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1

Plasma Confinement in a Toroidal Octupole Magnetic Field  

International Nuclear Information System (INIS)

The confinement of low-density (n = 109 cm-3) collisionless plasmas with Ti ? 40 eV, Te ? 10 eV produced by gun injection or with Te ? 1 eV. Ti -3of the Bohm diffusion coefficient which was not large enough to produce the observed radial loss. Studies were also made to determine the importance of low-frequency fluctuations or convective cells which may have been produced by injection, magnetic field perturbations or azimuthal density variations. The addition of a toroidal magnetic field decreased the lifetime slightly and generated large-scale convective cells in the shearless layer near the plasma surface. Currents parallel to the magnetic field have been observed which must be considered in determining the cause of increased fluctuation with the increase of the toroidal field. The mechanical supports were also guarded with magnetic dipoles in the manner proposed by Lehnert. The plasma flux to one of the supports was reduced for the hot ion plasma by an order of magnitude when there was one ion gyroradius between the mechanical support and the guard field separatrix. However, the plasma flux along the guard field separatrix increased to the value of the original support flux and there was a negligible ( ? 20%) improvement of the lifetime. An inductively excited, magnetically force-free octupole is being assembled with transiently withdrawn supports to eliminate the plasma loss to hoop supports. The device will provide at least 10 msec of experimental time during which only 5% of the magnetic flux diffuses into the internal hoops. 100 eV protons will have 15 gyroradii on each side of the separatrix. (author)

2

Toroidal discharges in an octupole field  

International Nuclear Information System (INIS)

Experimental results from the Extrap T1 device are reported. The Extrap T1 machine has a toroidal stainless steel below vessel, R/a=0.5/0.06 m, covered with a segmented shell. A special character of the device is a coil system which produces an octupole magnetic field. The application of the octupole field produce an equilibrium with four poloidal field nulls. Three modes of operation are considered; 1) toroidal field only, 2) toroidal field and octupole field, 3) octupole field only. The purpose of the present experiment was to study the effect of the octupole field. (author) 4 refs., 5 figs

3

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

4

Magnetic octupole scattering of neutrons  

International Nuclear Information System (INIS)

The cross section for the magnetic octupole scattering of neutrons by rare-earth ions is estimated. These scattering events can change the magnetic quantum number of the ions by up to three units. For high momentum transfers and a proper scattering geometry, the cross sections for magnetic octupole modular ?M = 2 and 3 transitions are comparable with those for magnetic dipole modulus ?M = 1 transitions. If a beam of polarized neutrons is used, modulus ?M 2 excitations, i.e. quadrupolar waves, can be produced without exciting spin waves modulus ?M = 1. Examples are quoted where this scattering is expected to be of particular interest. (author)

5

Spectroscopy on a single trapped ¹³?Ba? ion for nuclear magnetic octupole moment determination.  

Science.gov (United States)

We present precision measurements of the hyperfine intervals in the 5D3/2 manifold of a single trapped Barium ion, ¹³?Ba?. Measurements of the hyperfine intervals are made between mF = 0 sublevels over a range of magnetic fields allowing us to interpolate to the zero field values with an accuracy below a few Hz, an improvement on previous measurements by three orders of magnitude. Our results, in conjunction with theoretical calculations, provide a 30-fold reduction in the uncertainty of the magnetic dipole (A) and electric quadrupole (B) hyperfine constants. In addition, we obtain the magnetic octupole constant (C) with an accuracy below 0.1Hz. This gives a subsequent determination of the nuclear magnetic octupole moment, ?, with an uncertainty of 1% limited almost completely by the accuracy of theoretical calculations. This constitutes the first observation of the octupole moment in ¹³?Ba? and the most accurately determined octupole moment to date. PMID:23037261

Lewty, Nicholas C; Chuah, Boon Leng; Cazan, Radu; Sahoo, B K; Barrett, M D

2012-09-10

6

Beam-Profile Control Using an Octupole Magnet  

Science.gov (United States)

For medical irradiation, beams with a uniform distribution have been required. We have proposed a method to control the beam profile using an octupole magnet. We have installed an octupole magnet and confirmed its effectiveness at the Heavy Ion Medical Accelerator in Chiba (HIMAC) beam-transport line. A beam efficiency of 91% can be realized with a flatness of ±4% over the range of ±15 mm. The beam offset at the position of the octupole magnet is required to be within ±0.2 mm to realize this condition. This method is expected to have a beam efficiency higher than that of the ordinary method using wobbler magnets and a scatterer system.

Urakabe, Eriko; Fujita, Yuzo; Hiramoto, Kazuo; Inoue, Makoto; Iwashita, Yoshihisa; Kanazawa, Mitsutaka; Morita, Akio; Nishi, Masatsugu; Norimine, Tetsuro; Noda, Akira; Noda, Koji; Ogawa, Hirotsugu; Shirai, Toshiyuki; Torikoshi, Masami; Umezawa, Masumi; Yamada, Satoru

1999-10-01

7

Beam-profile control using an octupole magnet  

Energy Technology Data Exchange (ETDEWEB)

For medical irradiation, beams with a uniform distribution have been required. We have proposed a method to control the beam profile using an octupole magnet. We have installed an octupole magnet and confirmed its effectiveness at the Heavy Ion Medical Accelerator in Chiba (HIMAC) beam-transport line. A beam efficiency of 91% can be realized with a flatness of {+-}4% over the range of {+-}15 mm. The beam offset at the position of the octupole magnet is required to be within {+-}0.2 mm to realize this condition. This method is expected to have a beam efficiency higher than that of the ordinary method using wobbler magnets and a scatterer system. (author)

Urakabe, Eriko [Nuclear Science Research Facility, ICR, Kyoto University, Uji, Kyoto (Japan); Fujita, Yuzo; Hiramoto, Kazuo (and others)

1999-10-01

8

Beam-profile control using an octupole magnet  

International Nuclear Information System (INIS)

For medical irradiation, beams with a uniform distribution have been required. We have proposed a method to control the beam profile using an octupole magnet. We have installed an octupole magnet and confirmed its effectiveness at the Heavy Ion Medical Accelerator in Chiba (HIMAC) beam-transport line. A beam efficiency of 91% can be realized with a flatness of ±4% over the range of ±15 mm. The beam offset at the position of the octupole magnet is required to be within ±0.2 mm to realize this condition. This method is expected to have a beam efficiency higher than that of the ordinary method using wobbler magnets and a scatterer system. (author)

9

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

10

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

11

Spectroscopy on a single trapped 137Ba+ ion for nuclear magnetic octupole moment determination  

CERN Document Server

We present precision measurements of the hyperfine splittings in the 5D3/2 manifold of a single trapped Barium ion, 137Ba+ . Measurements of the hyperfine splittings are made between mF = 0 sublevels over a range of magnetic fields allowing us to interpolate to the zero field splittings with an accuracy below 10 Hz. Our results, in conjunction with theoretical calculations, allow the determination of the hyperfine coupling constant, C, with an accuracy below 0.1 Hz. This gives a subsequent determination of the nuclear magnetic octupole moment with an uncertainty limited almost completely by the accuracy of theoretical calculations.

Lewty, Nicholas C; Cazan, Radu; Barrett, M D

2012-01-01

12

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

13

A Comparison of Two Magnetic Ultra-Cold Neutron Trapping Concepts Using a Halbach-Octupole Array  

Science.gov (United States)

This paper describes a new magnetic trap for ultra-cold neutrons (UCNs) made from a 1.2m long Halbach-octupole array of permanent magnets with an inner bore radius of 47mm 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.; Ivanov, S.; Martin, F.; Rosenau, F.; Simson, M.; Zimmer, O.

2014-03-01

14

Octupole deformation properties of actinide isotopes within a mean field approach  

CERN Document Server

We discuss the octupole deformation properties of many even-even actinide isotopes. The analysis is carried out in the mean field framework (Hartree-Fock-Bogoliubov approximation) by using the axially symmetric octupole moment as a constraint. A one-dimensional octupole collective Hamiltonian is used to obtain properties like excitation energies or $E1$ and $E3$ transition probabilities of the negative parity band-heads associated to the lowest lying $1^{-}$ and $3^{-}$ states. The evolution of these values with neutron number is discussed and a comparison with available experimental data is made. In order to minimize the uncertainties associated to the energy density functional used, the calculations have been carried out for an assorted set ranging from the BCP1 functional to the finite range Gogny interaction with the D1S, D1N and D1M parametrization.

Robledo, L M; 10.1088/0954-3899/39/10/105103

2012-01-01

15

Octupole deformation properties of actinide isotopes within a mean-field approach  

Science.gov (United States)

We discuss the octupole deformation properties of many even-even actinide isotopes. The analysis is carried out in the mean-field framework (Hartree-Fock-Bogoliubov approximation) by using the axially symmetric octupole moment as a constraint. A one-dimensional octupole collective Hamiltonian is used to obtain properties such as excitation energies or the E1 and E3 transition probabilities of the negative-parity band-heads associated with the lowest lying 1- and 3- states. The evolution of these values with neutron number is discussed and a comparison with available experimental data is made. In order to minimize the uncertainties associated with the energy density functional used, the calculations have been carried out for an assorted set ranging from the BCP1 functional to the finite-range Gogny interaction with the D1S, D1N and D1M parametrization.

Robledo, L. M.; Rodríguez-Guzmán, R. R.

2012-10-01

16

Towards a measurement of the nuclear magnetic octupole moment of barium-137  

Science.gov (United States)

A 2051 rim wavelength laser system designed and built for use in a number of proposed experiments is presented. The laser is shown to have a sub-kilohertz linewidth. Results of spectroscopic measurements of the 6S1/2 to 5D3/2 transition in 138Ba + are discussed. A proposed measurement of the nuclear magnetic octupole measurement of 137Ba is reviewed. The prospects for developing this laser system into a barium ion optical frequency standard are discussed.

Kleczewski, Adam

17

NUCLEAR PHYSICS: Octupole Deformations of Even-Even Rn, Th, and U Nuclei in Relativistic Mean Field Theory  

Science.gov (United States)

The octupole deformations and other ground state properties of even-even Rn, Th and U isotopes are investigated systematically within the framework of the reflection asymmetric relativistic mean field (RAS-RMF) model. The calculation results reproduce the binding energies and the quadrupole deformations well. The calculation results indicate these nuclei at ground states evolve from nearly-spherical (N = 130) shape to quadrupole deformation shape with the increase of the neutron number. It is also found that among the Rn isotopes, only 222,224Rn are octupole deformed and the octupole deformations for them are small. However, more nuclei (N notsimeq 134-148) in Th and U isotopes are octupole deformed and the octupole deformations for some of them are significant (|?3| ~ 0.1 or even larger).

