WorldWideScience
1

Octupole magnet for expansion of irradiation area  

Energy Technology Data Exchange (ETDEWEB)

An octupole magnet for experiments is designed to prove a scheme for expanding beam irradiation area with good flatness. The length and maximum strength of the octupole field 1/3{exclamation_point} B``` are 0.6 m and 4000 T/m{sup 3}, respectively. (author)

Morita, Akio; Inoue, Makoto; Noda, Akira; Iwashita, Yoshihisa; Shirai, Toshiyuki; Urakabe, Eriko [Kyoto Univ., Uji (Japan). Inst. for Chemical Research; Hiramoto, Kazuo; Noda, Kouji

1997-12-31

2

Ion heating at the cyclotron resonance in plasmas magnetically confined in a toroidal octupole field  

International Nuclear Information System (INIS)

Ion temperatures as high as 600 eV have been produced using rf wave heating at the ion cyclotron resonance frequency in a toroidal octupole magnetic field. Rf is coupled to the plasma with an externally driven ''fifth'' hoop which forms the inductive leg of an oscillator tank circuit. Power levels up to 1 MW at 1 to 3 MHz have been applied for periods up to 2 msec. Plasmas produced either by ECRH or by gun injection are simulated with a computer program in which known particle and energy production and loss mechanisms are used to predict the spatially averaged time behaviour of the plasma in the presence of the applied ion heating. The program can be used to calculate the consequences of the heating model in the presence of many cooling mechanisms which may each have a separate dependence on instantaneous plasma parameters. Experimental quantities compared to computer predictions include density, ion temperature, and loading of the hoop by the plasma, both resistive and reactive, and neutral reflux from the wall by electron and ion impact. Wave penetration to the resonance zone is good up to the highest densities available (6 x 1012 cm-3 by gun injection) in good agreement with theory. Neutral reflux from the walls and the large charge exchange cooling which results is the dominant loss mechanism at the higher hoop voltages

3

Fifth-order aberrations in magnetic quadrupole-octupole systems  

International Nuclear Information System (INIS)

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

4

Octupole Magnet For Soft X Ray Magnetic Dichroism Experiments: Design and Performance  

Science.gov (United States)

An octupole magnet endstation for soft x ray magnetic dichroism measurements has been developed at the Advanced Light Source. The system consists of an eight pole electromagnet that surrounds a small vacuum chamber. The magnet provides fields up to 0.9 T that can be applied in any direction relative to the incoming x ray beam. High precision magnetic circular and linear dichroism spectra can be obtained reversing the magnetic field for each photon energy in an energy scan. Moreover, the field dependence of all components of the magnetization vector can be studied in detail by choosing various angles of x ray incidence while keeping the relative orientation of magnetic field and sample fixed.

Arenholz, Elke; Prestemon, Soren O.

2004-05-01

5

Octupole magnet for soft X ray magnetic dichroism experiments: Design and performance  

International Nuclear Information System (INIS)

An octupole magnet endstation for soft x-ray magnetic dichroism measurements has been developed at the Advanced Light Source. The system consists of an eight pole electromagnet that surrounds a small vacuum chamber. The magnet provides fields up to 0.9 T that can be applied in any direction relative to the incoming x-ray beam. High precision magnetic circular and linear dichroism spectra can be obtained reversing the magnetic field for each photon energy in an energy scan. Moreover, the field dependence of all components of the magnetization vector can be studied in detail by choosing various angles of x-ray incidence while keeping the relative orientation of magnetic field and sample fixed

6

Octupole Magnet For Soft X Ray Magnetic Dichroism Experiments: Design and Performance  

International Nuclear Information System (INIS)

An octupole magnet endstation for soft x ray magnetic dichroism measurements has been developed at the Advanced Light Source. The system consists of an eight pole electromagnet that surrounds a small vacuum chamber. The magnet provides fields up to 0.9 T that can be applied in any direction relative to the incoming x ray beam. High precision magnetic circular and linear dichroism spectra can be obtained reversing the magnetic field for each photon energy in an energy scan. Moreover, the field dependence of all components of the magnetization vector can be studied in detail by choosing various angles of x ray incidence while keeping the relative orientation of magnetic field and sample fixed

7

Specifications of the octupole magnets required for the ATF2 ultra-low ß* lattice  

Energy Technology Data Exchange (ETDEWEB)

The Accelerator Test Facility 2 (ATF2) aims to test the novel chromaticity correction for higher chromaticity lattices as the one of CLIC. To this end the ATF2 ultra-low ß* lattice is designed to vertically focus the beam at the focal point or usually referred to as interaction point (IP), down to 23 nm. However when the measured multipole components of the ATF2 magnets are considered in the simulations, the evaluated spot sizes at the IP are well above the design value. The designed spot size is effectively recovered by inserting a pair of octupole magnets. In this note we address the technical specifications required for these octupole magnets.

Marin, E.; /SLAC; Modena, M.; /CERN; Tauchi, T.; Terunuma, N.; /KEK, Tsukuba; Tomas, R.; /CERN; White, G.R.; /SLAC

2014-05-28

8

Specifications of the octupole magnets required for the ATF2 ultra-low ?* lattice  

International Nuclear Information System (INIS)

The Accelerator Test Facility 2 (ATF2) aims to test the novel chromaticity correction for higher chromaticity lattices as the one of CLIC. To this end the ATF2 ultra-low ?* lattice is designed to vertically focus the beam at the focal point or usually referred to as interaction point (IP), down to 23 nm. However when the measured multipole components of the ATF2 magnets are considered in the simulations, the evaluated spot sizes at the IP are well above the design value. The designed spot size is effectively recovered by inserting a pair of octupole magnets. In this note we address the technical specifications required for these octupole magnets

9

A comparison of two magnetic ultra-cold neutron trapping concepts using a Halbach-octupole array  

CERN Document Server

This paper describes a new magnetic trap for ultra-cold neutrons (UCNs) made from a 1.2 m long Halbach-octupole array of permanent magnets with an inner bore radius of 47 mm combined with an assembly of superconducting end coils and bias field solenoid. The use of the trap in a vertical, magneto-gravitational and a horizontal setup are compared in terms of the effective volume and ability to control key systematic effects that need to be addressed in high precision neutron lifetime measurements.

Leung, K; Martin, F; Rosenau, F; Simson, M; Zimmer, O

2015-01-01

10

Quadrupole magnet field mapping for FRIB  

International Nuclear Information System (INIS)

Extensive magnetic field map measurements have been done on a newly built superconducting quadrupole triplet with sextupole and octupole coils nested within every quadrupole. The magnetic field multipole composition and fringe field distributions have been analyzed and an improved parameterization of the field has been developed within the beam transport simulation framework. Parameter fits yielding standard deviations as low as 0.3% between measured and modeled values are reported here

11

Quadrupole magnet field mapping for FRIB  

Energy Technology Data Exchange (ETDEWEB)

Extensive magnetic field map measurements have been done on a newly built superconducting quadrupole triplet with sextupole and octupole coils nested within every quadrupole. The magnetic field multipole composition and fringe field distributions have been analyzed and an improved parameterization of the field has been developed within the beam transport simulation framework. Parameter fits yielding standard deviations as low as 0.3% between measured and modeled values are reported here.

Portillo, M., E-mail: portillo@frib.msu.edu [Facility for Rare Isotope Beams, Michigan State University, East Lansing, MI (United States); Amthor, A.M.; Chouhan, S. [Facility for Rare Isotope Beams, Michigan State University, East Lansing, MI (United States); Cooper, K.; Gehring, A. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States); Hausmann, M. [Facility for Rare Isotope Beams, Michigan State University, East Lansing, MI (United States); Hitchcock, S.; Kwarsick, J. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States); Manikonda, S. [Argonne National Laboratory, Argonne, IL (United States); Sumithrarachchi, C. [National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI (United States)

2013-12-15

12

Octupole Ordering Model for the Phase IV of CexLa1-xB6  

CERN Document Server

An octupole ordering model is studied by the mean field theory, and its relevance to the phase IV of CexLa1-xB6 is discussed. The observed lattice distortion along the [111] direction is interpreted in terms of the \\Gamma_{5g}-type ferro-quadrupole moment induced by an antiferro-octupole ordered state with \\Gamma_{5u} symmetry. The octupole model also accounts for the cusp in the magnetization as in the N\\'{e}el transition, and the softening of the elastic constant C_{44} below the ordering temperature. However, the internal magnetic field due to the octupole moment is smaller than the observed one by an order of magnitude. Also discussed is the possibility of a pressure induced antiferromagnetic moment in the octupole-ordered state.

Kubo, K; Kubo, Katsunori; Kuramoto, Yoshio

2003-01-01

13

Measuring the Nuclear Magnetic Octupole Moment of a Single Trapped Barium-137 Ion  

Science.gov (United States)

Recent measurements of hyperfine structure in the cesium-133 atom resolved a nuclear magnetic octupole moment ? much larger than expected from the nuclear shell model[1]. To explore this issue further, we are undertaking an experiment to measure the hyperfine structure in the 5D manifold of a single trapped barium-137 ion which, together with reliable calculations in alkali-like Ba^+, should resolve ? with sensitivity better than the shell model value [2]. We use a TmHo:YLF laser tuned to 2051 nm and a fiber laser tuned to 1762 nm to drive the 6S1/2 to 5D3/2 and 6S1/2 to 5D5/2 electric quadrupole transitions. These lasers allow us to selectively populate any hyperfine sub-level in the 5D manifold. We will then perform RF spectroscopy on the 5D states to make a precision measurement of the hyperfine frequency intervals. We report on the development of the laser and RF spectroscopy systems. [1] V. Gerginov, A. Derevianko, and C. E. Tanner, Phys. Rev. Lett. 91, 072501 [2] K. Beloy, A. Derevianko, V. A. Dzuba, G. T. Howell, B. B. Blinov, E. N. Fortson, arXiv:0804.4317v1 [physics.atom-ph] 28 Apr 2008

Kleczewski, Adam; Fortson, Norval; Blinov, Boris

2009-05-01

14

Low-field octupoles and high-field quadrupoles in URu2Si2  

CERN Document Server

The recent experimental finding of large-amplitude antiferromagnetism induced by uniaxial strain shows that the "hidden" low-field order of URu2Si2 breaks time reversal invariance. We propose a new crystal field model which supports T(beta)z octupolar order in the low-field phase, and quadrupolar order in a disjoint high-field phase. The temperature dependence of the linear and third order magnetic susceptibility is in good agreement with the observed behavior.

Kiss, A; Kiss, Annamaria; Fazekas, Patrik

2004-01-01

15

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 Earth's magnetic field on a compass. Students see the connection that the compass simply responds to the Earth's magnetic field since it is the closest, strongest field, and thus the compass responds 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,

16

Magnetic octupole order in Ce0.7La0.3B6: A polarized neutron diffraction study  

International Nuclear Information System (INIS)

Recently, in phase IV of CexLa1-xB6, 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 Ce0.7La0.3B6. 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 CexLa1-xB6.

17

Time-resolved soft-x-ray spectroscopy of a magnetic octupole transition in nickel-like xenon, cesium, and barium ions  

Energy Technology Data Exchange (ETDEWEB)

A microcalorimeter with event mode capability for time-resolved soft-x-ray spectroscopy, and a high-resolution flat-field EUV spectrometer have been employed at the Livermore EBIT-I electron beam ion trap for observations and wavelength measurements of M1, E2, and M3 decays of long-lived levels in the Ni-like ions Xe{sup 26+}, Cs{sup 27+}, and Ba{sup 28+}. Of particular interest is the lowest excited level, 3d{sup 9}4s {sup 3}D{sub 3}, which can only decay via a magnetic octupole (M3) transition. For this level in Xe an excitation energy of (590.40 {+-} 0.03eV) and a level lifetime of (11.5 {+-} 0.5 ms) have been determined.

Trabert, E; Beiersdorfer, P; Brown, G V; Boyce, K; Kelley, R L; Kilbourne, C A; Porter, F S; Szymkowiak, A

2005-11-11

18

Hyperfine structure of the metastable P32 state of alkaline-earth-metal atoms as an accurate probe of nuclear magnetic octupole moments  

Science.gov (United States)

Measuring the hyperfine structure (HFS) of long-lived P32 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 S87r needed to reveal the perturbation caused by the nuclear octupole moment is on the order of kHz. The results of similar analyses for B9e , M25g , and C43a are also reported.

Beloy, K.; Derevianko, A.; Johnson, W. R.

2008-01-01

19

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

20

The octupoles take pole position  

CERN Multimedia

The first preseries octupole magnet was delivered to CERN in December 2001. Hooked up to a main quadrupole magnet, its function will be to correct imperfections in the beams. The LHC will be fitted with about 5000 corrector magnets, whose task it will be to provide maximum precision in beam collisions.

2002-01-01

21

Magnetic Field  

DEFF Research Database (Denmark)

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

Olsen, Nils

2015-01-01

22

Effect of the lattice octupole fields on the synchro-betatron mode coupling instability  

Science.gov (United States)

Within the framework of a simplifying model and in the first approximation of the perturbation theory we discuss the effect of the Landau damping on the synchro-betatron mode coupling instability of a single bunch in a storage ring. We assume that the required by Landau damping frequency spreads of the betatron and of the synchro-betatron modes are provided by the octupole nonlinearity of the ring lattice focusing. We also assume that the wakefields of the bunch decay substantially during the revolution period of particles along the closed orbit. For this reason, the memory of the bunch wakefields are ignored in this paper.

Pestrikov, D. V.

2014-02-01

23

Effect of the lattice octupole fields on the synchro-betatron mode coupling instability  

Energy Technology Data Exchange (ETDEWEB)

Within the framework of a simplifying model and in the first approximation of the perturbation theory we discuss the effect of the Landau damping on the synchro-betatron mode coupling instability of a single bunch in a storage ring. We assume that the required by Landau damping frequency spreads of the betatron and of the synchro-betatron modes are provided by the octupole nonlinearity of the ring lattice focusing. We also assume that the wakefields of the bunch decay substantially during the revolution period of particles along the closed orbit. For this reason, the memory of the bunch wakefields are ignored in this paper.

Pestrikov, D.V., E-mail: pestrikov@inp.nsk.su [Budker Institute of Nuclear Physics, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation)

2014-02-21

24

Lattice Distortion and Octupole Ordering Model in CexLa1-xB6  

CERN Document Server

Possible order parameters of the phase IV in CexLa1-xB6 are discussed with special attention to the lattice distortion recently observed. A \\Gamma_{5u}-type octupole order with finite wave number is proposed as the origin of the distortion along the [111] direction. The \\Gamma_8 crystalline electric field (CEF) level splits into three levels by a mean field with the \\Gamma_{5u} symmetry. The ground and highest singlets have the same quadrupole moment, while the intermediate doublet has an opposite sign. It is shown that any collinear order of \\Gamma_{5u}-type octupole moment accompanies the \\Gamma_{5g}-type ferro-quadrupole order, and the coupling of the quadrupole moment with the lattice induces the distortion. The cusp in the magnetization at the phase transition is reproduced, but the internal magnetic field due to the octupole moment is smaller than the observed one by an order of magnitude.

Kubo, K; Kubo, Katsunori; Kuramoto, Yoshio

2003-01-01

25

A Hall Attractor in Axially Symmetric Magnetic Fields  

CERN Document Server

We have found an attractor for an axially symmetric magnetic field evolving under the Hall effect and subdominant Ohmic dissipation, resolving the question of the long term fate of the magnetic field in neutron star crusts. The electron fluid is in isorotation, analogous to Ferraro's law, with its angular velocity being approximately proportional to the poloidal magnetic flux, $\\Omega \\propto \\Psi$. This equilibrium is the long term configuration of a magnetic field evolving because of the Hall effect and Ohmic dissipation. For an initial dipole dominated field the attractor consists mainly of a dipole and an octupole component accompanied by an energetically negligible quadrupole toroidal field. The field dissipates in a self-similar way: although higher multipoles should have been decaying faster, the toroidal field mediates transfer of energy into them from the lower ones, leading to an advection diffusion equilibrium and keeping the ratio of the poloidal multipoles almost constant. This has implications f...

Gourgouliatos, Konstantinos N

2013-01-01

26

A novel structure of multipole field magnets and their applications in uniformizing beam spot at target  

International Nuclear Information System (INIS)

A novel structure of multipole field magnets is proposed, and it can provide any order either symmetric or anti-symmetric field distribution within a good-field region in a flat rectangular shape with relative field errors of about 1%. Some of these field distributions cannot be obtained by standard multipole magnets but are quite useful in some applications, thanks to the decoupling of the two halves of the magnets by a pair of shielding plates. In addition, the simplified structure compared with the standard one makes the magnet fabrication easier and cost effective. Two-dimensional magnetic field calculations for anti-symmetric sextupole, octupole, decapole and dodecapole fields show that the new types of multipole magnets have good field quality. Three-dimensional magnetic field calculations have confirmed the validity of the two-dimensional calculations. Symmetric field distributions by the simplified multipole field magnets have also been confirmed by two-dimensional field calculations. Two application examples by using numerical simulations are also given to show the effectiveness of simplified multipole field magnets in producing uniform-like beam spots at two different targets with different beam inputs. It is also shown that combinations of the lower order anti-symmetric field magnets – a merit of this magnet structure – are more advantageous than the traditional combination of octupole and dodecapole magnets in beam spot uniformization, besides with cheaper construction and operation costs. The applications of non-standard field distributions such as anti-symmetric sextupole and symmetric octupole field distributions in synchrotrons are to be exploited in the future.

27

Explaining Mercury's peculiar magnetic field  

Science.gov (United States)

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

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

2014-05-01

28

Exploring Magnetic Field Lines  

Science.gov (United States)

In this activity, learners explore the magnetic field of a bar magnet as an introduction to understanding Earth's magnetic field. First, learners explore and play with magnets and compasses. Then, learners trace the field lines of the magnet using the compass on a large piece of paper. This activity will also demonstrate why prominences are always "loops."

2012-06-26

29

Magnetic field sensor  

Science.gov (United States)

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

Silva, Nicolas

2012-09-01

30

Exploring Magnetic Fields  

Science.gov (United States)

This is an activity about magnetic fields. Using iron filings, learners will observe magnets in various arrangements to investigate the magnetic field lines of force. This information is then related to magnetic loops on the Sun's surface and the magnetic field of the Earth. This is the second activity in the Exploring the Earth's Magnetic Field: An IMAGE Satellite Guide to the Magnetosphere educators guide.

2012-08-03

31

Magnetic Fields Matter  

Science.gov (United States)

This lesson introduces students to the effects of magnetic fields in matter addressing permanent magnets, diamagnetism, paramagnetism, ferromagnetism, and magnetization. First students must compare the magnetic field of a solenoid to the magnetic field of a permanent magnet. Students then learn the response of diamagnetic, paramagnetic, and ferromagnetic material to a magnetic field. Now aware of the mechanism causing a solid to respond to a field, students learn how to measure the response by looking at the net magnetic moment per unit volume of the material.

VU Bioengineering RET Program, School of Engineering,

32

Visualizing Magnetic Field Lines  

Science.gov (United States)

In this activity, students take the age old concept of etch-a-sketch a step further. Using iron filings, students begin visualizing magnetic field lines. To do so, students use a compass to read the direction of the magnet's magnetic field. Then, students observe the behavior of iron filings near that magnet as they rotate the filings about the magnet. Finally, students study the behavior of iron filings suspended in mineral oil which displays the magnetic field in three dimensions.

VU Bioengineering RET Program, School of Engineering,

33

What are Magnetic Fields?  

Science.gov (United States)

This is an activity about magnetic fields. Using iron filings, learners will observe magnets in various arrangements to investigate the magnetic field lines of force. This information is then related to magnetic loops on the Sun's surface and the magnetic field of the Earth. This is the second activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.

34

Microscopic description of octupole-phonon alignment in the actinides  

Energy Technology Data Exchange (ETDEWEB)

A microscopic model, based on an approach that combines the ideas of the cranking model and the random-phase approximation, is formulated for the description of the vibrational octupole states. The mean field is approximated by a rotating Nilsson potential with allowance for monopole pairing. The residual interaction is made up of separable octupole--octupole interactions of the isoscalar and isovector types with negative signature. An empirical formula establishing a relation between the vibrational excitation energy and the aligned vibrational angular momentum as a function of the angular velocity is proposed. The alignment of the vibrational octupole angular momentum for the states of the K/sup ..pi../ = 0/sup -/ band of the /sup 230,232/Th and /sup 238/U nuclei is analyzed. A qualitative correspondence of the nature of the branching of the electric dipole transitions from the octupole states into the yrast-line states in these nuclei is obtained.

Nazmitdinov, R.G.

1987-09-01

35

Microscopic description of the octupole phonon alignment in actinides  

International Nuclear Information System (INIS)

The microscopic model based on the cranking random phase approximation for the description of the vibrational octupole states is formulated. The average field is approximated by the rotating nilsson potential witn monopole pairing. The hamiltonian of the model contains both isoscalar and isovector components of the separable octupole-octupole interaction of the negative signature. The empirical relation between the excitation energy and aligned angular momentum of the vibrational state from the dependence of the angular frequency is suggested. The alignment of the vibrational octupole angular momentum in the states of the Kn=0- band of 238U and 230,232Th is analysed. A qualitative correspondence of the behaviour of the branching of dipole electric transitions for these nuclei from the octupole states to the yrast states is obtained

36

Microscopic description of octupole-phonon alignment in the actinides  

International Nuclear Information System (INIS)

A microscopic model, based on an approach that combines the ideas of the cranking model and the random-phase approximation, is formulated for the description of the vibrational octupole states. The mean field is approximated by a rotating Nilsson potential with allowance for monopole pairing. The residual interaction is made up of separable octupole--octupole interactions of the isoscalar and isovector types with negative signature. An empirical formula establishing a relation between the vibrational excitation energy and the aligned vibrational angular momentum as a function of the angular velocity is proposed. The alignment of the vibrational octupole angular momentum for the states of the K/sup ?/ = 0- band of the /sup 230,232/Th and /sup 238/U nuclei is analyzed. A qualitative correspondence of the nature of the branching of the electric dipole transitions from the octupole states into the yrast-line states in these nuclei is obtained

37

Experimental tests for stable octupole deformation in actinium-227  

International Nuclear Information System (INIS)

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

38

Mapping Magnetic Fields  

Science.gov (United States)

This is an activity about bar magnets and their invisible magnetic fields. Learners will experiment with magnets and a compass to detect and draw magnetic fields. This is Activity 1 of a larger resource, entitled Exploring the Sun. The NASA spacecraft missions represented by this material include SOHO, TRACE, STEREO, Hinode, and SDO.

2012-08-03

39

The Earth's Magnetic Field  

OpenAIRE

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

Edda Lína Gunnarsdóttir 1988

2012-01-01

40

Plasma resistivity measurements in the Wisconsin levitated octupole  

International Nuclear Information System (INIS)

Resistivity measurements parallel to the magnetic field were made on gun injected plasmas ranging in density from 109cm-3 to 101parallelcm-3 in the Wisconsin levitated octupole with toroidal and poloidal magnetic fields. The 109cm-3 plasma was collisionless with lambda/sub mfp/ > 100 mirror lengths, had T/sub e/ = 10 eV, T/sub i/ = 30 eV and was found to have anomalous resistivity scaling like eta = ?T/sub e//n/sub e/ when E/sub parallel/ > E/su c/ is the Dreicer critical field. The 1012cm-3 plasma was collisional with lambda/sub mfp/ < mirror length, had T/sub e/ = T/sub i/ approx. = .2 eV and was found to have Spitzer resistivity when E/sub parallel/ < E/sub c/

41

Drawing Magnetic Fields  

Science.gov (United States)

Students use a compass and a permanent magnet to trace the magnetic field lines produced by the magnet. By positioning the compass in enough spots around the magnet, the overall magnet field will be evident from the collection of arrows representing the direction of the compass needle. In activities 3 and 4 of this unit, students will use this information to design a way to solve the grand challenge of separating metal for a recycling company.

VU Bioengineering RET Program,

42

The Magnetic Field  

Science.gov (United States)

This demonstration of the magnetic field lines of Earth uses a bar magnet, iron filings, and a compass. The site explains how to measure the magnetic field of the Earth by measuring the direction a compass points from various points on the surface. There is also an explanation of why the north magnetic pole on Earth is actually, by definition, the south pole of a magnet.

Jeffrey Barker

43

Neoclassical currents in the Wisconsin Levitated Octupole  

International Nuclear Information System (INIS)

Neoclassical transport theory predicts the existence of bootstrap current in collisionless plasmas with a significant population of trapped particles. This unidirectional current flows along field lines, and is generated by the balancing of ion-electron friction forces with the viscous forces between trapped and untrapped like particles. The current is driven by gradients in the plasma pressure and temperature. Previous work has identified the existence of bootstrap current in the Wisconsin Levitated Octupole, and this discovery of bootstrap current in the octupole naturally leads to the question of why previous experiments were unsuccessful in their endeavors to identify this current. The original motivation for this thesis was to address that question, by investigating the effects on bootstrap current caused by ohmic currents, plasma fluctuations, and rf fields. Ohmic currents, while naturally present in tokamaks, can be introduced in the octupole, independent of the usual operating procedure, and can be adjusted to be of the same order of magnitude as the expected diamagnetic and parallel currents. The interaction, if any, of bootstrap current and ohmic current can thus be determined without the problem of a large ohmic current masking the neoclassical current. Rf fields can be driven in the octupole plasma with little or no plasma heating. Any anomalous effects on the parallel currents, due to the existence of the rf fields, can then be determined. This thesis consists of four parts: the experimental apparatus and the plasma diagnostics used in these studies; the general theory of neoclassical currents (excluding field errors) and how it is applied to the octupole; the experimental results of this investigation; and a brief discussion of the conclusions that can be inferred from the data

44

Circuits and Magnetic Fields  

Science.gov (United States)

Students use the same method as in the activity from lesson 2 of this unit to explore the magnetism due to electric current instead of a permanent magnet. Students use a compass and circuit to trace the magnetic field lines induced by the electric current moving through the wire. Students develop an understanding of the effect of the electrical current on the compass needle through the induced magnetic field and understand the complexity of a three dimensional field system.

VU Bioengineering RET Program,

45

Magnetic Field Problem  

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. The color of the arrows represents the magnitude of the field with magnitude increasing as the color changes from blue to green to red to black. You may drag either magnet and double-click anywhere inside the animation to add a magnetic field line, and mouse-down to read the magnitude of the magnetic field at that point.

Wolfgang Christian

46

Magnetic field measuring device  

International Nuclear Information System (INIS)

In order to directly measure the magnetic fields in the vicinity of plasmas in a thermonuclear device, electric current is supplied to a conductor intersecting magnetic fields, and the position of the conductor is changed by generated electromagnetic forces, and the positional change of the conductor is measured to determine the magnetic fields. Namely, if electric current is supplied to the conductor crossing the magnetic fields, electromagnetic forces directly in proportion to the magnetic fields exert on the object. If the forces are measured, magnetic fields can be determined directly without using an integrator. If springs are attached to the conductor undergoing electromagnetic forces, as a method of measuring electromagnetic forces, since the distortion is in proportion to the electromagnetic forces, magnetic fields can be determined, for example, by changing the position of a contact of a variable resistor interlocking with the positional change of the spring. Since a semiconductor device which is sensitive to radiation is not necessary and the magnetic fields can be measured directly in this method for the measurement of the magnetic fields, the measurement can be conducted at a constant accuracy even in a long period of time. The device of the present invention can measure magnetic fields with no drift components of the integrator, has excellent radiation-resistance and can improve the plant safety. (N.H.)

47

Magnetic field measuring device  

International Nuclear Information System (INIS)

If signal voltages are integrated with lapse of time in a thermonuclear device, erroneous voltages are also integrated with lapse of time thereby resulting in occurrence of measuring errors increased with lapse of time, and continuous measurement for magnetic fields at high accuracy for a long period of time has been difficult. Then, a movable coil is disposed in the magnetic fields to be measured in order to directly measure the magnetic fields at the periphery of the plasmas, and electric current is supplied to the coil and resulted electromagnetic force is measured to obtain a magnetic field. If electric current is supplied to the coil in the magnetic fields, electromagnetic force (rotational torque) directly in proportion to the magnetic fields is generated. If the electromagnetic force is measured, magnetic fields can be determined directly without using an integrator. If a resistor wire is disposed on one end of the coil so that the resistor wire extends/shrinks by the electromagnetic force and changes the resistance value, the electromagnetic force can be determined from the magnetic fields based on the change of the resistance values. Since the measurement using magnetic fields does not require semiconductor devices which are sensitive to radiation, and the magnetic fields can be measured directly, the measurement can be conducted at a constant accuracy even for a long period of time. (N.H.)

48

Octupole Excitation of Trapped Ion Motion for Precision Mass Measurements  

Science.gov (United States)

National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, MI, USA An azimuthal octupole radiofrequency field has been used to excite the ion motion of ^40Ar^+ ions stored in a Penning trap. A resonant response was observed at twice the ions' true cyclotron frequency ?c=q/m.B. The experiment has been performed with the 9.4-T Penning trap system of the recently commissioned LEBIT facility at the NSCL at MSU [1]. Similar to the excitation with an azimuthal quadrupole field at ?c [2,3], octupole excitation at 2?c gives rise to a periodic beating of the ion motion between magnetron and reduced cyclotron motion. Differences are observed in the dependence of the excited ion motion on initial amplitudes and phases of the radial eigen motions. The observed behavior of the ions is found to be in good agreement with the results of numerical simulations. The technique still requires further testing but the first results indicate that 2?c excitation may provide benefits that are similar to doubling the magnetic field strength B. In particular precision mass measurements of short-lived rare isotopes may benefit from this technique by being able to reach a given precision with shorter ion storage and observation times. [1] S. Schwarz et al, Nucl. Instr. Meth. B204 (2004) 507 [2] G. Bollen et al., J. Appl. Phys. 68 (1990) 4355 [3] M. König et al., Int. J. Mass Spec. Ion. Proc. 142 (1995) 95

Bollen, G.; Ringle, R.; Schury, P.; Schwarz, S.; Sun, T.

2005-04-01

49

The First Magnetic Fields  

CERN Document Server

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

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

2011-01-01

50

Mapping Magnetic Field Lines  

Science.gov (United States)

This is a lesson about the magnetic field of a bar magnet. The lesson begins with an introductory discussion with learners about magnetism to draw out any misconceptions that may be in their minds. Then, learners freely experiment with bar magnets and various materials, such as paper clips, rulers, copper or aluminum wire, and pencils, to discover that magnets attract metals containing iron, nickel, and/or cobalt but not most other materials. Next, learners experiment with using a magnetic compass to discover how it is affected by the magnet and then draw the magnetic field lines of the magnet by putting dots at the location of the compass arrow. This is the first lesson in the first session of the Exploring Magnetism teacher guide.

51

Octupole shapes in heavy nuclei  

International Nuclear Information System (INIS)

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

52

The Magnetic Field  

Science.gov (United States)

This webpage is part of the University Corporation for Atmospheric Research (UCAR) Windows to the Universe program. It describes the nature and configuration of magnetic fields, which are the result of moving electric charges, including how they cause magnetic objects to orient themselves along the direction of the magnetic force points, which are illustrated as lines. Magnetic field lines by convention point outwards at the north magnetic pole and inward at the south magnetic pole. The site features text, scientific illustrations and an animation. Text and vocabulary are selectable for the beginning, intermediate, or advanced reader.

Windows to the Universe

1997-12-03

53

Voyager 1 assessment of Jupiter's planetary magnetic field  

International Nuclear Information System (INIS)

A new estimate of Jupiter's planetary magnetic field is obtained from the Voyager 1 observations of the Jovian magnetosphere. An explicit model for the magnetodisc current system is combined with spherical harmonic model of the planetary field with both sets of parameters determined simulataneously by using a nonlinear generalized inverse methodology. The resulting model fits the observations extremely well throughout the analysis interval (r>20 R/sub j/). The Jovian internal field model obtained from the Voyager 1 data is very similar to the octupole Pioneer 11 models. The best fitting magnetodisc lies in the centrifugal equator, 2/3 of the way between the rotational and magnetic equators, as is appropriate for centrifugal loading of the magnetosphere by a cold plasma. No statistically significant evidence is found for secular change of the equivalent dipole estimated from Pioneer 11 (1974.9) and Voyager 1 (1979.2) data

54

Lower hybrid heating associated with mode conversion on the Wisconsin octupole  

International Nuclear Information System (INIS)

This thesis addresses the following key issues in the lower hybrid frequency range: (1) what are the important physics aspects of wave propagation and heating in an experimental situation; (2) how effective is plasma heating in the complex magnetic field configuration of the octupole. Experimental work is accomplished by launching 1-10 ms pulses of up to 40 kW of radio frequency power at 140 MHz corresponding to the hot plasma lower hybrid resonance in the octupole. A dipole antenna which is moveable radially and is also rotatable couples wave power to the plasma. Coupling efficiencies greater than 95% are achieved by proper antenna placement near the edge of the plasma radial density profile

55

Lower hybrid heating associated with mode conversion on the Wisconsin octupole  

Energy Technology Data Exchange (ETDEWEB)

This thesis addresses the following key issues in the lower hybrid frequency range: 1. What are the importent physics aspects of wave propagation and heating in an experimental situation. 2. How effective is plasma heating in the complex magnetic field configuration of the octupole. Experimental work is accomplished by launching 1-10ms pulses of up to 40kW of radio frequency power at 140MHz corresponding to the hot plasma lower hybrid resonance in the octupole. A diploe antenna which is moveable radially and is also rotatable couples wave power to the plasma. Coupling efficiencies greater than 95% are achieved by proper antenna placement near the edge of the plasma radial density profile.

