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1

Fifth-order aberrations in magnetic quadrupole-octupole systems  

Energy Technology Data Exchange (ETDEWEB)

Explicit integral expressions are given for the fifth-order geometrical aberration coefficients in rectilinear magnetic quadrupole-octupole systems used for the transport of nonrelativistic charged particle beams. The numerical values of the fifth-order geometrical aberration coefficients for a rare earth cobalt (REC) quadrupole doublet are given as an example. 26 refs., 5 figs., 4 tabs.

Ling, K.M.

1990-01-01

2

Modified octupoles for damping coherent instabilities  

International Nuclear Information System (INIS)

[en] The introduction tune spread in circular e+e- accelerators with modified octupoles to reduce the loss of dynamic aperture is discussed. The new magnet design features an octupole of field component on-axis and a tapered field structure off-axis to minimize loss of dynamic aperture. Tracking studies show that the modified octupoles can produce the desired tune spread in SPEAR without compromising confinement of the beam. The technique for designing such magnets is presented, together with an example of magnets that give the required field distribution. 7 refs., 7 figs

1991-01-01

3

Progress Towards A Permanent Octupole Magnetic Ultra-Cold Neutron Trap for Lifetime Measurements  

CERN Document Server

The current knowledge of the neutron $\\beta$-decay lifetime has come under scrutiny as of late due to large disagreements between recent precise measurements. Measurements using magnetically trapped Ultra-Cold Neutrons (UCNs) offer the possibility of storage without spurious losses which can provide a reliable value for the neutron lifetime. The progress towards realizing a neutron lifetime measurement using a Ioffe-type trap made with a Halbach-type permanent octupole magnet is presented here. The experimental procedure extracts a gas of UCNs into vacuum, which reduces many known channels of neutron losses, and detects the neutron decays via in-situ detection of the produced protons.

Leung, Kent

2008-01-01

4

Octupole degree of freedom for nuclei near 152Sm in a reflection-asymmetric relativistic mean-field approach  

International Nuclear Information System (INIS)

The potential energy surfaces of even-even isotopes near 152Sm are investigated within the constrained reflection-asymmetric relativistic mean-field approach using parameter sets PK1 and NL3. It is shown that the critical-point candidate nucleus 152Sm marks the shape/phase transition not only from U(5) to SU(3) symmetry, but also from the octupole deformed ground state in 150Sm to the quadrupole deformed ground state in 154Sm. The important role of the octupole deformation driving pair (?2f7/2, ?1i13/2) is demonstrated based on the components of the single-particle levels near the Fermi surface. In addition, the patterns of both the proton and the neutron octupole deformation driving pairs (?2f7/2, ?1i13/2) and (?2d5/2, ?1h11/2) are investigated.

2011-09-23

5

Magnetic fields for transporting charged beams  

International Nuclear Information System (INIS)

[en] The transport of charged particle beams requires magnetic fields that must be shaped correctly and very accurately. During the last 20 years or so, many studies have been made, both analytically and through the use of computer programs, of various magnetic shapes that have proved to be useful. Many of the results for magnetic field shapes can be applied equally well to electric field shapes. A report is given which gathers together the results that have more general significance and would be useful in designing a configuration to produce a desired magnetic field shape. The field shapes studied include the fields in dipoles, quadrupoles, sextupoles, octupoles, septum magnets, combined-function magnets, and electrostatic septums. Where possible, empirical formulas are proposed, based on computer and analytical studies and on magnetic field measurements. These empirical formulas are often easier to use than analytical formulas and often include effects that are difficult to compute analytically. In addition, results given in the form of tables and graphs serve as illustrative examples. The field shapes studied include uniform fields produced by window-frame magnets, C-magnets, H-magnets, and cosine magnets; linear fields produced by various types of quadrupoles; quadratic and cubic fields produced by sextupoles and octupoles; combinations of uniform and linear fields; and septum fields with sharp boundaries

1976-01-01

6

Multiparticle octupole coupling and magnetic moments of hn9/2 isomers in N=126 isotones  

International Nuclear Information System (INIS)

[en] The influence of particle-vibration coupling on the g-factors of the (h9/2)n > isomers in the N = 126 isotones is assessed using the multiparticle octupole coupling model. According to the model, admixtures of the configuration (h9/2)n-1 f7/2> in the yrast 8+ and 21/2-states, nominally associated with the configuration (h9/2)n >, increase with n. On its own, the octupole mixing mechanism therefore predicts g-factors for these states that increase with the number of valence protons. This trend is the opposite of that predicted by core-polarization blocking. Combining multiparticle octupole coupling and first order core-polarization blocking significantly reduces the discrepancy between the experimental and theoretical g-factors of these states. It is concluded that the observed breakdown in additivity for the g-factors of the (h9/2)n > isomers in the N = 126 isotones arises primarily from first order core-polarization blocking and the combination of configuration mixing due to multiparticle octupole coupling and shell model residual interactions. 40 refs., 5 tabs., 3 figs

1992-01-01

7

Uniform beam distributions using octupoles  

Energy Technology Data Exchange (ETDEWEB)

The Gaussian beam profile of the BNL 200 MeV H{sup {minus}} Linac beam at the Radiation Effects Facility target location was transformed into a rectangular profile with almost uniform distribution by placing two octupole magnetic elements at particular locations along the beam line. Experimental results of the beam profile projection in the horizontal and vertical planes, with and without octupoles, are presented and compared with third order calculations. 7 refs., 3 figs.

Tsoupas, N.; Lankshear, R.; Snead, C.L. Jr.; Ward, T.E.; Zucker, M. (Brookhaven National Lab., Upton, NY (USA)); Enge, H.A. (Deuteron, Inc., Lincoln, MA (USA))

1991-01-01

8

Magnetic Fields  

Science.gov (United States)

Students visualize the magnetic field of a strong permanent magnet using a compass. The lesson begins with an analogy to the effect of the earthâs magnetic field on a compass. Students see the connection that the compass simply responds to the earthâs magnetic field since it is the closest, strongest field, and therefore the compass will respond to the field of the permanent magnets, allowing them the ability to map the field of that magnet in the activity. This information will be important in designing a solution to the grand challenge in activity 4 of the unit.

Vu Bioengineering Ret Program

9

Hyperfine structure of the metastable 3P2 state of alkaline earth atoms as an accurate probe of nuclear magnetic octupole moments  

CERN Document Server

Measuring the hyperfine structure (HFS) of long-lived $^3P_2$ states of divalent atoms may offer the opportunity of extracting relatively unexplored nuclear magnetic octupole and electric hexadecapole moments. Here, using relativistic many-body methods of atomic structure and the nuclear shell model, we evaluate the effect of these higher nuclear moments on the hyperfine structure. We find that the sensitivity of HFS interval measurements in $^{87}$Sr needed to reveal the perturbation caused by the nuclear octupole moment is on the order of kHz. Results of similar analyses for $^{9}$Be, $^{25}$Mg, and $^{43}$Ca are also reported.

Beloy, K; Johnson, W R

2007-01-01

10

Octupole degree of freedom for the critical-point candidate nucleus $^{152}$Sm in a reflection-asymmetric relativistic mean-field approach  

CERN Document Server

The potential energy surfaces of even-even $^{146-156}$Sm are investigated in the constrained reflection-asymmetric relativistic mean-field approach with parameter set PK1. It is shown that the critical-point candidate nucleus $^{152}$Sm marks the shape/phase transition not only from U(5) to SU(3) symmetry, but also from the octupole-deformed ground state in $^{150}$Sm to the quadrupole-deformed ground state in $^{154}$Sm. By including the octupole degree of freedom, an energy gap near the Fermi surface for single-particle levels in $^{152}$Sm with $\\beta_2 = 0.14 \\sim 0.26$ is found, and the important role of the octupole deformation driving pair $\

Zhang, W; Zhang, S Q; Meng, J; 10.1103/PhysRevC.81.034302

2010-01-01

11

Magnetic Fields  

Science.gov (United States)

This page and its annex describes, in trivial terms, the physics of magnetic fields and the history of its discovery. Included is the work of Halley, Oersted, Ampere and Maxwell. It also describes a way of demonstrating it in the classroom, using a vu-graph projector. Later sections #5, #5a and #6 extend this to magnetic field lines and electromagnetism.

Stern, David

2005-01-04

12

Study of octupoles as correctors  

Energy Technology Data Exchange (ETDEWEB)

In an electron microscope equipped with sextupole correctors the ultimate resolution is limited by the fifth-order spherical aberration of the optical system used to form the electron probe. We have examined the possibilities of using octupoles in order to correct this fifth-order spherical aberration. We find that for an electrostatic octupole, the fifth-order aberration is symmetric, while for a magnetic octupole the fifth-order aberration is asymmetric but it is possible to reduce this asymmetry by properly arranging the initial conditions. Based on these results, we propose a system which could be used to correct fifth-order aberration in a probe forming system equipped with a sextupole corrector.

Shao, Z.; Beck, V.; Crewe, A.V.

1988-08-15

13

Octupole vibrations in nuclei  

Energy Technology Data Exchange (ETDEWEB)

Phenomenological - geometric and algebraic - and microscopic approaches to the problem of octupole vibrations in nuclei are reviewed. In particular, the collective model of nuclear octupole motion, its structure and symmetries are recapitulated in detail. Theoretical descriptions are compared with experimental data. We also try to elucidate a peculiarity of the octupole degrees of freedom.

Rohozinski, S.G.

1988-04-01

14

Zonal harmonic model of Saturn's magnetic field from Voyager 1 and 2 observations  

Energy Technology Data Exchange (ETDEWEB)

An axisymmetric octupole model of Saturn's planetary magnetic field is proposed. This three parameter model is extremely efficient in representing the main magnetic field of Saturn and reconciling the in situ magnetic field observations obtained by Pioneer 11 with those obtained by the Voyager 1 and 2 space-craft. Saturn's unique field configuration is thus not that of a simple displaced dipole but rather appears to be the axisymmetric part of a complex dynamo field.

Connerney, J.E.P.; Ness, N.F.; Acuna, M.H. (National Aeronautics and Space Administration, Greenbelt, MD (USA). Goddard Space Flight Center)

1982-07-01

15

Magnetic octupole order in Ce{sub 0.7}La{sub 0.3}B{sub 6}: A polarized neutron diffraction study  

Energy Technology Data Exchange (ETDEWEB)

Recently, in phase IV of Ce{sub x}La{sub 1-x}B{sub 6}, weak but distinct superlattice reflections from the order parameter of phase IV have been detected by our unpolarized neutron scattering experiment [K. Kuwahara, K. Iwasa, M. Kohgi, N. Aso, M. Sera, F. Iga, J. Phys. Soc. Japan 76 (2007) 093702]. The scattering vector dependence of the intensity of superlattice reflections is quite unusual; the intensity is stronger for high scattering vectors. This result strongly indicates that the order parameter of phase IV is the magnetic octupole. However, the possibility that the observed superlattice reflections are due to lattice distortions could not be completely ruled out only on the basis of the unpolarized neutron scattering experiment. To confirm that the superlattice reflections are magnetic, therefore, we have performed a single crystal polarized neutron diffraction experiment on Ce{sub 0.7}La{sub 0.3}B{sub 6}. The obtained result has clearly shown that the time reversal symmetry is broken by the order parameter of phase IV. This is further evidence for the magnetic octupole order in Ce{sub x}La{sub 1-x}B{sub 6}.

Kuwahara, K., E-mail: kuwa@mx.ibaraki.ac.j [Institute of Applied Beam Science, Ibaraki University, Ibaraki 310-8512 (Japan); Iwasa, K. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Kohgi, M. [Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397 (Japan); Aso, N. [Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, Ibaraki 319-1106 (Japan); Sera, M.; Iga, F. [Department of Quantum Matter, ADSM, Hiroshima University, Hiroshima 739-8530 (Japan); Matsuura, M.; Hirota, K. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan)

2009-09-01

16

On the existence of a magnetic octupole moment in mesic atoms in 1S1/2 and 2P1/2 states  

International Nuclear Information System (INIS)

[en] It is shown that mesic atoms, their nucleus spin J?1, still possess octupole magnetic moment ? even in S1/2 and P172 states. The effect of ??0 existence in S1/2, P1/2 states is conditioned by the same reasons which cause the existence of electrical quadrupole moment in mesic atoms with J?0 in the same states: hyperfine interaction between the nucleus and negative ?-muon adds D3/2, D5/2... states to S1/2 term and P3/2, F5/2 etc. states allowed by the law of conservation of complete moment of F mesic atom and its projection M and possessing the same parity as the initial state-to P172 term

1987-07-04

17

Quadrupole magnet fringe field effect on the nonlinear shift of the betatron frequency  

International Nuclear Information System (INIS)

Analytic expressions for the amplitude-dependent betatron frequency shift driven by the quadrupole magnet fringe field have been obtained. The magnitude of the effect is compared with other sources of nonlinearity such as chromatic sextupoles, octupole errors of the main quadrupole magnetic field and kinematic terms. For the numerical example, the lattice of the e+e- collider VEhPP-4M was applied

2000-01-01

18

Experimental tests for stable octupole deformation in actinium-227  

International Nuclear Information System (INIS)

[en] The question of intrinsic reflection asymmetry or stable-octupole deformation in 227Ac was studied by the single-proton stripping reactions 226Ra(3He,d)227Ac with E/sub 3He/ = 30 MeV and 226Ra(?,t)227Ac with E/sub ?/ = 30 MeV and by measuring the magnetic moment of the first excited 3/2+ state at 27.38 keV by a differential perturbed angular correlation (DPAC) experiment. Theoretical differential cross sections were determined using calculated nuclear structure factors with and without octupole-deformed Woods-Saxon model wave functions. Theoretical values for the magnetic moments of the ground state and first excited state with and without octupole deformation were determined using calculated intrinsic g-factors from folded Yukawa model wave functions. The results of the proton-stripping cross sections are inconclusive. No how comparison of the measured values for the magnetic moment of the first excited state with a previous measurement for the ground state seems to support stable octupole deformation in 227Ac. Therefore, the energy ordering of orbitals and the magnetic moment results are consistent and they seem to support a stable-octupole deformed shape for the ground state parity doublet in 227Ac. Furthermore, the results are consistent with the branching ratio determination of the magnetic moment of the first excited state in 227Ac which is in agreement with the stable-octupole model prediction

1986-01-01

19

Magnetic field line Hamiltonian  

Energy Technology Data Exchange (ETDEWEB)

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

Boozer, A.H.

1985-02-01

20

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

 
 
 
 
21

Octupole coil configuration for the Tandem Mirror Experiment Upgrade (TMX-U)  

International Nuclear Information System (INIS)

The octupole plug concept offers the attractive possibility of reducing the length of the plug and transition sections in tandem mirror reactors. In the Tandem Mirror Experiment Upgrade (TMX-U), we are designing an octupole plug-transition that will replace our current quadrupole plug-transition. The reduction in length is made possible by the more nearly circular plasma cross section throughout the plug and transition sections. The principal physics of the design is the magnetohydrodynamic (MHD) stabilization of the core plasma in the plug by a hot electron ring in the mantle region surrounding the core. This hot electron mantle is MHD stable because of the good curvature field lines provided by the octupole. The positive radial pressure gradient in the hot electron mantle in turn stabilizes the core's plasma. Each octupole set consists of six coils replacing the transition and plug sets in the existing TMX-U experiment. The central cell coils will remain unchanged. Five of the coils for each of the new sets will be fabricated, while one, the 6-T mirror coil, will be reused from TMX-U. This paper will elaborate on the design configuration of the magnets. In particular, the configuration provides for adequate neutral beam lines-of-sight, and access for 0.615 MW of electron-cyclotron resonant heating (ECRH) on each end.

1985-01-01

22

Neutron star deformation due to multipolar magnetic fields  

Science.gov (United States)

Certain multiwavelength observations of neutron stars, such as intermittent radio emissions from rotation-powered pulsars beyond the pair-cascade death line, the pulse profile of the magnetar SGR 1900+14 after its 1998 August 27 giant flare and X-ray spectral features of PSR J0821-4300 and SGR 0418+5729, suggest that the magnetic fields of non-accreting neutron stars are not purely dipolar and may contain higher order multipoles. Here, we calculate the ellipticity of a non-barotropic neutron star with (i) a quadrupole poloidal-toroidal field, and (ii) a purely poloidal field containing arbitrary multipoles, deriving the relation between the ellipticity and the multipole amplitudes. We present, as a worked example, a purely poloidal field comprising dipole, quadrupole and octupole components. We show the correlation between field energy and ellipticity for each multipole, that the l = 4 multipole has the lowest energy, and that l = 5 has the lowest ellipticity. We show how a mixed multipolar field creates an observationally testable mismatch between the principal axes of inertia (to be inferred from gravitational wave data) and the magnetic inclination angle. Strong quadrupole and octupole components (with amplitudes ˜102 times higher than the dipole) in SGR 0418+5729 still yield ellipticity ˜10-8, consistent with current gravitational wave upper limits. The existence of higher multipoles in fast-rotating objects (e.g. newborn magnetars) has interesting implications for the braking law and hence phase tracking during coherent gravitational wave searches.

Mastrano, A.; Lasky, P. D.; Melatos, A.

2013-09-01

23

Biexciton in magnetic fields  

International Nuclear Information System (INIS)

The binding energy and structure of biexcitons in strong magnetic field is investigated using the stochastic variational method. The magnetic field confines the electrons and positrons in a small volume leading to Wigner-crystal like states of particles. (author)

2010-01-01

24

Magnetic field of pulsars  

Energy Technology Data Exchange (ETDEWEB)

The generation of the magnetic field in pulsars is considered. It is shown that the currents associated with drag of protons by rotating neutrons produce a mean magnetic field of order 10 to the 13th G. Within the star, this field has a vortex structure with density of order 3 x 10 to the 19th per sq cm. The almost homogeneous magnetic field produces a magnetic moment of order 10 to the 31st G cu cm. 8 references.

Sedrakian, D.M.

1983-01-01

25

Chromaticity dependence on octupole strength  

CERN Multimedia

The first measurements of the dependence of the chromaticity on the lattice octupole strength were performed at the LHC in a machine development session on Wednesday 20 June 2012. This chromaticity change is non negligible and needs to be taken into account when changing the octupole strength, e.g. for beam stabilization purposes. We report on the results of such measurements and later ones, along with some predictions and some first estimates of systematic horizontal and vertical misalignments of the octupoles.

Herr, W; Metral, E; Mounet, N; Papotti, G; Tomas Garcia, R; Wenninger, J

2012-01-01

26

Octupole shapes in heavy nuclei  

Energy Technology Data Exchange (ETDEWEB)

Theoretical calculations and measurements show the presence of strong octupole correlations in thecyround states and low-lying states of odd-mass and odd-odd nuclei in the RaPa region. Evidence for octupole correlations is provided by the observation of parity doublets and reductions in M1 matrix elements, decoupling parameters, and Coriolis matrix elements Involving high-j states. Enhancement of E1 transition rates has also been observed for some of the octupole deformed nuclei. The most convincing argument for octupole deformation is provided by the similarities of the reduced alpha decay rates to the two members of parity doublets.

Ahmad, I.

1994-08-01

27

Octupole shapes in heavy nuclei  

International Nuclear Information System (INIS)

[en] Theoretical calculations and measurements show the presence of strong octupole correlations in thecyround states and low-lying states of odd-mass and odd-odd nuclei in the RaPa region. Evidence for octupole correlations is provided by the observation of parity doublets and reductions in M1 matrix elements, decoupling parameters, and Coriolis matrix elements Involving high-j states. Enhancement of E1 transition rates has also been observed for some of the octupole deformed nuclei. The most convincing argument for octupole deformation is provided by the similarities of the reduced alpha decay rates to the two members of parity doublets

1994-01-01

28

Transformer generated magnetic fields  

International Nuclear Information System (INIS)

Magnetic fields produced by both small and large apparatus are being investigated for their possible relation to human health effects. A number of studies have been done in characterizing the magnetic field generated by transmission lines, household wiring and appliances. Two other major sources of magnetic fields are motors and transformers. The magnetic field generated by power transformers has not been studied extensively. The purpose of this paper is to experimentally quantify the magnetic field of a power transformer and compare it with calculated results obtained using one of the numerical techniques.

1996-01-01

29

Stellar magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

Strong evidence of magnetic fields is shown by white dwarves, chemically peculiar stars, and late-type dwarves. The magnetic data available, for CP stars agree with the oblique rotator model. The distribution of the magnetic axis inclination could be random or a mixture of low and high obliquities. The data are consistent with rotational braking on the main sequence and with field decay. Moreover, they show an anti-correlation between the magnetic field strength and the rotational velocity.

Didelon, P. (Observatoire de Strasbourg, 67 (France))

1984-01-01

30

Magnetic fields in galaxies  

CERN Document Server

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

31

A «tidal» magnetic field?  

Directory of Open Access Journals (Sweden)

Full Text Available t is shown that on the magnetization axis of a uniformly magnetized body of constant density the magnetic field intensity displays a «tidal» structure,i.e. the ratios among the differential magnetic field intensity in three orthogonal directions are the same as the ratios among the gravitational gradient tensor components pertaining to the same directions; it is also seen that the same characteristic ratios occur, both locally and non-locally, among the components of the magnetic field intensity and among the components of the gradient tensors of the two fields.

F. Bocchio

1997-01-01

32

Octupole effects in the lanthanides  

International Nuclear Information System (INIS)

Arrays of Anti-Compton Spectrometer enabled systematic investigations of octupole correlations in the neutron-rich lanthanides. The studies mostly confirm the theoretical expectations of moderate octupole deformation at medium spins in nuclei from this region but in some cases predictions deviate from the experiment. In cesium isotopes strong octupole effects are predicted but not observed and new measurements for 139Xe suggest octupole effects stronger than expected. Systematics of excitation energy of the 31 states excitations, updated in the present work for Xe isotopes, indicates the N=85 and Z=54 lines as borders for strong octupole correlations. Systematic of electric dipole moment, upgraded in the present work for Ca and Ce isotopes confirms the Z=54 limit and adds new information about local canceling of electric dipole moment at the N=90 neutron number.

1999-07-02

33

Multi-dimensional potential energy surfaces and non-axial octupole correlations in actinide and transfermium nuclei from relativistic mean field models  

CERN Document Server

We have developed multi-dimensional constrained covariant density functional theories (MDC-CDFT) for finite nuclei in which the shape degrees of freedom \\beta_{\\lambda\\mu} with even \\mu, e.g., \\beta_{20}, \\beta_{22}, \\beta_{30}, \\beta_{32}, \\beta_{40}, etc., can be described simultaneously. The functional can be one of the following four forms: the meson exchange or point-coupling nucleon interactions combined with the non-linear or density-dependent couplings. For the pp channel, either the BCS approach or the Bogoliubov transformation is implemented. The MDC-CDFTs with the BCS approach for the pairing (in the following labelled as MDC-RMF models with RMF standing for "relativistic mean field") have been applied to investigate multi-dimensional potential energy surfaces and the non-axial octupole $Y_{32}$-correlations in N=150 isotones. In this contribution we present briefly the formalism of MDC-RMF models and some results from these models. The potential energy surfaces with and without triaxial deformatio...

Lu, Bing-Nan; Zhao, En-Guang; Zhou, Shan-Gui

2013-01-01

34

Magnetic field generator  

Energy Technology Data Exchange (ETDEWEB)

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

Krienin, Frank (Shoreham, NY)

1990-01-01

35

Cosmological magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

Observations indicate that magnetic fields are associated with most structures in the universe. Upto now the origin of large scale primordial magnetic fields is an open problem. Two mechanisms in particular, taking place during inflation in the very early universe are reviewed.

Kunze, Kerstin E, E-mail: kkunze@usal.e [Departamento de Fisica Fundamental, Universidad de Salamanca, Plaza de la Merced s/n, 37008 Salamanca (Spain)

2009-10-01

36

Magnetic field on board  

International Nuclear Information System (INIS)

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

1995-01-01

37

Octupole Deformed Nuclei in the Actinide Region  

CERN Multimedia

% IS322 \\\\ \\\\ The aim of the present study is to investigate the limits of the $^{\\prime\\prime}$island$^{\\prime\\prime}$ of octupole deformation in the mass region A=225. It is of particular importance to demonstrate experimentally the sudden disappearance of the stable octupole deformation in the presence of a well developed quadrupole field. \\\\ \\\\In order to establish the upper border line the $\\beta$ decay chains of $^{227}$Rn $\\rightarrow$ $^{227}$Fr $\\rightarrow$ $^{227}$Ra and ~ $^{231}$Fr &$\\rightarrow$ $^{231}$Ra &$\\rightarrow$ $^{231}$Ac were studied at PSB-ISOLDE using advanced fast timing and $\\gamma$-ray spectroscopy techniques. The lifetimes of the excited states have been measured in the picosecond range using the time-delayed $\\beta

Thorsteinsen, T; Rubio barroso, B; Simpson, J; Gulda, K; Sanchez-vega, M; Cocks, J; Nybo, K; Garcia borge, M; Aas, A; Fogelberg, B; Honsi, J; Smith, G; Naumann, R; Grant, I

2002-01-01

38

Cosmological magnetic fields  

CERN Document Server

Magnetic fields are observed not only in stars, but in galaxies, clusters, and even high redshift Lyman-alpha systems. In principle, these fields could play an important role in structure formation and also affect the anisotropies in the cosmic microwave background radiation (CMB). The study of cosmological magnetic fields aims not only to quantify these effects on large-scale structure and the CMB, but also to answer one of the outstanding puzzles of modern cosmology: when and how do magnetic fields originate? They are either primordial, i.e. created before the onset of structure formation, or they are generated during the process of structure formation itself.

Maartens, R

2000-01-01

39

Construction and Operational Experience with a Superconducting Octupole Used to Trap Antihydrogen  

Energy Technology Data Exchange (ETDEWEB)

A superconducting octupole magnet has seen extensive service as part of the ALPHA experiment at CERN. ALPHA has trapped antihydrogen, a crucial step towards performing precision measurements of anti-atoms. The octupole was made at the Direct Wind facility by the Superconducting Magnet Division at Brookhaven National Laboratory. The magnet was wound with a six-around-one NbTi cable about 1 mm in diameter. It is about 300 mm long, with a radius of 25 mm and a peak field at the conductor of 4.04 T. Specific features of the magnet, including a minimal amount of material in the coil and coil ends with low multipole content, were advantageous to its use in ALPHA. The magnet was operated for six months a year for five years. During this time it underwent about 900 thermal cycles (between 4K and 100K). A novel operational feature is that during the course of data-taking the magnet was repeatedly shut off from its 950 A operating current. The magnet quenches during the shutoff, with a decay constant of 9 ms. Over the course of the five years, the magnet was deliberately quenched many thousands of times. It still performs well.

Wanderer P.; Escallier, J.; Marone, A.; Parker, B.

2011-09-06

40

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

 
 
 
 
41

Octupole instability in the heavy barium region  

Energy Technology Data Exchange (ETDEWEB)

Quasi-molecular rotational bands characterized by spin states of alternating parity connected by enhanced E1 transitions have recently been observed in several transitional nuclei around /sup 224/Th. The appearance of such bands can easily be understood by assuming the absence of intrinsic parity symmetry in these nuclei. Another likely region on the chart of nuclides to find octupole-unstable nuclei is the region of nuclei around /sup 146/Ba. In fact, in several Xe, Ba and Ce isotopes with n approximately equal to 88, calculations yield octupole-unstable ground states. The main goal of the present study was to calculate equilibrium deformations of doubly-even Xe, Ba, Ce, Nd, Sm and Gd nuclei with neutron numbers between 84 and 94. The method used was the Woods-Saxon-Bogolyubov cranking model method combined with the shell correction approach. The results of these calculations confirm previous expectations of octupole deformed mean fields at low and medium spins in Xe-Sm nuclei with neutron numbers around N = 86. Recent experimental data support theoretical results. 8 refs., 1 fig. (DWL)

Nazarewicz, W.; Leander, G.A.; Tabor, S.

1987-01-01

42

Interplay of field-induced multipoles in CeB{sub 6}  

Energy Technology Data Exchange (ETDEWEB)

We propose a theory of CeB{sub 6} in a magnetic field by extending and slightly modifying a previous paper. The antiferro-quadrupolar ordering induces dipoles and octupoles when the magnetic field is applied. The nature of those field-induced multipoles is studied by changing the direction of the field. It is shown that the contradiction between NMR and neutron diffraction is resolved by taking into account the influence of octupoles. Thus it is concluded that CeB{sub 6} is the first example in which the octupoles play a crucial role on the anomalous f-electron ordered phase. (author)

Shiina, Ryousuke; Shiba, Hiroyuki [Tokyo Inst. of Tech. (Japan). Dept. of Physics; Sakai, Osamu; Thalmeier, P.

1998-03-01

43

Magnetic Field Created by Tile Permanent Magnets  

Digital Repository Infrastructure Vision for European Research (DRIVER)

This paper presents the analytical calculation of the three components of the magnetic field created by tile permanent magnets whose magnetization is either radial or axial. The calculations are based on the coulombian model of permanent magnets. The magnetic field is directly calculated, without th...

Ravaud, Romain; Lemarquand, Guy; Lemarquand, Valérie

44

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 ...

Edda Lína Gunnarsdóttir 1988

45

Magnetic field dosimeter development  

Energy Technology Data Exchange (ETDEWEB)

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.

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

1980-09-01

46

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

47

Three-magnetic fields  

CERN Document Server

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

Koivisto, Tomi S

2011-01-01

48

Magnetic field coils  

Energy Technology Data Exchange (ETDEWEB)

The patent concerns magnetic field coils, particularly coils designed to produce a defined field in at least one volume, e.g. for NMR spectroscopy. The coils are formed by conductors located on a surface. The positions of the conductors are determined by the calculation of the continuous current density required on that surface to generate the required magnetic field on a specific target surface (or at specified points). The distribution of conductors that provides a good approximation to the current density is then calculated and the conductors are then wound onto the surface into the calculated positions. (U.K.).

Turner, R.; Mansfield, P.; Chapman, B.L.W.

1988-02-03

49

Magnetic field line reconnection  

Energy Technology Data Exchange (ETDEWEB)

The term 'magnetic field line reconnection' has arisen in the physics of rarefied plasmas with very high conductivity. When such a plasma is in motion, the remarkable property of field line 'freezing in' of the plasma manifests itself. However, situations sometimes occur in real plasma motion where this condition is violated. The process of reconnection results in a marked change in the field line topology and is accompanied by the formation of current layers and the conversion of magnetic energy into kinetic and thermal plasma energies. Magnetic field line reconnection plays a key role in many processes in the near-Earth, space and laboratory fusion plasmas.

Kadomtsev, B.B.

1987-02-01

50

Dipole and octupole pairs in deformed actinide nuclei  

Science.gov (United States)

The structure of deformed actinide nuclei is studied in terms of an intrinsic hamiltonian containing an octupole mean field in addition to a quadrupole field (Nilsson potential). It is shown that there is a significant amount of the collective dipole (1-) nucleon pair in the wave function of low-lying states, and that the dipole mode, for instance the dipole boson, has to be included in the description of such nuclei as well as the octupole one. The author acknowledges Professor A. Arima, Dr. N. Yoshida, Dr. N. Yoshinaga and Dr. M. Sugita for valuable discussions.

Otsuka, Takaharu

1986-12-01

51

ISR Radial Field Magnet  

CERN Document Server

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

52

Magnetic Fields in Galaxies  

Science.gov (United States)

Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized emission traces turbulent fields which are strongest in spiral arms and bars (20-30 ?G) and in central starburst regions (50-100 ?G). Such fields are dynamically important, e.g. they can drive gas inflows in central regions. Polarized emission traces ordered fields which can be regular or anisotropic random, generated from isotropic random fields by compression or shear. The strongest ordered fields of 10-15 ?G strength are generally found in interarm regions and follow the orientation of adjacent gas spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions of starburst galaxies. Faraday rotation measures (RM) of the diffuse polarized radio emission from the disks of several spiral galaxies reveal large-scale patterns, which are signatures of regular fields generated by a mean-field dynamo. However, in most spiral galaxies observed so far the field structure is more complicated. Ordered fields in interacting galaxies have asymmetric distributions and are an excellent tracer of past interactions between galaxies or with the intergalactic medium. Ordered magnetic fields are also observed in radio halos around edge-on galaxies, out to large distances from the plane, with X-shaped patterns. Future observations of polarized emission at high frequencies, with the EVLA, the SKA and its precursors, will trace galactic magnetic fields in unprecedented detail. Low-frequency telescopes (e.g. LOFAR and MWA) are ideal to search for diffuse emission and small RMs from weak interstellar and intergalactic fields.

Beck, Rainer

2012-05-01

53

Cosmic magnetic fields  

CERN Document Server

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

54

Nuclear magnetic resonance and earth magnetic field  

International Nuclear Information System (INIS)

[en] 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.)

1998-01-01

55

The earth's magnetic field  

International Nuclear Information System (INIS)

[en] 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

56

The Heliospheric Magnetic Field  

Science.gov (United States)

The Heliospheric Magnetic Field (HMF) is the physical framework in which energetic particles and cosmic rays propagate. Changes in the large scale structure of the magnetic field lead to short- and long term changes in cosmic ray intensities, in particular in anti-phase with solar activity. The origin of the HMF in the corona is well understood and inner heliospheric observations can generally be linked to their coronal sources. The structure of heliospheric magnetic polarities and the heliospheric current sheet separating the dominant solar polarities are reviewed here over longer than a solar cycle, using the three dimensional heliospheric observations by Ulysses. The dynamics of the HMF around solar minimum activity is reviewed and the development of stream interaction regions following the stable flow patterns of fast and slow solar wind in the inner heliosphere is described. The complex dynamics that affects the evolution of the stream interaction regions leads to a more chaotic structure of the HMF in the outer heliosphere is described and discussed on the basis of the Voyager observations. Around solar maximum, solar activity is dominated by frequent transients, resulting in the interplanetary counterparts of Coronal Mass Ejections (ICMEs). These produce a complex aperiodic pattern of structures in the inner heliosphere, at all heliolatitudes. These structures continue to interact and evolve as they travel to the outer heliosphere. However, linking the observations in the inner and outer heliospheres is possible in the case of the largest solar transients that, despite their evolutions, remain recognizably large structures and lead to the formation of Merged Interaction Regions (MIRs) that may well form a quasi-spherical, "global" shell of enhanced magnetic fields around the Sun at large distances. For the transport of energetic particles and cosmic rays, the fluctuations in the magnetic field and their description in alternative turbulent models remains a very important research topic. These are also briefly reviewed in this paper.

Balogh, André; Erdõs, Géza

2013-06-01

57

Global systematics of octupole excitations in even-even nuclei  

Science.gov (United States)

We present a computational methodology for a theory of the lowest axially symmetric octupole excitations applicable to all even-even nuclei beyond the lightest. The theory is the well-known generator-coordinate extension (GCM) of the Hartree-Fock-Bogoliubov (HFB) self-consistent mean field theory. We use the discrete-basis Hill-Wheeler (HW) method to compute the wave functions with an interaction from the Gogny family of Hamiltonians. Comparing to the compiled experimental data on octupole excitations, we find that the performance of the theory depends on the deformation characteristics of the nucleus. For nondeformed nuclei, the theory reproduces the energies to about ±20% apart from an overall scale factor of ?1.6. The performance is somewhat poorer for (quadrupole) deformed nuclei, and for both together the dispersion of the scaled energies about the experimental values is about ±25%. This compares favorably with the performance of similar theories of the quadrupole excitations. Nuclei having static octupole deformations in HFB theory form a special category. These nuclei have the smallest measured octupole excitation energies as well as the smallest predicted energies. However, in these cases the energies are seriously underpredicted by the theory. We find that a simple two-configuration approximation, the minimization after projection (MAP) method, is almost as accurate as the full HW treatment, provided that the octupole-deformed nuclei are omitted from the comparison. This article is accompanied by a tabulation of the predicted octupole excitations for 818 nuclei extending from drip-line to drip-line, computed with several variants of the Gogny interaction.

Robledo, L. M.; Bertsch, G. F.

2011-11-01

58

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

59

The LHC Magnetic Field Model  

CERN Document Server

The compensation of the field changes during the beam injection and acceleration in the LHC requires an accurate forecast and an active control of the magnetic field in the accelerator. The LHC Magnetic Field Model is the core of this magnetic prediction system. The model will provide the desired field components at a given time, magnet operating current, magnet ramp rate, magnet temperature and magnet powering history to the required precision. The model is based on the identification and physical decomposition of the effects that contribute to the total field in the magnet aperture of the LHC dipoles. Each effect is quantified using data obtained from series measurements, and modeled theoretically or empirically depending on the complexity of the physical phenomena involved. This paper presents the developments of the new finely tuned magnetic field model and evaluates its accuracy and predictive capabilities over a sector of the machine.