Wang, Nan; Meng, Jie; Zhao, En-Guang

2010-06-01

18

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

CERN Document Server

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

Leung, Kent

2008-01-01

19

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

International Nuclear Information System (INIS)

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

20

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

 
 
 
 
21

Ambipolar electric fields and turbulence studies in the Wisconsin levitated toroidal octupole  

Energy Technology Data Exchange (ETDEWEB)

Detailed studies of hot ion plasmas (T/sub i/ > T/sub e/) in the poloidal field octupole show that the ambipolar electric field which is perpendicular to the flux surfaces is well explained by the observed properties of the microturbulence structures in the plasma. The turbulence structure has been measured by correlation techniques which are carefully described. In these experiments, signals were studied which are aperiodic in time and space, short lived compared to the decay times of the bulk plasma parameters, short ranged compared to the machine size, and are therefore classified as microturbulence structures. The resulting spatial and temporal correlation functions (CFs) are well fitted to a Gaussian function and the associated correlation lengths or times are the half width at half maximum of the CFs. The correlation length is measured to be the ion gyro radius for the hot hydrogen plasma and somewhat less for the helium plasma.

Armentrout, C.J.

1977-01-01

22

Electric quadrupole and magnetic octupole moments of the light decuplet baryons within light cone QCD sum rules  

International Nuclear Information System (INIS)

The electric quadrupole and magnetic octupole moments of the light decuplet baryons are calculated in the framework of the light cone QCD sum rules. The obtained non-vanishing values for the electric quadrupole and magnetic octupole moments of these baryons show nonspherical charge distribution. The sign of electric quadrupole moment is positive for ?-, ?*-, ?*- and negative for ?*+, which correspond to the prolate and oblate charge distributions, respectively. A comparison of the obtained results with the predictions of non-covariant quark model which shows a good consistency between two approaches is also presented. Comparison of the obtained results on the multipole moments of the decuplet baryons containing strange quark with those of ? baryons shows a large SU(3) flavor symmetry breaking.

23

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

24

Towards a Measurement of the Nuclear Magnetic Octupole Moment of ^137Ba  

Science.gov (United States)

Measurements of hyperfine structure in a ^133Cs atom resolved a nuclear magnetic octupole moment, ?, much larger than expected.ootnotetextV. Gerginov, A. Derevianko, and C. E. Tanner, Phys. Rev. Lett. 91, 072501 To explore this anomaly further, we are undertaking an experiment to measure the hyperfine structure of the 5D levels of ^137Ba. We will selectively populate the m=0 states in the 5D3/2 manifold by driving the 6S1/2 to 5D3/2 electric quadrupole transition using a commercially available Tm,Ho:YLF laser. Using the Pound-Drever-Hall frequency stabilization method we locked this laser to a high finesse cavity made of ULE glass and demonstrated a laser linewidth of less than 750 Hz. Once the barium ion is initialized to an m=0 state of a chosen 5D3/2 hyperfine sublevel, we will perform RF spectroscopy to measure the hyperfine splittings with mHz precision. A measurement the 5D3/2 hyperfine intervals combined with a similar measurement of the 5D5/2 hyperfine intervals (using a 1762 nm fiber laser) will allow theorists to extract a value for ?.

Hoffman, Matthew; Kleczewski, Adam; Magnuson, Eric; Fortson, E. N.; Blinov, Boris

2011-06-01

25

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

26

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

International Nuclear Information System (INIS)

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

27

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

28

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

29

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

30

Experimental determination of the nuclear magnetic octupole moment of $^{137}$Ba$^+$ ion  

CERN Document Server

We perform precision measurements on the 5D$_{5/2}$ manifold hyperfine intervals of a single trapped ion, $^{137}$Ba$^+$. RF spectroscopy is used to measure the hyperfine intervals to an accuracy of a few Hz. Our results provide a three orders of magnitude improvement in accuracy over previous work and also provide a 10-fold improvement in the value of $g_J$ for this level. These results complement our previous work on the 5D$_{3/2}$ manifold of $^{137}$Ba$^+$, providing an independent measurement of the nuclear octupole, and a consistency check on atomic structure calculations.

Lewty, Nicholas C; Cazan, Radu; Sahoo, B K; Barrett, M D

2013-01-01

31

Measurement and prediction of the speed-dependent throughput of a magnetic octupole velocity filter including nonadiabatic effects  

International Nuclear Information System (INIS)

A magnetic octupole filter set in a 90 degree sign curve produces ?108 cold Rb atoms/s by filtering low-velocity particles from a thermal source. We measure the speed distribution of Rb exiting the filter to be 3.5 K using a Rydberg-atom time-of-flight scheme in which Rb is excited via the process 5s 2S1/2?5p 2P3/2o?32d 2D. We develop a general theory of the transmission and speed distribution of particles emitted from such a source including nonadiabatic effects. A detailed Monte Carlo simulation using the theory accurately reproduces the experimental results. We show that for Cs, Li, and Rb atoms and S2 molecules, nonadiabatic effects do not dramatically effect the performance of the filter, and that the output flux temperatures for a wide variety of filter configurations are well fit to a simple functional form

32

Spectroscopy on a single trapped 137Ba+ ion for nuclear magnetic octupole moment determination  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present precision measurements of the hyperfine intervals in the 5D3/2 manifold of a single trapped Barium ion, 137 Ba+ . Measurements of the hyperfine intervals are made between mF = 0 sublevels over a range of magnetic fields allowing us to interpolate to the zero field values with an accuracy below a few Hz, an improvement on previous measurements by three orders of magnitude. Our results, in conjunction with theoretical calculations, provide a 30-fold reduction in the...

Lewty, Nicholas C.; Chuah, Boon Leng; Cazan, Radu; Sahoo, B. K.; Barrett, M. D.

2012-01-01

33

Interference corrections of the second Born approximation to the elastic scattering cross section of electron by the nuclei with magnetic octupole moment  

International Nuclear Information System (INIS)

The correction of the second Born approximation to the cross section of elastic back scattering of electrons (TyETA=?) by nuclei possessing electric quadrupole and magnetic dipole and octupole moments taking into account the interference contributions between charged and magnetic scatterings. The correction behaviour is investigated in the case of 1p-shell (9Be, 11B) nuclei. Analytic expressions are obtained for corrections in the limits of not very high energies of incident electrons

34

The main magnetic field of Jupiter  

International Nuclear Information System (INIS)

The main magnetic field of Jupiter has been measured by the Goddard Space Flight Center flux gate magnetometer on Pioneer 11, and analysis of the data yields a more detailed model than that obtained from Pioneer 10 results. In a spherical harmonic octupole representation the dipole term (with opposite polarity to earth's) has a magnitude of 4.28 G R/sub j/ 3 at a tilt angle of 9.6degree and a system III longitude of 232degree. The quadrupole and octupole moments are significant, 24% and 21% of the dipole, respectively. This leads to a significant deviation of the planetary magnetic field from a simple offset dipole topology at distances of <3R/sub j/. The north polar field strength is 14 G, and in the northern hemisphere the 'footprint' of the lo associated flux tube traverses the magnetic polar region. Associated L shell splitting in the radiation belts, warping of the charged particle equatorial planes, and enhanced absorption effects due to the satellites Amalthea and lo are expected as a result of the field complexity

35

Observation of hyperfine mixing in measurements of a magnetic octupole decay in isotopically pure nickel-like 129Xe and 132Xe ions  

Energy Technology Data Exchange (ETDEWEB)

We present measurements of high statistical significance of the rate of the magnetic octupole (M3) decay in nickel-like ions of isotopically pure {sup 129}Xe and {sup 132}Xe. On {sup 132}Xe, an isotope with zero nuclear spin and therefore without hyperfine structure, the lifetime of the metastable level was established as (15.06 {+-} 0.24) ms. On {sup 129}Xe, an additional fast (2.7 {+-} 0.1 ms) decay component was established that represents hyperfine mixing with a level that decays by electric quadrupole (E2) radiation.

Trabert, E; Beiersdorfer, P; Brown, G V

2006-12-21

36

Multiparticle-octupole coupling and magnetic moments of h9/2n isomers in N=126 isotones  

International Nuclear Information System (INIS)

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

37

Influence of Nekhoroshev's criterion on dynamical aperture of circular accelerator with octupole lenses families  

International Nuclear Information System (INIS)

Soviet mathematician N.Nekhoroshev has shown that if the Hamiltonian of a system satisfies definite conditions (Nekhoroshev's criterion) then this system is stable (in Nekhoroshev's sense). This paper is devoted to study of Nekhoroshev's criterion influence on dynamical aperture (DA) of the ring including two families of octupole lenses for increase of betatron tunes spread and suppressing of transverse coherent instabilities. Two lattices have been designed: one lattice with strong modulation of beta-functions (which allows us to satisfy Nekhoroshev's criterion for octupole families) and the second lattice where this criterion is not satisfied. For both lattices the dependence of DA on octupole families current was calculated with account of systematic and random errors of magnetic field. The calculations have shown that for both lattices the DA is decreased with increase of the current; for the first lattice (where Nekhoroshev's criterion is satisfied) this effect is weaker than for the second one

38

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

39

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

40

Earth's Inconstant Magnetic Field  

Science.gov (United States)

This NASA site describes long-term changes in Earth's magnetic field, and how magnetic stripes in the Atlantic seafloor provide evidence for reversals of this field. The site presents a model of Earth's interior that helps explain how Earth's magnetic field is generated and how the reversals occur. A computer-generated image shows the complicated magnetic field in-between reversals.