Owens, T.L.

1979-08-01

56

Controlling magnetic field profiles  

International Nuclear Information System (INIS)

A method for designing solenoid magnets with controlled field profiles is discussed. The method, originated by D.B. Montgomery, minimizes both the field errors and the power consumption. An NOS time-sharing computer program for the CDC-6600, entitled MAGCOR, was constructed to provide an interactive magnet design capability. Results obtained during the design of magnets for a radial line electron accelerator are presented. 9 figures

57

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

58

Hall attractor in axially symmetric magnetic fields in neutron star crusts.  

Science.gov (United States)

We find an attractor for an axially symmetric magnetic field evolving under the Hall effect and subdominant Ohmic dissipation, resolving the question of the long-term fate of the magnetic field in neutron star crusts. The electron fluid is in isorotation, analogous to Ferraro's law, with its angular velocity being approximately proportional to the poloidal magnetic flux, ???. This equilibrium is the long-term configuration of a magnetic field evolving because of the Hall effect and Ohmic dissipation. For an initial dipole-dominated field, the attractor consists mainly of a dipole and an octupole component accompanied by an energetically negligible quadrupole toroidal field. The field dissipates in a self-similar way: Although higher multipoles should decay faster, the toroidal field mediates transfer of energy into them from the lower ones, leading to an advection diffusion equilibrium and keeping the ratio of the poloidal multipoles almost constant. This has implications for the structure of the intermediate-age neutron stars, suggesting that their poloidal field should consist of a dipole and an octupole component accompanied by a very weak toroidal quadrupole. For initial conditions that have a higher multipole ? structure, the attractor consists mainly of ? and ?+2 poloidal components. PMID:24836229

Gourgouliatos, Konstantinos N; Cumming, Andrew

2014-05-01

59

Hall Attractor in Axially Symmetric Magnetic Fields in Neutron Star Crusts  

Science.gov (United States)

We find an attractor for an axially symmetric magnetic field evolving under the Hall effect and subdominant Ohmic dissipation, resolving the question of the long-term fate of the magnetic field in neutron star crusts. The electron fluid is in isorotation, analogous to Ferraro's law, with its angular velocity being approximately proportional to the poloidal magnetic flux, ? ??. This equilibrium is the long-term configuration of a magnetic field evolving because of the Hall effect and Ohmic dissipation. For an initial dipole-dominated field, the attractor consists mainly of a dipole and an octupole component accompanied by an energetically negligible quadrupole toroidal field. The field dissipates in a self-similar way: Although higher multipoles should decay faster, the toroidal field mediates transfer of energy into them from the lower ones, leading to an advection diffusion equilibrium and keeping the ratio of the poloidal multipoles almost constant. This has implications for the structure of the intermediate-age neutron stars, suggesting that their poloidal field should consist of a dipole and an octupole component accompanied by a very weak toroidal quadrupole. For initial conditions that have a higher multipole ? structure, the attractor consists mainly of ? and ?+2 poloidal components.

Gourgouliatos, Konstantinos N.; Cumming, Andrew

2014-05-01

60

Detecting Exoplanetary Magnetic Fields  

Science.gov (United States)

Asymmetries in exoplanet transits are proving to be a useful tool for furthering our understanding of magnetic activity on both stars and planets outside our Solar System.Near-UV observations of the WASP-12 system have revealed asymmetries in the timing of the transit when compared with the optical light curve. A number of possible explanations have been suggested for this variation, including the presence of a magnetospheric bow shock arising from the interaction of the planet's magnetic field with the stellar wind from it's host star. Such observations provide the first method for directly detecting the presence of a magnetic field on exoplanets.The shape and size of such asymmetries is highly dependent on the structure of the host stars magnetic field at the time of observation. This implies we may observe highly varying near-UV transit light curves for the same system. These variations can then be used to learn about the geometry of the host star's magnetic field.In this presentation I will show modelling a bow shock around an exoplanet can help us to not only detect, but also also place constraints on the magnetic field strength of hot Jupiters. For some systems, such as HD 189733, we have maps of the surface magnetic field of the star at various epochs. I will also show how incorporating these maps into a stellar wind model, I can model the formation of a bow shock around the planet and hence demonstrate the variability of the near-UV transits.

Llama, Joe

2015-01-01

61

Octupole Deformed Nuclei in the Actinide Region  

CERN Multimedia

% IS322 \\\\ \\\\ The aim of the present study is to investigate the limits of the "island" 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 $\\beta\\gamma\\gamma$(t) method.

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

62

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

63

Magnetic Propeller for Uniform Magnetic Field Levitation  

OpenAIRE

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 fie...

Krinker, Mark; Bolonkin, Alexander

2008-01-01

64

ISR Radial Field Magnet  

CERN Multimedia

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

1983-01-01

65

Ground state octupole correlation energies with effective forces  

CERN Document Server

The ground state octupole correlations energies obtained with the D1M variant of the Gogny force are analyzed in detail. First we consider the correlation energy gained at the mean field level by allowing reflection symmetry breaking. Next we consider the energy gain coming from symmetry (parity) restoration and finally we analyze the ground state correlation energy after configuration mixing with axially symmetric octupole states. We find that these correlations do not significantly affect the trends of binding energies and systematics near closed shells. In particular, the too-large shell gaps predicted by self-consistent mean field models are not altered by the correlations.

Robledo, Luis M

2014-01-01

66

High field superconducting magnets  

Science.gov (United States)

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

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

2011-01-01

67

The magnetic field and abundance distribution geometry of the peculiar B star HD 215441  

International Nuclear Information System (INIS)

Nine high-resolution, high signal-to-noise spectra of the strongly magnetic Bp star HD 215441 = Babcock's star, well spaced through the rotation cycle, have been obtained. These data have been used to model the magnetic field geometry of the star and the distribution over one hemisphere of the elements Si, Ti, Cr, and Fe by means of a line synthesis program that includes the effects of the magnetic field and of nonuniform abundance distributions. The magnetic field axis appears to be inclined to the rotation axis at an angle of about 35 deg, and the rotation axis is inclined to the line of sight by about the same amount. The Zeeman splitting of spectral lines is reasonably well reproduced by an axisymmetric superposition of dipole, quadrupole, and octupole of polar strengths +67, -55, and +30 kG, respectively. 51 refs

68

The earth's magnetic field  

International Nuclear Information System (INIS)

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

69

Galactic magnetic fields and magnetic monopoles  

International Nuclear Information System (INIS)

This chapter proposes that the existence of the galactic field implies that the flux of magnetic monopoles is not in excess of 10-15 monopoles cm-2 s-1 unless the monopole mass is much larger than 1016 GeV or that the field of the galaxy is a manifestation of magnetic monopole plasma oscillations. Methods of avoiding excessive Landsu damping and phase mixing are given. Topics considered include the acceleration of magnetic monopoles and magnetic monopole plasma oscillations

70

Alignment effects and stable octupole deformation in the actinides  

International Nuclear Information System (INIS)

Explicit relations between the alignment of the intrinsic octupole momentum and a new type of deformation which does not conserve the axial symmetry are established. It seems that such an octupole deformation of the nuclear shape is indeed a general property of nuclear high spin states, whatever may become the axial octupole shape with increasing rotational frequency. However the nature seems to be reticent to show such properties easily and fortunately there exists shell-effects which allow to study them at low spin but only in some exceptional cases. One should push forwards both theory and experiments in this field. From the experimental point of view, one may expect much from the new multidetection techniques although one must overcome the experimental difficulties arising from the high rate of fission products in the (HI, xn) reactions

71

High magnetic fields in chemistry  

OpenAIRE

Recent applications of large (? 1 T ? 30 T) magnetic fields in modern chemical research are reviewed. Magnetic field effects of chemical relevance appear on the levels of quantum mechanics, thermodynamics, and macroscopic forces. Quantum mechanical magnetic field effects are governed by the Zeeman interaction and are borne out as static and dynamic effects in spectroscopy and in chemical kinetics. Magnetic circular dichroism (MCD) spectroscopy and magnetic fluorescence quenching in the ...

Steiner, Ulrich; Gilch, Peter

2003-01-01

72

Electrically silent magnetic fields.  

OpenAIRE

There has been a significant controversy over the past decade regarding the relative information content of bioelectric and biomagnetic signals. In this paper we present a new, theoretical example of an electrically-silent magnetic field, based on a bidomain model of a cylindrical strand of tissue generalized to include off-diagonal components in the conductivity tensors. The physical interpretation of the off-diagonal components is explained, and analytic expressions for the electrical poten...

Roth, B. J.; Wikswo, J. P.

1986-01-01

73

The non-dipolar magnetic fields of accreting T Tauri stars  

Science.gov (United States)

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 field is distorted close to the star by the stronger field regions, with the net effect being that the fractional open flux through the stellar surface is less than would be expected with a dipole magnetic field model. Finally, we estimate the disc truncation radius, assuming that this occurs where the magnetic torque from the stellar magnetosphere is comparable to the viscous torque in the disc.

Gregory, S. G.; Matt, S. P.; Donati, J.-F.; Jardine, M.

2008-10-01

74

Low field magnetic resonance imaging  

Science.gov (United States)

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

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

2010-07-13

75

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.

Wolfgang Christian

76

On octupole alignment in actinides  

Energy Technology Data Exchange (ETDEWEB)

The alignment of the octupole angular momentum in the rotational states of the K/sup ..pi../ = 0/sup -/ band is analysed in the microscopic model. The model describes qualitatively the branching ratio for the E1-transitions from these states to the ground band states.

Nazmitdinov, R.G.; Mikhailov, I.N.; Briancon, C.

1987-04-09

77

On octupole alignment in actinides  

International Nuclear Information System (INIS)

The alignment of the octupole angular momentum in the rotational states of the K? = 0- band is analysed in the microscopic model. The model describes qualitatively the branching ratio for the E1-transitions from these states to the ground band states. (orig.)

78

Octupole correlations in superdeformed nuclei  

International Nuclear Information System (INIS)

Octupole correlations have been investigated within the Generator Coordinate Method based upon Hartree-Fock plus BCS wavefunctions. GCM states corresponding to the q30 and q32 modes have been built up to describe the SD excited bands which have been recently observed as negative parity bands. (authors)

79

AGS correction quadrupoles and octupoles  

International Nuclear Information System (INIS)

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.)

80

Influence of the octupole mode on nuclear high-K isomeric properties  

Science.gov (United States)

The influence of quadrupole-octupole deformations on the energy and magnetic properties of high-K isomeric states in even-even actinide (U, Pu, Cm, Fm, No), rare-earth (Nd, Sm and Gd), and superheavy (^{270}\\text{Ds}) nuclei is examined within a deformed shell model with pairing interaction. The neutron two-quasiparticle (2qp) isomeric energies and magnetic dipole moments are calculated over a wide range in the plane of quadrupole and octupole deformations. In most cases the magnetic moments exhibit a pronounced sensitivity to the octupole deformation. At the same time, the calculations outline three different groups of nuclei: with pronounced, shallow, and missing minima in the 2qp energy surfaces with respect to the octupole deformation. The result indicates regions of nuclei with octupole softness as well as with possible octupole deformation in the high-K isomeric states. These findings show the need for further theoretical analysis as well as of detailed experimental measurements of magnetic moments in heavy deformed nuclei.

Minkov, Nikolay; Walker, Phil

2014-05-01

81

Magnetic nanoparticle traveling in external magnetic field  

OpenAIRE

A set of equations describing the motion of a free magnetic nanoparticle in an external magnetic field in a vacuum, or in a medium with negligibly small friction forces is postulated. The conservation of the total particle momentum, i.e. the sum of the mechanical and the total spin momentum of the nanoparticle is taken into account explicitly. It is shown that for the motion of a nanoparticle in uniform magnetic field there are three different modes of precession of the unit...

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

2014-01-01

82

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.

83

Magnetic response to applied electrostatic field in external magnetic field  

OpenAIRE

We show, within QED and other possible nonlinear theories, that a static charge localized in a finite domain of space becomes a magnetic dipole, if it is placed in an external (constant and homogeneous) magnetic field in the vacuum. The magnetic moment is quadratic in the charge, depends on its size and is parallel to the external field, provided the charge distribution is at least cylindrically symmetric. This magneto-electric effect is a nonlinear response of the magnetized vacuum to an app...

Adorno, T. C. Instituto Fi?sica; Gitman, D. M.; Shabad, A. E.

2013-01-01

84

SOLAR MAGNETIC ACTIVITY CYCLES, CORONAL POTENTIAL FIELD MODELS AND ERUPTION RATES  

International Nuclear Information System (INIS)

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 National Solar Observatory's three magnetographs at Kitt Peak, the Synoptic Optical Long-term Investigations of the Sun vector spectro-magnetograph, the spectro-magnetograph and the 512-channel magnetograph instruments, and from Stanford University'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 and 2006 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 activity cycle. All non-axisymmetric multipole strengths are well correlated with the activity cycle. The tilt of the solar dipole is therefore almost entirely due to active-region fields. The axial dipole and octupole are the largest contributors to the global field except while the polar fields are reversing. This influence of the polar fields extends to modulating eruption rates. According to the Computer Aided CME Tracking, Solar Eruptive Eputer Aided CME Tracking, Solar Eruptive Event Detection System, and Nobeyama radioheliograph prominence eruption catalogs, the rate of solar eruptions is found to be systematically higher for active years between 2003 and 2012 than for those between 1997 and 2002. This behavior appears to be connected with the weakness of the late-cycle 23 polar fields as suggested by Luhmann. We see evidence that the process of cycle 24 field reversal is well advanced at both poles.

85

SOLAR MAGNETIC ACTIVITY CYCLES, CORONAL POTENTIAL FIELD MODELS AND ERUPTION RATES  

Energy Technology Data Exchange (ETDEWEB)

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 National Solar Observatory's three magnetographs at Kitt Peak, the Synoptic Optical Long-term Investigations of the Sun vector spectro-magnetograph, the spectro-magnetograph and the 512-channel magnetograph instruments, and from Stanford University'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 and 2006 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 activity cycle. All non-axisymmetric multipole strengths are well correlated with the activity cycle. The tilt of the solar dipole is therefore almost entirely due to active-region fields. The axial dipole and octupole are the largest contributors to the global field except while the polar fields are reversing. This influence of the polar fields extends to modulating eruption rates. According to the Computer Aided CME Tracking, Solar Eruptive Event Detection System, and Nobeyama radioheliograph prominence eruption catalogs, the rate of solar eruptions is found to be systematically higher for active years between 2003 and 2012 than for those between 1997 and 2002. This behavior appears to be connected with the weakness of the late-cycle 23 polar fields as suggested by Luhmann. We see evidence that the process of cycle 24 field reversal is well advanced at both poles.

Petrie, G. J. D. [National Solar Observatory, Tucson, AZ 85719 (United States)

2013-05-10

86

Magnetic field therapy: a review.  

Science.gov (United States)

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

Markov, Marko S

2007-01-01

87

Polar Magnetic Field Experiment  

Science.gov (United States)

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

Russell, C. T.

1999-01-01

88

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

89

Magnetic Propeller for Uniform Magnetic Field Levitation  

CERN Document Server

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

90

Evolution of twisted magnetic fields  

International Nuclear Information System (INIS)

The magnetic field of the solar corona evolves quasistatically in response to slowly changing photospheric boundary conditions. The magnetic topology is preserved by the low resistivity of the solar atmosphere. We show that a magnetic flux coordinate system simplifies the problem of calculating field evolution with invariant topology. As an example, we calculate the equilibrium of a thin magnetic flux tube with small twist per unit length

91

Magnetic Fields on Cool Stars  

OpenAIRE

Magnetic fields are an important ingredient to cool star physics, and there is great interest in measuring fields and their geometry in order to understand stellar dynamos and their influence on star formation and stellar evolution. During the last few years, a large number of magnetic field measurements became available. Two main approaches are being followed to measure the Zeeman effect in cool stars; 1) the measurement of polarized light, for example to produce magnetic m...

Reiners, Ansgar

2010-01-01

92

Magnetic response to applied electrostatic field in external magnetic field  

Energy Technology Data Exchange (ETDEWEB)

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

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

2014-04-15

93

Magnetic response to applied electrostatic field in external magnetic field  

International Nuclear Information System (INIS)

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

94

Theory of fossil magnetic field  

Science.gov (United States)

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

Dudorov, Alexander E.; Khaibrakhmanov, Sergey A.

2015-02-01

95

Theory of fossil magnetic field  

OpenAIRE

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

Dudorov, Alexander E.; Khaibrakhmanov, Sergey A.

2014-01-01

96

Origin of cosmic magnetic fields  

CERN Document Server

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 \\times 10^(-12) G if the energy scale of inflation is few \\times 10^(16) GeV. Such a field account for galactic and galaxy cluster magnetic fields.

Campanelli, Leonardo

2013-01-01

97

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(-12)??G if the energy scale of inflation is few×10(16)??GeV. Such a field accounts for galactic and galaxy cluster magnetic fields. PMID:23971556

Campanelli, Leonardo

2013-08-01

98

Measurements of magnetic field alignment  

International Nuclear Information System (INIS)

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

99

Octupole correlations in the heavy elements  

International Nuclear Information System (INIS)

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 26-pole deformation and fast El transitions to an octupole model is considered. 30 refs., 21 figs., 1 tab

100

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

101

Rotating superconductor magnet for producing rotating lobed magnetic field lines  

International Nuclear Information System (INIS)

A rotating superconductor magnet is described for producing a rotating lobed magnetic field, comprising a cryostat; a superconducting magnet in the cryostat having a collar for producing a lobed magnetic field having oppositely directed adjacent field lines; rotatable support means for selectively rotating the superconductor magnet; and means for energizing the superconductor magnet

102

Design for the magnetic field requirements of the tandem mirror experiment  

International Nuclear Information System (INIS)

The tandem mirror magnetic geometry is described, followed by an analysis of the magnet set designed to meet the requirements of the TMX experiment. The final magnet line-up is composed of a baseball coil with two C coils for each plug, six solenoidal coils for the central cell, and two RC coils plus one octupole coil for each transition

103

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

CERN Document Server

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, where 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...

Robledo, L M; Schuck, P; Viñas, X

2010-01-01

104

Venus magnetic field and magnetosphere  

International Nuclear Information System (INIS)

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

105

Preprocessing Magnetic Fields with Chromospheric Longitudinal Fields  

Science.gov (United States)

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

Yamamoto, Tetsuya T.; Kusano, K.

2012-06-01

106

Magnetic fields and scintillator performance  

International Nuclear Information System (INIS)

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

107

Streamer propagation in magnetic field  

CERN Document Server

The propagation of a streamer near an insulating surface under the influence of a transverse magnetic field is theoretically investigated. In the weak magnetic field limit it is shown that the trajectory of the streamer has a circular form with a radius that is much larger than the cyclotron radius of an electron. The charge distribution within the streamer head is strongly polarized by the Lorentz force exerted perpendicualr to the streamer velocity. A critical magnetic field for the branching of a streamer is estimated. Our results are in good agreement with available experimental data.

Zhuravlev, V N; Vagner, I D; Wyder, P

1997-01-01

108

Preface: Cosmic magnetic fields  

Science.gov (United States)

Recent advances in observations and modeling have opened new perspectives for the understanding of fundamental dynamical processes of cosmic magnetism, and associated magnetic activity on the Sun, stars and galaxies. The goal of the Special Issue is to discuss the progress in solar physics and astrophysics, similarities and differences in phenomenology and physics of magnetic phenomena on the Sun and other stars. Space observatories, ground-based telescopes, and new observational methods have provided tremendous amount of data that need to be analyzed and understood. The solar observations discovered multi-scale organization of solar activity, dramatically changing current paradigms of solar variability. On the other side, stellar observations discovered new regimes of dynamics and magnetism that are different from the corresponding solar phenomena, but described by the same physics. Stars represent an astrophysical laboratory for studying the dynamical, magnetic and radiation processes across a broad range of stellar masses and ages. These studies allow us to look at the origin and evolution of our Sun, whereas detailed investigations of the solar magnetism give us a fundamental basis for interpretation and understanding of unresolved stellar data.

Kosovichev, Alexander

2015-02-01

109

ISR split-field magnet  

CERN Multimedia

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

1975-01-01

110

Measuring Earth's Magnetic Field Simply.  

Science.gov (United States)

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

Stewart, Gay B.

2000-01-01

111

Design of transport lines for uniforming beam distribution with octupoles  

Science.gov (United States)

The intensity distribution of a typical particle beam is an approximate Gaussian distribution while many applications require the beam to be uniform. Local bright spots on the targets for high-power Gaussian beams create difficult cooling problems and shorten the lifetime of the target. In this paper, we have theoretically studied uniformization of the transverse beam profile using two octupole magnets placed at particular locations in the beam transport line. The details about the requirements on magnet strength and phase advance will be shown. As an example, we take a set of China Spallation Neutron Source parameters to simulate the beam. The simulation result agrees well with theoretical formulas.

Guo, Y. Y.; Xu, G.

2013-02-01

112

High-Field Accelerator Magnets  

CERN Document Server

In this lecture an overview is given of the present technology for high field accelerator magnets. We indicate how to get high fields and what are the most important parameters. The available conductors and their limitations are presented followed by the most relevant types of coils and support structures. We conclude by showing a number of recent examples of development magnets which are either pure R&D objects or models for the LHC luminosity upgrade.

de Rijk, G

2014-01-01

113

Magnetic resonance in an elliptic magnetic field  

CERN Document Server

The behaviour of a particle with a spin 1/2 and a dipole magnetic moment in a time-varying magnetic field in the form $(h_0 cn(\\omega t,k), \\\\h_0 sn(\\omega t,k), H_0 dn(\\omega t,k))$, where $\\omega$ is the driving field frequency, $t$ is the time, $h_0$ and $H_0$ are the field amplitudes, $cn$, $sn$, $dn$ are Jacobi elliptic functions, $ k$ is the modulus of the elliptic functions has been considered. The variation parameter $k$ from zero to 1 gives rise to a wide set of functions from trigonometric shapes to exponential pulse shapes modulating the field. The problem was reduced to the solution of general Heun' equation. The exact solution of the wave function was found at resonance for any $ k$. It has been shown that the transition probability in this case does not depend on $k$. The present study may be useful for analysis interference experiments, improving magnetic spectrometers and the field of quantum computing.

Ivanchenko, E A

2004-01-01

114

Transmission cable magnetic field research  

International Nuclear Information System (INIS)

Generally accepted methods for calculating magnetic fields in the vicinity of overhead transmission lines are currently available. These calculation procedures have received general acceptance because they are well documented and because field measurement data is available to support the calculation results. Similar data and calculation procedures, however, are lacking for underground transmission cables. This is particularly true for pipe-type transmission cables which comprise the vast majority of transmission cables in this country. The high magnetic permeability of the steel pipe which surrounds the cables provides effective attenuation of the magnetic field external to the pipe, but the amount of attenuation is difficult to predict. This is primarily due to the nonlinear permeability of the carbon steel pipe and eddy current effects. This research project consisted of conducting magnetic field measurements in the vicinity of a pipe-cable system under controlled conditions at the EPRI Waltz Mill Test Facility to determine typical magnetic field values and how these values vary with operating conditions. This report describes the measurement results as well as an analysis of the factors which primarily affect the magnetic field external to the cable pipe

115

Octupole vibrations at high angular momenta  

CERN Document Server

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 vibrations. 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.

Nakatsukasa, T

1995-01-01

116

Nonlocal Pseudopotentials and Magnetic Fields  

Science.gov (United States)

We show how to describe the coupling of electrons to nonuniform magnetic fields in the framework of the widely used norm-conserving pseudopotential approximation 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 within density functional theory (DFT) in the local density approximation. Our results are compared with high-quality all-electron DFT results obtained using Gaussian basis sets and another recently proposed pseudopotential formalism.

Pickard, Chris J.; Mauri, Francesco

2003-11-01

117

Neptune's magnetic field - Calculation of field geometric invariants derived from the I8E1 GSFC/BRI model  

Science.gov (United States)

L shell values along the Voyager 2 encounter trajectory and those associated with the N1 through N6 moons and N1R through N6R rings of Neptune are computed numerically on the basis of a simplified description of the Neptunian magnetic field derived from the Goddard Space Flight Center/Bartol Research Institute I8E1 model, which includes internal terms up to and including the octupole (but no external terms). Like Uranus, the large tilt between the dipole term and the rotation axis causes the moons and rings to sweep a very large range of L shells. Their orbital motion introduces additional periodicities, causing the maxima and minima in L space to vary systematically with time.

Acuna, M. H.; Connerney, J. E. P.; Ness, N. F.

1993-01-01

118

Magnetic Field Generation in Stars  

Science.gov (United States)

Enormous progress has been made on observing stellar magnetism in stars from the main sequence (particularly thanks to the MiMeS, MAGORI and BOB surveys) through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence, in the generation and stability of neutron star fields. Independent information on the internal magnetic field of neutron stars will come from future gravitational wave detections. Coherent searches for the Crab pulsar with the Laser Interferometer Gravitational Wave Observatory (LIGO) have already constrained its gravitational wave luminosity to be ?2 % of the observed spin-down luminosity, thus placing a limit of ?1016 G on the internal field. Indirect spin-down limits inferred from recycled pulsars also yield interesting gravitational-wave-related constraints. Thus we may be at the dawn of a new era of exciting discoveries in compact star magnetism driven by the opening of a new, non-electromagnetic observational window. We also review recent advances in the theory and computation of magnetohydrodynamic turbulence as it applies to stellar magnetism and dynamo theory. These advances offer insight into the action of stellar dynamos as well as processes which control the diffusive magnetic flux transport in stars.

Ferrario, Lilia; Melatos, Andrew; Zrake, Jonathan

2015-03-01

119

Magnetic Field System of PERC  

International Nuclear Information System (INIS)

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

120

Modeling Earth's magnetic field variation  

Science.gov (United States)

Observations of the Earth's magnetic field taken at the Earth's surface and at satellite altitude have been combined to construct models of the geomagnetic field and its variation. Lesur et al. (2010) developed a kinematic reconstruction of core field changes that satisfied the frozen-flux constraint. By constraining the field evolution to be entirely due to advection of the magnetic field at the core surface it maintained the spatial complexity of the field morphology imposed by a satellite field model backward in time [Wardinski & Lesur,2012]. In this study we attempt a kinematic construction of future variation in Earth's magnetic field variation. Our approach, first seeks to identify typical time scales of the magnetic field and core surface flows present in decadal and millennial field and flow models. Therefore, the individual spherical harmonic coefficients are treated by methods of time series analysis. The second step employs stochastic modelling of the temporal variability of such spherical harmonic coefficients that represent the field and core surface flow. Difficulties arise due to the non-stationary behavior of the field and core surface flow. However, the broad behavior may consist of some homogeneity, which could be captured by a generalized stochastic model that calls for the d'th difference of the time series to be stationary (ARIMA-Model), or by detrending the coefficient time series. By computing stochastic models, we obtain two sets of field-forecasts, the first set is obtained from stochastic models of the Gauss coefficients. Here, first results suggest that secular variation on time scales shorter than 5 years behaves rather randomly and cannot be described sufficiently well by stochastic models. The second set is derived from forward modeling the secular variation using the diffusion-less induction equation (kinematic construction). This approach has not provide consistent results.

Wardinski, I.

2012-12-01

121

Satellite to study earth's magnetic field  

Science.gov (United States)

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

1979-01-01

122

Isotope separation by magnetic fields  

International Nuclear Information System (INIS)

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

123

Deflections in magnet fringe fields  

International Nuclear Information System (INIS)

A transverse multipole expansion is derived, including the longitudinal components necessarily present in regions of varying magnetic field profile. It can be used for exact numerical orbit following through the fringe-field regions of magnets whose end designs introduce no extraneous components, i.e., fields not required to be present by Maxwell's equations. Analytic evaluations of the deflections are obtained in various approximations. Mainly emphasized is a 'straight-line approximation', in which particle orbits are treated as straight lines through the fringe-field regions. This approximation leads to a readily-evaluated figure of merit, the ratio of rms end deflection to nominal body deflection, that can be used to determine whether or not a fringe field can be neglected. Deflections in 'critical' cases (e.g., near intersection regions) are analyzed in the same approximation

124

Crystalline Electric Field Effects and Hidden Order in URu2Si2  

Science.gov (United States)

We show that an antiferro-octupole order of Eu(x(y2-z2), y(z2-x2)) symmetry accounts for the rotational symmetry (RS) reduction of the basal plane magnetic susceptibility in the hidden order (HO) phase of URu2Si2. We determine the crystalline electric field level scheme with lower singlet-doublet levels, which can stabilize the Eu octupole order, as well as the quadrupole order of Eg(yz, zx) symmetry. Both orders can explain the RS reduction, but the octupole order breaks the time reversal symmetry, in agreement with the ligand NMR measurements, while the quadrupole order does not. Consequently, the Eu octupole order is favorable for the HO of URu2Si2.

Hanzawa, Katsurou

2012-11-01

125

Generation of helical magnetic fields from inflation  

CERN Document Server

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

126

Magnetic fields of neutron stars  

CERN Document Server

Neutron stars contain the strongest magnetic fields known in the Universe. In this paper, I discuss briefly how these magnetic fields are inferred from observations, as well as the evidence for their time-evolution. I show how these extremely strong fields are actually weak in terms of their effects on the stellar structure, as is also the case for magnetic stars on the upper main sequence and magnetic white dwarfs, which have similar total magnetic fluxes. I propose a scenario in which a stable hydromagnetic equilibrium (containing a poloidal and a toroidal field component) is established soon after the birth of the neutron star, aided by the strong compositional stratification of neutron star matter, and this state is slowly eroded by non-ideal magnetohydrodynamic processes such as beta decays and ambipolar diffusion in the core of the star and Hall drift and breaking of the solid in its crust. Over sufficiently long time scales, the fluid in the neutron star core will behave as if it were barotropic, becau...

Reisenegger, Andreas

2013-01-01

127

Magnetic field tomography, helical magnetic fields and Faraday depolarization  

Science.gov (United States)

Wide-band radio polarization observations offer the possibility to recover information about the magnetic fields in synchrotron sources, such as details of their three-dimensional configuration, that has previously been inaccessible. The key physical process involved is the Faraday rotation of the polarized emission in the source (and elsewhere along the wave's propagation path to the observer). In order to proceed, reliable methods are required for inverting the signals observed in wavelength space into useful data in Faraday space, with robust estimates of their uncertainty. In this paper, we examine how variations of the intrinsic angle of polarized emission ?0 with the Faraday depth ? within a source affect the observable quantities. Using simple models for the Faraday dispersion F(?) and ?0(?), along with the current and planned properties of the main radio interferometers, we demonstrate how degeneracies among the parameters describing the magneto-ionic medium can be minimized by combining observations in different wavebands. We also discuss how depolarization by Faraday dispersion due to a random component of the magnetic field attenuates the variations in the spectral energy distribution of the polarization and shifts its peak towards shorter wavelengths. This additional effect reduces the prospect of recovering the characteristics of the magnetic field helicity in magneto-ionic media dominated by the turbulent component of the magnetic field.

Horellou, C.; Fletcher, A.

2014-07-01

128

Magnetic Fields of the Earth and Sun  

Science.gov (United States)

This is an activity that compares the magnetic field of the Earth to the complex magnetic field of the Sun. Using images of the Earth and Sun that have magnets attached in appropriate orientations, learners will use a handheld magnetic field detector to observe the magnetic field of the Earth and compare it to that of the Sun, especially in sunspot areas. For each group of students, this activity requires use of a handheld magnetic field detector, such as a Magnaprobe or a similar device, a bar magnet, and ten small disc magnets.