Sammut, Nicholas J; Micallef, Joseph

2005-01-01

60

Low field magnetic resonance imaging  

Energy Technology Data Exchange (ETDEWEB)

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

 
 
 
 
61

Magnetization reversal in ultrashort magnetic field pulses  

Science.gov (United States)

We report the switching properties of a thin magnetic film subject to an ultrashort, laterally localized magnetic field pulse, obtained by numerical investigations. The magnetization distribution in the film is calculated on a grid assuming Stoner-like coherent rotation within the grid square size. Perpendicularly and in-plane magnetized films exhibit a magnetization reversal due to a 4ps magnetic field pulse. Outside the central region the pulse duration is short compared to the precession period. In this area the evolution of the magnetization during the field pulse does not depend strongly on magnetic damping and/or pulse shape. However, the final magnetization distribution is affected by the magnetic damping. Although the pulse duration is short compared to the precession period, the time needed for the relaxation of the magnetization to the equilibrium state is rather large. The influence of the different magnetic anisotropy contributions and the magnetic damping parameter enters into the magnetization reversal process. Comparing the case of perpendicular anisotropy with different kinds of in-plane anisotropies, a principal difference is found due to the symmetry of the shape anisotropy with respect to the anisotropy in question.

Bauer, M.; Lopusnik, R.; Fassbender, J.; Hillebrands, B.

2000-08-01

62

Octupole deformation properties of the Barcelona-Catania-Paris energy density functionals  

International Nuclear Information System (INIS)

We discuss the octupole deformation properties of the recently proposed Barcelona-Catania-Paris (BCP) energy density functionals for two sets of isotopes, those of radium and barium, in which it is believed that octupole deformation plays a role in the description of the ground state. The analysis is carried out in the mean field framework (Hartree-Fock-Bogoliubov approximation) by using the axially symmetric octupole moment as a constraint. The main ingredients entering the octupole collective Hamiltonian are evaluated and the lowest-lying octupole eigenstates are obtained. In this way we restore, in an approximate way, the parity symmetry spontaneously broken by the mean field and also incorporate octupole fluctuations around the ground-state solution. For each isotope the energy of the lowest lying 1- state and the B(E1) and B(E3) transition probabilities have been computed and compared to both the experimental data and the results obtained in the same framework with the Gogny D1S interaction, which are used here as a well-established benchmark. Finally, the octupolarity of the configurations involved in the way down to fission of 240Pu, which is strongly connected to the asymmetric fragment mass distribution, is studied. We confirm with this thorough study the suitability of the BCP functionals to describe octupole-related phenomena.

2010-01-01

63

The Galactic Magnetic Field  

CERN Document Server

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

64

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

65

AGS correction quadrupoles and octupoles  

International Nuclear Information System (INIS)

[en] A pole-face design is presented for a set of correction quadrupoles and a set of correction octupoles required in the Brookhaven AGS. The pole-face design consists of a circular pole which is terminated by radial lines tangent to the circle. The radius of the circle is chosen to cause the lowest undesired multipole present to vanish. (U.S.)

1975-01-01

66

Limits for primordial magnetic fields  

CERN Multimedia

A possible explanation for the origin of the magnetic fields observed today in matter structures is that they were generated in the primordial universe. After briefly revising the model of a primordial stochastic magnetic field and sketching the main features of its time evolution in the primordial plasma, we illustrate the current upper bounds on the magnetic field amplitude and spectral index from Cosmic Microwave Background observations and gravitational wave production. We conclude that a primordial magnetic field generated by a non-causal process such as inflation with a red spectrum seems to be favoured as a seed for the magnetic fields observed today in structures.

Caprini, Chiara

2011-01-01

67

Nanosystem magnetization via magnetic field rotation  

CERN Multimedia

We study the magnetization in systems of uniaxial ferromagnetic nanoparticles which is induced by the rotating magnetic field and enhanced by thermal fluctuations. We clarify the nature of this effect, develop an effective method for its description, calculate within this method the frequency dependence of the magnetization, and reveal the role of the magnetic dipolar interaction. The feasibility and desirability of experimental investigation of this phenomenon are argued.

Denisov, S I; Hänggi, P

2006-01-01

68

Fast superconducting magnetic field switch  

Energy Technology Data Exchange (ETDEWEB)

The superconducting magnetic switch or fast kicker magnet is employed with an electron stream or a bunch of electrons to rapidly change the direction of flow of the electron stream or bunch of electrons. The apparatus employs a beam tube which is coated with a film of superconducting material. The tube is cooled to a temperature below the superconducting transition temperature and is subjected to a constant magnetic field which is produced by an external dc magnet. The magnetic field produced by the dc magnet is less than the critical field for the superconducting material, thus, creating a Meissner Effect condition. A controllable fast electromagnet is used to provide a magnetic field which supplements that of the dc magnet so that when the fast magnet is energized the combined magnetic field is now greater than the critical field and the superconducting material returns to its normal state allowing the magnetic field to penetrate the tube. This produces an internal field which effects the direction of motion and of the electron stream or electron bunch. The switch can also operate as a switching mechanism for charged particles. Magnetic switches and particularly fast kicker magnets are used in the accelerator industry to quickly deflect particle beams into and out of various transport lines, storage rings, dumps, and specifically to differentially route individual bunches of particles from a train of bunches which are injected or ejected from a given ring.

Goren, Y.; Mahale, N.K.

1995-12-31

69

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

70

Analytical calculation of field error due to radial coil distortions of the LHC low-beta quadrupole magnets  

CERN Document Server

The magnetic field of superconducting accelerator magnets is mainly determined by the current distribution. A distortion of current distribution induces unexpected multipole fields. A simple analytical field calculation with radial distortions, which are described by Fourier series, is developed. Analytical equations which give the correlation between the deformation patterns and the multipole field components are found. The equations are applied to the measurement results for the LHC-MQXA magnets developed by KEK. The radial distortions which introduces normal octupole and twelvepole fields are estimated. The direction of distortions follows the magnet mechanical tendency. The amplitude of those is within the construction errors. A numerical computation applying the distortions to the real cross section is performed. The computation results prove that the analytical equations give the good approximation. (7 refs).

Sugita, K; Nakamoto, T; Ohuchi, N; Hirano, H; Shintomi, T; Tsuchiya, K; Yamamoto, A

2002-01-01

71

Leptogenesis and Primordial Magnetic Fields  

CERN Multimedia

The anomalous conversion of leptons into baryons during leptogenesis is shown to produce a right-handed helical magnetic field; in contrast, the magnetic field produced during electroweak baryogenesis is known to be left-handed. If the cosmological medium is turbulent, the magnetic field evolves to have a present day coherence scale and field strength that are of astrophysical interest. Observations of the amplitude, coherence scale, and helicity of the intergalactic magnetic field promise to provide a powerful probe of physics beyond the Standard Model and the very early universe.

Long, Andrew J; Vachaspati, Tanmay

2013-01-01

72

Fast superconducting magnetic field switch  

Energy Technology Data Exchange (ETDEWEB)

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

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

1996-01-01

73

Magnetic Propeller for Uniform Magnetic Field Levitation  

CERN Multimedia

Three new approaches to generating thrust in uniform magnetic fields are proposed. The first direction is based on employing Lorentz force acting on partial magnetically shielded 8-shaped loop with current in external magnetic field, whereby a net force rather than a torque origins. Another approach, called a Virtual Wire System, is based on creating a magnetic field having an energetic symmetry (a virtual wire), with further superposition of external field. The external field breaks the symmetry causing origination of a net force. Unlike a wire with current, having radial energetic symmetry, the symmetry of the Virtual Wire System is closer to an axial wire. The third approach refers to the first two. It is based on creation of developed surface system, comprising the elements of the first two types. The developed surface approach is a way to drastically increase a thrust-to-weight ratio. The conducted experiments have confirmed feasibility of the proposed approaches.

Krinker, Mark

2008-01-01

74

Octupole correlations in the heavy elements  

Energy Technology Data Exchange (ETDEWEB)

The effects of octupole correlations on the nuclear structure of the heavy elements are discussed. The cluster model description of the heavy elements is analyzed. The relevance of 2/sup 6/-pole deformation and fast El transitions to an octupole model is considered. 30 refs., 21 figs., 1 tab.

Chasman, R.R.

1986-01-01

75

Reconnection of Magnetic Fields  

Science.gov (United States)

Preface; Part I. Introduction: 1.1 The Sun E. R. Priest; 1.2 Earth's magnetosphere J. Birn; Part II. Basic Theory of MHD Reconnection: 2.1 Classical theory of two-dimensional reconnection T. G. Forbes; 2.2 Fundamental concepts G. Hornig; 2.3 Three-dimensional reconnection in the absence of magnetic null points G. Hornig; 2.4 Three-dimensional reconnection at magnetic null points D. Pontin; 2.5 Three-dimensional flux tube reconnection M. Linton; Part III. Basic Theory of Collisionless Reconnection: 3.1 Fundamentals of collisionless reconnection J. Drake; 3.2 Diffusion region physics M. Hesse; 3.3 Onset of magnetic reconnection P. Pritchett; 3.4 Hall-MHD reconnection A. Bhattacharjee and J. Dorelli; 3.5 Role of current-aligned instabilities J. Büchner and W. Daughton; 3.6 Nonthermal particle acceleration M. Hoshino; Part IV. Reconnection in the Magnetosphere: 4.1 Reconnection at the magnetopause: concepts and models J. G. Dorelli and A. Bhattacharjee; 4.2 Observations of magnetopause reconnection K.-H. Trattner; 4.3 On the stability of the magnetotail K. Schindler; 4.4 Simulations of reconnection in the magnetotail J. Birn; 4.5 Observations of tail reconnection W. Baumjohann and R. Nakamura; 4.6 Remote sensing of reconnection M. Freeman; Part V. Reconnection in the Sun's Atmosphere: 5.1 Coronal heating E. R. Priest; 5.2 Separator reconnection D. Longcope; 5.3 Pinching of coronal fields V. Titov; 5.4 Numerical experiments on coronal heating K. Galsgaard; 5.5 Solar flares K. Kusano; 5.6 Particle acceleration in flares: theory T. Neukirch; 5.7 Fast particles in flares: observations L. Fletcher; 6. Open problems J. Birn and E. R. Priest; Bibliography; Index.

Birn, J.; Priest, E. R.

2007-01-01

76

Octupole collectivity in the Sm isotopes  

International Nuclear Information System (INIS)

Microscopic models suggest the occurrence of strong octupole correlations in nuclei with N?88. To examine the signatures of octupole correlations in this region, the spdf Interacting Boson Approximation (IBA) Model is applied to the Sm isotopes with N = 86 - 92. The effects of including multiple negative parity bosons in the basis are compared to more standard one negative parity boson calculations and are analyzed in terms of signatures for strong octupole correlations. It is found that multiple negative parity bosons are needed to describe properties at medium spin. Bands with strong octupole correlations (multiple negative parity bosons) become yrast at medium spin in 148,150Sm. This region shares some similarities with the light actinides, where strong octupole correlations were also found at medium spin. (orig.)

2005-01-01

77

Octupole collectivity in the Sm isotopes  

International Nuclear Information System (INIS)

Microscopic models suggest the occurrence of strong octupole correlations in nuclei with N?88. To examine the signatures of octupole correlations in this region, the spdf interacting boson approximation model is applied to Sm isotopes with N=86-92. The effects of including multiple negative-parity bosons in this basis are compared with more standard one negative-parity boson calculations and are analyzed in terms of signatures for strong octupole correlations. It is found that multiple negative-parity bosons are needed to describe properties at medium spin. Bands with strong octupole correlations (multiple negative-parity bosons) become yrast at medium spin in 148,150Sm. This region shares some similarities with the light actinides, where strong octupole correlations were also found at medium spin

2005-01-01

78

Flexible magnetic field therapy mat  

UK PubMed Central (United Kingdom)

Devices for performing magnetic field therapy employ rigid field excitation coils for attachment or application onto the body of a patient, and this partially delimits the range of action of the therapeutically active field lines. The novel, flexible magnetic field therapy mat is to permit optimum utilization of the field in the entire body region coupled with extreme comfort on use. In a double-walled textile or plastic mat (1) which can surround a human body from the armpits to the thighs, coils (2) which are wound onto flat iron cores and are connected in series are excited via an adjustable direct current pulse generator for periodic, polarised formation of magnetic fields. Direct application of all coil rods on the body and the "coil core position" of the patient in the mat result in an optimum therapeutic effect of all the force lines of the therapy field. Magnetic field therapy in the ELF field.

KASCHIK GERHARD

79

Charge in Magnetic Field Model  

Science.gov (United States)

The EJS Charge In B-Field model allows the user to simulate moving charged particles in two identical magnetic field regions separated by a zero magnetic field gap. The Charge in B Field Model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ntnu_em_ChargeInBField.jar file will run the program if Java is installed.

Hwang, Fu-Kwun

2009-05-19

80

The non-dipolar magnetic fields of accreting T Tauri stars  

CERN Document Server

Models of magnetospheric accretion on to classical T Tauri stars often assume that stellar magnetic fields are simple dipoles. Recently published surface magnetograms of BP Tau and V2129 Oph have shown, however, that their fields are more complex. The magnetic field of V2129 Oph was found to be predominantly octupolar. For BP Tau the magnetic energy was shared mainly between the dipole and octupole field components, with the dipole component being almost four times as strong as that of V2129 Oph. From the published surface maps of the photospheric magnetic fields we extrapolate the coronal fields of both stars, and compare the resulting field structures with that of a dipole. We consider different models where the disc is truncated at, or well-within, the Keplerian corotation radius. We find that although the structure of the surface magnetic field is particularly complex for both stars, the geometry of the larger scale field, along which accretion is occurring, is somewhat simpler. However, the larger scale ...

Gregory, S G; Donati, J -F; Jardine, M

2008-01-01

 
 
 
 
81

Measurements of magnetic field alignment  

Energy Technology Data Exchange (ETDEWEB)

The procedure for installing Superconducting Super Collider (SSC) dipoles in their respective cryostats involves aligning the average direction of their field with the vertical to an accuracy of 0.5 mrad. The equipment developed for carrying on these measurements is described and the measurements performed on the first few prototypes SSC magnets are presented. The field angle as a function of position in these 16.6 m long magnets is a characteristic of the individual magnet with possible feedback information to its manufacturing procedure. A comparison of this vertical alignment characteristic with a magnetic field intensity (by NMR) characteristic for one of the prototypes is also presented. 5 refs., 7 figs.

Kuchnir, M.; Schmidt, E.E.

1987-11-06

82

Origin of cosmic magnetic fields.  

UK PubMed Central (United Kingdom)

We calculate, in the free Maxwell theory, the renormalized quantum vacuum expectation value of the two-point magnetic correlation function in de Sitter inflation. We find that quantum magnetic fluctuations remain constant during inflation instead of being washed out adiabatically, as usually assumed in the literature. The quantum-to-classical transition of super-Hubble magnetic modes during inflation allow us to treat the magnetic field classically after reheating, when it is coupled to the primeval plasma. The actual magnetic field is scale independent and has an intensity of few×10(-12)??G if the energy scale of inflation is few×10(16)??GeV. Such a field accounts for galactic and galaxy cluster magnetic fields.

Campanelli L

2013-08-01

83

Origin of cosmic magnetic fields.  

UK PubMed Central (United Kingdom)

We calculate, in the free Maxwell theory, the renormalized quantum vacuum expectation value of the two-point magnetic correlation function in de Sitter inflation. We find that quantum magnetic fluctuations remain constant during inflation instead of being washed out adiabatically, as usually assumed in the literature. The quantum-to-classical transition of super-Hubble magnetic modes during inflation allow us to treat the magnetic field classically after reheating, when it is coupled to the primeval plasma. The actual magnetic field is scale independent and has an intensity of few×10^{-12}??G if the energy scale of inflation is few×10^{16}??GeV. Such a field accounts for galactic and galaxy cluster magnetic fields.

Campanelli L

2013-08-01

84

Origin of Cosmic Magnetic Fields  

Science.gov (United States)

We calculate, in the free Maxwell theory, the renormalized quantum vacuum expectation value of the two-point magnetic correlation function in de Sitter inflation. We find that quantum magnetic fluctuations remain constant during inflation instead of being washed out adiabatically, as usually assumed in the literature. The quantum-to-classical transition of super-Hubble magnetic modes during inflation allow us to treat the magnetic field classically after reheating, when it is coupled to the primeval plasma. The actual magnetic field is scale independent and has an intensity of few×10-12G if the energy scale of inflation is few×1016GeV. Such a field accounts for galactic and galaxy cluster magnetic fields.

Campanelli, Leonardo

2013-08-01

85

Interplanetary electric and magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

A kinematic model of the stationary electromagnetic fields in interplanetary space with finite conductivity is considered. The electrodynamic problem is solved for a medium with uniform conductivity and radial plasma outflow from a spherical source. Simple analytical formulae are obtained for electric and magnetic fields, currents and charges in the case of a uniformly-magnetized rotating sphere.

Alexeev, I.I.; Kropotkin, A.P.; Veselovsky, I.S. (Moskovskij Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Inst. Yadernoj Fiziki)

1982-08-01

86

Magnetic fields in O stars  

CERN Multimedia

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

Naze, Yael

2013-01-01

87

Nonlocal pseudopotentials and magnetic fields  

CERN Multimedia

We show how to describe the coupling of electrons to non-uniform magnetic fields in the framework of the widely used norm-conserving pseudopotential appro ximation for electronic structure calculations. Our derivation applies to magnetic fields that are smooth on the scale of the core region. The method is validated by application to the calculation of the magnetic susceptibility of molecules. Our results are compared with high quality all electron quantum chemical results, and another recently proposed formalism.

Pickard, C J; Pickard, Chris J.; Mauri, Francesco

2003-01-01

88

Octupole vibrations at high angular momenta  

International Nuclear Information System (INIS)

Properties of octupole vibrations in rapidly rotating nuclei are discussed. Microscopic RPA calculations based on the cranked shell model are performed to investigate the interplay between rotation and vibration. The ability of this model to describe the properties of collective vibrations built on the ground bands in rare-earth and actinide nuclei is demonstrated at high angular momentum. The octupole vibrational states in even-even superdeformed Hg nuclei are also predicted and compared with available experimental data. A new interpretation of the observed excited superdeformed bands invoking these octupole bands is proposed. (author). 20 refs, 6 figs, 1 tab

1995-09-02

89

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

90

Primordial Magnetic Fields in Cosmology  

CERN Multimedia

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 two ways, analytically and via static realisations. We construct the power spectra, some of which we present for the first time. At the one- and three-point level we find significant intrinsic non-Gaussianities. Finally we turn to the observable impacts a primordial magnetic field. Assuming coherence, the statistics of the source can be mapped onto the CMB in a simple manner. We demonstrate that our approach is valid by reproducing the signals for Gaussian power law fields on the microwave sky. [ABRIDGED

Brown, Iain A

2008-01-01

91

Preflare magnetic and velocity fields  

International Nuclear Information System (INIS)

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

1983-01-24

92

Low-magnetic-field magnetars  

CERN Document Server

It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these `magnetar candidates' exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (~4.4E+13 G). The recent discovery of fully-qualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarize the observational status of the low-magnetic-field magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.

Turolla, R

2013-01-01

93

Magnetic fields and scintillator performance  

Energy Technology Data Exchange (ETDEWEB)

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.

Green, D.; Ronzhin, A. [Fermi National Accelerator Lab., Batavia, IL (United States); Hagopian, V. [Florida State Univ., Tallahasse, FL (United States)

1995-06-01

94

Neutron scattering in magnetic fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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. P...

Koehler, W.C.

95

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

1984-01-01

96

Magnetic field structure of Mercury  

Science.gov (United States)

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

Hiremath, K. M.

2012-04-01

97

Field of the Magnetic Monopole  

CERN Multimedia

This paper shows that based upon the Helmholtz decomposition theorem the field of a stationary magnetic monopole, assuming it exists, cannot be represented by a vector potential. Persisting to use vector potential in monopole representation violates fundamentals of mathematics. The importance of this finding is that the vector potential representation was crucial to the original prediction of the quantized value for a magnetic charge.

Hadjesfandiari, A R

2007-01-01

98

Magnetic field processing of polymers  

Energy Technology Data Exchange (ETDEWEB)

Hydroxypropyl cellulose (HPC) of degree of substitution three and average molecular weight of 100,000 was processed in a magnetic field of 1.2T. Films of HPC were cast from water, methanol, ethyl methyl ketone and 1,1,2,2-tetrachloroethane solutions in a magnetic field using {open_quotes}static{close_quotes} and {open_quotes}dynamic{close_quotes} casting techniques. The dynamic casting technique involved a shear radiant effect in addition to the magnetic field effect during the formation of the film. The processed films were evaluated for tensile strength, elastic modules, microhardness, thermal properties and molecular chain alignment by wide angle x-ray diffraction and polarized infrared. The films cast in a magnetic field, using the {open_quotes}dynamic{close_quotes} casting technique, showed no increase in the elastic modulus, a 106% increase in the tensile strength and a 21% increase in the microhardness and were dichroic.

Liepins, R.; Jahn, R.K.; Elliott, N.E.; Hubbard, K.M. [Los Alamos National Laboratory, NM (United States)

1993-12-31

99

Stellar and interstellar magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

It is noted that the stellar and interstellar magnetic fields are revealed directly by the splitting of the spectral lines caused by the Zeeman effect and indirectly by the polarization of radiation. The methods used in obtaining information on the interstellar magnetic field are discussed. These are (1) the optical polarization of starlight, (2) the rotation measure of radio sources, (3) the Zeeman effect at the 21-cm line, (4) the pulsar rotation measure, combined with the pulsar dispersion measure, and (5) radio polarization data on the continuum emission from the galaxy. Attention is also given to methods for measuring the stellar fields. The characteristics of the magnetic fields in chemically peculiar stars are discussed, as are magnetic white dwarfs and neutron stars.

Hack, M.

1982-01-01

100

NMR in pulsed magnetic fields  

International Nuclear Information System (INIS)

The first observation of NMR in the pulsed high magnetic field at the Hochfeldmagnetlabor Dresden (HLD), Forschungszentrum Dresden-Rossendorf (FZD) is reported. The new spectrometer that operates at up to 3.0 GHz is described, as well as its implementation in the pulsed field facility. Free induction decays and spin echo experiments on 1H and 63,65Cu in various magnets are described and discussed in terms of sensitivity and resolution.

2010-01-01

 
 
 
 
101

Theorem on magnet fringe field  

Energy Technology Data Exchange (ETDEWEB)

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 (b{sub n}) and skew (a{sub n}) multipoles, B{sub y} + iB{sub x} = {summation}(b{sub n} + ia{sub n})(x + iy){sup 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 B}L {equivalent_to} {integral} B(x,y,z)dz where the integration range starts well before the magnet and ends well after it. For {bar a}{sub n}, {bar b}{sub n}, {bar B}{sub x}, and {bar B}{sub y} 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 {vert_bar}{Delta}p{sub {proportional_to}}{vert_bar}, the transverse deflection produced by the ion-gitudinal component of the fringe field at one magnet end relative to {vert_bar}{Delta}p{sub 0}{vert_bar}, 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 B{sub x} from the vicinity of one magnet end since, along a path parallel to the magnet axis such as path BC.

Wei, Jie [Brookhaven National Lab., Upton, NY (United States); Talman, R. [Cornell Univ., Ithaca, NY (United States). Lab. of Nuclear Studies

1995-12-31

102

EARTH MAGNETIC-FIELD AUGMENTERS  

UK PubMed Central (United Kingdom)

Magnetic-field-augmented beds (10, 246, 258, 366, 388, 406, 424, 426), mattresses (330, 352), box springs (408), seating furniture (490), desks (542, 572), carrells (278, 514) rooms (168, 202, 216A, 216B), and buildings (156, 164, 192, 230, 472) include magnetic-field augmenters (18, 40, 46, 56, 154, 162, 172, 198, 210, 224A, 224B, 230, 254, 260, 282, 308, 334, 362, 380, 386, 412, 430, 442, 446, 456, 476, 492, 524, 550) that, when connected to a source (70) of electrical power, provide a healthful magnetic field for entire bodies of human beings or other living things in living spaces. In still another embodiment, a magnetic-field augmenter (444) is hung on a wall (446), and in another embodiment, a magnetic-field augmenter (456) is arranged on a floor (456) around seating furniture (462). Included among the various types of magnetic-field augmenters are bundled augmenter coils (390, 414, 476), dual-axis augmenters (492, 550), open-sided augmenters (524, 550), and dual-axis open-sided augmenters (550). An electrical-circuit protector (594) protects against loose connections and shorts.

MILLER Wendell E.; SOUTH Robert E.; SOUTH Michael R.

103

Magnetic field properties of the ISABELLE Project superconducting dipole magnets  

International Nuclear Information System (INIS)

A series of prototype superconducting dipole magnets have been constructed and tested as part of the ISABELLE Project research and development program. Results of magnetic field measurements are presented with emphasis placed on the DC and AC components of the main field. Magnetization and the effects of the magnetic fields at the ends of the magnet are displayed

1981-03-13

104

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

105

Measurements of magnetic field alignment  

International Nuclear Information System (INIS)

[en] The procedure for installing Superconducting Super Collider (SSC) dipoles in their respective cryostats involves aligning the average direction of their field with the vertical to an accuracy of 0.5 mrad. The equipment developed for carrying on these measurements is described and the measurements performed on the first few prototypes SSC magnets are presented. The field angle as a function of position in these 16.6 m long magnets is a characteristic of the individual magnet with possible feedback information to its manufacturing procedure. A comparison of this vertical alignment characteristic with a magnetic field intensity (by NMR) characteristic for one of the prototypes is also presented. 5 refs., 7 figs

1987-01-01

106

Reconnection in magnetic field lines  

International Nuclear Information System (INIS)

Magnetic surfaces are described for MHD equilibrium plasma with central hole plasma current density, confined in large aspect-ratio tokamaks, perturbed by external helical windings. The integrable case is first considered, where reconnection phenomenon is described for the field lines. A toroidal correction causes the integrability loss, leading to the onset of chaotic field lines. (author). 7 refs, 4 figs

1994-11-04

107

Magnetic field distributions of superconducting MRI magnet in insert dewar  

Energy Technology Data Exchange (ETDEWEB)

This paper describes the test results of magnetic field distributions of superconducting MRI magnet in an insert dewar. To get a very high homogeneous magnetic field, various shim coils are installed besides the main magnet. The operating currents of each shim coils are obtained from the exact measurements of the magnetic field. In this paper, we report the test results of the magnetic field distribution measurements with various shim coils. (author). 2 refs., 8 figs., 1 tab.

Jin, H.B.; Oh, B.H.; Kwon, Y.G.; Oh, S.S.; Cho, J.W.; Ha, D.W.; Lee, E.Y.; Ryu, K.W.; Ryu, K.S.; Hahn, I.Y. [Korea Electrotechonology Research Institute (Korea, Republic of); Nah, W. [Sungkwunkwan University (Korea, Republic of)

1995-07-01

108

MAGNETIC FIELD MEASUREMENTS FOR FAST-CHANGING MAGNETIC FIELDS  

International Nuclear Information System (INIS)

Several recent applications for fast ramped magnets have been found that require rapid measurement of the field quality during the ramp. (In one instance, accelerator dipoles will be ramped at 1 T/sec, with measurements needed to the accuracy typically required for accelerators.) We have built and tested a new type of magnetic field measuring system to meet this need. The system consists of 16 stationary pickup windings mounted on a cylinder. The signals induced in the windings in a changing magnetic field are sampled and analyzed to obtain the field harmonics. To minimize costs, printed circuit boards were used for the pickup windings and a combination of amplifiers and ADPs used for the voltage readout system. New software was developed for the analysis. Magnetic field measurements of a model dipole developed for the SIS200 accelerator at GSI are presented. The measurements are needed to insure that eddy currents induced by the fast ramps do not impact the field quality needed for successful accelerator operation.

2004-01-01

109

MAGNETIC FIELD MEASUREMENTS FOR FAST-CHANGING MAGNETIC FIELDS.  

Energy Technology Data Exchange (ETDEWEB)

Several recent applications for fast ramped magnets have been found that require rapid measurement of the field quality during the ramp. (In one instance, accelerator dipoles will be ramped at 1 T/sec, with measurements needed to the accuracy typically required for accelerators.) We have built and tested a new type of magnetic field measuring system to meet this need. The system consists of 16 stationary pickup windings mounted on a cylinder. The signals induced in the windings in a changing magnetic field are sampled and analyzed to obtain the field harmonics. To minimize costs, printed circuit boards were used for the pickup windings and a combination of amplifiers and ADPs used for the voltage readout system. New software was developed for the analysis. Magnetic field measurements of a model dipole developed for the SIS200 accelerator at GSI are presented. The measurements are needed to insure that eddy currents induced by the fast ramps do not impact the field quality needed for successful accelerator operation.

JAIN, A.; ESCALLIER, J.; GANETIS, G.; LOUIE, W.; MARONE, A.; THOMAS. R.; WANDERER, P.

2004-10-03

110

Magnetic Fields in Molecular Clouds  

CERN Document Server

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

Goodman, T L B A A

2004-01-01

111

Octupole correlations in $^{229}Ra$  

CERN Multimedia

The structure of /sup 229/Ra has been studied in the beta /sup -/ decay of /sup 229/Fr. Spins and parities have been determined from the conversion electron measurements, while half-lives for the 137.5, 142.7, 168.8, 213.0 and 479.0 keV levels have been measured in the ps and ns ranges via the fast timing beta gamma gamma (t) method. Our data confirm the previous results and enrich the knowledge of the structure of this nucleus by 25 new states and several strong transitions. Structural similarities are established between /sup 229 /Ra and its N=141 isotone /sup 231/Th. The experimental results are compared with the theoretical predictions of the quasiparticle-phonon model with inclusion of Coriolis coupling. The reduced transition probabilities, and especially the moderately fast B(E1) rate for the 137.5 keV transition connecting the band-heads of the K/sup pi /=5/2 /sup +or-/ parity doublet bands, reveal the presence of significant octupole correlations in /sup 229/Ra. (44 refs).

Fraile-Prieto, L M; García-Borge, M J; Fogelberg, B; García-Raffi, L M; Grant, I S; Gulda, K; Hagebø, E; Kurcewicz, W; Kvasil, J; Løvhøiden, G; Mach, H; Mackova, A; Martínez, T; Rubio, B; Taín, J L; Teijeiro, A G; Tengblad, O; Thorsteinsen, T F

1999-01-01

112

The Protogalactic Origin for Cosmic Magnetic Fields  

CERN Document Server

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

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

1996-01-01

113

Generation of helical magnetic fields from inflation  

CERN Multimedia

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

Jain, Rajeev Kumar; Hollenstein, Lukas

2012-01-01

114

Solar magnetic activity cycles, coronal potential field models and eruption rates  

CERN Multimedia

We study the evolution of the observed photospheric magnetic field and the modeled global coronal magnetic field during the past 3 1/2 solar activity cycles observed since the mid-1970s. We use synoptic magnetograms and extrapolated potential-field models based on longitudinal full-disk photospheric magnetograms from the NSO's three magnetographs at Kitt Peak, the Synoptic Optical Long-term Investigations of the Sun (SOLIS) vector spectro-magnetograph (VSM), the spectro-magnetograph and the 512-channel magnetograph instruments, and from the U. Stanford's Wilcox Solar Observatory. The associated multipole field components are used to study the dominant length scales and symmetries of the coronal field. Polar field changes are found to be well correlated with active fields over most of the period studied, except between 2003-6 when the active fields did not produce significant polar field changes. Of the axisymmetric multipoles, only the dipole and octupole follow the poles whereas the higher orders follow the ...

Petrie, G J D

2013-01-01

115

Simulations of magnetic fields in filaments  

CERN Document Server

The intergalactic magnetic field within filaments should be less polluted by magnetised outflows from active galaxies than magnetic fields in clusters. Therefore, filaments may be a better laboratory to study magnetic field amplification by structure formation than galaxy clusters which typically host many more active galaxies. We present highly resolved cosmological AMR simulations of magnetic fields in the cosmos and make predictions about the evolution and structure of magnetic fields in filaments. Comparing our results to observational evidence for magnetic fields in filaments suggests that amplification of seed fields by gravitational collapse is not sufficient to produce IGM fields. Finally, implications for cosmic ray transport are discussed.

Brüggen, M; Simionescu, A; Hoeft, M; Vecchia, C D

2005-01-01

116

Quadrupole and octupole shapes in nuclei  

Energy Technology Data Exchange (ETDEWEB)

The heavy-ion multiple Coulomb excitation technique, which has benefited from many important contributions by Dick Diamond, has developed to the stage where rather complete sets of E1, E2 and E3 matrix elements are being measured. These provide a sensitive measures of quadrupole and octupole deformation in nuclei. The completeness of the E2 data is sufficient to determine directly the centroids and fluctuation widths of the E2 properties in the principal axis frame for low-lying states. The results and model implications of recent Coulomb excitation measurements of the quadrupole shapes in odd and even A nuclei will be presented. Recent measurements of E1, E2 and E3 matrix elements for collective bands in N=88 and Z=88 nuclei show that octupole correlations play an important role. These results and the implications regarding octupole deformation and reflection asymmetry will be discussed.

Cline, D. [Univ. of Rochester, NY (United States)

1993-12-31

117

Origin of solar magnetic fields  

International Nuclear Information System (INIS)

Turbulent-dynamo theories of the solar cycle are criticized, and an alternative theory is proposed.The critique of dynamo theory focuses on attempts to justify the theory's basic physical and mathematical assumptions. It is argued that the theory's fundamental equation, the dynamo equation, is not a mathematically valid or physically plausible approximation to the exact equation governing the mean field; that there is no known physical or mathematical basis for the assumption that fluid turbulence enhances the diffusion of weak magnetic fields, as required by dynamo theories; and that mathematical models of ?? dynamos are internally inconsistent. Dynamo theories also encounter serious observational dificulties. The absence of strong surface fields for extended periods (70 years in the case of the Maunder minimum) is difficult to reconcile with theoretical expectations.The alternative theory invokes a nonregenerated, irregular magnetic field largely confined to the nonconvective core. The genesis of this field during the Hayashi phase of pre-main-sequence evolution and its role in the spin-down of the proto-Sun are discussed in qualitative terms. It is argued that the submerged field interacts with differential rotation mainly in a narrow layer at the base of the convection zone. This interaction drives a t torsional hydromagnetic oscillation which produces the reversing toroidal field in the manner originally suggested by Cowling (1953). This picture accounts qualitatively for the observed ocrrelations among the duration, intensity, and rise time of the magnetic cycle, as well as for the existence of extended periods of surface inactivity

1979-05-01

118

ATLAS cavern magnetic field calculations  

International Nuclear Information System (INIS)

A new approach has been adopted in an attempt to produce a complete ATLAS cavern B-field map using a more precise methodological approach (variable magnetisation, depending on the external field) and the latest design taking into account of the structural elements. The basic idea was to produce a dedicated basic TOSCA model and then to insert a series of ferromagnetic structure elements to monitor the perturbative effect on the basic field map. Eventually, it was found: the bedplate field perturbation is an order of magnitude above the permissible level; manufacturing of the bedplates from nonmagnetic material or careful evaluation of their field contribution in the event reconstruction codes is required; the field value at the rack positions is higher than the permissible one; the final position of racks should be chosen taking into account the detailed magnetic field distribution

2000-01-01

119

ATLAS Cavern Magnetic Field Calculations  

CERN Multimedia

A new approach has been adopted in an attempt to produce a complete ATLAS cavern B-field map using a more precise methodological approach (variable magnetisation, depending on the external field) and the latest design taking into account of the structural elements. The basic idea was to produce a dedicated basic TOSCA model and then to insert a series of ferromagnetic structure elements to monitor the perturbative effect on the basic field map. Eventually, it was found: The bedplate field pertubation is an order of magnitude above the permissible level. Manufacturing of the bedplates from nonmagnetic material or careful evaluation of their field contribution in the event reconstruction codes is required. The field value at the rack positions is higher than the permissible one. The final position of racks should be chosen taking into account the detailed magnetic field distribution.

Vorojtsov, S B; Butin, F; Price, M

2000-01-01

120

Magnetic Field from Loops Model  

Science.gov (United States)

The EJSMagnetic Field from Loops model computes the B-field created by an electric current through a straight wire, a closed loop, and a solenoid. Users can adjust the vertical position of the slice through the 3D field. The Magnetic Field from Loops model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ntnu_MagneticFielfFromLoops.jar file will run the program if Java is installed. Ejs is a part of the Open Source Physics Project and is designed to make it easier to access, modify, and generate computer models. Additional Ejs models for classical mechanics are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang; Hwang, Fu-Kwun

2008-11-17

 
 
 
 
121

Force Free Magnetic Fields and Solar Activity.  