2007-04-27

 
 
 
 
41

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,

42

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,

43

Cosmological Magnetic Fields  

CERN Document Server

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

Kunze, Kerstin E

2013-01-01

44

Low-degree Structure in Mercury's Planetary Magnetic Field  

Science.gov (United States)

The structure of Mercury's internal magnetic field has been determined from analysis of orbital Magnetometer measurements by the MESSENGER spacecraft. We identified the magnetic equator on 531 low-altitude and 120 high-altitude equator crossings from the zero in the radial cylindrical magnetic field component, Beta (sub rho). The low-altitude crossings are offset 479 +/- 6 km northward, indicating an offset of the planetary dipole. The tilt of the magnetic pole relative to the planetary spin axis is less than 0.8 deg.. The high-altitude crossings yield a northward offset of the magnetic equator of 486 +/- 74 km. A field with only nonzero dipole and octupole coefficients also matches the low-altitude observations but cannot yield off-equatorial Beta (sub rho) = 0 at radial distances greater than 3520 km. We compared offset dipole and other descriptions of the field with vector field observations below 600 km for 13 longitudinally distributed, magnetically quiet orbits. An offset dipole with southward directed moment of 190 nT-R-cube (sub M) yields root-mean-square (RMS) residuals below 14 nT, whereas a field with only dipole and octupole terms tuned to match the polar field and the low-altitude magnetic equator crossings yields RMS residuals up to 68 nT. Attributing the residuals from the offset-dipole field to axial degree 3 and 4 contributions we estimate that the Gauss coefficient magnitudes for the additional terms are less than 4% and 7%, respectively, relative to the dipole. The axial alignment and prominent quadrupole are consistent with a non-convecting layer above a deep dynamo in Mercury's fluid outer core.

Anderson, Brian J.; Johnson, Catherine L.; Korth, Haje; Winslow, Reka M.; Borovsky, Joseph E.; Purucker, Michael E.; Slavin, James A.; Solomon, Sean C.; Zuber, Maria T.; McNutt, Ralph L. Jr.

2012-01-01

45

Neutron star deformation due to multipolar magnetic fields  

Science.gov (United States)

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

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

2013-09-01

46

Design, fabrication and cold tests of a super ferric octupole corrector for the LHC  

International Nuclear Information System (INIS)

In the corrections scheme of the LHC it is planed to install octupole corrector magnets in the short straight section of the lattice. Initially these correctors were distributed windings on the cold bore tube nested in the tuning quadrupoles. The latter being suppressed a new compact super ferric design was chosen for the octupole prototype, suitable for a two-in-one configuration. This prototype was designed by CERN and CEDEX/Spain, built at INDAR/Spain and tested at CEDEX. The paper reports on the design of the prototype, describes the fabrication and assembly and presents the measurement results. Special interest has been taken to design a simple and compact magnet, easy to fabricate and training free below nominal field. First results show the feasibility of the solution wich will be finally confirmed by magnetic measurement. (Author) 4 refs

47

Design, fabrication and cold tests of a superferritic octupole corrector for the LHC  

International Nuclear Information System (INIS)

In the correction scheme of the LHC it is planned to install octupole corrector magnets in the short straight section of the lattice. Initially these correctors were distributed windings on the cold bore tube nested in the tuning quadrupoles. The latter being suppressed a new compact superferric design was chosen for the octupole prototype, suitable for a two-in-one configuration. This prototype was designed by CERN and CEDEX/Spain, built at INDAR/Spain and tested at CEDEX. The paper reports on the design of the prototype, describes the fabrication and assembly and presents the measurement results. Special interest has been taken to design a simple and compact magnet, easy to fabricate and training free below nominal field. First results show the feasibility of the solution which will be finally confirmed by magnetic measurements

48

Design, fabrication and cold tests of a superferritic octupole corrector for the LHC  

Energy Technology Data Exchange (ETDEWEB)

In the correction scheme of the LHC it is planned to install octupole corrector magnets in the short straight section of the lattice. Initially these correctors were distributed windings on the cold bore tube nested in the tuning quadrupoles. The latter being suppressed a new compact superferric design was chosen for the octupole prototype, suitable for a two-in-one configuration. This prototype was designed by CERN and CEDEX/Spain, built at INDAR/Spain and tested at CEDEX. The paper reports on the design of the prototype, describes the fabrication and assembly and presents the measurement results. Special interest has been taken to design a simple and compact magnet, easy to fabricate and training free below nominal field. First results show the feasibility of the solution which will be finally confirmed by magnetic measurements.

Laurent, G.; Russenschuck, S.; Siegel, N.; Traveria, M. [CERN, Geneva (Switzerland); Garcia-Tabares, L.; Calero, J. [CEDEX-MOPTMA, Madrid (Spain); Aguirre, P.; Etxeandia, J.; Garcia, J. [INDAR, Beasain (Spain)

1996-07-01

49

The Earth's Magnetic Field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Edda Lína Gunnarsdóttir 1988

2012-01-01

50

The Declining Magnetic Field  

Science.gov (United States)

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

51

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

52

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

53

Magnetic Fields in Stars  

Science.gov (United States)

Magnetism—the force that deflects the needle of a compass—and magnetic fields have been found in some hundreds of stars during the past 50 yr. Magnetic fields have been detected in T Tauri stars and other pre-main-sequence stars, several types of main sequence stars, white dwarfs and neutron stars. We now know a number of methods by which such magnetic fields may be detected, we are in the proces...

Landstreet, J.; Murdin, P.

2000-11-01

54

Plasma resistivity measurements in the Wisconsin levitated octupole  

Energy Technology Data Exchange (ETDEWEB)

Resistivity measurements parallel to the magnetic field were made on gun injected plasmas ranging in density from 10/sup 9/cm/sup -3/ to 10/sup 1/parallelcm/sup -3/ in the Wisconsin levitated octupole with toroidal and poloidal magnetic fields. The 10/sup 9/cm/sup -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 = ..sqrt..T/sub e//n/sub e/ when E/sub parallel/ > E/su c/ is the Dreicer critical field. The 10/sup 12/cm/sup -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/.

Brouchous, D. A.

1980-11-01

55

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/

56

A «tidal» magnetic field?  

Directory of Open Access Journals (Sweden)

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

F. Bocchio

1997-06-01

57

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.

Christian, Wolfgang; Belloni, Mario

2007-03-03

58

Photospheric magnetic fields  

Science.gov (United States)

Knowledge on the nature of magnetic fields on the solar surface is reviewed. At least a large part of the magnetic flux in the solar surface is confined to small bundles of lines of force within which the field strength is of the order of 500 gauss. Magnetic fields are closely associated with all types of solar activity. Magnetic flux appears at the surface at the clearly defined birth or regeneration of activity of an active region. As the region ages, the magnetic flux migrates to form large-scale patterns and the polar fields. Some manifestations of the large-scale distribution are discussed.

Howard, R.

1972-01-01

59

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.

60

Chromaticity dependence on octupole strength  

CERN Document Server

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

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

2012-01-01

 
 
 
 
61

Magnetic Field Tomography  

CERN Document Server

Neutral atoms may be trapped via the interaction of their magnetic dipole moment with magnetic field gradients. One of the possible schemes is the cloverleaf trap. It is often desirable to have at hand a fast and precise technique for measuring the magnetic field distribution. We introduce a novel diagnostic tool for instantaneous imaging the equipotential lines of a magnetic field within a region of space (the vacuum recipient) that is not accessible to massive probes. Our technique is based on spatially resolved observation of the fluorescence emitted by a hot beam of sodium atoms crossing a thin slice of resonant laser light within the magnetic field region to be investigated. The inhomogeneous magnetic field spatially modulates the resonance condition between the Zeeman-shifted hyperfine sublevels and the laser light and therefore the amount of scattered photons. We demonstrate this technique by mapping the field of our cloverleaf trap in three dimensions under various conditions.

Courteille, P W; Magalhães, K; Kaiser, R; Marcassa, L G; Bagnato, V S; Courteille, Ph. W.

2001-01-01

62

On Primordial Magnetic Fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

A primordial magnetic field could be responsible for the observed magnetic fields of the galaxies. One possibility is that such a primordial field is generated at the electroweak phase transition because of the fluctuations in the Higgs field gradients. I describe a statistical averaging procedure which gives rise to a field of a correct magnitude. Another possibility, where the Yang-Mills vacuum itself is ferrromagnetic, is also discussed.

Enqvist, Kari

1994-01-01

63

Primordial Magnetic Fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Enqvist, Kari

1998-01-01

64

Cosmological Magnetic Fields  

CERN Document Server

We discuss the evolution of cosmological magnetic fields from the early universe to the present. We review different scenarios for magnetogenesis in the early universe and follow the subsequent evolution of these fields as the universe recombines. We then focus on the role primordial fields play after recombination in the seeding of stellar and galactic fields and the formation of structure. Cosmological magnetic fields in the intergalactic medium trace the turbulent history of the universe and may contain fossils of the early universe. We conclude by discussing observational probes of cosmological magnetic fields including the study of extragalactic cosmic rays.

Olinto, A V

1998-01-01

65

Magnetic field line Hamiltonian  

International Nuclear Information System (INIS)

The magnetic field line Hamiltonian and the associated canonical form for the magnetic field are important concepts both for understanding toroidal plasma physics and for practical calculations. A number of important properties of the canonical or Hamiltonian representation are derived and their importance is explained

66

Magnetic field line Hamiltonian  

Energy Technology Data Exchange (ETDEWEB)

The magnetic field line Hamiltonian and the associated canonical form for the magnetic field are important concepts both for understanding toroidal plasma physics and for practical calculations. A number of important properties of the canonical or Hamiltonian representation are derived and their importance is explained.

Boozer, A.H.

1984-03-01

67

Interplanetary Magnetic Field Lines  

Science.gov (United States)

This web page provides information and a graphical exercise for students regarding the interaction between magnetic field lines and a plasma. The activity involves tracing a typical interplanetary magnetic field line, dragged out of a location on the Sun by the radial flow of the solar wind. This illustrates the way magnetic field lines are "frozen to the plasma" and the wrapping of field lines due to the rotation of the sun. This is part of the work "The Exploration of the Earth's Magnetosphere". A Spanish translation is available.

Stern, David

2005-04-27

68

Stability of Magnetic Fluids in Magnetic Fields  

Directory of Open Access Journals (Sweden)

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

I.M. Arefyev

2014-07-01

69

Axial magnetic field lens with permanent magnet  

International Nuclear Information System (INIS)

A compact Permanent Magnet Symmetric (PMS) lens which produces the axial magnetic field is studied. The proposed lens has no iron pole piece except for the return poles on both ends. It can produce the magnetic field on the axis more than the remanent field of the magnet material by the perpendicular field superimposition

70

Cosmological magnetic field survival  

Digital Repository Infrastructure Vision for European Research (DRIVER)

It is widely believed that primordial magnetic fields are dramatically diluted by the expansion of the universe. As a result, cosmological magnetic fields with residual strengths of astrophysical relevance are generally sought by going outside standard cosmology, or by extending conventional electromagnetic theory. Nevertheless, the survival of strong B-fields of primordial origin is possible in spatially open Friedmann universes without changing conventional electromagnetis...