129

Magnetic Forces and Field Line Density  

Science.gov (United States)

This is an activity about depicting the relative strength of magnetic fields using field line density. Learners will use the magnetic field line drawing of six magnetic poles created in a previous activity and identify the areas of strong, weak, and medium magnetic intensity using the density of magnetic field lines. This is the fifth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website. How to Draw Magnetic Fields - II in the Magnetic Math booklet must be completed prior to this activity.

2012-08-03

130

Reconnection of magnetic field lines  

International Nuclear Information System (INIS)

Magnetic field line diffusion in a plasma is studied on the basis of the non-linear boundary layer equations of dissipative, incompressible magnetohydrodynamics. Non-linear steady state solutions for a class of plasma parameters have been obtained which are consistent with the boundary conditions appropriate for reconnection. The solutions are self-consistent in connecting a stagnation point flow of a plasma with reconnecting magnetic field lines. The range of the validity of the solutions, their relation to other fluid models of reconnection, and their possible applications to space plasma configurations are pointed out. (Author)

131

Observations of Interstellar Magnetic Fields  

Science.gov (United States)

This article describes how interstellar magnetic fields are detected, measured, and mapped, the results of such observations, and the role played by interstellar magnetic fields in the physics of the interstellar medium. A goal of the observations is the measurement of the morphology and strengths of the uniform (Bu) and random (Br) components of magnetic fields. Observational techniques probe either the component of B parallel to the line of sight (B_parallel) or in the plane of the sky (B_?). Tracers of B_parallel are Faraday rotation of the position angle of linearly polarized radiation and Zeeman splitting of spectral lines. Tracers of B_? are the strength of synchrotron radiation and linear polarization of syn chrotron radiation and of emission or absorption from dust and spectral lines. Starlight polarization shows that on large spatial scales the Galactic magnetic field is not heavily tangled (B_u/B_r ? 0.7 - 1.0), that the field is generally parallel to the Galactic plane near the plane, that the local field points approximately along the local spiral arm (pitch angle 9.4(°) , center of curvature 7.8 kpc distant towards ? ? -15.4(°) ), and that off the Galactic plane there is considerable small-scale structure to the field. Galactic synchrotron emission shows magnetic spiral arms with a total strength B_t ? 6 #55G and B_u ? 4 #55G. Pulsar data show evidence for reversals of the field direction with Galactic radius and yield B_r ? 5 #55G and B_u ? 1.5 #55G; the morphology of the large-scale mean field is consistent with dynamo generation. H I Zeeman detections for diffuse clouds yield B_parallel char 126 5 - 20 #55G with many limits B_parallel #55G. A recent survey of Galactic H I in absorption against extragalactic sources confirms the result that the fields in diffuse clouds are often quite weak. The critical parameter for evaluating the importance of magnetic fields in star formation is the ratio of the mass to the magnetic flux, M/Phi_B; observations focus on measuring both this quantity and the morphology of fields in dense regions. Zeeman observations of molecular lines are consistent with B propto sigma_v sqrt{n}, which is the theoretical prediction for flattened cores supported by a combination of a uniform magnetic field pressure and turbulence. In cores, motions are approximately Alfvénic, and M/Phi_B$ has a critical to slightly supercritical value. The ratio of Br/Bu appears to decline with density. In some molecular cores there is evidence for the "hourglass" pinch that would be produced by cloud contraction with the magnetic field frozen into the matter.

Crutcher, R.; Heiles, C.; Troland, T.

132

Magnetic fields in neutron stars  

CERN Document Server

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

133

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

134

Galactic and extragalactic magnetic fields  

CERN Document Server

The current state of research of the Galactic magnetic field is reviewed critically. The average (equipartition) strength of the total field derived from radio synchrotron data is 6 +/- 2 muG locally and about 10 +/- 3 muG at 3 kpc Galactic radius. These values agree well with the estimates using the locally measured cosmic-ray energy spectrum and the radial variation of protons derived from gamma-rays. Optical and synchrotron polarization data yield a strength of the local regular field of 4 +/- 1 muG, but this value is an upper limit if the field strength fluctuates within the beam or if anisotropic fields are present. Pulsar rotation measures, on the other hand, give only 1.4 +/- 0.2 muG, a lower limit if fluctuations in regular field strength and thermal electron density are anticorrelated along the pathlength. The local regular field may be part of a 'magnetic arm' between the optical arms. However, the global structure of the regular Galactic field is not yet known. Several large-scale field reversals i...

Beck, R

2000-01-01

135

Majorana neutrinos and magnetic fields  

International Nuclear Information System (INIS)

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

136

Magnetic pumping in spatially inhomogeneous magnetic fields  

International Nuclear Information System (INIS)

A method is described for fast radial toroidal plasma column acceleration in an average ion-ion collision time or less back and forth in the plane of the closed containment means of the ATC described in U. S. Pat. No. 3,702,163, irreversibly to heat the plasma column. In accordance with this invention, current is flowed through the toroidal and poloidal coil means of the ATC and these coils are distributed to provide an unbalanced biasing force on the toroidal, current carrying, plasma column by means of a shaped magnetic field having an unstable region between spaced apart stable regions. By modulating the shaped field the plasma column is pushed back and forth between the two stable regions. In another embodiment, the plasma current is modulated to the same end. (U.S.)

137

Oxide superconductors under magnetic field  

International Nuclear Information System (INIS)

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

138

A high-field superferric NMR magnet.  

Science.gov (United States)

Strong, extensive magnetic fringe fields are a significant problem with magnetic resonance imaging magnets. This is particularly acute with 4-T, whole-body research magnets. To date this problem has been addressed by restricting an extensive zone around the unshielded magnet or by placing external unsaturated iron shielding around the magnet. This paper describes a solution to this problem which uses superconducting coils closely integrated with fully saturated iron elements. A 4-T, 30-cm-bore prototype, based on this design principle, was built and tested. The 5 G fringe field is contained within 1 meter of the magnet bore along the z axis. Homogeneity of the raw magnetic field is 10 ppm over 30% of the magnet's diameter after passive shimming. Compared with an unshielded magnet, 20% less superconductor is required to generate the magnetic field. Images and spectra are presented to demonstrate the magnet's viability for magnetic resonance imaging and spectroscopy. PMID:8419740

Huson, F R; Bryan, R N; MacKay, W W; Herrick, R C; Colvin, J; Ford, J J; Pissanetzky, S; Plishker, G A; Rocha, R; Schmidt, W

1993-01-01

139

Nuclear magnetic octupole moment and the hyperfine structure of the $5D_{3/2,5/2}$ states of the Ba$^+$ ion  

OpenAIRE

The hyperfine structure of the long-lived $5D_{3/2}$ and $5D_{5/2}$ levels of Ba$^+$ ion is analyzed. A procedure for extracting relatively unexplored nuclear magnetic moments $\\Omega$ is presented. The relevant electronic matrix elements are computed in the framework of the ab initio relativistic many-body perturbation theory. Both the first- and the second-order (in the hyperfine interaction) corrections to the energy levels are analyzed. It is shown that a simultaneous me...

Beloy, K.; Derevianko, A.; Dzuba, V. A.; Howell, G. T.; Blinov, B. B.; Fortson, E. N.

2008-01-01

140

Instability of ferrofluid magnetic drops under magnetic field  

OpenAIRE

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

Bacri, J. C.; Salin, D.

1982-01-01

141

Magnetic fields in spiral galaxies  

Science.gov (United States)

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

Krause, Marita

2015-03-01

142

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

143

Advances in high field magnetism at Osaka  

Science.gov (United States)

Recent advances in high field magnetism mainly done in the High Magnetic Field Laboratory, Osaka University, are reviewed. Various magnetic and electronic properties are induced in high fields; it is emphasized that the newly developed incommensurate mean field model is effective in understanding complex phase diagrams such as in CeSb, CeBi and PrCo 2Si 2.

Date, M.

1989-03-01

144

Hypernuclear matter in strong magnetic field  

OpenAIRE

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 ...

Sinha, Monika; Mukhopadhyay, Banibrata; Sedrakian, Armen

2012-01-01

145

Magnetic field tomography, helical magnetic fields and Faraday depolarization  

OpenAIRE

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

Horellou, Cathy; Fletcher, Andrew

2014-01-01

146

Magnetic fields and halos in spiral galaxies  

CERN Document Server

Radio continuum observations allow to reveal the magnetic field structure in the disk and halo of nearby spiral galaxies, their magnetic field strength and vertical scale heights. The spiral galaxies studied so far show a similar magnetic field pattern which is of spiral shape along the disk plane and X-shaped in the halo, sometimes accompanied by strong vertical fields above and below the central region of the disk. The strength of the halo field is comparable to that of the disk. The total and turbulent magnetic field strength is (weakly) increasing with the star formation. There are, however, indications that stronger star formation reduces the magnetic field regularity globally. The magnetic field in spiral galaxies is generally thought to be amplified and maintained by dynamo action. During the galaxy's formation and evolution the turbulent dynamo amplifies the field strength to energy equipartition with the turbulent gas, while the large-scale (mean-field) dynamo mainly orders the magnetic field. Hence,...

Krause, Marita

2014-01-01

147

Constraining the central magnetic field of magnetars  

CERN Document Server

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

148

Weak magnetic fields injurious to health, strong magnetic fields harmless? Radiation protection by the present of magnetic fields  

International Nuclear Information System (INIS)

Usually magnetic fields are part of the environment without making injuries to health. Only when limits in standards were fixed the certainty become conscious that electromagnetic fields in their various forms must be hazardous. The effects of the pure magnetic fields cannot be found out easy because it is difficult to screen the magnetic fields, especially the magnetic field of the earth. This analyzis shall also find out how to hold limits by using extremely high magnetic fields in medicine and research. The results show that screening is no the only method when the practice requires behaviour where screening is not possible. (author)

149

Nuclear magnetic octupole moment and the hyperfine structure of the $5D_{3/2,5/2}$ states of the Ba$^+$ ion  

CERN Document Server

The hyperfine structure of the long-lived $5D_{3/2}$ and $5D_{5/2}$ levels of Ba$^+$ ion is analyzed. A procedure for extracting relatively unexplored nuclear magnetic moments $\\Omega$ is presented. The relevant electronic matrix elements are computed in the framework of the ab initio relativistic many-body perturbation theory. Both the first- and the second-order (in the hyperfine interaction) corrections to the energy levels are analyzed. It is shown that a simultaneous measurement of the hyperfine structure of the entire $5D_J$ fine-structure manifold allows one to extract $\\Omega$ without contamination from the second-order corrections. Measurements to the required accuracy should be possible with a single trapped barium ion using sensitive techniques already demonstrated in Ba$^+$ experiments.

Beloy, K; Dzuba, V A; Howell, G T; Blinov, B B; Fortson, E N

2008-01-01

150

Field errors in superconducting magnets  

International Nuclear Information System (INIS)

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

151

Passive Magnetic Shielding in Gradient Fields  

CERN Document Server

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

Bidinosti, C P

2013-01-01

152

Statistics of Magnetic Fields for OB Stars  

CERN Document Server

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

153

Anisotropic magnetism in field-structured composites  

International Nuclear Information System (INIS)

Magnetic field-structured composites (FSCs) are made by structuring magnetic particle suspensions in uniaxial or biaxial (e.g., rotating) magnetic fields, while polymerizing the suspending resin. A uniaxial field produces chainlike particle structures, and a biaxial field produces sheetlike particle structures. In either case, these anisotropic structures affect the measured magnetic hysteresis loops, with the magnetic remanence and susceptibility increased significantly along the axis of the structuring field, and decreased slightly orthogonal to the structuring field, relative to the unstructured particle composite. The coercivity is essentially unaffected by structuring. We present data for FSCs of magnetically soft particles, and demonstrate that the altered magnetism can be accounted for by considering the large local fields that occur in FSCs. FSCs of magnetically hard particles show unexpectedly large anisotropies in the remanence, and this is due to the local field effects in combination with the large crystalline anisotropy of this material. (c) 2000 The American Physical Society

154

Screening and finite size corrections to the octupole and Schiff moments  

CERN Document Server

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

155

Magnetic Behaviour of Disordered Ising Ferrimagnet in High Magnetic Field  

OpenAIRE

The magnetic behaviour of a disordered ferrimagnetic system Ap B1-p where both A and B represent the magnetic atoms with respective spin SA = 1/2 and SB = 1 in presence of high magnetic field is treated theoretically.Assuming the magnetic interaction can be described through Ising Hamiltonian the approximate free energy is obtained using the cluster-variational method. The field dependence of the magnetization is then obtained for different concentration p and exchange param...

Ghatak, Sobhendu K.

2011-01-01

156

Sliding Phases via Magnetic Fields  

CERN Document Server

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

Sondhi, S L; Yang, Kun

2001-01-01

157

Octupole signatures in 124,125Ba  

International Nuclear Information System (INIS)

The ? decay of the nuclei 124,125Ba has been investigated with the EUROBALL array, using the reaction 64Ni+64Ni at Ebeam = 255 and 261 MeV. Six new E1 transitions have been found in the nucleus 125Ba, suggesting a significant role of octupole correlations in the origin of its parity doublets. The J? = 3- level of the nucleus 124Ba has been identified for the first time. Its excitation energy is in very good agreement with a prediction based on a microscopic model including octupole interactions

158

Sun and the interplanetary magnetic field  

International Nuclear Information System (INIS)

Modern ideas of the interplanetary magnetic field and the influence of the Sun field on it are stated in the popular form. It was considered earlier, that magnetic fields in interplanetary space as in solar atmosphere were concentrated in numerous separate tubes. Now it become clear, that interplanetary space is filled with magnetic field of one plarity in the north hemisphere and of another - in the south. This field serves as an original continuation of the dipole field of the Sun

159

Spline techniques for magnetic fields  

International Nuclear Information System (INIS)

This report is an overview of B-spline techniques, oriented toward magnetic field computation. These techniques form a powerful mathematical approximating method for many physics and engineering calculations. In section 1, the concept of a polynomial spline is introduced. Section 2 shows how a particular spline with well chosen properties, the B-spline, can be used to build any spline. In section 3, the description of how to solve a simple spline approximation problem is completed, and some practical examples of using splines are shown. All these sections deal exclusively in scalar functions of one variable for simplicity. Section 4 is partly digression. Techniques that are not B-spline techniques, but are closely related, are covered. These methods are not needed for what follows, until the last section on errors. Sections 5, 6, and 7 form a second group which work toward the final goal of using B-splines to approximate a magnetic field. Section 5 demonstrates how to approximate a scalar function of many variables. The necessary mathematics is completed in section 6, where the problems of approximating a vector function in general, and a magnetic field in particular, are examined. Finally some algorithms and data organization are shown in section 7. Section 8 deals with error analysis

160

Origin of magnetic fields and superdense cosmogony  

Energy Technology Data Exchange (ETDEWEB)

This note demonstrates that a previous suggestion that galaxies result from the decay of superheavy hadrons with Regge spin provides a natural source for magnetic fields of galactic scale. It is shown that the configuration and strength of galactic magnetic fields can be explained by assuming that the currently observed magnetic fields are relics of the dipole magnetic field of superhadronic protogalaxies. In the framework of this theory, these protogalaxies decayed into fragments that evolved into the galaxies observed today.

Muradian, R.M.

1979-01-01

161

Origin of magnetic fields and superdense cosmogony  

International Nuclear Information System (INIS)

The origin of magnetic fields of galaxies is discussed. The problem is considered in the framework of the superdense hadron cosmogony. According to this theory superdense protogalactic matter is a superhadron. The decay of this superhadron leads to the galactic formation. It explains properly magnetic fields of galactic scale. The hypothesis is proposed that galactic magnetic fields are the remnants of the dipole magnetic fields of the protogalaxy

162

Magnetic Field of Relativistic Nonlinear Plasma Wave  

OpenAIRE

Longitudinal and transverse behavior of magnetic field of relativistic nonlinear three-dimensional plasma wave is investigated. It is shown that the magnetic field of the wave is different from zero and performs higher frequency oscillations compared to the plasma electron frequency. An increase in the nonlinearity leads to strengthening of magnetic field. The oscillations of magnetic field in transverse direction arise, that caused by the phase front curving of nonlinear pl...

Khachatryan, A. G.

2000-01-01

163

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

164

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

165

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.

166

Superconducting vibrator with a trapped magnetic field  

International Nuclear Information System (INIS)

Paper offers a design of a superconducting vibrator for flexural oscillations. Dependence of the vibrator proper frequency on the magnetic field is estimated. The proper frequency of the proposed design is shown to be tens times more sensitive to the magnetic field in contrast to all those used earlier. It is proposed to use such a resonator to study magnetic field penetration into superconductors

167

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.)

168

Microwave Measurements of Coronal Magnetic Field  

Science.gov (United States)

Magnetic field measurements of the solar corona using microwave observation are reviewed. The solar corona is filled with highly ionised plasma and magnetic field. Moving charged particles interact with magnetic field due to Lorentz force. This results in gyration motion perpendicular to the magnetic field and free motion along the magnetic field. Circularly polarized electro-magnetic waves interact with gyrating electrons efficiently and the interaction depends on the sense of circular polarization (right-handed or left-handed). This is the reason why we can measure magnetic field strength through microwave observations. This process does not require complicated quantum physics but the classical treatment is enough. Hence the inversion of measured values to magnetic field strength is simpler than in the case of optical and infrared measurements. There are several methods to measure magnetic field strength through microwave observations. We can divide them into two categories: one is based on emission mechanisms and the other is based on wave propagation. In the case of emission mechanisms, thermal f-f emission, thermal gyro-resonance emission and non-thermal gyro-synchrotron emission can be used to measure magnetic field strength. In the case of wave propagation, polarization reversal due to propagation through quasi-transverse magnetic field region can be used. Examples of distribution of magnetic field strength in the solar corona measured by Nobeyama Radioheliograph will be presented.

Shibasaki, K.

2006-08-01

169

Hypernuclear matter in strong magnetic field  

International Nuclear Information System (INIS)

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

170

The magnetic field measurements of the booster synchrotron magnet  

International Nuclear Information System (INIS)

The magnetic field properties of the booster synchrotron magnet are investigated. Method of the field measurement, magnetic field measuring system, its data acquisition system and procedure of data processing are described in detail, with a special emphasis on the accuracy in the measurement. The excitation dependences and distributions of the field strength, field gradient, multipole fields and their effective lengths are given and analyzed. The betatron tune and chromaticity are discussed by taking account of the effect of the fringing field as well as the multipole fields of focussing and defocussing sectors. (auth.)

171

Magnetic structure of DyAg in high magnetic fields  

International Nuclear Information System (INIS)

Neutron diffraction on metamagnetic DyAg, a cubic rare earth intermetallic compound, has been performed in pulsed high magnetic fields up to 13 T. We have observed prominent intensity decreases at critical fields. These magnetic phase transitions cannot be explained by any structural models proposed before according to the magnetization process. ((orig.))

172

Magnetic fields and halos in spiral galaxies  

OpenAIRE

Radio continuum observations allow to reveal the magnetic field structure in the disk and halo of nearby spiral galaxies, their magnetic field strength and vertical scale heights. The spiral galaxies studied so far show a similar magnetic field pattern which is of spiral shape along the disk plane and X-shaped in the halo, sometimes accompanied by strong vertical fields above and below the central region of the disk. The strength of the halo field is comparable to that of th...

Krause, Marita

2014-01-01

173

Octupole deformation in light actinides within an analytic quadrupole octupole axially symmetric model with Davidson potential  

CERN Document Server

The analytic quadrupole octupole axially symmetric model, which had successfully predicted 226Ra and 226Th as lying at the border between the regions of octupole deformation and octupole vibrations in the light actinides using an infinite well potential (AQOA-IW), is made applicable to a wider region of nuclei exhibiting octupole deformation, through the use of a Davidson potential (AQOA-D). Analytic expressions for energy spectra and B(E1), B(E2), B(E3) transition rates are derived. The spectra of 222-226Ra and 224,226Th are described in terms of the two parameters phi_0 (expressing the relative amount of octupole vs. quadrupole deformation) and beta_0 (the position of the minimum of the Davidson potential), while the recently determined B(EL) transition rates of 224Ra, presenting stable octupole deformation, are successfully reproduced. A procedure for gradually determining the parameters appearing in the B(EL) transitions from a minimum set of data, thus increasing the predictive power of the model, is out...

Bonatsos, Dennis; Minkov, N; Karampagia, S; Petrellis, D

2015-01-01

174

Constraining the central magnetic field of magnetars  

OpenAIRE

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 ...

Mukhopadhyay, Banibrata; Sinha, Monika

2013-01-01

175

Search for two-octupole-phonon states in 208Pb  

Science.gov (United States)

A search for two-phonon octupole vibrational states in 208Pb was carried out using the 207Pb(n th, ?) reaction at the High Flux Reactor of the Institut Laue-Langevin. The conversion electron spectrum was scanned with the spectrometer BILL with a sensitivity of 20 ?b in the 4-6 MeV interval. Coincidence and singles ?-ray measurements were performed at the end of the thermal neutron beam guide H22-F reaching a sensitivity of 80 ?b for energies above 0.511 MeV. In addition the singles spectrum was investigated with the pair spectrometer at the tangential beam facility. Levels have been observed at (energies in keV and parenthesis for tentative level identification and spin-parity assignments): 2614.4, 3 -; 3997, (3 -); 4084.7, 2 +; 4253, (2 -, 3 -); 4704, (2 -, 3 -); (4882.0), (0 +); (4904.9), (0 +); 4935, 2 +; (6343), (2 +) and the 0 -, 1 - capture state at 7367.9 keV. The 4882.0 keV level probably corresponds to the known two-neutron pairing vibration. Possible candidates for two-phonon octupole excitations are the (0 +)(4904.9) and 2 + 4935 keV states. The nuclear field theory formalism is used to calculate branching ratios and energies for states in 208Pb under several assumptions. The most inimportant result of the comparison of theory and experiment is that the experimental properties of the 2 + 4935 keV state favour the interpretation of this state as a two-phonon octupole vibration rather than as a one-phonon non-collective quadrupole state.

Mariscotti, M. A. J.; Bes, D. R.; Reich, S. L.; Sofía, H. M.; Hungerford, P.; Kerr, S. A.; Schreckenbach, K.; Warner, D. D.; Davidson, W. F.; Gelletly, W.

1983-10-01

176

Magnetic fields of the magnetosheath  

International Nuclear Information System (INIS)

The magnetic field of the magnetosheath is most naturally discussed in terms of its steady state and its fluctuating components. The theory of the steady state field is quite well developed, and its essential features have been confirmed by observations. The interplanetary field is convected through the bow shock where its magnitude is increased and its direction changed by the minimal amount necessary to preserve the normal component across the shock. Convection within the magnetosheath usually increases the magnitude still further near the subsolar point and further distorts the direction until the field is aligned approximately tangent to the magnetopause. Fluctuations of the magnetosheath field are very complex, variable, and not well understood. Power spectra of the field typically vary as 1/f or 1/f2 below and 1/f3 above the proton gyrofrequency. Spectral peaks are common features which occur at different frequencies at various times. Transverse waves are often dominant at frequencies less than or equal to 0.002 Hz, and compressional waves are often dominant at somewhat higher frequencies. Perturbation vectors of hydromagnetic waves tend to be aligned with the shock and magnetopause surfaces. Magnetosheath waves may be generated upstream, within the magnetosheath, at the bow shock, or at the magnetopause, but the relative importance of these sources is not known. 83 references

177

Stray field magnetic resonance imaging  

International Nuclear Information System (INIS)

Magnetic resonance imaging (MRI) is well known in a clinical context as a technique capable of delivering highly detailed anatomical images, particularly of soft tissue. The MRI method is completely non-invasive and allows spatial resolution down to a few micrometres in three dimensions. Image contrast is governed by one of several nuclear magnetic resonance parameters and might reflect water mobility, chemical potential, self-diffusion coefficient, coherent flow or temperature, depending upon the exact form of the MRI measurement. Less widely realized is the enormous potential for the use of MRI in materials science. The flexibility that makes MRI such a valuable clinical tool is equally applicable in a non-medical scenario, but the greater technical difficulties associated with MRI in solid materials have hitherto limited the development of the technique in this area. This review describes in detail one approach to MRI in solid materials which is currently benefiting from rapidly increasing application: stray field (magnetic resonance) imaging (STRAFI). An introduction to the phenomenon of nuclear magnetic resonance and particularly its detection in solids is followed by a description of the steps necessary for its use as an imaging modality. The limits of MRI spatial resolution in liquids and solids are briefly discussed. STRAFI is placed in context throughout this introduction. The STRAFI technique is then described in detail, in terms of its merits relative to otail, in terms of its merits relative to other approaches to solids MRI and the subtleties of its implementation. The principal areas of current STRAFI application are reviewed and developments with which STRAFI advancement is closely linked, are also described. In conclusion, some consideration is given to the promising future of stray field MRI as a widely accepted research tool in materials science and to the development of the technique itself. (author)

178

Hypernuclear matter in strong magnetic field  

CERN Document Server

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

179

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

2013-06-01

180

Holography, Fractionalization and Magnetic Fields  

CERN Document Server

Four dimensional gravity with a U(1) gauge field, coupled to various fields in asymptotically anti-de Sitter spacetime, provides a rich arena for the holographic study of the strongly coupled (2+1)-dimensional dynamics of finite density matter charged under a global U(1). As a first step in furthering the study of the properties of fractionalized and partially fractionalized degrees of freedom in the strongly coupled theory, we construct electron star solutions at zero temperature in the presence of a background magnetic field. We work in Einstein-Maxwell-dilaton theory. In all cases we construct, the magnetic source is cloaked by an event horizon. A key ingredient of our solutions is our observation that starting with the standard Landau level structure for the density of states, the electron star limits reduce the charge density and energy density to that of the free fermion result. Using this result we construct three types of solution: One has a star in the infra-red with an electrically neutral horizon, ...

Albash, Tameem; MacDonald, Scott

2013-01-01

181

Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization  

Science.gov (United States)

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

182

Emission of magnetic fields from distribution lines  

International Nuclear Information System (INIS)

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

183

The magnetic field gradients generation for magnetic resonance tomography  

International Nuclear Information System (INIS)

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

184

Fringing field measurement of dipole magnet  

International Nuclear Information System (INIS)

The fringing field of a dipole magnet with a C-type circuit and homogeneous field in the gap has been measured including the distributions of fringing fields with and without magnetic shield. The measured data was analyzed by using the concept of virtual field boundary

185

Rydberg atoms in magnetic and electric fields  

International Nuclear Information System (INIS)

This chapter examines highly excited atoms in the presence of a uniform field, magnetic or electric. It discusses Rydberg atoms in magnetic fields; Rydberg atoms in electric fields; and Rydberg atoms in crossed fields. It reviews present knowledge of this subject which is of great theoretical interest and which has recently benefited from laser spectroscopy

186

Near-Field Magnetic Dipole Moment Analysis  

Science.gov (United States)

This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective magnetic dipole moment model. The model is most accurate with the earth s geomagnetic field cancelled in a spherical region bounded by the measurement magnetometers with a minimum radius large enough to enclose the magnetic source. Considerably enhanced spacecraft magnetic testing is offered by using this technique in conjunction with a computer-controlled magnetic field measurement system. Such a system, with real-time magnetic field display capabilities, has been incorporated into other existing magnetic measurement facilities and is also used at remote locations where transport to a magnetics test facility is impractical.

Harris, Patrick K.

2003-01-01

187

Magnetic Gradient edge magnetoplasmons in non-uniform magnetic field  

OpenAIRE

We have theoretically studied two-dimensional electron gas placed in a strong laterally non-uniform magnetic field, which appears due to ferromagnetic film . We have found, that in this case 2DEG experiences static charge redistribution that strongly depends on presence and configuration of the gates on the surface of a heterostructure. Also, it is shown that lateral inhomogeneity of a strong magnetic field allows itself “magnetic gradient” or “magnetic-edge” magnetoplasmons due ...

Balev, O. G.; Larkin, Ivan

2012-01-01

188

Strong and superstrong pulsed magnetic fields generation  

CERN Document Server

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.

Shneerson, German A; Krivosheev, Sergey I

2014-01-01

189

Full 180° Magnetization Reversal with Electric Fields  

Science.gov (United States)

Achieving 180° magnetization reversal with an electric field rather than a current or magnetic field is a fundamental challenge and represents a technological breakthrough towards new memory cell designs. Here we propose a mesoscale morphological engineering approach to accomplishing full 180° magnetization reversals with electric fields by utilizing both the in-plane piezostrains and magnetic shape anisotropy of a multiferroic heterostructure. Using phase-field simulations, we examined a patterned single-domain nanomagnet with four-fold magnetic axis on a ferroelectric layer with electric-field-induced uniaxial strains. We demonstrated that the uniaxial piezostrains, if non-collinear to the magnetic easy axis of the nanomagnet at certain angles, induce two successive, deterministic 90° magnetization rotations, thereby leading to full 180° magnetization reversals.

Wang, J. J.; Hu, J. M.; Ma, J.; Zhang, J. X.; Chen, L. Q.; Nan, C. W.

2014-12-01

190

Magnetic field calculation and measurement of active magnetic bearings  

Science.gov (United States)

Magnetic Bearings are typical devices in which electric energy and mechanical energy convert mutually. Magnetic Field indicates the relationship between 2 of the most important parameters in a magnetic bearing - current and force. This paper presents calculation and measurement of the magnetic field distribution of a self-designed magnetic bearing. Firstly, the static Maxwell's equations of the magnetic bearing are presented and a Finite Element Analysis (FEA) is found to solve the equations and get post-process results by means of ANSYS software. Secondly, to confirm the calculation results a Lakeshore460 3-channel Gaussmeter is used to measure the magnetic flux density of the magnetic bearing in X, Y, Z directions accurately. According to the measurement data the author constructs a 3D magnetic field distribution digital model by means of MATLAB software. Thirdly, the calculation results and the measurement data are compared and analyzed; the comparing result indicates that the calculation results are consistent with the measurement data in allowable dimension variation, which means that the FEA calculation method of the magnetic bearing has high precision. Finally, it is concluded that the magnetic field calculation and measurement can accurately reflect the real magnetic distribution in the magnetic bearing and the result can guide the design and analysis of the magnetic bearing effectively.

Ding, Guoping; Zhou, Zude; Hu, Yefa

2006-11-01

191

Diluted magnetic semiconductors: Novel properties in high magnetic fields  

Science.gov (United States)

Diluted magnetic semiconductors, II-VI and IV-VI compounds in which the cation is partially replaced by a magnetic ion such as Mn or a rare earth, combine interesting semiconducting and magnetic properties. At zero applied field, the materials behave like normal semiconductors or semimetals with energy gaps that can be varied with the composition of the magnetic ion. In the presence of an applied field, however, novel properties are observed. These include large field-induced splittings of energy levels, leading to strong Faraday rotations and the possibility of energy-gap tuning by magnetic field, field and temperature-dependent g-factors, large negative magnetoresistance followed at higher fields by a slowly varying positive magnetoresistance, and large paramagnetism with coupling of the magnetic ions by superexchange. Not only can these properties be observed in bulk crystal, but also they suggest promising physics and applications in artificially structured materials.

Anderson, J. R.

1990-06-01

192

Deformation of Water by a Magnetic Field  

Science.gov (United States)

After the discovery that superconducting magnets could levitate diamagnetic objects, researchers became interested in measuring the repulsion of diamagnetic fluids in strong magnetic fields, which was given the name "The Moses Effect." Both for the levitation experiments and the quantitative studies on liquids, the large magnetic fields necessary…

Chen, Zijun; Dahlberg, E. Dan

2011-01-01

193

Exploring Magnetic Fields with a Compass  

Science.gov (United States)

A compass is an excellent classroom tool for the exploration of magnetic fields. Any student can tell you that a compass is used to determine which direction is north, but when paired with some basic trigonometry, the compass can be used to actually measure the strength of the magnetic field due to a nearby magnet or current-carrying wire. In this…

Lunk, Brandon; Beichner, Robert

2011-01-01

194

Magnetic fields for surface containment of plasmas  

International Nuclear Information System (INIS)

Magnetic fields produced by a periodic array of rectangular bars magnetized perpendicular to their lengths have proven to be useful boundaries for plasma containment. Convenient formulas are developed for the computation of the magnetic fields for any choice of parameters. These formulas include not only the configuration which has commonly been used, but some alternate arrangements which can be advantageous for certain applications

195

Temperature strain and magnetic field measurements  

International Nuclear Information System (INIS)

This chapter describes the devices most widely used for measuring temperature, strain and magnetic field. The measurement of temperature is emphasized because it is the primary variable in nearly all low-temperature material properties. Topics considered include techniques for low temperatures, transducer-specimen contact, signals maintenance, temperature scales, resistance thermometers, measuring resistance, platinum resistance thermometers, carbon resistance thermometers, thermocouples, thermocouple calibration, filled systems, vapor-pressure thermometers, gas thermometers, the properties of fluids, diode thermometers, temperature measurement in magnetic fields, thermocouples in magnetic fields, apparent strain, the gauge factor, strain measurements in magnetic fields, types of strain gauges, nuclear magnetic resonance, Faraday coil gaussmeters, and Hall effect gaussmeters

196

Baryon onset in a magnetic field  

CERN Document Server

The critical baryon chemical potential for the onset of nuclear matter is a function of the vacuum mass and the binding energy. Both quantities are affected by an external magnetic field. We show within two relativistic mean-field models - including magnetic catalysis, but omitting the anomalous magnetic moment - that a magnetic field increases both the vacuum mass and the binding energy. For sufficiently large magnetic fields, the effect on the vacuum mass dominates and as a result the critical baryon chemical potential is increased.