Science.gov (United States)

This report concerning the prediction of solar flares, centers on devising methods for calculating magnetic field structures in the solar atmosphere. Force-free fields comprise an important class of magnetic-field structures which may be calculated by rel...

P. A. Sturrock C. W. Barnes

1974-01-01

122

Magnetic Fields in Protoplanetary Disks  

CERN Document Server

Magnetic fields likely play a key role in the dynamics and evolution of protoplanetary disks. They have the potential to efficiently transport angular momentum by MHD turbulence or via the magnetocentrifugal acceleration of outflows from the disk surface. Magnetically-driven mixing has implications for disk chemistry and evolution of the grain population, and the effective viscous response of the disk determines whether planets migrate inwards or outwards. However, the weak ionisation of protoplanetary disks means that magnetic fields may not be able to effectively couple to the matter. I examine the magnetic diffusivity in a minimum solar nebula model and present calculations of the ionisation equilibrium and magnetic diffusivity as a function of height from the disk midplane at radii of 1 and 5 AU. Dust grains tend to supress magnetic coupling by soaking up electrons and ions from the gas phase and reducing the conductivity of the gas by many orders of magnitude. However, once grains have grown to a few mic...

Wardle, Mark

2007-01-01

123

Magnetic fields in neutron stars  

CERN Multimedia

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, st...

Viganò, Daniele

2013-01-01

124

Majorana neutrinos and magnetic fields  

International Nuclear Information System (INIS)

[en] It is stressed that if neutrinos are massive they are probably of Majorana type. This implies that their magnetic moment form factor vanishes identically so that the previously discussed phenomenon of spin rotation in a magnetic field would not appear to take place. It is pointed out that Majorana neutrinos can, however, have transition moments. This enables an inhomogeneous magnetic field to rotate both spin and flavor of a neutrino. In this case the spin rotation changes particle to anti-particle. The spin-flavor rotation effect is worked out in detail. The parameterization and calculation of the electromagnetic form factors of Majorana neutrinos are discussed, taking into account the somewhat unusual quantum theory of massive Majorana particles

1981-01-01

125

A Fiber Magnetic Field Sensor  

International Nuclear Information System (INIS)

[en] 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

2008-01-01

126

Magnetic field measurement of RIKEN IRC sector magnets  

International Nuclear Information System (INIS)

Magnetic field measurements of the RIKEN IRC sector magnets were made with a newly constructed field mapping system. Using mapping data of the base and trim coil fields for several field levels, production of the isochronous field for a typical ion beam was attempted and the measured field was compared with the expected one

2001-12-12

127

Screening and finite size corrections to the octupole and Schiff moments  

CERN Multimedia

Parity (P) and time reversal (T) violating nuclear forces create P, T -odd moments in expansion of the nuclear electrostatic potential. We derive expression for the nuclear electric octupole field which includes the electron screening correction (similar to the screening term in the Schiff moment). Then we calculate the Z alpha corrections to the Schiff moment which appear due to the finite nuclear size. Such corrections are important in heavy atoms with nuclear charge Z > 50. The Schiff and octupole moments induce atomic electric dipole moments (EDM) and P, T -odd interactions in molecules which are measured in numerous experiments to test CP-violation theories.

Flambaum, V V

2012-01-01

128

Screening and finite-size corrections to the octupole and Schiff moments  

Science.gov (United States)

Parity (P) and time-reversal (T) violating nuclear forces create P,T-odd moments in expansion of the nuclear electrostatic potential. We derive expression for the nuclear electric octupole field which includes the electron screening correction (similar to the screening term in the Schiff moment). Then we calculate the Z2?2 corrections to the Schiff moment which appear due to the finite nuclear size. Such corrections are important in heavy atoms with nuclear charge Z>50. The Schiff and octupole moments induce atomic electric dipole moments and P,T-odd interactions in molecules which are measured in numerous experiments to test CP-violation theories.

Flambaum, V. V.; Kozlov, A.

2012-06-01

129

Magnetic fields in the cosmos  

Energy Technology Data Exchange (ETDEWEB)

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

Parker, E.N.

1983-08-01

130

Neutrinos in Strong Magnetic Fields  

CERN Document Server

We compute the dispersion relations for neutrinos propagating in an electroweak plasma, in the presence of very strong magnetic fields. The neutrino self-energy is calculated in the one-loop approximation. We consider only contributions of the first Landau level to the propagator of the W-bosons, and distinguish between motion parallel or perpendicular to the external magnetic field. We find that the neutrino soup just below the phase transition at the maximal field value $B\\le M_W^2/e$ exhibits spontaneous symmetry breakdown of translational invariance, i.e. superfluidity. Our results seem to validate the idea that the early universe is theoretically similar to the fractional quantum Hall effect.

Pérez-Martínez, A; Agüero, D O; Pérez-Rojas, Hugo Celso; Romo, S R

1997-01-01

131

Magnetic field of the Earth  

Science.gov (United States)

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

Popov, Aleksey

2013-04-01

132

Skewed magnetic field lines reconnection  

International Nuclear Information System (INIS)

Three-dimensional time-dependent reconnection of skewed magnetic field lines is studied. Reconnection is shown to be possible only in the limited oval-shaped part of the current sheet, which was called the reconnection zone. The size of the reconnection zone is defined by the reconnection line length, the behaviour of the electric field in the diffusion region as well as by the angle between the reconnecting fields. Reconnected magnetic flux has the same direction as it has in the Petschek's model near the reconnection line (normal flux), but it changes its sign in the rest of the reconnection zone (anomalous flux). The magnetic energy is converted into the kinetic one in the normal flux region, and the reverse process occurs in the anomalous flux region, so the energy balance is fulfilled within the reconnection region. An electric double layer emerges along the reconnection zone, which emits Alfven waves, these carryin away the energy released in the reconnection process. The solution obtained may be useful in various problems of cosmic plasma physics, e.g. MHD waves generation on the Sun, carrying magnetic flux away from its surface, origin of solar cosmic rays, etc

1986-01-01

133

Unique Topological Characterization of Braided Magnetic Fields  

CERN Multimedia

We introduce a topological flux function to quantify the topology of magnetic braids: non-zero, line-tied magnetic fields whose field lines all connect between two boundaries. This scalar function is an ideal invariant defined on a cross-section of the magnetic field, and measures the average poloidal magnetic flux around any given field line. Moreover, its integral over the cross-section yields the relative magnetic helicity. Using the fact that the flux function is also an action in the Hamiltonian formulation of the field line equations, we prove that it uniquely characterizes the field line mapping and hence the magnetic topology.

Yeates, A R

2012-01-01

134

Establishment of magnetic coordinates for a given magnetic field  

International Nuclear Information System (INIS)

A method is given for expressing the magnetic field strength in magnetic coordinates for a given field. This expression is central to the study of equilibrium, stability, and transport in asymmetric plasmas

1981-01-01

135

Quadrupole and octupole shapes in nuclei  

Energy Technology Data Exchange (ETDEWEB)

This paper outlines the Coulomb excitation technique and presents examples addressing quadrupole deformation in the strongly-deformed nuclei, double-[gamma] bands in even-A osmium nuclei, and the implications of recent measurements of E3 and E1 matrix elements regarding the role of octupole deformation in nuclear structure. (orig.)

Cline, D. (Nuclear Structure Research Lab., Univ. of Rochester, NY (United States))

1993-05-31

136

Generation of magnetic fields for accelerators with permanent magnets  

International Nuclear Information System (INIS)

[en] 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

137

Constraining the central magnetic field of magnetars  

CERN Multimedia

The magnetars are believed to be highly magnetized neutron stars having surface magnetic field 10^{14} - 10^{15} G. It is believed that at the center, the magnetic field may be higher than that at the surface. We study the effect of the magnetic field on the neutron star matter. We model the nuclear matter with the relativistic mean field approach considering the possibility of appearance of hyperons at higher density. We find that the effect of magnetic field on the matter of neutron stars and hence on the mass-radius relation is important, when the central magnetic field is atleast of the order of 10^{17} G. Very importantly, the effect of strong magnetic field reveals anisotropy to the system. Moreover, if the central field approaches 10^{19} G, then the matter becomes unstable which limits the maximum magnetic field at the center of magnetars.

Mukhopadhyay, Banibrata

2013-01-01

138

Magnetic field reversals and galactic dynamos  

CERN Multimedia

We argue that global magnetic field reversals similar to those observed in the Milky Way occur quite frequently in mean-field galactic dynamo models that have relatively strong, random, seed magnetic fields that are localized in discrete regions. The number of reversals decreases to zero with reduction of the seed strength, efficiency of the galactic dynamo and size of the spots of the seed field. A systematic observational search for magnetic field reversals in a representative sample of spiral galaxies promises to give valuable information concerning seed magnetic fields and, in this way, to clarify the initial stages of galactic magnetic field evolution.

Moss, David

2012-01-01

139

Alternating magnetic field moxibustion device  

UK PubMed Central (United Kingdom)

The utility model relates to an alternating magnetic field firing moxibustion device, which is characterized in that one lateral of the surface of an upper casing body is respectively provided with a switch and a display, a wiring board is arranged in the upper casing body, a far-infrared therapeutic plate is embedded in the surface of a lower casing body, the center of the lower casing body is embedded with a groove which is embedded with a magnetic steel which is surrounded by a coil, and a pulse inductive flake is arranged on the upper surface of the magnetic steel. A cavity body which is formed by the upper and lower casing bodies is provided with a large and a small porcelain stands in parallel, a heating flake is arranged on a large porcelain stand, and a controlling flake is arranged on a small porcelain stand, the heating flake and the controlling flake are respectively connected with an electrode flake, the lower portion is provided with a heat storing panel, a radiant panel is adhered on the lower portion of the far-infrared therapeutic plate in parallel, a heat insulating panel which is arranged between the heat storing panel and the far-infrared therapeutic plate is provided with a thermal insulating wire connecting circuit plate and a power cord battery box, and the wiring board circuit is a thyristor power supply controlling circuit which is respectively connected with the coil, the electrode plate, the switch and the display. The structure leads the pulsed magnetic field to connect with a constant magnetic field, which improves the function of far-infrared radiation on the collateral points of human body.

QIAN XU; TIEJUN XU

140

Field errors in superconducting magnets  

Energy Technology Data Exchange (ETDEWEB)

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

Barton, M.Q.

1982-01-01

 
 
 
 
141

Field quality aspects of CBA superconducting magnets  

Energy Technology Data Exchange (ETDEWEB)

A series of superconducting dipole magnets for the BNL Colliding Beam Accelerator which were manufactured to have the proper field quality characteristics has been tested. This report presents the analysis of the field harmonics of these magnets.

Kahn, S.; Engelmann, R.; Fernow, R.; Greene, A.F.; Herrera, J.; Kirk, H.; Skaritka, J.; Wanderer, P.; Willen, E.

1983-01-01

142

Statistics of Magnetic Fields for OB Stars  

CERN Multimedia

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

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

2010-01-01

143

Evolution of magnetic field in interacting galaxies  

CERN Multimedia

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

Drzazga, Robert T; Jurusik, Wojciech

2012-01-01

144

Rotating copper plasmoid in external magnetic field  

Energy Technology Data Exchange (ETDEWEB)

Effect of nonuniform magnetic field on the expanding copper plasmoid in helium and argon gases using optical emission spectroscopy and fast imaging is presented. We report a peculiar oscillatory rotation of plasmoid in magnetic field and argon ambient. The temporal variation and appearance of the dip in the electron temperature show a direct evidence of the threading and expulsion of the magnetic field lines from the plasmoid. Rayleigh Taylor instability produced at the interface separating magnetic field and plasma is discussed.

Pandey, Pramod K.; Thareja, Raj K. [Department of Physics, Indian Institute of Technology Kanpur, Uttar Pradesh 208 016 (India)

2013-02-15

145

Rotating copper plasmoid in external magnetic field  

International Nuclear Information System (INIS)

[en] Effect of nonuniform magnetic field on the expanding copper plasmoid in helium and argon gases using optical emission spectroscopy and fast imaging is presented. We report a peculiar oscillatory rotation of plasmoid in magnetic field and argon ambient. The temporal variation and appearance of the dip in the electron temperature show a direct evidence of the threading and expulsion of the magnetic field lines from the plasmoid. Rayleigh Taylor instability produced at the interface separating magnetic field and plasma is discussed.

2013-01-01

146

Topological constraints in magnetic field relaxation  

CERN Multimedia

Stability and reconnection of magnetic fields play a fundamental role in natural and man-made plasma. In these applications the field's topology determines the stability of the magnetic field. Here I will describe the importance of one topology quantifier, the magnetic helicity, which impedes any free decay of the magnetic energy. Further constraints come from the fixed point index which hinders the field to relax into the Taylor state.

Candelaresi, Simon

2013-01-01

147

Magnetic field effect for cellulose nanofiber alignment  

Science.gov (United States)

Regenerated cellulose formed into cellulose nanofibers under strong magnetic field and aligned perpendicularly to the magnetic field. Well-aligned microfibrils were found as the exposure time of the magnetic field increased. Better alignment and more crystalline structure of the cellulose resulted in the increased decomposition temperature of the material. X-ray crystallograms showed that crystallinity index of the cellulose increased as the exposure time of the magnetic field increased.

Kim, Jaehwan; Chen, Yi; Kang, Kwang-Sun; Park, Young-Bin; Schwartz, Mark

2008-11-01

148

Magnetic field perturbartions in closed-field-line systems with zero toroidal magnetic field  

Energy Technology Data Exchange (ETDEWEB)

In some plasma confinement systems (e.g., field-reversed configurations and levitated dipoles) the confinement is provided by a closed-field-line poloidal magnetic field. We consider the influence of the magnetic field perturbations on the structure of the magnetic field in such systems and find that the effect of perturbations is quite different from that in the systems with a substantial toroidal field. In particular, even infinitesimal perturbations can, in principle, lead to large radial excursions of the field lines in FRCs and levitated dipoles. Under such circumstances, particle drifts and particle collisions may give rise to significant neoclassical transport. Introduction of a weak regular toroidal magnetic field reduces radial excursions of the field lines and neoclassical transport.

Mauel, M; Ryutov, D; Kesner, J

2003-12-02

149

Primordial magnetic field limits from cosmological data  

International Nuclear Information System (INIS)

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

2010-10-15

150

A concentrator for static magnetic field  

CERN Multimedia

We propose a compact passive device as a super-concentrator to achieve an extremely high uniform static magnetic field over 50T in a large two-dimensional free space in the presence of a uniform weak background magnetic field. Our design is based on transformation optics and metamaterials for static magnetic fields. Finite element method (FEM) is utilized to verify its performance.

Sun, F

2013-01-01

151

Quarkyonic Chiral Spirals in a Magnetic Field  

CERN Multimedia

We discuss the formation of quarkyonic chiral spirals in the presence of a magnetic field. The explicit breaking of the rotational symmetry by the external magnetic field gives rise to an additional chiral spiral that varies along the field direction and rotates in the chiral space between pion and magnetic moment components.

Ferrer, Efrain J; Sanchez, Angel

2012-01-01

152

Primordial magnetic field limits from cosmological data  

CERN Multimedia

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

Kahniashvili, Tina; Sethi, Shiv K; Pandey, Kanhaiya; Ratra, Bharat

2010-01-01

153

Bacterial Growth in Weak Magnetic Field  

Science.gov (United States)

We study the effect of the weak magnetic field on the growth of bacteria. We found that the magnetic field has tremendous effects on the growth of bacteria. They follow the same growth curve however the increased growth rate let the growth curve follow through its path, quickly. We also notice that different magnetic fields affect differently on different types of bacteria.

Masood, Samina

2012-10-01

154

Magnetic Field Induced Chain Alignment of Ferroparticles in Magnetic Fluid  

Directory of Open Access Journals (Sweden)

Full Text Available Chain alignment of suspended-ferroparticles in a carrier fluid exposed to the external magnetic field was investigated theoretically and experimentally. The results show that without the external magnetic field the ferroparticles were randomly distributed and when exposed to uniform magnetic field the turned out to be a chained-alignment pattern along the external magnetic field orientation at intensity of 11.1 kA/m. With the external uniform magnetic field intensity up to 28.6 kA/m, more ferroparticles closely aggregated to a chained-alignment pattern along the magnetic field direction. When the magnetic field intensity reached 28.7 kA/m in the gradient magnetic field, a large number of ferroparticles gathered around the coils and formed complex clusters, while a small number of ferroparticles demonstrated a chain-alignment pattern along r direction with weaker magnetic field intensity. When the magnetic field gradient was gradually increasing from 1.73 kA/m2 to 5.11 kA/m2, the cluster pattern of ferroparticles turned out to be dense along the axis. This research may enhance the applications of magnetic fluid in the fields of mechanical engineering, bioengineering and thermodynamic engineering.

LI Yan-Qin, BU De-Cai, LI Xue-Hui

2013-01-01

155

Plastic scintillators in magnetic fields  

International Nuclear Information System (INIS)

The dependence of the light yield and the transmission on magnetic field has been measured with different methods up to 0.45 T for the plastic scintillators NE-102A, SCSN-38, and Polivar. The scintillators were excited by 25 MeV protons, 5.9 keV X-rays and UV light. When excited with ionizing radiation an increase of light yield is observed. For SCSN-38 of 2.6 mm thickness it amounts to 0.3%, 0.9%, 1.1% and 3.3% at 1, 10, 100 and 450 mT, respectively. NE-102A behaves similar, whereas an acrylic scintillator shows a stronger field dependence. The effect is independent of the direction of the field but increases for the Polivar scintillator with its thickness. No change in the decay time of the scintillator has been observed. The response of the scintillators did not change when excited by UV light in a magnetic field. (orig.)

1991-01-01

156

Magnetic design and measurement of nonlinear multipole magnets for the APT beam expander system  

Energy Technology Data Exchange (ETDEWEB)

Two prototype nonlinear multipole magnets have been designed for use in the 800-MeV beam test of the APT beam-expansion concept at LANSCE. The iron-dominated magnets each consist of three independent coils, two for producing a predominantly octupole field with a tunable duodecapole component, and one for canceling the residual quadrupole field. Two such magnets, one for shaping each transverse plane, are required to produce a rectangular, uniform beam current density distribution with sharp edges on the APT target. This report will describe the magnetic design of these magnets, along with field measurements, and a comparison to the magnetic design.

Barlow, D.B.; Shafer, R.E.; Martinez, R.P. [Los Alamos National Lab., NM (United States); Walstrom, P.L. [Northrop Grumman Corp., Princeton, NJ (United States); Kahn, S.; Jain, A.; Wanderer, P. [Brookhaven National Lab., Upton, NY (United States)

1997-10-01

157

Magnetic design and measurement of nonlinear multipole magnets for the APT beam expander system  

International Nuclear Information System (INIS)

Two prototype nonlinear multipole magnets have been designed for use in the 800-MeV beam test of the APT beam-expansion concept at LANSCE. The iron-dominated magnets each consist of three independent coils, two for producing a predominantly octupole field with a tunable duodecapole component, and one for canceling the residual quadrupole field. Two such magnets, one for shaping each transverse plane, are required to produce a rectangular, uniform beam current density distribution with sharp edges on the APT target. This report will describe the magnetic design of these magnets, along with field measurements, and a comparison to the magnetic design

1997-01-01

158

Magnetic monopole and the nature of the static magnetic field  

CERN Multimedia

We investigate the factuality of the hypothetical magnetic monopole and the nature of the static magnetic field. It is shown from many aspects that the concept of the massive magnetic monopoles clearly is physically untrue. We argue that the static magnetic field of a bar magnet, in fact, is the static electric field of the periodically quasi-one-dimensional electric-dipole superlattice, which can be well established in some transition metals with the localized d-electron. This research may shed light on the perfect unification of magnetic and electrical phenomena.

Huang, Xiuqing

2008-01-01

159

Observations of Cool-Star Magnetic Fields  

CERN Multimedia

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. Our observational picture of cool-star magnetic fields has improved tremendously over the last years. Sophisticated methods were developed to search for the subtle effects of magnetism, which are difficult to detect particularly in cool stars. With an emphasis on the assumptions and capabilities of modern methods used to measure magnetism in cool stars, I review the different techniques available for magnetic field measurements. I collect the analyses on cool-star magnetic fields and try to compare results from different me...

Reiners, Ansgar

2012-01-01

160

Nuclear magnetic resonance apparatus for pulsed high magnetic fields.  

UK PubMed Central (United Kingdom)

A nuclear magnetic resonance apparatus for experiments in pulsed high magnetic fields is described. The magnetic field pulses created together with various magnet coils determine the requirements such an apparatus has to fulfill to be operated successfully in pulsed fields. Independent of the chosen coil it is desirable to operate the entire experiment at the highest possible bandwidth such that a correspondingly large temporal fraction of the magnetic field pulse can be used to probe a given sample. Our apparatus offers a bandwidth of up to 20 MHz and has been tested successfully at the Hochfeld-Magnetlabor Dresden, even in a very fast dual coil magnet that has produced a peak field of 94.2 T. Using a medium-sized single coil with a significantly slower dependence, it is possible to perform advanced multi-pulse nuclear magnetic resonance experiments. As an example we discuss a Carr-Purcell spin echo sequence at a field of 62 T.

Meier B; Kohlrautz J; Haase J; Braun M; Wolff-Fabris F; Kampert E; Herrmannsdörfer T; Wosnitza J

2012-08-01

 
 
 
 
161

Hypernuclear matter in strong magnetic field  

CERN Multimedia

Compact stars with strong magnetic fields (magnetars) have been observationally determined to have surface magnetic fields of order of 10^{14}-10^{15} G, the implied internal field strength being several orders larger. We study the equation of state and composition of dense hypernuclear matter in strong magnetic fields in a range expected in the interiors of magnetars. Within the non-linear Boguta-Bodmer-Walecka model we find that the magnetic field has sizable influence on the properties of matter for central magnetic field B \\ge 10^{17} G, in particular the matter properties become anisotropic. Moreover, for the central fields B_{\\rm cr} \\ge 10^{19} G, the magnetized hypernuclear matter becomes unstable, which limits the range of admissible fields in magnetars to fields below the critical value B_{\\rm cr}.

Sinha, Monika; Sedrakian, Armen

2012-01-01

162

PROCESS OF PLANETS’ MAGNETIC FIELDS FORMATION  

Directory of Open Access Journals (Sweden)

Full Text Available Heated melt of the cores of the Sun and the planets is the basis of their permanent magnetic fields that, in interaction with the large-scale magnetic field of the Galaxy, condition on the action of their dynamo mechanisms which, on the basis of the speed of the Sun and the planets axial rotation in the galactic magnetic space, provide formation of variable magnetic fields of the Solar System planets.

E.V. Savich

2013-01-01

163

Magnetic field source for dark mode spectroscopy  

Directory of Open Access Journals (Sweden)

Full Text Available The paper is focused on the study of two-dimensional magnetic field distribution used for the analysis of the samples containing magnetically active films by means of dark mode spectroscopy (DMS). The design of proposed electromagnet for in-plane magneto-optic configuration and the magnetic field model computation are presented together with the results obtained from magnetic field distribution measurement.

Frantisek Stanek; Jaromir Pistora; Michal Lesnak

2010-01-01

164

Magnetic field measuring system for remapping the ORIC magnetic field  

International Nuclear Information System (INIS)

[en] The Holifield Heavy Ion Research Facility will integrate a new 25 MV tandem electrostatic acccelerator into the existing cyclotron laboratory which includes the Oak Ridge Isochronous Cyclotron (ORIC). Computations of ion paths for beam injection from the new tandem into ORIC require field mapping in the regions traversed by the beam. Additional field data is also desired for the higher levels (approx.19 kG) now used for most heavy ion beams. The magnetic field measurement system uses 39 flip coil/current integrator sets with computer controlled data scanning. The coils are spaced radially at 1 inch intervals in an arm which can be rotated azimuthally in 2 degree increments. The entire flip coil assembly can be shifted to larger radii to measure fields beyond the pole boundary. Temperature stabilization of electronic circuitry permits a measurement resolution of +-1 gauss over a dynamic range of +-25,000 gauss. The system will process a scan of 8000 points in about one hour

1977-03-18

165

Superconductivity induced by magnetic field?  

International Nuclear Information System (INIS)

It is shown that the effect of the giant negative magnetoresistance in doped manganite can be explained in the framework of the model based on the accounting of the covalence of the transition metal-oxygen binding. This effect is connected with the delocalization of ?-electrons along the asymmetric ?-orbitals belonging to chains of covalently bond ions of Mn and O. The delocalization of ?-electrons in manganite is induced by the magnetic field orienting the ferromagnetically unpaired ?-electrons and permitting the collective motion along the ?-orbital at conditions of the ferromagnetic ordering of manganese ions

1999-07-12

166

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

International Nuclear Information System (INIS)

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

2005-01-01

167

Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization  

Energy Technology Data Exchange (ETDEWEB)

In a plasma-producing device, an optimized magnet field for electron cyclotron resonance plasma generation is provided by a shaped pole piece. The shaped pole piece adjusts spacing between the magnet and the resonance zone, creates a convex or concave resonance zone, and decreases stray fields between the resonance zone and the workpiece. For a cylindrical permanent magnet, the pole piece includes a disk adjacent the magnet together with an annular cylindrical sidewall structure axially aligned with the magnet and extending from the base around the permanent magnet. The pole piece directs magnetic field lines into the resonance zone, moving the resonance zone further from the face of the magnet. Additional permanent magnets or magnet arrays may be utilized to control field contours on a local scale. Rather than a permeable material, the sidewall structure may be composed of an annular cylindrical magnetic material having a polarity opposite that of the permanent magnet, creating convex regions in the resonance zone. An annular disk-shaped recurve section at the end of the sidewall structure forms magnetic mirrors keeping the plasma off the pole piece. A recurve section composed of magnetic material having a radial polarity forms convex regions and/or magnetic mirrors within the resonance zone.

Doughty, Frank C. (Plano, TX); Spencer, John E. (Plano, TX)

2000-12-19

168

Strong and superstrong pulsed magnetic fields generation  

CERN Multimedia

Strong pulsed magnetic fields are important for several fields in physics and engineering, such as power generation and accelerator facilities. Basic aspects of the generation of strong and superstrong pulsed magnetic fields technique are given, including the physics and hydrodynamics of the conductors interacting with the field as well as an account of the significant progress in generation of strong magnetic fields using the magnetic accumulation technique. Results of computer simulations as well as a survey of available field technology are completing the volume.

Dolotenko, Mikhail I; Shneerson, German A

2014-01-01

169

Magnetization reversal of ferromagnetic nanoparticles under inhomogeneous magnetic field  

International Nuclear Information System (INIS)

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

2007-01-01

170

Trapped magnetic field in a superconducting disk magnetized by uniform field  

CERN Document Server

The distribution of the current density and the profile of the trapped magnetic field of a superconducting disk magnetized by uniform field are calculated from first principles. The effect of the superconducting parameters is taken into account by assuming the voltage-current law and the material law. The sample volume, the critical current density and the flux creep exponent dominate the strength of the trapped magnetic field. The flux creep exponent determines the decay rate of the trapped magnetic field. The aspect ratio of the sample influences the shape of the trapped magnetic flux lines. We conclude that higher trapped magnetic field cannot always be obtained by increasing the applied magnetic field.

Li, C; He, C Y; Meng, L F; Han, R; Gao, Z X

2002-01-01

171

Chaotic magnetic field reversals in turbulent dynamos  

CERN Document Server

We present direct numerical simulations of reversals of the magnetic field generated by swirling flows in a spherical domain. In agreement with a recent model, we observe that coupling dipolar and quadrupolar magnetic modes by an asymmetric forcing of the flow generates field reversals. In addition, we show that this mechanism strongly depends on the value of the magnetic Prandtl number.

Gissinger, Christophe; Fauve, Stephan

2009-01-01

172

Neutron star deformation due to arbitrary-order multipolar magnetic fields  

CERN Multimedia

Certain multi-wavelength observations of neutron stars, such as intermittent radio emissions from rotation-powered pulsars beyond the pair-cascade death line, the pulse profile of the magnetar SGR 1900+14 after its 1998 August 27 giant flare, and X-ray spectral features of PSR J0821-4300 and SGR 0418+5729, suggest that the magnetic fields of non-accreting neutron stars are not purely dipolar and may contain higher-order multipoles. Here, we calculate the ellipticity of a non-barotropic neutron star with (i) a quadrupole poloidal-toroidal field, and (ii) a purely poloidal field containing arbitrary multipoles, deriving the relation between the ellipticity and the multipole amplitudes. We present, as a worked example, a purely poloidal field comprising dipole, quadrupole, and octupole components. We show the correlation between field energy and ellipticity for each multipole, that the l=4 multipole has the lowest energy, and that l=5 has the lowest ellipticity. We show how a mixed multipolar field creates an ob...

Mastrano, Alpha; Melatos, Andrew

2013-01-01

173

Dynamic shielding of the magnetic fields  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents a comparative study of the methods used to control and compensate the direct and alternative magnetic fields. Two frequently used methods in the electromagnetic compatibility of the complex biomagnetism installations were analyzed. The two methods refer to the use of inductive magnetic field sensors (only for alternative fields) and of fluxgate magnetometers as active transducers which measures both the direct and alternative components of the magnetic field. The applications of the dynamic control of the magnetic field are: control of the magnetic field of the military ships, control of parasite magnetic field produced by power transformers and the electrical networks, protection of the mass spectrometers, electronic microscopes, SQUID and optical pumping magnetometers for applications in biomagnetism.

BALTAG, O.; COSTANDACHE, D.; RAU, M.; IFTEMIE, A.; RAU, I.

2010-01-01

174

Bipolar pulse field for magnetic refrigeration  

Energy Technology Data Exchange (ETDEWEB)

A magnetic refrigeration apparatus includes first and second steady state magnets, each having a field of substantially equal strength and opposite polarity, first and second bodies made of magnetocaloric material disposed respectively in the influence of the fields of the first and second steady state magnets, and a pulsed magnet, concentric with the first and second steady state magnets, and having a field which cycles between the fields of the first and second steady state magnets, thereby cyclically magnetizing and demagnetizing and thus heating and cooling the first and second bodies. Heat exchange apparatus of suitable design can be used to expose a working fluid to the first and second bodies of magnetocaloric material. A controller is provided to synchronize the flow of working fluid with the changing states of magnetization of the first and second bodies. 2 figs.

Lubell, M.S.

1994-10-25

175

Bipolar pulse field for magnetic refrigeration  

Energy Technology Data Exchange (ETDEWEB)

A magnetic refrigeration apparatus includes first and second steady state magnets, each having a field of substantially equal strength and opposite polarity, first and second bodies made of magnetocaloric material disposed respectively in the influence of the fields of the first and second steady state magnets, and a pulsed magnet, concentric with the first and second steady state magnets, and having a field which cycles between the fields of the first and second steady state magnets, thereby cyclically magnetizing and demagnetizing and thus heating and cooling the first and second bodies. Heat exchange apparatus of suitable design can be used to expose a working fluid to the first and second bodies of magnetocaloric material. A controller is provided to synchronize the flow of working fluid with the changing states of magnetization of the first and second bodies.

Lubell, Martin S. (Oak Ridge, TN)

1994-01-01

176

MAGNETIC BRAIDING AND PARALLEL ELECTRIC FIELDS  

International Nuclear Information System (INIS)

The braiding of the solar coronal magnetic field via photospheric motions-with subsequent relaxation and magnetic reconnection-is one of the most widely debated ideas of solar physics. We readdress the theory in light of developments in three-dimensional magnetic reconnection theory. It is known that the integrated parallel electric field along field lines is the key quantity determining the rate of reconnection, in contrast with the two-dimensional case where the electric field itself is the important quantity. We demonstrate that this difference becomes crucial for sufficiently complex magnetic field structures. A numerical method is used to relax a braided magnetic field toward an ideal force-free equilibrium; the field is found to remain smooth throughout the relaxation, with only large-scale current structures. However, a highly filamentary integrated parallel current structure with extremely short length-scales is found in the field, with the associated gradients intensifying during the relaxation process. An analytical model is developed to show that, in a coronal situation, the length scales associated with the integrated parallel current structures will rapidly decrease with increasing complexity, or degree of braiding, of the magnetic field. Analysis shows the decrease in these length scales will, for any finite resistivity, eventually become inconsistent with the stability of the coronal field. Thus the inevitable consequence of the magnetic braiding process is a loss of equilibrium of the magnetic field, probably via magnetic reconnection events.

2009-05-10

177

Franck-Hertz experiment in magnetic field  

CERN Multimedia

The paper studies the impact of applied magnetic field on the inelastic collisions of electrons with argon atoms. In the electron-argon Franck-Hertz experiment, the influence of applied magnetic field emerges complicated features, and is equivalent to that of the temperature. In case the accelerating electric intensity becomes strong enough, enlarging magnetic flux density will be equivalent to the increasing of oven temperature. When the accelerating electric intensity is very weak and the applied magnetic field occupies a dominant position, enhancing magnetic flux density is identical with the decreasing of oven temperature. And the non-uniform distribution of applied magnetic field has an influence on the inelastic collision as well. The study claims that the influence of magnetic field variation is equivalent to that of temperature variety, and that it leads the electron energy to transfer obviously in the experiment.

Weng, Ying

2010-01-01

178

Nonlinear physics of twisted magnetic field lines  

Energy Technology Data Exchange (ETDEWEB)

Twisted magnetic field lines appear commonly in many different plasma systems, such as magnetic ropes created through interactions between the magnetosphere and the solar wind, magnetic clouds in the solar wind, solar corona, galactic jets, accretion discs, as well as fusion plasma devices. In this paper, we study the topological characterization of twisted magnetic fields, nonlinear effect induced by the Lorentz back reaction, length-scale bounds, and statistical distributions. (author)

Yoshida, Zensho [Department of Quantum Engineering, University of Tokyo, Tokyo (Japan)

1998-08-01

179

Spontaneous magnetic fields in spherical laser targets  

International Nuclear Information System (INIS)

Results of theoretical investigation into generation effect of spontaneous magnetic fields as applied to laser target contraction under conditions of ''contractile'' shell are presented. Two approaches were used: a) qualitative description of a problem construction of simple physical models; b) numerical solution of equations of two-dimensional gas dynamics together with equation of generation of spontaneous magnetic fields. Results of investigation of magnetic field generation in corona of laser targets, fields generated due to development of the Rayleigh-Taylor instability; fields conditioned with appearance of crossed density and temperature gradients during target contraction are given. Experimental methods for investigating spontaneous magnetic fields in laser plasma are described in short. It is shown that in contractile targets 10MGs magnetic fields are generated at absorbed laser energy of up to 10 kJ and up to 100 MGs at absorbed energy above 100 kJ. In this case fields will significantly affect energy transfer with charged particles.

1985-01-01

180

Principles in power system magnetic field reduction  

Energy Technology Data Exchange (ETDEWEB)

The basic principles of generation of magnetic fields are identified, analyzed and synthesized for reduction of power system magnetic fields, notably from transmission lines. The field reduction methods studied are phase-split arrangements, passive shielding with and without series compensation, and configuration twist. A novel unorthodox four-conductor arrangement is presented. 3 refs, 8 figs

Pettersson, Per [Vattenfall Utveckling AB, Vaellingby (Sweden)

1995-12-01

 
 
 
 
181

Relativistic hydrogenic atoms in strong magnetic fields  

CERN Document Server

In the Dirac operator framework we characterize and estimate the ground state energy of relativistic hydrogenic atoms in a constant magnetic field and describe the asymptotic regime corresponding to a large field strength using relativistic Landau levels. We also define and estimate a critical magnetic field beyond which stability is lost.

Dolbeault, J; Loss, M; Dolbeault, Jean; Esteban, Maria J.; Loss, Michael

2006-01-01

182

Dirac oscillator in an external magnetic field  

International Nuclear Information System (INIS)

[en] We show that (2+1)-dimensional Dirac oscillators in an external magnetic field is mapped onto the same with reduced angular frequency in absence of magnetic field. This can be used to study the atomic transitions in a radiation field. Relativistic Landau levels are constructed explicitly. Several interesting features of this system are discussed.

2010-02-08

183

DC-based magnetic field controller  

Energy Technology Data Exchange (ETDEWEB)

A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.

