

Full Text Available Recent observations endorse earlier measurements of time varying electric and magnetic fields generated by tornadoes and dust devils. These signals may provide a means for early warning but together with a proper modeling approach can also provide insight into geometry and dynamics of the vortices. Our model calculations show the existence of pressure resonances characterized as acoustic duct modes with well defined frequencies. These resonances not only generate infrasound but also modulate the charge density and the velocity field and in this way lead to electric and magnetic field oscillations in the 0.5–20-Hz range that can be monitored from a distance of several kilometers.

E. D. Schmitter

2010-02-01

 
 
 
 
121

Generation of Uranus and Neptune large-scale magnetic fields by turbulent dynamo mechanism  

International Nuclear Information System (INIS)

A model of generation of a large-scale magnetic field in the Uranus nucleus and ocean bottom using nonuniform rotation and mean spiraling convective movements is built. It is shown that in a thin ocean envelope there can occur the prevailing excitation of a nonaxisymmetric field resulting in a sharp slope of the total dipole momentum of the nucleus and envelope field. The minimum convective velocities required for exciting the observed field are estimated. Due to the similar structure of Uranus and Neptune the same model can be applied to the latter. Taking into account that nearly one half of the Neptune nucleus is solid a lowere convection rate and consequently less effective magnetic field generation can be expected inside the Neptune nucleus that is why the main contribution into generation of the Neptune field must be made by motions in its ocean

1989-01-01

122

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.

2011-11-10

123

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

1990-04-24

124

Spontaneous generation of toroidal magnetic field during spheromak formation in a conical Theta-pinch  

International Nuclear Information System (INIS)

Spheromaks have been generated in conical Theta-pinches in a similar manner to FRC generation in straight reversed-field Theta-pinches. The essential difference is that when a conical Theta-pinch coil is used, a toroidal component to the magnetic field spontaneously appears. The poloidal component is generated by quickly reversing the current in the coil after an initial bias field is embedded in the preionized plasma. The toroidal component is generated through a much more subtle physical process. Numerical calculations have shown that the Hall term can lead to the generation of toroidal magnetic fields during the formation of an FRC; however for a straight coil, symmetry demands equal and opposite fields at each end, so no net toroidal flux or helicity can be generated. A simple analysis shows that even for a conical coil, the Hall term by itself cannot generate significant toroidal magnetic flux or helicity. They will show that a combination of the Hall term with the plasma resistivity can result in toroidal fields of comparable magnitude to experimental observation

1986-09-01

125

Generation of Electric and Magnetic Fields During Detonation of High Explosive Charges in Boreholes  

Energy Technology Data Exchange (ETDEWEB)

We present experimental results of a study of electromagnetic field generation during underground detonation of high explosive charges in holes bored in sandy loam and granite. Test conditions and physico-mechanical properties of the soil exert significant influence on the parameters of electromagnetic signals generated by underground TNT charges with masses of 2 - 200 kg. The electric and magnetic field experimental data are satisfactorily described by an electric dipole model with the source embedded in a layered media.

Soloviev, S; Sweeney, J

2004-06-04

126

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

2008-06-01

127

Generation of synchronous AC power through magnetic field compression  

International Nuclear Information System (INIS)

This paper presents conceptual analytical design picture for the MHD-synchronous AC generator using an accelerated plasma from the divertor of the fusion reactor plant. The exhaust plasma of the fusion reactor usually at low level in pressure and velocity will be accelerated through the action of any model of the linear induction accelerators. Structural components of the synchronous-MHD generator comprises co-axial perfectly conducting cylinders with the inner cylinder having a set of lateral tangential blades whose function is to impart the rotor with the desired mechanical velocity for synchronous operation, from the impinging plasma. Electric AC power will be developed through induction in a sinusoidally distributed three phase conventional winding close to the inner cylinder. Magneto-fluid interaction solutions as well as electro-mechanical outcome power expressions have been secured for actual concept design. (Auth.)

1982-12-13

128

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

Energy Technology Data Exchange (ETDEWEB)

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)

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

2003-03-01

129

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

CERN Document Server

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...

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

2014-01-01

130

Generation of electromagnetic radiation by plasma rotating in crossed electrostatic and magnetic fields  

International Nuclear Information System (INIS)

Generation of electromagnetic waves by plasma ring layer which is rotating in crossed radial electrostatic and axial magnetic fields in a cylindric resonator is studied theoretically. Dispersion equations which describe wave-plasma interaction are obtained. It was shown that wave generation by a narrow layer is possible by cyclotron, Cherenkov or plasma resonances. Wave frequencies and increments are found for mentioned resonances in a homogeneous plasma layer. The advantages and disadvantages of wave generation under different conditions are noted. 9 refs

1997-01-01

131

Computational Study of the Strong Magnetic Field Generation in Non-Spherical Cone-Guided Implosion  

International Nuclear Information System (INIS)

Full text: The magnetic field in non-spherical cone-guided implosion is simulated using temporal evolution equations of the magnetic field coupled with simulated result of 2-D radiation hydrodynamic simulation for Fast Ignition as the first attempt. We have found that the magnetic field is generated by ?Te x ?Ne term, and it is compressed by the implosion. In the result, it reaches 5 MG at maximum compression, which was not considered before. Also, high Hall parameter region is appeared between cone tip and core plasma. This magnetic field is strong enough to affect the implosion dynamic and hot electron transport, therefore it should be paid attention in these simulations for Fast Ignition. (author)

2012-09-01

132

Generation of relativistic electrons and ultra-high magnetic field for fast ignition  

Science.gov (United States)

Certain plasma processes would play a crutialal role during fast ignition (M. Tabak et. al., Phys. Plasmas 1,) 1626 (1994)., including the production of relativistic electrons in laser-matter interactions, the resulting generation of multi-megagauss magnetic fields, and the self-consistent effect on the relativistic electrons. We present an analytical model of fast electron generation by ``snow-plowing'' the plasma by an intense laser pulse and evaluate the electron beam current and energy. Since focused propagation of the electron beam is essential, and self-magnetic field can provide the required focusing, collisional and collisionless mechanisms of magnetic field penetration into the plasma are evaluated. Another mechanism of magnetic field generation is the inverse Faraday effect (IFE), whereby angular momentum is transfered from the ions to the electrons in the presence of circularly polarized laser. Implications of IFE to fast ignition are discussed. Another mechanism of B-field generation is the modification of electron-ion collisions in the presence of intense laser field. (G. Shvets and N. J. Fisch, Phys. Plasmas 4,) 428 (1997).

Shvets, Gennady; Fisch, Nathaniel

1997-11-01

133

Magnetic Field Generation through Angular Momentum Exchange between Circularly Polarized Radiation and Charged Particles  

CERN Document Server

The interaction between circularly polarized (CP) radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic field generation.

Shvets, G

2002-01-01

134

Magnetic field generation through angular momentum exchange between circularly polarized radiation and charged particles  

International Nuclear Information System (INIS)

The interaction between circularly polarized radiation and charged particles can lead to generation of magnetic field through an inverse Faraday effect. The spin of the circularly polarized electromagnetic wave can be converted into the angular momentum of the charged particles so long as there is dissipation. We demonstrate this by considering two mechanisms of angular momentum absorption relevant for laser-plasma interactions: electron-ion collisions and ionization. The precise dissipative mechanism, however, plays a role in determining the efficiency of the magnetic-field generation

2002-04-01

135

Electromagnetic design analysis and performance improvement of axial field permanent magnet generator for small wind turbine  

Science.gov (United States)

Axial field permanent magnet (AFPM) generators are widely applied for the small wind turbine. The output power of conventional AFPM generator, AFER-NS (Axial Field External Rotor-Non Slotted) generator, is limited by the large reluctance by the long air-gap flux paths. In this paper, the novel structure of AFPM generator, AFIR-S (Axial Field Inner Rotor-Slotted) generator, is suggested to improve the output characteristics. The electromagnetic design analysis and the design improvement of the suggested AFIR-S generator are studied. Firstly, the electromagnetic design analysis was done to increase the power density. Secondly, the design optimizations of the rotor pole-arc ratio and skew angle to increase the output power and to reduce the cogging torque. Finally, the output performances of AFER-NS and AFIR-S generator are compared with each other.

Jung, Tae-Uk

2012-04-01

136

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

Science.gov (United States)

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.

Avino, F.; Fasoli, A.; Furno, I.

2014-03-01

137

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

Science.gov (United States)

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.

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

2008-01-01

138

Super-Alfvénic Magnetic Field Fluctuations Generated from Low-Density, Magnetized Laser-Plasma Expansions  

Science.gov (United States)

In recent experiments at the Trident Laser Facility, at the Los Alamos National Laboratory (LANL), the three beam configuration and a pulsed Helmholtz coil were utilized to investigate laser-driven, magnetized shocked plasmas. The 56 cm, 4.2 kJ pulsed Helmholtz coil was used to create a 0.1-1.0 kG magnetic field over an experimental volume of ˜4x10^3 cm^3. Two sequential laser pulses, spaced 1.0-10.0 ?s apart, were used to ablate a CH or graphite target that was imbedded in the field. The first laser pulse created an ambient magnetized plasma and the second laser pulse created a debris plasma to shock the ambient plasma. The third laser pulse was frequency-doubled and employed for Thomson scattering measurements to characterized the ambient plasma density (10^13-10^15 cm-3) and electron temperature (10-50 eV). An array of single-axis, 1 mm b-dot probes were used to measure magnetic field compression, expulsion, and fast-diffusion inside and around the diamagnetic cavity formed by the laser-plasma expansion. A magnetic field compression pulse in the shocked plasma was observed to separate and propagate away from the leading edge of the diamagnetic cavity at an Alfvénic Mach number on the order of 10 (MA˜10).

Everson, E. T.; Bondarenko, A. S.; Morton, L. A.; Schaeffer, D.; Lopez, R.; Constantin, C. G.; Montgomery, D.; Shimada, T.; Johnson, R.; Letzring, S.; Niemann, C.

2010-11-01

139

Generation of high magnetic field 11 T by large scale superconducting coils  

International Nuclear Information System (INIS)

In May, 1984, in Japan Atomic Energy Research Institute, a high magnetic field of 11 T was successfully generated with the large scale superconducting coils for a nuclear fusion reactor. It was the highest magnetic field in the world. The generation of this high magnetic field was achieved by installing CBC coils in the coils installed before, in the setup simulating toroidal coil arrangement called cluster test apparatus. In this paper, the outline of the power-augmenting works for the cluster test apparatus related to the installation of CBC coils is discussed. For the development of large scale superconducting coils, as the technical subjects, the development of large current superconductors acting in a high magnetic field, the countermeasures to strong electromagnetic force, the solution of the electric, magnetic and mechanical problems caused by pulsed magnetic field, the development of large helium-liquefying refrigerators and their peripheral equipment, and the development of synthetic technology systematizing those are enumerated. The development of high voltage, large current leads is in progress. (Kako, I.)

1985-01-01

140

Detonation driven induction generators with parallel and antiparallel external and induced magnetic fields  

International Nuclear Information System (INIS)

Based on Maxwell's equations, the electric current and voltage pulses induced in explosion driven induction generators (R/sub m/ = ?0sigmavL>>1) with plane electrodes and homogeneous external magnetic field B0 are calculated analytically for two plasma shock flows, (i) the jet flow with shock speed v(t) = v0, t> or =0, and (ii) the plane detonation flow with shock speed v(t) = (2/3)(E0/rho0)/sup 1/3/t/sup -1/3/, t> or =0. The external load circuit with resistance R0 and inductance L0 is connected either (I) to the downstream ends or (II) to the flow entrance ends of the electrodes so that the magnetic self-field B(t) of the generated current I(t) is (I) parallel and (II) antiparallel to the transverse external field B0. In both generator models I and II, the jet flow produces large current and voltage pulses, whereas the detonation flow generates considerably smaller and shorter current and voltage pulses. In all cases, the magnetic self-field B(t) of the generated current I(t) is of the order-of-magnitude of B0, but the generator with electrode wiring I (positive superposition of B and B0) produces considerably more power and energy than the generator with electrode wiring II (negative superposition of B and B0)

1982-01-01

 
 
 
 
141

Magnetic seed field generation from electroweak bubble collisions with bubble walls of finite thickness  

International Nuclear Information System (INIS)

Building on earlier work, we develop an equation-of-motion method for calculating magnetic seed fields generated from currents arising from charged W± fields in bubble collisions during a first-order primordial electroweak phase transition allowed in some proposed extensions of the standard model. The novel feature of our work is that it takes into account, for the first time, the dynamics of the bubble walls in such collisions. We conclude that for bubbles with sufficiently thin surfaces the magnetic seed fields may be comparable to, or larger than, those found in earlier work. Thus, our results strengthen the conclusions of previous studies that cosmic magnetic fields observed today may originate from seeds created during the electroweak phase transition, and consequently that these fields may offer a clue relevant to extensions of the standard model.

2009-10-15

142

The breakdown of dipolar magnetic field generation in planetary dynamo models (Invited)  

Science.gov (United States)

Magnetic field measurements show that each dynamo in our solar system is distinct with field strengths that differ by many orders of magnitude and morphologies that range from titled dipoles to nearly axisymmetric dipole-quadrupoles to non-axisymmetric multipoles. The characteristics of stellar and astrophysical magnetic fields are similarly wide-ranging. Towards understanding the diversity of this dynamo zoo, we investigate the breakdown of dipole-dominated magnetic fields in a suite of planetary dynamo and otherwise identical non-magnetic simulations where the convective vigor and rotation rate are varied systematically. This survey considers models with Prandtl number Pr=1, magnetic Prandtl numbers up to Pm = 5, Ekman numbers in the range 1e-3 <= E <= 1e-5, and Rayleigh numbers from near onset to more than 1000 times critical. A sharp transition from dipolar to multipolar dynamos is observed in models with moderate to high Ekman numbers. This breakdown of the dipole happens when inertial and viscous forces become comparable and coincides with a degradation of helicity in the flow, which also occurs when no magnetic field is present. Large-scale poloidal magnetic fields in these models then appear to be generated by a viscously controlled, macro-scale alpha-effect. Our lowest Ekman number cases, however, suggest that the dynamics may be changing as the viscous force decreases. Since viscosity is expected to be negligible in planetary and stellar interiors, an extrapolation of our results implies that moderate Ekman number models may not simulate the physical mechanisms of magnetic field generation in these bodies correctly.

Soderlund, K. M.; King, E. M.; Aurnou, J. M.

2013-12-01

143

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 equa...

Mounir Bouabid; Nejib Hidouri; Mourad Magherbi; Ammar Ben Brahim

2011-01-01

144

Magnetic field generation from Self-Consistent collective neutrino-plasma interactions  

International Nuclear Information System (INIS)

A new Lagrangian formalism for self-consistent collective neutrino-plasma interactions is presented in which each neutrino species is described as a classical ideal fluid. The neutrino-plasma fluid equations are derived from a covariant relativistic variational principle in which finite-temperature effects are retained. This new formalism is then used to investigate the generation of magnetic fields and the production of magnetic helicity as a result of collective neutrino-plasma interactions

1999-01-01

145

Control of generation regimes of ring chip laser under the action of the stationary magnetic field  

International Nuclear Information System (INIS)

We consider realisation of different generation regimes in an autonomous ring chip laser, which is a rather complicated problem. We offer and demonstrate a simple and effective method for controlling the radiation dynamics of a ring Nd:YAG chip laser when it is subjected to a stationary magnetic field producing both frequency and substantial amplitude nonreciprocities. The amplitude and frequency nonreciprocities of a ring cavity, arising under the action of this magnetic field, change when the magnet is moved with respect to the active element of the chip laser. Some self-modulation and stationary generation regimes as well as the regime of beatings and dynamic chaos regime are experimentally realised. Temporal and spectral characteristics of radiation are studied and conditions for the appearance of the generation regime are found. (control of laser radiation parameters)

2013-05-31

146

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

Science.gov (United States)

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.

Kaethner, Christian; Ahlborg, Mandy; Knopp, Tobias; Sattel, Timo F.; Buzug, Thorsten M.

2014-01-01

147

Study of two medium size 'C' core electromagnets generating low magnetic fields  

International Nuclear Information System (INIS)

Magnetic field requirements of laboratories may impose constraints that often call for a variety of non-standard designs. The designer has to fulfil these demands without letting the design to become too inefficient. Since no ready design procedures are available he has to resort to intuition calculation and modelling. In spite of this there may be wide discrepancy between the design values and the actual results. This report describes the experience gained on two 'C' core electromagnets being used by authors. These magnets generate low magnetic fields over reasonably large volumes, a requirement that runs opposite to that of most other magnets. The study reveals the dependence of overall performance efficiency, field uniformity etc. on the design parameters. 31 figures. (author)

1987-01-01

148

Field generated within the SSC magnets due to persistant currents in the superconductor  

International Nuclear Information System (INIS)

This report presents the results of a number of computer studies of the magnetic fields generated by persistent circulating currents in the superconductor of superconducting dipoles. These magnetic fields are referred to as residual fields throughout this report. Since the field generated by persistent currents have a hysteric behavior, they are analagous to the residual filed found in iron bound conventional solenoids. The residual field calculations presented in this report were done using the LBL SCMAG4 computer code. This code has not been well tested against measured data, but a comparison with measured CBA data given in this report suggests that good agreement is possible. The residual fields generated by persistent superconducting currents are rich in higher multipoles. This is of concern to the accelerator designer for SSC. This report shows the effect of various superconductor parameters and coil parameters on the magnitude and structure of the residual fields. The effect of the magnet charging history on residual fields is aldo discussed. 14 references

1983-12-12

149

Field generated within the SSC magnets due to persistant currents in the superconductor  

Energy Technology Data Exchange (ETDEWEB)

This report presents the results of a number of computer studies of the magnetic fields generated by persistent circulating currents in the superconductor of superconducting dipoles. These magnetic fields are referred to as residual fields throughout this report. Since the field generated by persistent currents have a hysteric behavior, they are analagous to the residual filed found in iron bound conventional solenoids. The residual field calculations presented in this report were done using the LBL SCMAG4 computer code. This code has not been well tested against measured data, but a comparison with measured CBA data given in this report suggests that good agreement is possible. The residual fields generated by persistent superconducting currents are rich in higher multipoles. This is of concern to the accelerator designer for SSC. This report shows the effect of various superconductor parameters and coil parameters on the magnitude and structure of the residual fields. The effect of the magnet charging history on residual fields is aldo discussed. 14 references.

Green, M.A.

1984-01-01

150

Toroidal magnetic field generation during compact toroid formation in a field-reversed theta pinch and a conical theta pinch  

International Nuclear Information System (INIS)

The influence that the Hall and delP/sub e/ terms, in a generalized Ohm's law, have on the formation of a compact toroid in a field-reversed theta pinch and a conical theta pinch has been examined. The inclusion of these terms leads to the spontaneous generation of toroidal magnetic fields and toroidal velocities. The toroidal fields in the end regions reach peak values of almost 50% of the external poloidal field during the early stages of formation. When the coil geometry is the same at each end of the theta pinch, equal and opposite toroidal fields are generated by the Hall effect, so that no net toroidal flux is generated. When the geometry is not the same at each end, the Hall effect can lead to a net toroidal flux. Calculations for both a conical theta pinch experiment and a field-reversed configuration translation experiment demonstrate the generation of net toroidal flux, as observed experimentally

1986-01-01

151

Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability  

Science.gov (United States)

We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin-Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of the kinetic Kelvin-Helmholtz instability (KKHI) of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field Ez, perpendicular to the flow boundary, and the magnetic field By, transverse to the flow direction. After the By component is excited, an induced electric field Ex, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios mi/me = 1836 and mi/me = 20 are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (?j = 1.5) is larger than for a relativistic jet case (?j = 15).

Nishikawa, K.-I.; Hardee, P.; Zhang, B.; Du?an, I.; Medvedev, M.; Choi, E. J.; Min, K. W.; Niemiec, J.; Mizuno, Y.; Nordlund, A.; Frederiksen, J. T.; Sol, H.; Pohl, M.; Hartmann, D. H.

2013-09-01

152

Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability  

CERN Document Server

We have investigated generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin-Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of KKHI of our jet-sheath configuration is slightly different even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field $E_{\\rm z}$ and the magnetic field $B_{\\rm y}$. After the $B_{\\rm y}$ component is excited, an induced electric field $E_{\\rm x}$ becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios $m_{\\rm i}/m_{\\rm e} = 1836$ and $m_{\\rm i}/m_{\\rm e} = 20$ are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The g...

Nishikawa, K -I; Zhang, B; Dutan, I; Medvedev, M; Choi, E J; Min, K W; Niemiec, J; Mizuno, Y; Nordlund, A; Frederiksen, J T; Sol, H; Pohl, M; Hartmann, D H

2013-01-01

153

Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability  

Directory of Open Access Journals (Sweden)

Full Text Available We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin–Helmholtz instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012, the structure of the kinetic Kelvin–Helmholtz instability (KKHI of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field Ez, perpendicular to the flow boundary, and the magnetic field By, transverse to the flow direction. After the By component is excited, an induced electric field Ex, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios mi/me = 1836 and mi/me = 20 are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (?j = 1.5 is larger than for a relativistic jet case (?j = 15.

K.-I. Nishikawa

2013-09-01

154

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

Science.gov (United States)

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.

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

2008-01-01

155

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

Science.gov (United States)

We demonstrate experimentally and numerically that in fiber tips as they are used in NSOMs azimuthally polarized electrical fields (|Eazi|2 / |Etot|2 ?55% ± 5% for ?0 = 1550 nm), respectively subwavelength confined (FWHM ?450 nm ??0/3.5) magnetic fields, are generated for a certain tip aperture diameter (d = 1.4 ?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. PMID:24921567

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

2014-06-01

156

Magnetic field measurements of a superconducting undulator for a Harmonic Generation FEL experiment at the NSLS  

International Nuclear Information System (INIS)

An 18mm period, 0.54 Tesla, 8mm gap superconducting undulator with both horizontal and vertical focusing has been built and tested. This magnet, which is fabricated in 25 cm length sections, is being tested for use in the radiator section (total magnet length of 1.5 m) of the Harmonic Generation Free Electron Laser experiment at the National Synchrotron Light Source - Accelerator Test Facility at Brookhaven National Lab., in collaboration with Grumman Corp. The measurement system is outlined, sources and estimates of errors are described, and some magnetic field data are presented and discussed

1993-05-17

157

Symplectic integrator for s-dependent static magnetic fields based on mixed-variable generating functions  

International Nuclear Information System (INIS)

We describe a technique for constructing a symplectic transfer map for a charged particle moving through an accelerator component with arbitrary three-dimensional static magnetic field. The transfer map is constructed by symplectic integration; by representing the map at each step of the integration by a mixed-variable generating function, exact symplecticity is ensured. By using an appropriate integration algorithm, there is no necessity to make the paraxial approximation. The technique is illustrated by application (in one degree of freedom) to a quadrupole magnet with strong octupole component and fringe field.

2012-04-01

158

Modeling and analysis of solar wind generated contributions to the near-Earth magnetic field  

DEFF Research Database (Denmark)

Solar wind generated magnetic disturbances are currently one of the major obstacles for improving the accuracy in the determination of the magnetic field due to sources internal to the Earth. In the present study a global MHD model of solar wind magnetosphere interaction is used to obtain a physically consistent, divergence-free model of ionospheric, field-aligned and magnetospheric currents in a realistic magnetospheric geometry. The magnetic field near the Earth due to these currents is analyzed by estimating and comparing the contributions from the various parts of the system, with the aim of identifying the most important aspects of the solar wind disturbances in an internal field modeling context. The contribution from the distant magnetospheric currents is found to consist of two, mainly opposing, contributions from respectively the dayside magnetopause currents and the cross-tail current. At high latitudes the field-aligned component is of partidular interest in connection with internal field-modelling. In the attitude regime of 400-800 km (typical for low Earth orbit satellites) the ionospheric currents are found to contribute significantly to the disturbancance, and account for more than 90% of the field-aligned disturbance. The magnetic disturbance field from field-aligned currents (FACs) is basically transverse to the main field, and they therefore contribute with less than 2% to the disturbance in total field intensity. Inhomogeneity in ionospheric conductance is identified as the main cause of main-field disturbance in the field-aligned direction. These disturbances are associated with the ionospheric Pedersen currents, and may introduce systematic errors in internal field models.