Haber, Alexander; Schmitt, Andreas

2014-01-01

197

Neutrino Conversions in Solar Random Magnetic Fields  

OpenAIRE

We consider the effect of a random magnetic field in the convective zone of the Sun superimposed to a regular magnetic field on resonant neutrino spin-flavour oscillations. We argue for the existence of a field of strongly chaotic nature at the bottom of the convective zone. In contrast to previous attempts we employ in addition a model motivated regular twisting magnetic field profile. In this scenario electron antineutrinos are produced through cascades like $\

Semikoz, V. B.; Torrente-lujan, E.

1998-01-01

198

Dynamic shielding of the magnetic fields  

OpenAIRE

The paper presents a comparative study of the methods used to control and compensate the direct and alternative magnetic fields. Two frequently used methods in the electromagnetic compatibility of the complex biomagnetism installations were analyzed. The two methods refer to the use of inductive magnetic field sensors (only for alternative fields) and of fluxgate magnetometers as active transducers which measures both the direct and alternative components of the magnetic field. The applica...

Rau, M.; Costandache, D.; Baltag, O.; Iftemie, A.; Rau, I.

2010-01-01

199

Asymmetric Diffusion of Magnetic Field Lines  

OpenAIRE

Stochasticity of magnetic field lines is important for particle transport properties. Magnetic field lines separate faster than diffusively in turbulent plasma, which is called superdiffusion. We discovered that this superdiffusion is pronouncedly asymmetric, so that the separation of field lines along the magnetic field direction is different from the separation in the opposite direction. While the symmetry of the flow is broken by the so-called imbalance or cross-helicity,...

Beresnyak, Andrey

2013-01-01

200

Topological constraints on magnetic field relaxation  

OpenAIRE

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 he...

Candelaresi, Simon; Brandenburg, Axel

2012-01-01

201

Electrolytic tiltmeters inside magnetic fields: Some observations  

International Nuclear Information System (INIS)

We present observations of the electrolytic clinometers behaviour inside magnetic field environments introducing phenomenological expressions to account for the measured output voltage variations as functions of field gradients and field strengths

202

Neutron star deformation due to arbitrary-order multipolar magnetic fields  

CERN Document Server

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

203

Adgezator magnetic field disturbance by multiturn disconnected magnetic coils  

International Nuclear Information System (INIS)

To reduce magnetic field disturbance of the adgezator and that of its gradients a method is proposed for calculation of currents induced by pulsed magnetic field in multiturn disconnected coils, and for calculation of their fields. The method proposed does not require any preliminary measurements. A comparison is made with results of magnetic measurements on adgezator of heavy ion accelerator, which are in a good agreement with the experiment

204

Phase field simulation of spinodal decomposition under external magnetic field  

International Nuclear Information System (INIS)

A computational model was developed to simulate the spinodal decomposition process of ferromagnetic alloys under an external magnetic field. In this model, the temporal evolution of the modulated structure was described by a phase field method, and the magnetic configuration was solved by using a micromagnetic method. The spinodal decomposition and coarsening processes of a single magnetic particle and an A-B hypothetical system under an external magnetic field were simulated using the proposed model. The simulation results show that the precipitated particles were elongated along the direction of the external magnetic field. The dependence of the modulated structure of an A-B hypothetic system on external magnetic field is much more sensitive than that of the single particle structure. The simulation results also demonstrate that the modulation of the external magnetic field is effective even if the spinodal decomposition has been completed and a stable modulated structure was formed.

205

Abnormal Magnetic Field Effects on Electrogenerated Chemiluminescence  

Science.gov (United States)

We report abnormal magnetic field effects on electrogenerated chemiluminescence (MFEECL) based on triplet emission from the Ru(bpy)3Cl2-TPrA electrochemical system: the appearance of MFEECL after magnetic field ceases. In early studies the normal MFEECL have been observed from electrochemical systems during the application of magnetic field. Here, the abnormal MFEECL suggest that the activated charge-transfer [Ru(bpy)33+ … TPrA•] complexes may become magnetized in magnetic field and experience a long magnetic relaxation after removing magnetic field. Our analysis indicates that the magnetic relaxation can gradually increase the density of charge-transfer complexes within reaction region due to decayed magnetic interactions, leading to a positive component in the abnormal MFEECL. On the other hand, the magnetic relaxation facilitates an inverse conversion from triplets to singlets within charge-transfer complexes. The inverse triplet ? singlet conversion reduces the density of triplet light-emitting states through charge-transfer complexes and gives rise to a negative component in the abnormal MFEECL. The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFEECL after ceasing magnetic field. Nevertheless, our experimental studies may reveal un-usual magnetic behaviors with long magnetic relaxation from the activated charge-transfer [Ru(bpy)33+ … TPrA•] complexes in solution at room temperature. PMID:25772580

Pan, Haiping; Shen, Yan; Wang, Hongfeng; He, Lei; Hu, Bin

2015-01-01

206

Abnormal magnetic field effects on electrogenerated chemiluminescence.  

Science.gov (United States)

We report abnormal magnetic field effects on electrogenerated chemiluminescence (MFEECL) based on triplet emission from the Ru(bpy)3Cl2-TPrA electrochemical system: the appearance of MFEECL after magnetic field ceases. In early studies the normal MFEECL have been observed from electrochemical systems during the application of magnetic field. Here, the abnormal MFEECL suggest that the activated charge-transfer [Ru(bpy)3(3+) … TPrA(•)] complexes may become magnetized in magnetic field and experience a long magnetic relaxation after removing magnetic field. Our analysis indicates that the magnetic relaxation can gradually increase the density of charge-transfer complexes within reaction region due to decayed magnetic interactions, leading to a positive component in the abnormal MFEECL. On the other hand, the magnetic relaxation facilitates an inverse conversion from triplets to singlets within charge-transfer complexes. The inverse triplet ? singlet conversion reduces the density of triplet light-emitting states through charge-transfer complexes and gives rise to a negative component in the abnormal MFEECL. The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFEECL after ceasing magnetic field. Nevertheless, our experimental studies may reveal un-usual magnetic behaviors with long magnetic relaxation from the activated charge-transfer [Ru(bpy)3(3+) … TPrA(•)] complexes in solution at room temperature. PMID:25772580

Pan, Haiping; Shen, Yan; Wang, Hongfeng; He, Lei; Hu, Bin

2015-01-01

207

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.

RAU, M.

2010-11-01

208

Measurements of magnetic field of superconducting solenoid  

International Nuclear Information System (INIS)

The method of measurements for a superconducting focusing magnetic system of the cryogenic electron-beam ion source in nonuniform regions is proposed. The experimental data show high uniformity and axial symmetry of the magnetic field

209

Magnetic fields in the early universe  

CERN Document Server

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

Subramanian, Kandaswamy

2009-01-01

210

Field free line magnetic particle imaging  

CERN Document Server

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

Erbe, Marlitt

2014-01-01

211

Structure and magnetic field of periodic permanent magnetic focusing system with open magnetic rings  

Energy Technology Data Exchange (ETDEWEB)

The magnetic field along the central axis for an axially magnetized permanent magnetic ring was investigated by analytical and finite element methods. For open magnetic rings, both calculated and measured results show that the existence of the radial magnetic field creates a remarkable cosine distribution field along the central axis. A new structure of periodic permanent magnet focusing system with open magnetic rings is proposed. The structure provides a satisfactory magnetic field with a stable peak value of 120 mT for a traveling wave tube system. - Research highlights: For open magnetic rings, both calculated and measured results show that the existence of the radial magnetic field creates a remarkable cosine distribution field along the central axis. A new structure of periodic permanent magnet (PPM) focusing system with open magnetic rings is proposed. The new PPM focusing system with open magnetic rings meets the requirements for TWT system.

Peng Long, E-mail: plxkd@sina.co [College of Optoelectronics Technology, Chengdu University of Information Technology, Chengdu 610225 (China); Li Lezhong; Yang Dingyu; Zhu Xinghua [College of Optoelectronics Technology, Chengdu University of Information Technology, Chengdu 610225 (China); Li Yuanxun [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)

2011-06-15

212

Nonlinear physics of twisted magnetic field lines  

International Nuclear Information System (INIS)

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

213

Synchrotron Applications of High Magnetic Fields  

International Nuclear Information System (INIS)

This workshop aims at discussing the scientific potential of X-ray diffraction and spectroscopy in magnetic fields above 30 T. Pulsed magnetic fields in the range of 30 to 40 T have recently become available at Spring-8 and the ESRF (European synchrotron radiation facility). This document gathers the transparencies of the 6 following presentations: 1) pulsed magnetic fields at ESRF: first results; 2) X-ray spectroscopy and diffraction experiments by using mini-coils: applications to valence state transition and frustrated magnet; 3) R5(SixGe1-x)4: an ideal system to be studied in X-ray under high magnetic field?; 4) high field studies at the Advanced Photon Source: present status and future plans; 5) synchrotron X-ray diffraction studies under extreme conditions; and 6) projects for pulsed and steady high magnetic fields at the ESRF

214

Magnetic nanoparticle sensing: decoupling the magnetization from the excitation field  

OpenAIRE

Remote sensing of magnetic nanoparticles has exciting applications for magnetic nanoparticle hyperthermia and molecular detection. We introduce, simulate, and experimentally demonstrate an innovation---a sensing coil that is geometrically decoupled from the excitation field---for magnetic nanoparticle spectroscopy that increases the flexibility and capabilities of remote detection. The decoupling enhances the sensitivity absolutely; to small amounts of nanoparticles, and rel...

Reeves, Daniel B.; Weaver, John B.

2014-01-01

215

Magnetic fields in classical Be stars  

OpenAIRE

We report the results of our study of magnetic fields in a sample of Be stars using spectropolarimetric data obtained at the European Southern Observatory with the multi-mode instrument FORS1 installed at the 8m Kueyen telescope. The detected magnetic fields are rather weak, not stronger than ~150G. A few classical Be stars display cyclic variability of the magnetic field with periods of tens of minutes.

Yudin, R.; Hubrig, S.; Pogodin, M.; Savanov, I.; Schoeller, M.; Peters, G.; Cure, M.

2009-01-01

216

Graphene spin capacitor for magnetic field sensing  

OpenAIRE

An analysis of a novel magnetic field sensor based on a graphene spin capacitor is presented. The proposed device consists of graphene nanoribbons on top of an insulator material connected to a ferromagnetic source/drain. The time evolution of spin polarized electrons injected into the capacitor can be used for an accurate determination at room temperature of external magnetic fields. Assuming a spin relaxation time of 100 ns, magnetic fields on the order of $\\sim 10$ mOe ma...

Semenov, Y. G.; Zavada, J. M.; Kim, K. W.

2010-01-01

217

The Magnetic Field in the Solar Atmosphere  

OpenAIRE

This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphe...

Wiegelmann, Thomas; Thalmann, Julia K.; Solanki, Sami K.

2014-01-01

218

Magnetic Field Measurement with Ground State Alignment  

OpenAIRE

Observational studies of magnetic fields are crucial. We introduce a process "ground state alignment" as a new way to determine the magnetic field direction in diffuse medium. The alignment is due to anisotropic radiation impinging on the atom/ion. The consequence of the process is the polarization of spectral lines resulting from scattering and absorption from aligned atomic/ionic species with fine or hyperfine structure. The magnetic field induces precession and realign th...

Yan, Huirong; Lazarian, A.

2013-01-01

219

Magnetic Field Instabilities in Neutron Stars  

OpenAIRE

Magnetic fields represent a crucial aspect of the physics and astrophysics of neutron stars. Despite its great relevance, the internal magnetic field configuration of neutron stars is very poorly constrained by the observations, and understanding its properties is a long-standing theoretical challenge. The investigation on the subject is focused on the search for those magnetic field geometries which are stable on several Alfv\\`en timescales, thus constituting a viable descr...

Ciolfi, Riccardo

2014-01-01

220

Magnetic field screening effect in electroweak model  

OpenAIRE

It is shown that in the Weinberg-Salam model a magnetic field screening effect for static magnetic solutions takes place. The origin of this phenomenon can be traced to the mutual cancellation of Abelian magnetic fields created by the SU(2) gauge fields and Higgs boson. The effect implies monopole charge screening in the finite energy system of monopoles and antimonopoles. We consider another manifestation of the screening effect which leads to an essential energy decrease o...

Bakry, A. S.; Pak, D. G.; Zhang, P. M.; Zou, L. P.

2014-01-01

221

Magnetic field effects on plasma ionization balance  

Energy Technology Data Exchange (ETDEWEB)

Magnetic fields give rise to several phenomena that can significantly affect ionization balance in a plasma. Theoretical models commonly used to determine the charge state distribution (viz., ) of ions in non-magnetized plasmas are reviewed first, for both equilibrium and non-equilibrium situations. Then, after a brief survey of laboratory and cosmic plasmas with strong fields, B > 10{sup 6} Gauss, some of the ways such magnetic fields influence are highlighted. Most key problems have yet to be tackled.

Weisheit, J.C.

1995-12-31

222

Multielectronic Atom in Magnetic Field Revisited  

OpenAIRE

The motion of a multi-electronic atom in an external electro-magnetic field is reconsidered. We prove that according to classical mechanics and electrodynamics, the assumption that the interaction with the magnetic field is described by means of a potential energy is no valid, and the trajectory of the center of mass can be deflected by a magnetic field, even if the internal angular momentum is zero. The characteristic equation of the corresponding hamiltonian is not separab...

Chavoya-aceves, O.

2003-01-01

223

Solar Force-free Magnetic Fields  

OpenAIRE

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 ma...

Thomas Wiegelmann; Takashi Sakurai

2012-01-01

224

A magnetic shield for large-bore, high field magnets.  

Science.gov (United States)

An effective shield for the dc fringing fields produced by a large-bore, high field magnet intended for imaging and in vivo spectroscopy is presented. While limiting the extent of fringe fields, the shield has little effect on the homogeneity of the central field of the magnet. The effect of institutional safety policies as well as the exigencies of patient access in a hospital environment are emphasized as influences on the planning of an in vivo NMR installation. PMID:4094560

Ewing, J R; Timms, W; Williams, J E; Welch, K M

1985-10-01

225

Magnetic fields in nearby galaxies  

CERN Document Server

We describe a recent full-polarization radio continuum survey, performed using the Westerbork Synthesis Radio Telescope (WSRT), of several nearby galaxies in the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample. The WSRT-SINGS survey has been utilized to study the polarized emission and Faraday rotation measures (RMs) in the targets, and reveals an important new observational trend. The azimuthal distribution of polarized flux seems to be intimately related to the kinematic orientation of galaxies, such that in face-on galaxies the lowest level of polarized flux is detected along the kinematic major axis. In highly inclined galaxies, the polarized flux is minimized on both ends of the major axis, and peaks near the minor axis. Using models of various three-dimensional magnetic field geometries, and including the effects of turbulent depolarization in the midplane, we are able to reproduce the qualitative distribution of polarized flux in the target galaxies, its variation with inclination, and the distr...

Heald, G

2009-01-01

226

Spin assignment of the lowest octupole bandhead in 236U  

International Nuclear Information System (INIS)

Measurements carried out to determine the nature of the octupole bandhead in 236U led in the past to considerable confusion concerning its spin assignment. To see whether penetration effects are important in the conversion electron decay of the octupole band, a high resolution measurement was carried out at the #betta#-spectrometer of the ILL. Relative intensities have been determined for the transitions from the octupole bandhead to the O+, 2+ and 4+ members of the ground state rotational. (U.K.)

227

Minimizing magnetic fields for precision experiments  

CERN Document Server

An increasing number of measurements in fundamental and applied physics rely on magnetically shielded environments with sub nano-Tesla residual magnetic fields. State of the art magnetically shielded rooms (MSRs) consist of up to seven layers of high permeability materials in combination with highly conductive shields. Proper magnetic equilibration is crucial to obtain such low magnetic fields with small gradients in any MSR. Here we report on a scheme to magnetically equilibrate MSRs with a 10 times reduced duration of the magnetic equilibration sequence and a significantly lower magnetic field with improved homogeneity. For the search of the neutron's electric dipole moment, our finding corresponds to a linear improvement in the systematic reach and a 40 % improvement of the statistical reach of the measurement. However, this versatile procedure can improve the performance of any MSR for any application.

Altarev, I; Lins, T; Marino, M G; Nießen, B; Petzoldt, G; Reisner, M; Stuiber, S; Sturm, M; Singh, J T; Taubenheim, B; Rohrer, H K; Schläpfer, U

2015-01-01

228

Magnetic-field transfer of water molecules  

Science.gov (United States)

Thermal agitation induces the rotational motion of the two positively charged hydrogens around the oxygen nucleus in a water molecule, which forms an electric current with a short duration, generating a Lorentz force in a uniform static magnetic field. Since the center of gravity of a water molecule is approximately located at the oxygen nucleus, the Lorentz force has two components that rotate the hydrogens and push the oxygen nucleus. The component of the Lorentz force that pushes the oxygen nucleus parallel to the magnetic field has a strength that is half that of the component that pushes the oxygen nucleus perpendicular to the magnetic field. Since the Lorentz force causes water molecules to carry out a random walk, magnetic-field transfer, that is, a cumulative effect of random walks, is expected. The ratio of the diffusional coefficient for the magnetic-field transfer of D2O to that of H2O is 4:1 because the ratio of the interval between each random walk of D2O to that of H2O, which is also the ratio of the duration of one rotation, is 2:1. The diffusional displacement of the magnetic-field transfer is proportional to the magnetic field and reaches 0.62 Å/day for liquid water at 37 °C in a magnetic field of 2.0 T. Magnetic-field transfer is predicted to occur in polarized molecules with rotational freedom and restricted translational freedom.

Osuga, Toshiaki; Tatsuoka, Hozumi

2009-11-01

229

Autowave dissipation of forceless magnetic fields  

International Nuclear Information System (INIS)

It is shown that in a forceless magnetic field regions with strongly enhanced current density can be compressed irreversibly in a process of ohmic dissipation (resistive collapse). An example of such a structure is a plane current layer in a homogeneous magnetic field. In the presence of sources that restore in the layer the shear of the magnetic field lines (and, accordingly, the current) the dissipation process may be auto-oscillatory. The magnetic field of an active region containing forceless current layers can be regarded as an excitable nonlinear medium in which autowave propagation is possible. The energy and time characteristics of collapsing current layers are close to those of flares

230

Magnetic fields in the early universe  

OpenAIRE

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 t...

Grasso, Dario; Rubinstein, H. R.

2009-01-01

231

Ferroelectric Cathodes in Transverse Magnetic Fields  

International Nuclear Information System (INIS)

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

232

Domestic magnetic fields. Protocols, measurements and results  

International Nuclear Information System (INIS)

The quantification of magnetic field exposure has been the subject of considerable debate. A number of surrogates have been used including, spot measurements, wire coding and 24 hour averages. The quantification of domestic magnetic fields including the identification of sources is important if any mitigation is required. The State Electricity Commission of Victoria has developed recording instrumentation and measurement protocols for the survey of domestic magnetic field strengths in the Melbourne area. A range of domestic locations in the Melbourne metropolitan area is chosen to test the influence of external installations and the effect of appliance usage and energy consumption on the domestic magnetic field environment. (author)

233

Five years of magnetic field management  

International Nuclear Information System (INIS)

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

234

Magnetic field screening effect in electroweak model  

CERN Document Server

It is shown that in the Weinberg-Salam model a magnetic field screening effect for static magnetic solutions takes place. The origin of that phenomenon is conditioned by features of the electro-weak interaction, namely, there is mutual cancellation of Abelian magnetic fields created by the SU(2) gauge fields and Higgs boson. The effect implies monopole charge screening in finite energy system of monopoles and antimonopoles. We consider another manifestation of the screening effect which leads to an essential energy decrease of magnetic solutions. Applying variational method we have found a magnetic field configuration with a topological azimuthal magnetic flux which minimizes the energy functional and possesses a total energy of order 1 TeV. We suppose that corresponding magnetic bound state exists in the electroweak theory and can be detected in experiment.

Bakry, A; Zhang, P M; Zou, L P

2014-01-01

235

Swarm: ESA's Magnetic Field Mission  

Science.gov (United States)

Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme, and is scheduled for launch in 2012. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution using a constellation of 3 identical satellites. The Mission shall deliver data that allow access to new insights into the Earth system by improved scientific understanding of the Earth's interior and near-Earth electromagnetic environment. After launch and triple satellite release at an initial altitude of about 490 km, a pair of the satellites will fly side-by-side with slowly decaying altitude, while the third satellite will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission science goals are to provide a unique view into Earth core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently approaching the final stage of the development phase, will be addressed. A consortium of European scientific institutes is developing a distributed processing system to produce geophysical (Level 2) data products to the Swarm user community. The setup of Swarm ground segment and the contents of the data products will be addressed. More information on the Swarm mission can be found at the mission web site (see URL below).

Drinkwater, M. R.; Haagmans, R.; Floberghagen, R.; Plank, G.; Menard, Y.

2011-12-01

236

Microscopic description of octupole shape-phase transitions in light actinide and rare-earth nuclei  

Science.gov (United States)

A systematic analysis of low-lying quadrupole and octupole collective states is presented based on the microscopic energy density functional framework. By mapping the deformation constrained self-consistent axially symmetric mean-field energy surfaces onto the equivalent Hamiltonian of the sdf interacting boson model (IBM), that is, onto the energy expectation value in the boson condensate state, the Hamiltonian parameters are determined. The study is based on the global relativistic energy density functional DD-PC1. The resulting IBM Hamiltonian is used to calculate excitation spectra and transition rates for the positive- and negative-parity collective states in four isotopic chains characteristic for two regions of octupole deformation and collectivity: Th, Ra, Sm, and Ba. Consistent with the empirical trend, the microscopic calculation based on the systematics of ?2-?3 energy maps, the resulting low-lying negative-parity bands and transition rates show evidence of a shape transition between stable octupole deformation and octupole vibrations characteristic for ?3-soft potentials.

Nomura, K.; Vretenar, D.; Nikši?, T.; Lu, Bing-Nan

2014-02-01

237

Quadrupole and octupole collectivity in 148Nd  

International Nuclear Information System (INIS)

The role of quadrupole and octupole collectivity in the shape-transitional nucleus 148Nd has been studied by Coulomb excitation using beams of 58Ni and 92Mo, and a beam of 148Nd (using a 208Pb target). The extracted E1, E2 and E3 matrix elements involving states up to 12+ in the ground band and 13- in the negative-parity band are presented, and compared to calculations that assume a vibrational and rotational octupole nature for the negative-parity band. The positive-parity ground-band states are well described in terms of a prolate deformed shape with Q20?400 e fm2 (?2rms?+0.18). The present results suggest a vibrational octupole nature for the low-spin negative-parity states, with an intrinsic moment Q30?1500 e fm3 (?3rms?0.12). The E2 and E3 matrix elements connecting these bands to the ?- and ?-vibrational bands (and within these bands) are also presented, and compared to calculations incorporating the coupling between the rotational and vibrational modes. These calculations describe reasonably well the E2 matrix elements involving the gamma band, but do not reproduce the measured E2 matrix elements for the beta band, implying a complicated intrinsic structure for the beta band. The strong enhancement of the measured E3 matrix elements connecting the negative-parity band to the beta band coarity band to the beta band could be indicative of a significant component of the two-phonon octupole vibration in the wavefunction of the so-called beta band. (orig.)

238

Magnetic field evolution in interacting galaxies  

Science.gov (United States)

Aims: Violent gravitational interactions can change the morphologies of galaxies and, by means of merging, transform them into elliptical galaxies. We aim to investigate how they affect the evolution of galactic magnetic fields. Methods: We selected 16 systems of interacting galaxies with available VLA archive radio data at 4.86 and 1.4 GHz and compared their radio emission and estimated magnetic field strengths with their star-forming activity, far-infrared emission, and the stage of tidal interaction. Results: The estimated mean of total magnetic field strength for our sample of interacting galaxies is 14 ± 5 ?G, which is larger than for the non-interacting objects. The field regularity (of 0.27 ± 0.09) is lower than in typical spirals and indicates enhanced production of random magnetic fields in the interacting objects. We find a general evolution of magnetic fields: for weak interactions the strength of magnetic field is almost constant (10-15 ?G) as interaction advances, then it increases up to 2× , peaks at the nuclear coalescence (25 ?G), and decreases again, down to 5-6 ?G, for the post-merger remnants. The main production of magnetic fields in colliding galaxies thus terminates somewhere close to the nuclear coalescence, after which magnetic field diffuses. The magnetic field strength for whole galaxies is weakly affected by the star formation rate (SFR), while the dependence is higher for galactic centres. We show that the morphological distortions visible in the radio total and polarized emission do not depend statistically on the global or local SFRs, while they do increase (especially in the polarization) with the advance of interaction. The constructed radio-far-infrared relations for interacting and non-interacting galaxies display a similar balance between the generation of cosmic rays, magnetic fields, and the production of the thermal energy and dust radiation. Conclusions: The regular magnetic fields are much more sensitive to morphological distortions induced by tidal interactions than are the random fields. As a result the polarized emission could be yet another indicator of an ongoing merging process. The found evolution of magnetic field with advancing interaction would definitely imply a stronger effect of magnetic fields on the galaxy surroundings in the earlier cosmological epochs. The process of strong gravitational interactions can efficiently magnetize the merger's surroundings, having a similar magnetizing effect on intergalactic medium as supernova explosions or galactic winds. If interacting galaxies generate some ultra-high energy cosmic rays (UHECRs), the disk or magnetized outflows can deflect them (up to 23°), and make an association of the observed UHECRs with the sites of their origin very uncertain.

Drzazga, R. T.; Chy?y, K. T.; Jurusik, W.; Wiórkiewicz, K.

2011-09-01

239

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

2012-09-01

240

Comment on "Magnetic Relaxations of Antiferromagnetic Nanoparticles in Magnetic Fields"  

CERN Document Server

We have carried out in ferritin the Field-Cooling method and data analysis proposed by Mamiya et al. (Phys. Rev. Lett. 88, 67202 (2002) at T = 5 K in order to check the time magnetic relaxation of these antiferromagnetic nanoparticles as a function of the magnetic field. We found that relaxation at T = 5 K in ferritin is faster in the absence of magnetic field, in good agreement with the zero-field Resonant Spin Quantum Tunneling observed previously in ferritin (Phys. Rev. Lett. 79, 1754 (1997).

Barco, E; Hernández, J M; Tejada, J

2002-01-01

241

Structure of magnetic field in Tokamaks  

International Nuclear Information System (INIS)

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.)

242

Trapped particle radiation in a magnetic field  

International Nuclear Information System (INIS)

The new type of radiation arising in case of particle acceleration in the longitudinal wave field and transverse magnetic field is investigated. Characteristics of spontaneous radiation are obtained and the influence of collective effects on radiation is considered

243

Plasma diffusion in weak magnetic field  

International Nuclear Information System (INIS)

It is planned to measure the diffusion constant of weakly ionized plasma in weak magnetic field. An introduction to elementary theory of particle motion in electromagnetic field is presented. (author)

244

The Evolution of the Earth's Magnetic Field.  

Science.gov (United States)

Describes the change of earth's magnetic field at the boundary between the outer core and the mantle. Measurement techniques used during the last 300 years are considered. Discusses the theories and research for explaining the field change. (YP)

Bloxham, Jeremy; Gubbins, David

1989-01-01

245

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

2012-02-01

246

Stochasticity from external magnetic field measurements  

International Nuclear Information System (INIS)

To determine whether or not magnetic field lines inside a tokamak plasma are stochastic the authors need the Fourier coefficients of any perturbing radial field inside the plasma. Usually what is measured with magnetic pick-up coils is the root mean square poloidal field outside the plasma. Although no unique transformation is available, they present a model which allows an interpretation of the measured (external) root mean square field in terms of the internal Fourier harmonics. The results are applied to particular TEXT discharges, and suggest a link between magnetic stochasticity and in increasing (more positive) radial electric field, as measured with a heavy ion beam probe

247

Hadrons in Strong Electric and Magnetic Fields  

OpenAIRE

We use chiral perturbation theory to investigate hadronic properties in strong electric and magnetic fields. A strong-field power counting is employed, and results for pions and nucleons are obtained using Schwinger's proper-time method. In the limit of weak fields, we accordingly recover the well known one-loop chiral perturbation theory results for the electric and magnetic polarizabilities of pions and nucleons. In strong constant fields, we extend the Gell-Mann-Oakes-Ren...

Tiburzi, Brian C.

2008-01-01

248

Multidipole magnetic fields for plasma confinement  

International Nuclear Information System (INIS)

Plasma confinement by permanent magnets has been studied. An analytic formula for the field of a single bar magnet has been obtained. Generalization to various configurations of multidipole fields has also been found. Any two-dimensional field may now be completely described by a simple function of complex variables in closed form. Vector potential has also been obtained by integrating over a prescribed Riemann surface. The confinement of plasma by multidipole fields then becomes obvious through conservation principles

249

Control of magnetism by electric fields.  

Science.gov (United States)

The electrical manipulation of magnetism and magnetic properties has been achieved across a number of different material systems. For example, applying an electric field to a ferromagnetic material through an insulator alters its charge-carrier population. In the case of thin films of ferromagnetic semiconductors, this change in carrier density in turn affects the magnetic exchange interaction and magnetic anisotropy; in ferromagnetic metals, it instead changes the Fermi level position at the interface that governs the magnetic anisotropy of the metal. In multiferroics, an applied electric field couples with the magnetization through electrical polarization. This Review summarizes the experimental progress made in the electrical manipulation of magnetization in such materials, discusses our current understanding of the mechanisms, and finally presents the future prospects of the field. PMID:25740132

Matsukura, Fumihiro; Tokura, Yoshinori; Ohno, Hideo

2015-03-01

250

Control of magnetism by electric fields  

Science.gov (United States)

The electrical manipulation of magnetism and magnetic properties has been achieved across a number of different material systems. For example, applying an electric field to a ferromagnetic material through an insulator alters its charge-carrier population. In the case of thin films of ferromagnetic semiconductors, this change in carrier density in turn affects the magnetic exchange interaction and magnetic anisotropy; in ferromagnetic metals, it instead changes the Fermi level position at the interface that governs the magnetic anisotropy of the metal. In multiferroics, an applied electric field couples with the magnetization through electrical polarization. This Review summarizes the experimental progress made in the electrical manipulation of magnetization in such materials, discusses our current understanding of the mechanisms, and finally presents the future prospects of the field.

Matsukura, Fumihiro; Tokura, Yoshinori; Ohno, Hideo

2015-03-01

251

Fluctuating magnetic field induced resonant activation  

Science.gov (United States)

In this paper, we have studied the properties of a Brownian particle at stationary state in the presence of a fluctuating magnetic field. Time dependence of the field makes the system thermodynamically open. As a signature of that the steady state distribution function becomes function of damping strength, intensity of fluctuations and constant parts of the applied magnetic field. It also depends on the correlation time of the fluctuating magnetic field. Our another observation is that the random magnetic field can induce the resonant activation phenomenon. Here correlation time is increased under the fixed variance of the fluctuating field. But if the correlation time (?) increases under the fixed field strength then the mean first passage time rapidly grows at low ? and it almost converges at other limit. This is sharp contrast to the usual colored noise driven open system case where the mean first passage time diverges exponentially. We have also observed that a giant enhancement of barrier crossing rate occurs particularly at large strength of constant parts of the applied magnetic field even for very weak fluctuating magnetic field. Finally, break down of the Arrhenius result and disappearance of the Kramers' turn over phenomenon may occur in the presence of a fluctuating magnetic field.