Kotter, Dale K. (Shelley, ID); Rankin, Richard A. (Ammon, ID); Morgan, John P,. (Idaho Falls, ID)

1994-01-01

184

Transverse conductivity in a braided magnetic field  

Energy Technology Data Exchange (ETDEWEB)

The current orthogonal to the flux surfaces is calculated as the function of electric field for the externally produced magnetic field fluctuations. It has been demonstrated that the current is produced by a parallel of ions in a curvilinear magnetic field. (author). 6 refs.

Kaganovich, I.; Rozhansky, V. [St. Petersburg State Technical Univ. (Russian Federation). Physical Technical Dept.; Tendler, M. [Royal Inst. of Tech., Stockholm (Sweden). Alfven Lab.

1994-12-31

185

Studies of a poloidal divertor reversed field pinch  

International Nuclear Information System (INIS)

Several attempts have been made to form a reversed field pinch (RFP) in a four-node, poloidal divertor configuration which positions the plasma far from a conducting wall. In this configuration, the plasma is localized within a magnetic separatrix formed by the combination of toroidal currents in the plasma and four, internal, conducting rings. These experiments were conducted on three devices: Tokapole II, the Wisconsin Levitated Octupole, and the modified Octupole with smaller conducting rings. Transient, RFP-like equilibria were obtained on Tokapole II and the Wisconsin Levitated Octupole. RFP-like equilibria with field reversal duration /approximately/1 msec were obtained in the small ring Octupole. None of these plasmas was sustained against resistive magnetic diffusion. Local, internal measurements of the magnetic field in Tokapole II plasmas indicated the plasma current and density were mostly confined to the region inside the magnetic separatrix. The sharp drop in plasma pressure near the separatrix generated a large diamagnetic current in that region. Large magnetic perturbations observed in the startup phase of these plasmas. On the small ring Octupole, the perturbation was measured to have a dominant poloidal mode number of m = 1 and toroidal mode numbers n /approximately/ /minus/5, i.e., internally resonant or nonresonant modes. This perturbation was stationary and was phase-locked to a magnetic field error. If the tenuous plasma region outside the separatrix is ''vacuum-like,'' then this behavior might represent current-driven instability owing to the lack of nearly, stabilizing boundary. Such instability is consistent with linear magnetohydrodynamic stability calculations and nonlinear simulations of a cylindrical REP plasma bounded by a large vacuum region and a distant conducting wall. 53 refs., 48 figs.

1988-01-01

186

X-ray diffraction in magnetic fields  

International Nuclear Information System (INIS)

A method to determine the direction of magnetization in polycrystalline materials was developed using X-ray powder diffraction under an external magnetic field. The application of the magnetic field to the powdered sample induces a preferred orientation. By observing the changes in the line intensities as a consequence, the direction of spontaneous magnetization within the lattice can be determined in the case of a ferro- or ferrimagnetic arrangement. Since the sample holder with the permanent magnet is mounted on the cold finger of a flow cryostat, it is also possible to observe a change in direction of spontaneous magnetization as a function of the temperature. (orig.).

1997-01-01

187

X-ray diffraction in magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

A method to determine the direction of magnetization in polycrystalline materials was developed using X-ray powder diffraction under an external magnetic field. The application of the magnetic field to the powdered sample induces a preferred orientation. By observing the changes in the line intensities as a consequence, the direction of spontaneous magnetization within the lattice can be determined in the case of a ferro- or ferrimagnetic arrangement. Since the sample holder with the permanent magnet is mounted on the cold finger of a flow cryostat, it is also possible to observe a change in direction of spontaneous magnetization as a function of the temperature. (orig.)

Pototschnig, P. [Technische Univ. Vienna (Austria). Inst. fuer Exp. Phys.; Gratz, E. [Technische Univ. Vienna (Austria). Inst. fuer Exp. Phys.; Kirchmayr, H. [Technische Univ. Vienna (Austria). Inst. fuer Exp. Phys.; Lindbaum, A. [Technische Univ. Vienna (Austria). Inst. fuer Exp. Phys.

1997-01-30

188

Static uniform magnetic fields and amoebae  

Energy Technology Data Exchange (ETDEWEB)

Three species of potentially pathogenic amoebae were exposed to 71 and 106.5 mT from constant homogeneous magnetic fields and examined for inhibition of population growth. The number of amoebae for three species was significantly less than controls after a 72 h exposure to the magnetic fields when the temperature was 20 C or above. Axenic cultures, i.e., cultures grown without bacteria, were significantly affected after only 24 h. In 20 of 21 tests using the three species, the magnetic field significantly inhibited the growth of amoebae. In one test in which the temperature was 20 C for 48 h, exposure to the magnetic field was not inhibitory. Final numbers of magnetic field-exposed amoebae ranged from 9 to 72% lower than the final numbers of unexposed controls, depending on the species. This research may lead to disinfection strategies utilizing magnetic fields for surfaces on which pathogenic amoebae may proliferate.

Berk, S.G.; Srikanth, S.; Mahajan, S.M.; Ventrice, C.A. [Tennessee Technological Univ., Cookeville, TN (United States)

1997-03-01

189

Magnetization transfer contrast in high magnetic field  

International Nuclear Information System (INIS)

Cross relaxation between macromolecular protons and water protons is known to be important in biologic tissue. In magnetic resonance imaging sequences with a selective saturation of the characteristically short T2, the macromolecular proton pool can produce contrast in the images so called magnetization transfer contrast [MTC], based on the cross-relaxation process. The magnetization transfer can manipulate both the available longitudinal magnetization and the T1 of tissues. In a conventional spin echo technique with presaturated RF pulses, the reduction in available magnetization increased contrast on proton density-weighted images. The effects of repetition time TR, RF irradiation duration, and echo time TE on the magnetization transfer effect were studied, and images of the rat head, samples of water and oil were obtained at 7.05T. The signal intensities of the different tissues on the MTC images were compared with those on the control images obtained under identical conditions without the off-resonance irradiation. Quantitative analysis of tissue signal intensity was performed by examining regions of interest from each tissue. The results indicated that when MTC was used in conjunction with spin echo imaging, the shorter the echo time TE was, the higher contrast was obtained. This finding was even true at short TRs. The images reflected somewhat no dependence on either T1 or T2 weightings. Non-selective saturation of the water proton pool was also discussed from the point of view of the relaxation times. (author).

1995-01-01

190

Primordial magnetic fields from pseudo Goldstone bosons  

Energy Technology Data Exchange (ETDEWEB)

The existence of large-scale magnetic fields in galaxies is well established, but there is no accepted mechanism for generating a primordial field which could grow into what is observed today. We discuss a model which attempts to account for the necessary primordial field by invoking a pseudo Goldstone boson coupled to electromagnetism. The evolution of this boson during inflation generates a magnetic field; however, it seems difficult on rather general grounds to obtain fields of sufficient strength on astrophysically interesting scales.

Garretson, W.D.; Field, G.B.; Carroll, S.M. (Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States))

1992-12-15

191

Transient Magnetic Field in a Conducting Cylinder  

Directory of Open Access Journals (Sweden)

Full Text Available In the paper we determine the transient magnetic field in a conducting cylinder placed in external longitudinal sine-shaped magnetic field using the solution of Bessell equation in cylindrical co-ordinates, and also applying integral Laplace transformations, attenuation and diffusion of the magnetic field strength in the cylinder. The resulting equations can be used to describe volume density of the power lost in the cylinder and to determine substitute parameters of the inductor-cylindrical work system.

Zygmunt Piatek

2004-01-01

192

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 the 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.

2001-07-02

193

Noncommutativity in Space and Primordial Magnetic Field  

CERN Document Server

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 the 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.

Mazumdar, A

2001-01-01

194

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

195

Ferroelectric Cathodes in Transverse Magnetic Fields  

International Nuclear Information System (INIS)

[en] Experimental investigations of a planar ferroelectric cathode in a transverse magnetic field up to 3 kGs are presented. It is shown that the transverse magnetic field affects differently the operation of ferroelectric plasma cathodes in ''bright'' and ''dark'' modes in vacuum. In the ''bright'' mode, when the surface plasma is formed, the application of the transverse magnetic field leads to an increase of the surface plasma density. In the ''dark'' mode, the magnetic field inhibits the development of electron avalanches along the surface, as it does similarly in other kinds of surface discharges in the pre-breakdown mode

2002-01-01

196

Quark matter in a strong magnetic field  

Energy Technology Data Exchange (ETDEWEB)

The effect of a strong magnetic field on the stability and gross properties of bulk as well as quasibulk quark matter is investigated using the conventional MIT bag model. Both the Landau diamagnetism and the paramagnetism of quark matter are studied. How the quark hadron phase transition is affected by the presence of a strong magnetic field is also investigated. The equation of state of strange quark matter changes significantly in a strong magnetic field. It is also shown that the thermal nucleation of quark bubbles in a compact metastable state of neutron matter is completely forbidden in the presence of a strong magnetic field. {copyright} {ital 1996 The American Physical Society.}

Chakrabarty, S. [Department of Physics, University of Kalyani, District: Nadia, West Bengal 741 235 (India)]|[Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411 007 (India)

1996-07-01

197

Rectangular quantum dots in high magnetic fields  

CERN Multimedia

We use density-functional methods to study the effects of an external magnetic field on two-dimensional quantum dots with a rectangular hard-wall confining potential. The increasing magnetic field leads to spin polarization and formation of a highly inhomogeneous maximum-density droplet at the predicted magnetic field strength. At higher fields, we find an oscillating behavior in the electron density and in the magnetization of the dot. We identify a rich variety of phenomena behind the periodicity and analyze the complicated many-electron dynamics, which is shown to be highly dependent on the shape of the quantum dot.

Räasänen, E; Puska, M J; Nieminen, R M

2003-01-01

198

Topological constraints on magnetic field relaxation  

CERN Multimedia

Magnetic field relaxation is determined by both the field's geometry and its topology. For relaxation processes, however, it turns out that its topology is a much more stringent constraint. As quantifier for the topology we use magnetic helicity and test whether it is a stronger condition than the linking of field lines. Further, we search for evidence of other topological invariants, which give rise to further restrictions in the field's relaxation. We find that magnetic helicity is the sole determinant in most cases. Nevertheless, we see evidence for restrictions not captured through magnetic helicity.

Candelaresi, Simon

2012-01-01

199

Magnetotransport in a spatially modulated magnetic field  

Directory of Open Access Journals (Sweden)

Full Text Available We have measured the Shubnikov de Haas (SdH) oscillations of a nonplanar two-dimensional electron gas (2DEG) fabricated by overgrowth of a GaAs/AlGaAs heterojunction on a pre-patterned substrate. When placed in a uniform external magnetic field B, the field normal to the nonplanar 2DEG is spatially modulated, and electrons experience a nonuniform magnetic field. In a tilted magnetic field, the SdH oscillations are much more strongly damped than in a field perpendicular to the substrate. We consider several mechanisms and conclude that the electron scattering by the magnetic field spatial uctuations plays a main role in the transport properties of a nonplanar 2DEG at low magnetic field.

Gusev G.M.; Quivy A. A.; Leite J.R.; Bykov A. A.; Moshegov N.T.; Kudryashev V.M.; Toropov A.I.; Nastaushev Yu.V.

1999-01-01

200

Comprehensive evidences of octupole vibration in $^{158}Gd$  

CERN Document Server

Comprehensive evidences of the SU(3 limit in the spdf interacting boson model, a dynamical symmetry describing octupole vibration in rotational nucleus, are found in the spectrum, E2 and E1 transition rates, and relative intensities in $^{158}$Gd. This gives a good example of rotational nucleus with octupole vibration in rare-earth region.

Long, G L; Zhao, E G

1999-01-01

 
 
 
 
201

Magnetic field vector retrieval with HMI  

CERN Document Server

The Helioseismic and Magnetic Imager (HMI), on board the Solar Dynamics Observatory (SDO), will begin data acquisition in 2008. It will provide the first full disk, high temporal cadence observations of the full Stokes vector with a 0.5 arc sec pixel size. This will allow for a continuous monitoring of the Solar magnetic field vector. HMI data will advance our understanding of the small and large-scale magnetic field evolution, its relation to the solar and global dynamic processes, coronal field extrapolations, flux emergence, magnetic helicity and the nature of the polar magnetic fields. We summarize HMI's expected operation modes, focusing on the polarization cross-talk induced by the solar oscillations and how this affects the magnetic field vector determinations.

Borrero, J M; Norton, A; Darnell, T; Schou, J; Scherrer, P; Bush, R; Lui, Y

2006-01-01

202

The local Galactic magnetic field  

International Nuclear Information System (INIS)

The Galactic magnetic field is analyzed based on the large amount of pulsar rotation measures (RMs) now available, and regions of the sky suspected of producing anomalous RMs are discussed. The North Polar Spur appears to cause large positive RMs in the region l between 0 and 60 deg and b between 0 and 60 deg, and thus causes a systematic bias in modeling if the pulsars in the region are not flagged. Using only unflagged pulsars within D = 3 kpc and a longitudinal model of the local field, the strength is found to be B(0) = 1.6 + or - 0.3 microgauss in the direction l(B) = 96 deg + or - 4 deg, with a reversal at D(r) = 600 + or - 80 pc toward the inner Galaxy. A concentric-ring model is found to be superior to a bisymmetric spiral model as a fit to the data without the 3 kpc restriction, with a strength of B0 = 1.3 + or - 0.2 microgauss at the position of the sun and a reversal at D(r) = 650 + or - 90 pc toward the Galactic center. 33 refs.

1989-01-01

203

Solar Force-free Magnetic Fields  

Directory of Open Access Journals (Sweden)

Full Text Available The structure and dynamics of the solar corona is dominated by the magnetic field. In most areas in the corona magnetic forces are so dominant that all non-magnetic forces like plasma pressure gradient and gravity can be neglected in the lowest order. This model assumption is called the force-free field assumption, as the Lorentz force vanishes. This can be obtained by either vanishing electric currents (leading to potential fields) or the currents are co-aligned with the magnetic field lines. First we discuss a mathematically simpler approach that the magnetic field and currents are proportional with one global constant, the so-called linear force-free field approximation. In the generic case, however, the relation between magnetic fields and electric currents is nonlinear and analytic solutions have been only found for special cases, like 1D or 2D configurations. For constructing realistic nonlinear force-free coronal magnetic field models in 3D, sophisticated numerical computations are required and boundary conditions must be obtained from measurements of the magnetic field vector in the solar photosphere. This approach is currently of large interests, as accurate measurements of the photospheric field become available from ground-based (for example SOLIS) and space-born (for example Hinode and SDO) instruments. If we can obtain accurate force-free coronal magnetic field models we can calculate the free magnetic energy in the corona, a quantity which is important for the prediction of flares and coronal mass ejections. Knowledge of the 3D structure of magnetic field lines also help us to interpret other coronal observations, e.g., EUV images of the radiating coronal plasma.

Thomas Wiegelmann; Takashi Sakurai

2012-01-01

204

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

205

Magnetic field vector retrieval with the Helioseismic and Magnetic Imager  

CERN Document Server

We investigate the accuracy to which we can retrieve the solar photospheric magnetic field vector using the Helioseismic and Magnetic Imager (HMI) that will fly onboard of the Solar Dynamics Observatory (SDO) by inverting simulated HMI profiles. The simulated profiles realistically take into account the effects of the photon noise, limited spectral resolution, instrumental polarization modulation, solar p modes and temporal averaging. The accuracy of the determination of the magnetic field vector is studied considering the different operational modes of the instrument.

Borrero, J M; Norton, A; Darnell, T; Schou, J; Scherrer, P; Bush, R; Liu, Y

2006-01-01

206

Octupole Correlations and Deformation In Ba, La and Pr  

International Nuclear Information System (INIS)

Stable octupole deformation was predicted and subsequently found to occur centered around the reinforcing shell gaps at Z=56 and N=88 for ?3?0.15. Evidence for stable octupole deformation is reviewed. New results in 145Ba and 141Ba are presented. Rotational enhancement of octupole deformation is found at intermittent spins in Ba and La nuclei and the quenching of such deformation at higher spins in 146Ba but not in 144Ba. Symmetric and asymmetric shapes coexist in 145Ba and 145La. Evidence for octupole correlation is found in 147Pr but only h11/2 bands are found in 149,151Pr. The new 141Ba levels have two sets of two intertwined bands of levels with the characteristics of octupole deformation as found in 143,145Ba, however, a problem occurs with the assignment of parities in 141Ba. (author)

2001-01-01

207

Magnetic Braiding and Parallel Electric Fields  

CERN Multimedia

The braiding of the solar coronal magnetic field via photospheric motions - with subsequent relaxation and magnetic reconnection -- is one of the most widely debated ideas of solar physics. We readdress the theory in the light of developments in three-dimensional magnetic reconnection theory. It is known that the integrated parallel electric field along field lines is the key quantity determining the rate of reconnection, in contrast with the two-dimensional case where the electric field itself is the important quantity. We demonstrate that this difference becomes crucial for sufficiently complex magnetic field structures. A numerical method is used to relax a braided magnetic field to an ideal force-free equilibrium; that equilibrium is found to be smooth, with only large- scale current structures. However, the equilibrium is shown to have a highly filamentary integrated parallel current structure with extremely short length- scales. An analytical model is developed to show that, in a coronal situation, the ...

Wilmot-Smith, A L; Pontin, D I

2008-01-01

208

Protecting SQUID metamaterials against stray magnetic fields  

Science.gov (United States)

Using superconducting quantum interference devices (SQUIDs) as the basic, low-loss elements of thin-film metamaterials has one main advantage: their resonance frequency is easily tunable by applying a weak magnetic field. The downside, however, is a strong sensitivity to stray and inhomogeneous magnetic fields. In this work, we demonstrate that even small magnetic fields from electronic components destroy the collective, resonant behaviour of the SQUID metamaterial. We also show how the effect of these fields can be minimized. As a first step, magnetic shielding decreases any initially present fields, including the earth’s magnetic field. However, further measures such as improvements in the sample geometry have to be taken to avoid the trapping of Abrikosov vortices.

Butz, S.; Jung, P.; Filippenko, L. V.; Koshelets, V. P.; Ustinov, A. V.

2013-09-01

209

Structure of magnetic field in Tokamaks  

International Nuclear Information System (INIS)

[en] Magnetic surfaces, necessary to plasma confinement, can be extinguished by resonant helical perturbations with small intensities due to plasma oscillations or external helical currents. The mapping of magnetic field is obtained intergrating numerically the differential equation of its lines. Criteria which evaluate the chaotic distribution of lines between resonant magnetic islands are presented. (M.C.K.)

1990-01-01

210

Observations of Cool-Star Magnetic Fields  

Directory of Open Access Journals (Sweden)

Full Text Available 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. Our observational picture of cool-star magnetic fields has improved tremendously over the last years. Sophisticated methods were developed to search for the subtle effects of magnetism, which are difficult to detect particularly in cool stars. With an emphasis on the assumptions and capabilities of modern methods used to measure magnetism in cool stars, I review the different techniques available for magnetic field measurements. I collect the analyses on cool-star magnetic fields and try to compare results from different methods, and I review empirical evidence that led to our current picture of magnetic fields and their generation in cool stars and brown dwarfs.

Ansgar Reiners

2012-01-01

211

Magnetic field in Perseus spiral arm  

International Nuclear Information System (INIS)

The rotation measures data for extragalactic radio sources are used to estimate the value and direction of large-scale galactic magnetic field in the Perseus spiral arm. The field of a value of |B| ? 3.2 ?G lies in the galactic plane. It is directed along ? 280 deg in the opposite direction compared to the magnetic field in the local Orion arm. A variance of the field is of the other of ?B/B ? 1.4.

1988-01-01

212

Coronal magnetic fields produced by photospheric shear  

Energy Technology Data Exchange (ETDEWEB)

The magneto-frictional method is used for computing force free fields to examine the evolution of the magnetic field of a line dipole, when there is relative shearing motion between the two polarities. It found that the energy of the sheared field can be arbitrarily large compared with the potential field. It is also found that it is possible to fit the magnetic energy, as a function of shear, by a simple functional form.

Sturrock, P.A.; Yang, W.H.

1987-10-01

213

Coronal magnetic fields produced by photospheric shear  

International Nuclear Information System (INIS)

The magneto-frictional method is used for computing force free fields to examine the evolution of the magnetic field of a line dipole, when there is relative shearing motion between the two polarities. It found that the energy of the sheared field can be arbitrarily large compared with the potential field. It is also found that it is possible to fit the magnetic energy, as a function of shear, by a simple functional form.

1987-01-01

214

Single-layer high field dipole magnets  

Energy Technology Data Exchange (ETDEWEB)

Fermilab is developing high field dipole magnets for post-LHC hadron colliders. Several designs with a nominal field of 10-12 T, coil bore size of 40-50 mm based on both shell-type and block-type coil geometry are currently under consideration. This paper presents a new approach to magnet design, based on simple and robust single-layer coils optimized for the maximum field, good field quality and minimum number of turns.

Vadim V. Kashikhin and Alexander V. Zlobin

2001-07-30

215

Observations of magnetic fields in hot stars  

CERN Multimedia

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

Petit, V

2010-01-01

216

Collective {ital T}- and {ital P}-odd electromagnetic moments in nuclei with octupole deformations  

Energy Technology Data Exchange (ETDEWEB)

Parity and time invariance violating forces produce collective {ital P}- and {ital T}-odd moments in nuclei with static octupole deformation. Collective Schiff moment, electric octupole and dipole, and also magnetic quadrupole appear due to the mixing of rotational levels of opposite parity and can exceed single-particle moments by more than a factor of 100. This enhancement is due to two factors, the collective nature of the intrinsic moments and the small energy separation between members of parity doublets. The above moments induce {ital T}- and {ital P}-odd effects in atoms and molecules. Experiments with such systems may improve substantially the limits on time reversal violation. {copyright} {ital 1996 The American Physical Society.}

Auerbach, N.; Flambaum, V.V.; Spevak, V. [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel)]|[School of Physics, University of New South Wales, Sydney, 2052, New South Wales (Australia)

1996-06-01

217

Electromagnetic radiation in a helical magnetic field  

International Nuclear Information System (INIS)

Electromagnetic radiation spectrum is studied in a helical magnetic field since such magnetic field configurations may be present in cosmic objects. It is shown that, by a proper choice of the spatial period of the magnetic field, one could get large amounts of power over a wide region of the electromagnetic spectrum. The peak in the radiation spectrum shifts toward higher frequencies as the spatial period of the magnetic helix is reduced. As an illustration, this mechanism is applied to the Crab Nebula pulsar NP 0532. 18 references

1984-01-01

218

Electromagnetic radiation in a helical magnetic field  

Energy Technology Data Exchange (ETDEWEB)

Electromagnetic radiation spectrum is studied in a helical magnetic field since such magnetic field configurations may be present in cosmic objects. It is shown that, by a proper choice of the spatial period of the magnetic field, one could get large amounts of power over a wide region of the electromagnetic spectrum. The peak in the radiation spectrum shifts toward higher frequencies as the spatial period of the magnetic helix is reduced. As an illustration, this mechanism is applied to the Crab Nebula pulsar NP 0532. 18 references.

Krishan, V.

1984-01-01

219

Edge magnetic field effect on electron radiation  

International Nuclear Information System (INIS)

[en] The first quantum corrections to ultrarelativistic particle radiation in the ''short'' magnets with arbitrary non-homogeneity field have been found in the paper. A principle possibility to define the beam spin characteristics over circular polarization value of its radiation in edge field of magnetic elements is shown

1980-01-01

220

On the origins of galactic magnetic fields  

CERN Document Server

We present a five dimensional unified theory of gravity and electromagnetism which leads to modified Maxwell equations, suggesting a new origin for galactic magnetic fields. It is shown that a region with nonzero scalar curvature would amplify the magnetic fields under certain conditions.

Borzou, A; Yousefi, R; Ziaie, A H

2009-01-01

 
 
 
 
221

Magnetic Fields and Rotations of Protostars  

CERN Multimedia

The evolution of the magnetic field and angular momentum in the collapsing cloud core is studied using three-dimensional resistive MHD nested grid simulations. Starting with a Bonnor-Ebert isothermal cloud rotating in a uniform magnetic field, we calculate the cloud evolution from the molecular cloud core (n=10^4 cm^-3) to the stellar core (n \\simeq 10^22 cm^-3). The magnetic field strengths at the center of the clouds converge to a certain value as the clouds collapse, when the clouds have the same angular momenta but different strengths of the magnetic fields at the initial state. For 10^12 cm^-3 10^16 cm^-3, because the magnetic field is recoupled with the warm gas. Finally, protostars at their formation epoch have 0.1-1kG of the magnetic fields, which are comparable to observations. The magnetic field strength of protostar slightly depends on the angular momentum of the host cloud. The protostar formed from the slowly rotating cloud core has a stronger magnetic field. The evolution of the angular momentu...

Machida, M N; Matsumoto, T; Machida, Masahiro N.; Inutsuka, Shu-ichiro; Matsumoto, Tomoaki

2007-01-01

222

Field configurations in Helical magnetic wigglers  

Energy Technology Data Exchange (ETDEWEB)

We consider the field configuration produced in a system of two intercalcated concentric coils of radius {ital a} and pitch {Lambda} carrying currents in opposite directions (magnetic wigglers). The magnetic field and vector potential inside are obtained exactly at the coils axis and in a multipole-type expansion off the axis. The effect of finite coils is also considered.

Calvo, M. (Centro de Fisica, Instituto Venezolano de Investigaciones Cientificas, Apartado 21827, Caracas 1020A, Venezuela (VE)); Rendon, O. (Departamento de Fisica, Universidad Simon Bolivar, Apartado Postal 80659, Caracas 1080-A, (Venezuela))

1990-01-01

223

Programming the control of magnetic field measurements  

International Nuclear Information System (INIS)

This paper gives a short review concerning the new NMR probe measurement control system. Then it presents the new program 'CYCLOCHAMP' attached to the magnetic field measurement which also allows to cycle the magnetic field inside the cyclotrons and to equilibrate it among the SSC sectors. (authors)

1998-01-01

224

Magnetic field effects on gas discharge plasmas  

International Nuclear Information System (INIS)

A study of the fluid model for cylindrical weakly ionized quasineutral plasmas in an axial magnetic field is presented. The model takes into account ionization, ion and electron inertia, as well as frictional forces for ions and electrons. The behavior of the plasma parameters for arbitrary magnitudes of the magnetic field, arbitrary gas pressure, and plasma size is presented, making the model applicable for a wide range of discharge conditions. A magnetic field parameter is introduced, which specifies a parameter range for the magnetic field, gas pressure, and plasma size where the Boltzmann equilibrium with the ambipolar field for the electron distribution is satisfied. In addition, a parametric relation for the magnetic field, gas pressure, and plasma size is obtained, which separates the region of weak magnetic field effects from the region of strong magnetic field effects. For strongly magnetized plasmas, an asymptotic solution with nonzero plasma density at the plasma boundary is presented. Analytical approximations for the ionization frequency and the plasma density at the plasma boundary are found for arbitrary external discharge parameters. The theoretical results are supported by numerical computations.

2006-01-01

225

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 th...

Yuhong Fan

226

Magnetic isotope and magnetic field effects on the DNA synthesis.  

UK PubMed Central (United Kingdom)

Magnetic isotope and magnetic field effects on the rate of DNA synthesis catalysed by polymerases ? with isotopic ions (24)Mg(2+), (25)Mg(2+) and (26)Mg(2+) in the catalytic sites were detected. No difference in enzymatic activity was found between polymerases ? carrying (24)Mg(2+) and (26)Mg(2+) ions with spinless, non-magnetic nuclei (24)Mg and (26)Mg. However, (25)Mg(2+) ions with magnetic nucleus (25)Mg were shown to suppress enzymatic activity by two to three times with respect to the enzymatic activity of polymerases ? with (24)Mg(2+) and (26)Mg(2+) ions. Such an isotopic dependence directly indicates that in the DNA synthesis magnetic mass-independent isotope effect functions. Similar effect is exhibited by polymerases ? with Zn(2+) ions carrying magnetic (67)Zn and non-magnetic (64)Zn nuclei, respectively. A new, ion-radical mechanism of the DNA synthesis is suggested to explain these effects. Magnetic field dependence of the magnesium-catalysed DNA synthesis is in a perfect agreement with the proposed ion-radical mechanism. It is pointed out that the magnetic isotope and magnetic field effects may be used for medicinal purposes (trans-cranial magnetic treatment of cognitive deceases, cell proliferation, control of the cancer cells, etc).

Buchachenko AL; Orlov AP; Kuznetsov DA; Breslavskaya NN

2013-09-01

227

Magnetic isotope and magnetic field effects on the DNA synthesis.  

UK PubMed Central (United Kingdom)

Magnetic isotope and magnetic field effects on the rate of DNA synthesis catalysed by polymerases ? with isotopic ions (24)Mg(2+), (25)Mg(2+) and (26)Mg(2+) in the catalytic sites were detected. No difference in enzymatic activity was found between polymerases ? carrying (24)Mg(2+) and (26)Mg(2+) ions with spinless, non-magnetic nuclei (24)Mg and (26)Mg. However, (25)Mg(2+) ions with magnetic nucleus (25)Mg were shown to suppress enzymatic activity by two to three times with respect to the enzymatic activity of polymerases ? with (24)Mg(2+) and (26)Mg(2+) ions. Such an isotopic dependence directly indicates that in the DNA synthesis magnetic mass-independent isotope effect functions. Similar effect is exhibited by polymerases ? with Zn(2+) ions carrying magnetic (67)Zn and non-magnetic (64)Zn nuclei, respectively. A new, ion-radical mechanism of the DNA synthesis is suggested to explain these effects. Magnetic field dependence of the magnesium-catalysed DNA synthesis is in a perfect agreement with the proposed ion-radical mechanism. It is pointed out that the magnetic isotope and magnetic field effects may be used for medicinal purposes (trans-cranial magnetic treatment of cognitive deceases, cell proliferation, control of the cancer cells, etc).

Buchachenko AL; Orlov AP; Kuznetsov DA; Breslavskaya NN

2013-07-01

228

Magnetic field error analysis of a low- $\\beta$ quadrupole magnet  

CERN Multimedia

A good field quality is always requested to achieve for the low- beta quadrupole magnet being used in the accelerator projects. To meet the requirement, people are always managing to reduce the field errors from its magnetic design and construction. In order to obtain a basic understanding for various known multipolar field errors, some calculation evaluations have been performed. Based on the results, the possible origins and corresponding correction methods of the deviation were briefly discussed in the paper. (6 refs).

Qiu, M; Tsuchiya, K; Nakamoto, T; Shintomi, T; Ogitsu, T; Ajima, Y; Yamamoto, A

2002-01-01

229

Origin of Galactic and Extragalactic Magnetic Fields  

CERN Multimedia

A variety of observations suggest that magnetic fields are present in all galaxies and galaxy clusters. These fields are characterized by a modest strength (10^{-7}-10^{-5} G) and huge spatial scale (~Mpc). It is generally assumed that magnetic fields in spiral galaxies arise from the combined action of differential rotation and helical turbulence, a process known as the alpha-omega dynamo. However fundamental questions concerning the nature of the dynamo as well as the origin of the seed fields necessary to prime it remain unclear. Moreover, the standard alpha-omega dynamo does not explain the existence of magnetic fields in elliptical galaxies and clusters. The author summarizes what is known observationally about magnetic fields in galaxies, clusters, superclusters, and beyond. He then reviews the standard dynamo paradigm, the challenges that have been leveled against it, and several alternative scenarios. He concludes with a discussion of astrophysical and early Universe candidates for seed fields.

Widrow, L M

2003-01-01

230

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

231

Control of chaotic magnetic fields in tokamaks  

Scientific Electronic Library Online (English)

Full Text Available 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 works 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.

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

2002-12-01

232

Permanent magnet edge-field quadrupole  

Energy Technology Data Exchange (ETDEWEB)

Planar permanent magnet edge-field quadrupoles for use in particle accelerating machines and in insertion devices designed to generate spontaneous or coherent radiation from moving charged particles are disclosed. The invention comprises four magnetized rectangular pieces of permanent magnet material with substantially similar dimensions arranged into two planar arrays situated to generate a field with a substantially dominant quadrupole component in regions close to the device axis.

Tatchyn, Roman O. (Mountain View, CA)

1997-01-01

233

Control of chaotic magnetic fields in tokamaks  

Directory of Open Access Journals (Sweden)

Full Text Available Chaotic magnetic field lines play an important role in plasma confinement by tokamaks. They can either be generated in the plasma as a result of natural instabilities or artifficially produced by external conductors, like resonant helical windings and ergodic magnetic limiters. This is a review of works 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.

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

2002-01-01

234

Heterotic strings in a uniform magnetic field  

Energy Technology Data Exchange (ETDEWEB)

An exact conformal model representing a constant magnetic field background in heterotic string theory is explicitly solved in terms of free creation/annihilation operators. The spectrum of physical states is examined for different possible embeddings of the magnetic U(1) subgroup. We find that an arbitrarily small magnetic field gives rise to an infinite number of tachyonic excitations corresponding to charged vector states of the massless level and to higher level states with large spins and charges. (orig.).

Russo, J.G. [European Organization for Nuclear Research, Geneva (Switzerland). Theory Div.; Tseytlin, A.A. [Theoretical Physics Group, Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

1995-11-06

235

Magnetic helicity in magnetohydrodynamic turbulence with a mean magnetic field  

International Nuclear Information System (INIS)

A computational investigation of magnetic helicity of the fluctuating magnetic field Hm in ideal and freely decaying three-dimensional (3-D) magnetohydrodynamics (MHD) in the presence of a uniform mean magnetic field is performed. It is shown that for ideal 3-D MHD Hm, which is a rugged invariant in the absence of a mean magnetic field [Frisch et al., J. Fluid Mech. 77, 796 (1975)], decays from its initial value and proceeds to oscillate about zero. The decay of Hm is shown to result from the presence of a new ''generalized'' helicity invariant, which includes contributions from the uniform magnetic field. The loss of invariance of Hm will diminish the effects of inverse transfer of Hm on freely decaying turbulence. This is demonstrated in a discussion of the selective decay relaxation process. copyright 1995 American Institute of Physics.

2077-03-00

236

Structure of the galactic magnetic field  

Energy Technology Data Exchange (ETDEWEB)

The structure of the magnetic field of the Galaxy is investigated on the basis of a statistical analysis of the data on the rotation measures for 176 extragalactic radio sources and 43 pulsars. It is found that the large-scale magnetic field of the Galaxy is parallel to the local spiral arm and has opposite directions in the southern and northern hemispheres. The sun is situated about 70 pc to the south of the surface on which the reversal of the magnetic field takes place. Such a pattern corresponds to a dipole model of the galactic magnetic field. For the southern hemisphere, the magnetic field intensity is found as a function of the distance to the galactic plane.

Andreasian, R.R.

1981-04-01

237

Processing of polymers in high magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

Many organic molecules and polymers have an anisotropic diamagnetic susceptibility, and thus can be aligned in high magnetic fields. The presence of liquid crystallinity allows cooperative motions of the individual molecules, and thus the magnetic energy becomes greater than the thermal energy at experimentally obtainable field strengths. This work has determined the effect of magnetic field alignment on the thermal expansion and mechanical properties of liquid crystalline thermosets in the laboratory. Further advances in magnet design are needed to make magnetic field alignment a commercially viable approach to polymer processing. The liquid crystal thermoset chosen for this study is the diglycidyl ether of dihydroxy-{alpha}-methylstilbene cured with the diamine sulfamilamide. This thermoset has been cured at field strengths up to 18 Tesla.

Douglas, E.P.; Smith, M.E.; Benicewicz, B.C. [Los Alamos National Lab., NM (United States); Earls, J.D.; Priester, R.D. Jr. [Dow Chemical Co., Freeport, TX (United States)

1996-05-01

238

Organic Superconductors at Extremely High Magnetic Fields  

Energy Technology Data Exchange (ETDEWEB)

Intense magnetic fields are an essential tool for understanding layered superconductors. Fundamental electronic properties of organic superconductors are revealed in intense (60 tesla) magnetic fields. Properties such as the topology of the Fermi surface and the nature of the superconducting order parameter are revealed. With modest maximum critical temperatures {approx}13K the charge transfer salt organic superconductors prove to be incredibly valuable materials as their electronically clean nature and layered (highly anisotropic) structures yield insights to the high temperature superconductors. Observation of de Haas-van Alphen and Shubnikov-de Haas quantum oscillatory phenomena, magnetic field induced superconductivity and re-entrant superconductivity are some of the physical phenomena observed in the charge transfer organic superconductors. In this talk, I will discuss the nature of organic superconductors and give an overview of the generation of intense magnetic fields; from the 60 tesla millisecond duration to the extreme 1000 tesla microsecond pulsed magnetic fields.