Barrow, John D.; Tsagas, Christos G.

2011-01-01

71

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

72

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

Science.gov (United States)

We have developed multi-dimensional constrained covariant density functional theories (MDC-CDFT) for finite nuclei in which the shape degrees of freedom ??? with even ?, e.g., ?20, ?22, ?30, ?32, ?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 Y32-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 deformations are compared and it is found that the triaxiality plays an important role upon the second fission barriers of actinide nuclei. In the study of Y32-correlations in N = 150 isotones, it is found that, for 248Cf and 260Fm, ?32 > 0.03 and the energy is lowered by the ?32 distortion by more than 300 keV; while for 246Cm and 252No, the pocket with respect to ?32 is quite shallow.

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

2014-03-01

73

Magnetic fields at Neptune  

International Nuclear Information System (INIS)

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

74

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

75

Large ferroquadrupole moment induced in the octupole-ordered Ce0.7La0.3B6 revealed by high-resolution x-ray diffraction  

Science.gov (United States)

We carried out a high-resolution x-ray diffraction experiment on Ce0.7La0.3B6 that exhibits staggered order of 4f octupole moments below TO=1.4 K. Theoretically, ferroquadrupole moments that accompany the antiferro-octupole order and a resultant rhombohedral deformation of the cubic lattice were predicted. In contrast, experimentally, no direct evidence of the rhombohedral lattice has been obtained. We observe the splitting of Bragg peaks below TO and find that the unit cell is a rhombohedron being elongated along the [111] axis. The response of rhombohedral domains to magnetic fields also well agrees with theoretical calculations. A particular outcome of this experiment is that the magnitude of the induced quadrupole moments is precisely evaluated from the obtained shear strain. Using this result, the magnitude of the hidden octupole moments is also discussed.

Inami, T.; Michimura, S.; Hayashi, Y.; Matsumura, T.; Sera, M.; Iga, F.

2014-07-01

76

Multiparticle-octupole coupling and magnetic moments of h[sub 9/2][sup n] isomers in N=126 isotones  

Energy Technology Data Exchange (ETDEWEB)

The influence of particle-vibration coupling on the g-factors of the vertical stroke (h[sub 9/2])[sup n] rightangle isomers in the N=126 isotones is assessed using the multiparticle-octupole-coupling model. According to the model, admixtures of the configuration vertical stroke (h[sub 9/2])[sup n-1]f[sub 7/2] rightangle in the yrast 8[sup +] and 21[sup -]/2 states, nominally associated with the configuration vertical stroke (h[sub 9/2])[sup n] rightangle , increase with n. On its own, the octupole mixing mechanism therefore predicts g-factors for these states that increase with the number of valence protons. This trend is the opposite of that predicted by core-polarization blocking. Combining multiparticle-octupole coupling and first-order core-polarization blocking significantly reduces the discrepancy between the experimental and theoretical g-factors of these states. We conclude that the observed breakdown in additivity for the g-factors of the vertical stroke (h[sub 9/2])[sup n] rightangle isomers in the N=126 isotones arises primarily from first-order core-polarization blocking and the combination of configuration mixing due to multiparticle-octupole coupling and shell-model residual interactions. (orig.)

Stuchbery, A.E. (Dept. of Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National Univ., Canberra (Australia)); Byrne, A.P. (Dept. of Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National Univ., Canberra (Australia)); Dracoulis, G.D. (Dept. of Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National Univ., Canberra (Australia)); Fabricius, B. (Dept. of Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National Univ., Canberra (Australia)); Kibedi, T. (Dept. of Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National Univ., Canberra (Australia))

1993-04-12

77

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

78

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

79

Magnetic field induced superconductivity  

International Nuclear Information System (INIS)

The electrical resistance R and magnetic susceptibility chi of the pressure induced superconductors Sn/sub x/Eu/sub 1.2-x/Mo6S8 have been investigated as a function of magnetic field H up to 17 T and at pressures up to 18 kbar. Anomalous behavior is observed both in R versus H and chi versus H. The resistive behavior at p = 14 kbar at low temperatures is consistent with field enhanced superconductivity resulting from a large exchange field that compensates the applied field

80

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

 
 
 
 
81

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

Energy Technology Data Exchange (ETDEWEB)

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

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

2011-09-06

82

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

Energy Technology Data Exchange (ETDEWEB)

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

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

1998-03-01

83

Experimental tests for stable octupole deformation in actinium-227  

Energy Technology Data Exchange (ETDEWEB)

The question of intrinsic reflection asymmetry or stable-octupole deformation in /sup 227/Ac was studied by the single-proton stripping reactions /sup 226/Ra(/sup 3/He,d)/sup 227/Ac with E/sub 3He/ = 30 MeV and /sup 226/Ra(..cap alpha..,t)/sup 227/Ac with E/sub ..cap alpha../ = 30 MeV and by measuring the magnetic moment of the first excited 3/2/sup +/ 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 /sup 227/Ac. 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 /sup 227/Ac. Furthermore, the results are consistent with the branching ratio determination of the magnetic moment of the first excited state in /sup 227/Ac which is in agreement with the stable-octupole model prediction.

Martz, H.E. Jr.

1986-01-01

84

Magnetic Field Problem: Current  

Science.gov (United States)

A cross section of a circular wire loop carrying an unknown current is shown above. 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 can double-click in the animation to add magnetic field lines, click-drag the center of the loop to reposition it, and click-drag the top or bottom of the loop to change its size.

Christian, Wolfgang; Belloni, Mario

2007-03-03

85

Eruptive solar magnetic fields  

International Nuclear Information System (INIS)

This paper considers the quasi-steady evolution of solar magnetic fields in response to gradual photospheric changes. Special interest is taken in the threshold of a sudden eruption in the solar atmosphere. The formal model of an evolving, force-free field dependent on two Cartesian coordinates has been treated previously, and we extend it to a field which is not force free but in static equilibrium with plasma pressure and gravity. The basic physics is illustrated by the evolution of a loop-shaped electric current sheet enclosing a potential bipolar field with footpoints rooted in the photosphere. A free-boundary problem is posed and solved for the equilibrium configuration of the current sheet in a hydrostatically supported isothermal atmosphere. As the footpoints move appart to spread a constant photospheric magnetic flux over a larger region, the equilibria available extend the field to increasingly great heights. Two basic behaviors are possible, depending on the ratio of the total magnetic flux to an equivalent flux constructed dimensionally from the pressure difference across the current sheet and the density scale height. For a small, total magnetic flux, nonequilibrium can set in with the appearance of a marginally stable equilibriu, as demonstrated previously for the frece-free fields. For a total magnetic flux exceeding a certain critical value, the field lines rise high enough for gravity to play a significant role. The sequence of equilibria in this case . The sequence of equilibria in this case suggests that nonequilibrium can set in with the opening of the field lines by magnetic buoyancy. This eruption can also take place with a prominence filament and may be the origin of the white light coronal transient

86

Octupole instability in the heavy barium region  

Energy Technology Data Exchange (ETDEWEB)

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

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

1987-01-01

87

Magnetic Propeller for Uniform Magnetic Field Levitation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

88

MAGNETICALLY CONTROLLED ACCRETION FLOWS ONTO YOUNG STELLAR OBJECTS  

International Nuclear Information System (INIS)

ow must be close to isothermal. The inclusion of octupole field components produces higher densities at the stellar surface and smaller areas for the hot spots, which occur at higher latitudes; the magnetic truncation radius is smaller (larger) for octupole components that are aligned (anti-aligned) with the stellar dipole. This contribution thus increases our understanding of magnetically controlled accretion for young stellar objects and can be applied to a variety of additional astrophysical problems.

89

Magnetization dynamics using ultrashort magnetic field pulses  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Very short and well shaped magnetic field pulses can be generated using ultra-relativistic electron bunches at Stanford Linear Accelerator. These fields of several Tesla with duration of several picoseconds are used to study the response of magnetic materials to a very short excitation. Precession of a magnetic moment by 90 degrees in a field of 1 Tesla takes about 10 picoseconds, so we explore the range of fast switching of the magnetization by precession.

Tudosa, Ioan

2005-01-01

90

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

91

On magnetic field ``reconstruction''  

Science.gov (United States)

Context: Solanki and colleagues have presented intriguing 3D “reconstructions” of magnetic fields from the vector polarimetry of the He I 1083 nm multiplet. Aims: In this Research Note I re-examine the reconstruction technique used. Methods: Using a simple dipole field, I examine the reconstruction technique as applied to the theoretical fields. I assume that the He line forms in two locations, (1) along the magnetic loops and (2) in a horizontal plane. Results: The planar interpretation can account for all aspects of the data, but the loop interpretation has geometrical and physical problems. Conclusions: The data by themselves are not sufficient to determine which picture is more applicable. Nevertheless I argue that the planar interpretation makes more physical sense and that the early reconstructions lead to spurious results. I suggest additional tests that might help constrain the problem further.

Judge, P. G.

2009-01-01

92

Nuclear Magnetic Resonance and Magnetic Field Measurements  

Science.gov (United States)

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

2012-01-04

93

Magnetic fields in diffuse media  

CERN Document Server

This volume presents the current knowledge of magnetic fields in diffuse astrophysical media. Starting with an overview of 21st century instrumentation to observe astrophysical magnetic fields, the chapters cover observational techniques, origin of magnetic fields, magnetic turbulence, basic processes in magnetized fluids, the role of magnetic fields for cosmic rays, in the interstellar medium and for star formation. Written by a group of leading experts the book represents an excellent overview of the field. Nonspecialists will find sufficient background to enter the field and be able to appreciate the state of the art.

Pino, Elisabete; Melioli, Claudio

2015-01-01

94

Magnetic fields of OB stars  

Science.gov (United States)

We studied the statistical properties of the magnetic fields of OB stars based on the recent measurements. As the statistically significant characteristic of the magnetic field we use the rms magnetic field of the star ${\\cal B}$ . The distribution functions f( ${\\cal B}$ ) of magnetic fields of OB stars are evaluated. The function f( ${\\cal B}$ ) has a power-law dependence on the ${\\cal B}$ with an index of about 2-3 and a fast drop below ${\\cal B}$ = 100 - 300 G. We proposed that the compact regions with strong local magnetic fields can contribute to the global magnetic field of O stars.