Mondal, Shrabani; Das, Sudip; Baura, Alendu; Bag, Bidhan Chandra

2014-12-01

252

Effects of magnetic field on cavitation damage  

International Nuclear Information System (INIS)

The cavitation and boiling phenomena in magnetic field are related to the nuclear reactors using liquid metal as the coolant, the electromagnetic pumps for liquid metal and electromagnetic flow meters. The condition of initially causing cavitation and the behavior of a single bubble in magnetic field have been studied, but the effect of magnetic field on the cavitation damage of materials in liquid metal has been scarecely examined. It was pointed out that the effect of magnetic field was observed also in the cavitation in low conductivity liquid such as water. In this study, in order to clarify the effect of magnetic field on cavitation damage, the cavitation damage test in tap water was carried out, applying uniform magnetic field by electrostrictive vibration. The specimens used were SUS 304 stainless steel and S 15 C carbon steel. The effect of magnetic field on the amount of damage and surface roughness was examined in the region from latent period through acceleration period to the former half of steady period. The experimental setup and experimental method and the results are reported. The cavitation damage in water was affected by magnetic field. (Kako, I.)

253

Magnetic Fields at the Center of Coils  

Science.gov (United States)

In this note we synthesize and extend expressions for the magnetic field at the center of very short and very long current-carrying coils. Elementary physics textbooks present the following equation for the magnetic field inside a very long current-carrying coil (solenoid): B[subscript sol] = µ[subscript 0] (N/L) I, (1) where I is the current, N…

Binder, Philippe; Hui, Kaleonui; Goldman, Jesse

2014-01-01

254

Structure of nuclei in strong magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

The structure of nuclei in ultrastrong magnetic fields relevant for supernovas and neutron stars is considered. The dependence of shell-correction energy on magnetic field is analyzed and systematized by employing the shell model with spherical harmonic oscillator confining potential. (author)

Kondratyev, V.N. [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

2002-06-01

255

Tracing Magnetic Fields with Ground State Alignment  

CERN Document Server

Observational studies of magnetic fields are vital as 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. We identified a process "ground state alignment" as a new way to determine the magnetic field direction in diffuse medium. The alignment is due to anisotropic radiation impinging on the atom/ion, while the magnetic field induces precession and realign the atom/ion and therefore the polarization of the emitted or absorbed radiation reflects the direction of the magnetic field. The atoms get aligned at their low levels and, as the life-time of the atoms/ions we deal with is long, the alignment induced by anisotropic radiation is susceptible to weak magnetic fields ($1{\\rm G}\\gtrsim B\\gtrsim 10^{-15}$G). Compared to the upper level Hanle effect, atomic realignment is most suitable for the studies of magnetic field in the diffuse medium, where magnetic field is relatively weak. In...

Yan, Huirong

2012-01-01

256

Magnetic Field Line Stickiness in Tokamaks  

CERN Document Server

We present simulated figures of the diverted magnetic field lines of the tokamak ITER, obtained by numerically integrating a Hamiltonian model with electrical currents in five wire loops and control coils. We show evidences of a sticky island embedded in the chaotic region near the divertor plates, which traps magnetic field lines for many toroidal turns increasing their connection lengths to these plates.

Martins, Caroline G L; Caldas, I L

2013-01-01

257

Levitation of a magnet by an alternating magnetic field  

Science.gov (United States)

An experiment is described in which a small strong cylindrical magnet is levitated by a vertical non-uniform alternating magnetic field. Surprisingly, no superimposed constant field is necessary, but the levitation can be explained when the vertical motion of the magnet is taken into account. The theoretical mean levitation force is (0.26 ± 0.06) N, which is in good agreement with the levitated weight of (0.239 ± 0.001) N. This experiment is suitable for an undergraduate laboratory, particularly as a final year project. Students have found it interesting, and it sharpens up knowledge of basic magnetism.

Gough, W.; Hunt, M. O.; Summerskill, W. S. H.

2013-01-01

258

Levitation of a magnet by an alternating magnetic field  

International Nuclear Information System (INIS)

An experiment is described in which a small strong cylindrical magnet is levitated by a vertical non-uniform alternating magnetic field. Surprisingly, no superimposed constant field is necessary, but the levitation can be explained when the vertical motion of the magnet is taken into account. The theoretical mean levitation force is (0.26 ± 0.06) N, which is in good agreement with the levitated weight of (0.239 ± 0.001) N. This experiment is suitable for an undergraduate laboratory, particularly as a final year project. Students have found it interesting, and it sharpens up knowledge of basic magnetism. (paper)

259

Closed strings in uniform magnetic field backgrounds  

OpenAIRE

We consider a class of conformal models describing closed strings in axially symmetric stationary magnetic flux tube backgrounds. These models are closed string analogs of the Landau model of a particle in a magnetic field or the model of an open string in a constant magnetic field. They are interesting examples of solvable unitary conformal string theories with non-trivial 4-dimensional curved space-time interpretation. In particular, their quantum Hamiltonian can be expres...

Tseytlin, A. A.

1995-01-01

260

Magnetic field relaxation in ferromagnetic Ising systems  

OpenAIRE

We analyze the thermal magnetization reversal processes in magnetic grains. Two experiments are carried out: swtiching time and switching field experiments. In both cases, we find that the simulated behavior is coherent with existing experimental data (the streched exponent of the switching time experiment increases with the temperature and is superior to unity; there exists a master curve for the switching field experiment). Moreover, we simulated magnetic grains in a regio...

Me?lin, R.

1996-01-01

261

Large-scale magnetic fields in cosmology  

CERN Document Server

Despite the widespread presence of magnetic fields, their origin, evolution and role are still not well understood. Primordial magnetism sounds appealing but is not problem free. The magnetic implications for the large-scale structure of the universe still remain an open issue. This paper outlines the advantages and shortcomings of early-time magnetogenesis and the typical role of B-fields in linear structure-formation scenarios.

Tsagas, Christos G

2009-01-01

262

Computation of magnetic field in an actuator  

OpenAIRE

Design and optimization of an actuators based on magnetostrictive technology requires computation of the magnetic field. The “MS”-technology offers an attractive controllability with high power density. The magnetostriction is a reversible feature which can be used in various actuator layouts. The actuator performance depends on driving magnetic field and the particular magnetic properties of used materials. Good understanding of specific design constrains is required to define and to op...

Olabi, Abdul; Grunwald, Artur

2008-01-01

263

Quantum Electrodynamics in a Uniform Magnetic Field  

OpenAIRE

A systematic formalism for quantum electrodynamics in a classical uniform magnetic field is discussed. The first order radiative correction to the ground state energy of an electron is calculated. This then leads to the anomalous magnetic moment of an electron without divergent integrals. Thorough analyses of this problem are given for the weak magnetic field limit. A new expression for the radiative correction to the ground state energy is obtained. This contains only one i...

Suzuki, Jun

2005-01-01

264

Sonoluminescence Coupling to an Applied Magnetic Field  

CERN Document Server

We investigate several means of coupling between a sonoluminescing bubble and an applied magnetic field. Recent experiments show a strong quadratic dependence between the forcing pressures required for stable sonoluminescence and magnetic field amplitude. However, all coupling mechanisms calculated here are at most one percent perturbations. The most likely explanation is a sensitive hydrodynamic effect linked to a relatively small but characteristically inhomogeneous magnetically induced pressure on the bubble wall. We suggest experiments to test this effect.

Di Donna, B A; Young, J B

1997-01-01

265

Classical theory of electric and magnetic fields  

CERN Document Server

Classical Theory of Electric and Magnetic Fields is a textbook on the principles of electricity and magnetism. This book discusses mathematical techniques, calculations, with examples of physical reasoning, that are generally applied in theoretical physics. This text reviews the classical theory of electric and magnetic fields, Maxwell's Equations, Lorentz Force, and Faraday's Law of Induction. The book also focuses on electrostatics and the general methods for solving electrostatic problems concerning images, inversion, complex variable, or separation of variables. The text also explains ma

Good, Roland H

1971-01-01

266

Field-induced magnetism in actinide systems  

International Nuclear Information System (INIS)

We demonstrate that the field-induced spin and orbital moments in paramagnetic metals in general are parallel, regardless of the filling of the electronic shell. The early actinides, however, approach the border where the moments go antiparallel. This results in peculiar magnetic states for ?-Pu and some uranium compounds, where the spin moments are antiparallel to the applied field and the magnetic response is dominated by the orbital contribution, and consequently these systems display unusual spin densities and magnetic form factors. ((orig.))

267

Magnetic Helicity and Large Scale Magnetic Fields: A Primer  

Science.gov (United States)

Magnetic fields of laboratory, planetary, stellar, and galactic plasmas commonly exhibit significant order on large temporal or spatial scales compared to the otherwise random motions within the hosting system. Such ordered fields can be measured in the case of planets, stars, and galaxies, or inferred indirectly by the action of their dynamical influence, such as jets. Whether large scale fields are amplified in situ or a remnant from previous stages of an object's history is often debated for objects without a definitive magnetic activity cycle. Magnetic helicity, a measure of twist and linkage of magnetic field lines, is a unifying tool for understanding large scale field evolution for both mechanisms of origin. Its importance stems from its two basic properties: (1) magnetic helicity is typically better conserved than magnetic energy; and (2) the magnetic energy associated with a fixed amount of magnetic helicity is minimized when the system relaxes this helical structure to the largest scale available. Here I discuss how magnetic helicity has come to help us understand the saturation of and sustenance of large scale dynamos, the need for either local or global helicity fluxes to avoid dynamo quenching, and the associated observational consequences. I also discuss how magnetic helicity acts as a hindrance to turbulent diffusion of large scale fields, and thus a helper for fossil remnant large scale field origin models in some contexts. I briefly discuss the connection between large scale fields and accretion disk theory as well. The goal here is to provide a conceptual primer to help the reader efficiently penetrate the literature.

Blackman, Eric G.

2014-04-01

268

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

269

Origin of Galactic and Extragalactic Magnetic Fields  

CERN Document Server

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

270

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

271

Comparison of adjustable permanent magnetic field sources  

International Nuclear Information System (INIS)

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.

272

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

273

Comparison of adjustable permanent magnetic field sources  

CERN Document Server

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 agreement is found.

Bjørk, R; Smith, A; Pryds, N

2014-01-01

274

The Magnetic Field in the Solar Atmosphere  

CERN Document Server

This publication provides an overview of magnetic fields in the solar atmosphere with the focus lying on the corona. The solar magnetic field couples the solar interior with the visible surface of the Sun and with its atmosphere. It is also responsible for all solar activity in its numerous manifestations. Thus, dynamic phenomena such as coronal mass ejections and flares are magnetically driven. In addition, the field also plays a crucial role in heating the solar chromosphere and corona as well as in accelerating the solar wind. Our main emphasis is the magnetic field in the upper solar atmosphere so that photospheric and chromospheric magnetic structures are mainly discussed where relevant for higher solar layers. Also, the discussion of the solar atmosphere and activity is limited to those topics of direct relevance to the magnetic field. After giving a brief overview about the solar magnetic field in general and its global structure, we discuss in more detail the magnetic field in active regions, the quie...

Wiegelmann, Thomas; Solanki, Sami K

2014-01-01

275

Physics in Very Strong Magnetic Fields  

Science.gov (United States)

This paper provides an introduction to a number of astrophysics problems related to strong magnetic fields. The first part deals with issues related to atoms, condensed matter and high-energy processes in very strong magnetic fields, and how these issues influence various aspects of neutron star astrophysics. The second part deals with classical astrophysical effects of magnetic fields: Even relatively "weak" fields can play a strong role in various astrophysical problems, ranging from stars, accretion disks and outflows, to the formation and merger of compact objects.

Lai, Dong

2015-02-01

276

Warm inflation in presence of magnetic fields  

CERN Document Server

We present preliminary results on the possible effects that primordial magnetic fields can have for a warm inflation scenario, based on global supersymmetry, with a new-inflation-type potential. This work is motivated by two considerations: first, magnetic fields seem to be present in the universe on all scales, which rises the possibility that they could also permeate the early universe; second, the recent emergence of inflationary models where the inflaton is not assumed to be isolated but instead it is taken as an interacting field, even during the inflationary expansion. The effects of magnetic fields are included resorting to Schwinger proper time method.

Piccinelli, Gabriella; Ayala, Alejandro; Mizher, Ana Julia

2013-01-01

277

Warm inflation in presence of magnetic fields  

International Nuclear Information System (INIS)

We present preliminary results on the possible effects that primordial magnetic fields can have for a warm inflation scenario, based on global supersymmetry, with a new-inflation-type potential. This work is motivated by two considerations: first, magnetic fields seem to be present in the universe on all scales which rises de possibility that they could also permeate the early universe; second, the recent emergence of inflationary models where the inflaton is not assumed to be isolated but instead it is taken as an interacting field, even during the inflationary expansion. The effects of magnetic fields are included resorting to Schwinger's proper time method

278

Ohm's law for mean magnetic fields  

International Nuclear Information System (INIS)

Spatially complicated magnetic fields are frequently treated as the sum of a large, slowly varying, mean field and a small, rapidly varying, field. The primary effect of the small field is to modify the Ohm's law of the mean field. A set of plausible assumptions leads to a form of the mean field Ohm's law which is fundamentally different from the conventional alpha effect of dynamo theory

279

Hypernuclear matter in strong magnetic field  

Energy Technology Data Exchange (ETDEWEB)

Compact stars with strong magnetic fields (magnetars) have been observationally determined to have surface magnetic fields of order of 10{sup 14}–10{sup 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?10{sup 17} G, in particular the matter properties become anisotropic. Moreover, for the central fields B?10{sup 18} G, the magnetized hypernuclear matter shows instability, which is signalled by the negative sign of the derivative of the pressure parallel to the field with respect to the density, and leads to vanishing parallel pressure at the critical value B{sub cr}?10{sup 19} G. This limits the range of admissible homogeneously distributed fields in magnetars to fields below the critical value B{sub cr}.

Sinha, Monika [Institute for Theoretical Physics, J.W. Goethe-University, D-60438 Frankfurt am Main (Germany); Indian Institute of Technology Rajasthan, Old Residency Road, Ratanada, Jodhpur 342011 (India); Mukhopadhyay, Banibrata [Department of Physics, Indian Institute of Science, Bangalore 560012 (India); Sedrakian, Armen, E-mail: sedrakian@th.physik.uni-frankfurt.de [Institute for Theoretical Physics, J.W. Goethe-University, D-60438 Frankfurt am Main (Germany)

2013-01-17

280

Field Mapping System for Solenoid Magnet  

Science.gov (United States)

A three-dimensional Hall probe mapping system for measuring the solenoid magnet of PLS photo-cathode RF e-gun has been developed. It can map the solenoid field either in Cartesian or in cylindrical coordinate system with a measurement reproducibility better than 5 × 10-5 T. The system has three axis motors: one for the azimuthal direction and the other two for the x and z direction. This architecture makes the measuring system simple in fabrication. The magnetic center was calculated using the measured axial component of magnetic field Bz in Cartesian coordinate system because the accuracy of magnetic axis measurement could be improved significantly by using Bz, instead of the radial component of magnetic field Br. This paper describes the measurement system and summarizes the measurement results for the solenoid magnetic of PLS photo-cathode RF e-gun.

Park, K. H.; Jung, Y. K.; Kim, D. E.; Lee, H. G.; Park, S. J.; Chung, C. W.; Kang, B. K.

2007-01-01

281

Solar Force-free Magnetic Fields  

CERN Document Server

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

282

Magnetic-field-controlled reconfigurable semiconductor logic.  

Science.gov (United States)

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

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

2013-02-01

283

Classical dynamics in a random magnetic field  

International Nuclear Information System (INIS)

The classical dynamics in a quenched random magnetic field is investigated using both the Langevin and Boltzmann equations. In the former case, a field-theoretic method permits the average over the random magnetic field to be performed exactly. A self-consistent theory is constructed using the functional method for the effective action, allowing a determination of the particle response to external forces. In the Boltzmann approach the random magnetic field is treated as a random Lorentz driving force. Langevin dynamics always leads to negative magnetoresistance, whereas the Boltzmann description can lead to either positive or negative magnetoresistance. In both descriptions the resistivity decreases at low average magnetic fields as the temperature increases. In contrast to the Langevin result, the Boltzmann resistivity increases at moderate fields as a function of temperature, displaying a nonmonotonic temperature dependence. The transverse resistivity decreases as the temperature increases in the case of Langevin dynamics, whereas the opposite behavior occurs in the Boltzmann case

284

Magnetic monopole field exposed by electrons  

CERN Document Server

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

285

Protein detection with magnetic nanoparticles in a rotating magnetic field  

Science.gov (United States)

A detection scheme based on magnetic nanoparticle (MNP) dynamics in a rotating magnetic field for a quantitative and easy-to-perform detection of proteins is illustrated. For the measurements, a fluxgate-based setup was applied, which measures the MNP dynamics, while a rotating magnetic field is generated. The MNPs exhibit single iron oxide cores of 25 nm and 40 nm diameter, respectively, as well as a protein G functionalized shell. IgG antibodies were utilized as binding target molecules for the physical proof-of-concept. The measurement results were fitted with a theoretical model describing the magnetization dynamics in a rotating magnetic field. The established detection scheme allows quantitative determination of proteins even at a concentration lower than of the particles. The observed differences between the two MNP types are discussed on the basis of logistic functions.

Dieckhoff, Jan; Lak, Aidin; Schilling, Meinhard; Ludwig, Frank

2014-01-01

286

External-field-free magnetic biosensor  

Energy Technology Data Exchange (ETDEWEB)

In this paper, we report a magnetic nanoparticle (MNP) detection scheme without the presence of any external magnetic field. The proposed magnetic sensor uses a patterned groove structure within the sensor so that no external magnetic field is needed to magnetize the MNPs. An example is given based on a giant magnetoresistance (GMR) sensing device with a spin valve structure. For this structure, the detection of MNPs located inside the groove and near the free layer is demonstrated under no external magnetic field. Micromagnetic simulations are performed to calculate the signal to noise level of this detection scheme. A maximum signal to noise ratio (SNR) of 18.6?dB from one iron oxide magnetic nanoparticle with 8?nm radius is achieved. As proof of concept, this external-field-free GMR sensor with groove structure of 200?nm?×?200?nm is fabricated using a photo and an electron beam integrated lithography process. Using this sensor, the feasibility demonstration of the detection SNR of 9.3?dB is achieved for 30??l magnetic nanoparticles suspension (30?nm iron oxide particles, 1?mg/ml). This proposed external-field-free sensor structure is not limited to GMR devices and could be applicable to other magnetic biosensing devices.

Li, Yuanpeng; Wang, Yi; Klein, Todd; Wang, Jian-Ping, E-mail: jpwang@umn.edu [Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2014-03-24

287

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

OpenAIRE

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. ...

Isakov, S. V.; Raman, K. S.; Moessner, R.; Sondhi, S. L.

2004-01-01

288

Energy of magnetic moment of superconducting current in magnetic field  

OpenAIRE

The energy of magnetic moment of the persistent current circulating in superconducting loop in an externally produced magnetic field is not taken into account in the theory of quantization effects because of identification of the Hamiltonian with the energy. This identification misleads if, in accordance with the conservation law, the energy of a state is the energy expended for its creation. The energy of magnetic moment is deduced from a creation history of the current sta...

Gurtovoi, V. L.; Nikulov, A. V.

2014-01-01

289

Magnetic field measurements on small magnets by vibrating wire systems  

CERN Document Server

A new method based on vibrating wire to measure field multipole is presented. The magnet multipoles are assessed by positioning the wire in different points on a circle inside the magnet aperture and measuring the amplitude of wire vibrations. An analytical model relates vibration amplitudes to multipoles. Results of simulation tests aimed at analyzing the model performance are reported. Preliminary experimental validation results on small permanent magnets for the new linear accelerator Linac4 at European Organization for Nuclear Research (CERN) are shown.

Arpaia, P; Garcia Perez, Juan Jose; Golluccio, G; Petrone, C; Walckiers, Louis

2011-01-01

290

Compact low field magnetic resonance imaging magnet: Design and optimization  

Science.gov (United States)

Magnetic resonance imaging (MRI) is performed with a very large instrument that allows the patient to be inserted into a region of uniform magnetic field. The field is generated either by an electromagnet (resistive or superconductive) or by a permanent magnet. Electromagnets are designed as air cored solenoids of cylindrical symmetry, with an inner bore of 80-100 cm in diameter. In clinical analysis of peripheral regions of the body (legs, arms, foot, knee, etc.) it would be better to adopt much less expensive magnets leaving the most expensive instruments to applications that require the insertion of the patient in the magnet (head, thorax, abdomen, etc.). These "dedicated" apparati could be smaller and based on resistive magnets that are manufactured and operated at very low cost, particularly if they utilize an iron yoke to reduce power requirements. In order to obtain good field uniformity without the use of a set of shimming coils, we propose both particular construction of a dedicated magnet, using four independently controlled pairs of coils, and an optimization-based strategy for computing, a posteriori, the optimal current values. The optimization phase could be viewed as a low-cost shimming procedure for obtaining the desired magnetic field configuration. Some experimental measurements, confirming the effectiveness of the proposed approach (construction and optimization), have also been reported. In particular, it has been shown that the adoption of the proposed optimization based strategy has allowed the achievement of good uniformity of the magnetic field in about one fourth of the magnet length and about one half of its bore. On the basis of the good experimental results, the dedicated magnet can be used for MRI of peripheral regions of the body and for animal experimentation at very low cost.

Sciandrone, M.; Placidi, G.; Testa, L.; Sotgiu, A.

2000-03-01

291

Ohm's law for mean magnetic fields  

International Nuclear Information System (INIS)

The magnetic fields associated with plasmas frequently exhibit small-amplitude MHD fluctuations. It is useful to have equations for the magnetic field averaged over these fluctuations, the so-called mean field equations. Under very general assumptions, it is shown that the effect of MHD fluctuations on a force-free plasma can be represented by one parameter in Ohm's law, which is effectively the coefficient of electric current viscosity. (author)

292

Ohm's law for mean magnetic fields  

International Nuclear Information System (INIS)

The magnetic fields associated with plasmas frequently exhibit small amplitude MHD fluctuations. It is useful to have equations for the magnetic field averaged over these fluctuations, the so-called mean field equations. Under very general assumptions it is shown that the effect of MHD fluctuations on a force-free plasma can be represented by one parameter in Ohm's law, which is effectively the coefficient of electric current viscosity

293

Manifestations of the Galactic Center Magnetic Field  

OpenAIRE

Several independent lines of evidence reveal that a relatively strong and highly ordered magnetic field is present throughout the Galaxy's central molecular zone (CMZ). The field within dense clouds of the central molecular zone is predominantly parallel to the Galactic plane, probably as a result of the strong tidal shear in that region. A second magnetic field system is present outside of clouds, manifested primarily by a population of vertical, synchrotron-emitting filame...

Morris, Mark R.

2014-01-01

294

Magnetic field homogeneity perturbations in finite Halbach dipole magnets  

Science.gov (United States)

Halbach hollow cylinder dipole magnets of a low or relatively low aspect ratio attract considerable attention due to their applications, among others, in compact NMR and MRI systems for investigating small objects. However, a complete mathematical framework for the analysis of magnetic fields in these magnets has been developed only for their infinitely long precursors. In such a case the analysis is reduced to two-dimensions (2D). The paper details the analysis of the 3D magnetic field in the Halbach dipole cylinders of a finite length. The analysis is based on three equations in which the components of the magnetic flux density Bx, By and Bz are expanded to infinite power series of the radial coordinate r. The zeroth term in the series corresponds to a homogeneous magnetic field Bc, which is perturbed by the higher order terms due to a finite magnet length. This set of equations is supplemented with an equation for the field profile B(z) along the magnet axis, presented for the first time. It is demonstrated that the geometrical factors in the coefficients of particular powers of r, defined by intricate integrals are the coefficients of the Taylor expansion of the homogeneity profile (B(z) - Bc)/Bc. As a consequence, the components of B can be easily calculated with an arbitrary accuracy. In order to describe perturbations of the field due to segmentation, two additional equations are borrowed from the 2D theory. It is shown that the 2D approach to the perturbations generated by the segmentation can be applied to the 3D Halbach structures unless r is not too close to the inner radius of the cylinder ri. The mathematical framework presented in the paper was verified with great precision by computations of B by a highly accurate integration of the magnetostatic Coulomb law and utilized to analyze the inhomogeneity of the magnetic field in the magnet with the accuracy better than 1 ppm.

Turek, Krzysztof; Liszkowski, Piotr

2014-01-01

295

Field mapping system for cyclotron magnet  

International Nuclear Information System (INIS)

This paper presents a Hall probe mapping system for measuring a cyclotron magnet, which has been fabricated for the 13 MeV cyclotron at the Korea Institute of Radiological and Medical Sciences. Two Hall probes are mounted on a precision mechanical x-y stage and map magnetic field in the Cartesian coordinate system. The mapping system uses the 'flying' mode field mapping method to reduce data-acquisition time. The time required for mapping the whole gap-area of the cyclotron magnet is ?60 min. The relative measurement error for the averaged magnetic field along beam orbit is less than 0.02%. The cyclotron magnet has been corrected using field measurement data, and the achieved total phase excursion of the cyclotron after correction is less than ±15 deg , which is within the tolerance of ±20 deg for the total phase excursion

296

Hadronic instabilities in very intense magnetic fields  

International Nuclear Information System (INIS)

Composite hadronic states exhibit interesting properties in the presence of very intense magnetic fields, such as those conjectured to exist in the vicinity of certain astrophysical objects. We discuss three scenarios. (i) The presence of vector particles with anomalous magnetic moment couplings to scalar particles, induces an instability of the vacuum. (ii) A delicate interplay between the anomalous magnetic moments of the proton and neutron makes, in magnetic fields B?2x1014 T, the neutron stable and for fields B?5x1014 T, the proton becomes unstable to a decay into a neutron via ? emission. (iii) In the unbroken chiral ? model magnetic fields would be screened out as in a superconductor. It is the explicit breaking of chiral invariance that restores standard electrodynamics. Astrophysical consequences of all these phenomena are discussed

297

New Magnetic phases of holmium in a magnetic field  

International Nuclear Information System (INIS)

We have examined the behavior of two well-characterized single crystals of holmium in a magnetic field applied along the c axis in a temperature range from 90 to 140 K, using magnetization and dilatometric measurements. We have found several new phases in this previously unexplored region of the phase diagram

298

Demagnetizing fields in active magnetic regenerators  

DEFF Research Database (Denmark)

A magnetic material in an externally applied magnetic field will in general experience a spatially varying internal magnetic field due to demagnetizing effects. When the performance of active magnetic regenerators (AMRs) is evaluated using numerical models the internal field is often assumed to be spatially constant and equal to the applied field, thus neglecting the demagnetizing field. Furthermore, the experimental magnetocaloric properties used (adiabatic temperature change, isothermal entropy change and specific heat) are often not corrected for demagnetization. The demagnetizing field in an AMR is in general both a function of the overall shape of the regenerator and its morphology (packed particles, parallel plates etc.) as well as the magnetization of the material. Due to the pronounced temperature dependence of the magnetization near the Curie temperature, the demagnetization field is also temperature dependent. We propose a relatively straightforward method to correct sufficiently for the demagnetizing field in AMR models. We discuss how the demagnetizing field behaves in regenerators made of packed spheres under realistic operation conditions.

Bahl, Christian R.H.

2014-01-01

299

Neutron Star Crust in Strong Magnetic Fields  

International Nuclear Information System (INIS)

We discuss the effects of strong magnetic fields through Landau quantization of electrons on the structure and stability of nuclei in neutron star crust. In strong magnetic fields, this leads to the enhancement of the electron number density with respect to the zero field case. We obtain the sequence of equilibrium nuclei of the outer crust in the presence of strong magnetic fields adopting most recent versions of the experimental and theoretical nuclear mass tables. For B ? 1016G, it is found that some new nuclei appear in the sequence and some nuclei disappear from the sequence compared with the zero field case. Further we investigate the stability of nuclei in the inner crust in the presence of strong magnetic fields using the Thomas-Fermi model. The coexistence of two phases of nuclear matter - liquid and gas, is considered in this case. The proton number density is significantly enhanced in strong magnetic fields B ? 1017G through the charge neutrality. We find nuclei with larger mass number in the presence of strong magnetic fields than those of the zero field. These results might have important implications for the transport properties of the crust in magnetars.

300

3D analysis of applied field effect on trapped magnetic field during pulsed field magnetization of bulk superconductor  

Science.gov (United States)

External applied field effect in magnetization process by pulsed field (PFM) method of rectangular bulk superconductor is analysed by solving the A-V magnetic equation coupled to the thermal one in order to show the influence of the amplitude of the external field on the trapped magnetic field of bulk superconductor. A numerical model based on the control volume method (CVM) has been developed, which uses a power-law model with temperature dependency and magnetic field dependence on critical current density. For low cooling temperature Tco = 20 K, a good distribution of the trapped magnetic field of the bulk superconductor is obtained when we applied high external field.

Lotfi Khene, Mohamed; Alloui, Lotfi; Mimoune, Souri Mohamed; Bouillault, Frédéric; Feliachi, Mouloud

2014-04-01

301

Magnetic fields on resistance spaces  

OpenAIRE

On a metric measure space $X$ that supports a regular, strongly local resistance form we consider a magnetic energy form that corresponds to the magnetic Laplacian for a particle confined to $X$. We provide sufficient conditions for closability and essential self-adjointness in terms of geometric conditions on the reference measure without assuming energy dominance.

Hinz, Michael; Rogers, Luke

2015-01-01

302

Magnetic field considerations in fusion power plant environs  

International Nuclear Information System (INIS)

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

303

Equilibrium magnetization of a nanogranular magnetic film with perpendicular anisotropy in a tilted magnetic field  

International Nuclear Information System (INIS)

The influence of demagnetization field on the process of equilibrium magnetization of a nanogranular magnetic film with perpendicular anisotropy in a tilted magnetic field is studied theoretically. Both the canting and the overturning of granules magnetic moments are taken into account and the effect of each of these processes on the magnetization curves is described. It is shown, that transition from the magnetization state with nonuniform orientation of the granule magnetic moments to a homogeneous one in a tilted field occurs in the critical way.

304

Evolution of the interplanetary magnetic field  

Energy Technology Data Exchange (ETDEWEB)

Remote observations of magnetic field topologies in the solar corona and in situ observations of the solar wind and interplanetary magnetic field (IMF) in interplanetary space are used to examine the temporal evolution of the spatial distribution of open and closed field regions emanating from the Sun. The simple ``open`` configuration of inward and outward pointing sectors in the IMF is periodically disrupted by magnetically distinct coronal mass ejections (CMEs) which erupt from previously closed magnetic field regions in the corona into interplanetary space. At 1 AU, CMEs contain counterstreaming halo electrons which indicate their distinct magnetic topologies. This topology is generally thought to be: plasmoids that are completely disconnected from the Sun; magnetic ``bottles,`` still tied to the corona at both ends; or flux ropes which are only partially disconnected. Fully disconnected plasmoids would have no long term effect on the amount of open flux; however, both in situ observations of details of the halo electron distributions and remote coronagraph observations of radial fields following CMEs indicate that CMEs generally do retain at least partial attached to the Sun. Both the magnetic-bottle and flux rope geometries require some mitigating process to close off previously open fields in order to avoid a flux catastrophe. In addition, the average amount of magnetic flux observed in interplanetary space varies over the solar cycle, also indicating that there must be ways in which new flux is opened and previously open flux is closed off. The most likely scenario for closing off open magnetic fields is for reconnection to occurs above helmet streamers, where oppositely directed field regions are juxtaposed in the corona. These events would serve to return closed field arches to the Sun and release open, U-shaped structures into the solar wind.

McComas, D.J.

1993-05-01

305

Evolution of the interplanetary magnetic field  

Energy Technology Data Exchange (ETDEWEB)

Remote observations of magnetic field topologies in the solar corona and in situ observations of the solar wind and interplanetary magnetic field (IMF) in interplanetary space are used to examine the temporal evolution of the spatial distribution of open and closed field regions emanating from the Sun. The simple open'' configuration of inward and outward pointing sectors in the IMF is periodically disrupted by magnetically distinct coronal mass ejections (CMEs) which erupt from previously closed magnetic field regions in the corona into interplanetary space. At 1 AU, CMEs contain counterstreaming halo electrons which indicate their distinct magnetic topologies. This topology is generally thought to be: plasmoids that are completely disconnected from the Sun; magnetic bottles,'' still tied to the corona at both ends; or flux ropes which are only partially disconnected. Fully disconnected plasmoids would have no long term effect on the amount of open flux; however, both in situ observations of details of the halo electron distributions and remote coronagraph observations of radial fields following CMEs indicate that CMEs generally do retain at least partial attached to the Sun. Both the magnetic-bottle and flux rope geometries require some mitigating process to close off previously open fields in order to avoid a flux catastrophe. In addition, the average amount of magnetic flux observed in interplanetary space varies over the solar cycle, also indicating that there must be ways in which new flux is opened and previously open flux is closed off. The most likely scenario for closing off open magnetic fields is for reconnection to occurs above helmet streamers, where oppositely directed field regions are juxtaposed in the corona. These events would serve to return closed field arches to the Sun and release open, U-shaped structures into the solar wind.