Mielke, Charles H. (LANL and National High Magnetic Field Laboratory)

2002-02-27

239

Orienting Paramecium with intense static magnetic fields  

Science.gov (United States)

Recent experiments on cell division suggest the application of intense static magnetic fields as a novel tool for the manipulation of biological systems [1]. The magnetic field appears to couple to the intrinsic anisotropies in the diamagnetic components of the cells. Here, we present measurements of the intrinsic average diamagnetic anisotropy of the whole single celled ciliate, Paramecium Caudatum. Magnetic fields, 2.5 T Paramecium Caudatum that were suspended in a density matched medium. The organisms align with their long axis parallel to the applied magnetic field. Their intrinsic diamagnetic anisotropy is 3x10-11 in cgs units. We will discuss the implications of these results for employing magnetic fields to probe the behavior of swimming Paramecium. [1] J. M. Valles, Jr. et al., Expt. Cell Res.274, 112-118 (2002).

Valles, James M., Jr.; Guevorkian, Karine; Quindel, Carl

2004-03-01

240

Materials Processing in Magnetic Fields  

Science.gov (United States)

The latest in lattice QCD -- Quark-gluon plasma physics -- String theory and exact results in quantum field theory -- The status of local supersymmetry.Supersymmetry in nuclei -- Inflation, dark matter, dark energy -- How many dimensions are really compactified? -- Horizons -- Neutrino oscillations physics -- Fundamental constants and their possible time dependence.Highlights from BNL. new phenomena at RHIC -- Highlights from BABAR -- Diffraction studied with a hard scale at HERA -- The large hadron collider: a status report -- Status of non-LHC experiments at CERN -- Highlights from Gran Sass.Fast automatic systems for nuclear emulsion scanning: technique and experiments -- Probing the QGP with charm at ALICE-LHC -- magnetic screening length in hot QCD -- Non-supersymmetric deformation of the Klebanov-Strassler model and the related plane wave theory -- Holographic renormalization made simple: an example -- The kamLAND impact on neutrino oscillations -- Particle identification with the ALIC TOF detector at very high multiplicity -- Superpotentials of N = 1 SUSY gauge theories -- Measurement of the proton structure function F2 in QED compton scattering at HERA -- Yang-Mills effective action at high temperature -- The time of flight (TOF) system of the ALICE experiment -- Almost product manifolds as the low energy geometry of Dirichlet Brane.

Schneider-Muntau, Hans J.; Wada, Hitoshi

 
 
 
 
241

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

2004-01-01

242

A Test for Coronal Magnetic Field Extrapolations  

UK PubMed Central (United Kingdom)

As models for the physical properties of the corona above solar active regionsgrow more sophisticated, we will require better means for testing them. Inthis paper we discuss and apply such a test to a magnetic field model for anactive region. This test is based on the expectation that the temperatures atdifferent points on a given magnetic field line should be well correlated, dueto the rapid transport of heat along field lines in the corona. We use radioobservations of an active region to measure the temperatures on field lines asthey cross two isogauss surfaces (at 430 and 750 G) in the corona. The fieldlines and isogauss surfaces are derived from a coronal magnetic field modelobtained via a nonlinear force--free field extrapolation of a photospheric vectormagnetogram; for comparison, we also investigate a potential--field extrapolationof the same magnetogram. In a region where strongly sheared fields are present,the nonlinear force--free field model does indeed show a go...

Jeongwoo Lee; Stephen M. White; Mukul R. Kundu; A. N. Mcclymont

243

Quark condensate in a magnetic field  

CERN Document Server

We study the dependence of quark condensate $\\Sigma$ on an external magnetic field. For weak fields, it rises linearly with the field. Pion mass and residue are also shifted so that the Gell-Mann - Oakes - Renner relation is satisfied. In the strong field region, $\\Sigma(H) \\propto (eH)^{3/2}$.

Shushpanov, I A

1997-01-01

244

Comparison of adjustable permanent magnetic field sources  

Energy Technology Data Exchange (ETDEWEB)

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

Bjork, R., E-mail: rabj@risoe.dtu.d [Fuel Cells and Solid State Chemistry Division, Riso National Laboratory for Sustainable Energy, Technical University of Denmark - DTU, Frederiksborgvej 399, DK-4000 Roskilde (Denmark); Bahl, C.R.H.; Smith, A.; Pryds, N. [Fuel Cells and Solid State Chemistry Division, Riso National Laboratory for Sustainable Energy, Technical University of Denmark - DTU, Frederiksborgvej 399, DK-4000 Roskilde (Denmark)

2010-11-15

245

Comparison of adjustable permanent magnetic field sources  

Science.gov (United States)

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

Bjørk, R.; Bahl, C. R. H.; Smith, A.; Pryds, N.

2010-11-01

246

Comparison of adjustable permanent magnetic field sources  

DEFF Research Database (Denmark)

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

BjØrk, Rasmus; Bahl, Christian Robert Haffenden

2010-01-01

247

Atoms in extreme strong magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

The discovery of extremly strong magnetic fields up to 10/sup 9/T in compact cosmic objects is responsible for a new chapter in quantum mechanics: ''Matter in extremly strong magnetic fields''. In the presence of such fields the Coulomb-binding-force is dominated by the Lorentz-force, the atoms are strongly deformed to nearly one-dimensional objects, and all properties are anisotropic. The dramatic influence of the magnetic field is demonstrated for the hydrogen atom.

Ruder, H.; Herold, H.; Roesner, W.; Wunner, G.

1983-07-01

248

Charged ellipsoidal bunch in magnetic fields  

International Nuclear Information System (INIS)

[en] The states of a long charged ellipsoidal bunch rotating in the longitudinal uniform magnetic field are studied. Two motion integrals linking the cross-sectional velocities with coordinates, angular rotation velocity and frequency ?H = eH/mc (H - complete magnetic field) are used for the states description. The equations are accounting also for the particles Coulomb pushing apart of the ellipsoidal bunch. The bunch proper longitudinal magnetic field is calculated. The effect of the interaction delay on the state of the long charged rotating bunch is evaluated. The conditions of the dense bunch retention in the external field are obtained

2001-01-01

249

The Humboldt High Magnetic Field Center  

International Nuclear Information System (INIS)

The Humboldt High Magnetic Field Center has moved to a new campus with improved conditions. The three basic kinds of magnetic field generators are DC-superconducting solenoids up to 20 T, nondestructive coils for pulsed fields up to 60 T, and semidestructive/nondestructive single-turn coils up to more than 300/40 T, respectively. The latter variant is especially suitable for repetitive experiments with high dB/dt>107 T/s. The magnetic fields generated, allow, combined with the sophisticated supporting equipment, a great variety of solid-state experiments.

2004-04-30

250

Neutron polarizing magnetic mirror controlled by low magnetic field  

Energy Technology Data Exchange (ETDEWEB)

We have developed multilayer neutron polarizing mirrors controlled under an external magnetic field less than 100 gauss. The multilayers of Permalloy-Ge and Fe-Ge have been evaporated on Si wafers in the magnetic field of about 100 gauss applied parallel to the surface of Si wafer substrate. The polarizing efficiencies of Fe-Ge and Permalloy-Ge multilayers were 95% and 91% under an external magnetic field of 80 gauss. Under an external field of 50 gauss, the polarizing efficiency was 90% in case of Permalloy-Ge polarizing mirror. A neutron pulse was obtained by applying a pulsed magnetic field of about 50 gauss parallel to the Permalloy-Ge multilayer mirror. The pulse risetime is the order of 1 ms in the present instrument. (author).

Kawai, Takeshi; Ebisawa, Tooru; Tasaki, Seiji; Akiyoshi, Tsunekazu [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst.; Eguchi, K.; Hino, Masahiro; Achiwa, Norio

1995-06-01

251

Neutron polarizing magnetic mirror controlled by low magnetic field  

International Nuclear Information System (INIS)

[en] We have developed multilayer neutron polarizing mirrors controlled under an external magnetic field less than 100 gauss. The multilayers of Permalloy-Ge and Fe-Ge have been evaporated on Si wafers in the magnetic field of about 100 gauss applied parallel to the surface of Si wafer substrate. The polarizing efficiencies of Fe-Ge and Permalloy-Ge multilayers were 95% and 91% under an external magnetic field of 80 gauss. Under an external field of 50 gauss, the polarizing efficiency was 90% in case of Permalloy-Ge polarizing mirror. A neutron pulse was obtained by applying a pulsed magnetic field of about 50 gauss parallel to the Permalloy-Ge multilayer mirror. The pulse risetime is the order of 1 ms in the present instrument. (author)

1995-01-01

252

Measurements of the magnetic field of strong field permanent sextupole magnets  

International Nuclear Information System (INIS)

We have fabricated two types of strong field permanent sextupole magnets and measured magnetic field strength and gradient. These magnets can be used for the production of electron-spin polarized atomic beams in newly developed cold atomic beam polarized ion source at Kyushu University. These magnets are composed of 12 segments of permanent magnet (NEOMAX-30). Magnetic field strength of each sextupole magnet was calculated using Halbach's two dimensional formula and analyses of measured field strength were carried out by means of fast fourier transform method (FFT). Higher multipole field components are also evaluated. From the present study we concluded that our experimental data agreed well with theoretical calculations, higher multipole field components do not affect the electron-spin polarized atomic beam trajectory and these sextupole magnets are most suitable for producing high intensity low-temperature (cold) electron-spin polarized atomic beams. (author).

1992-01-01

253

Magnetic monopole field exposed by electrons  

CERN Multimedia

Magnetic monopoles have provided a rich field of study, leading to a wide area of research in particle physics, solid state physics, ultra-cold gases, superconductors, cosmology, and gauge theory. So far, no true magnetic monopoles were found experimentally. Using the Aharonov-Bohm effect, one of the central results of quantum physics, shows however, that an effective monopole field can be produced. Understanding the effects of such a monopole field on its surroundings is crucial to its observation and provides a better grasp of fundamental physical theory. We realize the diffraction of fast electrons at a magnetic monopole field generated by a nanoscopic magnetized ferromagnetic needle. Previous studies have been limited to theoretical semiclassical optical calculations of the motion of electrons in such a monopole field. Solid state systems like the recently studied 'spin ice' provide a constrained system to study similar fields, but make it impossible to separate the monopole from the material. Free space ...

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

2013-01-01

254

Solar Force-free Magnetic Fields  

CERN Multimedia

The structure and dynamics of the solar corona is dominated by the magnetic field. In most areas in the corona magnetic forces are so dominant that all non-magnetic forces like plasma pressure gradient and gravity can be neglected in the lowest order. This model assumption is called the force-free field assumption, as the Lorentz force vanishes. This can be obtained by either vanishing electric currents (leading to potential fields) or the currents are co-aligned with the magnetic field lines. First we discuss a mathematically simpler approach that the magnetic field and currents are proportional with one global constant, the so-called linear force-free field approximation. In the generic case, however, the relation between magnetic fields and electric currents is nonlinear and analytic solutions have been only found for special cases, like 1D or 2D configurations. For constructing realistic nonlinear force-free coronal magnetic field models in 3D, sophisticated numerical computations are required and boundar...

Wiegelmann, Thomas

2012-01-01

255

Magnetic Fields in Noninvasive Brain Stimulation.  

UK PubMed Central (United Kingdom)

The idea that magnetic fields could be used therapeutically arose 2000 years ago. These therapeutic possibilities were expanded after the discovery of electromagnetic induction by the Englishman Michael Faraday and the American Joseph Henry. In 1896, Arsène d'Arsonval reported his experience with noninvasive brain magnetic stimulation to the scientific French community. In the second half of the 20th century, changing magnetic fields emerged as a noninvasive tool to study the nervous system and to modulate neural function. In 1985, Barker, Jalinous, and Freeston presented transcranial magnetic stimulation, a relatively focal and painless technique. Transcranial magnetic stimulation has been proposed as a clinical neurophysiology tool and as a potential adjuvant treatment for psychiatric and neurologic conditions. This article aims to contextualize the progress of use of magnetic fields in the history of neuroscience and medical sciences, until 1985.

Vidal-Dourado M; Conforto AB; Caboclo LO; Scaff M; Guilhoto LM; Yacubian EM

2013-06-01

256

Magnetic-field-controlled reconfigurable semiconductor logic.  

UK PubMed Central (United Kingdom)

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

Joo S; Kim T; Shin SH; Lim JY; Hong J; Song JD; Chang J; Lee HW; Rhie K; Han SH; Shin KH; Johnson M

2013-02-01

257

Temporal Chiral Spiral in Strong Magnetic Fields  

CERN Document Server

Vacuum properties of quantum chromodynamics in strong magnetic and finite electric fields are investigated. We show that when a uniform electric field is instantaneously applied in the parallel direction to a strong magnetic field, it induces temporal oscillation of the chiral and pion condensates. This is a temporal analog to the chiral spiral. The oscillation originates with the propagation of the collective mode, which is protected by the axial anomaly and thus nondissipative.

Hayata, Tomoya; Yamamoto, Arata

2013-01-01

258

Magnetic fields in Local Group dwarf irregulars  

CERN Multimedia

We clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and what is the role of dwarf galaxies in the magnetization of the Universe. We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100m Effelsberg telescope at 2.64 and 4.85GHz. Magnetic fields in LG dwarfs are three times weaker than in the normal spirals (6muG) are observed only in dwarfs of extreme characteristics while typical LG dwarfs are not suitable objects for efficient supply of magnetic fields to the intergalactic medium.

Chyzy, Krzysztof T; Beck, Rainer; Bomans, Dominik J

2011-01-01

259

Strongly interacting matter in magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

Provides a first coherent and introductory account of this new topic. Edited and Authored by leading researchers in the field. Suitable as both self-study text and advanced course material for graduate courses, thematic schools and seminars. The physics of strongly interacting matter in an external magnetic field is presently emerging as a topic of great cross-disciplinary interest for particle, nuclear, astro- and condensed matter physicists. It is known that strong magnetic fields are created in heavy ion collisions, an insight that has made it possible to study a variety of surprising and intriguing phenomena that emerge from the interplay of quantum anomalies, the topology of non-Abelian gauge fields, and the magnetic field. In particular, the non-trivial topological configurations of the gluon field induce a non-dissipative electric current in the presence of a magnetic field. These phenomena have led to an extended formulation of relativistic hydrodynamics, called chiral magnetohydrodynamics. Hitherto unexpected applications in condensed matter physics include graphene and topological insulators. Other fields of application include astrophysics, where strong magnetic fields exist in magnetars and pulsars. Last but not least, an important new theoretical tool that will be revisited and which made much of the progress surveyed in this book possible is the holographic principle - the correspondence between quantum field theory and gravity in extra dimensions. Edited and authored by the pioneers and leading experts in this newly emerging field, this book offers a valuable resource for a broad community of physicists and graduate students.

Kharzeev, Dmitri [State Univ. of New York, Stony Brook, NY (United States). Dept. of Physics; Landsteiner, Karl [Universidad Autonoma de Madrid (Spain). Inst. de Fisica Teorica UAM/CSIC; Schmitt, Andreas [Technische Univ., Vienna (Austria). 1. Inst. fuer Theoretische Physik; Yee, Ho-Ung (eds.) [Illinois Univ., Chicago, IL (United States). Dept. of Physics

2013-08-01

260

The sun and interplanetary magnetic field  

International Nuclear Information System (INIS)

The interplanetary magnetic field (IMF) serves as a link between the sun, the response of the earth to solar activity and variations in galactic cosmic radiation. The IMF originates as a solar-coronal magnetic field that is transported into space by the solar wind. The close connection between solar magnetic fields and the origin and structure of the solar wind is described. The solar wind forms the heliosphere, a cavity containing the magnetized solar plasma from which the interstellar plasma and field are excluded. The entry of galactic cosmic rays into the heliosphere and their strong interaction with the IMF are discussed, this topic being of primary importance to the production and temporal variations of radiogenic elements. The profound influence of the IMF on geomagnetic activity and the aurora is discussed within the context of merging or reconnection with the planetary field. The physical connection is thus established between solar magnetic fields, magnetic storms and aurora. The state of the solar wind and IMF during the Maunder minimum is considered and an explanation for the (relative) absence of sunspots and aurora is proposed. The mechanism is an interruption of the oscillatory solar dynamo, a consequent reduction in the heating of the corona, a cessation of the supersonic solar wind and a weakening or absence of southward-directed magnetic fields in the vicinity of the earth

1991-01-01

 
 
 
 
261

Magnetic Fields in the Early Universe  

CERN Multimedia

This review concerns the origin and the possible effects of magnetic fields in the early Universe. We start by providing to the reader with a short overview of the current state of art of observations of cosmic magnetic fields. We then illustrate the arguments in favour of a primordial origin of magnetic fields in the galaxies and in the clusters of galaxies. We argue that the most promising way to test this hypothesis is to look for possible imprints of magnetic fields on the temperature and polarization anisotropies of the cosmic microwave background radiation (CMBR). With this purpose in mind, we provide a review of the most relevant effects of magnetic fields on the CMBR. A long chapter of this review is dedicated to particle physics inspired models which predict the generation of magnetic fields during the early Universe evolution. Although it is still unclear if any of these models can really explain the origin of galactic and intergalactic magnetic fields, we show that interesting effects may arise any...

Grasso, D; Grasso, D

2001-01-01

262

Toroidal magnetic field simulation by special windings  

International Nuclear Information System (INIS)

Investigated is creation of a field in the volume of a coil of tested section simulating the toroidal field in the tokamak operating section using a compact magnetic system. The calculation results of the system simulating the toroidal magnetic field by special coils for one of the first T-15 construction versions, in which oval superconducting coils are used, are presented. Given is the arrangement scheme of simulating and tested coils, permitting to ensure a rather simple construction of joints and suitable mounting of the tested sections in the simulating system. Parallel arrangement of the simulating system sections reduces costs of the superconducting material and permits to decrease the cryostate dimensions. The gap (40 mm) between the simulating and tested sections is chosen in order to place construction elements and additional windings, simulating pulse magnetic fields of plasma and control windings. The computer code is developed for the BESM-6-type computers and the ES computers using the FORTRAN language. The computer code system is developed for the superconducting coils with linear connection between current and field without magnetizing materials. This system can be used for calculation of magnetic systems of nonsuperconducting materials. The investigation results have shown that the simulating magnetic system with a given degree of accuracy forms in the tokamak operating section the magnetic field which is the same in value and distribution as the field formed by twenty three tokamak sections in the place of the twenty fourth one being absent.

1979-01-01

263

Pulsed field magnets at the United States National High Magnetic Field Laboratory  

Energy Technology Data Exchange (ETDEWEB)

The pulsed field facility of the National High Magnetic Field Laboratory (NHMFL) consists of four components. Now available are (1) explosive driven flux compression, (2) capacitor-driven magnets, and (3) a 20 T superconducting magnet. The fourth component, a 60 T quasi-continuous magnet, has been designed and is scheduled for installation in early 1995. All magnets have He-4 cryostats giving temperatures from room temperature (RT) to 2.2--1.5 K. Dilution refrigerators for the superconducting 20 T magnet and the 50 T pulsed magnet will be installed by early 1994. A wide range of experiments has been completed within the past year.

Campbell, L.J.; Parkin, D.M. [Los Alamos National Lab., NM (United States); Crow, J.E.; Schneider-Muntau, H.J. [Florida State Univ., Tallahassee, FL (United States). NHMFL; Sullivan, N.S. [Univ. of Florida, Gainesville, FL (United States). Dept. of Physics

1993-11-01

264

Magnetic drug targeting: biodistribution and dependency on magnetic field strength  

International Nuclear Information System (INIS)

[en] ''Magnetic drug targeting,'' a model of locoregional chemotherapy showed encouraging results in treatment of VX2-squamous cell carcinoma in rabbits. In the present study we investigated the biokinetic behavior of Iod[123]-labelled ferrofluids in vivo and showed in vitro that the ferrofluid concentration is dependent on the magnetic field strength

2002-01-01

265

Magnetic field considerations in fusion power plant environs  

International Nuclear Information System (INIS)

[en] A summary of magnetic field production mechanisms and effects is given. Discussions are included on the following areas: (1) stray magnetic and electric fields from tokamaks, (2) methods for reducing magnetic fields, (3) economics of magnetic field reductions, (4) forces on magnetizable objects near magnetic confinement fusion reactors, (5) electric field transients in tokamaks, (6) attenuation and decay of electromagnetic fields, and (7) magnetic field transients from tokamak malfunctions

1976-01-01

266

Simultaneous quadrupole and octupole shape phase transitions in Thorium  

CERN Multimedia

The evolution of quadrupole and octupole shapes in Th isotopes is studied in a fully microscopic framework based on nuclear Density Functional Theory. The constrained potential energy maps and observables calculated with microscopic collective Hamiltonians, indicate the occurrence of a simultaneous quantum shape phase transition between spherical and quadrupole-deformed prolate shapes, and between non-octupole and octupole-deformed shapes, as functions of the nucleon number. $^{224}$Th is predicted closest to the critical point of the double phase transition. A microscopic mechanism of this phenomenon is discussed in terms of the evolution of single-nucleon orbitals with deformation.

Li, Z P; Yao, J M; Vretenar, D; Meng, J

2013-01-01

267

Heart - Shaped Nuclei: Condensation of Rotational Aligned Octupole Phonons  

CERN Multimedia

The strong octupole correlations in the mass region $A\\approx 226$ are interpreted as rotation-induced condensation of octupole phonons carrying three units of angular momentum aligned with the rotational axis. The condensation represents a quantum phase transition. Discrete phonon energy and parity conservation generate oscillations of the rotational sequences with positive and negative parity. The phonon condensate co-rotates with quadrupole shape forming a rotating heart shape. The coupling between the quadrupole and octupole modes reaches a maximum in the $N\\approx 136$ isotones, approaching the limit of a static heart shape.

Frauendorf, S

2007-01-01

268

Magnetic field aberration induced by cycle stress  

International Nuclear Information System (INIS)

Magneto-mechanical effect has been causing people's growing interest because of its relevance to several technology problems. One of them is the variation of surface magnetic field induced by stress concentration under the geomagnetic field. It can be used as an innovative, simple and convenient potential NDE method, called as magnetic memory method. However, whether and how this can be used as a quantitative measurement method, is still a virginal research field where nobody sets foot in. In this paper, circle tensile stress within the elastic region was applied to ferromagnetic sample under geomagnetic field. Experiment results on the relation between surface magnetic field and elastic stress were presented, and a simple model was derived. Simulation of the model was reconciled with the experimental results. This can be of great importance for it provides a brighter future for the promising Magnetic Memory NDE method-the potential possibility of quantitative measurement.

2007-01-01

269

Instability of neutron star matter in high magnetic field: constraint on central magnetic field of magnetars  

CERN Multimedia

Pulsars are believed to be magnetized neutron stars. Their surface magnetic field ranges from $10^8$ to $10^{12}$ G. On the other hand, the magnetars have surface magnetic field $10^{14}-10^{15}$ G. It is believed that at center the magnetic field may be higher than that at the surface. However, neutron star can sustain at most the magnetic field $\\sim10^{18}$ G based on dimensional analysis. Within the range of maximum attainable field strength, we study the effect of the magnetic field on the neutron star matter. We model the nuclear matter with relativistic mean field approach considering the possibility of appearance of hyperons at higher density. We find that beyond the magnetic field of the order of $10^{18}$ G, the matter becomes unstable which limits the maximum magnetic field at the center of magnetars. We also find that even at maximum value of magnetic field which is realistic for neutron stars, the effect of magnetic field on highly dense nuclear matter is not so pronounced.

Sinha, Monika

2010-01-01

270

[Working in the magnetic field of ultrahigh field MRI].  

UK PubMed Central (United Kingdom)

Development of magnetic resonance imaging (MRI) device technology continues to increase the static magnetic flux densities applied and consequently leads to considerably increased occupational exposure. This has already made it necessary to review limits of occupational exposure and to postpone European legal regulations for occupational exposure to electromagnetic fields. This raises the question whether and if so which adverse health effects and health risks might be associated with occupational exposure to MRI ultra-high static magnetic fields. Based on a survey on interaction mechanisms recommendations and safety rules are presented to help minimize adverse health effects of emerging ultra-high field MRI.

Leitgeb N; Gombotz H

2013-05-01

271

Hyperon Stars in Strong Magnetic Fields  

CERN Document Server

We investigate the effects of strong magnetic fields on the properties of hyperon stars. The matter is described by a hadronic model with parametric coupling. The matter is considered to be at zero temperature, charge neutral, beta-equilibrated, containing the baryonic octet, electrons and muons. The charged particles have their orbital motions Landau-quantized in the presence of strong magnetic fields (SMF). Two parametrisations of a chemical potential dependent static magnetic field are considered, reaching $1-2 \\times 10^{18}\\,G$ in the center of the star. Finally, the Tolman-Oppenheimer-Volkov (TOV) equations are solved to obtain the mass-radius relation and population of the stars.

Gomes, R O; Vasconcellos, C A Z

2013-01-01

272

The National High Magnetic Field Laboratory  

International Nuclear Information System (INIS)

We describe two of the main user facilities of the National High Magnetic Field Laboratory (NHMFL): (a) the General Purpose DC Field Facility with nine resistive and hybrid magnet stations with continuous fields between 20 and 45 T, and (b) the CIMAR Facilities with 17 spectrometers for the NMR Spectroscopy and Imaging Program, the Fourier Transform ICR Mass Spectrometry Program and the Electron Magnetic Resonance Spectroscopy Program. The facilities are located in Tallahassee, and Gainesville, FL. Members of the worldwide science and engineering communities can access NHMFL facilities, generally without cost, through a peer-reviewed proposal process.

2004-04-30

273

On Color Superconductivity in External Magnetic Field  

CERN Multimedia

We study color superconductivity in external magnetic field. We discuss the reason why the mixing angles in color-flavor locked (CFL) and two-flavor superconductivity (2SC) phases are different despite the fact that the CFL gap goes to the 2SC gap for $m_s \\to \\infty$. Although flavor symmetry is explicitly broken in external magnetic field, we show that all values of gaps in their coset spaces of possible solutions in the CFL phase are equivalent in external magnetic field.

Gorbar, E V

2000-01-01

274

Viscous Bianchi universes with magnetic field  

International Nuclear Information System (INIS)

[en] Measurements of the Faraday rotation of light emitted by extragalactic radio sources suggest the presence of a large scale magnetic field. Bianchi universes are the natural generalizations of the homogeneous and isotropic Friedmann--Robertson--Walker (FRW) models. A flat FRW model is Bianchi type I homogeneous, an open FRW model is type V homogeneous and a closed FRW model is type IX homogeneous. All other Bianchi types are not related to a FRW model. The author gives a review of the consequences for homogeneous universes if we incorporate a magnetic field and a viscous fluid where viscosity is induced by the magnetic field

1988-09-03

275

[Weak magnetic fields and cognitive activity  

UK PubMed Central (United Kingdom)

The influence of natural level of uniform magnetic field (to 200 microT) on Wistar rat cognition was studied in this work. It was found that influence of disturbed Earth magnetic field has caused a long depression of explorative activity only in the presence of information loading. Such depression was removed only after short external stimulation. After this stimulation rats were able to learn by themselves and it took them twice less time than in the control (nootropic effect). It is suggested that a weak magnetic field disturbances may be considered as a negative psychogenic factor which distorts normal conditions for cognitive activity.

Nikol'skaia KA; Shtemler AV; Savonenko AV; Osipov AI; Nikol'ski? SV

1996-07-01

276

[Weak magnetic fields and cognitive activity].  

Science.gov (United States)

The influence of natural level of uniform magnetic field (to 200 microT) on Wistar rat cognition was studied in this work. It was found that influence of disturbed Earth magnetic field has caused a long depression of explorative activity only in the presence of information loading. Such depression was removed only after short external stimulation. After this stimulation rats were able to learn by themselves and it took them twice less time than in the control (nootropic effect). It is suggested that a weak magnetic field disturbances may be considered as a negative psychogenic factor which distorts normal conditions for cognitive activity. PMID:8962888

Nikol'skaia, K A; Shtemler, A V; Savonenko, A V; Osipov, A I; Nikol'ski?, S V

277

Thermal diffusivity measurements in magnetic field  

International Nuclear Information System (INIS)

[en] This paper presents the first observation of thermal diffusivity in magnetic field on superconducting oxides. The measurements are performed on sintered samples using a high resolution a.c. technique from 30 to 120 K in magnetic field up to 7 T. In magnetic field higher than 1 T the thermal diffusivity below the critical temperature decreases and the authors suggest this is due to the scattering between the phonons and the flux lines inside the grains. The cross section ? related to such a scattering is calculated; the authors obtain values from 1 to 7 x 10-7 cm when the temperature increases from 30 to 70 K

1990-01-01

278

Superconducting channel magnets without stray fields  

International Nuclear Information System (INIS)

[en] Superconducting channel magnets without stray fields are developed as injection and extraction elements for the superconducting separated sector cyclotron SuSe. Similar to a coaxial line a channel magnet consists of one or several central conductors surrounded by outer conductors on a closed surface. There always exists a current distribution of the outer conductors, so that the total outside field vanishes except for small stray fields caused by the beam windows. A bended superconducting channel magnet for B = 2T is under construction

1984-01-01

279

Plasma Dynamics in Pulsed Strong Magnetic Fields  

Science.gov (United States)

We describe recent studies of the interaction of fast-rising magnetic fields with multi-species plasmas of densities 10^13-10^15 cm-3. The configurations studied are planar or coaxial gaps, prefilled with plasmas that are driven by 80-400 ns current pulses. The diagnostics is based on time-dependent spectroscopic observations that are spatially resolved in 3D using plasma-doping techniques. The measurements include the magnetic-field structure (from Zeeman splitting), ion velocity distributions (from Doppler profiles), electric fields (from line shapes of allowed and forbidden transitions), and non-Maxwellian electron energy distribution (from line ratios). It is found that the magnetic field propagates in the plasma faster than expected from diffusion. Also, the field spatial distribution is inconsistent with diffusion. The observed broad current channel, as well as non-dependence of the magnetic field evolution on the current polarity, cannot be explained by the available Hall-field theories. Moreover, detailed observations reveal that magnetic field penetration and plasma reflection occur simultaneously, leading to ion-species separation [1, 2], which are also not predicted by Hall-field theories. Measurements of the reflected-proton velocities (twice the magnetic field velocity) show that the protons dissipate a significant fraction of the magnetic field energy. A possible mechanism previously formulated for astrophysical plasmas, based on the formation of small-scale density fluctuations (perhaps as a result of the Rayleigh-Taylor instability) that lead to field penetration via the Hall mechanism, has recently been suggested. The new phenomena observed require novel theoretical treatments. Applications include plasmas under high currents and space physics. 1. A. Weingarten et al., Phys. Rev. Lett. 87, 115004 (2001). 2. R. Arad, et al., Phys. Plasmas 10, 112 (2003).

Maron, Yitzhak

2003-10-01

280

Generation of high magnetic fields using superconducting magnets  

International Nuclear Information System (INIS)

High-field superconducting magnets have opened new frontiers for several kinds of applications, such as fusion reactors, particle accelerators, and nuclear magnetic resonance (NMR) spectrometers. The present record for the highest field in a fully superconducting state is 23.4 T. It was achieved with a combination of NbTi, Nb3Sn, and Bi-2212 conductors in 1999. Since high T c (critical temperature) superconductors (HTS) have sufficiently high critical current density even in excess of 30 T, they are promising for use as high-field superconducting magnets. However, several problems still remain to be resolved for practical applications, and the use of HTS coils will be limited to the inner part of a high-field magnet system in the near future. The required technologies to develop a high-field superconducting magnet with a field of up to 28 T have already been established. Such a magnet is certain to provide information to all leading research areas.

2006-01-01

 
 
 
 
281

Emittance growth in rippled solenoidal magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

Emittance growth results due to accelerating gaps, and magnetic field gaps in induction accelerators. The analytic technique previously used to study electric field induced emittance growth for immersed source beams is extended to include solenoid fringing field effects in the present work. These results have application to industrial induction accelerators and to high brightness Free Electron Laser drivers. 1 ref., 2 figs.

Adler, R.J.

1987-01-01

282

Magnetic Field Estimation Beyond 1/N Scaling  

CERN Multimedia

We propose an atomic magnetometer for which the field estimation uncertainty decreases faster than 1/N with the number of atoms N. Our procedure estimates the magnetic field by observing an optical probe field that is multi-passed through the atomic system during Larmor precession.

Partner, Heather L; Geremia, JM

2007-01-01

283

The CMS Magnetic Field Map Performance  

CERN Multimedia

The Compact Muon Solenoid (CMS) is a general-purpose detector designed to run at the highest luminosity at the CERN Large Hadron Collider (LHC). Its distinctive featuresinclude a 4 T superconducting solenoid with 6 m diameter by 12.5 m long free bore, enclosed inside a 10000-ton return yoke made of construction steel. Accurate characterization of the magnetic field everywhere in the CMS detector is required. During two major tests of the CMS magnet the magnetic flux density was measured inside the coil in a cylinder of 3.448 m diameter and 7 m length with a specially designed field-mapping pneumatic machine as well as in 140 discrete regions of the CMS yoke with NMR probes, 3-D Hall sensors and flux-loops. A TOSCA 3-D model of the CMS magnet has been developed to describe the magnetic field everywhere outside the tracking volume measured with the field-mapping machine. A volume based representation of the magnetic field is used to provide the CMS simulation and reconstruction software with the magnetic field ...

Klyukhin, VI; Sarycheva, L I; Klyukhin, V I; Ball, A; Gaddi, A; Amapane, N; Gerwig, H; Andreev, V; Cure, B; Mulders, M; Loveless, R; Karimaki, V; Popescu, S; Herve, A

2010-01-01

284

Lengthwise field variation in CBA magnets  

Energy Technology Data Exchange (ETDEWEB)

The multipole content of the magnetic field in accelerator superconducting magnets built with a cos theta current distribution inside an iron yoke is determined by the placement of the individual current-carrying turns in the coil, by the location of the coil inside the iron yoke and by the amount of iron saturation at high field. Differences in these parameters cause the multipole content to vary from magnet to magnet leading to possible undesirable effects on beam behavior. Experience has shown that conductor placement errors, due to unavoidable size and placement differences in the conductor and current blocks, are the dominant cause of the observed variation in the multipole content of supposedly identical magnets. These variations were studied in existing magnets in order to see how similar variations might affect the performance of the SSC.

Willen, E.

1984-01-01

285

The rotation-magnetic field relation  

CERN Multimedia

Today, the generation of magnetic fields in solar-type stars and its relation to activity and rotation can coherently be explained, although it is certainly not understood in its entirety. Rotation facilitates the generation of magnetic flux that couples to the stellar wind, slowing down the star. There are still many open questions, particularly at early phases (young age), and at very low mass. It is vexing that rotational braking becomes inefficient at the threshold to fully convective interiors, although no threshold in magnetic activity is seen, and the generation of large scale magnetic fields is still possible for fully convective stars. This article briefly outlines our current understanding of the rotation-magnetic field relation.

Reiners, A; Eislöffel, J; Hallinan, G; Berger, E; Browning, M; Irwin, J; Küker, M; Matt, S

2008-01-01

286

Octupole and hexadecapole bands in 152Sm  

International Nuclear Information System (INIS)

The nucleus 152Sm is characterized by a variety of low-energy collective modes, conventionally described as rotations, ? vibrations and ? vibrations. Recently, it has been suggested that 152Sm is at a critical point between spherical and deformed collective phases. Consequently, 152Sm is being studied by a variety of techniques, including radioactive decay, multi-step Coulomb excitation, in-beam (?, 2n?) ?-ray spectroscopy and (n, n'?) spectroscopy. The present work focuses on the latter two reactions; these have been used to investigate the low-lying bands associated with the octupole degree of freedom, including one built on the first excited 0+ band. In addition, the K? = 4+ hexadecapole vibrational band has been identified.

2005-10-01

287

FEM Computation of Magnetic Fields in Anisotropic Magnetic Materials  

Science.gov (United States)

The magnetic fields in nonlinear anisotropic magnetic materials were analyzed by using the Finite Element Method (FEM). The measured data was directly used in the computation without a complicateded smoothing. The resultant asymmetric linear equations were solved by using the ILUBiCGStab method without symmetrization or the ICCG method with symmetrization. The magnetic flux distributions in a ring core model showed the characteristic patterns according to the non-oriented, grain-oriented and doubly-oriented magnetic properties. The good convergence of the Newton-Raphson nonlinear iteration was attained by the iterative solvers without special techniques for the smoothing.