Kholtygin, A. F.; Hubrig, S.; Drake, N. A.; Sudnik, N.; Dushin, V.

2014-08-01

95

Magnetic helicity and cosmological magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The magnetic helicity has paramount significance in nonlinear saturation of galactic dynamo. We argue that the magnetic helicity conservation is violated at the lepton stage in the evolution of early Universe. As a result, a cosmological magnetic field which can be a seed for the galactic dynamo obtains from the beginning a substantial magnetic helicity which has to be taken into account in the magnetic helicity balance at the later stage of galactic dynamo.

Semikoz, V. B.; Sokoloff, D. D.

2004-01-01

96

Magnetic field reconnection  

International Nuclear Information System (INIS)

The fundamental principles of particle acceleration by magnetic reconnection in cosmic plasmas are reviewed. The history of reconnection models is traced, and consideration is given to the Kelvin-Helmholtz theorem, the frozen-field theorem, the application of the Kelvin-Helmholtz theorem to a collisionless plasma, solutions to specific reconnection problems, and configurational instability. Diagrams and graphs are provided, and the objections raised by critics of the reconnection theory and/or its astrophysical applications are discussed. 42 references

97

Coupling of the giant dipole resonance to low lying octupole modes - generator coordinate method study  

Science.gov (United States)

The effect on the properties of low lying octupole modes of the coupling with the giant dipole resonance is studied within the Generator Coordinate Method. Results are presented for 152Sm which is deformed in its ground state and for the superdeformed state of 190Hg. A basis is first generated by Hartree-Fock+BCS calculations with constraints on the octupole and dipole moments. The same Skyrme SkM ? effective interaction used in the mean field is then diagonalised by the GCM. For the octupole K = 0 mode, the effect of the coupling is marginal and the dipole properties of low lying states are satisfactorily described by pure octupole calculations. For the K = 1 mode, the dipole-octupole coupling slightly reduces the E1 transition strength.

Heenen, P.-H.; Skalski, J.

1996-02-01

98

Reflection asymmetric shell model for octupole rotation  

International Nuclear Information System (INIS)

The reflection asymmetric shell model approach has been introduced for the description of octupole bands. The Q·Q forces of quadrupole, octupole and hexadecapole as well as the monopole and quadrupole pairings are included in the hamiltonian. The shell model space is spanned by a selected set of the projected axial and octupole Nilsson plus BSC basis. The calculated results for the octupole bands in the A=220 region are in a good agreement with the experimental data. The experimental SD bands 1 and 3 in 194Hg are well reproduced by the present calculation and interpreted as the parity partner octupole SD bands with K? = 0+ and K? = 0- respectively. (author)

99

Magnetic Field Topology in Jets  

Science.gov (United States)

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

Gardiner, T. A.; Frank, A.

2000-01-01

100

THE GALACTIC MAGNETIC FIELD  

Energy Technology Data Exchange (ETDEWEB)

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

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

2012-12-10

 
 
 
 
101

The Galactic Magnetic Field  

CERN Document Server

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

Jansson, Ronnie

2012-01-01

102

THE GALACTIC MAGNETIC FIELD  

International Nuclear Information System (INIS)

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

103

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

104

Measuring nuclear magnetization in strong magnetic fields  

International Nuclear Information System (INIS)

Al nuclear magnetization has been measured in magnetic fields up to 100 kOe, by use of a capacitive Faraday magnetometer installed in a dilution refrigerator. The sample employed was an Al0.98Si0.02 alloy prepared from high purity (6N) elements. The Si doping was essential in suppressing the de Haas-van Alphen oscillations of conduction electrons. Fine Curie's law was observed at temperatures below 3 K down to ?60 mK, in several magnetic fields in the range 30-100 kOe. The measurement opens a new route towards primary thermometry at low temperature and high magnetic field region

105

NMR at low magnetic fields  

Science.gov (United States)

NMR provides outstanding information in chemistry and in medicine. But the equipment is expensive as high-field magnets are employed. Low-field NMR works with inexpensive permanent magnets. Until recently these did not provide fields sufficiently homogeneous for spectroscopy and were mostly used for relaxation measurements. Relaxation can also be measured outside the magnet, and small mobile NMR devices have been developed for non-destructive testing of large objects. Today small stray-field magnets and small magnets with homogeneous fields are available for relaxation analysis, imaging, and spectroscopy. Their availability is believed to be essential for shifting NMR analysis from a specialist's tool to a convenience tool.

Blümich, Bernhard; Casanova, Federico; Appelt, Stephan

2009-08-01

106

The Heliospheric Magnetic Field  

Directory of Open Access Journals (Sweden)

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

Mathew J. Owens

2013-11-01

107

Magnetic Fields: Visible and Permanent.  

Science.gov (United States)

Children will be able to see the concept of a magnetic field translated into a visible reality using the simple method outlined. Standard shelf paper, magnets, iron filings, and paint in a spray can are used to prepare a permanent and well-detailed picture of the magnetic field. (Author/JN)

Winkeljohn, Dorothy R.; Earl, Robert D.

1983-01-01

108

Low frequency turbulence, particle and heat transport in the Wisconsin levitated octupole  

International Nuclear Information System (INIS)

Low frequency turbulence in the drift frequency range and its relation to the observed particle transport in the Wisconsin Levitated Octupole has been studied with a microwave scattering apparatus. The effect of shear on the transport was studied by the addition of a small toroidal field. By matching experimentally measured density profiles to those given by numerical solutions of the transport equations, diffusion coefficients were obtained. At high magnetic field strengths the gun injected plasmas initially decayed in such a way as to indicate a diffusive mechanism which scaled like D/sub perpendicular to/ proportional to n-05 dominated the transport, damping out on a time scale of milliseconds. The residual diffusion scaled like classical, D/sub perpendicular to/ proportional to/n2, B, but was enhanced above classical by an order of magnitude. At lower values of magnetic field and of all times following injection, the diffusion scaled like classical, but again was an order of magnitude above classical

109

Collective T- and P- Odd Electromagnetic Moments in Nuclei with Octupole Deformations  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Parity and time invariance violating forces produce collective P- and T- odd moments in nuclei with static octupole deformation. Collective Schiff moment, electric octupole and dipole and also magnetic quadrupole appear due to the mixing of rotational levels of opposite parity and can exceed single-particle moments by more than a factor of 100. This enhancement is due to two factors, the collective nature of the intrinsic moments and the small energy separation between membe...

Auerbach, N.; Flambaum, V. V.; Spevak, V.

1996-01-01

110

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

111

Understanding the Chromospheric Magnetic Field  

Science.gov (United States)

The chromospheric magnetic field is an important and essential component for understanding solar atmospheric fields. Due to the problems of polarization radiation transfer in the chromosphere and the low detective sensitivity of chromospheric spectrum lines, observations of chromospheric magnetic fields are very difficult, so studies of chromospheric fields are infrequent. However, the understanding of chromospheric fields is evolving. In this report, we summarize our current empirical knowledge and basic physical understanding of chromospheric fields. We concentrate on the comparison of magnetic fields in the photosphere and chromosphere, and then display their difference.

Jin, C. L.; Harvey, J. W.; Pietarila, A.

2014-10-01

112

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.

113

Evolution of twisted magnetic fields  

International Nuclear Information System (INIS)

The magnetic field of the solar corona evolves quasi-statically in response to slowly changing photospheric boundary conditions. The magnetic topology is preserved by the low resistivity of the solar atmosphere. It is shown that a magnetic flux coordinate system simplifies the problem of calculating field evolution with invariant topology. As an example, the equilibrium of a thin magnetic flux tube with small twist per unit length was calculated. 22 references

114

Reconnection of Magnetic Fields  

Science.gov (United States)

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

Birn, J.; Priest, E. R.

2007-01-01

115

Magnetic fields in nearby galaxies  

CERN Document Server

Observations of synchrotron radiation and the Faraday rotation of its polarized component allow us to investigate the magnetic properties of the diffuse interstellar medium in nearby galaxies, on scales down to roughly one hundred parsecs. All disc galaxies seem to have a mean, or regular, magnetic field component that is ordered on length scales comparable to the size of the galaxy as well as a random magnetic field of comparable or greater strength. I present an overview of what is currently known observationally about galactic magnetic fields, focusing on the common features among galaxies that have been studied rather than the distinctive or unusual properties of individual galaxies. Of particular interest are the azimuthal patterns formed by regular magnetic fields and their pitch angles as these quantities can be directly related to the predictions of the mean field dynamo theory, the most promising theoretical explanation for the apparent ubiquitous presence of regular magnetic fields in disc galaxies.

Fletcher, Andrew

2011-01-01

116

Octupole bands of Gd isotopes  

International Nuclear Information System (INIS)

Excited states in 154,156,158,160Gd have been populated through the multiple coulomb excitation process by 32S, 48Ti, 58Ni ions. The ground band, ?-band and octupole K?=0- band were extended to I?=16+, (12+), and (11-) state respectively in 160Gd. The octupole K?=1- band was extended to I?=9- state in 158Gd. Excitation cross sections of individual levels relative to that of the I?=4+ state in the ground band in each nucleus were compared with the simulation by the computer code GOSIA within the framework of the pure rotational model. From these comparisons the matrix elements for both intra-band and inter-band transitions were deduced. (orig.)

117

Cryogenically cooled octupole ion trap for spectroscopy of biomolecular ions.  