McComas, D.J.

1993-01-01

306

Normal glow discharge in axial magnetic field  

Science.gov (United States)

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

Surzhikov, S.; Shang, J.

2014-10-01

307

Magnetic fields from heterotic cosmic strings  

International Nuclear Information System (INIS)

Large-scale magnetic fields are observed today to be coherent on galactic scales. While there exists an explanation for their amplification and their specific configuration in spiral galaxies--the dynamo mechanism--a satisfying explanation for the original seed fields required is still lacking. Cosmic strings are compelling candidates because of their scaling properties, which would guarantee the coherence on cosmological scales of any resultant magnetic fields at the time of galaxy formation. We present a mechanism for the production of primordial seed magnetic fields from heterotic cosmic strings arising from M theory. More specifically, we make use of heterotic cosmic strings stemming from M5-branes wrapped around four of the compact internal dimensions. These objects are stable on cosmological time scales and carry charged zero modes. Therefore a scaling solution of such defects will generate seed magnetic fields which are coherent on galactic scales today.

308

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

CERN Document Server

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

309

Dynamo Activity In Imposed DC Magnetic Fields  

International Nuclear Information System (INIS)

A widely accepted mechanism for the spontaneous appearance of large-scale magnetic fields in magnetofluids is the turbulent inverse cascade of magnetic helicity. The evidence for the effect is largely computational, and has been acquired by using spectral-method codes and imposing three-dimensional (3D) rectangular periodic boundary conditions. We report here similar investigations of the phenomenon that result when a uniform external dc magnetic field is present. With no imposed dc magnetic field, the 1981 results of Meneguzzi et al are recovered, but by adding an externally-imposed dc magnetic field, we find that it is possible to suppress entirely the inverse magnetic helicity cascade phenomenon. This is a somewhat puzzling result, and we attribute it not to any fundamental change in the physical processes involved as much as to the inconsistency of 3D rectangular periodic boundary conditions (which permit no net current through the basic computational box). These boundary conditions seem inadequate as a representation of the nonlinear dynamics of helically-driven MHD in the presence of a dc magnetic field (which encourage such a dc net current to flow). We believe that if the turbulent computations were to be repeated with more realistic geometry and boundary conditions (e.g., toroids, disks, or periodic cylinders), the inverse magnetic helicity cascade phenomenon would reappear. But at the moment, this must be regarded as an open question an open question

310

ICRH experiments in a toroidal octupole  

International Nuclear Information System (INIS)

A 100 kW, 144 ?sec pulse of 1.4 MHz rf is used to heat plasmas with densities less than or equal to 3 x 1012 cm-3 at the ion cyclotron frequency in a toroidal octupole. The rf is coupled to the plasma by a single turn, electrostatically shielded hoop coaxial to the four main hoops and located near the wall. Absorbed power is inferred from plasma loading of the hoop and measured directly with an electrostatic ion energy analyzer and compared to single particle resonance heating theory

311

Surface magnetic field effects in local helioseismology  

CERN Document Server

Using helioseismic holography strong evidence is presented that the phase (or equivalent travel-time) of helioseismic signatures in Dopplergrams within sunspots depend upon the line-of-sight angle in the plane containing the magnetic field and vertical directions. This is shown for the velocity signal in the penumbrae of two sunspots at 3, 4 and 5 mHz. Phase-sensitive holography demonstrates that they are significantly affected in a strong, moderately inclined magnetic field. This research indicates that the effects of the surface magnetic field are potentially very significant for local helioseismic analysis of active regions.

Schunker, H; Cally, P S; 10.1002/asna.200610732

2010-01-01

312

Investigation of the Galaxy magnetic field  

International Nuclear Information System (INIS)

Rotation measurements of 703 radio sources are used for the study of the structure of the Galaxy magnetic field. It is shown that the large scale magnetic field of the Galaxy is directed approximately parallel to the local spiral arm and has an opposite direction in the regions 15 deg 200 rad/m2) and located in the region -15 deg < b < 15 deg probably are Galaxy H2 regions. The parameters of the magnetic fields of these objects approximately coincide with the parameters of the surrounding medium

313

Magnetic Field Dependent Tunneling in Glasses  

CERN Document Server

We report on experiments giving evidence for quantum effects of electromagnetic flux in barium alumosilicate glass. In contrast to expectation, below 100 mK the dielectric response becomes sensitive to magnetic fields. The experimental findings include both, the complete lifting of the dielectric saturation by weak magnetic fields and oscillations of the dielectric response in the low temperature resonant regime. As origin of these effects we suggest that the magnetic induction field violates the time reversal invariance leading to a flux periodicity in the energy levels of tunneling systems. At low temperatures, this effect is strongly enhanced by the interaction between tunneling systems and thus becomes measurable.

Strehlow, P; Janssen, A J M; Haueisen, R; Weiss, G L; Enss, C; Hunklinger, S

2000-01-01

314

Dispersion of Magnetic Fields in Molecular Clouds  

CERN Document Server

We describe a method for determining the dispersion of magnetic field vectors about local mean fields in turbulent molecular clouds. The method is designed to avoid inaccurate estimates of MHD or turbulent dispersion - and hence to avoid inaccurate estimates of field strengths - due to large-scale, non-turbulent field structure when using the well-known method of Chandrasekhar and Fermi. Our method also provides accurate, independent estimates of the turbulent to mean magnetic field strength ratio. We discuss applications to the molecular clouds Orion, M17, and DR21.

Hildebrand, Roger H; Dotson, Jessie L; Houde, Martin; Vaillancourt, John E

2008-01-01

315

Residential ground system currents and magnetic fields  

International Nuclear Information System (INIS)

Full text: Measurements of ground currents and magnetic fields have been made in fourteen houses. The measurements indicated that a ground system can be a source of magnetic fields in these houses. In some houses the fields inside sometimes exceeded the fields due to the external power lines alone. In four houses the current in the grounding system was zero, nevertheless these houses were exposed to fields produced by power lines. In some houses a close relationship existed between the measured ground currents at the water meters and the ground system fields inside those houses. The largest value of average ground current was 5.37 A. Contour and surface plots of magnetic fields showed that water pipes influenced the spatial distribution of the magnetic field inside houses. In two houses the external ground current sometimes exceeded the load current of those houses. This is a most unexpected finding. In houses where no ground currents occurred, the value of the magnetic field at the centre of each room was found to be a good approximation to the average of the field throughout that room

316

The theory of the Galactic magnetic field  

Science.gov (United States)

The paper discusses the role of the magnetic field in determining the large scale structure and dynamics of the interstellar medium. It then discusses the origin and maintenance of the Galactic field. The two major competing theories are that the field is primordial and connected to an intergalactic field or that the field is removed from and regenerated within the Galaxy. Finally, cosmic ray acceleration and confinement in the interstellar medium are discussed.

Zweibel, Ellen G.

1987-01-01

317

Field quality of LHC superconducting dipole magnets  

International Nuclear Information System (INIS)

The author reports here the main results of field measurements performed so far on the LHC superconducting dipoles at superfluid helium temperature. The main field strength at injection, collision conditions and higher order multipoles are discussed. Superconducting magnets exhibit additional field imperfections due to diamagnetic properties of superconducting cables, apart from geometric error, saturation of iron yoke and eddy currents error. Dynamic effects on field harmonics, such as field decay at injection and subsequent snap back are also discussed. (author)

318

Tracing Magnetic Fields by Atomic Alignment in Extended Radiation Fields  

CERN Document Server

Tracing magnetic fields is crucial as magnetic fields play an important role in many astrophysical processes. Earlier studies have demonstrated that Ground State Alignment (GSA) is a unique way to detect weak magnetic fields (1G> B> 1exp(-15)G) in diffuse media, they consider the situation when the pumping source is a point source, which applies when the star is very far away from the diffuse media. In this paper, we explore the GSA in the presence of extended radiation fields. For the radiation fields with a clear geometric structure, we consider the alignment in circumstellar medium, binary systems, disc, and Local Interstellar Medium (LISM). For the radiation fields with unidentified pumping sources, we apply the method of multipole expansion and discuss the GSA induced by each component. We demonstrate that for general radiation fields, it is adequate to consider the contribution from dipole and quadrupole radiation components. We find that in general polarization of absorption arizing from GSA coincides ...

Zhang, Heshou; Dong, Le

2014-01-01

319

The rotation-magnetic field relation  

Science.gov (United States)

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, Ansgar; Scholz, Alexander; Eislöffel, Jochen; Hallinan, Gregg; Berger, Edo; Browning, Matthew; Irwin, Jonathan; Küker, Manfred; Matt, Sean

2009-02-01

320

Coil unit of toroidal magnetic field  

International Nuclear Information System (INIS)

Toroidal magnetic coil groups comprise all of conductors such as coils intersecting toroidal magnetic fields which reduce a transient inpedance for abruptly reducing or increasing electric current and equivalent primary inpedance reducing coils for abruptly reducing current upon protection from quenching in the toroidal magnetic field coils. Primary coil current is transferred to secondary coils by using protection coils as secondary coils, so that the current in the primary coils (that is, toroidal magnetic field coils) can be attenuated earlier than the attenuation of the total magnetic energy, to ensure protection operation from quenching. Then, occurrence of quenching phenomenon can be avoided efficiently, thereby enabling to attain remarkable cost down and simplification of systems. (N.H.)

321

Magnetic Field Created by Thin Wall Solenoids and Axially Magnetized Cylindrical Permanent Magnets  

OpenAIRE

This paper presents the calculation of the magnetic field created by axially magnetized cylindrical permanent magnets and thin wall solenoids in air. It emphasizes the equivalence of the source models: charged planes and current sheet. It shows that although the starting formulations, magnetic scalar potential, Coulomb's law, vector potential, Biot-Savart's law often depend in the literature on the source nature, they shouldn't. Indeed, it presents the magnetic field calculation for each poin...

Lemarquand, Guy; Lemarquand, Vale?rie; Babic, Slobodan; Akyel, Cevdet

2009-01-01

322

The magnetic field structure of Rotamak discharges  

International Nuclear Information System (INIS)

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

323

Quantum Antiferromagnets in a Magnetic Field  

OpenAIRE

Motivated by recent experiments on low-dimensional quantum magnets in applied magnetic fields, we present a theoretical analysis of their properties based on the nonlinear sigma model. The spin stiffness and a 1/N expansion are used to map the regimes of spin-gap behavior, predominantly linear magnetization, and spin saturation. A two-parameter renormalization-group study gives the characteristic properties over the entire parameter range. The model is relevant to many syste...

Loss, Daniel; Normand, B.

1998-01-01

324

Calculation of magnetic fields for engineering devices  

International Nuclear Information System (INIS)

The methodology of magnet technology and its application to various engineering devices are discussed. Magnet technology has experienced a rigid growth in the past few years as a result of the advances made in superconductivity, numerical methods and computational techniques. Included are discussions on: (1) mathematical models for solving magnetic field problems; (2) the applicability, usefulness, and limitations of computer programs that utilize these models; (3) examples of application in various engineering disciplines; and (4) areas where further contributions are needed

325

Mechanism of magnetic field effect in cryptochrome  

OpenAIRE

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 ...

Solov Yov, Ilia A.; Schulten, Klaus

2011-01-01

326

Magnetic monopoles in field theory and cosmology.  

Science.gov (United States)

The existence of magnetic monopoles is predicted by many theories of particle physics beyond the standard model. However, in spite of extensive searches, there is no experimental or observational sign of them. I review the role of magnetic monopoles in quantum field theory and discuss their implications for particle physics and cosmology. I also highlight their differences and similarities with monopoles found in frustrated magnetic systems. PMID:23166376

Rajantie, Arttu

2012-12-28

327

Magnetic Field Effects in Fermion Pairings  

OpenAIRE

This paper considers various fermion pairings of interest for the QCD phases. The effects of an external magnetic field on the pairing mechanisms, on the realization of new condensates, and on the properties of the magnetized phases are all explored and discussed.

La Incera, Vivian

2013-01-01

328

High-field superconducting nested coil magnet  

Science.gov (United States)

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

Laverick, C.; Lobell, G. M.

1970-01-01

329

Estimating the magnetic field strength from magnetograms  

CERN Document Server

A properly calibrated longitudinal magnetograph is an instrument that measures circular polarization and gives an estimation of the magnetic flux density in each observed resolution element. This usually constitutes a lower bound of the field strength in the resolution element, given that it can be made arbitrarily large as long as it occupies a proportionally smaller area of the resolution element and/or becomes more transversal to the observer and still produce the same magnetic signal. Yet, we know that arbitrarily stronger fields are less likely --hG fields are more probable than kG fields, with fields above several kG virtually absent-- and we may even have partial information about its angular distribution. Based on a set of sensible considerations, we derive simple formulae based on a Bayesian analysis to give an improved estimation of the magnetic field strength for magnetographs.

Ramos, A Asensio; Sainz, R Manso

2015-01-01

330

Cooling Curve of Strange Star in Strong Magnetic Field  

International Nuclear Information System (INIS)

In this paper, firstly, we investigate the neutrino emissivity from quark Urca process in strong magnetic field. Then, we discuss the heat capacity of strange stars in strong magnetic field. Finally, we give the cooling curve in strong magnetic field. In order to make a comparison, we also give the corresponding cooling curve in the case of null magnetic field. It turns out that strange stars cool faster in strong magnetic field than that without magnetic field

331

THE SNS RING DIPOLE MAGNETIC FIELD QUALITY.  

Energy Technology Data Exchange (ETDEWEB)

The large acceptance and compact size of the Spallation Neutron Source (SNS) ring implies the use of short, large aperture dipole magnets, with significant end field errors. The SNS will contain 32 such dipoles. We report magnetic field measurements of the first 16 magnets. The end field errors have been successfully compensated by the use of iron bumps. For 1.0 GeV protons, the magnets have been shimmed to meet the 0.01% specification for rms variation of the integral field. At 1.3 GeV, the rms variation is 0.036%. The load on the corrector system at 1.3 GeV will be reduced by the use of sorting.

WANDERER,P.; JACKSON,J.; JAIN,A.; LEE,Y.Y.; MENG,W.; PAPAPHILIPPOU,I.; SPATARO,C.; TEPIKIAN,S.; TSOUPAS,N.; WEI,J.

2002-06-03

332

THE SNS RING DIPOLE MAGNETIC FIELD QUALITY  

International Nuclear Information System (INIS)

The large acceptance and compact size of the Spallation Neutron Source (SNS) ring implies the use of short, large aperture dipole magnets, with significant end field errors. The SNS will contain 32 such dipoles. We report magnetic field measurements of the first 16 magnets. The end field errors have been successfully compensated by the use of iron bumps. For 1.0 GeV protons, the magnets have been shimmed to meet the 0.01% specification for rms variation of the integral field. At 1.3 GeV, the rms variation is 0.036%. The load on the corrector system at 1.3 GeV will be reduced by the use of sorting

333

Stability of Relativistic Matter with Magnetic Fields  

International Nuclear Information System (INIS)

Stability of matter with Coulomb forces has been proved for nonrelativistic dynamics, including arbitrarily large magnetic fields, and for relativistic dynamics without magnetic fields. In both cases stability requires that the fine structure constant ? be not too large. It was unclear what would happen for both relativistic dynamics and magnetic fields, or even how to formulate the problem clearly. We show that the use of the Dirac operator allows both effects, provided the filled negative energy is defined properly. The use of the free Dirac operator to define the negative levels leads to catastrophe for any ?, but the use of the Dirac operator with magnetic field leads to stability. copyright 1997 The American Physical Society

334

Stability of Relativistic Matter With Magnetic Fields  

CERN Document Server

Stability of matter with Coulomb forces has been proved for non-relativistic dynamics, including arbitrarily large magnetic fields, and for relativistic dynamics without magnetic fields. In both cases stability requires that the fine structure constant alpha be not too large. It was unclear what would happen for both relativistic dynamics and magnetic fields, or even how to formulate the problem clearly. We show that the use of the Dirac operator allows both effects, provided the filled negative energy `sea' is defined properly. The use of the free Dirac operator to define the negative levels leads to catastrophe for any alpha, but the use of the Dirac operator with magnetic field leads to stability.

Lieb, E H; Solovej, J P; Lieb, Elliott H.; Siedentop, Heinz; Solovej, Jan Philip

1997-01-01

335

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

336

NMR stabilizer of a dc magnetic field  

International Nuclear Information System (INIS)

The performance is described and a block diagram is presented of a dc magnetic field stabilizer operating in a pulse mode. All stabilizer blocks are placed in separate high-frequency shielded covers interconnected by coaxial cables. An NMR probe is fitted inside the electromagnet, close to the specimen being imaged. The field and scanning coils are wound directly on the test tube containing the stabilizing material. The stabilizer operating frequency is 3.64 MHz. In measuring the magnetic field of an experimental magnetic resonance tomograph of induction B = 0.085 T, a long-term stability (ca. 30 mins) was obtained of the magnetic field of ±1.4 ppm, i.e., 0.12 ?T. (J.B.)

337

ON THE GENERATION OF ORGANIZED MAGNETIC FIELDS  

International Nuclear Information System (INIS)

Motivated by the problem of the origin of astrophysical magnetic fields, we introduce two concepts. The first is that of a 'system-scale dynamo', i.e., a dynamo that can organize magnetic fields on the scale of the astrophysical object. The second is that of an 'essentially nonlinear dynamo'. This is a dynamo which relies on a velocity driven by magnetic forces and/or magnetic instabilities. We construct a simple framework that can be used to study such dynamos and give examples in which the evolution is such to generate a system-scale field. We argue that this framework provides a valuable complementary approach to the more conventional studies based on kinematic mean-field dynamo theory.

338

Heavy fermions in a high magnetic field  

International Nuclear Information System (INIS)

Heavy-fermion systems are intermetallic materials composed of rare earth (Ce, Yb) or actinides (U, Np, Pu) elements. In these systems, partially filled 4f- or 5f-electron orbitals are strongly-coupled to conduction-electron bands. We give an overview on experimental studies performed in the last 25 years on heavy fermion systems in a high magnetic field. The properties of field-induced magnetic transitions in heavy-fermion materials close to a quantum antiferromagnetic-to-paramagnetic instability are presented. Effects of a high magnetic field to the Fermi surface, in particular the splitting of spin-up and spin-down bands, are also considered. Finally, we review on recent advances on the study of non-centrosymmetric compounds and ferromagnetic superconductors in a high magnetic field

339

EIT waves and coronal magnetic field diagnostics  

CERN Document Server

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

340

A Holographic Bound on Cosmic Magnetic Fields  

CERN Document Server

Magnetic fields large enough to be observable are ubiquitous in astrophysics, even at extremely large length scales. This has led to the suggestion that such fields are seeded at very early (inflationary) times, and subsequently amplified by various processes involving, for example, dynamo effects. Many such mechanisms give rise to extremely large magnetic fields at the end of inflationary reheating, and therefore also during the quark-gluon plasma epoch of the early universe. Such plasmas have a well-known holographic description. We show that holography imposes an upper bound on the intensity of magnetic fields (scaled by the squared temperature) in these circumstances, and that the values expected in some models of cosmic magnetism come close to attaining that bound.

McInnes, Brett

2015-01-01

341

Split-Field Magnet facility upgraded  

CERN Document Server

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

342

Cosmic Magnetic Fields: Observations and Prospects  

Science.gov (United States)

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. Unpolarized emission traces turbulent fields which are strongest in galactic 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 (uni-directional) or anisotropic random (generated from isotropic random fields by compression or shear). Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions of starburst galaxies. The strongest ordered (mostly regular) fields of 10-15 ?G strength are generally found in galactic interarm regions and follow the orientation of adjacent gas spiral arms. 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 probably generated by a mean-field dynamo. 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.--The strength of the total magnetic field in our Milky Way is about 6 ?G near the solar radius, but several mG in dense clouds, pulsar wind nebulae, and filaments near the Galactic Center. Diffuse polarized radio emission and Faraday rotation data from pulsars and background sources show spiral fields with large-scale reversals, but the overall field structure in our Galaxy is still under debate.--Diffuse radio emission from the halos of galaxy clusters is mostly unpolarized because intracluster magnetic fields are turbulent, while cluster ``relics'', probably shock fronts by cluster mergers, can have degrees of polarization of up to 60% and extents of up to 2 Mpc. The IGM magnetic field strength is >=3 10-16 G with a filling factor of at least 60%, derived from the combination of data from the HESS and FERMI telescopes.--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. Small Faraday rotation measures can also be best measured at low frequencies. Polarization at higher frequencies (1-10 GHz), as observed with the EVLA, MeerKAT, APERTIF and the SKA, will trace magnetic fields in the disks and central regions of nearby galaxies in unprecedented detail. The SKA pulsar survey will find many new pulsars; their RMs will map the Milky Way's magnetic field with high precision. All-sky surveys of Faraday rotation measures towards a dense grid of polarized background sources with the SKA and its precursor telescope ASKAP are dedicated to measure magnetic fields in distant intervening galaxies, galaxy clusters and intergalactic filaments, and will be used to model the overall structure and strength of the magnetic field in the Milky Way. With the SKA, ordered fields in distant galaxies and cluster relics can be measured to redshifts of z~=0.5, turbulent fields in starburst galaxies or cluster halos to z~=3 and regular fields in intervening galaxies towards QSOs to z~=5.

Beck, Rainer

2011-09-01

343

Magnetic Field Analysis of Superconducting Undulators with Variable Field Polarization  

CERN Document Server

An undulator with double-helix coils on a cylindrical beam tube is the classical method of producing a helical magnetic field. This type of device, however, can produce only circularly polarized radiation and has limited horizontal aperture for beam injection. A planar superconducting undulator SCU) unit of helical field, which generates horizontal and vertical fields perpendicular to the beam direction, is inserted in between the magnetic poles of a vertical-field unit. This paper analyzes the magnetic fields and a scaling law of the SCU. The angle of the coil windings for the inserted unit is analyzed to maximize the horizontal field Bx. The range of the optimum rotation angle, for the range of gap/period ratio 0.1 - 0.6, is calculated to 30 - 40 degrees.

Kim, Suk H

2005-01-01

344

Magnetic fields in superconducting neutron stars  

OpenAIRE

The interior of a neutron star is likely to be predominantly a mixture of superfluid neutrons and superconducting protons. This results in the quantisation of the star's magnetic field into an array of thin fluxtubes, producing a macroscopic force very different from the Lorentz force of normal matter. We show that in an axisymmetric superconducting equilibrium the behaviour of a magnetic field is governed by a single differential equation. Solving this, we present the first...

Lander, S. K.

2012-01-01

345

Hyperon bulk viscosity in strong magnetic fields  

OpenAIRE

We study the bulk viscosity of neutron star matter including $\\Lambda$ hyperons in the presence of quantizing magnetic fields. Relaxation time and bulk viscosity due to both the non-leptonic weak process involving $\\Lambda$ hyperons and direct Urca processes are calculated here. In the presence of a strong magnetic field of $10^{17}$ G, the hyperon bulk viscosity coefficient is reduced whereas bulk viscosity coefficients due to direct Urca processes are enhanced compared wit...

Sinha, Monika; Bandyopadhyay, Debades

2008-01-01

346

Photospheric magnetic field and chromospheric emission  

CERN Document Server

We present a statistical analysis of network and internetwork properties in the photosphere and the chromosphere. For the first time we simultaneously observed (a) the four Stokes parameters of the photospheric iron line pair at 630.2 nm and (b) the intensity profile of the Ca II H line at 396.8 nm. The vector magnetic field was inferred from the inversion of the iron lines. We aim at an understanding of the coupling between photospheric magnetic field and chromospheric emission.

Rezaei, R; Beck, C; Schmidt, W

2007-01-01

347

Photospheric magnetic field and chromospheric emission  

OpenAIRE

We present a statistical analysis of network and internetwork properties in the photosphere and the chromosphere. For the first time we simultaneously observed (a) the four Stokes parameters of the photospheric iron line pair at 630.2 nm and (b) the intensity profile of the Ca II H line at 396.8 nm. The vector magnetic field was inferred from the inversion of the iron lines. We aim at an understanding of the coupling between photospheric magnetic field and chromospheric emis...

Rezaei, R.; Schlichenmaier, R.; Beck, C.; Schmidt, W.

2007-01-01

348

Charmonia and Bottomonia in a Magnetic Field  

OpenAIRE

We study the effect of a static homogeneous external magnetic field on charmonium and bottomonium states. In an external magnetic field, quarkonium states do not have a conserved center-of-mass momentum. Instead there is a new conserved quantity called the pseudomomentum which takes into account the Lorentz force on the particles in the system. When written in terms of the pseudomomentum, the internal and center-of-mass motions do not decouple and, as a result, the propertie...

Alford, Jeremy; Strickland, Michael

2013-01-01

349

Magnetic Branes Supported by Nonlinear Electromagnetic Field  

OpenAIRE

Considering the nonlinear electromagnetic field coupled to Einstein gravity in the presence of cosmological constant, we obtain a new class of $d$-dimensional magnetic brane solutions. This class of solutions yields a spacetime with a longitudinal nonlinear magnetic field generated by a static source. These solutions have no curvature singularity and no horizons but have a conic geometry with a deficit angle $\\delta \\phi$. We investigate the effects of nonlinearity on the me...

Hendi, Seyed Hossein

2010-01-01

350

Transverse quasilinear relaxation in inhomogeneous magnetic field  

OpenAIRE

Transverse quasilinear relaxation of the cyclotron-Cherenkov instability in the inhomogeneous magnetic field of pulsar magnetospheres is considered. We find quasilinear states in which the kinetic cyclotron-Cherenkov instability of a beam propagating through strongly magnetized pair plasma is saturated by the force arising in the inhomogeneous field due to the conservation of the adiabatic invariant. The resulting wave intensities generally have nonpower law frequency depend...

Lyutikov, Maxim

1998-01-01

351

The spiral configuration of sunspot magnetic fields  

International Nuclear Information System (INIS)

Distributions of circularly and linearly polarized intensities are computed using an analytical magnetic field model for an isolated sunspot, and these intensity distributions are compared with observed intensities in all Stokes parameters in the lambda 5250 line measured with the Marshall Space Flight Center's vector magnetograph. The qualitative agreement between measured and calculated linearly polarized intensity distributions is discussed with regard to implications as to the configuration of the transverse magnetic field of the isolated sunspot. (Auth.)

352

Primordial Magnetic Fields and Stochastic GW Backgrounds  

OpenAIRE

Operating resonant mass detectors set interesting bounds on diffused backgrounds of gravitational radiation and in the next five years the wide-band interferometers will also look for stochastic sources. In this lecture the interplay among relic GW backgrounds and large scale magnetic fields will be discussed. Magnetic fields may significantly affect the thermal history of the Universe in particular at the epoch electroweak symmetry breaking and shortly after. A review of so...

Giovannini, Massimo

2002-01-01

353

Non-yrast quadrupole-octupole spectra  

Directory of Open Access Journals (Sweden)

Full Text Available A model of strongly coupled quadrupole and octupole vibrations and rotations is applied to describe non-yrast alternating-parity sequences in even-even nuclei and split parity-doublet spectra in odd-mass nuclei. In even-even nuclei the yrast alternating-parity sequence includes the ground-state band and the lowest negative-parity levels with odd angular momenta, while the non-yrast sequences include excited ?-bands and higher negative-parity levels. In odd-mass nuclei the yrast levels are described as low-energy rotation-vibration modes coupled to the ground single-particle (s.p. state, while the non-yrast parity-doublets are obtained as higher-energy rotation-vibration modes coupled to excited s.p. configurations. We show that the extended model scheme describes the yrast and non-yrast quadrupole-octupole spectra in both even-even and odd-A nuclei. The involvement of the reflection-asymmetric deformed shell model to explain the single-particle motion and the Coriolis interaction in odd nuclei is discussed.

Lenske H.

2012-12-01

354

Electric and magnetic fields and ecology  

International Nuclear Information System (INIS)

Much of the paper explains electric and magnetic fields and how power transfer takes place in overhead transmission lines. Calculations of electric fields at ground level are shown, and how man may be affected by such fields is discussed. The article draws on some of the many reviews of data on the biological and health effects of electric and magnetic fields and discusses the role of the National Radiological Protection Board's Advisory Group on Non-Ionizing Radiation. The findings of US and Swedish groups who studied the effects of overhead lines on farm animals and crops are mentioned

355

Interstellar magnetic fields: An observational perspective  

International Nuclear Information System (INIS)

The plausibility of magnetic molecular clouds is established. It is shown that the empirically known relations between spectral line width, density, and cloud size can be derived from a virial equilibrium model where gravity is balanced by the sum of magnetic and pressure support. It is shown that substitution of measured density, cloud size, and line width measurements into the model can predict observed field strength to within a factor of two. The Zeeman effect is discussed and new measurements are presented for magnetic field strength based on OH and HI Zeeman observations at the Arecibo and Green Bank telescopes. The Barnard 1 (B1) region, in the Perseus Molecular Cloud Complex, is discussed in detail. OH spectral line intensity maps are presented for the regions where the OH Zeeman effect was observed, which allow, for the first time, comparison of observed field strength values with predicted field strength values, using emission from a single molecular species. Spatial structure of magnetic fields in molecular clouds are investigated. New optical polarization maps are presented for the dark clouds in Perseus, Taurus, and Ophiuchus. The polarization observed is attributed to preferential extinction of background starlight by magnetically aligned dust grains in the clouds, and we analyze the polarization maps as maps of the projection of the magnetic field onto the plane of the sky

356

Magnetic Field Spectrum at Cosmological Recombination Revisited  

CERN Document Server

If vector type perturbations are present in the primordial plasma before recombination, the generation of magnetic fields is known to be inevitable through the Harrison mechanism. In the context of the standard cosmological perturbation theory, non-linear couplings of first-order scalar perturbations create second-order vector perturbations, which generate magnetic fields. Here we reinvestigate the generation of magnetic fields at second-order in cosmological perturbations on the basis of our previous study, and extend it by newly taking into account the time evolution of purely second-order vector perturbations with a newly developed second-order Boltzmann code. We confirm that the amplitude of magnetic fields from the product-terms of the first-order scalar modes is consistent with the result in our previous study. However, we find, both numerically and analytically, that the magnetic fields from the purely second-order vector perturbations partially cancel out the magnetic fields from one of the product-te...

Saga, Shohei; Takahashi, Keitaro; Sugiyama, Naoshi

2015-01-01

357

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 thesing 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)

358

Do neutron star magnetic fields decay  

International Nuclear Information System (INIS)

The evidence for and against magnetic field decay in neutron stars is discussed, both for pulsars and for binary neutron stars. From the distribution of PP versus P/P it is concluded that the decay model of magnetic dipole moments is at variance with the data: in particular, there is an unexplained drop-out of pulsars with spindown ages > 107 yr. Even more stringent are the constraints on magnetic field decay in binary X-ray sources. Neutron star dipole moments may well be conserved for several 107 years. (orig.)

359

Irradiation-resistant magnetic field microsensors  

OpenAIRE

A technology developed for creating radiationresistant magnetic field sensors based on semiconductor binary compounds of III-V group (InSb, InAs, GaAs) and their solid solutions (InXGa1-XAs, InAsXIn1-X) is presented. Studies have confirmed such sensors’ operability in neutron fluxes up to high fluences. This has made possible their use in magnetic measuring instrumentation for magnetic field diagnostics in thermonuclear reactors. The instrumentation comprises a 3D probe with Hall sensors...

Bolshakova, Inessa; Yerashok, Volodymyr; Zagachevskyi, Yuriy; Makido, Olena; Tymoshyn, Serhiy; Stetsko, Roman; Kokoten, Nazar; Prykhodko, Oleksandr; Shurygin, Fedir

2013-01-01

360

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

361

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

362

Where is magnetic anisotropy field pointing to?  