Kameari, Akihisa; Fujiwara, Koji

288

Evolution of Magnetic Fields in Supernova Remnants  

CERN Document Server

Supernova remnants (SNR) are now widely believed to be a source of cosmic rays (CRs) up to an energy of 1 PeV. The magnetic fields required to accelerate CRs to sufficiently high energies need to be much higher than can result from compression of the circumstellar medium (CSM) by a factor 4, as is the case in strong shocks. Non-thermal synchrotron maps of these regions indicate that indeed the magnetic field is much stronger, and for young SNRs has a dominant radial component while for old SNRs it is mainly toroidal. How these magnetic fields get enhanced, or why the field orientation is mainly radial for young remnants, is not yet fully understood. We use an adaptive mesh refinement MHD code, AMRVAC, to simulate the evolution of supernova remnants and to see if we can reproduce a mainly radial magnetic field in early stages of evolution. We follow the evolution of the SNR with three different configurations of the initial magnetic field in the CSM: an initially mainly toroidal field, a turbulent magnetic fie...

Schure, K M; Achterberg, A; Keppens, R

2008-01-01

289

MRS photodiode in strong magnetic field  

Energy Technology Data Exchange (ETDEWEB)

The experimental results on the performance of the MRS (Metal/Resistor/Semiconductor) photodiode in the strong magnetic field of 4.4T, and the possible impact of the quench of the magnet at 4.5T on sensor's operation are reported.

Beznosko, D.; Blazey, G.; Dyshkant, A.; Francis, K.; Kubik, D.; Rykalin, V.; /Northern Illinois U.; Tartaglia, M.A.; /Fermilab; Zutshi, v.; /Northern Illinois U.

2004-12-01

290

Magnetic field calculation considering the measured hysteresis  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The calculation of magnetic fields is and important part of the electromagnetic device design process. The numerical approach to the consideration of the material hysteresis is shown in the paper. Some problems with shapes of the new magnetization curves are pointed out. The results of the calculati...

Jesenik, Marko; Gori?an, Viktor; Trlep, Mladen; Hamler, Anton; Štumberger, Bojan

291

EIT waves and coronal magnetic field diagnostics  

CERN Multimedia

Magnetic field in the solar lower atmosphere can be measured by the use of the Zeeman and Hanle effects. In contrast, the coronal magnetic field well above the solar surface, which directly controls various eruptive phenomena, can not be precisely measureed with the traditional techniques. Several attempts are being made to probe the coronal magnetic field, such as force-free extrapolation based on the photospheric magnetograms, gyroresonance radio emissions, and coronal seismology based on MHD waves in the corona. Compared to the waves trapped in the localized coronal loops, EIT waves are the only global-scale wave phenomenon, and thus are the ideal tool for the coronal global seismology. In this paper, we review the observations and modelings of EIT waves, and illustrate how they can be applied to probe the global magnetic field in the corona.

Chen, P F

2010-01-01

292

Interaction of Plasmoids with External Magnetic Fields.  

Science.gov (United States)

An attempt is made to give a theoretical description of the interaction of plasmoids with external magnetic fields, considering the plasma nature of the plasmoid, its finite dimensions, and geometry. Equations of longitudinal motion, transverse compressio...

N. A. Khizhnyak B. G. Safronov

1964-01-01

293

Modeling magnetic fields of magnetron sputtering systems  

International Nuclear Information System (INIS)

[en] The strength and direction of magnetic fields of magnetron sputtering systems, including single and multi cathodes, are modeled by computer software based on electromagnetic theories (Maxwell's equations) and finite element analysis. The results of the modeling of magnetic fields are shown to agree closely with the actual measurements of magnetic fields and the resulting target erosion pattern. The pattern of the magnetic field inside the sputtering chamber affects the distribution of plasma density and the substrate bias current density, which, together with the bias potential, determine the film properties. The modeling can be very useful to help in the design and development of new types of magnetron sputtering cathodes and multi-cathode sputtering systems to improve target utilization, sputtering efficiency and properties of deposited films. (orig.)

1991-12-10

294

Heat Capacity Measurements in Pulsed Magnetic Fields  

Energy Technology Data Exchange (ETDEWEB)

The new NHMFL 60T quasi-continuous magnet produces a flat-top field for a period of 100 ms at 60 Tesla, and for longer time at lower fields, e.g. 0.5 s at 45 Tesla. We have developed for the first time the capability to measure heat capacity at very high magnetic fields in the NHMFL 60T quasi-continuous magnet at LANL, using a probe built out of various plastic materials. The field plateau allows us to utilize a heat-pulse method to obtain heat capacity data. Proof-of-principle heat capacity experiments were performed on a variety of correlated electron systems. Both magnet performance characteristics and physical properties of various materials studied hold out a promise of wide application of this new tool.

Jaime, M.; Movshovich, R.; Sarrao, J.L.; Kim, J.; Stewart, G.; Beyermann, W.P.; Canfield, P.C.

1998-10-23

295

A Topology for the Penumbral Magnetic Fields  

CERN Document Server

We describe a scenario for the topology of the magnetic field in penumbrae that accounts for recent observations showing upflows, downflows, and reverse magnetic polarities. According to our conjecture, short narrow magnetic loops fill the penumbral photosphere. Flows along these arched field lines are responsible for both the Evershed effect and the convective transport. This scenario seems to be qualitatively consistent with most existing observations, including the dark cores in penumbral filaments reported by Scharmer et al. Each bright filament with dark core would be a system of two paired convective rolls with the dark core tracing the common lane where the plasma sinks down. The magnetic loops would have a hot footpoint in one of the bright filament and a cold footpoint in the dark core. The scenario fits in most of our theoretical prejudices (siphon flows along field lines, presence of overturning convection, drag of field lines by downdrafts, etc). If the conjecture turns out to be correct, the mild...

Almeida, J Sanchez

2009-01-01

296

Aging beryllium bronze in pulsed magnetic fields  

Science.gov (United States)

Methods of microhardness and X-ray diffraction were used to study the kinetics of changes in the microstructure of the beryllium bronze alloy BrB-2 in the process of decomposition of the supersaturated solid solution in a pulsed magnetic field with a frequency from 0 to 7 Hz at an amplitude of the pulse of 318.4 kA/m, a dc component of the magnetic field equal to 238.8 kA/m, at a temperature of 350°C and annealing duration of 1 h. Frequency dependences of the microhardness, lattice parameter, concentration of beryllium in the residual matrix, size of coherent domains, dislocation density, and relative microdeformations of mosaic blocks in the matrix have been measured upon aging with and without pulse magnetic field. The results of experiments show that the pulse magnetic field substantially affects the parameters of the fine structure and physicomechanical properties of the bronze.

Osinskaya, Yu. V.; Pokoev, A. V.

2008-04-01

297

Circumstellar magnetic fields in Herbig Ae stars  

CERN Multimedia

We present the results of our latest studies of the circumstellar magnetic fields in Herbig Ae stars and briefly discuss the cause of the failure of another recent study by our colleagues to confirm the Zeeman features in our spectra.

Yudin, R V; Hubrig, S; Schöller, M

2007-01-01

298

Magnetic field generation due to resonance absorption  

International Nuclear Information System (INIS)

[en] A detailed study of mechanism of megagauss magnetic field generation in resonant absorption of laser light is presented which takes into account effects of both dissipation and thermal motion of electrons. (auth.)

1975-07-16

299

External magnetic field configurations for EXTRAP  

International Nuclear Information System (INIS)

The strongly inhomogeneous magnetic field for stabilization of a pinch in an Extrap configuration can be created in various ways. Some possibilities both for the linear case and for the toroidal case are discussed. (author)

1982-01-01

300

ATLAS Barrel Toroid magnet reached nominal field  

CERN Multimedia

 On 9 November the barrel toroid magnet reached its nominal field of 4 teslas, with an electrical current of 21 000 amperes (21 kA) passing through the eight superconducting coils as shown on this graph

2006-01-01

 
 
 
 
301

Magnetic Fields in Limb Solar Flares  

Science.gov (United States)

Two limb solar flares, of 14 July 2005 and 19 July 2012, of importance X1.2 and M7.7, are analyzed at present work. Magnetic field strength in named flares are investigated by Stokes I±V profiles of H? and D3 HeI lines. There are direct evidences to the magnetic field inhomogeneity in flares, in particular, non-paralelism of bisectors in I+V and I-V profiles. In some flare places, the local maximums of bisectors splitting were found in both lines. If these bisector splittings are interpreted as Zeeman effect manifestation, the following magnetic field strengths reach up to 2200 G in H? and 1300 G in D3. According to calculations, the observed peculiarities of line profiles may indicate the existence of optically thick emissive small-scale elements with strong magnetic fields and lowered temperature.

Lozitsky, V. G.; Lozitska, N. I.; Botygina, O. A.

2013-02-01

302

End fields of CBA superconducting magnets  

International Nuclear Information System (INIS)

Measurements of the two dimensional harmonic content of the end fields generated by the Brookhaven CBA dipole and quadrupole superconducting magnets are presented. Both the local longitudinal structure and the integrated end effects are examined

1983-01-01

303

Split-Field Magnet facility upgraded  

CERN Multimedia

The Split Field Magnet (SFM) was the largest spectrometer for particles from beam-beam collisions in the ISR. It could determine particle momenta in a large solid angle, but was designed mainly for the analysis of forward travelling particles.As the magnet was working on the ISR circulating beams, its magnetic field had to be such as to restore the correct proton orbit.The SFM, therefore, produced zero field at the crossing point and fields of opposite signs upstream and downstream of it and was completed by 2 large and 2 small compensator magnets. The gradient effects were corrected by magnetic channels equipped with movable flaps. The useful magnetic field volume was 28 m3, the induction in the median plane 1.14 T, the gap heigth 1.1 m, the length 10.5 m, the weight about 1000 ton. Concerning the detectors, the SFM was the first massive application of multiwire proportional chambers (about 70000 wires) which filled the main and the large compensator magnets. In 1976 an improved programme was started with tw...

1977-01-01

304

Electron scattering from the octupole band in 238U  

International Nuclear Information System (INIS)

[en] A simple model for nuclear surface vibrations in permanently deformed nuclei does well in reproducing electron scattering cross sections of rotational levels built on a K/sup ?/= 0- intrinsic octupole vibration in 238U

1978-03-06

305

Ehrenfest force in inhomogeneous magnetic field  

International Nuclear Information System (INIS)

[en] The Ehrenfest force in an inhomogeneous magnetic field is calculated. It is shown that there exist such (very rare) topologically nontrivial physical situations when the Gauss theorem in its classic formulation fails and, as a consequence, apart from the usual Lorentz force an additional, purely imaginary force acts on the charged particle. This force arises only in inhomogeneous magnetic fields of special configurations, has a purely quantum origin, and disappears in the classical limit

2000-01-01

306

Plasma diffusion through multi dipole magnetic fields  

International Nuclear Information System (INIS)

[en] The diffusion of a cold plasma through multi dipole fields of a magnetic picket fence is presented. The ion diffusion and trapping is determined by electric potentials inside the multi dipole fields. The electron diffusion is regulated by an anomalous transport process driven by low frequency fluctuations inside the magnetic sheath. Particles drifting with velocities above the ion acoustic speed generates high amplitude turbulent waves responsible for an anomalous diffusion process. (author)

1992-01-01

307

Magnetic field dissipation in converging flows  

International Nuclear Information System (INIS)

Converging flows (e.g., gas accreting on to compact objects) are often ionized and magnetized. As the gas in these systems compresses towards smaller radii, flux conservation acts to intensify the magnetic field B, which can attain superequipartition values. (Throughout this paper, equipartition is meant to imply a comparison between the energy density in the field and that of the particles only, not including turbulence.) Since such a field probably cannot remain anchored in the gas, it is often assumed that the field intensity in excess of equipartition (i.e., Beq) is dissipated as heat, and that B therefore saturates at its Beq value -the so-called 'equipartition assumption'. In this paper we make an attempt at developing a model for magnetic field dissipation based on resistive magnetic tearing, in order to provide a more realistic means of determining the evolution of B in cases where the contribution to the spectrum from magnetic bremsstrahlung is important. We find that the violation of equipartition can vary in degree from large to small radii, and in either direction. Thus the spectrum predicted on the basis of the equipartition assumption is not always an adequate representation of the actual state of the system. However, several major shortcomings remain in our formulation. For example, our approach in this paper is to consider the turbulence as being initiated primarily by hydrodynamic processes. Arguing that the magnetic field is frozen into the highly ionized plasma, we therefore adopt a magnetic field spatial distribution that mirrors that of the gas. This may be valid Only when the field is subequipartition, for otherwise the turbulent cascade may be influenced primarily by magnetic dissipation, rather than the hydrodynamics

2000-01-01

308

Explosion of soliton in a magnetic field  

Energy Technology Data Exchange (ETDEWEB)

A dynamics of a solitary pulse of the electrostatic ion cyclotron wave that propagates perpendicular to an applied magnetic field is considered. It is shown that the solitary wave will be singular in some range of parameters in the system, such as the plasma density and the magnitude of an applied magnetic field. This fact shows that there is a possibility of controlling the place where explosion of the solitary wave occurs.

Nishinari, K. (Department of Aeronautics, Faculty of Engineering, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113 (Japan)); Abe, K. (College of Arts and Sciences, The University of Tokyo, Komaba 3-8-1, Meguroku, Tokyo 153 (Japan)); Satsuma, J. (Department of Mathematical Sciences, The University of Tokyo, Komaba 3-8-1, Meguroku, Tokyo 153 (Japan))

1994-12-01

309

Explosion of soliton in a magnetic field  

International Nuclear Information System (INIS)

A dynamics of a solitary pulse of the electrostatic ion cyclotron wave that propagates perpendicular to an applied magnetic field is considered. It is shown that the solitary wave will be singular in some range of parameters in the system, such as the plasma density and the magnitude of an applied magnetic field. This fact shows that there is a possibility of controlling the place where explosion of the solitary wave occurs.

1994-01-01

310

An evaluation of Tsyganenko magnetic field model  

International Nuclear Information System (INIS)

[en] A long-standing goal of magnetospheric physics has been to produce a model of the Earth's magnetic field that can accurately predict the field vector at all locations within the magnetosphere for all dipole tilt angles and for various solar wind or magnetic activity conditions. A number of models make such predictions, but some only for limited spatial regions, some only for zero tilt angle, and some only for arbitrary conditions. No models depend explicitly on solar wind conditions. A data set of more than 22,000 vector averages of the magnetosphere magnetic field over 0.5 RE regions is used to evaluate Tsyganenko's 1982 and 1987 magnetospheric magnetic field models. The magnetic field predicted by the model in various regions is compared to observations to find systematic discrepancies which future models might address. While agreement is generally good, discrepancies are noted which include: (1) a lack of adequate field line stretching in the tail and ring current regions; (2) an inability to predict weak enough fields in the polar cusps; and (3) a deficiency of Kp as a predictor of the field configuration

1991-02-01

311

An evaluation of Tsyganenko magnetic field model  

Energy Technology Data Exchange (ETDEWEB)

A long-standing goal of magnetospheric physics has been to produce a model of the Earth's magnetic field that can accurately predict the field vector at all locations within the magnetosphere for all dipole tilt angles and for various solar wind or magnetic activity conditions. A number of models make such predictions, but some only for limited spatial regions, some only for zero tilt angle, and some only for arbitrary conditions. No models depend explicitly on solar wind conditions. A data set of more than 22,000 vector averages of the magnetosphere magnetic field over 0.5 R{sub E} regions is used to evaluate Tsyganenko's 1982 and 1987 magnetospheric magnetic field models. The magnetic field predicted by the model in various regions is compared to observations to find systematic discrepancies which future models might address. While agreement is generally good, discrepancies are noted which include: (1) a lack of adequate field line stretching in the tail and ring current regions; (2) an inability to predict weak enough fields in the polar cusps; and (3) a deficiency of Kp as a predictor of the field configuration.

Fairfield, D.H. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

1991-02-01

312

Static plasma confinement by harmonic magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

A new class of magnetic fields, deduced from the extension of force-free fields to the complex domain, is presented. The compatibility of such kind of fields with the magnetic diffusion equation for harmonic fields, in absence of plasma flow velocity, is shown. This allows to produce a static Lorentz force density in a resistive plasma and possibly to balance pressure forces in the momentum equation. An explicit example of equilibrium solution for a cylindrical plasma column with scalar pressure is presented and its connections with previous experimental results are discussed. Some discussion is also devoted to the question of the existence of this kind of closed equilibria. (author)

Clemente, R.A. [Univ. Estadual de Campinas, Inst. de Fisica Gleb Wataghin, Campinas, SP (Brazil); Tessarotto, M.

1998-01-01

313

Electric and magnetic fields in cryopreservation.  

UK PubMed Central (United Kingdom)

Electromagnetic warming has a long history in cryobiology as a preferred method for recovering large tissue masses from cryopreservation, especially from cryopreservation by vitrification. It is less well-known that electromagnetic fields may be able to influence ice formation during cryopreservation by non-thermal mechanisms. Both theory and published data suggest that static and oscillating electric fields can respectively promote or inhibit ice formation under certain conditions. Evidence is less persuasive for magnetic fields. Recent claims that static magnetic fields smaller than 1 mT can improve cryopreservation by freezing are specifically questioned.

Wowk B

2012-06-01

314

A Penning trap with radial magnetic field  

International Nuclear Information System (INIS)

A radial inhomogeneous magnetic field produced by counter-propagating currents in anti-Helmholtz configuration coils has been superimposed to a Penning trap. The confinement properties of electrons in such a trap have been studied experimentally. Without the radial B-field we find a number of operating conditions where instabilities occur, arising from higher order contributions to the quadrupolar trapping field. When we apply the radial field the trap properties remain essentially unchanged until the strength of this field at the boundary of the electron cloud is of the same order as the homogeneous Penning field. Then a sudden breakdown in the confinement appears. The experiments have been performed in low magnetic fields. The equations of motions of the trapped particles can be cast in a dimensionless form and our results can be considered as independent of the field strength.

2007-01-01

315

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

316

Helical Fields Possessing Mean Magnetic Wells  

International Nuclear Information System (INIS)

Recently Furth and Rosenbluth pointed out that a particular magnetic field having helical symmetry could provide a mean magnetic well, that is provide regions in which ?d?/B decreases away from a magnetic axis (or equivalently a region in which V'' is negative). In this paper we examine helical fields in general and the circumstances in which they may exhibit the negative V'' property. This investigation is made possible by the use of the stream function formalism which provides a simple picture of the field geometry, The existence of negative V'' is related to the topology of the magnetic surfaces which in turn is connected with the positions of the stationary points of the stream function ?. Detailed calculations are given of the shape of the flux surfaces and of the shape of the magnetic well (the variation of ?d?/B across it) for several examples of helical fields. These include the Furth-Rosenbluth configuration and a new configuration which provides a mean magnetic well without the necessity for a central conductor. A survey is also made of the magnetic well properties of these two classes of helical field in terms of two simple criteria: (1) the ratio Q of the field strength on the axis and on the separatrix (which provides an estimate of the overall well depth); and (2) the value of V'' on the magnetic axis (which provides a measure of the ''curvature'' of the well). This latter quantity is calculated analytically by using a general expression for the value of V'' on an arbitrary magnetic axis; It is pointed out that Q alone does not provide a realistic indication of the well shape. (author)

1966-01-01

317

New electric field in asymmetric magnetic reconnection.  

UK PubMed Central (United Kingdom)

We present a theory and numerical evidence for the existence of a previously unexplored in-plane electric field in collisionless asymmetric magnetic reconnection. This electric field, dubbed the "Larmor electric field," is associated with finite Larmor radius effects and is distinct from the known Hall electric field. Potentially, it could be an important indicator for the upcoming Magnetospheric Multiscale mission to locate reconnection sites as we expect it to appear on the magnetospheric side, pointing earthward, at the dayside magnetopause reconnection site.

Malakit K; Shay MA; Cassak PA; Ruffolo D

2013-09-01

318

Earth magnetic field effects on Swarm electric field instrument  

Science.gov (United States)

Earth magnetic field effects on the particle sensors carried by the Swarm satellites are investigated using particle in cell (PIC) and test-particle modelling. In the reference frame of the spacecraft in which plasma flows at relative velocity v?, Earth magnetic field leads to an ambient electric field E?=-v?×B?, which affects the shape of particle distribution functions at the particle sensors. This in turn impacts the distribution of particle fluxes on the microchannel plate (MCP) in the ram face mounted thermal ion imagers (TIIs). Shifts in the centroid of these distributions depend on the direction and magnitude of the local magnetic field and, as such, are expected to vary periodically along the spacecraft orbit. The magnitude of these shifts is estimated quantitatively, and the effect of their variation on the calibration and interpretation of the electric field instrument (EFI) are also discussed.

Rehman, S.; Burchill, J.; Eriksson, A.; Marchand, R.

2012-12-01

319

Critical Magnetic Field Determination of Superconducting Materials  

Energy Technology Data Exchange (ETDEWEB)

Superconducting RF technology is becoming more and more important. With some recent cavity test results showing close to or even higher than the critical magnetic field of 170-180 mT that had been considered a limit, it is very important to develop a way to correctly measure the critical magnetic field (H{sup RF}{sub c}) of superconductors in the RF regime. Using a 11.4 GHz, 50-MW, <1 {mu}s, pulsed power source and a TE013-like mode copper cavity, we have been measuring critical magnetic fields of superconductors for accelerator cavity applications. This device can eliminate both thermal and field emission effects due to a short pulse and no electric field at the sample surface. A model of the system is presented in this paper along with a discussion of preliminary experimental data.

Canabal, A.; Tajima, T.; /Los Alamos; Dolgashev, V.A.; Tantawi, S.G.; /SLAC; Yamamoto, T.; /Tsukuba, Natl. Res. Lab. Metrol.

2011-11-04

320

Magnetic Field Evolution During Neutron Star Recycling  

CERN Document Server

I describe work on two aspects of magnetic field evolution relevant for the "recycling" scenario for making millisecond radio pulsars. First, many of the theoretical ideas for bringing about accretion-induced field decay rely on dissipation of currents in the neutron star crust. I discuss field evolution in the crust due to the Hall effect, and outline when it dominates Ohmic decay. This emphasises the importance of understanding the impurity level in the crust. Second, I briefly discuss the progress that has been made in understanding the magnetic fields of neutron stars currently accreting matter in low mass X-ray binaries. In particular, thermonuclear X-ray bursts offer a promising probe of the magnetic field of these neutron stars.

Cumming, A

2004-01-01

 
 
 
 
321

Explosive plasma expansion in strong magnetic field  

Science.gov (United States)

Experiments to investigate the interaction of a laser-produced-plasma with a strong magnetic field showed the formation of a dynamic boundary layer with high density gradient at the plasma-field interface.[1,2] The shape of the expansion is explained by 3D-ideal-MHD modeling, but kinetic effects are found to be important in understanding the shock penetration in the strong field region. Follow-up experiments using a higher intensity laser and stronger magnetic field will allow control of the plasma collisionality and magnetization in the plasma-field interaction region. These laboratory experiments will achieve conditions relevant to plasma astrophysics interactions. Experimental results and several new experimental concepts will be presented. [1] R. Presura et al., ApSS 299, 299-303 (2005) [2] W. Horton et al., Advances in Space Research, In Press, 2005

Presura, R.

2005-10-01

322

Asymptotic freedom in strong magnetic fields.  

UK PubMed Central (United Kingdom)

Perturbative gluon exchange interaction between quark and antiquark, or in a 3q system, is enhanced in a magnetic field and may cause vanishing of the total qq[over ¯] or 3q mass, and even unlimited decrease of it-recently called the magnetic collapse of QCD. The analysis of the one-loop correction below shows a considerable softening of this phenomenon due to qq[over ¯] loop contribution, similar to the Coulomb case of QED, leading to approximately logarithmic damping of gluon exchange interaction (?O(1/ln|eB|)) at large magnetic field.

Andreichikov MA; Orlovsky VD; Simonov YA

2013-04-01

323

Octupole response and stability of spherical shape in heavy nuclei  

Energy Technology Data Exchange (ETDEWEB)

The isoscalar octupole response of a heavy spherical nucleus is analyzed in a semiclassical model based on the linearized Vlasov equation. The octupole strength function is evaluated with different degrees of approximation. The zero-order fixed-surface response displays a remarkable concentration of strength in the 1{Dirac_h}{omega} and 3{Dirac_h}{omega} regions, in excellent agreement with the quantum single-particle response. The collective fixed-surface response reproduces both the high- and low-energy octupole resonances, but not the low-lying 3{sup -} collective states, while the moving-surface response function gives a good qualitative description of all the main features of the octupole response in heavy nuclei. The role of triangular nucleon orbits, that have been related to a possible instability of the spherical shape with respect to octupole-type deformations, is discussed within this model. It is found that, rather than creating instability, the triangular trajectories are the only classical orbits contributing to the damping of low-energy octupole excitations.

Abrosimov, V.I.; Davidovskaya, O.I.; Dellafiore, A. E-mail: della@fi.infn.it; Matera, F

2003-11-17

324

Octupole response and stability of spherical shape in heavy nuclei  

International Nuclear Information System (INIS)

The isoscalar octupole response of a heavy spherical nucleus is analyzed in a semiclassical model based on the linearized Vlasov equation. The octupole strength function is evaluated with different degrees of approximation. The zero-order fixed-surface response displays a remarkable concentration of strength in the 1?? and 3?? regions, in excellent agreement with the quantum single-particle response. The collective fixed-surface response reproduces both the high- and low-energy octupole resonances, but not the low-lying 3- collective states, while the moving-surface response function gives a good qualitative description of all the main features of the octupole response in heavy nuclei. The role of triangular nucleon orbits, that have been related to a possible instability of the spherical shape with respect to octupole-type deformations, is discussed within this model. It is found that, rather than creating instability, the triangular trajectories are the only classical orbits contributing to the damping of low-energy octupole excitations.

2003-11-17

325

Near equipment magnetic field verification and scaling  

Science.gov (United States)

Magnetic field measurements are essential to the success of many scientific space missions. Outside of the Earth's magnetic field the biggest potential source of magnetic field contamination of these measurements is emitted by the spacecraft. Spacecraft magnetic cleanliness is enforced through the application of strict ground verification requirements for spacecraft equipment and instruments. Due to increasingly strict AC magnetic field requirements, many spacecraft units cannot be verified on the ground using existing techniques. These measurements must instead be taken close to the equipment under test (EUT) and then extrapolated. A traditional dipole power law of -3 (with a field fall-off proportional to r-3) cannot be applied at these close distances without risk of underestimating the field emitted by the EUT, but we demonstrate that a power law of -2 is too conservative. We propose a compromise that uses a power law of -2 up to a distance equal to 3 times the unit size, beyond which a dipole power law can be applied. When extrapolating from a distance of 0.20 to 1.00 m from the centre of a 0.20 m wide EUT, we demonstrate that this method avoids an underprediction of the field, and is at least twice as accurate as performing the extrapolation with a fixed power law of -2.

Pudney, M. A.; Carr, C. M.; Schwartz, S. J.; Howarth, S. I.

2013-07-01

326

Magnetization hysteresis of magnetic nanoclusters V15 in a swept magnetic field  

International Nuclear Information System (INIS)

[en] Magnetization hysteresis of superparamagnetic systems in a swept magnetic field has been investigated. The consideration was made in the framework of the model based on non-equilibrium properties of superparamagnetic systems, namely on the difference in spin and lattice temperatures that appears in alternating magnetic field. The temperature of the spin subsystem and consequently, the magnetization of the sample are shown to 'lag' systematically from alternating magnetic field. This fact can cause the magnetization hysteresis observed. The results of the calculation are compared with experimental data

2003-01-01

327

The Magnetic Field of Solar Spicules  

CERN Multimedia

Determining the magnetic field of solar spicules is vital for developing adequate models of these plasma jets, which are thought to play a key role in the thermal, dynamic, and magnetic structure of the chromosphere. Here we report on magnetic spicule properties in a very quiet region of the off-limb solar atmosphere, as inferred from new spectropolarimetric observations in the HeI 10830 A triplet. We have used a novel inversion code for Stokes profiles caused by the joint action of atomic level polarization and the Hanle and Zeeman effects (HAZEL) to interpret the observations. Magnetic fields as strong as 40G were unambiguously detected in a very localized area of the slit, which may represent a possible lower value of the field strength of organized network spicules.

Centeno, R; Ramos, A Asensio

2009-01-01

328

Magnetic Fields in Molecular Cloud Cores  

CERN Document Server

Observations of magnetic field strengths imply that molecular cloud fragments are individually close to being in a magnetically critical state, even though both magnetic field and column density measurements range over two orders of magnitude. The turbulent pressure also approximately balances the self-gravitational pressure. These results together mean that the one-dimensional velocity dispersion $\\sigv$ is proportional to the mean \\Alf speed of a cloud $\\va$. Global models of MHD turbulence in a molecular cloud show that this correlation is naturally satisfied for a range of different driving strengths of the turbulence. For example, an increase of turbulent driving causes a cloud expansion which also increases $\\va$. Clouds are in a time averaged balance but exhibit large oscillatory motions, particularly in their outer rarefied regions. We also discuss models of gravitational fragmentation in a sheet-like region in which turbulence has already dissipated, including the effects of magnetic fields and ion-n...

Basu, S

2004-01-01

329

Variable-field permanent magnet dipole  

Energy Technology Data Exchange (ETDEWEB)

A new concept for a variable-field permanent-magnet dipole (VFPMD) has been designed, fabricated, and tested at Los Alamos. The VFPMD is a C-shaped sector magnet with iron poles separated by a large block of magnet material (SmCo). The central field can be continuously varied from 0.07 T to 0.3 T by moving an iron shunt closer or further away from the back of the magnet. The shunt is specially shaped to make the dependence of the dipole field strength on the shunt position as linear as possible. The dipole has a 2.8 cm high by 8 cm wide aperture with {approximately}10 cm long poles.

Barlow, D.B.; Kraus, R.H. Jr.; Meyer, R.E.

1993-10-01

330

Magnetization process of spin ice in a [111] magnetic field  

CERN Multimedia

Spin ice in a magnetic field in the [111] direction displays two magnetization plateaux, one at saturation and an intermediate one with finite entropy. We study the crossovers between the different regimes from a point of view of (entropically) interacting defects. We develop an analytical theory for the nearest-neighbor spin ice model, which covers most of the magnetization curve. We find that the entropy is non-monotonic, exhibiting a giant spike between the two plateaux. This regime is described by a monomer-dimer model with tunable fugacities. At low fields, we develop an RG treatment for the extended string defects, and we compare our results to extensive Monte Carlo simulations. We address the implications of our results for cooling by adiabatic (de)magnetization.

Isakov, S V; Moessner, R; Sondhi, S L

2004-01-01

331

The Magnetic Field of beta Coronae Borealis.  

Science.gov (United States)

Measurements of resolved Zeeman patterns in the spectrum of Beta CrB show that /H(s)/, the mean surface magnetic field, varies approximately 180 degrees out of phase with the longitudinal component of the field H(e). The maximum observed /H(s)/ is about 5...

S. C. Wolff R. J. Wolff

1969-01-01

332

Magnetic Fields in the Early Universe  

Energy Technology Data Exchange (ETDEWEB)

Magnetic fields are present everywhere: Earth, other planets, stars, galaxies, galaxy clusters and probably all over the Universe. They extend over kiloparsecs and more, with constant amplitude and direction, and they have tangled components as well. When and how were they created, can we understand the mechanisms, do they influence particle physics, how stable are these fields?

Rubinstein, Hector (Stockholm University)

2004-01-14

333

Source of the earth's magnetic field  

International Nuclear Information System (INIS)

[en] 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

334

Magnetic-field decay and pulsar cooling  

Energy Technology Data Exchange (ETDEWEB)

If pulsar magnetic fields decay with a time constant of proportional 10/sup 6/ years as suggested by measurements of pulsar periods and their time derivatives, then the contribution of the field decay in the form of Ohmic losses to the overall photon luminosity of a pulsar might not be negligible if the age of the pulsar exceeds proportional 10/sup 5/ years.

Lodenquai, J.F. (West Indies Univ., Mona (Jamaica). Dept. of Physics)

1984-09-22

335

The Magnetic Field in the Convection Zone  

CERN Multimedia

One of the key questions in solar physics that remains to be answered concerns the strength and the distribution of the magnetic fields at the base of the convection zone. The flux tube dynamics requires that toroidal fields of strength as large as 100 kilogauss be present at the base of the convection zone. The kinetic-magnetic equipartition argument leads to smaller field strengths. For possible detection of these relatively small (compared to pressure effects) fields by helioseismic methods it is important to know the range of the field strengths and their distribution. We estimate a range for the toroidal magnetic field strengths at the base of the convection zone using dynamo simulations in a spherical shell. These simulations involve the distribution of rotation provided by helioseismic inversions of the GONG and MDI data. Combining the simulations with the observed line-of-sight surface poloidal field we extract the spatial pattern and magnitude of the mean toroidal magnetic field at the base of the co...

Bigazzi, A; Bigazzi, Alberto; Ruzmaikin, Alexander A.

2002-01-01

336

Magnetic relaxation of superconducting YBCO samples in weak magnetic fields  

CERN Multimedia

For the first time, magnetization of high-Tc samples with different crystalline structure and its isothermal relaxation is studied at very weak constant fields (H <= 0.1 Oe) for temperatures close to the critical ones. Essential influence of twin boundaries in YBCO single crystals on magnetic relaxation rate is shown. An estimation of effective pinning potential is made in the framework of the collective pinning model.

Timofeev, V P

2005-01-01

337

Hyperon bulk viscosity in strong magnetic fields  

CERN Multimedia

We study bulk viscosity in neutron star matter including $\\Lambda$ hyperons in the presence of quantizing magnetic fields. Relaxation time and bulk viscosity due to both the non-leptonic weak process involving $\\Lambda$ hyperons and the direct Urca (dUrca) process are calculated here. In the presence of a strong magnetic field, bulk viscosity coefficients are enhanced when protons, electrons and muons are populated in their respective zeroth Landau levels compared with the field free cases. The enhancement of bulk viscosity coefficient is larger for the dUrca case.

Sinha, Monika

2008-01-01

338

Nonperturbative Physics in a Magnetic Field  

CERN Multimedia

Non-Perturbative Quantum Field Theory has played an important role in the study of phenomena where a fermion condensate can appear under certain physical conditions. The familiar phenomenon of electric superconductivity, the color superconductivity of very dense quark matter, and the chiral symmetry breaking of low energy effective chiral theories are all examples of that sort. Often one is interested in the behavior of these systems in the presence of an external magnetic field. In this talk I will outline the effects of an external magnetic field on theories with either fermion-fermion or fermion-antifermion condensates.

de la Incera, Vivian

2010-01-01

339

Measurement of gradient magnetic field temporal characteristics  

Energy Technology Data Exchange (ETDEWEB)

We describe a technique of measuring the time dependence and field distortions of magnetic fields due to eddy currents (EC) produced by time-dependent magnetic field gradients. The EC measuring technique makes use of a large volume sample and selective RF excitation pulses and free induction decay (FID) (or a spin or gradient echo) to measure the out-of-phase component of the FID, which is proportional to {gamma}{delta}B, i.e. the amount the signal is off resonance. The measuring technique is sensitive, easy to implement and interpret, and used for determining pre-emphasis compensation parameters. 8 refs, 7 figs, 1 tab.

Bartusek, K.; Jflek, B. [Czech Academy of Sciences, Inst. of Scientific Instruments, Brno (Czech Republic)

1994-12-31

340

Measurement of gradient magnetic field temporal characteristics  

International Nuclear Information System (INIS)

[en] We describe a technique of measuring the time dependence and field distortions of magnetic fields due to eddy currents (EC) produced by time-dependent magnetic field gradients. The EC measuring technique makes use of a large volume sample and selective RF excitation pulses and free induction decay (FID) (or a spin or gradient echo) to measure the out-of-phase component of the FID, which is proportional to ??B, i.e. the amount the signal is off resonance. The measuring technique is sensitive, easy to implement and interpret, and used for determining pre-emphasis compensation parameters

1994-01-01

 
 
 
 
341

Magnetic fields during high redshift structure formation  

CERN Document Server

We explore the amplification of magnetic fields in the high-redshift Universe. For this purpose, we perform high-resolution cosmological simulations following the formation of primordial halos with \\sim10^7 M_solar, revealing the presence of turbulent structures and complex morphologies at resolutions of at least 32 cells per Jeans length. Employing a turbulence subgrid-scale model, we quantify the amount of unresolved turbulence and show that the resulting turbulent viscosity has a significant impact on the gas morphology, suppressing the formation of low-mass clumps. We further demonstrate that such turbulence implies the efficient amplification of magnetic fields via the small-scale dynamo. We discuss the properties of the dynamo in the kinematic and non-linear regime, and explore the resulting magnetic field amplification during primordial star formation. We show that field strengths of \\sim10^{-5} G can be expected at number densities of \\sim5 cm^{-3}.