Vennerstrøm, Susanne; Moretto, T.

2006-01-01

159

Generation of a symmetric magnetic field by thermal convection in a plane rotating layer  

CERN Document Server

We investigate numerically magnetic field generation by thermal convection with square periodicity cells in a rotating horizontal layer of electrically-conducting fluid with stress-free electrically perfectly conducting boundaries for Rayleigh numbers in the interval 5100\\le R\\le 5800. Dynamos of three kinds, apparently not encountered before, are presented: 1) Steady and time-periodic regimes, where the flow and magnetic field are symmetric about a vertical axis. In regimes with this symmetry, the global alpha-effect is insignificant, and the complex structure of the system of amplitude equations controlling weakly nonlinear stability of the system to perturbations with large spatial and temporal scales suggests that the perturbations are likely to exhibit uncommon complex patterns of behaviour, to be studied in the future work. 2) Periodic in time regimes, where magnetic field is always concentrated in the interior of the convective layer, in contrast to the behaviour first observed by St Pierre (1993) and ...

Zheligovsky, V

2010-01-01

160

Entropy generation during fluid flow in a channel under the effect of transverse magnetic field  

Science.gov (United States)

Entropy generation due to fluid flow and heat transfer inside a horizontal channel made of two parallel plates under the effect of transverse magnetic field is numerically investigated. The flow is assumed to be steady, laminar, hydro-dynamically and thermally fully developed of electrically conducting fluid. Both horizontal walls are maintained at constant temperatures higher than that of the fluid. The governing equations in Cartesian coordinate are solved by an implicit finite difference technique. After the flow field and the temperature distributions are obtained, the entropy generation profiles are computed and presented graphically. The factors, which were found to affect the problem under consideration are the magnetic parameter, Eckert number, Prandtl number, and the temperature parameter (??). It was found that, entropy generation increased as all parameters involved in the present problem increased.

Damseh, R. A.; Al-Odat, M. Q.; Al-Nimr, M. A.

2008-06-01

 
 
 
 
161

Controlled and spontaneous magnetic field generation in a gun-driven spheromak  

International Nuclear Information System (INIS)

In the Sustained Spheromak Physics Experiment, SSPX [E. B. Hooper, D. Pearlstein, and D. D. Ryutov, Nucl. Fusion 39, 863 (1999)], progress has been made in understanding the mechanisms that generate fields by helicity injection. SSPX injects helicity (linked magnetic flux) from 1 m diameter magnetized coaxial electrodes into a flux-conserving confinement region. Control of magnetic fluctuations (?B/B?1% on the midplane edge) yields Te profiles peaked at >200 eV. Trends indicate a limiting beta (?e?4%-6%), and so we have been motivated to increase Te by operating with stronger magnetic field. Two new operating modes are observed to increase the magnetic field: (A) Operation with constant current and spontaneous gun voltage fluctuations. In this case, the gun is operated continuously at the threshold for ejection of plasma from the gun: stored magnetic energy of the spheromak increases gradually with ?B/B?2% and large voltage fluctuations (?V?1 kV), giving a 50% increase in current amplification, Itor/Igun. (B) Operation with controlled current pulses. In this case, spheromak magnetic energy increases in a stepwise fashion by pulsing the gun, giving the highest magnetic fields observed for SSPX (?0.7 T along the geometric axis). By increasing the time between pulses, a quasisteady sustainment is produced (with periodic good confinement), comparing well with resistive magnetohydrodynamic simulations. In each case, the processes that transport the helicity into the spheromak are inductive and exhibit a scaling of field with current that exceeds those previously obtained. We use our newly found scaling to suggest how to achieve higher temperatures with a series of pulses

2005-05-01

162

Evaluation and characterization of fetal exposures to low frequency magnetic fields generated by laptop computers.  

Science.gov (United States)

Portable - or "laptop" - computers (LCs) are widely and increasingly used all over the world. Since LCs are often used in tight contact with the body even by pregnant women, fetal exposures to low frequency magnetic fields generated by these units can occur. LC emissions are usually characterized by complex waveforms and are often generated by the main AC power supply (when connected) and by the display power supply sub-system. In the present study, low frequency magnetic field emissions were measured for a set of five models of portable computers. For each of them, the magnetic flux density was characterized in terms not just of field amplitude, but also of the so called "weighted peak" (WP) index, introduced in the 2003 ICNIRP Statement on complex waveforms and confirmed in the 2010 ICNIRP Guidelines for low frequency fields. For the model of LC presenting the higher emission, a deeper analysis was also carried out, using numerical dosimetry techniques to calculate internal quantities (current density and in-situ electric field) with reference to a digital body model of a pregnant woman. Since internal quantities have complex waveforms too, the concept of WP index was extended to them, considering the ICNIRP basic restrictions defined in the 1998 Guidelines for the current density and in the 2010 Guidelines for the in-situ electric field. Induced quantities and WP indexes were computed using an appropriate original formulation of the well known Scalar Potential Finite Difference (SPFD) numerical method for electromagnetic dosimetry in quasi-static conditions. PMID:22019904

Zoppetti, Nicola; Andreuccetti, Daniele; Bellieni, Carlo; Bogi, Andrea; Pinto, Iole

2011-12-01

163

Generator for scanning the magnetic field in a MNR wide line spectrometer  

International Nuclear Information System (INIS)

A circuit of a generator for fast scanning (0.01-250 s) of a magnetic field is described. The generator is characterized by an increased output power and is intended for use in broad-line spectrometers. The high linearity and stability of output voltage amplitude permit the employment of the generator for operation with a digital storage without using complicated synchronizing circuits. Records of NMR lines of the 297Pb isotope in p-PbTe obtained by a fast scanning method with data storage and a method of differential transmission are presented. They witness to the advantage of the first one (a considerable reduction of the signal recording time)

1980-01-01

164

Photon mass new limits from strong photon-torsion coupling generation of primordial magnetic fields  

CERN Document Server

Recently Adelberger et al [Phys Rev Lett 98: 010402, (2007)] have placed a limit to photon mass by investigating the primordial magnetic fields. Earlier Bertolami et al [Phys Lett \\textbf{B} 455, 96(1999)] showed that massive photons in a spontaneous Lorentz breaking may generate primordial magnetic fields consistent with galactic dynamo seeds. Torsion coupling constant of order $10^{-5}$, much higher than the previously obtained by de Sabbata and Sivaram of $10^{-24}$, leads to strong amplification of magnetic field able to seed galactic dynamo at recombination era contrary to what happens in general relativistic dynamos. This results in $B\\sim{10^{-5}{\\beta}G}$ where ${\\beta}$ is the massive photon-torsion coupling. Thus in order to obtain the observed galaxy field of $B_{G}\\sim{{\\mu}G}$ one should have a coupling $\\beta\\sim{10^{-1}}$, never observed in the universe. Thus we may conclude that the weaker couplings for torsion to e.m fields shall only produce magnetic fields without dynamos starting from extr...

de Andrade, Garcia

2011-01-01

165

Cosmological Magnetic Fields  

CERN Document Server

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.

Kunze, Kerstin E

2013-01-01

166

Experimental studies of the pressures generated by a liquid oxygen slug in a magnetic field  

International Nuclear Information System (INIS)

The strong paramagnetic susceptibility of liquid oxygen (LOX) has established it as a good candidate for a cryogenic magnetic fluid system. While its properties have been known for several decades, a fundamental understanding of the behavior of LOX in a magnetically controlled fluid system is needed for the development of a suitable space application that can operate reliably and efficiently. This study conducted quantitative experiments on the dynamics of a LOX slug in a tube when subjected to electrically-induced magnetic fields within a solenoid. The experiments used a quartz tube with an inner diameter of 1.9 mm and LOX slugs of 0.6, 1.3, 1.9, 2.5, and 3.2 mm length at various initial positions relative to the solenoid. The pressures generated by the motion of the LOX slug under the magnetic force were recorded to characterize the pressure differential generated and the breakdown of the slug. The highest attainable pressure differential was found to be 1.45 kPa, which correlated well to theoretical predictions once the analysis accounted for the resistance heating of the solenoid. The noted differences between experimental results and theory could also be attributed to impeded slug motion from shear and mass forces. Within the workable pressure range, however, an optimal slug length was found which appropriately balances the pressure, shear, and magnetic forces in the system. This paper presents the experimental data on the dynamics and the maximum pressure differential generated by a LOX slug in a magnetic field and discusses the viability of LOX in a magnetic fluid management system intended for space applications.

2010-07-01

167

A Method for Adaptive Mesh Generation Taking into Account the Continuity Requirements of Magnetic Field  

Science.gov (United States)

This paper proposes a method to generate adaptively 2D and 3D finite element meshes taking into account the continuity requirements of the magnetic field at the interface between two neighboring elements. First, this paper proposes a new error estimator that includes the Zienkiewicz and Zhu error norm estimator and the boundary rules in the electromagnetic field. Using a 2D simple model, this paper decides two parameters of the proposed estimator. Next, this paper presents a 3D mesh generation method based on the Voronoi-Delaunay theory, which ensures that the bounding surface of the domain is contained in the triangulation. The method has the capability to decrease the amount of information on the connectivity of boundary nodes by generating nodes not only in the interior of the domain but also on its surface. Two simple magnetostatic field problems are provided to illustrate the usefulness of the proposed method.

Ishikawa, Takeo; Matsunami, Michio

168

Generation and evolution of current carrying plasma clot in external electric and magnetic field  

International Nuclear Information System (INIS)

At the present time the problem of the generation and dynamics of plasma clots in the low temperature plasma flow has attracted considerable interest. The special generated plasma clot can be used for the aerodynamic drag force decreasing, it can be employed as a projectile to destroy tile obstacle and it can be used for the generation of the electrical energy in the external magnetic field. The submitted paper presents results of the experimental and numerical research of the plasma clot generation by means of the capacitor discharge and analysis of the plasma clot evolution in tile supersonic channel in presence of the external magnetic field. It was found that the pressure wave created during the generation stage propagates ahead of the clot. Furthermore the clot moving through the channel takes the shape with the extended wall tails due to its deformation in the nonuniform velocity field. The experiments have been carried out in Eindhoven Shock Tunnel Facility. The experimental facility consists of a shock tube, a channel with a supersonic nozzle and a tank. The products of CO and O2 combustion in the detonation wave which is seeded with Cs are used as a working body. The plasma clot is formed by means of the 10 mks capacitor discharge with energy about 120 J near the throat after the shock-wave startup of the nozzle. The clot transporting through the channel by the gas flow in tile presence of the external magnetic field of 3.3 T generates the electrical current which is measured on the galvanically separated electrode pairs. The streak photography in the middle of the channel is obtained in experiments also. The physical processes studied are simulated by proper numerical models. The modified one-dimensional time-dependent numerical model of the gasdynamic and electrodynamic processes in the experimental facility with the shock tube and the numerical solution of the approximate two-dimensional time-dependent model have been used in numerical analysis

1995-08-04

169

Nonlinear second harmonic generation by light wave-plasma interaction in oscillating magnetic field  

International Nuclear Information System (INIS)

The nonlinear generation of second harmonic electromagnetic waves in a thin inhomogeneous (dense and rarefied) plasma layer (of length d) by obliquely and normal incidence of light wave is analyzed. We consider the effect of external time- dependent magnetic field on the generation and amplification of waves. Two cases are considered, when the magnetic field oscillates at frequency: (i) equal, and (ii) double of that of the incident wave. For normal incidence, waves are not radiated in case (i), while in case (ii) the second harmonics are radiated equally from the plasma boundaries at x = o and x = d. For rarefied plasma, the second harmonics are radiated with equal amplitudes in both cases. (author). 3 refs

1992-01-01

170

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

CERN Document Server

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.

Asenjo, Felipe A; Qadir, Asghar

2012-01-01

171

Net current generation in a 1D quantum ring at zero magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study a non-adiabatic excitation of an electron system in a 1D quantum ring radiated by a short THz pulse. The response of two models, a continuous and discrete, is explored. By introducing a spatial asymmetry in the external perturbation a net current can be generated in the ring at a zero magnetic field. Effect of impurities and ratchets are investigated in combination with symmetric and asymmetric external excitation.

Gylfadottir, Sigridur Sif; Nita, Marian; Gudmundsson, Vidar; Manolescu, Andrei

2004-01-01

172

Langmuir waves generation and detection in a quiescent plasma confined by magnetic multipole field  

International Nuclear Information System (INIS)

Langmuir waves were generated and detected in a plasma with large experimental volume (D = 0.5 m L = 1.0 m), stability and absence of external magnetic fields in the region of interest. These characteristics not only facilitate the data attainment but are also essential for a better comparison between experimental results with the theory. (L.C.J.A.). 5 refs, 5 figs

1991-12-10

173

Back-reactions of dynamo-generated magnetic fields: Torsional oscillations and variations in meridional circulation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The periodically varying Lorentz force of the periodic solar magnetic field generated by the solar dynamo can induce two kinds of motions: torsional oscillations and periodic variations in the meridional circulation. Observational evidence now exists for both these kinds of motions. We discuss our ongoing effort in theoretically studying the variations of the meridional circulation. Then we present our theoretical model of torsional oscillations, which addresses the question...

Choudhuri, Arnab Rai

2011-01-01

174

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

Directory of Open Access Journals (Sweden)

Full Text Available 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.

Roberto De Luca

2011-10-01

175

A numerical model of resistive generation of intergalactic magnetic field at cosmic dawn  

CERN Multimedia

Miniati and Bell (2011) proposed a mechanism for the generation of magnetic seeds that is based the finite resistivity of the low temperature IGM in the high redshift universe. In this model, cosmic-ray protons generated by the first generation of galaxies, escape into the intergalactic medium carrying an electric current that induces return currents, $j_t$, and associated electric fields, $\\vec E=\\eta\\vec j_t$ there. Because the resistivity, $\\eta$, depends on the IGM temperature, which is highly inhomogeneous due to adiabatic contraction and shocks produced by structure formation, a non-vanishing curl of the electric field exists which sustains the growth of magnetic field. In this contribution we have developed an approximate numerical model for this process by implementing the source terms of the resistive mechanism in the cosmological code CHARM. Our numerical estimates substantiate the earlier analysis in Miniati and Bell (2011) which found magnetic seeds between 10$^{-18}$ and 10$^{-16}$ Gauss througho...

Miniati, Francesco

2011-01-01

176

Periodic magnetorotational dynamo action as a prototype of nonlinear magnetic field generation in shear flows  

CERN Document Server

The nature of dynamo action in shear flows prone to magnetohydrodynamic instabilities is investigated using the magnetorotational dynamo in Keplerian shear flow as a prototype problem. Using direct numerical simulations and Newton's method, we compute an exact time-periodic magnetorotational dynamo solution to the three-dimensional dissipative incompressible magnetohydrodynamic equations with rotation and shear. We discuss the physical mechanism behind the cycle and show that it results from a combination of linear and nonlinear interactions between a large-scale axisymmetric toroidal magnetic field and non-axisymmetric perturbations amplified by the magnetorotational instability. We demonstrate that this large scale dynamo mechanism is overall intrinsically nonlinear and not reducible to the standard mean-field dynamo formalism. Our results therefore provide clear evidence for a generic nonlinear generation mechanism of time-dependent coherent large-scale magnetic fields in shear flows and call for new theor...

Herault, J; Cossu, C; Lesur, G; Ogilvie, G I; Longaretti, P -Y

2011-01-01

177

High-magnetic-field MHD-generator program. Quarterly report, January 1, 1981-March 31, 1981  

Energy Technology Data Exchange (ETDEWEB)

Progress in an experimental and theoretical program designed to investigate MHD channel phenomena which are important at high magnetic fields is reported. The areas of research include nonuniformity effects, boundary layers, Hall field breakdown, the effects of electrode configuration and current concentrations, and studies of steady-state combustion disk and linear channels in an existing 6 Tesla magnet of small dimensions. In the study of the effects of nonuniformities, experiments have been performed to test a multi-channel, fiber optics diagnostic system that yields time-resolved temperature profiles in an MHD channel. For the study of magneto-acoustic fluctuation phenomena, a one-dimensional model has been developed to describe the performance of a non-ideal MHD generator with a generalized electrical configuration. The installation of the hardware for the data acquisition and reduction of the laser Doppler velocimeter data, to be used in the study of turbulence suppression in a magnetic field, has been nearly completed. A two-dimensional MHD computer code has been developed which predicts the dependence on electrode and insulator dimensions of the onset of interelectrode Hall field breakdown. Calculations have been performed of the effects of nonuniformities on the flow and electrical behavior of baseload-sized disk generators.

None

1981-04-01

178

Two-dimensional wave instability of flows generated by a rotating magnetic field  

Energy Technology Data Exchange (ETDEWEB)

One way of increasing the hydraulic efficiency of equipment for mixing liquid metals by a rotating magnetic field is by generating hydrodynamic structures that will ensure more intensive transformation of the electromagnetic field into energy of the mechanical motion of the liquid metal as a result of wave effects. With this in mind, the stability of a two-dimensional nonsteady flow generated by a two-dimensional coplanar rotating magnetic field in an infinitely long vessel of circular cross section was studied. The object was to determine whether or not such a flow is stable against two-dimensional wave disturbances and to establish the mechanism by which instability develops. A problem was obtained for small perturbations in a noninductive approximation and wave solutions forming a complete system of orthogonal functions were derived. This system was used as the basis for studying the wave instability of rotational MHD flows. Experimental results for a sharp increase in the velocity of the fluid in the direction of rotation of the magnetic field rotation were used as evidence of energy transmission to the rotational flow from the wave packet moving in the same direction.

Kapusta, A.B.

1988-01-01

179

Mathematical and numerical analysis of the resistive magnetohydrodynamics system with self-generated magnetic field terms  

International Nuclear Information System (INIS)

This work is devoted to the construction of numerical methods that allow the accurate simulation of inertial confinement fusion (ICF) implosion processes by taking self-generated magnetic field terms into account. In the sequel, we first derive a two-temperature resistive magnetohydrodynamics model and describe the considered closure relations. The resulting system of equations is then split in several subsystems according to the nature of the underlying mathematical operator. Adequate numerical methods are then proposed for each of these subsystems. Particular attention is paid to the development of finite volume schemes for the hyperbolic operator which actually is the hydrodynamics or ideal magnetohydrodynamics system depending on whether magnetic fields are considered or not. More precisely, a new class of high-order accurate dimensionally split schemes for structured meshes is proposed using the Lagrange re-map formalism. One of these schemes' most innovative features is that they have been designed in order to take advantage of modern massively parallel computer architectures. This property can for example be illustrated by the dimensionally split approach or the use of artificial viscosity techniques and is practically highlighted by sequential performance and parallel efficiency figures. Hyperbolic schemes are then combined with finite volume methods for dealing with the thermal and resistive conduction operators and taking magnetic field generation into account. In order to study the characteristics and effects of self-generated magnetic field terms, simulation results are finally proposed with the complete two-temperature resistive magnetohydrodynamics model on a test problem that represents the state of an ICF capsule at the beginning of the deceleration phase. (author)

2011-01-01

180

Magnetic field structure of large-scale plasmoid generated by the fast reconnection mechanism in a sheared current sheet  

Digital Repository Infrastructure Vision for European Research (DRIVER)

On the basis of the spontaneous fast reconnection model, three-dimensional magnetic field profiles associated with a large-scale plasmoid propagating along the antiparallel magnetic fields are studied in the general sheared current sheet system. The plasmoid is generated ahead of the fast reconnection jet as a result of distinct compression of the magnetized plasma. Inside the plasmoid, the sheared (east-west) field component has the peak value at the plasmoid center located at x<...

Ugai, M.

2010-01-01

 
 
 
 
181

Dynamics of self-generated, large amplitude magnetic fields following high-intensity laser matter interaction  

CERN Multimedia

The dynamics of magnetic fields with amplitude of several tens of Megagauss, generated at both sides of a solid target irradiated with a high intensity (? 1019W/cm2) picosecond laser pulse, has been spatially and temporally resolved using a proton imaging technique. The amplitude of the magnetic fields is sufficiently large to have a constraining effect on the radial expansion of the plasma sheath at the target surfaces. These results, supported by numerical simulations and simple analytical modeling, may have implications for ion acceleration driven by the plasma sheath at the rear side of the target as well as for the laboratory study of self-collimated high-energy plasma jets.

Sarri, G; Cecchetti, C A; Kar, S; Liseykina, T V; Yang, X H; Dieckmann, M E; Fuchs, J; Galimberti, M; Gizzi, L A; Jung, R; Kourakis, I; Osterholz, J; Pegoraro, F; Robinson, A P L; Romagnani, L; Willi, O; Borghesi, M

2012-01-01

182

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

DEFF Research Database (Denmark)

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.

Erdös, Laszlo; Fournais, Søren

2012-01-01

183

Generation of a spin-polarized electron beam by multipoles magnetic fields  

CERN Multimedia

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 these analysis could prove useful in the design of improved electron microscope.

Karimi, Ebrahim; Boyd, Robert W; Santamato, Enrico

2013-01-01

184

Generation of magnetic field fluctuations in relativistic electron-positron magnetoplasmas  

International Nuclear Information System (INIS)

It is shown that magnetic field aligned equilibrium relativistic plasmas flows can excite electromagnetic fluctuations in a magnetized electron-positron (e-p) plasma. For this purpose, a new dispersion relation is derived by using a relativistic two-fluid model and the Maxwell equations. The dispersion relation admits purely growing instabilities of electromagnetic perturbations across the ambient magnetic field direction. The results have relevance for understanding the origin of magnetic field fluctuations in cosmological and laser-produced plasmas

2007-02-26

185

Generation of magnetic field fluctuations in relativistic electron-positron magnetoplasmas  

Energy Technology Data Exchange (ETDEWEB)

It is shown that magnetic field aligned equilibrium relativistic plasmas flows can excite electromagnetic fluctuations in a magnetized electron-positron (e-p) plasma. For this purpose, a new dispersion relation is derived by using a relativistic two-fluid model and the Maxwell equations. The dispersion relation admits purely growing instabilities of electromagnetic perturbations across the ambient magnetic field direction. The results have relevance for understanding the origin of magnetic field fluctuations in cosmological and laser-produced plasmas.

Shukla, Nitin [Institut fuer Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)]. E-mail: ns@tp4.rub.de; Shukla, P.K. [Institut fuer Theoretische Physik IV and Centre for Plasma Science and Astrophysics, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany) and Max-Planck Institut fuer Extraterrestrische Physik, D-45741 Garching, Germany and Centre for Nonlinear Physics, Department of Physics, Umea University, SE-90187 Umea (Sweden) and CCLRC Centre for Fundamental Physics, Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom) and SUPA, Department of Physics, University of Strathclyde, Glasgow G4 0NG (United Kingdom); GoLP/Centro de Fisica de Plasmas, Instituto Superior Tecnico, 1096 Lisbon Codex (Portugal)]. E-mail: ps@tp4.rub.de

2007-02-26

186

Magnetic fields in galaxies  

CERN Multimedia

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...

Beck, Rainer

2013-01-01

187

Particle Acceleration, Magnetic Field Generation, and Emission in Relativistic Pair Jets  

Science.gov (United States)

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., the Buneman instability, two-streaming instability, and the Weibel instability) created by relativistic pair jets are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet propagating through an ambient plasma with and without initial magnetic fields. The growth rates of the Weibel instability depends on the distribution of pair jets. Simulations show that the Weibel instability created in the collisionless shock accelerates particles perpendicular and parallel to the jet propagation direction. The simulation results show that this instability is responsible for generating and amplifying highly nonuniform, small-scale magnetic fields, which contribute to the electron's transverse deflection behind the jet head. The "jitter" radiation from deflected electrons 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.

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

2005-01-01

188

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

1983-01-01

189

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

Energy Technology Data Exchange (ETDEWEB)

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.

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

190

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

International Nuclear Information System (INIS)

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.