CERN Document Server

The desired result of magnetic anisotropy investigations is the determination of value(s) of various anisotropy constant(s). This is sometimes difficult, especially when the precise knowledge of saturation magnetization is required, as it happens in ferromagnetic resonance (FMR) studies. In such cases we usually resort to `trick' and fit our experimental data to the quantity called \\emph{anisotropy field}, which is strictly proportional to the ratio of the searched anisotropy constant and saturation magnetization. Yet, this quantity is scalar, simply a number, and is therefore of little value for modeling or simulations of the magnetostatic or micromagnetic structures. Here we show how to `translate' the values of magnetic anisotropy constants into the complete vector of magnetic anisotropy field. Our derivation is rigorous and covers the most often encountered cases, from uniaxial to cubic anisotropy.

Gutowski, Marek W

2013-01-01

363

Magnetic susceptibility and magnetization properties of asymmetric nuclear matter under a strong magnetic field  

OpenAIRE

We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields $B \\sim 10^{16} - 10^{17}$ G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same...

Rabhi, A.; Pe?rez-garci?a, M. A.; Provide?ncia, C.; Vidan?a, I.

2014-01-01

364

Simulating magnetic fields in the Antennae galaxies  

CERN Document Server

We present self-consistent high-resolution simulations of NGC4038/4039 (the "Antennae galaxies") including star formation, supernova feedback and magnetic fields performed with the N-body/SPH code Gadget, in which hydrodynamics and magnetohydrodynamics are followed with the SPH method. We vary the initial magnetic field in the progenitor disks from 1 nG to 1 muG. At the time of the best match with the central region of the Antennae system the magnetic field has been amplified by compression and shear flows to an equilibrium field of approximately 10 muG, independent of the initial seed field. This simulations are a proof of the principle that galaxy mergers are efficient drivers for the cosmic evolution of magnetic fields. We present a detailed analysis of the magnetic field structure in the central overlap region. Simulated radio and polarization maps are in good morphological and quantitative agreement with the observations. In particular, the two cores with the highest synchrotron intensity and ridges of r...

Kotarba, H; Naab, T; Johansson, P H; Dolag, K; Lesch, H

2009-01-01

365

Microscopic description of octupole shape-phase transitions in light actinides and rare-earth nuclei  

CERN Document Server

A systematic analysis of low-lying quadrupole and octupole collective states is presented, based on the microscopic energy density functional framework. By mapping the deformation constrained self-consistent axially symmetric mean-field energy surfaces onto the equivalent Hamiltonian of the $sdf$ interacting boson model (IBM), that is, onto the energy expectation value in the boson condensate state, the Hamiltonian parameters are determined. The study is based on the global relativistic energy density functional DD-PC1. The resulting IBM Hamiltonian is used to calculate excitation spectra and transition rates for the positive- and negative-parity collective states in four isotopic chains characteristic for two regions of octupole deformation and collectivity: Th, Ra, Sm and Ba. Consistent with the empirical trend, the microscopic calculation based on the systematics of $\\beta_{2}$-$\\beta_{3}$ energy maps, the resulting low-lying negative-parity bands and transition rates show evidence of a shape transition be...

Nomura, K; Niksic, T; Lu, Bing-Nan

2014-01-01

366

Spectroscopy of quadrupole and octupole states in rare-earth nuclei from a Gogny force  

CERN Document Server

Collective quadrupole and octupole states are described in a series of Sm and Gd isotopes within the framework of the interacting boson model (IBM), whose Hamiltonian parameters are deduced from mean field calculations with the Gogny energy density functional. The link between both frameworks is the ($\\beta_2\\beta_3$) potential energy surface computed within the Hartree-Fock-Bogoliubov framework in the case of the Gogny force. The diagonalization of the IBM Hamiltonian provides excitation energies and transition strengths of an assorted set of states including both positive and negative parity states. The resultant spectroscopic properties are compared with the available experimental data and also with the results of the configuration mixing calculations with the Gogny force within the generator coordinate method (GCM). The structure of excited $0^{+}$ states and its connection with double octupole phonons is also addressed. The model is shown to describe the empirical trend of the low-energy quadrupole and o...

Nomura, K; Robledo, L M

2015-01-01

367

Magnetic field measurements in white dwarfs. Magnetic field, rotation and spectrum of 40 Eri B  

OpenAIRE

This paper describes results of magnetic field measurements of white dwarfs carried out on the 6-m telescope for the last years. A magnetic field of about Be ~ 28 kG has been discovered in the degenerate star WD 1953-011. A rotational period of WD 0009+501, 1.83 hours, has been discovered, the average magnetic field of the star is = -42.3 +/- 5.4 kG and its semi-amplitude of the rotational variability is 32.0 +/- 6.8 kG. The variable magnetic field of the bright normal (n...

Fabrika, S. N.; Valyavin, G. G.; Burlakova, T. E.; Barsukova, E. A.; Monin, D. N.

2000-01-01

368

Superconductivity in Strong Magnetic Field (Greater Than Upper Critical Field)  

International Nuclear Information System (INIS)

The National High Magnetic Field Laboratory, funded by the National Science Foundation and other US federal Agencies, has in recent years built a wide range of magnetic fields, DC 25 to 35 Tesla, short pulse 50 - 60 Tesla, and quasi-continuous 60 Tesla. Future plans are to push the frontiers to 45 Tesla DC and 70 to 100 Tesla pulse. This user facility, is open for national and international users, and creates an excellent tool for materials research (metals, semiconductors, superconductors, biological systems ..., etc). Here we present results of a systematic study of the upper critical field of a novel superconducting material which is considered a promising candidate for the search for superconductivity beyond Hc2 as proposed by several new theories. These theories predict that superconductors with low carrier density can reenter the superconducting phase beyond the conventional upper critical field Hc2. This negates the conventional thinking that superconductivity and magnetic fields are antagonistic

369

Simultaneous quadrupole and octupole shape phase transitions in Thorium  

International Nuclear Information System (INIS)

The evolution of quadrupole and octupole shapes in Th isotopes is studied in the framework of nuclear Density Functional Theory. Constrained 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 neutron number. The nucleus 224Th is closest to the critical point of a double phase transition. A microscopic mechanism of this phenomenon is discussed in terms of the evolution of single-nucleon orbitals with deformation

370

Electrical Properties of Chain Microstructure Magnetic Emulsions in Magnetic Field  

OpenAIRE

The work deals with the experimental study of the emulsion whose dispersion medium is a magnetic fluid while the disperse phase is formed by a glycerin-water mixture. It is demonstrated that under effect of a magnetic field chain aggregates form from the disperse phase drops. Such emulsion microstructure change affects its macroscopic properties. The emulsion dielectric permeability and specific electrical conductivity have been measured. It is demonstrated that under the ef...

Zakinyan, Arthur; Dikansky, Yury; Bedzhanyan, Marita

2014-01-01

371

Magnetizing a complex plasma without a magnetic field  

CERN Document Server

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

372

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

373

Magnetic Fields on the Surface of the Sun  

Science.gov (United States)

This is a lesson about magnetism in solar flares. Learners will map magnetic fields around bar magnets and investigate how this configuration relates to magnetic fields of sunspots. This activity requires compasses, bar magnets, and a equipment for the instructor to project a PowerPoint or pdf lecture presentation. This is Activity 1 in the Exploring Magnetism in Solar Flares teachers guide.

374

Flow control of magnetic fluids exposed to magnetic fields  

International Nuclear Information System (INIS)

The description of flow in ferrohydrodynamics (Rosensweig, 1985) is based on a combination of equations, namely the continuity equation, the Navier-Stokes equation, the Maxwell equations and particular equations for the magnetization. Since the different models to describe the relaxation of magnetization differ, the adequate one has yet to be identified. By comparing experimental and simulation data of a model system, this goal may get achieved. As a model system, a Taylor-Couette apparatus was chosen. In this paper, experimental results concerning the transition form circular Couette flow to Taylor vortex flow at different field strengths of an axial magnetic field are compared to a linear stability analysis. The relaxation equation established by Shliomis (Shliomis, 1972) and the Debye-Model with a field dependent relaxation time showed to give qualitative accordance with the experimental data.

375

Flow control of magnetic fluids exposed to magnetic fields  

Science.gov (United States)

The description of flow in ferrohydrodynamics (Rosensweig, 1985) is based on a combination of equations, namely the continuity equation, the Navier-Stokes equation, the Maxwell equations and particular equations for the magnetization. Since the different models to describe the relaxation of magnetization differ, the adequate one has yet to be identified. By comparing experimental and simulation data of a model system, this goal may get achieved. As a model system, a Taylor-Couette apparatus was chosen. In this paper, experimental results concerning the transition form circular Couette flow to Taylor vortex flow at different field strengths of an axial magnetic field are compared to a linear stability analysis. The relaxation equation established by Shliomis (Shliomis, 1972) and the Debye-Model with a field dependent relaxation time showed to give qualitative accordance with the experimental data.

Reindl, M.; Leschhorn, A.; Lücke, M.; Odenbach, S.

2009-02-01

376

Lightning Magnetic Field Measurements around Langmuir Laboratory  

Science.gov (United States)

In the absence of artificial conductors, underground lightning transients are produced by diffusion of the horizontal surface magnetic field of a return stroke vertically downward into the conducting earth. The changing magnetic flux produces an orthogonal horizontal electric field, generating a dispersive, lossy transverse electromagnetic wave that penetrates a hundred meters or more into the ground according to the skin depth of the medium. In turn, the electric field produces currents that flow toward or away from the channel to ground depending on the stroke polarity. The underground transients can produce large radial horizontal potential gradients depending on the distance from the discharge and depth below the surface. In this study we focus on the surface excitation field. The goal of the work is to compare measurements of surface magnetic field waveforms B(t) at different distances from natural lightning discharges with simple and detailed models of the return stroke fields. In addition to providing input to the diffusion mechanism, the results should aid in further understanding return stroke field generation processes. The observational data are to be obtained using orthogonal sets of straightened Rogowski coils to measure magnetic field waveforms in N-S and E-W directions. The waveforms are sampled at 500 kS/s over 1.024 second time intervals and recorded directly onto secure digital cards. The instrument operates off of battery power for several days or weeks at a time in remote, unattended locations and measures magnetic field strengths of up to several tens of amperes/meter. The observations are being made in conjunction with collocated slow electric field change measurements and under good 3-D lightning mapping array (LMA) and fast electric field change coverage.

Stock, M.; Krehbiel, P. R.; Rison, W.; Aulich, G. D.; Edens, H. E.; Sonnenfeld, R. G.

2010-12-01

377

Strongly interacting matter in magnetic fields  

International Nuclear Information System (INIS)

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. Editeory 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.

378

Galactic magnetic fields and hierarchical galaxy formation  

CERN Document Server

A framework is introduced for coupling the evolution of galactic magnetic fields sustained by the mean-field dynamo with the formation and evolution of galaxies in the cold dark matter cosmology. Estimates of the steady-state strength of the large-scale and turbulence magnetic fields from mean-field and fluctuation dynamo models are used together with galaxy properties predicted by semi-analytic models of galaxy formation for a population of spiral galaxies. We find that the field strength is mostly controlled by the evolving gas content of the galaxies. Thus, because of the differences in the implementation of the star formation law, feedback from supernovae and ram-pressure stripping, each of the galaxy formation models considered predicts a distribution of field strengths with unique features. The most prominent of them is the difference in typical magnetic fields strengths obtained for the satellite and central galaxies populations as well as the typical strength of the large-scale magnetic field in galax...

Rodrigues, Luiz Felippe S; Fletcher, Andrew; Baugh, Carlton

2015-01-01

379

Magnetic Field Inversion in Vortices in Multilayers  

CERN Document Server

We present a description of very dense vortex lattices in highly anisotropic multilayers, for high fields parallel to the layers. We show that a magnetic field inversion can occur away from the center of a vortex, provided the layers are sufficiently far apart.

Theodorakis, S; Theodorakis, Stavros; Leontidis, Epameinondas

1997-01-01

380

Source of the earth's magnetic field  

International Nuclear Information System (INIS)

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

381

Measurement of gradient magnetic field temporal characteristics  

International Nuclear Information System (INIS)

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

382

Heavy fermions in high magnetic fields  

International Nuclear Information System (INIS)

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The National High Magnetic Field Laboratory (NHMFL) has established major new facilities at LANL. This project sought to explore some exciting new problems in condensed matter physics that could be studied using these facilities. We studied the behavior of heavy-fermion compounds in high-magnetic fields. The unusual properties of these materials are governed by small energy scales arising from strong many-body correlations, demonstrating that the fields that can be achieved in the NHMFL can be used to probe these correlations

383

Heavy fermions in high magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The National High Magnetic Field Laboratory (NHMFL) has established major new facilities at LANL. This project sought to explore some exciting new problems in condensed matter physics that could be studied using these facilities. We studied the behavior of heavy-fermion compounds in high-magnetic fields. The unusual properties of these materials are governed by small energy scales arising from strong many-body correlations, demonstrating that the fields that can be achieved in the NHMFL can be used to probe these correlations.

Trugman, S.; Bedell, K.; Bonca, J.; Gulacsi, M. [Los Alamos National Lab., NM (United States); Yu, C. [California Univ., Irvine, CA (United States)

1996-05-01

384

Poloidal Magnetic Fields In Superconducting Neutron Stars  

CERN Document Server

We develop the formalism for computing the magnetic field within an axisymmetric neutron star with a strong Type II superconductor core surrounded by a normal conductor. The formalism takes full account of the constraints imposed by hydrostatic equilibrium with a barotropic equation of state. We specialize to purely poloidal magnetic fields and develop the "most dipolar case" for which we find that the surface field strength is $\\simeq H_b\\epsilon_b/3\\simeq 3\\times 10^{12}$ G, where $H_b$ is the magnetic field at the outer edge of the core and $\\epsilon_b R$ is the thickness of the normal shell. This value only depends on the equation of state of nuclear matter. We also find that the quadrupolar distortion of the star is $\\sim 10^{-9}$.

Henriksson, K T

2012-01-01

385

Magnetohydrodynamic experiments on cosmic magnetic fields  

CERN Document Server

It is widely known that cosmic magnetic fields, including the fields of planets, stars, and galaxies, are produced by the hydromagnetic dynamo effect in moving electrically conducting fluids. It is less well known that cosmic magnetic fields play also an active role in cosmic structure formation by enabling outward transport of angular momentum in accretion disks via the magnetorotational instability (MRI). Considerable theoretical and computational progress has been made in understanding both processes. In addition to this, the last ten years have seen tremendous efforts in studying both effects in liquid metal experiments. In 1999, magnetic field self-excitation was observed in the large scale liquid sodium facilities in Riga and Karlsruhe. Recently, self-excitation was also obtained in the French "von Karman sodium" (VKS) experiment. An MRI-like mode was found on the background of a turbulent spherical Couette flow at the University of Maryland. Evidence for MRI as the first instability of an hydrodynamica...

Stefani, Frank; Gerbeth, Gunter

2008-01-01

386

Jets, magnetic fields and the central engine  

International Nuclear Information System (INIS)

Reviewing recent observations of jets unconfined by external pressure, the author suggests that self-confinement may be common. This requires current-carrying jets with helical magnetic fields. Such beams occur in the laboratory, in lightning, and in the Crab Nebula, where currents are apparently carried over distances greater than a light year. Self-confined jets require a significant torodial magnetic field emerging from the nozzle. The author suggests that the parallel/azimuthal magnetic field ratio may be the crucial nozzle parameter, causing asymmetries. Helical field configurations have remarkable stability properties and can evolve naturally as synchrotron losses in the jet lead to minimizing Lorentz forces. Current-carrying jets may provide a valuable clue to the physics of the central source. (Auth.)

387

Assessment of inhomogeneous ELF magnetic field exposures  

International Nuclear Information System (INIS)

In daily life as well as at workplaces, exposures to inhomogeneous magnetic fields become very frequent. This makes easily applicable compliance assessment methods increasingly important. Reference levels have been defined linking basic restrictions to levels of homogeneous fields at worst-case exposure conditions. If reference levels are met, compliance with basic restrictions can be assumed. If not, further investigations could still prove compliance. Because of the lower induction efficiency, inhomogeneous magnetic fields such as from electric appliances could be allowed exceeding reference levels. To easily assess inhomogeneous magnetic fields, a quick and flexible multi-step assessment procedure is proposed. On the basis of simulations with numerical, anatomical human models reference factors were calculated elevating reference levels to link hot-spot values measured at source surfaces to basic limits and allowing accounting for different source distance, size, orientation and position. Compliance rules are proposed minimising assessment efforts. (authors)

388

Compute Values of Earth's Magnetic Field  

Science.gov (United States)

The program run from this form computes the values of the Earth's magnetic field parameters for a given location and date or date range. Input required is the date and location (in latitude and longitude) of interest. Links to the U.S. Census Bureau's U.S. Gazeteer and the Getty Thesaurus assists in determing the latitude and longitude for locations of interest. The magnetic parameters (D, I, H, X, Y, Z, and F) are computed based on the latest International Geomagnetic Reference Field (IGRF), a Schmidt quasinormalized spherical harmonic model of the magnetic field. Accuracies for the angular components (Declination, D and Inclination, I) are reported in degrees and minutes of arc and are generally within 30 minutes. Accuracies for the force components (Horizontal - H, North - X, East - Y, Vertical - Z, and Total force - F) are generally within 25 nanotesla. A link to frequently-asked questions about the geomagnetic field of Earth is provided as background material.

389

Conversion of free magnetic polaron into vortex lattice in diluted magnetic semiconductors in quantizing magnetic fields  

OpenAIRE

We show that in strong (quantizing) magnetic fields "ordinary" free magnetic polaron in diluted magnetic semiconductors (of type $A^2MeB^6$, where Me=Fe, Mn) exists in the form of vortex lattice quite similar to that in type II superconductors (Abricosov vortex lattice). The region of external parameters (like external magnetic field and temperature), where such lattice exists, is determined from the condition that lattice dimension is less or equal to polaron localization r...

Stephanovich, V. A.

2000-01-01

390

Primordial magnetic fields from self-ordering scalar fields  

Science.gov (United States)

A symmetry-breaking phase transition in the early universe could have led to the formation of cosmic defects. Because these defects dynamically excite not only scalar and tensor type cosmological perturbations but also vector type ones, they may serve as a source of primordial magnetic fields. In this study, we calculate the time evolution and the spectrum of magnetic fields that are generated by a type of cosmic defects, called global textures, using the non-linear sigma (NLSM) model. Based on the standard cosmological perturbation theory, we show, both analytically and numerically, that a vector-mode relative velocity between photon and baryon fluids is induced by textures, which inevitably leads to the generation of magnetic fields over a wide range of scales. We find that the amplitude of the magnetic fields is given by B~10?9((1+z)/103)?2.5(v/mpl)2(k/Mpc?1)3.5/?N Gauss in the radiation dominated era for klesssim 1 Mpc?1, with v being the vacuum expectation value of the O(N) symmetric scalar fields. By extrapolating our numerical result toward smaller scales, we expect that B~ 10?14.5((1+z)/103)1/2(v/mpl)2(k/Mpc?1)1/2/?N Gauss on scales of kgtrsim 1 Mpc?1 at redshift 0zgtrsim 110. This might be a seed of the magnetic fields observed on large scales today.

Horiguchi, Kouichirou; Ichiki, Kiyotomo; Sekiguchi, Toyokazu; Sugiyama, Naoshi

2015-04-01

391

Vacuum polarization tensor in inhomogeneous magnetic fields  

CERN Document Server

We develop worldline numerical methods, which combine string-inspired with Monte-Carlo techniques, for the computation of the vacuum polarization tensor in inhomogeneous background fields for scalar QED. The algorithm satisfies the Ward identity exactly and operates on the level of renormalized quantities. We use the algorithm to study for the first time light propagation in a spatially varying magnetic field. Whereas a local derivative expansion applies to the limit of small variations compared to the Compton wavelength, the case of a strongly varying field can be approximated by a derivative expansion for the averaged field. For rapidly varying fields, the vacuum-magnetic refractive indices can exhibit a non-monotonic dependence on the local field strength. This behavior can provide a natural limit on the self-focussing property of the quantum vacuum.

Gies, Holger

2011-01-01

392

Near-zero-field nuclear magnetic resonance  

CERN Document Server

We investigate nuclear magnetic resonance (NMR) in near-zero-field, where the Zeeman interaction can be treated as a perturbation to the electron mediated scalar interaction (J-coupling). This is in stark contrast to the high field case, where heteronuclear J-couplings are normally treated as a small perturbation. We show that the presence of very small magnetic fields results in splitting of the zero-field NMR lines, imparting considerable additional information to the pure zero-field spectra. Experimental results are in good agreement with first-order perturbation theory and with full numerical simulation when perturbation theory breaks down. We present simple rules for understanding the splitting patterns in near-zero-field NMR, which can be applied to molecules with non-trivial spectra.

Ledbetter, Micah; Blanchard, John; Ring, Hattie; Ganssle, Paul; Appelt, Stephan; Bluemich, Bernhard; Pines, Alex; Budker, Dmitry

2011-01-01

393

Studying the magnetic fields of cool stars  

Science.gov (United States)

Magnetic fields are prevalent in a wide variety of low mass stellar systems and play an important role in their evolution. Yet the process through which these fields are generated is not well understood. To understand how such systems can generate strong field structures characterization of these fields is required. Radio emission traces the fields directly and the properties of this emission can be modeled leading to constraints on the field geometry and magnetic parameters. The new Karl Jansky Very Large Array (VLA) provides highly sensitive radio observations. My thesis involves combining VLA observations with the development of magnetospheric emission models in order to characterize the magnetic fields in two fully convective cool star systems: (1) Young Stellar Objects (YSOs); (2) Ultracool dwarf stars. I conducted multi epoch observations of DG Tau, a YSO with a highly active, collimated outflow. The radio emission observed from this source was found to be optically thick thermal emission with no indication of the magnetic activity observed in X-rays. I determined that the outflow is highly collimated very close to the central source, in agreement with jet launching models. Additionally, I constrained the mass loss of the ionized component of the jet and found that close to the central source the majority of mass is lost through this component. Using lower angular resolution observations, I detected shock formations in the extended jet of DG Tau and modeled their evolution with time. Taking full advantage of the upgraded bandwidth on the VLA, I made wideband observations of two UCDs, TVLM513-46 and 2M 0746+20. Combining these observations with previously published and archival VLA observations I was able to fully characterize the spectral and temporal properties of the radio emission. I found that the emission is dominated by a mildly polarized, non-thermal quiescent component with periodic strongly polarized flare emission. The spectral energy distribution and polarization of the quiescent emission is well modeled using gyrosynchrotron emission with a mean field B ˜100 G, mildly relativistic power-law electrons with a density ne ˜ 105-6 cm-3, and source size of R ˜ 2R*. We were able to model the pulsed emission by coherent electron cyclotron radiation from a small number of isolated loops of high magnetic field (2-3 kG) with scale heights˜1.2-2.7 stellar radii. The loops are well-separated in magnetic longitude, and are not part of a single dipolar magnetosphere. The overall magnetic configuration of both stars appears to confirm recent suggestions that radio over-luminous UCD's have `weak field' non-axisymmetric topologies, but with isolated regions of high magnetic field.

Lynch, Christene Rene

394

Upper critical magnetic field of superconducting films with magnetic impurities  

Energy Technology Data Exchange (ETDEWEB)

The upper critical magnetic field, H/sub c2/(T), of In-Mn and Pb-Mn alloy films was measured. H/sub c2/ was determined from the resistance of the films. The results were compared with the theory of Fulde and Maki. This theory assumes that the electron-phonon coupling is weak, and that the interaction between the impurity spins and the conduction electron spins is weak. The theory predicts that the pair-breaking effect of the magnetic impurities is temperature-independent, and that the pair-breaking effects of the magnetic impurities and the applied magnetic field are additive. Furthermore, it predicts explicitly the temperature dependence of H/sub c2/. The temperature dependence of H/sub c2/ for the In-Mn alloy films is well described by the Fulde-Maki theory, despite the moderately strong electron-phonon coupling and the strong interaction between the impurity spins and the conduction electron spins. The temperature dependence of H/sub c2/ for the Pb-Mn alloy films is not well described by the Fulde-Maki theory, probably due to the strong electron-phonon coupling in Pb. However, even without a quantitatively correct theory, one can conclude from the Pb-Mn data that the pair-breaking effect of the magnetic impurities is temperature independent, and that the pair-breaking effects of the magnetic impurities and the applied magnetic field are additive. For some of the Pb-Mn alloy films, there was a region of positive curvature in H/sub c2/(T) near the zero-field transition temperature. This positive curvature is not understood.

Lemberger, Thomas Richard

1978-07-05

395

Holography, Fractionalization and Magnetic Fields  

OpenAIRE

Four dimensional gravity with a U(1) gauge field, coupled to various fields in asymptotically anti-de Sitter spacetime, provides a rich arena for the holographic study of the strongly coupled (2+1)-dimensional dynamics of finite density matter charged under a global U(1). As a first step in furthering the study of the properties of fractionalized and partially fractionalized degrees of freedom in the strongly coupled theory, we construct electron star solutions at zero tempe...

Albash, Tameem; Johnson, Clifford V.; Macdonald, Scott

2012-01-01

396

Generation of magnetic fields in planets  

International Nuclear Information System (INIS)

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

397

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

398

A magnetic fields measurement system for undulator  

International Nuclear Information System (INIS)

The undulator is one of the key devices in the studies of free electron laser (FEL). During the design and fabrication of the undulator, it's necessary to the magnetic fields in the undulator with high precision. An automatic magnetic fields measurement system is reported here which is mainly for the measurement of a hybrid undulator of FEL and can also be used in measuring the fields of the multipole lenses, the coaxial coils and the bend magnets of accelerators. A high sensitive Hall probe with micro dimensions has been used as the magnetic fields sensor. The mechanical driving parts of the system enable the detective probe either to move along the lines or to turn around in different radii. The system is controlled by an AST/386 micro-computer. The software has many functions and the user's interface is designed in forms of pull-down and pop-up menus. From practical testing, when the changing gradient of the magnetic fields is about 1.00 x 10-2 T/mm, the measuring precision of the system ?B/Bp = (0.3?1.5) x 10-4, when the gradient is about 6.00 x 10-2 T/mm, the measuring precision ?B/Bp = (1.5?5) x 10-4

399

Magnetic field evolution in interacting galaxies  

CERN Document Server

Violent gravitational interactions can change the morphologies of galaxies and, by means of merging, transform them into elliptical galaxies. We aim to investigate how they affect the evolution of galactic magnetic fields. We selected 16 systems of interacting galaxies and compared their radio emission and estimated magnetic field strengths with their star-forming activity, far-infrared emission, and the stage of tidal interaction. We find a general evolution of magnetic fields: for weak interactions the strength of magnetic field is almost constant (10-15muG) as interaction advances, then it increases up to 2x, peaks at the nuclear coalescence (25muG), and decreases again, down to 5-6muG, for the post-merger remnants. The magnetic field strength for whole galaxies is weakly affected by the star formation rate (SFR), while the dependence is higher for galactic centres. We show that the morphological distortions visible in the radio total and polarized emission do not depend statistically on the global or loca...

Drzazga, Robert T; Jurusik, Wojciech; Wiorkiewicz, Krzysztof

2011-01-01

400

Magnetic Fields and Massive Star Formation  

CERN Document Server

Massive stars ($M > 8$ \\msun) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 $\\mu$m obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of $\\lsim$ 0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within $40^\\circ$ of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the ...

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

2014-01-01

401

Cosmic Magnetic Fields: Observations and Prospects  

CERN Document Server

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

402

Reionization constraints on primordial magnetic fields  

CERN Document Server

We study the impact of the extra density fluctuations induced by primordial magnetic fields on the reionization history in the redshift range: $6 < z < 10$. We perform a comprehensive MCMC physical analysis allowing the variation of parameters related to primordial magnetic fields (strength, $B_0$, and power-spectrum index $n_{\\scriptscriptstyle \\rm B}$), reionization, and $\\Lambda$CDM cosmological model. We find that magnetic field strengths in the range: $B_0 \\simeq 0.05{-}0.3$ nG (for nearly scale-free power spectra) can significantly alter the reionization history in the above redshift range and can relieve the tension between the WMAP and quasar absorption spectra data. Our analysis puts upper-limits on the magnetic field strength $B_0 < 0.362, 0.116, 0.057$ nG (95 % c.l.) for $n_{\\scriptscriptstyle \\rm B} = -2.95, -2.9, -2.85$, respectively. These represent the strongest magnetic field constraints among those available from other cosmological observables.

Pandey, Kanhaiya L; Sethi, Shiv K; Ferrara, Andrea

2014-01-01

403

Magnetic Field Measurement with Ground State Alignment  

CERN Document Server

Observational studies of magnetic fields are crucial. We introduce a process "ground state alignment" as a new way to determine the magnetic field direction in diffuse medium. The alignment is due to anisotropic radiation impinging on the atom/ion. The consequence of the process is the polarization of spectral lines resulting from scattering and absorption from aligned atomic/ionic species with fine or hyperfine structure. The magnetic field induces precession and realign the atom/ion and therefore the polarization of the emitted or absorbed radiation reflects the direction of the magnetic field. The atoms get aligned at their low levels and, as the life-time of the atoms/ions we deal with is long, the alignment induced by anisotropic radiation is susceptible to extremely weak magnetic fields ($1{\\rm G}\\gtrsim B\\gtrsim 10^{-15}$G). In fact, the effects of atomic/ionic alignment were studied in the laboratory decades ago, mostly in relation to the maser research. Recently, the atomic effect has been already de...

Yan, Huirong

2013-01-01

404

Magnetic field stabilization by temperature control of an azimuthally varying field cyclotron magnet  

Science.gov (United States)

A magnetic field drift, gradual decrease of the order of 10-4 in several tens of hours, was observed with the beam intensity decrease in an operation of an azimuthally varying field (AVF) cyclotron. From our experimental results, we show that the temperature increase of the magnet iron by the heat transfer from the excitation coils can induce such change of the magnetic field as to deteriorate the beam quality. The temperature control of the magnet iron was realized by thermal isolation between the main coil and the yoke and by precise control of the cooling water temperature of the trim coils attached to the pole surfaces in order to prevent temperature change of the magnet iron. The magnetic field stability of ±5×10-6 and the beam intensity stability of ±2% have been achieved by this temperature control.

Okumura, S.; Arakawa, K.; Fukuda, M.; Nakamura, Y.; Yokota, W.; Ishimoto, T.; Kurashima, S.; Ishibori, I.; Nara, T.; Agematsu, T.; Sano, M.; Tachikawa, T.

2005-03-01

405

On the octupole excitation in 236U  

International Nuclear Information System (INIS)

Measurements of the K, Lsub(I), Lsub(II) and Msub(I) conversion lines of the 687.7 keV transition in 236U are evaluated within the electron penetration formalism. The spin-parity assignment of the octupole-band-head is found to be 1- in accordance with reaction data, and an assignment of 2- to the 687.7 keV state is ruled out. The penetration matrix element vertical strokeetavertical stroke has the value of 13.5 for the K-shell and increases slightly for higher main shells. An estimate of the anomalous amplitudes is compared with values reported for transitions in the odd even actinide nuclei. Furthermore electron conversion data for the 1-->2+ and 1-->4+ transitions are given. Radioactivity 236U from 235U(n,e-); measured: conversion electron decay; deduced: conversion coefficients from K, L and M shells; evaluated: dynamic matrix elements. (orig.)

406

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

Science.gov (United States)

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. PMID:21592484

Bi, Yanping; Pan, Xiaoxia; Chen, Lei; Wan, Qian-Hong

2011-06-24

407

Focus on Materials Analysis and Processing in Magnetic Fields  

OpenAIRE

Recently, interest in the applications of feeble (diamagnetic and paramagnetic) magnetic materials has grown, whereas the popularity of ferromagnetic materials remains steady and high. This trend is due to the progress of superconducting magnet technology, particularly liquid-helium-free superconducting magnets that can generate magnetic fields of 10 T and higher. As the magnetic energy is proportional to the square of the applied magnetic field, the magnetic energy of such 10 T magnets is in...

Yoshio Sakka, Noriyuki Hirota

2009-01-01

408

Mechanism of magnetic field effect in cryptochrome  

CERN Document Server

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

409

Probing magnetic fields with GALFACTS  

CERN Document Server

GALFACTS is a large-area spectro-polarimetric survey on the Arecibo Radio telescope. It uses the seven-beam focal plane feed array receiver system (ALFA) to carry out an imaging survey project of the 12,700 square degrees of sky visible from Arecibo at 1.4 GHz with 8192 spectral channels over a bandwidth of 300 MHz sampled at 1 millisecond. The aggregate data rate is 875 MB/s. GALFACTS observations will create full-Stokes image cubes at an angular resolution of 3.5' with a band-averaged sensitivity of 90 $\\mu$Jy, allowing sensitive imaging of polarized radiation and Faraday Rotation Measure from both diffuse emission and extragalactic sources. GALFACTS is a scientific pathfinder to the SKA in the area of cosmic magnetism. Key to magnetism science with the SKA is the technique of RM synthesis. The technique of RM synthesis is introduced and we discuss practical aspects of RM synthesis including efficient computational techniques and detection thresholds in the resulting Faraday spectrum. We illustrate the use ...