Science.gov (United States)

We present here the design of a linear octupole ion trap, suitable for collisional cryogenic cooling and spectroscopy of large ions. The performance of this trap has been assessed using ultraviolet (UV) photofragmentation spectroscopy of protonated dipeptides. At the trap temperature of 6.1 K, the vibrational temperature of the ions reaches 9.1 K, although their estimated translational temperature is ~150 K. This observation suggests that, despite the significant translational heating by radio-frequency electrical field, vibrational cooling of heavy ions in the octupole is at least as efficient as in the 22-pole ion traps previously used in our laboratory. In contrast to the 22-pole traps, excellent radial confinement of ions in the octupole makes it convenient for laser spectroscopy and boosts the dissociation yield of the stored ions to 30%. Overlap of the entire ion cloud by the laser beam in the octupole also allows for efficient UV depletion spectroscopy of ion-He clusters. The measured electronic spectra of the dipeptides and the clusters differ drastically, complicating a use of UV tagging spectroscopy for structural determination of large species. PMID:24689562

Boyarkin, Oleg V; Kopysov, Vladimir

2014-03-01

118

Cryogenically cooled octupole ion trap for spectroscopy of biomolecular ions  

Science.gov (United States)

We present here the design of a linear octupole ion trap, suitable for collisional cryogenic cooling and spectroscopy of large ions. The performance of this trap has been assessed using ultraviolet (UV) photofragmentation spectroscopy of protonated dipeptides. At the trap temperature of 6.1 K, the vibrational temperature of the ions reaches 9.1 K, although their estimated translational temperature is ˜150 K. This observation suggests that, despite the significant translational heating by radio-frequency electrical field, vibrational cooling of heavy ions in the octupole is at least as efficient as in the 22-pole ion traps previously used in our laboratory. In contrast to the 22-pole traps, excellent radial confinement of ions in the octupole makes it convenient for laser spectroscopy and boosts the dissociation yield of the stored ions to 30%. Overlap of the entire ion cloud by the laser beam in the octupole also allows for efficient UV depletion spectroscopy of ion-He clusters. The measured electronic spectra of the dipeptides and the clusters differ drastically, complicating a use of UV tagging spectroscopy for structural determination of large species.

Boyarkin, Oleg V.; Kopysov, Vladimir

2014-03-01

119

Magnetic response to applied electrostatic field in external magnetic field  

CERN Document Server

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

Adorno, T C; Shabad, A E

2013-01-01

120

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.)

 
 
 
 
121

Theory of fossil magnetic field  

CERN Document Server

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

Dudorov, Alexander E

2014-01-01

122

Cosmic Magnetic Fields - An Overview  

Science.gov (United States)

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

Wielebinski, Richard; Beck, Rainer

123

Charge in Magnetic Field Model  

Science.gov (United States)

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

Hwang, Fu-Kwun

2009-05-19

124

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

125

Multipactor discharges in magnetic fields  

International Nuclear Information System (INIS)

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

126

Interplanetary electric and magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

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

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

1982-08-01

127

Design of multi-element corrector magnet for NewSUBARU  

International Nuclear Information System (INIS)

An octupole-base corrector magnet of multi-elements was designed. The new corrector magnets will be installed in the electron storage ring NewSUBARU in place of vertical steering (dipole) magnets in 2010. The new magnet will have coil windings to produce skew quadrupole, skew sextupole, normal octupole, and the skew dipole field. The skew dipole element will work as a vertical steering. The skew quadrupole and the skew sextupole elements are for the resonance correction. The normal octupole element will be use to control the higher order dispersion function and the higher order momentum compaction factor of the ring. In designing the magnet, a consideration to a field interference with the neighboring magnet was an important issue, because the yoke length, space between the yokes and the bore diameter are comparable. The field interference was calculated using OPERA-3D. (author)

128

The non-dipolar magnetic fields of accreting T Tauri stars  

CERN Document Server

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

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

2008-01-01

129

New circumstellar magnetic field diagnostics  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Nordsieck, K. H.

2001-01-01

130

Resonant magnetic fields from inflation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We propose a novel scenario to generate primordial magnetic fields during inflation induced by an oscillating coupling of the electromagnetic field to the inflaton. This resonant mechanism has two key advantages over previous proposals. First of all, it generates a narrow band of magnetic fields at any required wavelength, thereby allaying the usual problem of a strongly blue spectrum and its associated backreaction. Secondly, it avoids the need for a strong coupling as the ...

Byrnes, Christian T.; Hollenstein, Lukas; Jain, Rajeev Kumar; Urban, Federico R.

2011-01-01

131

The NEAR Magnetic Field Instrument.  

Science.gov (United States)

The primary objective of the Magnetic Field Instrument on the Near Earth Asteroid Rendezvous (NEAR) spacecraft is to search for and characterize the magnetic field of the asteroid 433 Eros to better understand the origin and evolution of this planetary body. The instrument consists of a three-axis fluxgate magnetometer with a sensor mounted on the high-gain antenna feed structure of the NEAR spacecraft. It is currently operating in space and is providing measurements of the interplanetary magnetic field with a resolution of better than 1 nT. The Magnetic Field Instrument is capable of detecting a surface field at Eros of 10 nT at the 35-km altitude that will be the eventual orbit of NEAR.

Lohr, D. A.; Zanetti, L. J.; Anderson, B. J.; Potemra, T. A.; Acuña, M. H.

1998-06-01

132

Preflare magnetic and velocity fields  

Science.gov (United States)

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

Hagyard, M. J.; Gaizauskas, V.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M.-J.; Porter, J. G.; Schmeider, B.

1986-01-01

133

Resonant magnetic fields from inflation  

International Nuclear Information System (INIS)

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

134

Magnetoconvection in sheared magnetic fields  

International Nuclear Information System (INIS)

The development of magnetoconvection in a sheared magnetic field is investigated. The equilibrium magnetic field B0 is horizontal and its orientation varies linearly along the vertical axis. Preliminary consideration of the transition from the inertial to the viscous regime of the gravitational resistive interchange instability, reveals that the latter is characterized by the existence of viscoresistive boundary layers of vertical width which scales as Q-1/6, where Q is the Chandrasekhar number. The situation is analogous to the one encountered in magnetically confined laboratory plasmas, where convective flows are constrained by the magnetic shear to develop in boundary layers located around resonant magnetic surfaces in order to fulfill the ''interchange condition''k·B0=0, where k is the wave vector of the magnetic perturbation. It follows that when the effect of thermal diffusion is taken into account in the process, convection can only occur above a certain critical value of the Rayleigh number which scales as Q2/3 for large Q. At the onset, the convection pattern is a superposition of identically thin convective rolls everywhere aligned with the local magnetic field lines and which therefore adopt the magnetic field geometry, a situation also reminiscent of the penumbra of sunspots. Using this degeneracy, equations describing the weakly nonlinear state are obtained and discussed. A reduced magnetohydrodynamic description of magnetoconvection is introduced. Since it is valid for arbitrary magnetic field configurations, it allows a simple extension to the case where there exists an inclination between the direction of gravity and the plane spanned by the equilibrium magnetic field. These reduced magnetohydrodynamic equations are proposed as a powerful tool for further investigations of magnetoconvection in more complex field line geometries.

135

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

136

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

137

Magnetic fields in neutron stars  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

Vigano?, Daniele

2013-01-01

138

Magnetic Fields from Phase Transitions  

CERN Document Server

The generation of primordial magnetic fields from cosmological phase transitions is discussed, paying particular attention to the electroweak transition and to the various definitions of the `average' field that have been put forward. It is emphasised that only the volume average has dynamical significance as a seed for galactic dynamos. On rather general grounds of causality and energy conservation, it is shown that, in the absence of MHD effects that transfer power in the magnetic field from small to large scales, processes occurring at the electroweak transition cannot generate fields stronger than $10^{-20}$ Gauss on a scale of 0.5 Mpc. However, it is implausible that this upper bound could ever be reached, as it would require all the energy in the Universe to be turned into a magnetic field coherent at the horizon scale. Non-linear MHD effects seem therefore to be necessary if the electroweak transition is to create a primordial seed field.

Hindmarsh, M B; Hindmarsh, Mark; Everett, Allen

1998-01-01

139

N-flationary magnetic fields  

CERN Document Server

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

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

2007-01-01

140

Subsurface magnetic fields from helioseismology  

CERN Document Server

Using even-order frequency splitting coefficients of global p-modes it is possible to infer the magnetic field in the solar interior as a function of radial distance and latitude. Results obtained using GONG and MDI data are discussed. While there is some signal of a possible magnetic field in the convection zone, there is little evidence for any temporal variation of the magnetic field in the solar interior. Limits on possible magnetic field in the solar core are also discussed. It is generally believed that the solar dynamo is located in the tachocline region. Seismic studies do not show any significant temporal variation in the tachocline region, though a significant latitudinal variation in the properties of the tachocline are found. There is some evidence to suggest that the latitudinal variation is not continuous and the tachocline may consist of two parts.

Antia, H M

2002-01-01

 
 
 
 
141

Magnetic field generation in plasma  

Science.gov (United States)

An equation is obtained which describes the generation of a quasi-stationary magnetic field in a weakly ionized plasma or a plasma consisting of multiply charged ions in a high-frequency electromagnetic wave. A consistent kinematic description of electron heating during bremsstrahlung absorption has made it possible to discover the effect of a substantial increase in the magnetic field rise rate dependent on the radiation intensity.

Ovchinnikov, K. N.; Silin, V. P.; Uriupin, S. A.

1991-09-01

142

Theorem on magnet fringe field  

International Nuclear Information System (INIS)

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

143

Magnetic resonance in an elliptic magnetic field  

Energy Technology Data Exchange (ETDEWEB)

The behaviour of a particle with a spin 12 and a dipole magnetic moment in a time-varying magnetic field in the form (h{sub 0}cn({omega}t,k),h{sub 0}sn({omega}t,k),H{sub 0}dn({omega}t,k)), where {omega} is the angular frequency of the radiation field, t is the time, h{sub 0} and H{sub 0} are the field amplitudes, cn, sn, dn are Jacobi elliptic functions and k is the modulus of the elliptic functions, has been considered. The variation parameter k from 0 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 the 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. [National Science Center, ' Kharkov Institute of Physics and Technology' , Institute for Theoretical Physics, 1 Akademicheskaya Str., 61108 Kharkov (Ukraine)]. E-mail: yevgeny@kipt.kharkov.ua

2005-04-15

144

Magnetic field induced dynamical chaos  

International Nuclear Information System (INIS)

In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the x–y plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples

145

Magnetic field induced dynamical chaos  

Energy Technology Data Exchange (ETDEWEB)

In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the x–y plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples.

Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra, E-mail: bidhanchandra.bag@visva-bharati.ac.in [Department of Chemistry, Visva-Bharati, Santiniketan 731 235 (India)

2013-12-15

146

Effective magnetic anisotropy vector field  

International Nuclear Information System (INIS)

An effective anisotropy vector field that can be treated as an effective external field has been formulated for uniaxial anisotropies with n-fold symmetry within the plane containing the main axis. A simple method for obtaining the effective field for the two-fold symmetry uniaxial anisotropy and the calculated result according to the method are presented. Then the extension to n-fold symmetry anisotropies is given and the calculated results for four- and six-fold symmetry cases are demonstrated. The tips of those vector fields are found to trace hypocycloids moving oppositely with the rotation of magnetization. The newly introduced effective anisotropy vector field may make a new tool in various analysis of magnetization processes and help understand the effect of anisotropy on magnetization visually

147

Magnetic field properties of the ISABELLE Project superconducting dipole magnets  

International Nuclear Information System (INIS)

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

148

Magnetic fields in O stars  

Science.gov (United States)

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

Nazé, Y.