2013-02-01

191

Magnetic Fields of Stars  

Science.gov (United States)

Now it is known about 1212 stars of the main sequence and giants (from them 610 stars - it is chemically peculiarity (CP) stars) for which direct measurements of magnetic fields were spent (Bychkov et al.,2008). Let's consider, what representations were generated about magnetic fields (MT) of stars on the basis of available observations data.

Bychkov, V. D.; Bychkova, L. V.; Madej, J.

192

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

Science.gov (United States)

A device and a method for the production of a magnetic field using a Charge Holding Object that is mechanically rotated. In a preferred embodiment, a Charge Holding Object surrounding a sample rotates and subjects the sample to one or more magnetic fields. The one or more magnetic fields are used by NMR Electronics connected to an NMR Conductor positioned within the Charge Holding Object to perform NMR analysis of the sample.

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

2009-10-13

193

Formation of current filaments and magnetic field generation in a quantum current-carrying plasma  

International Nuclear Information System (INIS)

The nonlinear dynamics of filamentation instability and magnetic field in a current-carrying plasma is investigated in the presence of quantum effects using the quantum hydrodynamic model. A new nonlinear partial differential equation is obtained for the spatiotemporal evolution of the magnetic field in the diffusion regime. This equation is solved by applying the Adomian decomposition method, and then the profiles of magnetic field and electron density are plotted. It is shown that the saturation time of filamentation instability increases and, consequently, the instability growth rate and the magnetic field amplitude decrease in the presence of quantum effects

2013-09-01

194

Formation of current filaments and magnetic field generation in a quantum current-carrying plasma  

Energy Technology Data Exchange (ETDEWEB)

The nonlinear dynamics of filamentation instability and magnetic field in a current-carrying plasma is investigated in the presence of quantum effects using the quantum hydrodynamic model. A new nonlinear partial differential equation is obtained for the spatiotemporal evolution of the magnetic field in the diffusion regime. This equation is solved by applying the Adomian decomposition method, and then the profiles of magnetic field and electron density are plotted. It is shown that the saturation time of filamentation instability increases and, consequently, the instability growth rate and the magnetic field amplitude decrease in the presence of quantum effects.

Niknam, A. R. [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Taghadosi, M. R.; Majedi, S.; Khorashadizadeh, S. M. [Physics Department, University of Birjand, Birjand (Iran, Islamic Republic of)

2013-09-15

195

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

Science.gov (United States)

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.

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

2009-01-01

196

The generation of screw pinch/high-? tokamak configurations using a transverse rotating magnetic field  

International Nuclear Information System (INIS)

Plasma currents can be driven by means of rotating magnetic fields. In this paper an experiment is described which demonstrates that the screw pinch/high-? tokamak configuration can be established using the rotating field technique

1979-01-01

197

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

1999-03-01

198

Magnetic field measurements of the harmonic generation FEL superconducting undulator at BNL-NSLS  

Energy Technology Data Exchange (ETDEWEB)

A three stage superconducting undulator (modulator, dispersive section, and radiator) is under construction at Brookhaven National Laboratory. Sections of the radiator, consisting of 25cm long steel yokes, each with 18mm period, 0.54 Tesla field, and 8.6mm gap are under test. The magnetic measurements and operational characteristics of the magnet are discussed. Measurement results and analysis are presented, with emphasis on the integrated field quality. The magnet winding and the effects of the various trims are discussed.

Solomon, L.; Graves, W.S. [Brookhaven National Lab., Upton, NY (United States); Lehrman, I. [Grumman Aerospace Corp., Princeton, NJ (United States)

1994-12-31

199

Exploring the role of a basal magma ocean in generating Earth's ancient magnetic field  

Science.gov (United States)

Observations of Earth's magnetic field extending back to 3.45 billion years ago indicate that generation by a core dynamo must be sustained over most of Earth's history. However, recent estimates of thermal and electrical conductivity of liquid iron at core conditions from mineral physics experiments indicate that adiabatic heat flux is approximately 15 TW, nearly 3 times larger than previously thought, exacerbating difficulties for driving a core dynamo by convective core cooling alone throughout Earth history. A long-lived basal magma ocean in the lowermost mantle has been proposed to exist in the early Earth, surviving perhaps into the Archean. While the modern, solid lower mantle is an electromagnetic insulator, electrical conductivities of silicate melts are known to be higher, though as yet they are unconstrained for lowermost mantle conditions. Here we explore the geomagnetic consequences of a basal magma ocean layer for a range of possible electrical conductivities. For the highest electrical conductivities considered, we find a basal magma ocean could be a primary dynamo source region. This would suggest the proposed three magnetic eras observed in paleomagnetic data originate from distinct sources for dynamo generation: from 4.5-2.45 Ga within a basal magma ocean, from 2.25-0.4 Ga within a superadiabatically cooled liquid core, and from 0.4-present within a quasi-adiabatic core that includes a solidifying inner core.

Ziegler, Leah; Stegman, Dave

2014-05-01

200

Plasma jet formation and magnetic-field generation in the intense laser plasma under oblique incidence  

Science.gov (United States)

Long-scale jet-like x-ray emission was observed in the experiments on the interactions of 100 TW laser light with plasmas. The jet formation is investigated by simulations with a two-dimensional particle code. When an S-polarized intense laser is irradiated obliquely on an overdense plasma, collimated MeV electrons are observed from the critical surface in the specular reflection direction. These electrons are found to be accelerated through the coronal plasma by the reflected laser light, which was modulated at the reflection point. The quasisteady magnetic channel occurs simultaneously and collimates the energetic electrons along the specular direction. In the case of P-polarized laser, it is found that an outgoing electron stream is induced at the critical surface due to Brunel mechanism. Megagauss quasistatic magnetic fields are generated and pinch the electron stream. The angle of ejected electron depends on the electron's energy. The emission direction of the jet generated by the P-polarized light is determined by the canonical momentum conservation along the target surface.

Sentoku, Y.; Ruhl, H.; Mima, K.; Kodama, R.; Tanaka, K. A.; Kishimoto, Y.

1999-07-01

 
 
 
 
201

Effects of Magnetic Field on Entropy Generation in Flow and Heat Transfer due to a Radially Stretching Surface  

International Nuclear Information System (INIS)

We investigate the effects of magnetic field on the entropy generation during fluid flow and heat transfer due to the radially stretching surface. The partial differential equations governing the flow and heat transfer phenomenon are transformed into nonlinear ordinary differential equations by using suitable similarity transformations. These equations are then solved by the homotopy analysis method and the shooting technique. The effects of the magnetic field parameter M and the Prandtl number Pr on velocity and the temperature profiles are presented. Moreover, influence of the magnetic field parameter M and the group parameter Br/? on the local entropy generation number Ns as well as the Bejan number Be are inspected. It is observed that the magnetic field is a strong source of entropy production in the considered problem

2013-02-01

202

Effects of Magnetic Field on Entropy Generation in Flow and Heat Transfer due to a Radially Stretching Surface  

Science.gov (United States)

We investigate the effects of magnetic field on the entropy generation during fluid flow and heat transfer due to the radially stretching surface. The partial differential equations governing the flow and heat transfer phenomenon are transformed into nonlinear ordinary differential equations by using suitable similarity transformations. These equations are then solved by the homotopy analysis method and the shooting technique. The effects of the magnetic field parameter M and the Prandtl number Pr on velocity and the temperature profiles are presented. Moreover, influence of the magnetic field parameter M and the group parameter Br/? on the local entropy generation number Ns as well as the Bejan number Be are inspected. It is observed that the magnetic field is a strong source of entropy production in the considered problem.

Adnan Saeed, Butt; Asif, Ali

2013-02-01

203

Primordial magnetic field  

Energy Technology Data Exchange (ETDEWEB)

Full text: Magnetic fields are found throughout the cosmos, and models of mechanisms that generate these fields in the present Universe cannot explain all its forms. The fields are detected in the radiation emitted by galaxies, galaxy clusters and superclusters that display patterns of a known phenomena: Zeeman Effect (splitting of the molecular energy lines), Synchrotron Radiation (emitted by relativistic electrons in a magnetic field); Faraday Effect (rotation of the radiation plane of polarization by a magnetic field parallel to its propagation). Such magnetic fields can arise from the Primordial Universe; if it preceded the Cosmic Microwave Background (CMB) radiation, it could be observed today. The wavelengths of the fields found sweep a large region of the spectrum: from nanometers to the size of megaparsec. Its intensity is also quite varied, ranging from micro-Gauss to a few Gauss. We make perturbations in the primordial plasma before the Era of Recombination. In such plasma, the efficient collision between its constituents generates a relative velocity between electrons and protons, creating a magnetic field. In such a way that makes it possible to generate fields of the order of 10{sup -18} G for scales of 1Mpc and 10{sup -14} of 10kpc. The perturbations are made in viscous cosmological model, using Inflation theory. As the disturbance of the density of matter and the generation of gravitational waves behave differently from the magnetic fields produced in the primordial era, we can distinguish them in the power spectrum of current observations. It is possible and interesting to compare the model of primordial magnetic fields with its evolution in nucleosynthesis (which would limit the elements formed) and at CMB radiation. Developed the model and determined its parameters, we determine its limitations with the current observational data. So we are able to speculate the formation of magnetic fields that today fill the Universe within the capability of our model. (author)

Goncalves, Sergio Vitorino de Borba; Scardua, A.C. [Universidade Federal do Espirito Santo (UFES), ES (Brazil)

2011-07-01

204

Magnetic Weibel field generation in thin collisionless current sheets in reconnection in space plasma  

CERN Document Server

In collisionless reconnection in space plasma like the magnetospheric tail or magnetopause current layer, magnetic fields can grow from thermal level by the action of the non-magnetic Weibel instability driven in thin ($\\Delta<$ few $\\lambda_i$) current layers by the counter-streaming electron inflow from the `ion diffusion' (ion inertial Hall) region into the inner current (electron inertial) region from where the ambient magnetic fields are excluded when released by the inflowing electrons which become non-magnetic on scales $<$ few $\\lambda_e$. It is shown that under magnetospheric tail conditions it takes $\\sim 40$ e-folding times ($\\sim 20$ s) for the Weibel field to reach observable amplitudes $|{\\bf b}_{\\rm W}|\\sim 1$ nT. In counter-streaming inflows these fields are predominantly of guide field type. In non-symmetric inflows the field may possess a component normal to the current which would be capable of initiating reconnection onset.

Treumann, R A

2009-01-01

205

Self-generated magnetic field measurements in TEA-CO_2 laser produced plasmas on different targets  

International Nuclear Information System (INIS)

Results of self-generated magnetic field measurements using differential inductive probes in TEA-CO_2 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)

1983-01-01

206

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)

1968-11-01

207

Wall conditioning by microwave generated plasmas in a toroidal magnetic field  

International Nuclear Information System (INIS)

The suitability of microwave generated plasmas for the purpose of wall coating in pure toroidal magnetic fields is investigated in a special test bench. We report on the results of layer deposition using methane plasmas as a systematic case study for future boron or silicon deposition by other gases (B2H6,SiH4). The produced coatings can be characterized as polymer-like soft a-C:D-films with a high D/C-ratio due to the low energy of particles hitting the wall. Neutral hydrocarbon radicals could be identified to play the major role for film deposition. On the other hand, strong re-erosion induced by deuterium ions is observed in regions with plasma-wall contact. The spatial homogeneity and the characteristics of produced coatings are presented and observations are correlated with measured plasma parameters. The use of pulsed plasmas for wall conditioning is compared with steady-state discharges

2001-03-01

208

Weibel Instability Driven by Relativistic Pair Jets: Particle Acceleration, Magnetic Field Generation, and Emission  

CERN Document Server

Shock acceleration is a ubiquitous phenomenon in astrophysical plasmas. Plasma waves and their associated instabilities (e.g., Buneman, Weibel and other two-stream instabilities) created in collisionless shocks are responsible for particle (electron, positron, and ion) acceleration. Using a 3-D relativistic electromagnetic particle (REMP) code, we have investigated particle acceleration associated with a relativistic jet front propagating into an ambient plasma. We find that the growth times of the Weibel instability in electron-positron jets are not affected by the (electron-positron or electron-ion) ambient plasmas. However, the amplitudes of generated local magnetic fields in the electron-ion ambient plasma are significantly larger than those in the electron-positron ambient plasma.

Nishikawa, K I; Hededal, C B; Richardson, G; Sol, H; Preece, R; Fishman, G J

2005-01-01

209

Wall conditioning by microwave generated plasmas in a toroidal magnetic field  

Science.gov (United States)

The suitability of microwave generated plasmas for the purpose of wall coating in pure toroidal magnetic fields is investigated in a special test bench. We report on the results of layer deposition using methane plasmas as a systematic case study for future boron or silicon deposition by other gases (B 2H 6,SiH 4). The produced coatings can be characterized as polymer-like soft a-C:D-films with a high D/C-ratio due to the low energy of particles hitting the wall. Neutral hydrocarbon radicals could be identified to play the major role for film deposition. On the other hand, strong re-erosion induced by deuterium ions is observed in regions with plasma-wall contact. The spatial homogeneity and the characteristics of produced coatings are presented and observations are correlated with measured plasma parameters. The use of pulsed plasmas for wall conditioning is compared with steady-state discharges.

Ihde, J.; Störk, H. B.; Winter, J.; Rubel, M.; Esser, H. G.; Toyoda, H.

2001-03-01

210

Generation of strong quasistatic magnetic fields in interactions of ultraintense and short laser pulses with overdense plasma targets.  

Science.gov (United States)

An analytical fluid model is proposed for the generation of strong quasistatic magnetic fields during normal incidence of a short ultraintense Gaussian laser pulse with a finite spot size on an overdense plasma. The steepening of the electron density profile in the originally homogeneous overdense plasma and the formation of electron cavitation as the electrons are pushed inward by the laser are included self-consistently. It is shown that the appearance of the cavitation plays an important role in the generation of quasistatic magnetic fields: the strong plasma inhomogeneities caused by the formation of the electron cavitation lead to the generation of a strong axial quasistatic magnetic field Bz. In the overdense regime, the generated quasistatic magnetic field increases with increasing laser intensity, while it decreases with increasing plasma density. It is also found that, in a moderately overdense plasma, highly intense laser pulses can generate magnetic fields approximately 100 MG and greater due to the transverse linear mode conversion process. PMID:17930347

Cai, Hong-bo; Yu, Wei; Zhu, Shao-ping; Zhou, Cang-tao

2007-09-01

211

Virtual cathode microwave generation using inhomogeneous magnetic field and wave guide wall configuration  

International Nuclear Information System (INIS)

Microwave generation from a virtual cathode system is investigated using two-dimensional particle-in-cell simulation. In the typical virtual cathode geometry, the electron beam diode is separated from the output waveguide by a ground plane which is a thin foil or screen. By lowering the diode impedance sufficiently, it is possible to form a virtual cathode in the waveguide region a short distance from the ground plane. In this configuration two mechanisms can lead to microwave generation: 1) electron bunching due to reflection between the real and virtual cathode and 2) electron bunching due to virtual cathode oscillation. Both mechanisms are typically present, but it appears possible to make one mechanism dominant by adjusting the output waveguide radius. Although such a configuration might generate 1-10 GW output, electron deposition into the ground plane, waveguide wall, and output window causes breakdown. To overcome these disadvantages, the authors have investigated a configuration with no ground plane coupled with the use of an inhomogeneous external magnetic field and waveguide wall

1984-01-01

212

New performance in harmonic analysis device generation used for magnetic fields measurements  

International Nuclear Information System (INIS)

In particle accelerator, correcting high multipole components of magnets are of high importance for quality magnet: to get a pure quadrupole to within 10"-"4, we have to know the field quality to 10"-"5 through the 30. order. Our laboratory needed such a very sharp device to find small harmonic components of magnetic field. For harmonic analysis of magnetic field, we adopted the standard method, i.e. a rotating coil connected to a flux integrator. Nowadays, coils measuring azimuthal component of magnetic field are used. In order to obtain correct and accurate measurements, we were guided by two imperatives: first, optimisation of construction constraints and second, comparison of azimuthal and radial component measurements. With this background, this article describes both new technological solutions adopted and new performance obtained. We also discuss the most suitable geometric structure for the coils. We obtained a noiseless signal, a repeatability of 10"-"5 and a sensitivity up to 10"-"8 Weber for both types of coils. Our device is able to find and measure main component, normal and skew multipole components up to the 32. order, when simulating local defects. The magnetic axis is located within 5 ?m. The central gradient is also measured and magnetic length deduced. Complementary functions of two types of coils were noticed in detecting local defects of magnetic structure. (authors)

1996-01-01

213

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.)

1985-06-01

214

Hamilton flow generated by field lines near a toroidal magnetic surface  

Energy Technology Data Exchange (ETDEWEB)

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.

Skovoroda, A. A., E-mail: skovorod@nfi.kiae.ru [National Research Center Kurchatov Institute (Russian Federation)

2013-07-15

215

Hamilton flow generated by field lines near a toroidal magnetic surface  

Science.gov (United States)

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.

Skovoroda, A. A.

2013-07-01

216

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

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

2006-01-01

217

Effects of Radiation Heat Transfer on Entropy Generation at Thermosolutal Convection in a Square Cavity Subjected to a Magnetic Field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Thermosolutal convection in a square cavity filled with a binary perfect gas mixture and submitted to an oriented magnetic field taking into account the effect of radiation heat transfer is numerically investigated. The cavity is heated and cooled along the active walls whereas the two other walls are adiabatic and insulated. Entropy generation due to heat and mass transfer, fluid friction and magnetic effect has been determined for laminar flow by solving numerically: The continuity, momentu...

Nejib Hidouri; Mounir Bouabid; Mourad Magherbi; Ammar Ben Brahim

2011-01-01

218

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)

2006-05-15

219

Dynamical Feedback of Self-generated Magnetic Fields in Cosmic Rays Modified Shocks  

Energy Technology Data Exchange (ETDEWEB)

We present a semi-analytical kinetic calculation of the process of non-linear diffusive shock acceleration (NLDSA) which includes magnetic field amplification due to cosmic ray induced streaming instability, the dynamical reaction of the amplified magnetic field and the possible effects of turbulent heating. This kinetic calculation allows us to show that the net effect of the amplified magnetic field is to enhance the maximum momentum of accelerated particles while reducing the concavity of the spectra, with respect to the standard predictions of NLDSA. This is mainly due to the dynamical reaction of the amplified field on the shock, which smoothens the shock precursor. The total compression factors which are obtained for parameters typical of supernova remnants are R{sub tot} {approx} 7-10, in good agreement with the values inferred from observations. The strength of the magnetic field produced through excitation of streaming instability is found in good agreement with the values inferred for several remnants if the thickness of the X-ray rims are interpreted as due to severe synchrotron losses of high energy electrons. We also discuss the relative role of turbulent heating and magnetic dynamical reaction in smoothening the shock precursor.

Caprioli, D.; /Pisa, Scuola Normale Superiore; Blasi, P.; /Arcetri Observ. /Fermilab; Amato, E.; /Arcetri Observ.; Vietri, M.; /Pisa, Scuola Normale Superiore

2008-07-01

220

NOAA/NGDC candidate models for the 11th generation International Geomagnetic Reference Field and the concurrent release of the 6th generation Pomme magnetic model  

Science.gov (United States)

The International Geomagnetic Reference Field (IGRF) is updated every five years based on candidate model submissions by research institutions worldwide. In the call for the 11th generation of IGRF, candidates were requested for the definitive main field in 2005, the predicted main field in 2010, and the predicted secular variation from 2010 to 2015. The NOAA/NGDC candidate models for IGRF-11 were produced from parent models parameterized in the same way as the 6th generation of our Pomme magnetic model. All models were based on CHAMP satellite measurements, while Ørsted satellite measurements were used for model validation. The internal field in Pomme-6 is described by a 2nd degree Taylor time series of spherical harmonic expansion coefficients of a scalar magnetic potential. Magnetic fields of ionospheric origin are avoided by careful data selection. Instead of co-estimating magnetospheric fields, we subtract a magnetospheric field model estimated previously from a more extensive data set covering all local times. From comparison with Örsted measurements and general considerations of magnetic field predictability, we attribute a root mean square (RMS) uncertainty of 1.3 nT to our candidate model for the main field in 2005, 2.5 nT to the predicted main field in 2010 and 26 nT/a to the predicted secular variation from 2010 to 2015.

Maus, S.; Manoj, C.; Rauberg, J.; Michaelis, I.; Lühr, H.

2010-10-01

 
 
 
 
221

Use of second generation coated conductors for efficient shielding of DC magnetic fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper reports the results of an experimental investigation of the performance of two types of magnetic screens assembled from YBa2Cu3O7-d (YBCO) coated conductors. Since effective screening of the axial DC magnetic field requires the unimpeded flow of an azimuthal persistent current, we demonstrate a configuration of a screening shell made out of standard YBCO coated conductor capable to accomplish that. The screen allows the persistent current to flow in the predominantly azimuthal dire...

Fagnard, Jean-francois; Dirickx, Michel; Levin, G. A.; Barnes, P. N.; Vanderheyden, Benoi?t; Vanderbemden, Philippe

2010-01-01

222

Experimental Observation of Optical Rotation Generated in Vacuum by a Magnetic Field  

International Nuclear Information System (INIS)

We report the experimental observation of a light polarization rotation in vacuum in the presence of a transverse magnetic field. Assuming that data distribution is Gaussian, the average measured rotation is (3.9±0.5)x10-12 rad/pass, at 5 T with 44 000 passes through a 1 m long magnet, with ?=1064 nm. The relevance of this result in terms of the existence of a light, neutral, spin-zero particle is discussed

2006-03-24

223

Experimental observation of optical rotation generated in vacuum by a magnetic field  

CERN Document Server

We report the experimental observation of a light polarization rotation in vacuum in the presence of a transverse magnetic field. Assuming that data distribution is Gaussian, the average measured rotation is(3.9+/-0.5)e-12 rad/pass, at 5 T with 44000 passes through a 1 m long magnet. One possible interpretation of this result is the existence of a light, neutral, pseudoscalar particle coupled to two photons.

Zavattini, E; Ruoso, G; Polacco, E; Milotti, E; Karuza, M; Gastaldi, Ugo; Domenico, G D; Valle, F D; Cimino, R; Carusotto, S; Cantatore, G; Bregant, M

2006-01-01

224

Generation of a modulated IREB (intense relativistic electron beam) with a frequency tunable by a magnetic field  

International Nuclear Information System (INIS)

The present invention comprises a device for generating a modulated intense relativistic beam (IREB) with an electronically tunable frequency, comprising: a longitudinally running drift tube; a plurality of gaps in the drift tube including first gap and a second gap, disposed with a predetermined distance therebetween; and a plurality of cavities, with a first cavity disposed around the drift tube at the location of the first gap, and a second cavity disposed around the drift tube at the location of the second gap. These first and second cavities are provided with volumes and a geometry such as to excite a predetermined frequency band below the plasma frequency for the device. A circuit is provided for generating an IREB and injecting this IREB to propagate within the drift tube with a predetermined-plasma frequency. Additionally, a main magnetic field generating means is provided for generating an IREB and injecting this IREB to a desired beam diameter. The frequency tuning is obtained by providing an auxiliary magnetic field running parallel to and within the drift tube and located only along a predetermined length between the first and second gaps, with this auxiliary magnetic field running parallel to and within the drift tube and located along a predetermined length between first and second gaps, with this auxiliary magnetic field being tunable to thereby tune the frequencies of excitations in the first and second gaps. Finally, a means is provided at one end of the drift tube for converting the kinetic energy of the IREB into electrical energy

1985-01-01

225

Thermal convection and generation of large-scale magnetic fields in the inner regions of accretion discs around black holes  

International Nuclear Information System (INIS)

The theory of thermal convection in the inner region of an accretion disc (IRAD) is investigated. The characteristic time of development of the convective instability is determined, which, at the optimal configuration of the convective cells, proved to be of the order of the disc's revolution time. The effect of the differential rotation and azimuthal magnetic field on this instability is studied. The following quantities are estimated with the use of the equations of the turbulent dynamo in the disc: growth time of the large-scale magnetic field, the relations between the components of this field, and the maximum value-scale magnetic field, which can be generated in the inner region of the accretion disc in the framework of our model

1983-01-01

226

Simulations of electron generation and dynamics in a hollow cathode with applied magnetic field  

International Nuclear Information System (INIS)

Hollow cathode devices are promising as compact electron and ion sources, as sources for radiation and as fast switches for pulsed power applications. Researchers have shown in previous work how one can use an applied magnetic field to induce large impedance changes in a hollow cathode system, with possible applications to switching. Using an electrostatic particle-in-cell (PIC) code, we explore the dynamics of a hollow cathode device including an applied magnetic field. We show results for the full kinetic energy distribution of the electrons, demonstrating the formation of pendular electrons with no magnetic field and the inhibition of pendular electrons with a magnetic field. Our results also show the pendular electrons that form in the case of no applied field have a distribution indicating they undergo up to 10 ionization events, with four being the most likely number of events. Finally, we use an approximate radiation diagnostic to show that our results agree qualitatively with the experimental results of Rocca and Floyd

2007-08-01

227

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.