Schleicher, Dominik R G; Schober, Jennifer; Schmidt, Wolfram; Bovino, Stefano; Federrath, Christoph; Niemeyer, Jens; Banerjee, Robi; Klessen, Ralf S

2012-01-01

342

Electric breakdown potentials under longitudinal magnetic fields  

International Nuclear Information System (INIS)

A study of a DC ionization potential with longitudinal magnetic fields in a parallel plate configuration is presented. A variation of the well known Paschen curve is studied for two different separation distances (2.0 and 6.7 cm) between the electrodes; more than orders of magnitude in pressures (1.4 x 10-2 to 40 mbar); and magnetic fields up to 250 Gauss. The differences between the curves with and without B field are explained by the fluid model only by means of perpendicular mobility (?) and diffusion (D) coefficients, cyclotron frequencies (?)c), Larmor radii (r-L) and collision frequencies v=?-1 with neutrals, independently of whether they produce ionization or not. Some inversions or crossings of the electric behavior between the right and left branch of different modified Paschen curves are due to the increasing collision frequencies and anomalous coefficients producing lower ionization potentials than the established ones in the absence of magnetic fields. (author)

1998-12-04

343

Helicon plasma in a nonuniform magnetic field  

International Nuclear Information System (INIS)

[en] The distributions of the electron density in a plasma produced by helicon waves and the corresponding wave amplitudes and phases are studied experimentally. The measurements were carried out in an argon plasma at a pressure of 3 mtorr and at an input RF power of up to 600 W. The magnetic field was varied in the range from 0 to 200 G. The efficiency of plasma production in both uniform and nonuniform fields is investigated. It is shown that, in a nonuniform magnetic field, the electron density can be substantially increased (up to 5 x 1012 cm-3) by placing an antenna in the region in which the magnetic field is weaker than in the main plasma

2001-01-01

344

Measuring vector magnetic fields in solar prominences  

CERN Document Server

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

Suárez, D Orozco; Bueno, J Trujillo

2012-01-01

345

Measuring vector magnetic fields in solar prominences  

Science.gov (United States)

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

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

2013-05-01

346

Magnetic nanoparticles for applications in oscillating magnetic field  

Energy Technology Data Exchange (ETDEWEB)

Enzymatic and thermochemical catalysis are both important industrial processes. However, the thermal requirements for each process often render them mutually exclusive: thermochemical catalysis requires high temperature that denatures enzymes. One of the long-term goals of this project is to design a thermocatalytic system that could be used with enzymatic systems in situ to catalyze reaction sequences in one pot; this system would be useful for numerous applications e.g. conversion of biomass to biofuel and other commodity products. The desired thermocatalytic system would need to supply enough thermal energy to catalyze thermochemical reactions, while keeping the enzymes from high temperature denaturation. Magnetic nanoparticles are known to generate heat in an oscillating magnetic field through mechanisms including hysteresis and relaxational losses. We envisioned using these magnetic nanoparticles as the local heat source embedded in sub-micron size mesoporous support to spatially separate the particles from the enzymes. In this study, we set out to find the magnetic materials and instrumental conditions that are sufficient for this purpose. Magnetite was chosen as the first model magnetic material in this study because of its high magnetization values, synthetic control over particle size, shape, functionalization and proven biocompatibility. Our experimental designs were guided by a series of theoretical calculations, which provided clues to the effects of particle size, size distribution, magnetic field, frequency and reaction medium. Materials of theoretically optimal size were synthesized, functionalized, and their effects in the oscillating magnetic field were subsequently investigated. Under our conditions, the materials that clustered e.g. silica-coated and PNIPAM-coated iron oxides exhibited the highest heat generation, while iron oxides embedded in MSNs and mesoporous iron oxides exhibited the least bulk heating. It is worth noting that the specific loss power of PNIPAM-coated Fe{sub 3}O{sub 4} was peculiarly high, and the heat loss mechanism of this material remains to be elucidated. Since thermocatalysis is a long-term goal of this project, we also investigated the effects of the oscillating magnetic field system for the synthesis of 7-hydroxycoumarin-3-carboxylic acid. Application of an oscillating magnetic field in the presence of magnetic particles with high thermal response was found to effectively increase the reaction rate of the uncatalyzed synthesis of the coumarin derivative compared to the room temperature control.

Peeraphatdit, Chorthip

2010-12-15

347

Magnetizing a complex plasma without a magnetic field.  

UK PubMed Central (United Kingdom)

We propose and demonstrate a concept that mimics the magnetization of the heavy dust particles in a complex plasma while leaving the properties of the light species practically unaffected. It makes use of the frictional coupling between a complex plasma and the neutral gas, which allows us to transfer angular momentum from a rotating gas column to a well-controlled rotation of the dust cloud. This induces a Coriolis force that acts exactly as the Lorentz force in a magnetic field. Experimental normal mode measurements for a small dust cluster with four particles show excellent agreement with theoretical predictions for a magnetized plasma.

Kählert H; Carstensen J; Bonitz M; Löwen H; Greiner F; Piel A

2012-10-01

348

Magnetizing a complex plasma without a magnetic field  

CERN Multimedia

We propose and demonstrate a concept that mimics the magnetization of the heavy dust particles in a complex plasma while leaving the properties of the light species practically unaffected. It makes use of the frictional coupling between a complex plasma and the neutral gas, which allows to transfer angular momentum from a rotating gas column to a well-controlled rotation of the dust cloud. This induces a Coriolis force that acts exactly as the Lorentz force in a magnetic field. Experimental normal mode measurements for a small dust cluster with four particles show excellent agreement with theoretical predictions for a magnetized plasma.

Kählert, H; Bonitz, M; Löwen, H; Greiner, F; Piel, A

2012-01-01

349

Coronal magnetic fields produced by photospheric shear  

International Nuclear Information System (INIS)

The magnetofrictional method for computing force-free fields is used to examine the evolution of the magnetic field of a line dipole, when there is relative shearing motion between the two polarities. It is found that the energy of the sheared field can be arbitrarily large compared with the potential field. It is also found that it is possible to fit the magnetic energy, as a function of shear amplitude, by a simple functional form. The fit parameters depend only on the distribution of normal field in the photosphere and the form of the shearing displacement. They show that the energy is relatively more enhanced if the shear occurs: (1) where the normal field is strongest; and/or (2) in the inner region of the dipole, near the axis; and/or (3) over a large fraction of the dipole area. 22 references.

1988-01-01

350

Coronal magnetic fields produced by photospheric shear  

Energy Technology Data Exchange (ETDEWEB)

The magneto-frictional method for computing force-free fields examines the evolution of the magnetic field of a line dipole, when there is relative shearing motion between the two polarities. The energy of the sheared field can be arbitrarily large compared with the potential field. It is possible to fit the magnetic energy, as a function of shear amplitude, by a simple functional form. The fit parameters depend only on the distribution of normal field in the photosphere and the form of the shearing displacement. The energy is relatively more enhanced if the shear occurs: (1) where the normal field is strongest; (2) in the inner region of the dipole, near the axis; or (3) over a large fraction of the dipole area.

Klimchuk, J.A.; Sturrock, P.A.; Yang, W.H.

1988-04-01

351

Coronal magnetic fields produced by photospheric shear  

Energy Technology Data Exchange (ETDEWEB)

The magnetofrictional method for computing force-free fields is used to examine the evolution of the magnetic field of a line dipole, when there is relative shearing motion between the two polarities. It is found that the energy of the sheared field can be arbitrarily large compared with the potential field. It is also found that it is possible to fit the magnetic energy, as a function of shear amplitude, by a simple functional form. The fit parameters depend only on the distribution of normal field in the photosphere and the form of the shearing displacement. They show that the energy is relatively more enhanced if the shear occurs: (1) where the normal field is strongest; and/or (2) in the inner region of the dipole, near the axis; and/or (3) over a large fraction of the dipole area. 22 references.

Klimchuk, J.A.; Sturrock, P.A.; Yang, W.H.

1988-12-01

352

The measurement of magnetic field interference of adjacent to quadrupole magnets of J-PARC RCS  

International Nuclear Information System (INIS)

The magnet of J-PARC Rapid Cycle Synchrotron (RCS) consists of magnets with a large aperture. Therefore influence of magnetic field interference between adjacent magnets must be measured. This is important in order to reduce beam loss. This paper reports the measurement of magnetic field interference between steering or sextupole magnets and quadrupole magnets. (author)

2006-01-01

353

Magnetic helicity in magnetohydrodynamic turbulence with a mean magnetic field  

Energy Technology Data Exchange (ETDEWEB)

A computational investigation of magnetic helicity of the fluctuating magnetic field {ital H}{sub {ital m}} in ideal and freely decaying three-dimensional (3-D) magnetohydrodynamics (MHD) in the presence of a uniform mean magnetic field is performed. It is shown that for ideal 3-D MHD {ital H}{sub {ital m}}, which is a rugged invariant in the absence of a mean magnetic field [Frisch {ital et} {ital al}., J. Fluid Mech. {bold 77}, 796 (1975)], decays from its initial value and proceeds to oscillate about zero. The decay of {ital H}{sub {ital m}} is shown to result from the presence of a new ``generalized`` helicity invariant, which includes contributions from the uniform magnetic field. The loss of invariance of {ital H}{sub {ital m}} will diminish the effects of inverse transfer of {ital H}{sub {ital m}} on freely decaying turbulence. This is demonstrated in a discussion of the selective decay relaxation process. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Stribling, T. [National Research Council, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States); Matthaeus, W.H.; Oughton, S. [Bartol Research Institute, University of Delaware, Newark, Delaware 19716 (United States)

1995-05-01

354

Exact Solution of Noncommutative Field Theory in Background Magnetic Fields  

CERN Document Server

We obtain the exact non-perturbative solution of a scalar field theory defined on a space with noncommuting position and momentum coordinates. The model describes non-locally interacting charged particles in a background magnetic field. It is an exactly solvable quantum field theory which has non-trivial interactions only when it is defined with a finite ultraviolet cutoff. We propose that small perturbations of this theory can produce solvable models with renormalizable interactions.

Langmann, E; Zarembo, K

2003-01-01

355

Magnetic field measurements in xi Bootis A  

International Nuclear Information System (INIS)

Four Zeeman spectrograms from Lick Observatory of xi Boo A and two of iota Peg at 2 A mm-1 have been measured to determine if a weak magnetic field is present in xi Boo A. The results indicate that the field is too weak to be measured by this technique on these spectrograms, although remeasurements of spectrograms from Mauna Kea at 3.4 A mm-1 still give a positive field of 170 gauss. (U.S.)

1975-01-01

356

Electric/magnetic field sensor  

Energy Technology Data Exchange (ETDEWEB)

A UNLV novel electric/magnetic dot sensor includes a loop of conductor having two ends to the loop, a first end and a second end; the first end of the conductor seamlessly secured to a first conductor within a first sheath; the second end of the conductor seamlessly secured to a second conductor within a second sheath; and the first sheath and the second sheath positioned adjacent each other. The UNLV novel sensor can be made by removing outer layers in a segment of coaxial cable, leaving a continuous link of essentially uncovered conductor between two coaxial cable legs.

Schill, Jr., Robert A. (Henderson, NV); Popek, Marc [Las Vegas, NV

2009-01-27

357

Cosmic Magnetic Fields: Observations and Prospects  

CERN Multimedia

Synchrotron emission, its polarization and its Faraday rotation at radio frequencies of 0.2-10 GHz are powerful tools to study the strength and structure of cosmic magnetic fields. The observational results are reviewed for spiral, barred and flocculent galaxies, the Milky Way, halos and relics of galaxy clusters, and for the intergalactic medium. Polarization observations with the forthcoming large radio telescopes will open a new era in the observation of cosmic magnetic fields and will help to understand their origin. At low frequencies, LOFAR (10-250 MHz) will allow us to map the structure of weak magnetic fields in the outer regions and halos of galaxies and galaxy clusters. Polarization at higher frequencies (1-10 GHz), as observed with the EVLA, ASKAP, MeerKAT, APERTIF and the SKA, will trace magnetic fields in the disks and central regions of nearby galaxies in unprecedented detail. Surveys of Faraday rotation measures of pulsars will map the Milky Way's magnetic field with high precision. All-sky sur...

Beck, Rainer

2011-01-01

358

Plasma Equilibria With Stochastic Magnetic Fields  

Science.gov (United States)

Plasma equilibria that include regions of stochastic magnetic fields are of interest in a variety of applications, including tokamaks with ergodic limiters and high-pressure stellarators. Such equilibria are examined theoretically, and a numerical algorithm for their construction is described.^2,3 % The balance between stochastic diffusion of magnetic lines and small effects^2 omitted from the simplest MHD description can support pressure and current profiles that need not be flattened in stochastic regions. The diffusion can be described analytically by renormalizing stochastic Langevin equations for pressure and parallel current j, with particular attention being paid to the satisfaction of the periodicity constraints in toroidal configurations with sheared magnetic fields. The equilibrium field configuration can then be constructed by coupling the prediction for j to Amp'ere's law, which is solved numerically. A. Reiman et al., Pressure-induced breaking of equilibrium flux surfaces in the W7AS stellarator, Nucl. Fusion 47, 572--8 (2007). J. A. Krommes and A. H. Reiman, Plasma equilibrium in a magnetic field with stochastic regions, submitted to Phys. Plasmas. J. A. Krommes, Fundamental statistical theories of plasma turbulence in magnetic fields, Phys. Reports 360, 1--351.

Krommes, J. A.; Reiman, A. H.

2009-05-01

359

Behavior of a Single Langmuir Probe in a Magnetic Field.  

Science.gov (United States)

|Describes an experiment to demonstrate the influence of a magnetic field on the behavior of a single Langmuir probe. The experiment introduces the student to magnetically supported plasma and particle behavior in a magnetic field. (GA)|

Pytlinski, J. T.; And Others

1978-01-01

360

Computing nonlinear force free coronal magnetic fields  

Directory of Open Access Journals (Sweden)

Full Text Available Knowledge of the structure of the coronal magnetic field is important for our understanding of many solar activity phenomena, e.g. flares and CMEs. However, the direct measurement of coronal magnetic fields is not possible with present methods, and therefore the coronal field has to be extrapolated from photospheric measurements. Due to the low plasma beta the coronal magnetic field can usually be assumed to be approximately force free, with electric currents flowing along the magnetic field lines. There are both observational and theoretical reasons which suggest that at least prior to an eruption the coronal magnetic field is in a nonlinear force free state. Unfortunately the computation of nonlinear force free fields is way more difficult than potential or linear force free fields and analytic solutions are not generally available. We discuss several methods which have been proposed to compute nonlinear force free fields and focus particularly on an optimization method which has been suggested recently. We compare the numerical performance of a newly developed numerical code based on the optimization method with the performance of another code based on an MHD relaxation method if both codes are applied to the reconstruction of a semi-analytic nonlinear force-free solution. The optimization method has also been tested for cases where we add random noise to the perfect boundary conditions of the analytic solution, in this way mimicking the more realistic case where the boundary conditions are given by vector magnetogram data. We find that the convergence properties of the optimization method are affected by adding noise to the boundary data and we discuss possibilities to overcome this difficulty.

T. Wiegelmann; T. Neukirch

2003-01-01

 
 
 
 
361

Mechanism of magnetic field effect in cryptochrome  

CERN Multimedia

Creatures as varied as mammals, fish, insects, reptiles, and migratory birds have an intriguing `sixth' sense that allows them to distinguish north from south by using the Earth's intrinsic magnetic field. Yet despite decades of study, the physical basis of this magnetic sense remains elusive. A likely mechanism is furnished by magnetically sensitive radical pair reactions occurring in the retina, the light-sensitive part of the eyes. A photoreceptor, cryptochrome, has been suggested to endow birds with magnetoreceptive abilities as the protein has been shown to exhibit the biophysical properties required for an animal magnetoreceptor to operate properly. Here, we propose a concrete light-driven reaction cycle in cryptochrome that lets a magnetic field influence the signaling state of the photoreceptor. The reaction cycle ties together transient absorption and electron-spin-resonance observations with known facts on avian magnetoreception. Our analysis establishes the feasibility of cryptochrome to act as a g...

Solov'yov, Ilia A

2011-01-01

362

Field-flow fractionation of magnetic particles in a cyclic magnetic field.  

UK PubMed Central (United Kingdom)

Although magnetic field-flow fractionation (MgFFF) is emerging as a promising technique for characterizing magnetic particles, it still suffers from limitations such as low separation efficiency due to irreversible adsorption of magnetic particles on separation channel. Here we report a novel approach based on the use of a cyclic magnetic field to overcome the particle entrapment in MgFFF. This cyclic field is generated by rotating a magnet on the top of the spiral separation channel so that magnetic and opposing gravitational forces alternately act on the magnetic particles suspended in the fluid flow. As a result, the particles migrate transversely between the channel walls and their adsorption at internal channel surface is prevented due to short residence time which is controlled by the rotation frequency. With recycling of the catch-release process, the particles follow saw-tooth-like downstream migration trajectories and exit the separation channel at velocities corresponding to their sedimentation coefficients. A retention model has been developed on the basis of the combined effects of magnetic, gravitational fields and hydrodynamic flow on particle migration. Two types of core-shell structured magnetic microspheres with diameters of 6.04- and 9.40-?m were synthesized and used as standard particles to test the proposed retention theory under varying conditions. The retention ratios of these two types of particles were measured as a function of magnet rotation frequency, the gap between the magnet and separation channel, carrier flow rate, and sample loading. The data obtained confirm that optimum separation of magnetic particles with improved separation efficiency can be achieved by tuning rotation frequency, magnetic field gradient, and carrier flow rate. In view of the widespread applications of magnetic microspheres in separation of biological molecules, virus, and cells, this new method might be extended to separate magnetically labeled proteins or organisms for multiplex analyte identification and purification.

Bi Y; Pan X; Chen L; Wan QH

2011-06-01

363

High magnetic field ohmically decoupled non-contact technology  

Energy Technology Data Exchange (ETDEWEB)

Methods and apparatus are described for high magnetic field ohmically decoupled non-contact treatment of conductive materials in a high magnetic field. A method includes applying a high magnetic field to at least a portion of a conductive material; and applying an inductive magnetic field to at least a fraction of the conductive material to induce a surface current within the fraction of the conductive material, the surface current generating a substantially bi-directional force that defines a vibration. The high magnetic field and the inductive magnetic field are substantially confocal, the fraction of the conductive material is located within the portion of the conductive material and ohmic heating from the surface current is ohmically decoupled from the vibration. An apparatus includes a high magnetic field coil defining an applied high magnetic field; an inductive magnetic field coil coupled to the high magnetic field coil, the inductive magnetic field coil defining an applied inductive magnetic field; and a processing zone located within both the applied high magnetic field and the applied inductive magnetic field. The high magnetic field and the inductive magnetic field are substantially confocal, and ohmic heating of a conductive material located in the processing zone is ohmically decoupled from a vibration of the conductive material.

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

2009-05-19

364

Vector magnetic fields of Solar Granulation  

CERN Document Server

Observations of quiet Sun from the Solar Optical Telescope/Spectro-Polarimeter (SOT/SP) aboard the Hinode spacecraft would reveal the magnetic characters of the solar photosphere. By making use of the deep mode observations of three quiet regions, we have statistically studied the vector magnetic fields of solar granulation. More than 2000 normal granules are manually selected to form a sample. It is recognized that some granules are even darker than the mean photosphere in intensity, and there is a linear correlation between intensity and Doppler velocity in granules. The distributions of longitudinal and transverse apparent magnetic flux densities, Doppler velocity and continuum intensity of granules are obtained, and their unsigned magnetic flux measured. Two approaches are carried out in this study. First we obtained the magnetic properties of granulation by averaging the measurements for all the sampling granules. Secondly, we reconstructed an average granular cell based on a sub-sample, and obtained the...

Jin, Chunlan; Zhao, Meng

2008-01-01

365

SSC collider dipole magnets field angle data  

Energy Technology Data Exchange (ETDEWEB)

In the fabrication of both 40 and 50 mm collider dipole superconducting magnets, surveys of the direction of the magnetic field along their length have been taken. This data besides being used for certifying compliance with the specifications for the finished magnet, yields interesting information on the straightness and rigidity of the coil placement between some stages in their manufacture and testing. A discussion on the measuring equipment and procedures is given. All of the 40 mm magnets that were built or cryostat at Fermilab have at least one of these surveys, and a summary of the data on them is presented. Most of the 50 mm magnets built and cold tested at Fermilab have been surveyed before and after insertion in the cryostat and before and after being cold tested. A summary of this data is also presented.

Kuchnir, M.; Bleadon, M.; Schmidt, E.; Bossert, R.; Carson, J.; Delchamps, S.W.; Gourlay, S.; Hanft, R.; Koska, W.; Lamm, M.J.; Mazur, P.O.; Orris, D.; Ozelis, J.; Strait, J.; Wake, M. [Fermi National Accelerator Lab., Batavia, IL (United States); DiMarco, J.; Devred, A.; Kuzminski, J.; Yu, Y.; Zheng, H. [Superconducting Super Collider Lab., Dallas, TX (United States); Ogitsu, T. [Superconducting Super Collider Lab., Dallas, TX (United States)]|[KEK, National Lab. for High Energy Physics, Tsukuba, Ibaraki (Japan)

1992-09-01

366

SSC collider dipole magnets field angle data  

International Nuclear Information System (INIS)

In the fabrication of both 40 and 50 mm collider dipole superconducting magnets, surveys of the direction of the magnetic field along their length have been taken. This data besides being used for certifying compliance with the specifications for the finished magnet, yields interesting information on the straightness and rigidity of the coil placement between some stages in their manufacture and testing. A discussion on the measuring equipment and procedures is given. All of the 40 mm magnets that were built or cryostat at Fermilab have at least one of these surveys, and a summary of the data on them is presented. Most of the 50 mm magnets built and cold tested at Fermilab have been surveyed before and after insertion in the cryostat and before and after being cold tested. A summary of this data is also presented.

1992-01-01

367

Equilibrium magnetization states in magnetic nanotubes and their evolution in external magnetic field  

Science.gov (United States)

The equilibrium magnetization states existing in soft magnetic nanotubes and their behavior in external magnetic field are investigated by means of micromagnetic simulation. In the ground state the middle part of a sufficiently long tube is uniformly magnetized along the tube axis, however there are curling states of various circular polarities near the tube ends. The characteristic length of ending curling states, as well as switching field Hs in the external magnetic field parallel to the tube axis, have been calculated as a function of outer tube radius and tube thickness.

Chen, A. P.; Usov, N. A.; Blanco, J. M.; Gonzalez, J.

2007-09-01

368

Equilibrium magnetization states in magnetic nanotubes and their evolution in external magnetic field  

Energy Technology Data Exchange (ETDEWEB)

The equilibrium magnetization states existing in soft magnetic nanotubes and their behavior in external magnetic field are investigated by means of micromagnetic simulation. In the ground state the middle part of a sufficiently long tube is uniformly magnetized along the tube axis, however there are curling states of various circular polarities near the tube ends. The characteristic length of ending curling states, as well as switching field H {sub s} in the external magnetic field parallel to the tube axis, have been calculated as a function of outer tube radius and tube thickness.

Chen, A.P. [Dpto. de Fisica de Materiales, Fac. Quimicas, Universidad del Pais Vasco, San Sebastian 20009 (Spain)]. E-mail: scpchxxa@ehu.es; Usov, N.A. [Dpto. de Fisica de Materiales, Fac. Quimicas, Universidad del Pais Vasco, San Sebastian 20009 (Spain); Troitsk Institute for Innovation and Fusion Research, Troitsk, Moscow Region 142190 (Russian Federation); Blanco, J.M. [Department of Applied Physics I, EUITI, POV/EHU, Plaza Europa, 1, San Sebastian 20080 (Spain); Gonzalez, J. [Dpto. de Fisica de Materiales, Fac. Quimicas, Universidad del Pais Vasco, San Sebastian 20009 (Spain)

2007-09-15

369

Equilibrium magnetization states in magnetic nanotubes and their evolution in external magnetic field  

International Nuclear Information System (INIS)

The equilibrium magnetization states existing in soft magnetic nanotubes and their behavior in external magnetic field are investigated by means of micromagnetic simulation. In the ground state the middle part of a sufficiently long tube is uniformly magnetized along the tube axis, however there are curling states of various circular polarities near the tube ends. The characteristic length of ending curling states, as well as switching field H s in the external magnetic field parallel to the tube axis, have been calculated as a function of outer tube radius and tube thickness.

2007-01-01

370

A Field Cancellation Algorithm for Constructing Economical Planar Permanent Magnet (PM) Multipoles With Large High Quality Field Apertures  

International Nuclear Information System (INIS)

In recent years studies have been initiated on a new class of multipole field generators consisting of cuboid planar permanent magnet (PM) pieces arranged in biplanar arrays of 2-fold rotational symmetry. These structures, first introduced for Free Electron Laser (FEL) applications, are based on reducing the rotational symmetry of conventional N-pole field generators from N-fold to 2-fold. One consequence of this reduction is a large higher-multipole content in a planar PM multipole's field at distances relatively close to the structure's axis, making it generally unsuitable for applications requiring a large high-quality field aperture. In this paper we outline an economical field-cancellation algorithm that can substantially decrease the harmonic content of a planar PM's field without breaking its biplanar geometry or 2-fold rotational symmetry. An economical field-cancellation algorithm has been described which will allow the fabrication of bi-planar quadrupoles and sextupoles with high-quality fields using a manageably small number of PM pieces. For higher order N-poles the number of pieces required to cancel a given number of successively-higher multipole components will also increase linearly; nevertheless, the practicability of fabricating octupoles and higher N-poles of this type should be considered a subject of continuing r and d. Since the removal of a large number of successive multipole components essentially increases the transverse region over which the N-pole's field is dominated by its leading N-pole field component, the fabrication of quadrupoles and sextupoles of the type described in this paper should lead to their introduction in storage ring applications. One potentially important application in this area is as distributed focusing elements installed into very-short-period, small-gap undulators (e.g., as a FODO lattice). The installation is rendered feasible by the very small vertical height of the biplanar N-poles (on the order of a millimeter), which, notwithstanding, doesn't prevent them from attaining focusing gradients on the order of several hundred T/m. If proven, this would allow short-period undulators of substantial length (viz., >>b) to be operated on storage rings, potentially transforming the optimality and economy of synchrotron radiation sources toward more favorable regimes.

2011-01-01

371

The magnetic fields of hot subdwarf stars  

CERN Multimedia

Detection of magnetic fields has been reported in several sdO and sdB stars. Recent literature has cast doubts on the reliability of most of these detections. We revisit data previously published in the literature, and we present new observations to clarify the question of how common magnetic fields are in subdwarf stars. We consider a sample of about 40 hot subdwarf stars. About 30 of them have been observed with the FORS1 and FORS2 instruments of the ESO VLT. Here we present new FORS1 field measurements for 17 stars, 14 of which have never been observed for magnetic fields before. We also critically review the measurements already published in the literature, and in particular we try to explain why previous papers based on the same FORS1 data have reported contradictory results. All new and re-reduced measurements obtained with FORS1 are shown to be consistent with non-detection of magnetic fields. We explain previous spurious field detections from data obtained with FORS1 as due to a non-optimal method of ...

Landstreet, John D; Fossati, Luca; Jordan, Stefan; O'Toole, Simon J

2012-01-01

372

Measuring the absolute magnetic field using high-Tc SQUID  

International Nuclear Information System (INIS)

SQUID normally can only measure the change of magnetic field instead of the absolute value of magnetic field. Using a compensation method, a mobile SQUID, which could keep locked when moving in the earth's magnetic field, was developed. Using the mobile SQUID, it was possible to measure the absolute magnetic field. The absolute value of magnetic field could be calculated from the change of the compensation output when changing the direction of the SQUID in a magnetic field. Using this method and the mobile SQUID, we successfully measured the earth's magnetic field in our laboratory.

2006-06-01

373

Solar Magnetic Fields and Geomagnetic Events.  

UK PubMed Central (United Kingdom)

Recent interplanetary studies conclude that the large-scale solar dipolar field dominates the solarcycle modulation of the magnetic structure of interplanetary clouds. Other studies lead one toexpect that the toroidal fields of active regions, described by the Hale-Nicholson polarity law,play an important role. We have studied the ratio of the geomagnetic A p index to the sunspotnumber for solar cycles 17-22. We find no compelling evidence that either the large-scale dipolarfield or active regions uniquely modulate this quantity on solar-cycle time scales.In the period 1991 -- 1998 the large-scale solar dipolar magnetic field pointed southward. Duringthis period we studied geomagnetic storms temporally associated with the eruption of 18individual coronal X-ray sigmoids observed with the Yohkoh Soft X-Ray Telescope (SXT). Weapply two different models -- force-free field (FFF) and coronal flux-rope (CFR) -- to infer themagnetic fields in these sigmoids and the geomagne...

Alexei A. Pevtsov; Richard C. Canfield

374

Field flattening in superconducting beam transport magnets  

International Nuclear Information System (INIS)

Dipoles in which the beam traverses the midplane well away from tie magnet axis may benefit from flattening of the vertical field on the midplane. A procedure is described for doing so, making use of Chebyshev polynomials. In the case of the large aperture ''DX'' magnets located immediately on each side of the six intersection regions of the Relativistic Heavy Ion Powder (RHIC), a comparison is made of the field of coils optimized in this way and of coils optimized in the more common way by minimizing the leading coefficients of the Fourier expansion about the magnet axis. The comparison is of the integrated Fourier coefficients of the field expanded locally along the beam trajectory

1994-01-01

375

Tracing Magnetic Fields with Aligned Grains  

CERN Document Server

Magnetic fields play a crucial role in various astrophysical processes, including star formation, accretion of matter, transport processes (e.g., transport of heat), and cosmic rays. One of the easiest ways to determine the magnetic field direction is via polarization of radiation resulting from extinction on or/and emission by aligned dust grains. Reliability of interpretation of the polarization maps in terms of magnetic fields depends on how well we understand the grain-alignment theory. Currently the grain-alignment theory is a predictive one, and its results nicely match observations. Among its predictions is a subtle phenomenon of radiative torques. after having stayed in oblivion for many years after its discovery, is currently viewed as the most powerful means of alignment. In this article, I shall review the basic physical processes involved in grain alignment, and the currently known mechanisms of alignment. I shall also discuss possible niches for different alignment mechanisms. I shall dwell on th...

Lazarian, A

2007-01-01

376

Consistency relation for cosmic magnetic fields  

DEFF Research Database (Denmark)

If cosmic magnetic fields are indeed produced during inflation, they are likely to be correlated with the scalar metric perturbations that are responsible for the cosmic microwave background anisotropies and large scale structure. Within an archetypical model of inflationary magnetogenesis, we show that there exists a new simple consistency relation for the non-Gaussian cross correlation function of the scalar metric perturbation with two powers of the magnetic field in the squeezed limit where the momentum of the metric perturbation vanishes. We emphasize that such a consistency relation turns out to be extremely useful to test some recent calculations in the literature. Apart from primordial non-Gaussianity induced by the curvature perturbations, such a cross correlation might provide a new observational probe of inflation and can in principle reveal the primordial nature of cosmic magnetic fields. DOI: 10.1103/PhysRevD.86.123528

Jain, R. K.; Sloth, M. S.

2012-01-01

377

Human melatonin during continuous magnetic field exposure  

Energy Technology Data Exchange (ETDEWEB)

This report describes the third in a series of double-blind, laboratory-based studies that were aimed at determining the effects of nocturnal exposure to power frequency magnetic fields on blood levels of melatonin in human volunteers. The two earlier studies evaluated effects on melatonin of intermittent exposure to 60 Hz circularly polarized magnetic fields at 10 and 200 mG. No overall effects on melatonin levels were found. In the present study, men were exposed continuously rather than intermittently through the night to the same 200 mG magnetic field condition that was used previously; again, no overall effects on melatonin levels were found. The authors conclude that the intermittent and continuous exposure conditions used in the laboratory to date are not effective in altering nocturnal blood levels of melatonin in human volunteers.

Graham, C.; Cook, M.R.; Riffle, D.W. [Midwest Research Inst., Kansas City, MO (United States)

1997-05-01

378

Diffusive shock acceleration and magnetic field amplification  

CERN Document Server

Diffusive shock acceleration is the theory of particle acceleration through multiple shock crossings. In order for this process to proceed at a rate that can be reconciled with observations of high-energy electrons in the vicinity of the shock, and for cosmic rays protons to be accelerated to energies up to observed galactic values, significant magnetic field amplification is required. In this review we will discuss various theories on how magnetic field amplification can proceed in the presence of a cosmic ray population. On both short and long scales, cosmic ray streaming can induce instabilities that act to amplify the magnetic field. Developments in this area that have occurred over the past decade are the main focus of this paper.

Schure, K M; Drury, L O'C; Bykov, A M

2012-01-01

379

Diffusive Shock Acceleration and Magnetic Field Amplification  

Science.gov (United States)

Diffusive shock acceleration is the theory of particle acceleration through multiple shock crossings. In order for this process to proceed at a rate that can be reconciled with observations of high-energy electrons in the vicinity of the shock, and for cosmic rays protons to be accelerated to energies up to observed galactic values, significant magnetic field amplification is required. In this review we will discuss various theories on how magnetic field amplification can proceed in the presence of a cosmic ray population. On both short and long length scales, cosmic ray streaming can induce instabilities that act to amplify the magnetic field. Developments in this area that have occurred over the past decade are the main focus of this paper.

Schure, K. M.; Bell, A. R.; O'C Drury, L.; Bykov, A. M.

2012-11-01

380

Collective excitations in graphene in magnetic field  

CERN Document Server

Monolayer graphene collective excitations are studied. The equations describing collective properties of electrons in graphene were obtained. For the derivation the basic ideas of the method of many-particle quantum hydrodynamics were used. As starting point of derivation we used the Dirac's like equation for massless electrons which usually using for description of electrons in graphene [D. E. Sheehy and J. Schmalian, Phys. Rev. Lett. 99, 226803 (2007)], where the Coulomb interaction taken into account. We studied the dispersion properties of collective excitations by means derived here quantum hydrodynamics equations for graphene (GQHD). We considered graphene in the external magnetic field which directed at an angle to the graphene sample in linear approximation for GQHD equations. We observe that the magnetic field directed perpendicular to the graphene plane had no influence on collective excitation dispersion. For the magnetic field directed at an angle to the graphene we receive dependence of wave disp...

Andreev, Pavel A

2012-01-01

 
 
 
 
381

Magnetic field draping about coronal mass ejecta  

Energy Technology Data Exchange (ETDEWEB)

Fast coronal mass ejecta (CMEs) accelerate and deflect the slower moving solar wind plasma which piles up ahead of them as they propagate out through the heliosphere. This acceleration and deflection, in turn, causes the interplanetary magnetic field (IMF) imbedded in the upstream solar wind to drape about the ejecta. Draping should cause substantial out-of-the-ecliptic magnetic fields at some locations ahead of CMEs, and radial fields behind and along the flanks. At the Earth, draping can be an important factor in the generation of some magnetic storms and substorms, while in the outer heliosphere draping may produce very large magnetotail-like configurations, somewhat analogous to those observed behind Venus and comets. 17 refs.

McComas, D.J.; Gosling, J.T.

1987-01-01

382

Magnetic field effects on electrochemical metal depositions  

Directory of Open Access Journals (Sweden)

Full Text Available This paper discusses recent experimental and numerical results from the authors' labs on the effects of moderate magnetic (B) fields in electrochemical reactions. The probably best understood effect of B fields during electrochemical reactions is the magnetohydrodynamic (MHD) effect. In the majority of cases it manifests itself in increased mass transport rates which are a direct consequence of Lorentz forces in the bulk of the electrolyte. This enhanced mass transport can directly affect the electrocrystallization. The partial currents for the nucleation of nickel in magnetic fields were determined using an in situ micro-gravimetric technique and are discussed on the basis of the nucleation model of Heerman and Tarallo. Another focus of the paper is the numerical simulation of MHD effects on electrochemical metal depositions. A careful analysis of the governing equations shows that many MHD problems must be treated in a 3D geometry. In most cases there is a complex interplay of natural and magnetically driven convection.

Andreas Bund, Adriana Ispas and Gerd Mutschke

2008-01-01

383

Microwave Background Signals from Tangled Magnetic Fields  

CERN Multimedia

An inhomogeneous cosmological magnetic field will create Alfven-wave modes that induce a small rotational velocity perturbation on the last scattering surface of the microwave background radiation. The Alfven-wave mode survives Silk damping on much smaller scales than the compressional modes. This, in combination with its rotational nature, ensures that there will be no sharp cut-off in anisotropy on arc-minute scales. We estimate that a magnetic field which redshifts to a present value of $3\\times 10^{-9}$ Gauss produces temperature anisotropies at the 10 micro Kelvin level at and below 10 arc-min scales. A tangled magnetic field, which is large enough to influence the formation of large scale structure is therefore potentially detectable by future observations.