2014-11-01

149

Magnetic Field System of PERC  

International Nuclear Information System (INIS)

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

150

Octupole deformation in odd-odd nuclei  

International Nuclear Information System (INIS)

Experimental evidence for octupole deformation in odd-odd nuclei is examined in both the rare earth and actinide regions. Extensive existing experimental data on 154Eu and 152Eu suggest the existence of octupole deformation, while the evidence is less clear for 156Eu. 224Ac and 220Fr have been studied experimentally following the alpha decay of accelerator produced and isotope separated 228PaF+4 and 220AcF+2 ions, respectively. Clear evidence of octupole deformation is found in both cases. Unusually small parity doublet splitting energies are found for the K = O± and K = 3± bands of 224Ac. The experimental Newby shifts of the K = 0± bands in 224Ac have opposite sign but approach the same absolute magnitude as theoretically expected for an octupole deformed system

151

Critical Magnetic Field Ratio of Anisotropic Magnetic Superconductors  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The upper critical field, the lower critical field and the critical magnetic field ratio of anisotropic magnetic superconductors are calculated by Ginzburg-Landau theory analytically. The effect of the Ginzburg-Landau parameter(\\kappa_0), magnetic susceptibility(\\chi) and magnetic-to- anisotropic parameter ratio(\\theta) on the critical field ratio are considered. We find that the value of critical magnetic field ratio with \\chi < 0, higher \\kappa_0,and higher \\theta case are...

Changjan, A.; Udomsamuthirun, P.

2010-01-01

152

Indoor localization using magnetic fields  

Science.gov (United States)

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

Pathapati Subbu, Kalyan Sasidhar

153

Crystal fields in metallic magnetism  

International Nuclear Information System (INIS)

The magnetic structure and excitations of praseodymium are reviewed. Two phenomena which cannot be understood within the standard model of rare earth magnetism are discussed. These are the quasielastic peak which is present in both the paramagnetic and antiferromagnetic phases, and the excitations which accompany the crystal field excitations near the Brillouin zone centre. We also review the properties of the localised moment compound UPd3, and discuss the nature of the quadrupolar phases observed in this system. (au)

154

Protogalactic evolution and magnetic fields  

CERN Document Server

We show that the relatively strong magnetic fields (\\ge 1 \\muG) in high redshift objects can be explained by the combined action of an evolving protogalactic fluctuation and electrodynamic processes providing the magnetic seed fields. Three different seed field mechanisms are reviewed and incorporated into a spherical "top-hat" model and tidal torque theory for the fate of a forming galaxy in an expanding universe. Very weak fields 10^{-19} \\sim 10^{-23}G created in an expanding over-dense region are strongly enhanced due to the dissipative disk formation by a factor \\sim 10^4, and subsequently amplified by strong non-axisymmetric flow by a factor \\sim 10^{6-10}, depending on the cosmological parameters and the epoch of galaxy formation. The resulting field strength at z \\sim 0.395 can be of the order of a few \\muG and be close to this value at z \\sim 2.

Lesch, H; Lesch, Harald; Chiba, Masashi

1994-01-01

155

Global systematics of octupole excitations in even-even nuclei  

CERN Document Server

We present a computational methodology for a theory of the lowest octupole excitations applicable to all even-even nuclei beyond the lightest. The theory is the well-known generator-coordinate extension (GCM) of the Hartree-Fock-Bogoliubov self-consistent mean field theory (HFB). We use the discrete-basis Hill-Wheel method (HW) to compute the wave functions with an interaction from the Gogny family of Hamiltonians. Comparing to the compiled experimental data on octupole excitations, we find that the performance of the theory depends on the deformation characteristics of the nucleus. For nondeformed nuclei, the theory reproduces the energies to about 20 % apart from an overall scale factor of about 1.6. The performance is somewhat poorer for (quadrupole) deformed nuclei, and for both together the dispersion of the scaled energies about the experimental values is about 25 %. This compares favorably with the performance of similar theories of the quadrupole excitations. Nuclei having static octupole deformations...

Robledo, L M

2011-01-01

156

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

157

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)

158

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.

159

Magnetic Field from Loops Model  

Science.gov (United States)

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

Christian, Wolfgang; Hwang, Fu-Kwun

2008-11-17

160

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

 
 
 
 
161

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

162

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

CERN Document Server

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

Petrie, G J D

2013-01-01

163

Chiral transition with magnetic fields  

CERN Document Server

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

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

2014-01-01

164

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.)

165

How to Draw Magnetic Fields - I  

Science.gov (United States)

This is an activity about depicting magnetic fields. Learners will observe two provided drawings of magnetic field line patterns for bar magnets in simple orientations of like and unlike polarities and carefully draw the field lines for both orientations. This is the third activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.

166

Minus-I quadrupole system for containing aberration-correction octupoles  

International Nuclear Information System (INIS)

Octupoles may be used to correct the third order spherical aberration of quadrupole transport systems. Crosstalk in the coupling of an octupole placed at a given point causes it to add a term with the wrong sign in the y-channel if it has the right sign in the x-channel, thus severely reducing efficiency. It is often convenient to utilize a special correcting section insertion which is seen as a +I transfer matrix by the first order focusing. Within point-to-point thin lens optics we give two-parameter systems with 16 magnets having locations with large S/sub x/ where S/sub y/ = 0 and vice versa for octupole placement

167

Magnetic fields in the cosmos  

International Nuclear Information System (INIS)

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

168

Neutrinos in Strong Magnetic Fields  

CERN Document Server

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

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

1997-01-01

169

Skewed magnetic field lines reconnection  

International Nuclear Information System (INIS)

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

170

Octupole correlations in $^{229}Ra$  

CERN Document Server

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

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

1999-01-01

171

Octupole correlations in 229Ra  

International Nuclear Information System (INIS)

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

172

Magnetically Controlled Accretion Flows onto Young Stellar Objects  

CERN Document Server

(abridged) Accretion from disks onto young stars is thought to follow magnetic field lines from the inner disk edge to the stellar surface. The accretion flow thus depends on the geometry of the magnetic field. This paper extends previous work by constructing a collection of orthogonal coordinate systems, including the corresponding differential operators, where one coordinate traces the magnetic field lines. This formalism allows for an (essentially) analytic description of the geometry and the conditions required for the flow to pass through sonic points. Using this approach, we revisit the problem of magnetically controlled accretion flow in a dipole geometry, and then generalize the treatment to consider magnetic fields with multiple components, including dipole, octupole, and split monopole contributions. This approach can be generalized further to consider more complex magnetic field configurations. Observations indicate that accreting young stars have substantial dipole and octupole components, and tha...

Adams, Fred C

2011-01-01

173

Magnetic field tomography, helical magnetic fields and Faraday depolarization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

174

Magnetic fields and coronal heating  

International Nuclear Information System (INIS)

General considerations concerning the scaling properties of magnetic-field--related colonal heating mechanisms are used to build a two-parameter model for the heating of closed coronal regions. The model perdicts the way in which coronal temperature and electron density are related to photospheric magnetic field strength and the size of the region, using the additional constraint provided by the scaling law of rosner, tucker, and Viaiana. The model successfully duplicates the observed scaling of total thermal energy content with total longitudinal flux; it also predict a relation between the coronal energy density (or pressure) and the longitudinal field strength modified by the region scale size. The observational data yield a similar relation, pproportional/sup 1.6/. A parameter of the theory, which is evaluated by fitting to the data, is the product ?upsilon/sub phi/, where ? is the ratio of azimuthal to longitudinal magnetic field and upsilon/sub phi/ is the effective twisting velocity of the loop footpoints, which supplies the energy for coronal heating

175

Hypernuclear matter in strong magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

176

Hypernuclear matter in strong magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

2010-01-01

177

Generation of magnetic fields for accelerators with permanent magnets  

International Nuclear Information System (INIS)

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

178

Quark stars in strong magnetic fields  

Science.gov (United States)

Within the confined isospin- and density-dependent mass model, we study the properties of strange quark matter (SQM) and quark stars (QSs) in strong magnetic fields. The equation of state of SQM under a constant magnetic field is obtained self-consistently and the pressure perpendicular to the magnetic field is shown to be larger than that parallel to the magnetic field, implying that the properties of magnetized QSs generally depend on both the strength and the orientation of the magnetic fields distributed inside the stars. Using a density-dependent magnetic field profile which is introduced to mimic the magnetic field strength distribution in a star, we study the properties of static spherical QSs by assuming two extreme cases for the magnetic field orientation in the stars, i.e., the radial orientation in which the local magnetic fields are along the radial direction, and the transverse orientation in which the local magnetic fields are randomly oriented but perpendicular to the radial direction. Our results indicate that including the magnetic fields with radial (transverse) orientation can significantly decrease (increase) the maximum mass of QSs, demonstrating the importance of the magnetic field orientation inside the magnetized compact stars.

Chu, Peng-Cheng; Chen, Lie-Wen; Wang, Xin

2014-09-01

179

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

180

Simulation Outside Magnetic Field of the Sun  

Directory of Open Access Journals (Sweden)

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

Zhiliang Yang

2011-06-01

 
 
 
 
181

Magnetic field reversals and galactic dynamos  

CERN Document Server

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

Moss, David

2012-01-01

182

The ACE Magnetic Fields Experiment  

Science.gov (United States)

The magnetic field experiment on ACE provides continuous measurements of the local magnetic field in the interplanetary medium. These measurements are essential in the interpretation of simultaneous ACE observations of energetic and thermal particles distributions. The experiment consists of a pair of twin, boom- mounted, triaxial fluxgate sensors which are located 165 inches (=4.19 m) from the center of the spacecraft on opposing solar panels. The electronics and digital processing unit (DPU) is mounted on the top deck of the spacecraft. The two triaxial sensors provide a balanced, fully redundant vector instrument and permit some enhanced assessment of the spacecraft's magnetic field. The instrument provides data for Browse and high-level products with between 3 and 6 vector s-1 resolution for continuous coverage of the interplanetary magnetic field. Two high-resolution snapshot buffers each hold 297 s of 24 vector s-1 data while on- board Fast Fourier Transforms extend the continuous data to 12 Hz resolution. Real-time observations with 1-s resolution are provided continuously to the Space Environmental Center (SEC) of the National Oceanographic and Atmospheric Association (NOAA) for near- instantaneous, world-wide dissemination in service to space weather studies. As has been our team's tradition, high instrument reliability is obtained by the use of fully redundant systems and extremely conservative designs. We plan studies of the interplanetary medium in support of the fundamental goals of the ACE mission and cooperative studies with other ACE investigators using the combined ACE dataset as well as other ISTP spacecraft involved in the general program of Sun-Earth Connections.