2011-01-01

228

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Alves, E. P.; Grismayer, T.; Fonseca, R. A.; Silva, L. O.

2014-01-01

229

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%

1992-01-01

230

Generation of 1.5-kW, 1-THz coherent radiation from a gyrotron with a pulsed magnetic field.  

Science.gov (United States)

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 musec 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. PMID:18232780

Glyavin, M Yu; Luchinin, A G; Golubiatnikov, G Yu

2008-01-11

231

Simulation Study of Magnetic Fields generated by the Electromagnetic Filamentation Instability driven by Pair Loading  

Science.gov (United States)

Using a 3-D relativistic particle-in-cell (RPIC) code, we have investigated particle acceleration associated with a relativistic electron-positron (cold) jet propagating into ambient electron-positron and electron-ion plasmas without initial magnetic fields in order to investigate the nonlinear stage of the Weibel instability. We have also performed simulations with broad Lorentz factor distribution of jet electrons and positrons, which are assumed to be created by the photon annihilation. The growth time and nonlinear saturation levels depend on the initial jet parallel velocity distributions and ambient plasma. Simulations show that the Weibel instability created in the collisionless shocks accelerates jet and ambient particles both perpendicular and parallel to the jet propagation direction. The nonlinear fluctuation amplitude of densities, currents, electric, and magnetic fields in the electron-ion ambient plasma are larger than those in the electron-positron ambient plasma. We have shown that plasma instabilities driven by these streaming electron-positron pairs are responsible for the excitation of near-equipartition, turbulent magnetic fields. These fields maintain a strong saturated level on timescales much longer than the electron skin depth at least for the duration of the simulations. Our results reveal the importance of the electromagnetic filamentation instability in ensuring an effective coupling between electron-positron pairs and ions, and may help explain the origin of large upstream fields in GRB shock.

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

2007-01-01

232

Generation of the sheared radial electric field by a magnetic island structure  

Directory of Open Access Journals (Sweden)

Full Text Available The effect of the presence of a magnetic island structure on the am bipolar radial electric field is studied in the context of the belt island model. It is shown that the sheared radial electric field region exists on the island position. Depending on the model parameters, the single (ion root or multiple (one ion and two electron roots solutions for the radial electric field are obtained at different radial positions. The radially non-local treatment is developed proposing the steady-state plasma conditions. The numerical calculations show that the diffusion of the radial electric field is significant only near the island boundaries. As a result the discontinuities in the am bipolar electric field profile are smoothed.

Man?i? Ana

2004-01-01

233

Influence of the Backreaction of Streaming Cosmic Rays on Magnetic Field Generation and Thermal Instability  

Science.gov (United States)

Using a multifluid approach, we investigate streaming and thermal instabilities of the electron-ion plasma with homogeneous cold cosmic rays propagating perpendicular to the background magnetic field. Perturbations are also considered to be across the magnetic field. The backreaction of cosmic rays resulting in strong streaming instabilities is taken into account. It is shown that, for sufficiently short wavelength perturbations, the growth rates can exceed the growth rate of cosmic-ray streaming instability along the magnetic field, found by Nekrasov & Shadmehri, which is in turn considerably larger than the growth rate of the Bell instability. The thermal instability is shown not to be subject to the action of cosmic rays in the model under consideration. The dispersion relation for the thermal instability has been derived, which includes sound velocities of plasma and cosmic rays and Alfvén and cosmic-ray streaming velocities. The relation between these parameters determines the kind of thermal instability ranging from the Parker to the Field instabilities. The results obtained can be useful for a more detailed investigation of electron-ion astrophysical objects, such as supernova remnant shocks, galaxy clusters, and others, including the dynamics of streaming cosmic rays.

Nekrasov, Anatoly K.; Shadmehri, Mohsen

2014-06-01

234

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

1992-10-01

235

Generation of zonal magnetic fields by drift waves in a current carrying nonuniform magnetoplasma  

Energy Technology Data Exchange (ETDEWEB)

It is shown that zonal magnetic fields (ZMFs) can be nonlinearly excited by incoherent drift waves (DWs) in a current carrying nonuniform magnetoplasma. The dynamics of incoherent DWs in the presence of ZMFs is governed by a wave-kinetic equation. The governing equation for ZMFs in the presence of nonlinear advection force of the DWs is obtained from the parallel component of the electron momentum equation and the Faraday law. Standard techniques are used to derive a nonlinear dispersion relation, which depicts instability via which ZMFs are excited in plasmas. ZMFs may inhibit the turbulent cross-field particle and energy transport in a nonuniform magnetoplasma.

Shukla, Nitin [Department of Physics, Umea University, SE-90187 Umea (Sweden); Shukla, P.K., E-mail: ps@tp4.rub.d [Institut fuer Theoretische Physik IV, Fakultaet fuer Physik und Astronomie, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2010-05-17

236

Effect of Particle Size of Magnetite Nanoparticles on Heat Generating Ability under Alternating Magnetic Field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this study, magnetite nanoparticles (MNPs) with series of size varying from 8nm to 103nm were synthesized by a chemical co-precipitation and an oxidation-precipitation method to aim for finding the optimum particle size which has high heating efficiency in the applied magnetic field (9.6?23.9 kA·m?¹, 100kHz). Their in vitro heating efficiencies in agar phantom, at a MNPs concentration of 58mg Fe·ml?¹, were measured in the applied field. The temperature increase...

Li, Z.; Kawashita, M.; Araki, N.; Mistumori, M.; Hiraoka, M.

2011-01-01

237

Effects of density profile steepening on generation of suprathermal particles, harmonics and magnetic fields in a laser produced plasma  

International Nuclear Information System (INIS)

The propagation of obliquely incident p-polarized laser radiation through a laser plasma with a density profile steepening in the domain of the critical point is considered. Such a density profile seems to be a long term profile in a laser produced plasma. It is shown that the structure of the laser radiation electric field is significantly changed in reference to Ginzburg's treatment. In the case of total absorption of the laser radiation a simple expression for the electric field is obtained. The effects of such a new structure of the electric field on the generation of suprathermal particles, harmonics and magnetic fields is considered. It is shown that in this field, ions (due to the ponderomotive force) could be accelerated up to the energies of the order of 10 keV. It is also shown that such a structure of the electric field significantly affects generation of magnetic fields (by the p-component of the laser radiation electric field) in plasma. Finally, it is shown that due to the density profile steepening a direct transformation (as a consequence of parametric instability) of laser radiation into ?_0.2"-"1 harmonic takes place. (author)

1982-02-01

238

Magnetic Field and Life  

Science.gov (United States)

This is a lesson where learners explore magnetic forces, fields, and the relationship between electricity. Learners will use this information to infer how the Earth generates a protective magnetic field. The lesson models scientific inquiry using the 5E instructional model and includes teacher notes, prerequisite concepts, common misconceptions, student journal and reading. This is lesson seven in the Astro-Venture Geology Training Unit that were developed to increase students' awareness of and interest in astrobiology and the many career opportunities that utilize science, math and technology skills. The lessons are designed for educators to use with with the Astro-Venture multimedia modules.

239

Generation of enhanced-scalelength plasmas and Zeeman study of magnetic fields  

International Nuclear Information System (INIS)

Using nonuniform laser illumination on flat targets, with moderate laser energies (200 J), we have produced enhanced density scalelengths; e.g., in excess of 0.5 mm at 0.1 of critical density. These enhanced scalelengths are of interest in simulating large, high-gain pellets, and investigating the potential impact of longer scalelengths on a variety of convective plasma instabilities. The nonuniform laser irradiation also affects the spontaneous magnetic fields. These fields were measured for the first time using the Zeeman effect. Space-and-time-resolved measurements, for both polarizations, were made of the 2271-2278 A CV triplets (2s_3S"1 - 2p_3P"2,"1,"0) emission. A comparison with theory gave fields around 200 kG

1982-05-10

240

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

Directory of Open Access Journals (Sweden)

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.

Moh'd A. Al-Nimr

2004-06-01

 
 
 
 
241

On the problem of large-scale magnetic field generation in rotating compressible convection  

CERN Document Server

Mean-field dynamo theory suggests that turbulent convection in a rotating layer of electrically-conducting fluid produces a significant alpha-effect, which is one of the key ingredients in any mean-field dynamo model. Provided that this alpha-effect operates more efficiently than (turbulent) magnetic diffusion, such a system should be capable of sustaining a large-scale dynamo. However, in the Boussinesq model that was considered by Cattaneo&Hughes (2006) the dynamo produced small-scale, intermittent magnetic fields with no significant large-scale component. In this paper, we consider the compressible analogue of the rotating convective layer that was considered by Cattaneo&Hughes (2006). Varying the horizontal scale of the computational domain, we investigate the dependence of the dynamo upon the rotation rate. Our simulations indicate that these turbulent compressible flows can drive a small-scale dynamo but, even when the layer is rotating very rapidly (with a mid-layer Taylor number of Ta=10^8), w...

Favier, Benjamin

2013-01-01

242

Effects of metallurgical microstructure of armatures on compressed magnetic field generators  

International Nuclear Information System (INIS)

Methods for improving uniform expansion behavior of compressed magnetic field device armatures were studied. Initial microstructure of the copper tubes was altered in a controlled manner by using different forming techniques and alloying. Results show a 25 to 50% improvement in uniform explosive expansion radius for electroformed and spun copper armatures compared to standard armatures machined from drawn tubing. Expansion improvement has been correlated with changes in the mechanical texture due to forming. The smoother expansion, however, did not result in a significantly higher electrical efficiency with the armature parameters tested

1979-06-01

243

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

Directory of Open Access Journals (Sweden)

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.

Józef Kunc

1971-01-01

244

Wakefield generation in magnetized plasmas  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider wakefield generation in plasmas by electromagnetic pulses propagating perpendicular to a strong magnetic field, in the regime where the electron cyclotron frequency is equal to or larger than the plasma frequency. PIC-simulations reveal that for moderate magnetic field strengths previous results are re-produced, and the wakefield wavenumber spectrum has a clear peak at the inverse skin depth. However, when the cyclotron frequency is significantly larger than the ...

Holkundkar, A.; Brodin, G.; Marklund, M.

2011-01-01

245

Simulation Study of Magnetic Fields Generated by the Electromagnetic Filamentation Instability  

Science.gov (United States)

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.

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

2007-01-01

246

Primordial Magnetic Fields in Cosmology  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Magnetic fields have been observed in galaxies, clusters of galaxies and probably in superclusters. While mechanisms exist to generate these in the late universe, it is possible that magnetic fields have existed since very early times. This thesis is concerned with methods to predict the form of such imprints. We review in detail a standard, linearised cosmology before introducing an electromagnetic field. We then consider the intrinsic statistics of the magnetic stresses in...

Brown, Iain A.

2008-01-01

247

Health effects of magnetic fields generated from power lines: new clues for an old puzzle  

International Nuclear Information System (INIS)

Thirty years ago, Nancy Wertheimer and Ed Leeper published the first report on the association between childhood cancer and electrical current configuration of houses in Denver, Colorado. In 2001 the International Agency for Research on Cancer defined 50-60 Hz magnetic fields as possibly carcinogenic to humans because of the limited evidence of carcinogenicity of residential exposure relatively to childhood leukemia. With respect to health effects other than cancer, namely neuro degenerative disorders, miscarriage, subtle differences in the timing of melatonin release, altered autonomic control of the heart, and changes in the number of natural killer cells, some open questions still remain. Several authors recommended further investigation of the possible long-term effects of magnetic fields, focussing on populations experiencing high exposure levels. In this frame a research team of ISS searched for a suitable location to implement an epidemiological study aimed at a wide range of outcomes for which a priori hypotheses could be formulated. The recently published findings of this project showed an increase of primary and secondary malignant neoplasms, ischaemic disease and haematological diseases. Future studies should thus address the most exposed sectors of the population, take into account different outcomes (all neoplasms, neuro degenerative diseases, immunological disorders, specific cardiovascular effects) and follow research protocols that enable subsequent pooled analyses. A precautionary approach may provide the frame for decision making where the available resources for environmental remediation be prioritatively allocated to worst-off situations.

2009-01-01

248

Efficient laser-overdense plasma coupling via surface plasma waves and steady magnetic field generation  

Energy Technology Data Exchange (ETDEWEB)

The efficiency of laser overdense plasma coupling via surface plasma wave excitation is investigated. Two-dimensional particle-in-cell simulations are performed over a wide range of laser pulse intensity from 10{sup 15} to 10{sup 20} W cm{sup -2}{mu}m{sup 2} with electron density ranging from 25 to 100n{sub c} to describe the laser interaction with a grating target where a surface plasma wave excitation condition is fulfilled. The numerical studies confirm an efficient coupling with an enhancement of the laser absorption up to 75%. The simulations also show the presence of a localized, quasi-static magnetic field at the plasma surface. Two interaction regimes are identified for low (I{lambda}{sup 2} < 10{sup 17} W cm{sup -2}{mu}m{sup 2}) and high (I{lambda}{sup 2} > 10{sup 17} W cm{sup -2}{mu}m{sup 2}) laser pulse intensities. At ''relativistic'' laser intensity, steady magnetic fields as high as {approx}580 MG {mu}m/{lambda}{sub 0} at 7 x 10{sup 19} W cm{sup -2}{mu}m{sup 2} are obtained in the simulations.

Bigongiari, A. [CEA/DSM/LSI, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); TIPS/LULI, Universite Paris 6, CNRS, CEA, Ecole Polytechnique, 3, rue Galilee 94200, Ivry-sur-Seine (France); Raynaud, M. [CEA/DSM/LSI, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); Riconda, C. [TIPS/LULI, Universite Paris 6, CNRS, CEA, Ecole Polytechnique, 3, rue Galilee 94200, Ivry-sur-Seine (France); Heron, A. [CPHT, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); Macchi, A. [Consiglio Nazionale delle Ricerche, Istituto Nazionale di Ottica (CNR/INO), Dipartimento di Fisica ' ' E. Fermi' ' , Largo B. Pontecorvo 3, 56127 Pisa (Italy)

2011-10-15

249

CAVMA3 - an IBM 360/75 code for calculating axial and radial components of the magnetic field generated by a finite-dimensions axially symmetrical coil; application to the experiment of magnetic scattering in nuclear reactor  

CERN Document Server

CAVMA3 - an IBM 360/75 code for calculating axial and radial components of the magnetic field generated by a finite-dimensions axially symmetrical coil; application to the experiment of magnetic scattering in nuclear reactor

Franco, F; Pedretti, E no 1; Franco, F no 1

1973-01-01

250

Solar Magnetic Fields  

CERN Multimedia

This review provides an introduction to the generation and evolution of the Sun's magnetic field, summarising both observational evidence and theoretical models. The eleven year solar cycle, which is well known from a variety of observed quantities, strongly supports the idea of a large-scale solar dynamo. Current theoretical ideas on the location and mechanism of this dynamo are presented. The solar cycle influences the behaviour of the global coronal magnetic field and it is the eruptions of this field that can impact on the Earth's environment. These global coronal variations can be modelled to a surprising degree of accuracy. Recent high resolution observations of the Sun's magnetic field in quiet regions, away from sunspots, show that there is a continual evolution of a small-scale magnetic field, presumably produced by small-scale dynamo action in the solar interior. Sunspots, a natural consequence of the large-scale dynamo, emerge, evolve and disperse over a period of several days. Numerical simulation...

Hood, Alan W

2011-01-01

251

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

Energy Technology Data Exchange (ETDEWEB)

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 {approx}10{sup 13} W/cm{sup 2}. It is also possible to use this device in other configurations to get time resolved information.

Prasad, Y. B. S. R.; Barnwal, S.; Naik, P. A.; Kamath, M. P.; Joshi, A. S.; Kumbhare, S. R.; Gupta, P. D. [Laser Plasma Division, Raja Ramanna Centre for Advanced Technology, Indore 452013 (India); Bolkhovitinov, E. A.; Rupasov, A. A. [Laboratory of Plasma Diagnostics, P.N. Lebedev Physical Institute, 53 Leninsky Prospekt, Moscow 117924 (Russian Federation)

2011-12-15

252

Second harmonic generation in laser-plasma interactions in the present of a wiggler magnetic field by using of photonic crystal theory  

International Nuclear Information System (INIS)

Interaction of a ultra short laser pulse with nonmagnetic isotropic plasma produce many nonlinear phenomena such as generation of odd harmonics. In the presence of a magnetic field, anisotropic plasma is converted to a non isotropic plasma and leads to generate even harmonics. In nonlinear optical processes such as second harmonic generation, the phase matching condition, which is an important character to obtain a large output, is given by the conservation of the momentum. In order to providing phase-matching condition, it is exerting a spatial periodic magnetic field (Wiggler magnetic field) in order to create a structure such as photonic crystal.

2007-08-27

253

Solar magnetic fields and activity  

International Nuclear Information System (INIS)

The author summarizes the experience of a solar observer dealing with the dynamics of solar background magnetic fields formation, including the development of new active regions magnetic fluxes. Single active regions occurrences, complexes of activity and proton-flare region related large-scale regular magnetic patterns growths are investigated. The meaning and importance of magnetic active longitudes are indicated. The physical background of magnetic fields generation in connection with convection, differential rotation and especially with the photospheric surface kinematics of the background fields is discussed. (Auth.)

1982-01-01

254

LEC growth of semi-insulating GaAs crystals in traveling magnetic field generated in a heater-magnet module  

Science.gov (United States)

For the first time semi-insulating (SI) GaAs single crystals were grown by the liquid encapsulated Czochralski (LEC) method using a traveling magnetic field (TMF) system generated in a heater-magnet module (HMM). The system was developed within the framework of the KRISTMAG project. The HMM, that generates heat and TMF simultaneously, was placed closely around the crucible inside the chamber of the industrial CI 358 puller. Before the growth experiments the induced vertical Lorentz force density F Lz was evaluated by the weight force response of a dummy. First growth experiments at various f/ ? ratios ( f—frequency and ?—phase shift) were carried out. Interface morphology and temperature fluctuation strengths were analyzed by a striation technique. Etch pit density, carbon, residual impurity and EL2° contents as well as electrical properties of the as-grown TMF-LEC GaAs crystals were measured. A preliminary correlation between crystal qualities and field frequency has been noticed.

Rudolph, P.; Czupalla, M.; Lux, B.

2009-10-01

255

Resonant magnetic fields from inflation  

CERN Document Server

We propose a novel scenario to generate primordial magnetic fields during inflation induced by an oscillating coupling of the electromagnetic field to the inflaton. This resonant mechanism has two key advantages over previous proposals. First of all, it generates a narrow band of magnetic fields at any required wavelength, thereby allaying the usual problem of a strongly blue spectrum and its associated backreaction. Secondly, it avoids the need for a strong coupling as the coupling is oscillating rather than growing or decaying exponentially. Despite these major advantages, we find that the backreaction is still far too large during inflation if the generated magnetic fields are required to have a strength of ${\\cal O}(10^{-15}\\, \\Gauss)$ today on observationally interesting scales. We provide a more general no-go argument, proving that this problem will apply to any model in which the magnetic fields are generated on subhorizon scales and freeze after horizon crossing.

Byrnes, Christian T; Jain, Rajeev Kumar; Urban, Federico R

2012-01-01

256

Linear Magnetic Motor/Generator.  

Science.gov (United States)

A linear magnetic motor/generator is disclosed which uses magnetic flux to provide mechanical motion or electrical energy. The linear magnetic motor/generator includes an axially movable actuator mechanism. A permament magnet mechanism defines a first mag...

P. A. Studer

1982-01-01

257

Magnetic field-effect transistor  

International Nuclear Information System (INIS)

The magnetic control of the filamentary current flow during avalanche breakdown in a semiconductor at low temperatures represents an interesting new principle of a magnetic field-effect transistor. The power losses in such a device are minimized by using superconducting lines for the generation of the magnetic control field and for the interconnections. For such a hybrid concept, implementing semiconducting and superconducting components, the important performance characteristics are evaluated

1986-09-01

258

Study of the U-25B MHD generator system in strong electric and magnetic fields  

International Nuclear Information System (INIS)

The third and fourth tests of the U-25B facility have demonstrated that the MHD flow train has operated for over 50 h with little difficulty. Review of the data reveals no significant problems associated with vibration, stress, or fluctuation of the electrical and gasdynamic parameters of the system components. In Test 3, the MHD generator produced a maximum power of 575 kW, a maximum Hall voltage of 4240 V, and a maximum Hall field of 2100 V/m. Inverter loading characteristics indicated that the upstream portion of the channel operated at low conductivity compared to the two downstream sections. During Test 4, at a lower mass flow rate but with cesium seed and oxygen enrichment to 60%, a power level of about 400 kW was generated. Because of inadvertent water and air leakage into the combustion chamber, however, combustion temperatures were lower in Test 4 that anticipated. These factors had a detrimental effect on the generator performance. Analysis of the data obtained from Tests 3 and Test 4 illustrates that in order to increase the power of the U-25B channel, a number of steps should be taken to increase the effective plasma conductivity and channel mass flow. For example, increasing the mass flow rate to 5 kg/s and achieving a K/sub sigma/ of 0.7 to 0.8, a channel inlet temperature about 2950 K may produce an electrical power output up to 1.3 MW. Steps are being taken to increase the preheat temperature in the facility, as well as to eliminate all water and air leakage into the combustor and decrease other thermal losses in the combustor nozzle and generator

1979-06-20

259

Magnetic field induced third order susceptibility of third order harmonic generation in a ZnMgSe strained quantum well  

Science.gov (United States)

Third order susceptibility of third order harmonic generation is investigated in a Zn0.1Mg0.9Se/Zn0.8Mg0.2Se/Zn0.1Mg0.9Se quantum well in the presence of magnetic field strength. The confinement potential is considered as the addition of energy offsets of the conduction band (or valence band) and the strain-induced potential in our calculations. The material dependent effective mass is followed throughout the computation because it has a high influence on the electron energy levels in low dimensional semiconductor systems.

Mark, J. Abraham Hudson; Peter, A. John

2014-04-01

260

Temporal and spatial analysis of fields generated by eddy currents in superconducting magnets: Optimization of corrections and quantitative characterization of magnet/gradient systems  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We propose methods for the spatial and temporal characterization of time-dependent magnetic fields generated by eddy currents after switching gradients. For an on-line determination of the temporal variations of the fields, we extract two terms from the unresolved signal of an extended sample, describing the time evolution of a frequency shift ??B(z)(t) and of a decay constant k(t). This procedure allows us to optimize interactively the multiexponential pre-emphasis as well as any spectral ...

Boesch, C.; Gruetter, R.; Martin, E.

1991-01-01

 
 
 
 
261

The Earth's Magnetic Field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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...