Subramanian, K; Subramanian, Kandaswamy; Barrow, John D.

1998-01-01

384

Temporally incoherent magnetic fields mitigate the response of biological systems to temporally coherent magnetic fields.  

UK PubMed Central (United Kingdom)

We have previously demonstrated that a weak, extremely-low-frequency magnetic field must be coherent for some minimum length of time (approximately 10 s) in order to affect the specific activity of ornithine decarboxylase (ODC) in L929 mouse cells. In this study we explore whether or not the superposition of an incoherent (noise) magnetic field can block the bioeffect of a coherent 60 Hz magnetic field, since the sum of the two fields is incoherent. An experimental test of this idea was conducted using as a biological marker the twofold enhancement of ODC activity found in L929 murine cells after exposure to a 60 Hz, 10 microT rms magnetic field. We superimposed an incoherent magnetic noise field, containing frequencies from 30 to 90 Hz, whose rms amplitude was comparable to that of the 60 Hz field. Under these conditions the ODC activity observed after exposure was equal to control levels. It is concluded that the superposition of incoherent magnetic fields can block the enhancement of ODC activity by a coherent magnetic field if the strength of the incoherent field is equal to or greater than that of the coherent field. When the superimposed, incoherent noise field was reduced in strength, the enhancement of ODC activity by the coherent field increased. Full ODC enhancement was obtained when the rms value of the applied EM noise was less than one-tenth that of the coherent field. These results are discussed in relation to the question of cellular detection of weak EM fields in the presence of endogenous thermal noise fields.

Litovitz TA; Krause D; Montrose CJ; Mullins JM

1994-01-01

385

Structure of the magnetospheric magnetic field during magnetic storms  

Science.gov (United States)

We report the results of a study of the contributions of the large-scale magnetospheric currents to the observed Dst variation. Ground-based magnetometer data during four magnetic storms (January 27-30, 1985; November 23-27, 1986; January 14-16, 1988; and May 6-8, 1988) were used to calculate Dst, and the paraboloid model of the magnetospheric magnetic field [Alexeev et al., 1996] was used to determine the contribution of each magnetospheric current system. Input data for our model were the solar wind plasma parameters, the interplanetary magnetic field (IMF) BZ, DMSP F6, F7, F8, and F9 satellite observations of precipitating auroral particles, and Active Magnetospheric Particle Tracer Explorers (AMPTE)/CCE satellite measurements of the total energy of the ring current ions with energy per charge between 1.5 and 300 keVq-1. We found good agreement between observed and modeled magnetic fields during the main phase of the magnetic storms. Using the paraboloid model, we have determined the contributions to Dst of different magnetospheric current systems including the magnetopause current BCF, the symmetric ring current BR, and the geotail current BT. Such separation shows that values of BT and BCF are comparable with the value of BR during the main phase of the storms. During the recovery phase the effect of BR predominates.

Dremukhina, L. A.; Feldstein, Y. I.; Alexeev, I. I.; Kalegaev, V. V.; Greenspan, M. E.

386

Doped spin ladders under magnetic field  

International Nuclear Information System (INIS)

This thesis deals with the physics of doped two-leg ladders which are a quasi one-dimensional and unconventional superconductor. We particularly focus on the properties under magnetic field. Models for strongly correlated electrons on ladders are studied using exact diagonalization and density-matrix renormalization group (DMRG). Results are also enlightened by using the bosonization technique. Taking into account a ring exchange it highlights the relation between the pairing of holes and the spin gap. Its influence on the dynamics of the magnetic fluctuations is also tackled. Afterwards, these excitations are probed by the magnetic field by coupling it to the spin degree of freedom of the electrons through Zeeman effect. We show the existence of doping-dependent magnetization plateaus and also the presence of an inhomogeneous superconducting phase (FFLO phase) associated with an exceeding of the Pauli limit. When a flux passes through the ladder, the magnetic field couples to the charge degree of freedom of the electrons via orbital effect. The diamagnetic response of the doped ladder probes the commensurate phases of the t-J model at low J/t. Algebraic transverse current fluctuations are also found once the field is turned on. Lastly, we report numerical evidences of a molecular superfluid phase in the 3/2-spin attractive Hubbard model: at a density low enough, bound states of four fermions, called quartets, acquire dominant superfluid fluctuations. The observed competition between the superfluid and density fluctuations is connected to the physics of doped ladders. (author)

2007-01-01

387

Plasma diagnostic in magnetic field. Plane probe  

Energy Technology Data Exchange (ETDEWEB)

Theoretical investigation of plasma parameters has been performed in the magnetic field by the probe method. A dependence of electron current on cut-off potential at arbitrary relations between the probe radius and Langmuir radius of electrons has been discovered. Electron energy distribution function has been obtained as a result of the processing of current-voltage characteristics (CVC) of a plane probe oriented perpendicularly to a magnetic field. A comparison of experimental electron concentrations with the data obtained by means of the probe CVC processing reveals their satisfactory agreement.

Devyatov, A.M.; Mal' kov, M.A. (Moskovskij Gosudarstvennyj Univ. (USSR))

1984-03-01

388

In situ characterization of undulator magnetic fields.  

UK PubMed Central (United Kingdom)

A new in situ method is proposed to characterize the peak magnetic fields of undulator sources. The X-ray beam emitted by the HU52 Apple-2 undulator of the DEIMOS beamline of the SOLEIL synchrotron is analyzed using the Bragg diffraction of a Si(111) crystal. Measurements over the undulator gap range in linear horizontal polarization are compared with simulations in order to rebuild the Halbach function linking the undulator gaps to their peak magnetic fields. The method presented also allows information about the electron beam to be obtained.

Moreno T; Otero E; Ohresser P

2012-03-01

389

Collider dipole magnet field angle measurement  

International Nuclear Information System (INIS)

This paper discusses methods and devices for measuring the prototype Superconducting Super Collider (SSC) dipole magnetic field angle with respect to a vertical reference. An internal research and development project was conducted at General Dynamics to develop a low cost device for production measurement of the SSC dipole field verticality. The system employs Hall probes, a level sensor and precision electronics interfaced to a personal computer to perform this critical measurement at discrete points along the magnet beam axis. Specifications, component selection, mechanical and electrical design, calibration and test results are presented

1991-01-01

390

Reduction of a Ship's Magnetic Field Signatures  

CERN Multimedia

Decreasing the magnetic field signature of a naval vessel will reduce its susceptibility to detonating naval influence mines and the probability of a submarine being detected by underwater barriers and maritime patrol aircraft. Both passive and active techniques for reducing the magnetic signatures produced by a vessel's ferromagnetism, roll-induced eddy currents, corrosion-related sources, and stray fields are presented. Mathematical models of simple hull shapes are used to predict the levels of signature reduction that might be achieved through the use of alternate construction materials. Al

Holmes, John

2008-01-01

391

Germination of wheat grain in an alternating magnetic field  

Directory of Open Access Journals (Sweden)

Full Text Available The paper presents the germination of wheat grains of the variety Henika, in an alternating magnetic field. The research conducted showed that the influence of an alternating magnetic field on germination depends on the value of the magnetic induction. A magnetic field affects germination mainly during the initial 50 h of the process. The highest positive influence of the field was observed in the field with magnetic inductions of 50 and 80 mT.

Pietruszewski S.; Kornarzyński K.; Łacek R.

2001-01-01

392

Magnetic clouds and force-free fields with constant alpha  

Energy Technology Data Exchange (ETDEWEB)

Magnetic clouds observed at 1 AU are modeled as cylindrically symmetric, constant alpha force-free magnetic fields. The model satisfactorily explains the types of variations of the magnetic field direction that are observed as a magnetic cloud moves past a spacecraft in terms of the possible orientations of the axis of a magnetic cloud. The model also explains why the magnetic field strength is observed to be higher inside a magnetic cloud than near its boundaries. However, the model predicts that the magnetic field strength profile should be symmetric with respect to the axis of the magnetic cloud, whereas observations show that this is not generally the case.

Burlaga, L.F. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

1988-07-01

393

Magnetic fields of HgMn stars?  

Science.gov (United States)

Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have failed to detect magnetic fields, indicating an upper limit on the longitudinal field between 8 and 15 G. In these LSD studies, assumptions were made that all spectral lines are identical in shape and can be described by a scaled mean profile. Aims: We re-analyse the available spectropolarimetric material by applying the moment technique on spectral lines of inhomogeneously distributed elements separately. Furthermore, we present new determinations of the mean longitudinal magnetic field for the HgMn star HD 65949 and the hotter analog of HgMn stars, the PGa star HD 19400, using FORS 2 installed at the VLT. We also give new measurements of the eclipsing system AR Aur with a primary star of HgMn peculiarity, which were obtained with the SOFIN spectropolarimeter installed at the Nordic Optical Telescope. Methods: We downloaded from the European Southern Observatory (ESO) archive the publically available HARPS spectra for eight HgMn stars and one normal and one superficially normal B-type star obtained in 2010. Out of this sample, three HgMn stars belong to spectroscopic double-lined systems. The application of the moment technique to the HARPS and SOFIN spectra allowed us to study the presence of the longitudinal magnetic field, the crossover effect, and quadratic magnetic fields. Results for the HgMn star HD 65949 and the PGa star HD 19400 are based on a linear regression analysis of low-resolution spectra obtained with FORS 2 in spectropolarimetric mode. Results: Our measurements of the magnetic field with the moment technique using spectral lines of several elements separately reveal the presence of a weak longitudinal magnetic field, a quadratic magnetic field, and the crossover effect on the surface of several HgMn stars as well as normal and superficially normal B-type stars. Furthermore, our analysis suggests the existence of intriguing correlations between the strength of the magnetic field, abundance anomalies, and binary properties. The results are discussed in the context of possible mechanisms responsible for the development of the element patches and complex magnetic fields on the surface of late B-type stars. Based on observations obtained at the European Southern Observatory (ESO programmes 076.D-0169(A), 076.D-0172(A), 084.D-0338(A), 085.D-0296(A), 085.D-0296(B), 087.D-0049(A), 088.D-0284(A)), SOFIN observations at the 2.56 m Nordic Optical Telescope on La Palma, and observations obtained with the CORALIE Echelle Spectrograph on the 1.2 m Euler Swiss telescope on La Silla, Chile.Tables 2-7, 9, 10 are only available in electronic form at http://www.aanda.org

Hubrig, S.; González, J. F.; Ilyin, I.; Korhonen, H.; Schöller, M.; Savanov, I.; Arlt, R.; Castelli, F.; Lo Curto, G.; Briquet, M.; Dall, T. H.

2012-11-01

394

Magnetic field exposure of commercial airline pilots.  

UK PubMed Central (United Kingdom)

PURPOSE: Airline pilots are exposed to magnetic fields generated by the aircraft's electrical and electronic systems. The purpose of this study was to directly measure the flight deck magnetic fields to which commercial airline pilots are exposed when flying on different aircraft types over a 75-hour flight-duty month.METHODS: Magentic field measurements were taken using personal dosimeters capable of measuring magnetic fields in the 40-800 Hz frequency range. Dosimeters were carried by either the Captain or the First Officer on Boeing 737/200, Boeing 747/400, Boeing 767/300ER, and Airbus 320 aircraft. The data were analyzed by aircraft type, with statistics based on block hours. Block hours begin when the aircraft departs the gate prior to take off and end when the aircraft returns to the gate after landing.RESULTS: Approximately 1008 block hours were recorded at a sampling rate of 3 seconds. Total block time exposure to the pilots ranged from a harmonic geometric mean of 6.7 milliGauss (mG) for the Boeing 767/300ER to 12.7 mG for the Boeing 737/200.CONCLUSIONS: Measured flight deck magnetic field levels were substantially above the 0.8 to 1 mG level typically found in the home or office and suggest the need for further study to evaluate potential health effects of long-term exposure.

Hood W; Nicholas J; Butler G; Lackland D; Hoel D; Mohr L

2000-10-01

395

Multi-coil magnetic field modeling.  

UK PubMed Central (United Kingdom)

The performance of multi-coil (MC) magnetic field modeling is compared to dedicated wire patterns for the generation of spherical harmonic (SH) shapes as these are the workhorse for spatial encoding and magnetic field homogenization in MR imaging and spectroscopy. To this end, an example 48 channel MC setup is analyzed and shown to be capable of generating all first through fourth order SH shapes over small and large regions-of-interest relevant for MR investigations. The MC efficiency for the generation of linear gradient fields shares the same order of magnitude with classic and state-of-the-art SH gradient coils. MC field modeling becomes progressively more efficient with the synthesis of more complex field shapes that require the combination of multiple SH terms. The possibility of a region-specific optimization of both magnetic field shapes and generation performance with the MC approach are discussed with emphasis on the possible trade-off between the field accuracy and generation efficiency. MC shimming has been shown previously to outperform current SH shimming. Along with the efficiency gains of MC shimming shown here, the MC concept has the potential to (1) replace conventional shim systems that are based on sets of dedicated SH coils and (2) allow optimal object-specific shim solutions similar to object-specific RF coils.

Juchem C; Green D; de Graaf RA

2013-09-01

396

Sensor for detecting changes in magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

A sensor for detecting changes in the magnetic field of the equilibrium-field coil of a Tokamak plasma device comprises a pair of bifilar wires disposed circumferentially, one inside and one outside the equilibrium-field coil. Each is shorted at one end. The difference between the voltages detected at the other ends of the bifilar wires provides a measure of changing flux in the equilibrium-field coil. This difference can be used to detect faults in the coil in time to take action to protect the coil.

Praeg, Walter F. (Palos Park, IL)

1981-01-01

397

Magnetic fields in the interplanetary space  

Energy Technology Data Exchange (ETDEWEB)

This summary comprises two parts. In the first, attention is given to the overall structure of the interplanetary field of essentially solar origin convected by the solar wind. In the second part, the in situ observations of planetary magnetic fields of either internal and/or external origin are reviewed. With regard to the overall structure, problems remain concerning in particular the source region close to the sun and the propagation and evolution of the perturbations associated with solar activity. With regard to the planetary fields, the problems have to do with the source of the internal fields and the implications of the internal planetary structures.

Mariani, F.

1982-01-01

398

Sensor for detecting changes in magnetic fields  

Science.gov (United States)

A sensor is described for detecting changes in the magnetic field of the equilibrium-field coil of a Tokamak plasma device that comprises a pair of bifilar wires disposed circumferentially, one inside and one outside the equilibrium-field coil. Each is shorted at one end. The difference between the voltages detected at the other ends of the bifilar wires provides a measure of changing flux in the equilibrium-field coil. This difference can be used to detect faults in the coil in time to take action to protect the coil.

Praeg, W.F.

1980-02-26

399

Two-octupole-phonon states in 146,148Gd  

International Nuclear Information System (INIS)

The so-called 'two-octupole-phonon states' in 146,148Gd are theoretically analyzed by using the Dyson boson mapping method. In our analyses, the free ground state of 146Gd is treated as doubly closed shell since Z=64 is rather good subshell closure. The starting collective multi-phonon space that we take consists of collective octupole phonons and collective monopole pairing phonons for 146Gd. Additionally correlated particle-pair modes with J?0 are included in the multi-phonon space for 148Gd. The effective Hamiltonian used is constituted by a Woods-Saxon-type single-particle potential, an octupole-octupole force for particle-hole modes and a surface-delta interaction for particle-pair and hole-pair modes. The numerical calculation can considerably well reproduce the octupole collectivity shown by experiments for 146,148Gd. It is shown that the Dyson boson mapping method is useful for such a complicated system as 148Gd. (author).

1996-01-01

400

Octupole response and stability of spherical shape in heavy nuclei  

CERN Document Server

The isoscalar octupole response of a heavy spherical nucleus is analyzed in a semiclassical model based on the linearized Vlasov equation. The octupole strength function is evaluated with different degrees of approximation. The zero-order fixed-surface response displays a remarkable concentration of strength in the $1\\hbar\\omega$ and $3\\hbar\\omega$ regions, in excellent agreement with the quantum single-particle response. The collective fixed-surface response reproduces both the high- and low-energy octupole rsonances, but not the low-lying $3^{-}$ collective states, while the moving-surface response function gives a good qualitative description of all the main features of the octupole response in heavy nuclei. The role of triangular nucleon orbits, that have been related to a possible instability of the spherical shape with respect to octupole-type deformations, is discussed within this model. It is found that, rather than creating instability, the triangular trajectories are the only classical orbits contri...

Abrosimov, V I; Dellafiore, A; Matera, F

2003-01-01

 
 
 
 
401

SQUID-detected magnetic resonance imaging in microtesla magnetic fields  

International Nuclear Information System (INIS)

[en] We describe studies of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) of liquid samples at room temperature in microtesla magnetic fields. The nuclear spins are prepolarized in a strong transient field. The magnetic signals generated by the precessing spins, which range in frequency from tens of Hz to several kHz, are detected by a low-transition temperature dc SQUID (Superconducting QUantum Interference Device) coupled to an untuned, superconducting flux transformer configured as an axial gradiometer. The combination of prepolarization and frequency-independent detector sensitivity results in a high signal-to-noise ratio and high spectral resolution (?1 Hz) even in grossly inhomogeneous magnetic fields. In the NMR experiments, the high spectral resolution enables us to detect the 10-Hz splitting of the spectrum of protons due to their scalar coupling to a 31P nucleus. Furthermore, the broadband detection scheme combined with a non-resonant field-reversal spin echo allows the simultaneous observation of signals from protons and 31P nuclei, even though their NMR resonance frequencies differ by a factor of 2.5. We extend our methodology to MRI in microtesla fields, where the high spectral resolution translates into high spatial resolution. We demonstrate two-dimensional images of a mineral oil phantom and slices of peppers, with a spatial resolution of about 1 mm. We also image an intact pepper using slice selection, again with 1-mm resolution. In further experiments we demonstrate T1-contrast imaging of a water phantom, some parts of which were doped with a paramagnetic salt to reduce the longitudinal relaxation time T1. Possible applications of this MRI technique include screening for tumors and integration with existing multichannel SQUID systems for brain imaging

2003-11-26

402

Magnetic field in the SSC arc quad  

International Nuclear Information System (INIS)

In part one we report on field calculations along the conductor in the end region of the SSC arc-quad. We have determined that the maximum field in the 2D section is 5.04 tesla located at the pole turn of the inner layer somewhere in the middle of the cable (strand 9)(fields are at 6500 A). At the ''end'' the maximum field is slightly higher 5.09 tesla located at the overpass (strand 11). The iron contribution was included assuming infinite permeability. In part two we include results of a 3D representation of the magnetic field inside the bore. The complete analysis, for which a brief description has been included here, is described elsewhere. This form for presenting the field is suitable for interfacing with other codes that make use of the 3D field components (particle tracking and stability). 69 figs

1991-01-01

403

MR safety at high magnetic fields.  

UK PubMed Central (United Kingdom)

MR imaging requires the exposure of human patients to magnetic fields that are much more intense than ever occur naturally. Under most circumstances, however, these fields do not appear to pose a health or safety risk even at levels well above those currently in clinical use. This margin of safety results from the extreme weakness of the diamagnetic interaction between human tissues and magnetic fields. Ferromagnetic materials, however, present either as implants within the patient or inadvertently introduced into the scanner environment, pose significant risks and must be scrupulously avoided. At very high field strengths, there is evidence for mild sensory effects, such as vertigo and metallic tastes, which do not appear to be harmful.

Schenck JF

1998-11-01

404

MR safety at high magnetic fields.  

Science.gov (United States)

MR imaging requires the exposure of human patients to magnetic fields that are much more intense than ever occur naturally. Under most circumstances, however, these fields do not appear to pose a health or safety risk even at levels well above those currently in clinical use. This margin of safety results from the extreme weakness of the diamagnetic interaction between human tissues and magnetic fields. Ferromagnetic materials, however, present either as implants within the patient or inadvertently introduced into the scanner environment, pose significant risks and must be scrupulously avoided. At very high field strengths, there is evidence for mild sensory effects, such as vertigo and metallic tastes, which do not appear to be harmful. PMID:9799852

Schenck, J F

1998-11-01

405

Rayleigh-Bénard convection with magnetic field  

Directory of Open Access Journals (Sweden)

Full Text Available We discuss the solution of the small perturbation equations for a horizontal fluid layer heated from below with an applied magnetic field either in vertical or in horizontal direction. The magnetic field stabilizes, due to the Lorentz force, more or less Rayleigh-Bénard convective cellular motion. The solution of the eigenvalue problem shows that the critical Rayleigh number increases with increasing Hartmann number while the corresponding wave length decreases. Interesting analogies to solar granulation and black spots phenomena are obvious. The influence of a horizontal field is stronger than that of a vertical field. It is easy to understand this by discussing the influence of the Lorentz force on the Rayleigh-Bénard convection. This result corrects earlier calculations in the literature.

Zierep Jürgen

2003-01-01

406

Evolution of primordial magnetic fields in mean-field approximation  

CERN Multimedia

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

Campanelli, Leonardo

2013-01-01

407

Magnetic field configuration of the theta aurora  

International Nuclear Information System (INIS)

[en] The theta aurora is an approximately Sun-aligned transpolar arc that often extends the entire length of the polar cap, linking the dayside and nightside auroral zones. It is a remarkable manifestation of polar cap auroral activity that appears during periods of northward interplanetary magnetic field (IMF). In this paper the authors describe a magnetic configuration of the open magnetosphere that is conducive to the formation of the theta aurora when the IMF has a significant northward component. They present a magnetic field topology and polar cap configuration that is derived from a quantitative model of the open magnetosphere that incorporates Crooker's antiparallel merging hypothesis. Under this hypothesis, when the IMF has a northward component, the dayside merging line bifurcates, leaving a large fraction of the subsolar magnetopause untouched by the merging process. The polar cap, defined by tracing magnetic field lines that connect from the solar wind to the Earth, is similarly bifurcated, leaving a sun-aligned stagnation region that is not magnetically connected to the solar wind and may plausibly be associated with the sun-aligned bar of the theta aurora. The model provides testable predictions with regard to the position of this convection gap in both northern and southern hemispheres as functions of IMF direction

1990-01-01

408

High magnetic field facilities in Latin America  

International Nuclear Information System (INIS)

[en] The EC supported a network (under the Framework 5 ALFA Programme) designated HIFIELD (Project number II0147FI) and entitled: Measurement methods involving high magnetic fields for advanced and novel materials. As a result, high field facilities were initiated, constructed or extended at the following laboratories in Latin America: University Cordoba (Argentina), CES, Merida (Venezuela), CIMAV, Chihuahua (Mexico), University Federal de Rio de Janeiro (Brazil)

2006-01-01

409

High magnetic field facilities in Latin America  

Energy Technology Data Exchange (ETDEWEB)

The EC supported a network (under the Framework 5 ALFA Programme) designated HIFIELD (Project number II0147FI) and entitled: {sup M}easurement methods involving high magnetic fields for advanced and novel materials{sup .} As a result, high field facilities were initiated, constructed or extended at the following laboratories in Latin America: University Cordoba (Argentina), CES, Merida (Venezuela), CIMAV, Chihuahua (Mexico), University Federal de Rio de Janeiro (Brazil)

Sato, R [Inst. f. Festkoerperphysik, T.U.Vienna (Austria); Groessinger, R [Inst. f. Festkoerperphysik, T.U.Vienna (Austria); Bertorello, H [University Cordoba (Argentina); Broto, J M [LNCMP, Toulouse (France); Davies, H A [University Sheffield (United Kingdom); Estevez-Rams, E [University Havana (Cuba); Gonzalez, J [CES, Univ de los Andes, Merida (Venezuela); Matutes, J [CIMAV (Mexico); Sinnecker, J P [Instituo de Fisica, UFRJ (Brazil); Sagredo, V [Univ de los Andes (Venezuela)

2006-11-15

410

Phase diagrams for the precession states of the nanoparticle magnetization in a rotating magnetic field  

International Nuclear Information System (INIS)

Using the analytical and numerical solutions of the Landau-Lifshitz equation, we calculate the phase diagrams for the precession states of the nanoparticle magnetization in a rotating magnetic field. We show that there are three different scenarios for the magnetization switching. The bias magnetic field applied antiparallel to the nanoparticle magnetization strongly decreases the switching amplitudes and frequencies of the rotating field.

2010-01-01

411

Mechanical response of elastomers to magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

Elastomeric materials represent an important class of engineering materials, which are widely used to make components of structures, machinery, and devices for vibration and noise control. Elastomeric materials possessing conductive or magnetic properties are used in applications such as conductive and magnetic tapes, sensors, flexible permanent magnets, etc. Our interest in these materials has focused on understanding and controlling the magnitude and directionality of their mechanical response to applied magnetic fields. This presentation will discuss the control of mechanical properties and mathematical modeling of the new materials prepared in our laboratories along with experiments to achieve adaptive vibration control using the new materials. Such controllable elastomers promise to have more functionality than conventional elastomers and therefore could be a link that brings the applications of modern control technologies, intelligent structures, and smart materials to a very broad industrial area.

Munoz, B.C.; Jolly, M.R. [Lord Corporation, Cary, NC (United States)

1995-12-31

412

Magnetic field effects on twin dislocations  

Energy Technology Data Exchange (ETDEWEB)

This paper attempts to determine the influence of a magnetic field on the motion of twin dislocations in order to understand the mechanism involved in magnetically driven shape memory alloys. In this paper, the nucleation of dislocations was not considered and thus the pre-existence of dislocations prior to the application of a magnetic field was assumed. The procedure used here is a general one, although for simplicity, the authors will apply the concepts to the (3 10 15)F transformation in ferrous alloys. The reason for this choice is the fact that twinning plays a crucial role in this phase transformation and the phenomenological crystallographic theory provides a reasonable description for this phase transition.

Ferreira, P.J.; Vander Sande, J.B. (Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Materials Science and Engineering)

1999-06-18

413

Magnetic Fields in the Solar Convection Zone  

Directory of Open Access Journals (Sweden)

Full Text Available 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 article reviews studies with regard to the formation and rise of active region scale magnetic flux tubes in the solar convection zone and their emergence into the solar atmosphere as active regions.

Yuhong Fan

2009-01-01

414

Structural alloys for high field superconducting magnets  

International Nuclear Information System (INIS)

Research toward structural alloys for use in high field superconducting magnets is international in scope, and has three principal objectives: the selection or development of suitable structural alloys for the magnet support structure, the identification of mechanical phenomena and failure modes that may influence service behavior, and the design of suitable testing procedures to provide engineering design data. This paper reviews recent progress toward the first two of these objectives. The structural alloy needs depend on the magnet design and superconductor type and differ between magnets that use monolithic and those that employ force-cooled or ICCS conductors. In the former case the central requirement is for high strength, high toughness, weldable alloys that are used in thick sections for the magnet case. In the latter case the need is for high strength, high toughness alloys that are used in thin welded sections for the conductor conduit. There is productive current research on both alloy types. The service behavior of these alloys is influenced by mechanical phenomena that are peculiar to the magnet environment, including cryogenic fatigue, magnetic effects, and cryogenic creep. The design of appropriate mechanical tests is complicated by the need for testing at 40K and by rate effects associated with adiabatic heating during the tests. 46 refs

1985-01-01

415

Structural alloys for high field superconducting magnets  

Energy Technology Data Exchange (ETDEWEB)

Research toward structural alloys for use in high field superconducting magnets is international in scope, and has three principal objectives: the selection or development of suitable structural alloys for the magnet support structure, the identification of mechanical phenomena and failure modes that may influence service behavior, and the design of suitable testing procedures to provide engineering design data. This paper reviews recent progress toward the first two of these objectives. The structural alloy needs depend on the magnet design and superconductor type and differ between magnets that use monolithic and those that employ force-cooled or ICCS conductors. In the former case the central requirement is for high strength, high toughness, weldable alloys that are used in thick sections for the magnet case. In the latter case the need is for high strength, high toughness alloys that are used in thin welded sections for the conductor conduit. There is productive current research on both alloy types. The service behavior of these alloys is influenced by mechanical phenomena that are peculiar to the magnet environment, including cryogenic fatigue, magnetic effects, and cryogenic creep. The design of appropriate mechanical tests is complicated by the need for testing at 4/sup 0/K and by rate effects associated with adiabatic heating during the tests. 46 refs.

Morris, J.W. Jr.

1985-08-01

416

Passive levitation in alternating magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

Stable levitation of an object in an alternating magnetic field can be achieved by eliminating coupling between the rotational and translational forces acting on the object. Stable levitation can also be achieved by varying the coupling between the rotational and translational forces acting on the object, while maintaining one or more of the rotational and translational forces steady in time.

Romero, Louis (Albuquerque, NM); Christenson, Todd (Albuquerque, NM); Aronson, Eugene A. (Albuquerque, NM)

2009-06-16

417

Plasma flow in a curved magnetic field  

International Nuclear Information System (INIS)

A beam of collisionless plasma is injected along a longitudinal magnetic field into a region of curved magnetic field. Two unpredicted phenomena are observed: The beam becomes deflected in the direction opposite to that in which the field is curved, and it contracts to a flat slab in the plane of curvature of the magnetic field. The phenomenon is of a general character and can be expected to occur in a very wide range of densities. The lower density limit is set by the condition for self-polarization, nm sub(i)/epsilon0B2 >> 1 or, which is equivalent, c2/v2sub(A) >> 1, where c is the velocity of light, and v sup(A) the Alfven velocity. The upper limit is presumably set by the requirement ?sub(e)tau(e) >> 1. The phenomenon is likely to be of importance e.g. for injection of plasma into magnetic bottles and in space and solar physics. The paper illustrates the comlexity of plasma flow phenomena and the importance of close contact between experimental and theoretical work. (author)

1977-01-01

418

Lorentz forces caused by rotating magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Leading topic of this article is description of Lorentz forces in the container with cuboid shape. Inside of the container is an electrically conductive melt. Lorentz forces are caused by rotating magnetic field. Lorentz forces were calculated by analytic formula. This formula was derived for cylin...

Horáková K.; Fra?a K.

419

Magnetic field of Mars: Mars 5 evidence  

International Nuclear Information System (INIS)

[en] The measurements obtained by Mars 5 reaffirm the conclusion of an intrinsic Martian magnetic field based on the Mars 2 and 3 data. The bow shock positions are equivalent to those observed on the earlier missions. Furthermore, a magnetotail is observed whose direction is independent of interplanetary sector structure

1978-01-01

420

The Peierls transition under high magnetic field  

Energy Technology Data Exchange (ETDEWEB)

The dependence on magnetic field of the Peierls transition has been clearly measured on the quasi-one-dimensional compound Per{sub 2}[Au(mnt){sub 2}]. A quadratic dependence of the transition temperature has been found, in agreement with the theoretical predictions. (orig.).

Bonfait, G. [Departamento de Quimica, ICEN-INETI, P2686 Sacavem Codex (Portugal); Matos, M.J. [Departamento de Quimica, ICEN-INETI, P2686 Sacavem Codex (Portugal); Henriques, R.T. [Departamento de Quimica, ICEN-INETI, P2686 Sacavem Codex (Portugal); Almeida, M. [Departamento de Quimica, ICEN-INETI, P2686 Sacavem Codex (Portugal)

1995-05-01

 
 
 
 
421

Flight deck magnetic fields in commercial aircraft.  

UK PubMed Central (United Kingdom)

BACKGROUND: Airline pilots are exposed to magnetic fields generated by the aircraft's electrical system. The objectives of this study were (1) to directly measure flight deck magnetic fields in terms of personal exposure to the pilots when flying on different aircraft types over a 75-hour flight-duty month, and (2) to compare magnetic field exposures across flight deck types and job titles. METHODS: Measurements were taken using personal dosimeters carried by either the Captain or the First Officer on Boeing 737/200, Boeing 747/400, Boeing 767/300ER, and Airbus 320 aircraft. RESULTS: Approximately 1,008 block hours were recorded at a sampling frequency of 3 seconds. Total block time exposure to the pilots ranged from a harmonic geometric mean of 6.7 milliGauss (mG) for the Boeing 767/300ER to 12.7 mG for the Boeing 737/200. CONCLUSIONS: Measured flight deck magnetic field levels were substantially above the 0.8-1 mG level typically found in the home or office and suggest the need for further study to evaluate potential health effects of long-term exposure.

Nicholas JS; Butler GC; Lackland DT; Hood WC Jr; Hoel DG; Mohr LC Jr

2000-11-01

422

Calculation of magnetic field of helical coils  

International Nuclear Information System (INIS)

Formulae of magnetic field calculation of finite size helical coils with rectangular cross section are extended to the case that the size of the coil, or the relative position to the guiding curve, varies along the arc length of the guiding curve. The error caused by the inappropriate formulae or inappropriate current model is discussed. (author).

1990-01-01

423

Large TileCal magnetic field simulation.  

Science.gov (United States)

The ATLAS magnetic field map has been estimated in the presence of the hadron tile calorimeter. This is an important issue in order to quantify the needs for individual PMT shielding, the effect on the scintillator light yield and its implications on the ...

M. Nessi F. Bergsma S. B. Vorozhtsov O. N. Borisov O. V. Lomakina

1994-01-01

424

UHECR propagation in the Galactic Magnetic Field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Extensive simulations of the ultra-high energy cosmic ray (UHECR) propagation in the Galactic magnetic field (GMF) have been performed, and the results are presented. The use of different available models of the large-scale GMF and/or primary particle assumptions leads to distinctly different deflec...

Vorobiov, Serguei; Hussain, Mustafa; Veberi?, Darko

425

Strain sensors for high field pulse magnets  

Energy Technology Data Exchange (ETDEWEB)

In this paper we present an investigation into several strain sensing technologies that are being considered to monitor mechanical deformation within the steel reinforcement shells used in high field pulsed magnets. Such systems generally operate at cryogenic temperatures to mitigate heating issues that are inherent in the coils of nondestructive, high field pulsed magnets. The objective of this preliminary study is to characterize the performance of various strain sensing technologies at liquid nitrogen temperatures (-196 C). Four sensor types are considered in this investigation: fiber Bragg gratings (FBG), resistive foil strain gauges (RFSG), piezoelectric polymers (PVDF), and piezoceramics (PZT). Three operational conditions are considered for each sensor: bond integrity, sensitivity as a function of temperature, and thermal cycling effects. Several experiments were conducted as part of this study, investigating adhesion with various substrate materials (stainless steel, aluminum, and carbon fiber), sensitivity to static (FBG and RFSG) and dynamic (RFSG, PVDF and PZT) load conditions, and sensor diagnostics using PZT sensors. This work has been conducted in collaboration with the National High Magnetic Field Laboratory (NHMFL), and the results of this study will be used to identify the set of sensing technologies that would be best suited for integration within high field pulsed magnets at the NHMFL facility.

Martinez, Christian [Los Alamos National Laboratory; Zheng, Yan [Los Alamos National Laboratory; Easton, Daniel [Los Alamos National Laboratory; Farinholt, Kevin M [Los Alamos National Laboratory; Park, Gyuhae [Los Alamos National Laboratory

2009-01-01

426

Magnetic fields in noncommutative quantum mechanics  

CERN Multimedia

We discuss various descriptions of a quantum particle on noncommutative space in a (possibly non-constant) magnetic field. We have tried to present the basic facts in a unified and synthetic manner, and to clarify the relationship between various approaches and results that are scattered in the literature.

Delduc, Francois; Gieres, Francois; Lefrancois, Matthieu

2007-01-01

427

Topics in the physics of high magnetic fields  

International Nuclear Information System (INIS)

The strong magnetic fields expected to exist in neutron stars affect strongly the thermodynamic and transport properties of matter. Topics discussed here are Thomas-Fermi type theories of matter in high magnetic fields, the general expression for magnetic forces in a non-linear magnetic medium, and ambipolar diffusion as a mechanism for field decay in neutron star interiors. (orig.)

1991-01-01

428

Coordinate noncommutativity in strong non-uniform magnetic fields  

CERN Multimedia

Noncommuting spatial coordinates are studied in the context of a charged particle moving in a strong non-uniform magnetic field. We derive a relation involving the commutators of the coordinates, which generalizes the one realized in a strong constant magnetic field. As an application, we discuss the noncommutativity in the magnetic field present in a magnetic mirror.

Frenkel, J

2004-01-01

429

Electrical conductivity of quark matter in magnetic field  

CERN Multimedia

Fermion currents in dense quark matter embedded into magnetic field are under intense discussions motivated by Chiral Magnetic Effect. We argue that conductivity of quark matter may be independent of the magnetic field direction and not proportional to the magnetic field strength.

Kerbikov, B

2011-01-01