George, Samuel J; Andrecut, Mircea; Taylor, A Russ

2011-01-01

410

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

2003-01-01

411

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

Science.gov (United States)

The Spiral Magnetic Motor, which can accelerate a magnetized rotor through 90% of its cycle with only permanent magnets, was an energy milestone for the 20th century patents by Kure Tekkosho in the 1970's. However, the Japanese company used old ferrite magnets which are relatively weak and an electrically-powered coil to jump start every cycle, which defeated the primary benefit of the permanent magnet motor design. The principle of applying an inhomogeneous, anisotropic magnetic field gradient force Fz = ? cos ? dB/dz, with permanent magnets is well-known in physics, e.g., Stern-Gerlach experiment, which exploits the interaction of a magnetic moment with the aligned electron spins of magnetic domains. In this case, it is applied to dB/d? in polar coordinates, where the force F? depends equally on the magnetic moment, the cosine of the angle between the magnetic moment and the field gradient. The radial magnetic field increases in strength (in the attractive mode) or decreases in strength (in the repulsive mode) as the rotor turns through one complete cycle. An electromagnetic pulsed switching has been historically used to help the rotor traverse the gap (detent) between the end of the magnetic stator arc and the beginning (Kure Tekko, 1980). However, alternative magnetic pulse and switching designs have been developed, as well as strategic eddy current creation. This work focuses on the switching mechanism, novel magnetic pulse methods and advantageous angular momentum improvements. For example, a collaborative effort has begun with Toshiyuki Ueno (University of Tokyo) who has invented an extremely low power, combination magnetostrictive-piezoelectric (MS-PZT) device for generating low frequency magnetic fields and consumes "zero power" for static magnetic field production (Ueno, 2004 and 2007a). Utilizing a pickup coil such as an ultra-miniature millihenry inductor with a piezoelectric actuator or simply Wiegand wire geometry, it is shown that the necessary power for magnetic field switching device can be achieved in order to deflect the rotor magnet in transit. The Wiegand effect itself (bistable FeCoV wire called "Vicalloy") invented by John Wiegand (Switchable Magnetic Device, US Patent ?4,247,601), utilizing Barkhausen jumps of magnetic domains, is also applied for a similar achievement (Dilatush, 1977). Conventional approaches for spiral magnetic gradient force production have not been adequate for magnetostatic motors to perform useful work. It is proposed that integrating a magnetic force control device with a spiral stator inhomogeneous axial magnetic field motor is a viable approach to add a sufficient nonlinear boundary shift to apply the angular momentum and potential energy gained in 315 degrees of the motor cycle.

Valone, Thomas F.

2010-01-01

412

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

413

Vector magnetic fields of Solar Granulation  

OpenAIRE

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 ...

Jin, Chunlan; Wang, Jingxiu; Zhao, Meng

2008-01-01

414

Photon Redshift in a Magnetic field  

CERN Document Server

Previous results from the authors concerning the arising a tiny photon anomalous paramagnetic moment are also interpreted as a red-shift in analogy to the gravitational known effect. It is due to the photon interaction with the magnetized virtual electron-positron background which withdraw transverse momentum from photons and is polarization-dependent. If the photon frequency red-shift implies a change in time, a clock would go faster for increasing magnetic field intensity.

Rojas, H Pérez

2010-01-01

415

Magnetic String Coupled to Nonlinear Electromagnetic Field  

OpenAIRE

We introduce a class of rotating magnetically charged string solutions of the Einstein gravity with a nonlinear electrodynamics source in four dimensions. The present solutions has no curvature singularity and no horizons but has a conic singularity and yields a spacetime with a longitudinal magnetic field. Also, we investigate the effects of nonlinearity on the properties of the solutions and find that for the special range of the nonlinear parameter, the solutions are not ...

Hendi, S. H.

2010-01-01

416

Quadrupole-octupole coupled states in 112Cd  

International Nuclear Information System (INIS)

Negative-parity excitations in the 2.5 MeV region in 112Cd have been investigated with the (n,n'? reaction. Several of these states exhibit enhanced B(E2) values for decay to the 31- octupole state, indicative of quadrupole-octupole coupled (2+x3-) structures. The B(E1) values observed are typically in the range of 1-5x10-4 W.u., irrespective of the final state. (author)

417

Chaos in axially symmetric potentials with octupole deformation  

Energy Technology Data Exchange (ETDEWEB)

Classical and quantum mechanical results are reported for the single particle motion in a harmonic oscillator potential which is characterized by a quadrupole deformation and an additional octupole deformation. The chaotic character of the motion is strongly dependent on the quadrupole deformation in that for a prolate deformation virtually no chaos is discernible while for the oblate case the motion shows strong chaos when the octupole term is turned on.

Heiss, W.D.; Nazmitdinov, R.G.; Radu, S. (Centre for Nonlinear Studies and Department of Physics, University of Witwatersrand, PO Wits 2050, Johannesburg (South Africa) Departamento de Fisica Teorica C-XI, Universidad Autonoma de Madrid, E-28049, Madrid (Spain))

1994-04-11

418

Chaos in axially symmetric potentials with octupole deformation  

CERN Document Server

Classical and quantum mechanical results are reported for the single particle motion in a harmonic oscillator potential which is characterized by a quadrupole deformation and an additional octupole deformation. The chaotic character of the motion is srongly dependent on the quadrupole deformation in that for a prolate deformation virtually no chaos is discernible while for the oblate case the motion shows strong chaos when the octupole term is turned on.

Heiss, W D; Radu, S; Rashid G Nazmitdinov; Stefanel Radu

1994-01-01

419

Chaos in Axially Symmetric Potentials with Octupole Deformation  

OpenAIRE

Classical and quantum mechanical results are reported for the single particle motion in a harmonic oscillator potential which is characterized by a quadrupole deformation and an additional octupole deformation. The chaotic character of the motion is srongly dependent on the quadrupole deformation in that for a prolate deformation virtually no chaos is discernible while for the oblate case the motion shows strong chaos when the octupole term is turned on.

Heiss, W. Dieter; Nazmitdinov, Rashid G.; Radu, Stefanel

1994-01-01

420

Chaos in axially symmetric potentials with octupole deformation  

International Nuclear Information System (INIS)

Classical and quantum mechanical results are reported for the single particle motion in a harmonic oscillator potential which is characterized by a quadrupole deformation and an additional octupole deformation. The chaotic character of the motion is strongly dependent on the quadrupole deformation in that for a prolate deformation virtually no chaos is discernible while for the oblate case the motion shows strong chaos when the octupole term is turned on

421

Periodic Orbits and Shell Structure in Octupole Deformed Potentials  

OpenAIRE

The effect of an octupole term in a quadrupole deformed single particle potential is studied from the classical and quantum mechanical view point. Whereas the problem is nonintegrable, the quantum mechanical spectrum nevertheless shows some shell structure in the superdeformed prolate case for particular, yet fairly large octupole strengths; for spherical or oblate deformation the shell structure disappears. This result is associated with classical periodic orbits which are ...

Heiss, W. Dieter; Nazmitdinov, Rashid G.; Radu, Stefanel

1994-01-01

422

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

423

Near-field aperture-probe as a magnetic dipole source and optical magnetic field detector  

CERN Document Server

Scanning near-field field optical microscopy (SNOM) is a technique, which allows sub-wavelength optical imaging of photonic structures. While the electric field components of light can be routinely obtained, imaging of the magnetic components has only recently become of interest. This is so due to the development of artificial materials, which enhance and exploit the typically weak magnetic light-matter interactions to offer extraordinary optical properties. Consequently, both sources and detectors of the magnetic field of light are now required. In this paper, assisted by finite-difference time-domain simulations, we suggest that the circular aperture at the apex of a metal coated hollow-pyramid SNOM probe can be approximated by a lateral magnetic dipole source. This validates its use as a detector for the lateral magnetic near-field, as illustrated here for a plasmonic nanobar sample. Verification for a dielectric sample is currently in progress. We experimentally demonstrate the equivalence of the reciproc...

Denkova, Denitza; Silhanek, Alejandro V; Van Dorpe, Pol; Moshchalkov, Victor V

2014-01-01

424

Effect of magnetic field in malaria diagnosis using magnetic nanoparticles  

Science.gov (United States)

The current gold standard method of Malaria diagnosis relies on the blood smears examination. The method is laborintensive, time consuming and requires the expertise for data interpretation. In contrast, Raman scattering from a metabolic byproduct of the malaria parasite (Hemozoin) shows the possibility of rapid and objective diagnosis of malaria. However, hemozoin concentration is usually extremely low especially at the early stage of malaria infection, rendering weak Raman signal. In this work, we propose the sensitive detection of enriched ?-hematin, whose spectroscopic properties are equivalent to hemozoin, based on surface enhanced Raman spectroscopy (SERS) by using magnetic nanoparticles. A few orders of magnitude enhancement in the Raman signal of ?-hematin can be achieved using magnetic nanoparticles. Furthermore, the effect of magnetic field on SERS enhancement is investigated. Our result demonstrates the potential of SERS using magnetic nanoparticles in the effective detection of hemozoin for malaria diagnosis.

Liu, Quan; Yuen, Clement

2011-07-01

425

Magnetic field instabilities in accretion disks  

International Nuclear Information System (INIS)

The stability of magnetic fields within the accretion disks is examined, including the effects of magnetic buoyancy. Rayleigh-Taylor, and Kelvin-Helmholtz instabilities. The purpose of the study is to examine the efficacy of turbulent accretion (?-) disk models which depend upon ''magnetic viscosity'' to provide the dissipation necessary to account for radial infall. We provide estimates for the time scales of the dominant instabilities in both the gas pressure-dominated and radiation pressure-dominated regions of a thin accretion disk; provide constraints on dynamo processes such that ''magnetic viscosity'' operates to permit stationary accretion; show that field amplification may take place even in vertically stably stratified regions of a thin disk by the action of ''magnetic buoyancy-driven'' convection; and demonstrate that the turbulent Reynolds stress responsible for accretion is proportional to the gas pressure even in the radiation-dominated portion of the disk (so that the disk is stable to viscous and thermal instabilities). Furthermore, we show that if a ''seed'' magnetic field is injected into a thin accretion disk, then the formation of buoyancy-generated hot corona above the disk appears inevitable

426

Mechanical Response of Elastomers to Magnetic Fields  

Science.gov (United States)

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 material possessing conductive or magnetic properties have been widely used in applications such as conductive and magnetic tapes, sensors, flexible permanent magnets, etc. Our interest in these materials has focussed on understanding and controlling the magnitude and directionality of their response to applied magnetic fields. The effect of magnetic fields on the mechanical properties of these materials has not been the subject of many published studies. Our interest and expertise in controllable fluids have given us the foundation to make a transition to controllable elastomers. Controllable elastomers are materials that exhibit a change in mechanical properties upon application of an external stimuli, in this case a magnetic field. Controllable elastomers promise to have more functionality than conventional elastomers and therefore could share the broad industrial application base with conventional elastomers. As such, these materials represent an attractive class of smart materials, and may well be a link that brings the applications of modern control technologies, intelligent structures and smart materials to a very broad industrial area. This presentation will cover our research work in the area of controllable elastomers at the Thomas Lord Research Center. More specifically, the 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.

Munoz, B. C.; Jolly, M. R.

1996-01-01

427

Helicity of the solar magnetic field  

CERN Document Server

Helicity measures complexity in the field. Magnetic helicity is given by a volume integral over the scalar product of magnetic field {\\bf B} and its vector potential {\\bf A}. A direct computation of magnetic helicity in the solar atmosphere is not possible due to unavailability of the observations at different heights and also due to non-uniqueness of {\\bf A}. The force-free parameter $\\alpha$ has been used as a proxy of magnetic helicity for a long time. We have clarified the physical meaning of $\\alpha$ and its relationship with the magnetic helicity. We have studied the effect of polarimetric noise on estimation of various magnetic parameters. Fine structures of sunspots in terms of vertical current ($J_z$) and $\\alpha$ have been examined. We have introduced the concept of signed shear angle (SSA) for sunspots and established its importance for non force-free fields. We find that there is no net current in sunspots even in presence of a significant twist, showing consistency with their fibril-bundle nature...

Tiwari, Sanjiv Kumar

2010-01-01

428

The magnetic fields of hot subdwarf stars  

CERN Document Server

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

429

Electron Beam Therapy with Transverse Magnetic Fields  

International Nuclear Information System (INIS)

Detailed Monte Carlo electron transport calculations were carried out for the purpose of investigating the possibility of improving electron dose distributions for therapeutic applications by using transverse magnetic fields. The effect of a transverse magnetic field in and near the ''volume of interest'' causes the electrons to spiral in this region thus producing an effective peak in the depth-dose distribution within the tumor volume. An important aspect of this process is the attainment of a rapid dose fall-off with increasing penetration depth a well a considerable ''skin sparing''. Although work on this topic has been conducted in the past (1), the authors believe that with the advent of powerful computational platforms as well as with advances in the production of intense magnetic fields, it is very beneficial to re-address this important topic, especially in the light of the results obtained by the present authors (2)

430

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

431

Euclidean resonance in a magnetic field  

International Nuclear Information System (INIS)

An analogy is found between Wigner resonant tunneling and tunneling across a static potential barrier in a static magnetic field. Whereas in the process of Wigner tunneling an electron encounters a classically allowed region where a discrete energy level coincides with its energy, in the magnetic field the potential barrier is constant in the direction of tunneling. Along the tunneling path, certain regions are formed where, in the classical language, the kinetic energy of the motion perpendicular to tunneling is negative. These regions play the role of potential wells, where a discrete energy level can coincide with the electron energy. This phenomenon, which occurs at a certain magnetic field, is called Euclidean resonance and substantially depends on the shape of the potential forces in the direction perpendicular to tunneling. Under conditions of Euclidean resonance, a long-distance underbarrier motion is possible, which can be observed in experiments

432

Magnetic field gradiometer with trimming element  

International Nuclear Information System (INIS)

A magnetic field gradiometer includes a pair of coils, encompassing different regions of space. A SQUID is provided to detect a difference in flux linking the coils thereby to provide a measure of a magnetic field gradient between the coils. A control element of a superconducting material is provided in the vicinity of the coils and a heater is controlled to vary the proportion of the element assuming the superconducting state. By suitably varying this proportion the balance condition of the coils can be altered. The control element may operate in a feed back circuit. A coil subjects both coils to an alternating magnetic field at a preset frequency. A component in the output of the SQUID having this frequency is used to control the heater

433

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

434

Electron beam dynamics in cusped magnetic fields  

International Nuclear Information System (INIS)

The electron beam quality is a critical parameter in microwave tubes. A compact and high-power microwave amplifier is under development based on the cusptron concept which utilizes the negative-mass instability of an axis-rotating electron beam either in circular or multivane circuits. Through a series of recent experiments using a low-energy, axis-rotating beam, the NSWC cusptron oscillator has produced microwave radiation at fundamental and harmonic cyclotron frequencies in either a circular or a multivane circuit. For the production of an axis-rotating beam in cusptrons, a cusped magnetic field is used into which an annual beam is injected. In a non-ideal cusped magnetic field, one should take into account the coherent and incoherent off-centering effects for electron trajectories. Both effects result in beam broadening. In this paper, the authors present an experimental study of electron dynamics in a cusped magnetic field and its comparison with theory including computer simulations

435

Bound states in a strong magnetic field  

Energy Technology Data Exchange (ETDEWEB)

We expect a strong magnetic field to be produced in the perpendicular direction to the reaction plane, in a noncentral heavy-ion collision . The strength of the magnetic field is estimated to be eB{approx}m{sup 2}{sub {pi}}{approx} 0.02 GeV{sup 2} at the RHIC and eB{approx} 15m{sup 2}{sub {pi}}{approx} 0.3 GeV{sup 2} at the LHC. We investigate the effects of the magnetic field on B{sup 0} and D{sup 0} mesons, focusing on the changes of the energy levels and of the mass of the bound states.

Machado, C. S.; Navarra, F. S.; Noronha, J.; Oliveira, E. G. [Instituto de Fisica, Universidade de Sao Paulo Rua do Matao, Travessa R, 187, 05508-090 Sao Paulo, SP (Brazil); Ferreira Filho, L. G. [Departamento de Matematica e Computacao, Faculdade de Tecnologia, Universidade do Estado do Rio de Janeiro Rodovia Presidente Dutra, km 298, Polo Industrial, CEP 27537-000, Resende, RJ (Brazil)

2013-03-25

436

Coulomb drag in intermediate magnetic fields  

CERN Document Server

We investigated theoretically the Coulomb drag effect in coupled 2D electron gases in a wide interval of magnetic field and temperature $ 1/\\tau \\ll $\\tau$ being intralayer scattering time, $ømega_c$ being the cyclotron frequency. We show that the quantization of the electron spectrum leads to rich parametric dependences of drag transresistance on temperature and magnetic field. This is in contrast to usual resistance. New small energy scales are found to cut typical excitation energies to values lower than temperature. This may lead to a linear temperature dependence of transresistance even in a relatively weak magnetic field and can explain some recent experimental data. We present a novel mechanism of Coulomb drag when the current in the active layer causes a magnetoplasmon wind and the magnetoplasmons are absorbed by the electrons of the passive layer providing a momentum transfer. We derived general relations that describe the drag as a result of resonant tunneling of magnetoplasmons.

Khaetskii, A V; Nazarov, Yuli V.

1999-01-01

437

The Origin of Astrophysical Magnetic Fields  

CERN Document Server

We review the literature concerning how the cosmic magnetic fields pervading nearly all galaxies actually got started. some observational evidence involves the chemical abundance of the light elements Be and B, while another one is based on strong magnetic fields seen in high red shift galaxies. Seed fields, whose strength is of order 10^{-20} gauss, easily sprung up in the era preceding galaxy formation. Several mechanisms are proposed to amplify these seed fields to microgauss strengths. The standard mechanism is the Alpha-Omega dynamo theory. It has a major difficulty that makes unlikely to provide the sole origin. The difficulty is rooted in the fact that the total flux is constant. This implies that flux must be removed from the galactic discs. This requires that the field and flux be separated, for otherwise interstellar mass must be removed from the deep galactic gravitational and then their strength increased by the alpha omega theory.

Kulsrud, Russell M

2007-01-01

438

Manifestations of the Galactic Center Magnetic Field  

CERN Document Server

Several independent lines of evidence reveal that a relatively strong and highly ordered magnetic field is present throughout the Galaxy's central molecular zone (CMZ). The field within dense clouds of the central molecular zone is predominantly parallel to the Galactic plane, probably as a result of the strong tidal shear in that region. A second magnetic field system is present outside of clouds, manifested primarily by a population of vertical, synchrotron-emitting filamentary features aligned with the field. Whether or not the strong vertical field is uniform throughout the CMZ remains undetermined, but is a key central issue for the overall energetics and the impact of the field on the Galactic center arena. The interactions between the two field systems are considered, as they are likely to drive some of the activity within the CMZ. As a proxy for other gas-rich galaxies in the local group and beyond, the Galactic center region reveals that magnetic fields are likely to be an important diagnostic, if no...

Morris, Mark R

2014-01-01

439

Chaotic magnetic field line in toroidal plasmas  

International Nuclear Information System (INIS)

This is an introductory review of chaotic magnetic field line in plasmas, together with some new results, with emphasis on the long-time tail and the fractional Brownian motion of the magnetic field line. The chaotic magnetic field line in toroidal plasmas is a typical chaotic phenomena in the Hamiltonian dynamical systems. The onset of stochasticity induced by a major magnetic perturbation is thought to cause a macroscopic rapid phenomena called the current disruption in the tokamak discharges. Numerical simulations on the basis of magnetohydrodynamics reveal in fact the disruptive phenomena. Some dynamical models which include the area-preserving mapping such as the standard mapping, and the two-wave Hamiltonian system can model the stochastic magnetic field. Theoretical results with use of the functional integral representation are given regarding the long-time tail on the basis of the radial twist mapping. It is shown that application of renormalization group technique to chaotic orbit in the two-wave Hamiltonian system proves decay of the velocity autocorrelation function with the power law. Some new numerical results are presented which supports these theoretical results. (author)

440

Breached superfluidity of fermionic atoms in magnetic field  

OpenAIRE

We derived the energy gap of a breached pairing superfluidity phase of fermionic atoms in an external magnetic field in Feshbach resonance experiments which is determined by the magnetic - field detuning from the Feshbach resonance. We show that a BCS superfluid state exists only for the magnetic - field detuning smaller than one critical, and this critical magnetic - field detuning is determined by the equality of the Zeeman energy splitting for the magnetic - field detunin...

Genkin, G. M.

2005-01-01

441

Thomson scattering in a magnetic field. I - Field along z  

Science.gov (United States)

The Monte Carlo method is used here to solve the radiative transfer equation for Thomson scattering in a constant magnetic field perpendicular to the atmosphere. Emergent radiation and polarization are presented for various atmospheric thicknesses. The circular polarization peaks at frequencies near the cyclotron, omega(c), and for propagation direction along the field. At low field strengths, the circular polarization is roughly proportional to omega(c)/omega; the linear polarization is proportional to the square of omega(c)/omega and the amount of circular polarization present at each scatter and is therefore much smaller than the circular polarization. The linear polarization is large for propagation direction perpendicular to the magnetic field and at frequencies near the cyclotron and in the strong-field limit. The position angle of the linear polarization undergoes a rotation of 90 deg at a value of omega(c)/omega near the square root of three.

Whitney, Barbara A.

1991-01-01

442

Neutrino conversions in solar random magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

We consider the effect of a random magnetic field in the convective zone of the Sun super-imposed to a regular magnetic field on resonant neutrino spin-flavor oscillations. We argue for the existence of a field of strongly chaotic nature at the bottom of the convective zone. In contrast to previous attempts we employ a model motivated regular magnetic field profile: it is a static field solution to the solar equilibrium hydro-magnetic equations. These solutions have been known for a long time in the literature. We show for the first time that in addition they are twisting solutions. In this scenario electron antineutrinos are produced through cascades like {nu}{sub eL} {yields} {nu}{sub {mu}}{sub L} {yields} V-tilde{sub eR}, The detection of V-tilde{sub eR} at Earth would be a long-awaited signature of the Majorana nature of the neutrino. The expected signals in the different experiments (SK, GALLEX-SAGE, Homestake) are obtained as a function of the level of noise, regular magnetic field and neutrino mixing parameters. Previous results obtained for small mixing and ad-hoc regular magnetic profiles are reobtained. We confirm the strong suppression for a large part of the parameter space of the V-tilde{sub eR}-flux for high energy boron neutrinos in agreement with present data of the SK experiment. We find that MSW (Mikheyev-Smirnov-Wolfenstein) regions ({delta}m{sup 2} congruent with ]0{sup -5} eV{sup 2}, both small and large mixing solutions) are stable up to very large levels of noise (P = 0.7-0.8) but they are acceptable from the point of view of antineutrino production only for moderate levels of noise (P congruent with 0.95). For strong noise and a reasonable regular magnetic field, any parameter region ({delta}m{sup 2}, sin{sup 2} 2{theta}) is excluded. As a consequence, we are allowed to reverse the problem and to put limits on the r.m.s. field strength and transition magnetic moments by demanding a particle physics solution to the SNP in this scenario.

Semikoz, V.B. E-mail: semikoz@flamenco.ific.uv.es; Torrente-Lujan, E. E-mail: e.torrente@ceern.ch

1999-09-06

443

Helical magnetic fields via baryon asymmetry  

CERN Document Server

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

Piratova, Eduard F; Hortúa, Héctor J

2014-01-01

444

Highly Excited Molecules in Magnetic Fields  

Science.gov (United States)

Two-color resonance-enhanced multiphoton ionization (REMPI) spectra via a single Zeeman sublevel in the A state of gaseous nitric oxide (NO) were measured in magnetic fields, B, ranging from 0 ? B ? 10 T to observe the magnetic field effects on electronic states near the ionization potential (IP). It was found that new resonance appears above the IP for B ? 4 T. By using a semi-classical calculation, this resonance was assigned to the quasi-Landau resonance, which was observed for the first time in molecules.

Takazawa, K.

2005-07-01

445

Neutrino conversions in solar random magnetic fields  

International Nuclear Information System (INIS)

We consider the effect of a random magnetic field in the convective zone of the Sun super-imposed to a regular magnetic field on resonant neutrino spin-flavor oscillations. We argue for the existence of a field of strongly chaotic nature at the bottom of the convective zone. In contrast to previous attempts we employ a model motivated regular magnetic field profile: it is a static field solution to the solar equilibrium hydro-magnetic equations. These solutions have been known for a long time in the literature. We show for the first time that in addition they are twisting solutions. In this scenario electron antineutrinos are produced through cascades like ?eL ? ??L ? V-tildeeR, The detection of V-tildeeR at Earth would be a long-awaited signature of the Majorana nature of the neutrino. The expected signals in the different experiments (SK, GALLEX-SAGE, Homestake) are obtained as a function of the level of noise, regular magnetic field and neutrino mixing parameters. Previous results obtained for small mixing and ad-hoc regular magnetic profiles are reobtained. We confirm the strong suppression for a large part of the parameter space of the V-tildeeR-flux for high energy boron neutrinos in agreement with present data of the SK experiment. We find that MSW (Mikheyev-Smirnov-Wolfenstein) regions (?m2 congruent with ]0-5 eV2, both small and large mixing solutions) are stable urge mixing solutions) are stable up to very large levels of noise (P = 0.7-0.8) but they are acceptable from the point of view of antineutrino production only for moderate levels of noise (P congruent with 0.95). For strong noise and a reasonable regular magnetic field, any parameter region (?m2, sin2 2?) is excluded. As a consequence, we are allowed to reverse the problem and to put limits on the r.m.s. field strength and transition magnetic moments by demanding a particle physics solution to the SNP in this scenario

446

Reduction of a Ship's Magnetic Field Signatures  

CERN Document Server

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

447

Homogeneous viscous universes with magnetic field  

International Nuclear Information System (INIS)

In this thesis homogeneous universes are studied containing a large scale magnetic field. In the evolution three different phases are distinguished: the lepton, the plasma and the matter dominated eras. During the lepton and plasma eras, which form the radiation dominated phase, the material contents of the universe are taken to consist of a viscous fluid. The transport properties taking place during this radiation dominated period are described with the help of relativistic kinetic theory, thereby taking into account the effect of the magnetic field on the shear viscosity. In the matter dominated phase the contents of the universe mainly consists of dust and, therefore, viscosity is absent during this period. (Auth.)

448

Magnetic resonance imaging without field cycling at less than earth's magnetic field  

Science.gov (United States)

A strong pre-polarization field, usually tenths of a milli-tesla in magnitude, is used to increase the signal-to-noise ratio in ordinary superconducting quantum interference device-based nuclear magnetic resonance/magnetic resonance imaging experiments. Here, we introduce an experimental approach using two techniques to remove the need for the pre-polarization field. A dynamic nuclear polarization (DNP) technique enables us to measure an enhanced resonance signal. In combination with a ? / 2 pulse to avoid the Bloch-Siegert effect in a micro-tesla field, we obtained an enhanced magnetic resonance image by using DNP technique with a 34.5 ?T static external magnetic field without field cycling. In this approach, the problems of eddy current and flux trapping in the superconducting pickup coil, both due to the strong pre-polarization field, become negligible.

Lee, Seong-Joo; Shim, Jeong Hyun; Kim, Kiwoong; Yu, Kwon Kyu; Hwang, Seong-min

2015-03-01

449

Exploring the origin of magnetic fields in massive stars: II. New magnetic field measurements in cluster and field stars  

OpenAIRE

Theories on the origin of magnetic fields in massive stars remain poorly developed, because the properties of their magnetic field as function of stellar parameters could not yet be investigated. To investigate whether magnetic fields in massive stars are ubiquitous or appear only in stars with a specific spectral classification, certain ages, or in a special environment, we acquired 67 new spectropolarimetric observations for 30 massive stars. Among the observed sample, r...

Hubrig, S.; Schoeller, M.; Ilyin, I.; Kharchenko, N. V.; Oskinova, L. M.; Langer, N.; Gonzalez, J. F.; Kholtygin, A. F.; Briquet, M.; Collaboration, The Magori

2013-01-01

450

The Aurora and Magnetic Field of Uranus  

Science.gov (United States)

Resolution of the details of a planetary magnetic field from magnetometer measurements made during a single flyby can be limited by the incomplete geometrical sampling of the trajectory. This problem was especially severe for the only spacecraft visit to Uranus, that of Voyager 2 in 1986. Fortunately, auroral footprints serve as additional constraints that may be used to determine the higher multipole moments of the planetary field. This approach has been used by Connerney (JGR 103:11,929, 1998) to improve the magnetic field model of Jupiter. In the present work, this approach is applied to improving the resolution of the magnetic field of Uranus. The earlier determination of Uranus' auroral emission distribution (Herbert JGR 99:4143, 1994) from scans by the Voyager 2 Ultraviolet Spectrometer (UVS) has been improved by incorporating more observations and using more powerful analysis techniques. However, the resulting new estimate of the locus of the auroral oval does not match the expectations derived from the Voyager magnetometer (Connerney et al., JGR 92:15,329, 1987, Q3 model). Accordingly, a search has been initiated for planetary magnetic field model coefficients that agree both with the new auroral locus and also with the magnetic field observations. This search is more ambiguous than that at Jupiter, because the source of the aurora is not clearly defined, but a reasonable starting assumption is that it lies at constant L shell (maximum field-line distance from Uranus). Based on this assumption, preliminary results confirm the Q3 model quadrupole moment's large magnitude but disagree slightly with its orientation. Further analysis will be presented at the meeting. Support from the NASA Outer Planets Program made this work possible, and is gratefully acknowledged. Part of this work was done while a guest investigator at l'Institut d'Astrophysique de Paris (IAP/CNRS), whose hospitality is appreciated.

Herbert, F.

2008-12-01

451

The National High Magnetic Field Laboratory  

Science.gov (United States)

The National High Magnetic Field Laboratory (NHMFL) is a collaboration between Florida State University, the University of Florida, and the Los Alamos National Laboratory. The DC Field Facilities are located at the main campus for the NHMFL in Tallahassee, Florida and are described in this paper. The DC Field Facility has a variety of resistive and superconducting magnets. The DC Field Facility infrastructure, the most powerful in the world, is able to provide 57 MW of continuous low noise DC power. Constant magnetic fields of up to 45 tesla in a 32 mm bore and 20 tesla in 195 mm bore are available at no charge to the user community. The users of the facility are selected by a peer reviewed process. Roughly 400 research groups visit the lab to conduct experiments each year. Experimental capabilities provided by the NHMFL are magneto-optics, millimeter wave spectroscopy, magnetization, dilatometry, specific heat, electrical transport, ultrasound, low to medium resolution NMR, EMR, and materials processing. Measurements of properties can be made on samples at temperatures from 20 mK to 1000 K, pressures from ambient to 10 GPa, orientation and currents from 1 pA to 10 kA.

Hannahs, S. T.; Palm, E. C.

2010-04-01

452

Magnetic Fields in an Expanding Universe  

CERN Document Server

We find a solution to $4D$ Einstein-Maxwell theory coupled to a massless dilaton field describing a Melvin magnetic field in an expanding universe with 'stiff matter' equation of state parameter $w=+1$. As the universe expands, magnetic flux becomes more concentrated around the symmetry axis for dilaton coupling $a1/\\sqrt{3}$. An electric field circulates around the symmetry axis in the direction determined by Lenz's law. For $a=0$ the magnetic flux through a disk of fixed comoving radius is proportional to the proper area of the disk. This result disagrees with the usual expectation based on a test magnetic field that this flux should be constant, and we show why this difference arises. We also find a Melvin solution in an accelerating universe with $w=-7/9$ for a dilaton field with a certain exponential potential. Our main tools are simple manipulations in $5D$ Kaluza-Klein theory and related solution generating techniques. We also discuss a number of directions for possible extensions of this work.

Kastor, David

2013-01-01

453

The magnetic fields of hot subdwarf stars  

Science.gov (United States)

Context. 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. The situation concerning the occurrence and frequency of magnetic fields in hot subdwarfs is at best confused. Aims: 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. Methods: 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. Results have been published for only about half of the hot subdwarfs observed with FORS. Here we present new FORS1 field measurements for 17 stars, 14 of which have never been observed for magnetic