Edda Lína Gunnarsdóttir 1988

2012-01-01

262

The earth's magnetic field  

International Nuclear Information System (INIS)

After a historical introduction in Chapter 1, the more traditional aspects of geomagnetism relating to the present field and historical observations are presented in Chapter 2. The various methods and techniques and theoretical background of palaeomagnetism are given in Chapter 3. Chapters 4, 5 and 6 present the results of palaeomagnetic and archaeomagnetic studies in three topics. Chapter 4 relates to studies of the geomagnetic field roughly back to about 50,000 years ago. Chapter 5 is about reversals of the geomagnetic field and Chapter 6 presents studies of the field for times older than 50,000 years and on the geological time scale of millions or hundreds of millions of years. Chapters 7, 8 and 9 provide insight into dynamo theory. Chapter 7 is essentially a non-mathematical attempt to explain the physical basis of dynamo theories to palaeomagnetists. This is followed in Chapter 8 by a more advanced theoretical treatment. Chapter 9 explains theoretical aspects of secular variation and the origin of reversals of the geomagnetic field. Chapter 10 is our attempt to relate theory to experiment and vice versa. The final two chapters consider the magnetic fields of the moon, sun, planets and meteorites, in an attempt to determine the necessary and sufficient conditions for magnetic field generation in large solar system bodies. (author)

1983-01-01

263

The Declining Magnetic Field  

Science.gov (United States)

This is an activity about the declining strength of Earth's magnetic field. Learners will review a graph of magnetic field intensity and calculate the amount by which the field has changed its intensity in the last century, the rate of change of its intensity, and when the field should decrease to zero strength at the current rate of change. Learners will also use evidence from relevant sources to create a conjecture on the effects on Earth of a vanished magnetic field. Access to information sources about Earth's magnetic field strength is needed for this activity. This is Activity 7 in the Exploring Magnetism on Earth teachers guide.

264

PHOTODETACHMENT IN MAGNETIC FIELDS  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The behavior of the photodetachment cross section, near threshold, for atomic negative ions in a magnetic field is described and illustrated with data on photodetachment of electrons from negative sulfur ions. The effect of the final state interaction is discussed and the photodetachment of atomic negative ions in a magnetic field is compared to photoionization of neutral atoms in a magnetic field. New data on the photodetachment cross section of a molecular negative ion, SeH-, in a magnetic ...

1982-01-01

265

Effect of the background magnetic field inhomogeneity on generation processes of whistler-mode chorus and broadband hiss-like emissions  

Science.gov (United States)

By a series of self-consistent electron hybrid code simulations, we study the effect of the background magnetic field inhomogeneity on the generation process of whistler-mode chorus emissions. Chorus with rising tones are generated through nonlinear wave-particle interactions occurring around the magnetic equator. The mirror force plays an important role in the nonlinear interactions, and the spatial inhomogeneity of the background magnetic field is a key parameter of the chorus generation process. We have conducted numerical experiments with different spatial inhomogeneities to understand properties of the chorus generation process. We assume the same initial condition of energetic electrons at the magnetic equator in all simulation runs. The simulation results reveal that the spectral characteristics of chorus significantly vary depending on the magnetic field inhomogeneity. Whistler-mode emissions are generated and propagate away from the equator in all simulation runs, but distinct chorus elements with rising tones are only reproduced in the cases of small inhomogeneities. In the simulation that had the smallest inhomogeneity, we find excitation of broadband hiss-like emission (BHE) whose amplitudes are comparable to discrete chorus elements found in other simulation runs. The BHE consists of many wave elements with rising tones nonlinearly triggered in the region close to the magnetic equator. We show that the small spatial inhomogeneity of the background magnetic field results in the small threshold amplitude for the nonlinear wave growth and allows the triggering process of rising tone elements to emerge easily in the equatorial region of the magnetosphere.

Katoh, Yuto; Omura, Yoshiharu

2013-07-01

266

Generation of magnetic field by the current-driven instability near cosmic-ray modified shocks  

International Nuclear Information System (INIS)

We study the non-linear properties of the current-driven instability predicted by Bell (2004). In the first part, we combine an analytical modeling plus particle-in-cell (PIC) simulations to make a one-dimensional study of the waves as they were isolated plane waves subject to a constant cosmic ray (CR) current. In the second part, we relax these conditions by including multidimensional effects and also the back-reaction on the CRs. In the idealistic case, we find that the current-driven waves can grow exponentially until the Alfven velocity of the plasma, Va, becomes comparable to the drift velocity of the CRs, Vcr. We also find that, in the exponential growth regime, the current-driven waves will move the plasma along the direction of propagation of the CRs at a speed ?Va2/Vcr. Also, they will induce transversal plasma motions of about the '' transversal Alfven speed '', which is the Alfven speed calculated only with the fields perpendicular to the CR current. The multidimensional evolution of the instability is studied making use of two- and three-dimensional simulations. First, we find that a condition for the growth of the instability is that Vcr(Ncr/Ni) << Vai, where Ncr and Ni are the density of CR and background ions, respectively, and Vai is the initial Alfven velocity of the plasma. If this condition is not met, the instability will be suppressed by the formation of strong plasma filaments of the scale of the ions skin depth. We also find that, even if the current-driven waves can grow, they will produce significant density fluctuations in the plasma shortly after they become non-linear, which confirm previous numerical MHD studies. The formation of these fluctuations will decrease the growth rate of the instability and will enlarge its dominant wavelengths. We also study the effect of the back-reaction on CR. We find that, if the Larmor radii of the CR become comparable to the size of the magnetic fluctuations, the deflection of the CR can saturate the instability before the regime Va ? Vcr is reached. We discuss applications of this instability to both relativistic and non-relativistic shock environments. (author)

2008-10-05

267

Simulation Outside Magnetic Field of the Sun  

Directory of Open Access Journals (Sweden)

Full Text Available We derive the viscous current in the fully ionized two-fluid plasma to generate the solar magnetic field. The global magnetic field of the Sun can be simulated by the viscous current from the differential rotation inside the Sun. The field presents a structure with 6-polar. As the viscous current is very weak, the magnetic field intensity is only about G, which could be considered as the background field of the Sun. The theory is a start for the generation of solar magnetic field. The local strong magnetic field of the Sun is not considered in the paper.

Zhiliang Yang

2011-06-01

268

Magnetic field measuring device  

International Nuclear Information System (INIS)

A coil is disposed to a beam secured at one end thereof for measuring magnetic fields at peripheries of reactor core plasmas. Electric current is supplied to the coil to cause electromagnetic force in magnetic fields to be measured, and the deformation amount of the beam is measured to determine low frequency components of the magnetic fields. High frequency components of the magnetic fields are measured based on output signals of a pick-up coil, and the two magnetic field components are synthesized to form one magnetic signal. Namely, the electromagnetic force acts as a bending moment of the beam, the beam is deformed, and the deformation amount is in proportion to the bending moment. Therefore, if a resistance wire is disposed to one end of the beam so that the resistance wire shrinks by the deformation of the beam and the resistance value is changed, the magnetic field can be determined based on the changing amount of the resistance value. Since magnetic fields free from a drift ingredient of an integrator can be measured, magnetic fields can be measured for a long period of time at a predetermined accuracy, and since a semiconductor sensor is not used, magnetic fields having excellent radiation resistance can be provided. (N.H.)

1996-06-17

269

Magnetic Field Example 1  

Science.gov (United States)

Clicking on the different links below will produce different magnetic fields in the box above. The wires (perpendicular to the screen) or coils (in and out of the screen) are not visible, but you can determine what they are from the field. You can also click on a point to read off the magnetic field at that place.

Christian, Wolfgang; Belloni, Mario

2008-02-19

270

High-bit-rate generation of low chirped pulses from vertical-cavity surface-emitting lasers via external axial magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The possibility of generating low chirped, fast optical pulses with linear polarization in vertical-cavity surface-emitting lasers (VCSEL's) is numerically explored. We show that, under the influence of an axial magnetic field, polarization modulation at gigahertz rates can be achieved with possible applications in optical clock generation/extraction and optical communications.

1998-01-01

271

Density profile steepening due to self-generated magnetic fields in plasmas produced by laser irradiation of spherical targets  

International Nuclear Information System (INIS)

The density variation of plasmas produced by irradiation with laser beams on spherical targets has been studied in the steady state. This study used an adiabatic plasma model with self-generated magnetic fields included in a phenomenological manner. The density variation with a radial coordinate is found to have a steep rise through the critical density, which reaches a plateau in the overdense region, then a density minimum and finally, a rise. This variation has been compared with experimentally observed values in earlier works and is found to be in fairly good agreement. The variation of plateau density with the intensity of the laser is also compared with the experimentally observed variation. copyright 1995 American Institute of Physics

1995-07-01

272

Macro-scale matter wave generation in charged particle dynamics in a magnetic field, a consequence of quantum entanglement  

International Nuclear Information System (INIS)

Matter wave interference effects on the macro-scale predicted by the author in charged particle dynamics in a magnetic field [R.K. Varma, Phys. Rev. E 64, 036608 (2001)], and observed subsequently [R.K. Varma, A.M. Punithavelu, S.B. Banerjee, Phys. Rev. E 65, 026503 (2002); R.K. Varma, S.B. Banerjee, Phys. Scr. 75, 19 (2007)] have been shown here to be an interesting consequence of quantum entanglement between the parallel and perpendicular degrees of freedom of the particle. Treating the problem in the framework of the inelastic scattering theory, it is shown that these macro-scale matter waves are generated in the 'parallel' degree of freedom as a modulation of the plane wave state of the particle along the field concomitantly with the excitation of Landau levels in the perpendicular degree of freedom in an inelastic scattering episode. We highlight here the role of quantum entanglement leading to the generation of this macro-scale quantum entity which has been shown to exhibit observable consequences. This case also exemplifies a situation exhibiting quantum entanglement on the macro-scale. (author)

2012-02-01

273

Low-frequency plasma instability generated in the sheath region of a biased rod-electrode immersed along the magnetic field line in a weakly magnetized plasma  

International Nuclear Information System (INIS)

The characteristics of a low-frequency, electrostatic plasma instability generated in the sheath region of a biased, thin rod-electrode are experimentally investigated in detail in a weakly ionized, weakly magnetized (that is, electrons are magnetized, while ions are not magnetized) cylindrical plasma. (author). 2 refs, 5 figs

1994-11-04

274

Generation of Kilogauss radial magnetic fields in the plasma focus current sheath  

International Nuclear Information System (INIS)

The purpose of this chapter is to present a mechanism which can explain the origin and main features of current sheath (CS) filamentation, and which is able to correlate several experimental facts. Investigates the possibility of thermoelectric instability as being the origin of the filamentary structure observed in the current sheath of a plasma focus device. Concludes that the outlined theory indicates that a clean, warm, well ionized plasma is best suited for the production of the dissipative, filamentary magnetic structures which recent experiments disclose as a desirable and key feature of PF machines

1975-12-03

275

Effect Of The LEBT Solenoid Magnetic Field On The Beam Generation For Particle Tracking  

CERN Document Server

Linac4 is a 160 MeV H- linear accelerator which will replace the 50 MeV proton Linac2 for upgrade of the LHC injectors with higher intensity and eventually an increase of the LHC luminosity. Linac4 structure is a source, a 45 keV low energy beam transport line (LEBT) with two solenoids, a 3 MeV Radiofrequency Quadrupole (RFQ), a Medium Energy Beam Transport line (MEBT), a 50 Mev DTL, a 100 Mev CCDTL and PIMS up to 160 Mev. We use Travel v4.07 and PathManager code for simulation. Firstly, we need to a file as a source and defining the beginning point (last point in tracking back) of simulation. We recognise the starting point base on the solenoid magnetic property of LEBT.

Yarmohammadi Satri, M; CERN. Geneva. ATS Department

2013-01-01

276

Magnetic Field Measurements in Beam Guiding Magnets  

CERN Document Server

Electromagnets used as beam guiding elements in particle accelerators and colliders require very tight tole-rances on their magnetic fields and on their alignment along the particle path. This article describes the methods and equipment used for magnetic measurements in beam transport magnets. Descriptions are given of magnetic resonance techniques, various induction coil methods, Hall generator measurements, the fluxgate magnetometer as well as the recently developed method of beam based alignment. References of historical nature as well as citations of recent work are given. The present commercial availability of the different sensors and asso-ciated equipment is indicated. Finally we shall try to analyze possible future needs for developments in those fields.

Henrichsen, K N

1998-01-01

277

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)

2012-01-01

278

N-flationary magnetic fields  

CERN Multimedia

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.

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

2007-01-01

279

The Earth's Magnetic Field  

Science.gov (United States)

The magnetic field of the Earth is contained in a region called the magnetosphere. The magnetosphere prevents most of the particles from the sun, carried in solar wind, from hitting the Earth. This site, produced by the University Corporation for Atmospheric Research (UCAR), uses text, scientific illustrations,and remote imagery to explain the occurrence and nature of planetary magnetic fields and magnetospheres, how these fields interact with the solar wind to produce phenomena like auroras, and how magnetic fields of the earth and other planets can be detected and measured by satellite-borne magnetometers.

280

Field free line magnetic particle imaging  

CERN Document Server

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

Erbe, Marlitt

2014-01-01

 
 
 
 
281

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

CERN Document Server

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 collisionless magnetic reconnection. Particle-in-cell simulations reveal that most of the magnetic energy is released and most of this energy goes into energetic ions with significant but smaller amounts of energy going into electrons. The energy gain of the most energetic ions results from their reflection from the ends of contracting magnetic islands, a first order Fermi process. The energy gain of the ions in contracting islands increases their parallel (to the magnetic field ${\\bf B}$) pressure $p_\\parallel$ until the marginal firehose condi...

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

2009-01-01

282

Design and Modelling of a Silicon Optical MEMS Switch Controlled by Magnetic Field Generated by a Plain Coil  

Science.gov (United States)

Optical switches can be made as a silicon cantilever with a magnetic layer. Such a structure is placed in a magnetic field of a planar coil. There is a torque deflecting the silicon beam with NiFe layer depending on a flux density of the magnetic field. The study shows an analysis of ferromagnetic layer parameters, beam's dimensions on optical switch characteristics. Different constructions of the beams were simulated for a range of values of magnetic field strength from 100 to 1000 A/m. An influence of the actuators parameters on characteristics was analysed. The loss of stiffness of the beam caused by specific constructions effected in displacements reaching 85 nm. Comsol Multiphysics 4.3b was used for the simulations.

Golebiowski, J.; Milcarz, Sz

2014-04-01

283

Magnetic fields at Neptune  

International Nuclear Information System (INIS)

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

1989-12-15

284

Mapping Magnetic Field Lines  

Science.gov (United States)

This is an activity about electromagnetism. Learners will use a compass to map the magnetic field lines surrounding a coil of wire that is connected to a battery. This activity requires a large coil or spool of wire, a source of electricity such as 3 D-cell batteries or an AC to DC power adapter, alligator-clipped wire, and magnetic compasses. This is the third lesson in the second session of the Exploring Magnetism teachers guide.

285

Wakefield generation in magnetized plasmas.  

Science.gov (United States)

We consider wakefield generation in plasmas by electromagnetic pulses propagating perpendicular to a strong magnetic field, in the regime where the electron cyclotron frequency is equal to or larger than the plasma frequency. Particle-in-cell simulations reveal that for moderate magnetic field strengths previous results are reproduced, and the wakefield wave number spectrum has a clear peak at the inverse skin depth. However, when the cyclotron frequency is significantly larger than the plasma frequency, the wakefield spectrum becomes broadband, and simultaneously the loss rate of the driving pulse is much enhanced. A set of equations for the scalar and vector potentials reproducing these results are derived, using only the assumption of a weakly nonlinear interaction. PMID:22060515

Holkundkar, Amol; Brodin, Gert; Marklund, Mattias

2011-09-01

286

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

1980-01-01

287

The Heliospheric Magnetic Field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 ...

2013-01-01

288

Influence of the back-reaction of streaming cosmic rays on magnetic field generation and thermal instability  

CERN Document Server

Using a multi-fluid approach, we investigate streaming and thermal instabilities of the electron-ion plasma with homogeneous cold cosmic rays propagating perpendicular to the background magnetic field. Perturbations are considered to be also across the magnetic field. The back-reaction of cosmic rays resulting in strong streaming instabilities is taken into account. It is shown that for sufficiently short wavelength perturbations, the growth rates can exceed the growth rate of cosmic-ray streaming instability along the magnetic field found by Nekrasov & Shadmehri (2012), which is in its turn considerably larger than the growth rate of the Bell instability (2004). The thermal instability is shown not to be subject to the action of cosmic rays in the model under consideration. The dispersion relation for the thermal instability has been derived which includes sound velocities of plasma and cosmic rays, Alfv\\'{e}n and cosmic-ray streaming velocities. The relation between these parameters determines the kind ...

Nekrasov, Anatoly K

2014-01-01

289

Linear magnetic motor/generator  

Science.gov (United States)

A linear magnetic motor/generator is disclosed which uses magnetic flux to provide mechanical motion or electrical energy. The linear magnetic motor/generator includes an axially movable actuator mechanism. A permament magnet mechanism defines a first magnetic flux path which passes through a first end portion of the actuator mechanism. Another permament magnet mechanism defines a second magnetic flux path which passes through a second end portion of the actuator mechanism. A drive coil defines a third magnetic flux path passing through a third central portion of the actuator mechanism. A drive coil selectively adds magnetic flux to and subtracts magnetic flux from magnetic flux flowing in the first and second magnetic flux path.

Studer, P. A.

1982-02-01

290

Passive Magnetic Shielding in Gradient Fields  

CERN Multimedia

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...

Bidinosti, C P

2013-01-01

291

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

CERN Document Server

(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)...

Modica, Frank; Zhiglo, Andrey

2013-01-01

292

Energy transfer and magnetic field generation via ion-beam driven instabilities in an electron-ion plasma  

International Nuclear Information System (INIS)

Whether an efficient collisionless temperature equilibration mechanism exists for a two-temperature ion-electron plasma, with Ti>Te, is important for understanding astrophysical phenomena such as two-temperature accretion flows and collisionless shocks in supernova remnants or gamma-ray bursts. In this paper, counter-streaming ion beam-driven two-stream, Weibel (or filamentation), and oblique instabilities are studied using two-dimensional (2D) particle-in-cell (PIC) simulations as a possible plasma instability that could operate in such astrophysical objects. The PIC simulations show interplay among these instabilities and that distinct stages with different dominant modes occur during the nonlinear evolution period. Although the 2D results show stronger electron-ion coupling than the one-dimensional (1D) instabilities, it is still too weak to rule out existing two-temperature accretion solutions. The nonrelativistic quasilinear equations for the 1D Weibel plus 1D two-stream modes are numerically solved to compare the results with the 2D PIC simulations and qualitative similarities were found. The equations also show that the magnetic fields generated by the Weibel instability decay to zero in the end.

2010-02-01

293

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

Directory of Open Access Journals (Sweden)

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].

Imbert-Gérard Lise-Marie

2011-11-01

294

To picosecond magnetic fields (abstract)  

Energy Technology Data Exchange (ETDEWEB)

The magnetic reversal mechanism in perpendicularly oriented, premagnetized Co based thin film alloys, induced by ultra short magnetic field exposure of a few picoseconds duration has been studied. Field pulses with a magnitude of several thousand Tesla were generated by the 50 GeV final focus electron beam at the Stanford Linear Accelerator Center (SLAC). Characteristic remanent domain patterns are observed in these films long after field exposure using polar Kerr microscopy. Complete reversal of the magnetization is found to occur during a single spin precession event of 6.0 ps duration where the inplane-field amplitude is greater or equal to the macroscopically determined perpendicular anisotropy field. Further, a wide transition range, dividing the reversed and nonreversed regions is observed which is broken into a quasi periodic stripe domain structure with stripe-width 0.3 {mu}m. As a main result of this experimental study we find that magnetization reversal on this time scale is solely governed by the intrinsic effective field, i.e., anisotropy- and demagnetization-field contributions, rather then by complex curling and buckling mechanisms. Unique insight into fundamental spin reversal mechanisms and their ultimate speed in thin magnetic recording films is provided by these experiments. {copyright} {ital 1996 American Institute of Physics.}

Heidmann, J. [IBM Storage Systems Division, 5600 Cottle Road, San Jose, California 95193 (United States); Weller, D. [IBM Research Division, Almaden Research Center, 650 Harry Road, San Jose, California 95120 (United States); Siegmann, H.C. [Swiss Federal Institute of Technology, Zurich (Switzerland); Garwin, E.L. [Stanford Linear Accelerator Center, Stanford University, Stanford, California 94309 (United States)

1996-04-01

295

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

Energy Technology Data Exchange (ETDEWEB)

We present herein 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 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. Our 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 field problems in cases of special and ideal geometries, the solutions of these and similar problems for the proper analysis and design of compressed magnetic field generators and their related hardware require computer simulations. In earlier studies, computer models have been proposed, several based on research oriented hydrocodes to which uncoupled or partially coupled Maxwell's equations solvers are added. Although the hydrocode models address the problem of moving, deformable conductors, they are not useful for electromagnetic analysis, nor can they be considered design tools. For our studies, we take advantage of the commercial, electromagnetic computer-aided design software packages FLUX2D nd PHI3D that were developed for motor manufacturers and utilities industries. 4 refs., 6 figs.

Hodgdon, M.L.; Oona, H.; Martinez, A.R.; Salon, S.; Wendling, P.; Krahenbuhl, L.; Nicolas, A.; Nicolas, L.

1989-01-01

296

On Primordial Magnetic Fields of Electroweak Origin  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We consider Vachaspati's primordial magnetic field which is generated at the electroweak phase transition. Assuming that either the gradients of the Higgs field or, alternatively, the magnetic field itself are stochastic variables with a normal distribution, we find that the resulting magnetic field has an {\\em rms} value in the present-day universe which is fully consistent with what is required for the galactic dynamo mechanism.

Enqvist, K.; Olesen, P.

1993-01-01

297

Three-dimensional effects generated in a finite-length container under the action of a rotating magnetic field  

Energy Technology Data Exchange (ETDEWEB)

In the noninductive approximation (omega-bar<1) we consider a three-dimensional axisymmetric stationary flow of a conducting liquid, excited in a cylindrical container of finite length by a rotating magnetic field of arbitrary symmetry, homogeneous along the z axis.

Kapusta, A.B.; Zibold' d, A.F.

1982-10-01

298

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.)

1991-02-04

299

The effect of applied magnetic field on photocurrent generation in poly-3-hexylthiophene:[6,6]-phenyl C61-butyric acid methyl ester photovoltaic devices  

International Nuclear Information System (INIS)

The effect of a magnetic field on the photocurrent generated by a bulk heterojunction solar cell made from poly-3-hexylthiophene (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) is investigated. At the operating voltage, increases in photocurrent of ?9% can be obtained at magnetic fields of less than 100 mT. This increase in photocurrent is attributed to an increase in the rate of intersystem crossing, between the singlet and triplet states, leading to a higher net efficiency of exciton dissociation. Close to the open-circuit voltage, an increase of more than two orders of magnitude in the photocurrent could be obtained under applied magnetic field. (fast track communication)

2008-11-12

300

Superconducting film magnetization in weak magnetic fields  

International Nuclear Information System (INIS)

A study is made on dependences of M magnetization on H magnetic field intensity (H2Cu3O7-? films in magnetic field, perpendicular to film plane. Correlation of hysteresis curves of film and massive sample magnetization was conducted. It is shown that M(H) dependences of films differ sufficiently from corresponding curves of massive samples

1990-01-01

 
 
 
 
301

Damping of cosmic magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

We examine the evolution of magnetic fields in an expanding fluid composed of matter and radiation with particular interest in the evolution of cosmic magnetic fields. We derive the propagation velocities and damping rates for relativistic and non-relativistic fast and slow magnetosonic and Alfv{acute e}n waves in the presence of viscous and heat conducting processes. The analysis covers all magnetohydrodynamics modes in the radiation diffusion and the free-streaming regimes. When our results are applied to the evolution of magnetic fields in the early universe, we find that cosmic magnetic fields are damped from prior to the epoch of neutrino decoupling up to recombination. Similar to the case of sound waves propagating in a demagnetized plasma, fast magnetosonic waves are damped by radiation diffusion on all scales smaller than the radiation diffusion length. The characteristic damping scales are the horizon scale at neutrino decoupling (M{sub {nu}}{approx}10{sup {minus}4}M{sub {circle_dot}} in baryons) and the Silk mass at recombination (M{sub {gamma}}{approx}10{sup 13}M{sub {circle_dot}} in baryons). In contrast, the oscillations of slow magnetosonic and Alfv{acute e}n waves get overdamped in the radiation diffusion regime, resulting in frozen-in magnetic field perturbations. Further damping of these perturbations is possible only if before recombination the wave enters a regime in which radiation free-streams on the scale of the perturbation. The maximum damping scale of slow magnetosonic and Alfv{acute e}n modes is always smaller than or equal to the damping scale of fast magnetosonic waves, and depends on the magnetic field strength and its direction relative to the wave vector. Our findings have multifold implications for cosmology. The dissipation of magnetic field energy into heat during the epoch of neutrino decoupling ensures that most magnetic field configurations generated in the very early universe satisfy big bang nucleosynthesis constraints. Further dissipation before recombination constrains models in which primordial magnetic fields give rise to galactic magnetic fields or density perturbations. Finally, the survival of Alfv{acute e}n and slow magnetosonic modes on scales well below the Silk mass may be of significance for the formation of structure on small scales. {copyright} {ital 1998} {ital The American Physical Society}

Jedamzik, K. [Max-Planck-Institut fuer Astrophysik, 85748 Garching bei Muenchen (Germany); Katalinic, V.; Olinto, A.V. [Department of Astronomy and Astrophysics and Enrico Fermi Institute, University of Chicago, 5640 S. Ellis Ave., Chicago, Illinois 60637 (United States)

1998-03-01

302

ISR Radial Field Magnet  

CERN Multimedia

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

1983-01-01

303

Trapped field internal dipole superconducting motor generator  

Energy Technology Data Exchange (ETDEWEB)

A motor generator including a high temperature superconductor rotor and an internally disposed coil assembly. The motor generator superconductor rotor is constructed of a plurality of superconductor elements magnetized to produce a dipole field. The coil assembly can be either a conventional conductor or a high temperature superconductor. The superconductor rotor elements include a magnetization direction and c-axis for the crystals of the elements and which is oriented along the magnetization direction.

Hull, John R. (Downers Grove, IL)

2001-01-01

304

Cosmic magnetic fields  

CERN Multimedia

Magnetic fields are important in the Universe and their effects contain the key to many astrophysical phenomena that are otherwise impossible to understand. This book presents an up-to-date overview of this fast-growing topic and its interconnections to plasma processes, astroparticle physics, high energy astrophysics, and cosmic evolution. The phenomenology and impact of magnetic fields are described in diverse astrophysical contexts within the Universe, from galaxies to the filaments and voids of the intergalactic medium, and out to the largest redshifts. The presentation of mathematical formulae is accessible and is designed to add insight into the broad range of topics discussed. Written for graduate students and researchers in astrophysics and related disciplines, this volume will inspire readers to devise new ways of thinking about magnetic fields in space on galaxy scales and beyond.

Kronberg, Philipp P

2013-01-01

305

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.

2010-06-01

306

Generation mechanism of slow-time-scale magnetic fields and electron acceleration by the field in an underdense relativistic Vlasov plasma  

International Nuclear Information System (INIS)

Slow-time-scale magnetic fields driven by fast-time-scale electromagnetic waves or plasma waves are unitarily discussed in a relativistic Vlasov plasma. Such a field is a result of the difference beat of wave-wave, which drives a solenoidal current, and the interaction of wave-particle. The magnitude of the slow-time-scale magnetic field proposed here can be as high as about 20 MS on the critical surface for the laser intensity I = 1018 W/cm2 at laser wavelength ? = 1.06?m. (authors)

1999-09-12

307

Observations of Cool-Star Magnetic Fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Cool stars like the Sun harbor convection zones capable of producing substantial surface magnetic fields leading to stellar magnetic activity. The influence of stellar parameters like rotation, radius, and age on cool-star magnetism, and the importance of the shear layer between a radiative core and the convective envelope for the generation of magnetic fields are keys for our understanding of low-mass stellar dynamos, the solar dynamo, and also for other large-scale and planetary dynamos. Ou...

2012-01-01

308

Emission of magnetic fields from distribution lines  

International Nuclear Information System (INIS)

Ontario Hydro performed a study of emission of magnetic fields from distribution lines. Comprehensive calculations were performed to evaluate magnetic fields by varying standard pole framings, voltages, typical currents, very high currents near transformers and distribution stations, perfectly balanced, and 10% unbalanced lines. All tests computed magnetic flux under the distribution line at 1 m exposure above ground. The magnetic fields measured ranged from 1.2-22 ?Tesla. These values relate very closely to magnetic fields generated by household appliances. The most effective reduction of magnetic fields occurs when the following conditions are met: reverse phasing arrangement on double-phase lines; transportation of 3-phase lines; replacement of crossarm pole framing with armless pole framing; conversion of single phase to 3-phase lines; and balancing lines as best as possible. Field strengths are compared to those found with naturally occurring magnetic fields, household appliances, transportation, security systems, industrial processes, and medical practices. 2 refs., 1 fig., 5 tabs

1988-01-01

309

Generation of a small-scale quasi-static magnetic field and fast particles during the collision of electron-positron plasma clouds  

DEFF Research Database (Denmark)

We present the results of analytical studies and 2D3V PIC simulations of electron-positron plasma cloud collisions. We concentrate on the problem of quasi-static magnetic field generation. It is shown from linear theory, using relativistic two-fluid equations for electron-positron plasmas, that the generation of a quasi-static magnetic field can be associated with the counterstreaming instability. A two-dimensional relativistic particle simulation provides good agreement with the above linear theory and shows that, in the nonlinear stage of the instability, about 5.3% of the initial plasma flow energy can be converted into magnetic field energy. It is also shown from the simulation that the quasi-static magnetic field undergoes a collisionless change of structure, leading to large-scale, long-living structures and the production of high-energy particles. These processes may be important for understanding the production of high-energy particles in the region where two pulsar winds collide.

Kazimura, Y.; Sakai, J. I.

1998-01-01

310

Chiral near fields generated from plasmonic lattices  

CERN Document Server

Plasmonic fields are usually considered non-chiral because of the transverse magnetic polarization of surface plasmon modes. We however show here that plasmonic lattices built from coherent superpositions of surface plasmons can generate optical chirality in the interfering near field. We reveal in particular the emergence of plasmonic potentials relevant to the generation of near-field chiral forces. This draws promising perspectives for performing enantiomeric separation schemes within the near field.

Canaguier-Durand, Antoine

2014-01-01

311

Nuclear magnetic resonance and earth magnetic field  

International Nuclear Information System (INIS)

Nuclear magnetic resonance concerns nuclei whose spin is different from 0. These nuclei exposed to a magnetic field is comparable to a peg top spinning around its axis while being moved by a precession movement called Larmor precession. This article presents an experiment whose aim is to reveal nuclear magnetism of nuclei by observing Larmor precession phenomena due to the earth magnetic field. The earth magnetic field being too weak, it is necessary to increase the magnetization of the sample during a polarization phase. First the sample is submitted to a magnetic field B perpendicular to the earth magnetic field B0, then B is cut off and the nuclei move back to their equilibrium position by executing a precession movement due to B0 field. (A.C.)

1998-03-01

312

Noncommutativity in space and primordial magnetic field  

International Nuclear Information System (INIS)

In this paper we show that noncommutativity in spatial coordinates can generate magnetic field in the early Universe on a horizon scale. The strength of such a magnetic field depends on tin number density of massive charged particles present at a given moment. This allows us to trace back the temperature dependence of the noncommutativity scale from the bounds on primordial magnetic field coming from nucleosynthesis. (author)

2001-01-01

313

High field superconducting magnets  

Science.gov (United States)

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.

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

2011-01-01

314

Optimum Magnets for MHD Generators  

International Nuclear Information System (INIS)

One of the more critical aspects in the design of MHD power generation systems for specific applications concerns the proper selection of a magnet for the generator. The advent of superconducting (low weight, zero power) magnets will allow of the realization of MHD systems which are competitive with conventional power generators. Nevertheless, resistive or permanent magnets may prove superior to superconducting magnets for certain types of MHD generation systems. The purpose of this study is to define the areas of applicability for permanent, conventionally cooled resistive, cryogenically cooled resistive, and superconducting magnets to open cycle MHD power generation systems. Combustion driven MHD generators utilizing continuous electrode Faraday and Hall configurations are investigated. In all cases, typical values of gas scalar conductivity, gas velocity, and Hall coefficient are used. Operation of such generators is considered over the range of net power output 100 kW to 1000 MW for durations of 1 ms to one year. For each generator case considered, magnet characteristics are calculated for systems optimized on the basis of either total system cost or total system weight by computer analysis. Magnets and refrigerator systems are assumed to be operated with power generated by the MHD process. The cost, weight, and power requirements of magnet cooling systems are calculated and included in the magnet design criteria. The net power produced by the generator must be computed taking into consideration the proper efficiency factors and losses represented by Joule heating in the resistive magnets and refrigeration losses in superconducting magnets. Coolant tankage weights are also considered for aerospace systems. The type or types of magnets most applicable to the given operating situation for the two types of generators are then selected. The selection of magnet types for stationary and mobile systems as well as for short and long duration systems is made. The results of the investigation are presented in summary form for two types of MHD generators. These results are plotted on power duration and net power output co-ordinates to show the economical operating regimes of the various types of magnets. Both a weight and cost optimum regime are shown for the entire MHD generator operating range. The most significant result of the analysis is that high-purity aluminium magnets cooled with liquid hydrogen exhibit a wide range of application from both a cost and weight standpoint. (author)

1966-12-01

315

Field-free line formation in a magnetic field  

International Nuclear Information System (INIS)

In this communication, the theory of field-free line (FFL) formation in a magnetic field is investigated. It is shown that an FFL can be generated by only three Maxwell coil pairs. By varying the applied currents, the FFL can be arbitrarily rotated, while keeping the coils static in space. For translation, additional Helmholtz coil pairs can be used. These findings enable efficient realization of a field generating unit for a recently developed imaging method named magnetic particle imaging. (fast track communication)

2010-01-08

316

Three-module disk explosive magnetic generator  

International Nuclear Information System (INIS)

Ultrahigh pulse current and magnetic field generation in the volumes meeting the experimental requirements, is closely connected with the necessity of the fundamental scientific and technical problem solution. This paper reports that the symmetric target implosion by an axial accelerating magnetic field to solve the problems of the controlled fusion based on the magnetogasdynamic energy cumulation requires the creation of energy-consuming (250 MJ in 5--10 ?s) accumulator of the electromagnetic energy

1989-07-03

317

High magnetic fields science and technology  

CERN Document Server

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

Miura, Noboru

2003-01-01

318

Nuclear Magnetic Resonance and Magnetic Field Measurements  

Science.gov (United States)

This laboratory is designed for students to become familiar with the principles and detection techniques of Nuclear Magnetic Resonance (NMR), examine the relationship between current and magnetic field in an electromagnet, and gain experience in the use of magnetic field measurement techniques.

2012-01-04

319

Lattice Planar QED in external magnetic field  

CERN Document Server

We investigate planar Quantum ElectroDynamics (QED) with two degenerate staggered fermions in an external magnetic field on the lattice. Our preliminary results indicate that in external magnetic fields there is dynamical generation of mass for two-dimensional massless Dirac fermions in the weak coupling region. We comment on possible implications to the quantum Hall effect in graphene.

Cea, Paolo; Giudice, Pietro; Papa, Alessandro

2011-01-01

320

Electrophysiological and quantitative electroencephalographic measurements after treatment by transcerebral magnetic fields generated by compact disc through a computer sound card: the Shakti treatment.  

Science.gov (United States)

Quantitative electroencephalographic activity over the left and right frontal, temporal, parietal, and occipital lobes was obtained on 4 successive weeks in 12 subjects before they were exposed cerebrally for 30 min to one of two configurations of weak complex magnetic fields or to a sham-field condition. The two configurations were Shakti (c Todd Murphy) and the set of 4 solenoids (Koren boxes) generating a burst-firing magnetic field through the temporal lobes. Compared to baseline measurements there were no statistically significant differences in treatments for relative changes in power over these regions within the delta, theta, low alpha, beta, or gamma ranges. However within the high alpha range (10.5 Hz to 13 Hz), there was a significant interaction between session and type of treatment that was due primarily to the Shakti treatment. These changes were congruent with the subjective experiences reported by some users of the technology. PMID:15527205

Tsang, E W; Koren, S A; Persinger, M A

2004-08-01

 
 
 
 
321

Magnetic fields and stellar evolution  

International Nuclear Information System (INIS)

The author reviews the present state of knowledge regarding magnetic fields and stellar evolution. Two explanations of stellar magnetic fields are discussed: contemporary dynamo action maintaining the magnetic field and, a slowly decaying relic of either the galactic field pervading the gas from which the star formed, or of dynamo action in an earlier epoch in the star's life. (Auth.)

1980-07-25

322

Galactic and Extragalactic Magnetic Fields  

CERN Document Server

The strength of the total magnetic field in our Milky Way from radio Zeeman and synchrotron measurements is about 6 muG near the Sun and several mG in dense clouds, pulsar wind nebulae, and filaments near the Galactic Center. Diffuse polarized radio emission and Faraday rotation of the polarized emission from pulsars and background sources show many small-scale magnetic features, but the overall field structure in our Galaxy is still under debate. -- Radio synchrotron observations of nearby galaxies reveal dynamically important magnetic fields of 10-30 muG total strength in the spiral arms. Fields with random orientations are concentrated in spiral arms, while ordered fields (observed in radio polarization) are strongest in interarm regions and follow the orientation of the adjacent gas spiral arms. Faraday rotation of the diffuse polarized radio emission from the disks of spiral galaxies sometimes reveals large-scale patterns which are signatures of coherent fields generated by dynamos, but in most galaxies ...

Beck, Rainer

2008-01-01

323

Distributed generation induction and permanent magnet generators  

CERN Document Server

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 generator (IG) is the most commonly used and cheapest 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 rel

Lai, Loi Lei

2008-01-01

324

Magnetic field optimization of permanent magnet undulators for arbitrary polarization  

Energy Technology Data Exchange (ETDEWEB)

Techniques for improving the magnetic field quality of APPLE II undulators are discussed. Individual block characterization including the inhomogeneities of the magnetization permits a precise prediction of field integrals as required for sorting. Specific shimming procedures adapted to the magnetic design of APPLE II undulators have to be employed in order to meet the stringent requirements of insertion devices in third generation synchrotron radiation sources as demonstrated for BESSY.

Bahrdt, J. E-mail: bahrdt@bessy.de; Frentrup, W.; Gaupp, A.; Scheer, M.; Englisch, U

2004-01-11

325

A Fiber Magnetic Field Sensor  

International Nuclear Information System (INIS)

A Fabry-Perot interferometer-based fiber optic sensor that uses magnetostrictive Terfenol-D (Tb0,3Dy0,7Fe1,92) rod as a sensor gauge for measuring DC magnetic fields was designed. A single mode fiber was placed in front of the one of the polished circular face of Terfenol-D rod with 48 mm long and 6 mm in diameter, acts as a reflector, thereby creating an air gap that acts as a Fabry-Perot cavity. A solenoid was used to generate magnetic field and the sensor was inserted inside the coil. The detectable minimum magnetic field level is 8 kA/m (?100 Oe). Up to 45 kA/m magnetic field was measured by using the sensor. Also the obtained results were compared with the theoretical results. A single mode diode laser was used as a light source with 660 nm wavelength and the data acquisition was made with ADC with a simple program written in Labview 8.0

2008-08-25

326

Magnetic Fields, Flares & Forecasts  

Science.gov (United States)

A 2D wavelet transform modulus maxima (WTMM) method is used to characterise the complexity of the distribution of the photospheric magnetic field of active regions. The WTMM method offers increased accuracy and reliability over previous fractal and multifractal methods. The multifractal spectrum of both quiet Sun and active region magnetic features are presented. It is shown that the multifractal nature of the quiet Sun is significantly different from that of an active region. As such, a method is proposed to seperate the information corresponding to the multifractal spectrum of an active region from the surrounding quite Sun texture. The WTMM method and segmentation procedure are shown to detect the internal restructuring of active region magnetic features prior to flaring. We detect two thresholds (Haussdorf dimension > 1.2 and Holder Exponent > -0.7) as possible indicators for conditions favourable to flaring.

Conlon, Paul A.; Kestener, P.; McAteer, R.; Gallagher, P.

2009-05-01

327

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

1994-09-01

328

Magnetic fields and cancer  

Energy Technology Data Exchange (ETDEWEB)

This letter is a response to an article by Savitz and Kaune, EHP 101:76-80. W-L wire code was applied to data from a 1988 Denver study, and an association was reported between high W-L wire code and childhood cancer. This author discusses several studies and provides explanations which weakens the argument that classification error resulted in an appreciable reduction in the association between W-L high wire code and childhood cancer. In conclusion, the fact that new wire code is only weakly correlated with magnetic field measurements (in the same manner as the original W-L wire code) suggests that the newly reported stronger association with childhood cancer is likely due to factors other than magnetic fields. Differential residential mobility and differential residential age are two possible explanations and are suggestive that the reported association may be false.

Jones, T.L.

1993-10-01

329

Electrostatic wave heating and possible formation of self-generated high electric fields in a magnetized plasma  

Energy Technology Data Exchange (ETDEWEB)

A plasma reactor operates at the Laboratori Nazionali del Sud of INFN, Catania, and it has been used as a test-bench for the investigation of innovative mechanisms of plasma ignition based on electrostatic waves (ES-W), obtained via the inner plasma EM-to-ES wave conversion. Evidences of Bernstein wave (BW) generation will be shown. The Langmuir probe measurements have revealed a strong increase of the ion saturation current, where the BW are generated or absorbed, this being a signature of possible high energy ion flows. The results are interpreted through the Bernstein wave heating theory, which predicts the formation of high speed rotating layers of the plasma (a dense plasma ring is in fact observed). High intensity inner plasma self-generated electric fields (on the order of several tens of kV/cm) come out by our calculations.

Mascali, D., E-mail: davidmascali@lns.infn.it [INFN - Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy); CSFNSM, Viale A. Doria 6, 95125 Catania (Italy); Celona, L.; Gammino, S. [INFN - Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy); Miracoli, R.; Castro, G.; Gambino, N. [INFN - Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy); Universita degli Studi di Catania, Dipartimento di Fisica e Astronomia, Via S. Sofia 64, 95123 Catania (Italy); Ciavola, G. [INFN - Laboratori Nazionali del Sud, via S. Sofia 62, 95123 Catania (Italy)

2011-10-11

330

Simulation of pulsed ELF magnetic fields generated by GSM mobile phone handsets for human electromagnetic bioeffects research.  

Science.gov (United States)

Human provocation studies that investigate the effects of Global System for Mobiles (GSM) communication systems on the brain have focused on Radio Frequency (RF) exposure. We wish to further extend such study by investigating the effect of both RF and Extremely Low Frequency (ELF) field exposure, the latter generated by the GSM handset's battery switching. The use of a commercial handset as an exposure source for such investigations is problematic for a number of reasons and therefore a simulated exposure source, capable of producing both RF and ELF components of exposure, is desirable. As a first step in developing such a source, we have quantified and characterized the ELF field from several commercial handsets (the RF characteristics being already well understood). Through experimental measurement we deduce that these fields can be sufficiently simulated by a 9 mm radius loop residing 10 mm beneath the front surface of the handset device and carrying enough current to generate peak fields of 25 microT at the surface of the handset. PMID:18946983

Perentos, N; Iskra, S; McKenzie, R J; Cosi, I

2008-09-01

331

A Linear Magnetic Motor/Generator.  

Science.gov (United States)

A linear magnetic motor/generator is described which uses magnetic flux to provide mechanical motion or electrical energy. The linear magnetic motor/generator includes an axially movable actuator mechanism. A permanent magnet mechanism defines a first mag...

P. A. Studer

1980-01-01

332

The Galactic Magnetic Field  

CERN Multimedia

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.

Jansson, Ronnie

2012-01-01

333

Magnetic Field Topology in Jets  

Science.gov (United States)

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.

Gardiner, T. A.; Frank, A.

2000-01-01

334

Low field magnetic resonance imaging  

Science.gov (United States)

A method and system of magnetic resonance imaging does not need a large homogenous field to truncate a gradient field. Spatial information is encoded into the spin magnetization by allowing the magnetization to evolve in a non-truncated gradient field and inducing a set of 180 degree rotations prior to signal acquisition.

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

2010-07-13

335

Field induced superconductivity in magnetically modulated films  

International Nuclear Information System (INIS)

The transport properties of Al superconducting thin films covering arrays of Co/Pt pinning centers of two different sizes are measured and compared. Detailed magnetization characterization of the dots allow us to gain control over the average magnetization of the dots through the application of an external magnetic field. By increasing the magnetization of the dots a gradually increasing shift of the superconducting phase boundary is observed. This shift is explained in terms of vortex-antivortex pair generation. It is shown that the resulting field-induced-superconductivity is strongly dependent on the size of the magnetic dots

2008-04-01

336

Heat generation ability in AC magnetic field of nano MgFe{sub 2}O{sub 4}-based ferrite powder prepared by bead milling  

Energy Technology Data Exchange (ETDEWEB)

Nanosized MgFe{sub 2}O{sub 4}-based ferrite powder having heat generation ability in an AC magnetic field was prepared by bead milling and studied for thermal coagulation therapy applications. The crystal size and the particle size significantly decreased by bead milling. The heat generation ability in an AC magnetic field improved with the milling time, i.e. a decrease in crystal size. However, the heat generation ability decreased for excessively milled samples with crystal sizes of less than 5.5 nm. The highest heat ability ({Delta}T=34 {sup o}C) in the AC magnetic field (370 kHz, 1.77 kA/m) was obtained for fine MgFe{sub 2}O{sub 4} powder having a ca. 6 nm crystal size (the samples were milled for 6-8 h using 0.1 mm {phi} beads). The heat generation of the samples was closely related to hysteresis loss, a B-H magnetic property. The reason for the high heat generation properties of the samples milled for 6-8 h using 0.1 mm {phi} beads was ascribed to the increase in hysteresis loss by the formation of a single domain. Moreover, the improvement in heating ability was obtained by calcination of the bead-milled sample at low temperature. In this case, the maximum heat generation ({Delta}T=41 {sup o}C) ability was obtained for a ca. 11 nm crystal size sample was prepared by crystal growth during the sample calcination. On the other hand, the {Delta}T value for Mg{sub 0.5}Ca{sub 0.5}Fe{sub 2}O{sub 4} was synthesized using a reverse precipitation method decreased by bead milling. - Research highlights: > The crystal and particle size for MgFe{sub 2}O{sub 4} based ferrite were decreased by bead milling. > The highest heat ability was obtained for MgFe{sub 2}O{sub 4} having a ca. 6 nm crystal size. > This high heat generation ability was ascribed to the increase in hysteresis loss. > Hysteresis loss was increased by the formation of a single domain.

Hirazawa, Hideyuki, E-mail: hirazawa@mat.niihama-nct.ac.j [Department of Environmental Materials Engineering, Niihama National College of Technology, Niihama 792-8580 (Japan); Aono, Hiromichi; Naohara, Takashi; Maehara, Tsunehiro [Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Sato, Mitsunori [AdMeTech Co. Ltd., 2821-4, Minami-yoshida-cyo, Matsuyama 791-8042 (Japan); Watanabe, Yuji [Department of Surgery, Graduate School of Medicine, Ehime University, Toon 791-0295 (Japan)

2011-03-15

337

Heat generation ability in AC magnetic field of nano MgFe2O4-based ferrite powder prepared by bead milling  

International Nuclear Information System (INIS)

Nanosized MgFe2O4-based ferrite powder having heat generation ability in an AC magnetic field was prepared by bead milling and studied for thermal coagulation therapy applications. The crystal size and the particle size significantly decreased by bead milling. The heat generation ability in an AC magnetic field improved with the milling time, i.e. a decrease in crystal size. However, the heat generation ability decreased for excessively milled samples with crystal sizes of less than 5.5 nm. The highest heat ability (?T=34 oC) in the AC magnetic field (370 kHz, 1.77 kA/m) was obtained for fine MgFe2O4 powder having a ca. 6 nm crystal size (the samples were milled for 6-8 h using 0.1 mm ? beads). The heat generation of the samples was closely related to hysteresis loss, a B-H magnetic property. The reason for the high heat generation properties of the samples milled for 6-8 h using 0.1 mm ? beads was ascribed to the increase in hysteresis loss by the formation of a single domain. Moreover, the improvement in heating ability was obtained by calcination of the bead-milled sample at low temperature. In this case, the maximum heat generation (?T=41 oC) ability was obtained for a ca. 11 nm crystal size sample was prepared by crystal growth during the sample calcination. On the other hand, the ?T value for Mg0.5Ca0.5Fe2O4 was synthesized using a reverse precipitation method decreased by bead milling. - Research Highlights: ?The crystal and particle size for MgFe2O4 based ferrite were decreased by bead milling. ?The highest heat ability was obtained for MgFe2O4 having a ca. 6 nm crystal size. ?This high heat generation ability was ascribed to the increase in hysteresis loss. ?Hysteresis loss was increased by the formation of a single domain.

2011-03-01

338

Magnetic Field Problem: Current and Magnets  

Science.gov (United States)

The above animations represent two typical bar magnets each with a North and South pole. The arrows represent the direction of the magnetic field. A wire is placed between the magnets and a current that comes out of the page can be turned on.

Christian, Wolfgang; Belloni, Mario

2007-03-03

339

Magnetic fields in galactic haloes  

CERN Document Server

Magnetic fields on a range of scales play a large role in the ecosystems of galaxies, both in the galactic disk and in the extended layers of gas away from the plane. Observing magnetic field strength, structure and orientation is complex, and necessarily indirect. Observational data of magnetic fields in the halo of the Milky Way are scarce, and non-conclusive about the large-scale structure of the field. In external galaxies, various large-scale configurations of magnetic fields are measured, but many uncertainties about exact configurations and their origin remain. There is a strong interaction between magnetic fields and other components in the interstellar medium such as ionized and neutral gas and cosmic rays. The energy densities of these components are comparable on large scales, indicating that magnetic fields are not passive tracers but that magnetic field feedback on the other interstellar medium components needs to be taken into account.

Haverkorn, Marijke

2011-01-01

340

The first magnetic fields in the universe  

CERN Multimedia

We show that the first structures that form in the universe should spontaneously generate magnetic fields. No primordial seed field is required for this "first dynamo". Although the first dynamo starts with kinetic plasma instabilities, we argue that an adequate magnetohydrodynamic description might be possible via a simple trick. This should allow a numerical study of the effect of the first magnetic fields on the first baryonic objects.

Gruzinov, Andrei

2009-01-01

 
 
 
 
341

Low Cost Magnetic Field Controller  

CERN Document Server

The Physics Institute of the University of São Paulo (IFUSP) is building a continuous wave (cw) racetrack microtron. This machine has several dipole magnets, like the first and second stage recirculators, and a number of smaller ones in the transport line. These magnets must produce very stable magnetic fields to allow the beam to recirculate along very precise orbits and paths. Furthermore, the fields must be reproducible with great accuracy to allow an easier setup of the machine, though the effects of hysteresis tend to jeopardize the reproducibility. If the magnetic field is chosen by setting the current in the coils, temperature effects over the magnet and power supply tend to change the field. This work describes an inexpensive magnetic field controller that allows a direct measure of the magnetic field through an Hall probe. It includes a microcontroller running a feedback algorithm to control the power supply, in order to keep the field stable and reproducible. The controller can also execu...

Malafronte, Alexandre A

2005-01-01

342

Poloidal magnetic field fluctuations  

International Nuclear Information System (INIS)

Elementary non-linear tearing-mode theory in a two-dimensional cylindrical geometry is used to predict accurately the amplitude of the m=2 poloidal-magnetic-field fluctuations (Mirnov oscillations) at the limiter of a tokamak. The input required is the electron temperature radial profile from which the safety factor profile can be inferred. The saturation amplitude of the m=2 tearing mode is calculated from the safety factor profile using a non-linear ?' analysis. This gives an absolute result (no arbitrary factors) for the amplitude of the perturbation in the poloidal magnetic field everywhere and, in particular, at the limiter. An analysis of ORMAK and T-4 safety factor profiles (inferred from electron temperature profiles) gives results that are in agreement with the experimental data. - A study of a general profile shows that, as a function of the safety factor at the limiter, a maximum occurs in the amplitude of the Mirnov oscillation. The magnitude of the maximum increases with a decrease in temperature near the limiter. (author)

1979-01-01

343

The Heliospheric Magnetic Field  

Directory of Open Access Journals (Sweden)

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.

Mathew J. Owens

2013-11-01

344

SCUPOL Magnetic Field Analysis  

CERN Document Server

We present an extensive analysis of the 850 microns polarization maps of the SCUPOL Catalog produced by Matthews et al. (2009), focusing exclusively on the molecular clouds and star-forming regions. For the sufficiently sampled regions, we characterize the depolarization properties and the turbulent-to-mean magnetic field ratio of each region. Similar sets of parameters are calculated from 2D synthetic maps of dust emission polarization produced with 3D MHD numerical simulations scaled to the S106, OMC-2/3, W49 and DR21 molecular clouds polarization maps. For these specific regions the turbulent MHD regimes retrieved from the simulations, as described by the turbulent Alfv\\`en and sonic Mach numbers, are consistent within a factor 1 to 2 with the values of the same turbulent regimes estimated from the analysis of Zeeman measurements data provided by Crutcher (1999). Constraints on the values of the inclination angle of the mean magnetic field with respect to the LOS are also given. The values obtained from th...

Poidevin, Frederick; Kowal, Grzegorz; Pino, Elisabete de Gouveia Dal; Magalhaes, Antonio-Mario

2013-01-01

345

Photonic Magnetic Field Sensor  

Science.gov (United States)

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

Wyntjes, Geert

2002-02-01

346

The magnetic field of rotating bodies  

International Nuclear Information System (INIS)

The paper discusses the possibility of interpreting the magnetic fields of astronomical bodies in the framework of a unified field theory. Using one of the solutions of the generalized field theory, a direct relation between the polar magnetic field, the angular velocity and the gravitational potential of the body considered, is obtained. The model used for applications has spherical symmetry. The predictions of the theoretical formula, obtained from the model, are compared with available observational data, and with the empirical relation of Blackett. The theoretical formula gives a possible interpretation of a seed magnetic field which will develop and produce the largescale magnetic field observed for celestial objects. The formula shows that the field may be generated as a result of the rotation of the massive object. (author). 24 refs, 3 figs, 1 tab

1991-01-01

347

Fields from a relativistic magnetic explosion  

CERN Multimedia

Following Prendergast we study the relativistically expanding electromagnetic fields generated by an axisymmetric explosion of magnetic energy in a small volume. The magnetic field expands uniformly either within a cone or in all directions and it is therefore accompanied by an electric field. In the highly conducting plasma the charges move to annul the electric field in the frame of the moving plasma. The solutions presented are analytical and semi-analytical. We find that the time-scale for the winding up of the initial magnetic field is crucial, as short time-scales lead to strong radiant fields. Assuming a magnetic field of $10^{13}Gauss$ emerging from a magnetosphere of $10^{9}cm$ we end with a jet when confined by a pressure environment that falls more slowly than $r^{-4}$. The jet carries energy of $10^{51}erg$, which is mostly due to differential rotation at the base.

Gourgouliatos, K N

2008-01-01

348

Control of chaotic magnetic fields in tokamaks  

Scientific Electronic Library Online (English)

Full Text Available SciELO Brazil | Language: English Abstract in english 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.

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

349

Magnetic Fields in Stellar Jets  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Although several lines of evidence suggest that jets from young stars are driven magnetically from accretion disks, existing observations of field strengths in the bow shocks of these flows imply that magnetic fields play only a minor role in the dynamics at these locations. To investigate this apparent discrepancy we performed numerical simulations of expanding magnetized jets with stochastically variable input velocities with the AstroBEAR MHD code. Because the magnetic fi...

Hartigan, P.; Frank, A.; Varniere, P.; Blackman, E.

2007-01-01

350

Scattering by magnetic fields  

CERN Multimedia

Consider the scattering amplitude $s(\\omega,\\omega^\\prime;\\lambda)$, $\\omega,\\omega^\\prime\\in{\\Bbb S}^{d-1}$, $\\lambda > 0$, corresponding to an arbitrary short-range magnetic field $B(x)$, $x\\in{\\Bbb R}^d$. This is a smooth function of $\\omega$ and $\\omega^\\prime$ away from the diagonal $\\omega=\\omega^\\prime$ but it may be singular on the diagonal. If $d=2$, then the singular part of the scattering amplitude (for example, in the transversal gauge) is a linear combination of the Dirac function and of a singular denominator. Such structure is typical for long-range scattering. We refer to this phenomenon as to the long-range Aharonov-Bohm effect. On the contrary, for $d=3$ scattering is essentially of short-range nature although, for example, the magnetic potential $A^{(tr)}(x)$ such that ${\\rm curl} A^{(tr)}(x)=B(x)$ and $=0$ decays at infinity as $|x|^{-1}$ only. To be more precise, we show that, up to the diagonal Dirac function (times an explicit function of $\\omega$), the scattering amplitude has only a w...

Yafaev, D R

2005-01-01

351

Magnetic Field Effect on the Stability of Flow Induced by a Rotating Magnetic Field  

Science.gov (United States)

A linear stability analysis has been performed for the flow induced by a rotating magnetic field in a cylindrical column filled with electrically conducting fluid. The first transition is time- independent and results in the generation of Taylor vortices. The critical value of the magnetic Taylor number has been examined as a function of the strength of the transverse rotating magnetic field, the strength of an axial static magnetic field, and thermal buoyancy. Increasing the transverse field increases the critical magnetic Taylor number and decreases the aspect ratio of the Taylor vortices at the onset of instability. An increase in the axial magnetic field also increases the critical magnetic Taylor number but increases the aspect ratio of the Taylor vortices. Thermal buoyancy is found to have only a negligible effect on the onset of instability.

Mazuruk, K.; Volz, M. P.; Gillies, D. C.

1999-01-01

352

Magnetic Fields in the Solar Convection Zone  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Active regions on the solar surface are generally thought to originate from a strong toroidal magnetic field generated by a deep seated solar dynamo mechanism operating at the base of the solar convection zone. Thus the magnetic fields need to traverse the entire convection zone before they reach the photosphere to form the observed solar active regions. Understanding this process of active region flux emergence is therefore a crucial component for the study of the solar cycle dynamo. This ar...

2009-01-01

353

Adaptable controller of magnetic field homogeneity  

International Nuclear Information System (INIS)

The electrical wiring is described of an adaptable controller of the magnetic field homogeneity. The controller is designed for search and maintenance of the optimal magnetic field homogeneity using a correction system. The system comprises an electronic voltage-to-frequency converter, a clock pulse generator, bidirectional counters, and digital-to-analog converters. The controller is especially suitable for use in NMR spectrometers. (J.B.)

1981-01-01

354

Jet Collimation by Small-Scale Magnetic Fields  

Science.gov (United States)

A popular model for jet collimation is associated with the presence of a large-scale and predominantly toroidal magnetic field originating from the central engine (a star, a black hole, or an accretion disk). Besides the problem of how such a large-scale magnetic field is generated, in this model the jet suffers from the fatal long-wave mode kink magnetohydrodynamic instability. In this paper we explore an alternative model: jet collimation by small-scale magnetic fields. These magnetic fields are assumed to be local, chaotic, and tangled, but are dominated by toroidal components. Just as in the case of a large-scale toroidal magnetic field, we show that the ``hoop stress'' of the tangled toroidal magnetic fields exerts an inward force which confines and collimates the jet. The magnetic ``hoop stress'' is balanced either by the gas pressure of the jet or by centrifugal force if the jet is spinning. Since the length scale of the magnetic field is small (wave mode kink instability. Many other problems associated with the large-scale magnetic field are also eliminated or alleviated for small-scale magnetic fields. Though it remains an open question how to generate and maintain the required small-scale magnetic fields in a jet, the scenario of jet collimation by small-scale magnetic fields is favored by the current study on disk dynamo which indicates that small-scale magnetic fields are much easier to generate than large-scale magnetic fields.

Li, Li-Xin

2002-01-01

355

Atoms in high magnetic fields  

International Nuclear Information System (INIS)

High magnetic fields have been of interest for some time in solid-state physics. Recent spectroscopic experiments on highly excited barium atoms and the discovery of very large magnetic fields in white dwarf stars and neutron stars have stimulated renewed interest in the spectroscopy of free atoms in high magnetic fields. The various spectroscopic regimes ranging from the low-field Zeeman effect to the high-field Landau regime are reviewed and calculations of the energy levels of hydrogen, helium and the isoelectronic ions in fields of any strength are surveyed. Observations of the quadratic Zeeman effect in the alkalis and high-field effects in the neutral barium spectrum are described. Finally, recent discoveries of continuum polarization in white dwarf stars, its interpretation in terms of the presence of high magnetic fields, and confirmation of such fields spectroscopically, and some remaining mysteries in these remarkable stellar spectra, are reviewed. (author)

1977-01-01

356

The magnetic field structure of Rotamak discharges  

International Nuclear Information System (INIS)

This thesis describes an experimental study of a field-reversed compact torus configuration which is generated and sustained by a rotating magnetic field. Earlier studies of this so-called 'rotamak' concept used rotating magnetic fields of limited duration (?15 ?s). The present work extends these studies to a longer timescale (?60 ?s). The rotating magnetic field is produced by feeding RF currents, dephased by 90 deg., through two orthogonal Helmholtz coils which are wound around the outside of a spherical Pyrex vacuum vessel. Line generators are used to supply the RF current pulses. The experiments are performed using an argon plasma. From measurements of the driven toroidal current, two rotamak operating modes are identified. Detailed poloidal flux contour measurements prove that these modes are associated with either a closed magnetic field line, compact torus configuration or an open magnetic field line, mirror-like structure. In the compact torus configuration the driven toroidal current is shown to vary linearly with the magnitude of the externally applied equilibrium field. For the same initial conditions of filling pressure and externally applied equilibrium field, the plasma discharges are highly reproducible. The magnetic structures of the discharges are studied in detail for three such sets of initial conditions. In particular, poloidal flux contours are derived for each of the three conditions. Although no toroidal magnetic field is externally imposed in these experiments, under certain conditions a toroidal field is observed to be present. The toroidal field is in opposite directions in the upper and lower halves of the minor cross section. Measurements of the input power into the plasma show that this power is largely determined by the characteristics of the line-generators. The variation of this input power with time can explain all the features observed in the plasma discharges. The effects of a conducting 'shell' around the vacuum vessel are also investigated. 97 refs., 72 figs., ills

1983-01-01

357

Recurrent flux emergence from dynamo-generated fields  

CERN Multimedia

We investigate the emergence of a large-scale magnetic field. This field is dynamo-generated by turbulence driven with a helical forcing function. Twisted arcade-like field structures are found to emerge in the exterior above the turbulence zone. Time series of the magnetic field structure show recurrent plasmoid ejections.

Warnecke, Jörn

2010-01-01

358

Source of the earth's magnetic field  

International Nuclear Information System (INIS)

The structure and dynamics of the earth's magnetic field are described. The structure and electric, mechanical, and gravitational forces generated in the core and their effects on this field as well as various dynamical models, particularly the heat-driven and the gravitationally powered dynamos, are discussed

1979-01-01

359

Directed Plasma Flow across Magnetic Field  

Science.gov (United States)

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

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

2008-04-01

360

Magnetic Fields in the Solar Convection Zone  

Directory of Open Access Journals (Sweden)

Full Text Available Recent studies of the dynamic evolution of magnetic flux tubes in the solar convection zone are reviewed with focus on emerging flux tubes responsible for the formation of solar active regions. The current prevailing picture is that active regions on the solar surface originate from strong toroidal magnetic fields generated by the solar dynamo mechanism at the thin tachocline layer at the base of the solar convection zone. Thus the magnetic fields need to traverse the entire convection zone before they reach the photosphere to form the observed solar active regions. This review discusses results with regard to the following major topics: 1. the equilibrium properties of the toroidal magnetic fields stored in the stable overshoot region at the base of the convection zone, 2. the buoyancy instability associated with the toroidal magnetic fields and the formation of buoyant magnetic flux tubes, 3. the rise of emerging flux loops through the solar convective envelope as modeled by the thin flux tube calculations which infer that the field strength of the toroidal magnetic fields at the base of the solar convection zone is significantly higher than the value in equipartition with convection, 4. the minimum twist needed for maintaining cohesion of the rising flux tubes, 5. the rise of highly twisted kink unstable flux tubes as a possible origin of d -sunspots, 6. the evolution of buoyant magnetic flux tubes in 3D stratified convection, 7. turbulent pumping of magnetic flux by penetrative compressible convection, 8. an alternative mechanism for intensifying toroidal magnetic fields to significantly super-equipartition field strengths by conversion of the potential energy associated with the superadiabatic stratification of the solar convection zone, and finally 9. a brief overview of our current understanding of flux emergence at the surface and post-emergence evolution of the subsurface magnetic fields.

Fan Yuhong

2004-07-01

 
 
 
 
361

Theory of fossil magnetic field  

CERN Document Server

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

Dudorov, Alexander E

2014-01-01

362

Investigation of highly ionized plasma plumes generated by CO2 laser irradiation of solid targets in strong axial magnetic fields  

International Nuclear Information System (INIS)

This chapter demonstrates the technique of creating uniform plasma conditions using laser irradiation and magnetic confinement. Topics covered include absorption near critical density, absorption in magnetically confined plume, radiative losses, a plasma plume technique, a plasma diagnostic apparatus, instrumentation for XUV-spectroscopy, results of plasma characterization experiments, and time resolved spectroscopic results (C4+ and C5+ ions). Plume formation is achieved by laser heating near the critical density and in a magnetically confined region. Scaling laws are derived to describe both processes. It is indicated that the strong temperature dependence of the laser absorption coefficient in a magnetically confined region results in very good radial uniformity. The temporal history of line radiation from recombining plasma plumes shows good agreement with results of modeling. Includes 2 photos and 2 diagrams

1984-01-01

363

Juno and Jupiter's Magnetic Field (Invited)  

Science.gov (United States)

The Juno spacecraft, launched in August 2011, will reach Jupiter in early July 2016, where it will enter a polar orbit, with an 11 day period and a perijove altitude of approximately 5000 km. The baseline mission will last for one year during which Juno will complete 32 orbits, evenly spaced in longitude. The baseline mission presents an unparalleled opportunity for investigating Jupiter's magnetic field. In many ways Jupiter is a better planet for studying dynamo-generated magnetic fields than the Earth: there are no crustal fields, of course, which otherwise mask the dynamo-generated field at high degree; and an orbiting spacecraft can get proportionately much closer to the dynamo region. Assuming Jupiter's dynamo extends to 0.8 Rj, Juno at closet approach is only 0.3 Rc above the dynamo, while Earth orbiting magnetic field missions sample the field at least 1 Rc above the dynamo (where Rc is the respective outer core or dynamo region radius). Juno's MAG Investigation delivers magnetic measurements with exceptional vector accuracy (100 ppm) via two FGM sensors, each co-located with a dedicated pair of non-magnetic star cameras for attitude determination at the sensor. We expect to image Jupiter's dynamo with unsurpassed resolution. Accordingly, we anticipate that the Juno magnetic field investigation may place important constraints on Jupiter's interior structure, and hence on the formation and evolution of Jupiter.

Bloxham, J.; Connerney, J. E.; Jorgensen, J. L.

2013-12-01

364

Multipactor discharges in magnetic fields  

International Nuclear Information System (INIS)

In the high frequency electric field in vacuum, discharge occurs at a small electric field which does not cause discharge in the case of DC. This is because the number of electrons is doubled due to the emission of secondary electrons from an electrode synchronizing with the high frequency electric field, and it is called multipactor discharge. The multipactor discharge occurs also in nuclear fusion experimental apparatuses, and has drawn attention. The research on the multipactor discharge when a magnetic field exists is few. The authors carried out the experiment on the multipactor discharge in 100 MHz zone in the statical magnetic field up to about 0.08 T, and the theoretical analysis on the voltage at which discharge begins in a vertical magnetic field corresponding to [Angular frequency of electron cyclotron ?(c)]/(Angular frequency of high frequency field ?) < 1. The experimental result and the theoretical analysis result agreed qualitatively. Moreover, the simple theoretical analysis on the monopole multipactor discharge in a vertical magnetic field was carried out. Accompanying the application of a vertical magnetic field, the region where both-pole multipactor discharge is possible moved in the direction of large voltage and f1(f: frequency, 1: distance between electrodes). Both-pole multipactor discharge is cut off at a certain magnetic flux density of a vertical magnetic field. (Kako, I.)

1986-01-01

365

Torsion, neutrinos, and intergalactic magnetic field  

Energy Technology Data Exchange (ETDEWEB)

It is suggested that in the early universe neutrinos with magnetic moment M aligned to generate an ubiquitous magnetic field B. Their alignment was spurred by torsion. With an iterative procedure it was found a relation connecting M to B at any epoch. This result does not depend on the value of the initial torsion, all was needed is an initial torsion no matter how small. With M = 10{sup -}44 erg/gauss one finds B =10{sup -}9 gauss at the present epoch. This value explains the observed mean galactic magnetic field.

Massa, C. [Reggio Emilia, (Italy)

2001-03-01

366

Magnetic fields in laser heated plasmas  

International Nuclear Information System (INIS)

With a fixed-ion code for the study of self-generated magentic fields in laser heated plasmas, the inhibition of thermal transport and the effect of the Nernst term are modeled for a KrF laser. For various values of the flux limiter, the response of a foil to a focused laser is calculated without a magnetic field and compared with the response calculated with a magnetic field. The results are: The Nernst term convects the magnetic field to densities above critical as found by Nishiguchi et al. (1984), but the field does not strongly inhibit transport into the foil. The field is also transported to sub-critical densities, where it inhibits thermal diffusion and enhance lateral transport by convection

1984-10-05

367

High-field magnet facilities and associated technology at Oxford  

Energy Technology Data Exchange (ETDEWEB)

We report on the successful completion and beginning of operation of the high magnetic field lab in Oxford. The lab, named after Nicholas Kurti, is equipped with three magnet stations, where currently the highest fields in the UK are generated. A new high-field pulsed magnet has been designed, which is expected to achieve fields in the 65-70 T range. We also present our latest activities concerning high-temperature superconductors (YBCO), which are a special interest of the magnet group for a new generation of superconducting high-field magnets.

Witte, H.; Jones, H

2004-04-30

368

The Polar BEAR magnetic field experiment  

Science.gov (United States)

The objectives and the instrumentation of the Polar BEAR magnetic field experiment are described along with the preliminary results from simultaneous measurements of Birkeland currents and UV auroral emissions. The experiment consists of an integrated sensor head, analog electronics, and digital electronics. The sensor head is a single unit containing sensor windings for each of the three orthogonal axes, oriented parrallel to the spacecraft coordinates; to minimize interference from spacecraft-generated magnetic fields, the sensor unit is located at the end of the +y solar panel. The digital electronics package is essentially identical to that flown on HILAT. A signal processor digitizes the analog outputs of the three orthogonal axes of the flux-gate magnetometer to a 13-bit resolution, yielding a magnetic field range of + or - 63,000 nT and a resolution of 15.2 nT. The full-resolution magnetic field values are recovered by data processing techniques on the ground.

Bythrow, Peter F.; Potemra, Thomas A.; Zanetti, Lawrence J.; Mobley, Frederick F.; Scheer, Leonard

1987-09-01

369

Discontinuities in the magnetic field near Enceladus  

Science.gov (United States)

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 flux tube (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 flux tube. 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.

Simon, Sven; Saur, Joachim; Treeck, Shari C.; Kriegel, Hendrik; Dougherty, Michele K.

2014-05-01

370

Inflation and late-time cosmic acceleration in non-minimal Maxwell-F(R) gravity and the generation of large-scale magnetic fields  

Science.gov (United States)

We study inflation and late-time acceleration in the expansion of the universe in non-minimal electromagnetism, in which the electromagnetic field couples to the scalar curvature function. It is shown that power-law inflation can be realized due to the non-minimal gravitational coupling of the electromagnetic field, and that large-scale magnetic fields can be generated due to the breaking of the conformal invariance of the electromagnetic field through its non-minimal gravitational coupling. Furthermore, it is demonstrated that both inflation and the late-time acceleration of the universe can be realized in a modified Maxwell-F(R) gravity which is consistent with solar-system tests and cosmological bounds and free of instabilities. At small curvature typical for the current universe the standard Maxwell theory is recovered. We also consider the classically equivalent form of non-minimal Maxwell-F(R) gravity, and propose the origin of the non-minimal gravitational coupling function based on renormalization-group considerations.

Bamba, Kazuharu; Odintsov, Sergei D.

2008-04-01

371

Inflation and late-time cosmic acceleration in non-minimal Maxwell-F(R) gravity and the generation of large-scale magnetic fields  

International Nuclear Information System (INIS)

We study inflation and late-time acceleration in the expansion of the universe in non-minimal electromagnetism, in which the electromagnetic field couples to the scalar curvature function. It is shown that power-law inflation can be realized due to the non-minimal gravitational coupling of the electromagnetic field, and that large-scale magnetic fields can be generated due to the breaking of the conformal invariance of the electromagnetic field through its non-minimal gravitational coupling. Furthermore, it is demonstrated that both inflation and the late-time acceleration of the universe can be realized in a modified Maxwell-F(R) gravity which is consistent with solar-system tests and cosmological bounds and free of instabilities. At small curvature typical for the current universe the standard Maxwell theory is recovered. We also consider the classically equivalent form of non-minimal Maxwell-F(R) gravity, and propose the origin of the non-minimal gravitational coupling function based on renormalization-group considerations

2008-04-01

372

Inflation and late-time cosmic acceleration in non-minimal Maxwell-F(R) gravity and the generation of large-scale magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

We study inflation and late-time acceleration in the expansion of the universe in non-minimal electromagnetism, in which the electromagnetic field couples to the scalar curvature function. It is shown that power-law inflation can be realized due to the non-minimal gravitational coupling of the electromagnetic field, and that large-scale magnetic fields can be generated due to the breaking of the conformal invariance of the electromagnetic field through its non-minimal gravitational coupling. Furthermore, it is demonstrated that both inflation and the late-time acceleration of the universe can be realized in a modified Maxwell-F(R) gravity which is consistent with solar-system tests and cosmological bounds and free of instabilities. At small curvature typical for the current universe the standard Maxwell theory is recovered. We also consider the classically equivalent form of non-minimal Maxwell-F(R) gravity, and propose the origin of the non-minimal gravitational coupling function based on renormalization-group considerations.

Bamba, Kazuharu [Department of Physics, Kinki University, Higashi-Osaka 577-8502 (Japan); Odintsov, Sergei D, E-mail: bamba@phys.kindai.ac.jp, E-mail: odintsov@aliga.ieec.uab.es [Institucio Catalana de Recerca i Estudis Avancats (ICREA), Campus UAB, Facultat de Ciencies, Torre C5-Par-2a pl, E-08193 Bellaterra (Barcelona) (Spain)

2008-04-15

373

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

Magnetism is a fundamental interaction shaping our physical world, at the basis of technologies such as magnetic recording or energy generation. Unlike electromagnetic waves, which can be routed and transmitted with waveguides to long distances, magnetic fields rapidly decay with distance. Here we show the concept, design, and properties of a magnetic hose which enables to transfer the static magnetic field generated by a source to an arbitrary distance, and along any given ...

Navau, Carles; Prat-camps, Jordi; Romero-isart, Oriol; Cirac, J. Ignacio; Sanchez, Alvaro

2013-01-01

374

Generation of non-equilibrium thermal quantum discord and entanglement in a three-spin XX chain by multi-spin interaction and an external magnetic field  

International Nuclear Information System (INIS)

The generation of non-equilibrium thermal quantum discord and entanglement is investigated in a three-spin chain whose two end spins are respectively coupled to two thermal reservoirs at different temperatures. We show that the spin chain can be decoupled from the thermal reservoirs by homogeneously applying a magnetic field and including a strong three-spin interaction, and then the maximal steady-state quantum discord and entanglement in the two end spins can always be created. In addition, the present investigation may provide a useful approach to control coupling between a quantum system and its environment. -- Highlights: ? Spin chain decoupled from thermal reservoirs. ? Thermal excitation depressed. ? Maximal quantum correlations created.

2011-11-07

375

Homogeneous magnetic field in a cylindrical shell  

International Nuclear Information System (INIS)

A highly homogeneous magnetic field complying with different criteria of homogeneity was generated using four coils. The design parameters that minimised the RMS deviation of the field intensity from a constant value throughout the region of interest, were determined numerically. Electrons' trajectories from points along the source to a plane target, were calculated to evaluate the effect of the residual inhomogeneity of the optimal field. A four-coil system accurately implementing optimal design parameters, was built and successfully tested. (author)

1984-01-01

376

Homogeneous magnetic field in a cylindrical shell  

Energy Technology Data Exchange (ETDEWEB)

A highly homogeneous magnetic field complying with different criteria of homogeneity was generated using four coils. The design parameters that minimised the RMS deviation of the field intensity from a constant value throughout the region of interest, were determined numerically. Electrons trajectories from points along the source to a plane target, were calculated to evaluate the effect of the residual inhomogeneity of the optimal field. A four-coil system accurately implementing optimal design parameters, was built and successfully tested.

Friedman, M.; Avida, R.; Brandstadter, J. (Israel Atomic Energy Commission, Beersheba); Erez, G.

1984-03-01

377

Design of heliac vacuum magnetic fields  

International Nuclear Information System (INIS)

The design of vacuum magnetic fields for helical axis stellarators (HELIACS) is investigated. The aim is to produce realistic configurations possessing magnetic wells (for stability), favourable transform with low shear (to avoid resonant rational surfaces), and small variation of Q=?dl/B (to minimize parallel currents). An asymmetric toroidal domain whose boundary is assumed to be an outer magnetic surface is created by helically winding a poloidal cross-section about a circle. The magnetic scalar potential inside the domain is computed numerically and field-line integrations are performed in order to evaluate the field properties. The magnetic field is generated by skin currents flowing along the equipotential contours on the boundary. These currents are then discretized into a modular coil system, whose resulting magnetic field is compared with that of the corresponding continuum. Skin current configurations having a shallow well and favourable beta limitations and Q-variation are presented. Discretization of the skin current usually results in a magnetic field which preserves the transform and Q-variation, but with less favourable well properties. (author)

1985-01-01

378

Magnetic field waves at Uranus  

Science.gov (United States)

The research efforts funded by the Uranus Data Analysis Program (UDAP) grant to the Bartol Research Institute (BRI) involved the study of magnetic field waves associated with the Uranian bow shock. Upstream wave studies are motivated as a study of the physics of collisionless shocks. Collisionless shocks in plasmas are capable of 'reflecting' a fraction of the incoming thermal particle distribution and directing the resulting energetic particle motion back into the upstream region. Once within the upstream region, the backward streaming energetic particles convey information of the approaching shock to the supersonic flow. This particle population is responsible for the generation of upstream magnetic and electrostatic fluctuations known as 'upstream waves', for slowing the incoming wind prior to the formation of the shock ramp, and for heating of the upstream plasma. The waves produced at Uranus not only differed in several regards from the observations at other planetary bow shocks, but also gave new information regarding the nature of the reflected particle populations which were largely unmeasurable by the particle instruments. Four distinct magnetic field wave types were observed upstream of the Uranian bow shock: low-frequency Alfven or fast magnetosonic waves excited by energetic protons originating at or behind the bow shock; whistler wave bursts driven by gyrating ion distributions within the shock ramp; and two whistler wave types simultaneously observed upstream of the flanks of the shock and argued to arise from resonance with energetic electrons. In addition, observations of energetic particle distributions by the LECP experiment, thermal particle populations observed by the PLS experiment, and electron plasma oscillations recorded by the PWS experiment proved instrumental to this study and are included to some degree in the papers and presentations supported by this grant.

Smith, Charles W.; Goldstein, Melvyn L.; Lepping, Ronald P.; Mish, William H.; Wong, Hung K.

1994-01-01

379

Magnetic fields of the Sun  

International Nuclear Information System (INIS)

Magnetic fields of the Sun are considered. Medium, large-scale Sun magnetic field exists. Its axial-symmetric poloidal component is characterised by the intensity of the order of 1 Gs and by dipole-type space mode, oriented along rotation axis. Furthermore, a weak non-axial-symmetric field (about 0.5 Gs), corresponding to dipole and (or) quadrupole, the axes of which are found in the solar equator plane. Magnetic field of the Sun does not remain unchangeable. Small-scale fields change in an irregular, random way. The field non-axial-symmetric component changes approximately with the period of the Sun rotation around its axis. 22-year axial-symmetric field cycle is well known

1986-11-01

380

MAGNETIC FIELDS FROM QCD PHASE TRANSITIONS  

Energy Technology Data Exchange (ETDEWEB)

We study the evolution of QCD phase transition-generated magnetic fields (MFs) in freely decaying MHD turbulence of the expanding universe. We consider an MF generation model that starts from basic non-perturbative QCD theory and predicts stochastic MFs with an amplitude of the order of 0.02 {mu}G and small magnetic helicity. We employ direct numerical simulations to model the MHD turbulence decay and identify two different regimes: a 'weakly helical' turbulence regime, when magnetic helicity increases during decay, and 'fully helical' turbulence, when maximal magnetic helicity is reached and an inverse cascade develops. The results of our analysis show that in the most optimistic scenario the magnetic correlation length in the comoving frame can reach 10 kpc with the amplitude of the effective MF being 0.007 nG. We demonstrate that the considered model of magnetogenesis can provide the seed MF for galaxies and clusters.

Tevzadze, Alexander G. [Faculty of Exact and Natural Sciences, Javakhishvili Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi 0128 (Georgia); Kisslinger, Leonard; Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Brandenburg, Axel, E-mail: aleko@tevza.org [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

2012-11-01

 
 
 
 
381

Magnetic fields and scintillator performance  

International Nuclear Information System (INIS)

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

1995-01-01

382

Electrons in superstrong magnetic field  

Energy Technology Data Exchange (ETDEWEB)

Interaction of an electron moving in a superstrong magnetic field Hsub(c) is considered. To describe such quantum phemomena in Hsub(c) as dependence of radiative corrections to the ground state of the electron on H/Hsub(c) ratio, synchrotron radiation, anomalous magnetic moment of the electron, distortion of the Coulomb potential due to polarization of the electron vacuum, Dirac quantum mechanics is used. The state of the electron in the magnetic field of high intensity is described by the wave function which is the solution of the Dirac equation in which electron and field interaction is accurately taken into account.

Ternov, I.M.; Khalilov, V.R. (Moskovskij Gosudarstvennyj Univ. (USSR))

1983-05-01

383

Magnetic Field Effect Transistors.  

Science.gov (United States)

It has been demonstrated that magnetic Cr02 can be selectively deposited on semiconductor substrates and polymide resin plastics with feature resolution smaller than micron. In addition, hard coatings have been fabricated to protect active devices as well...

J. T. Spencer P. A. Dowben

1990-01-01

384

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

1984-02-13

385

Generation of Gaussian Density Fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This document describes analytical and numerical techniques for the generation of Gaussian density fields, which represent cosmological density perturbations. The mathematical techniques involved in the generation of density harmonics in k-space, the filtering of the density fields, and the normalization of the power spectrum to the measured temperature fluctuations of the Cosmic Microwave Background, are presented in details. These techniques are well-known amongst experts,...

Martel, Hugo

2005-01-01

386

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

Science.gov (United States)

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

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

387

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

1984-12-14

388

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

2008-02-01

389

ISR split-field magnet  

CERN Multimedia

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.

1975-01-01

390

ISR split-field magnet  

CERN Multimedia

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.

1974-01-01

391

Magnetic field transfer device and method  

Energy Technology Data Exchange (ETDEWEB)

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

Wipf, Stefan L. (Hamburg, DE)

1990-01-01

392

Magnetic field effect on capillary rise of magnetic fluids  

International Nuclear Information System (INIS)

The objective of this work is to study the effect of the external uniform magnetic field on the height and dynamics of magnetic fluid ascension into a vertical cylindrical capillary. Due to demagnetization effects in the magnetic fluid, the height of ascension increases in the magnetic field longitudinal to the capillary and decreases in the transverse field, proportionally to the square of the magnetic fluid magnetization. Magnetic fluid ascension decelerates strongly in the transverse field

2005-03-01

393

Rigidity for periodic magnetic fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We study the motion of a charge on a conformally flat Riemannian torus in the presence of magnetic field. We prove that for any non-zero magnetic field there always exist orbits of this motion which have conjugate points. We conjecture that the restriction of conformal flatness of the metric is not essential for this result. This would provide a ``twisted'' version of the recent generalisation of Hopf's rigidity result obtained by Burago and Ivanov.

Bialy, M. L.

1999-01-01

394

PERMANENT-MAGNET INDUCTION GENERATORS: AN OVERVIEW  

Directory of Open Access Journals (Sweden)

Full Text Available 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-up, modelling, steady-state and performance analysis of the permanent-magnet induction generators.

K. S. S. RAMAKRISHNAN

2011-06-01

395

Magnetic fields on the Sun  

International Nuclear Information System (INIS)

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

1981-01-01

396

SEED BANKS FOR MAGNETIC FLUX COMPRESSION GENERATORS  

Energy Technology Data Exchange (ETDEWEB)

In recent years the Lawrence Livermore National Laboratory (LLNL) has been conducting experiments that require pulsed high currents to be delivered into inductive loads. The loads fall into two categories (1) pulsed high field magnets and (2) the input stage of Magnetic Flux Compression Generators (MFCG). Three capacitor banks of increasing energy storage and controls sophistication have been designed and constructed to drive these loads. One bank was developed for the magnet driving application (20kV {approx} 30kJ maximum stored energy.) Two banks where constructed as MFCG seed banks (12kV {approx} 43kJ and 26kV {approx} 450kJ). This paper will describe the design of each bank including switching, controls, circuit protection and safety.

Fulkerson, E S

2008-05-14

397

Measuring the Earth's magnetic field in a laboratory  

International Nuclear Information System (INIS)

Two methods for measuring the Earth's magnetic field are described. In the former, according to Gauss, the Earth's magnetic field is compared with that of a permanent magnet; in the latter, a well-known method, the comparison is made with the magnetic field generated by a current. As all the used instruments are available off the shelf, both methods are cheap. With some attention to the procedure, both methods give accurate results

2008-07-01

398

Theorem on magnet fringe field  

International Nuclear Information System (INIS)

Transverse particle motion in particle accelerators is governed almost totally by non-solenoidal magnets for which the body magnetic field can be expressed as a series expansion of the normal (bn) and skew (an) multipoles, By + iBx = summation(bn + ian)(x + iy)n, where x, y, and z denote horizontal, vertical, and longitudinal (along the magnet) coordinates. Since the magnet length L is necessarily finite, deflections are actually proportional to ''field integrals'' such as bar BL ? ? B(x,y,z)dz where the integration range starts well before the magnet and ends well after it. For bar an, bar bn, bar Bx, and bar By defined this way, the same expansion Eq. 1 is valid and the ''standard'' approximation is to neglect any deflections not described by this expansion, in spite of the fact that Maxwell's equations demand the presence of longitudinal field components at the magnet ends. The purpose of this note is to provide a semi-quantitative estimate of the importance of |?p?|, the transverse deflection produced by the ion-gitudinal component of the fringe field at one magnet end relative to |?p0|, the total deflection produced by passage through the whole magnet. To emphasize the generality and simplicity of the result it is given in the form of a theorem. The essence of the proof is an evaluation of the contribution of the longitudinal field Bx from the vicinity of one magnet end since, along a path parallel to the magnet axis such as path BC

1995-10-15

399

Untwisting magnetic fields in the solar corona  

Science.gov (United States)

The solar corona is the tenuous atmosphere of the Sun characterized by a temperature of the order of million degrees Kelvin, an ambient magnetic field of 10 to 15 Gauss and a very high magnetic Reynolds number because of which it qualifies as a near-ideal magnetofluid system. It is well known that for such a system, the magnetic flux across every fluid surface remains effectively constant to a good approximation. Under this so called ``frozen-in'' condition then, it is possible to partition this magnetofluid into contiguous magnetic subvolumes each entrapping its own subsystem of magnetic flux. Thin magnetic flux tubes are an elementary example of such magnetic subvolumes evolving in time with no exchange of fluid among them. The internal twists and interweaving of these flux tubes, collectively referred as the magnetic topology, remains conserved under the frozen-in condition. Because of the dynamical evolution of the magnetofluid, two such subvolumes can come into direct contact with each other by expelling a third interstitial subvolume. In this process, the magnetic field may become discontinuous across the surface of contact by forming a current sheet there. Because of the small spatial scales generated by steepening of magnetic field gradient, the otherwise negligible resistivity becomes dominant and allows for reconnection of field lines which converts magnetic energy into heat. This phenomenon of spontaneous current sheet formation and its subsequent resistive decay is believed to be a possible mechanism for heating the solar corona to its million degree Kelvin temperature. In this work the dynamics of spontaneous current sheet formation is explored through numerical simulations and the results are presented.

Bhattacharyya, Ramit; Smolarkiewicz, Piotr; Chye Low, Boon

2012-07-01

400

Field measurements for PETRA magnets  

International Nuclear Information System (INIS)

Two fast measuring machines have been built for measuring the great series of dipoles and focussing magnets for PETRA. The measuring system consists of a machine with a long moving integrating coil for measuring the dipoles and of a rotating coil system for an integral measurement of quadrupoles, sextupoles and other higher multipoles. Both machines are computer controlled. Results of field measurements for the first part of the series magnets are presented. The measurements show the profile of the integral field and the improvements due to end-field corrections. Magnets of the same type are compared as to integral field for gradient. The effect of different energizing cycles on the reproducibility of field setting is described. (author)

1977-09-02

 
 
 
 
401

High-field superconducting accelerator magnets  

International Nuclear Information System (INIS)

The next generation of accelerators for high-energy physics will require high-field, small-bore dipole magnets: in the region of 10 T and 40-mm diam. For such magnets, there is a great incentive to attain high overall current density through increasing the current density within the superconductor and minimizing the copper stabilizer. Both Nb-Ti operating at 1.8 K and Nb_3sn at 4.2 are candidate superconductors. Two programs in the US and one in Japan are directed toward the development of such magnets. The program at LBL is described below

1982-05-14

402

Mapping of confinement magnetic field  

International Nuclear Information System (INIS)

The present magnetic field confinement device for high temperature plasma consists of torus, and its representative tokamak basically has axisymmetry, but the symmetry is broken by various causes such as the errors in the devices and MHD instability. In asymmetric magnetic fields, the lines of magnetic force present chaotic state locally in the vicinity of the resonance magnetic surface due to the nonlinearity. In the study, for helical torus magnetic fields, the method of deriving approximately scalar potential and flux function (Hamiltonian) by double Fourier development method is proposed, and the example of application is shown. By this Hamiltonian, the information required for the design of devices can be obtained, and the chaotic state can be examined. The derivation of toroidal helical magnetic field is described. Toroidal helical flux function along the lines of magnetic force is shown. The example of the calculated helical pinch plasma is shown. The state of the tracks by the approximated Hamiltonian in the vicinity of the separatrix was examined by separatrix mapping. The results of having carried out the separatrix mapping 10,000 times are shown. (K.I.)

1994-04-01

403

Magnetic field analysis of high gradient magnetic separator via finite element analysis  

Energy Technology Data Exchange (ETDEWEB)

High Gradient Magnetic Separator (HGMS) uses matrix to make high magnetic field gradient so that ferro- or para-magnetic particles can be attracted to them by high magnetic force. The magnetic force generated by the field gradient is several thousand times larger than that by the magnetic flux density alone. So the HGMS shows excellent performance compared with other magnetic separators. These matrices are usually composed of stainless wires having high magnetization characteristics. This paper deals with superconducting HGMS which is aimed for purifying wastewater by using stainless steel matrix. Background magnetic field up to 6 T is generated by a superconducting solenoid and the stainless steel matrices are arranged inside of the solenoid. In order to calculate magnetic forces exerting on magnetic particles in wastewater, it is important to calculate magnetic field and magnetic field gradient those are proportional to the magnetic force acting on the particle. So we presents magnetic field distribution analysis result and estimates how many times of magnetic force will act on a particle when the matrix are arranged or not. Magnetic field is calculated in 3 dimensions by using Finite Element Method (FEM) and also compared with results obtained from 2 dimensional analysis.

Baik, S.K., E-mail: skbaik@keri.re.kr [Korea Electrotechnology Research Institute, Seongju-dong 28-1, Changwon (Korea, Republic of); Ha, D.W.; Ko, R.K.; Kwon, J.M. [Korea Electrotechnology Research Institute, Seongju-dong 28-1, Changwon (Korea, Republic of)

2012-10-15

404

Magnetic fields in neutron stars  

Science.gov (United States)

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 magnetosphere. Modeling its global configuration is important to understand the observational properties of the most magnetized neutron stars, magnetars. On the other hand, magnetic fields in the interior are thought to evolve on long time-scales, from thousands to millions of years. The magnetic evolution is coupled to the thermal one, which has been the subject of study in the last decades. An important part of this thesis presents the state-of-the-art of the magneto-thermal evolution models of neutron stars during the first million of years, studied by means of detailed simulations. The numerical code here described is the first one to consistently consider the coupling of magnetic field and temperature, with the inclusion of both the Ohmic dissipation and the Hall drift in the crust.

Viganò, Daniele

2013-09-01

405

Permanent Magnet Spiral Motor for Magnetic Gradient Energy Utilization: Axial Magnetic Field  

Science.gov (United States)

The Spiral Magnetic Motor, which can accelerate a magnetized rotor through 90% of its cycle with only permanent magnets, was an energy milestone for the 20th century patents by Kure Tekkosho in the 1970's. However, the Japanese company used old ferrite magnets which are relatively weak and an electrically-powered coil to jump start every cycle, which defeated the primary benefit of the permanent magnet motor design. The principle of applying an inhomogeneous, anisotropic magnetic field gradient force Fz = ? cos J dB/dz, with permanent magnets is well-known in physics, e.g., Stern-Gerlach experiment, which exploits the interaction of a magnetic moment with the aligned electron spins of magnetic domains. In this case, it is applied to dB/d? in polar coordinates, where the force F? depends equally on the magnetic moment, the cosine of the angle between the magnetic moment and the field gradient. The radial magnetic field increases in strength (in the attractive mode) or decreases in strength (in the repulsive mode) as the rotor turns through one complete cycle. An electromagnetic pulsed switching has been historically used to help the rotor traverse the gap (detent) between the end of the magnetic stator arc and the beginning (Kure Tekko, 1980). However, alternative magnetic pulse and switching designs have been developed, as well as strategic eddy current creation. This work focuses on the switching mechanism, novel magnetic pulse methods and advantageous angular momentum improvements. For example, a collaborative effort has begun with Toshiyuki Ueno (University of Tokyo) who has invented an extremely low power, combination magnetostrictive-piezoelectric (MS-PZT) device for generating low frequency magnetic fields and consumes ``zero power'' for static magnetic field production (Ueno, 2004 and 2007a). Utilizing a pickup coil such as an ultra-miniature millihenry inductor with a piezoelectric actuator or simply Wiegand wire geometry, it is shown that the necessary power for magnetic field switching device can be achieved in order to deflect the rotor magnet in transit. The Wiegand effect itself (bistable FeCoV wire called ``Vicalloy'') invented by John Wiegand (Switchable Magnetic Device, US Patent No.4,247,601), utilizing Barkhausen jumps of magnetic domains, is also applied for a similar achievement (Dilatush, 1977). Conventional approaches for spiral magnetic gradient force production have not been adequate for magnetostatic motors to perform useful work. It is proposed that integrating a magnetic force control device with a spiral stator inhomogeneous axial magnetic field motor is a viable approach to add a sufficient nonlinear boundary shift to apply the angular momentum and potential energy gained in 315 degrees of the motor cycle.

Valone, Thomas F.

2010-01-01