Smith, C. W.; L'Heureux, J.; Ness, N. F.; Acuña, M. H.; Burlaga, L. F.; Scheifele, J.

1998-07-01

183

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

184

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

185

Field quality aspects of CBA superconducting magnets  

International Nuclear Information System (INIS)

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

186

Magnetic field effect for cellulose nanofiber alignment  

Science.gov (United States)

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

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

2008-11-01

187

Topological constraints in magnetic field relaxation  

Science.gov (United States)

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

Candelaresi, S.

2014-10-01

188

Magnetization of cylindrical hard superconductors in longitudinally applied magnetic fields  

International Nuclear Information System (INIS)

On the basis of the critical state model, and using as its equation Jsub(c)Hsub(i)?=?, the magnetization of cylindrical hard superconductors is calculated. The external magnetic field is applied parallel to the axis of symmetry of the sample. It is shown that there are three types of magnetization cycle curves that depend on the maximum applied magnetic field. It is demonstrated how to determine the parameters ? and ? for any experimental magnetization curve. (author)

189

Octupole deformation in sup 223 Ac  

Energy Technology Data Exchange (ETDEWEB)

The level structure of {sup 223}Ac has been obtained from a study of the alpha-decay of mass separated {sup 227}Pa. Two levels connected by a fast E1 transition and with spin and parity 5/2{sup +} and 5/2{sup -} were found: They form a parity doublet suggestive of octupole deformation in this nuclei. The Coriolis matrix element obtained for the mixing between the low-lying states is found to be attenuated, in agreement with theoretical expectations for stable octupole deformation. (orig.).

Ahmad, I.; Holzmann, R.; Janssens, R.V.F. (Argonne National Lab., IL (USA)); Dendooven, P.; Huyse, M.; Reusen, G.; Wauters, J.; Duppen, P. van (Leuven Univ. (Belgium). LISOL)

1989-12-11

190

Magnetic Field Induced Chain Alignment of Ferroparticles in Magnetic Fluid  

Directory of Open Access Journals (Sweden)

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

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

2013-07-01

191

Microscopic analysis of the octupole phase transition in Th isotopes  

CERN Document Server

A shape phase transition between stable octupole deformation and octupole vibrations in Th nuclei is analyzed in a microscopic framework based on nuclear density functional theory. The relativistic functional DD-PC1 is used to calculate axially-symmetric quadrupole-octupole constrained energy surfaces. Observables related to order parameters are computed using an interacting-boson Hamiltonian, with parameters determined by mapping the microscopic energy surfaces to the expectation value of the Hamiltonian in the boson condensate. The systematics of constrained energy surfaces and low-energy excitation spectra point to the occurrence of a phase transition between octupole-deformed shapes and shapes characterized by octupole-soft potentials.

Nomura, K; Lu, B -N

2013-01-01

192

Biotropic parameters of magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

The use of magnetic fields (MF) in biology and medicine to control biological systems has led to appearance of the term, biotropic parameters of MF. They include the physical characteristics of MF, which determine the primary biologically significant physicochemical mechanisms of field action causing formation of corresponding reactions on the level of the integral organism. These parameters include MF intensity, gradient, vector, pulse frequency and shape, and duration of exposure. Factors that elicit responses by the biological system include such parameter of MF interaction with the integral organism as localization of exposure and volume of tissues interacting with the field, as well as the initial state of the organism. In essence, the findings of experimental studies of biotropic parameters of MF make it possible to control physiological processes and will aid in optimizing methods of MF therapy.

Shishlo, M.A.

193

Magnetic Helicity and Large Scale Magnetic Fields: A Primer  

CERN Document Server

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

Blackman, Eric G

2014-01-01

194

Magnetic fields and halos in spiral galaxies  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

195

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

196

How to Draw Magnetic Fields - II  

Science.gov (United States)

This is an activity about depicting magnetic polarity. Learners will observe several provided drawings of magnetic field line patterns for bar magnets in simple orientations of like and unlike polarities and carefully draw the field lines and depict the polarities for several orientations, including an arrangement of six magnetic poles. This is the fourth activity in the Magnetic Math booklet; this booklet can be found on the Space Math@NASA website.

197

Quark Antiscreening at Strong Magnetic Field and Inverse Magnetic Catalysis  

CERN Document Server

The dependence of the QCD coupling constant with a strong magnetic field and the implications for the critical temperature of the chiral phase transition are investigated. It is found that the coupling constant becomes anisotropic in a strong magnetic field, and that the quarks, confined by the field to the LLL, produce an antiscreening effect. These results lead to inverse magnetic catalysis, providing a natural explanation for the behavior of the critical temperature in the strong field region.

Ferrer, E J; Wen, X J

2014-01-01

198

Magnetic field measuring system for remapping the ORIC magnetic field  

International Nuclear Information System (INIS)

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

199

Low frequency turbulence, particle and heat transport in the Wisconsin levitated octupole  

Energy Technology Data Exchange (ETDEWEB)

Low frequency turbulence in the drift frequency range and its relation to the observed particle transport in the Wisconsin Levitated Octupole has been studied with a microwave scattering apparatus. The effect of shear on the transport was studied by the addition of a small toroidal field. By matching experimentally measured density profiles to those given by numerical solutions of the transport equations, diffusion coefficients were obtained. At high magnetic field strengths the gun injected plasmas initially decayed in such a way as to indicate a diffusive mechanism which scaled like D/sub perpendicular to/ proportional to n/sup -0/ /sup 5/ dominated the transport, damping out on a time scale of milliseconds. The residual diffusion scaled like classical, D/sub perpendicular to/ proportional to/n/sub 2/, B, but was enhanced above classical by an order of magnitude. At lower values of magnetic field and of all times following injection, the diffusion scaled like classical, but again was an order of magnitude above classical.

Garner, H.R.

1982-01-01

200

Nonlinear diffusion regimes in stochastic magnetic fields  

International Nuclear Information System (INIS)

The transport of collisional particles in stochastic magnetic fields is studied using the decorrelation trajectory method. The nonlinear effect of magnetic line trapping is considered together with particle collisions. The running diffusion coefficient is determined for arbitrary values of the statistical parameters of the stochastic magnetic field and of the collisional velocity. New diffusion regimes are found in the conditions for which the trapping of magnetic field lines is effective. (author)

 
 
 
 
201

Magnetic field evolution in neutron stars  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Neutron stars contain persistent, ordered magnetic fields that are the strongest known in the Universe. However, their magnetic fluxes are similar to those in magnetic A and B stars and white dwarfs, suggesting that flux conservation during gravitational collapse may play an important role in establishing the field, although it might also be modified substantially by early convection, differential rotation, and magnetic instabilities. The equilibrium field configuration, est...

Reisenegger, Andreas

2007-01-01

202

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

203

Octupole states in the SO(6) limit  

International Nuclear Information System (INIS)

In this paper we treat the octupole states in even-even nuclei using a system consisting of f- boson and N-1 s+, d+ bosons. The SO(6) limiting case is emphasized and the analytic relations for energies and electromagnetic transition rates are derived. Finally the two-particle states are briefly discussed

204

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

205

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

206

Some aspects of self generated magnetic field  

International Nuclear Information System (INIS)

Self generated magnetic field is an important phenomenon in laser produced plasma and in astrophysical plasma. Several mechanisms for generation of axial and transverse fields are described here. Scaling laws for magnetic fields involving the laser parameters are also obtained. Detection of transverse and axial fields by measuring Faraday rotation is reported. (author). 23 refs., 3 figs

207

Quark stars under strong magnetic fields  

CERN Document Server

Within the confined-isospin-density-dependent-quark-mass model, we study the properties of strange quark matter (SQM) and quark stars (QSs) under strong magnetic fields. The equation of state of SQM under a constant magnetic field is obtained self-consistently and the pressure perpendicular to the magnetic field is shown to be larger than that parallel to the magnetic field, implying that the properties of magnetized QSs generally depend on both the strength and the orientation of the magnetic fields distributed inside the stars. Using a density-dependent magnetic field profile which is introduced to mimic the magnetic field strength distribution in a star, we study the properties of static spherical QSs by assuming two extreme cases for the magnetic field orientation in the stars, i.e., the radial orientation in which the local magnetic fields are along the radial direction and the transverse orientation in which the local magnetic fields are randomly oriented but perpendicular to the radial direction. Our r...

Chu, Peng-Cheng; Wang, Xin

2014-01-01

208

Chaotic motion of a nucleon in mean field potential with octupole deformation. Pt.2: Characteristics of expectation values and uncertainty measures of canonical variables in space-temporal variation of initial coherent states  

International Nuclear Information System (INIS)

Coherent states of two dimensional asymmetrical harmonic oscillator, which propagate in additional octupole deformation potentials, are used to investigate the characteristics of expectation values and uncertainty measures of canonical variables in space-temporal variations. The quantum chaotic system shows varying behaviors as the corresponding classical chaotic system does. Thus the characteristics of quantum chaos are associated with the geometric symmetry of the potential surface, specifically, the existence of the negative curvature and the magnitude of the curvature in the potential surface

209

Magnetic line trapping and effective transport in stochastic magnetic fields  

International Nuclear Information System (INIS)

The transport of collisional particles in stochastic magnetic fields is studied using the decorrelation trajectory method. The nonlinear effect of magnetic line trapping is considered together with particle collisions. The running diffusion coefficient is determined for arbitrary values of the statistical parameters of the stochastic magnetic field and of the collisional velocity. The effect of the magnetic line trapping is determined. New anomalous diffusion regimes are found

210

Magnetic field properties of SSC model dipole magnets  

International Nuclear Information System (INIS)

SSC 1.5 m model dipole magnets were built and tested at Fermilab. Magnetic field properties were studied in term of transfer function variation and multipole components. The results were satisfactory. Observation of periodicity of remanent field along the axis is also reported. Based on the model magnet experience, Fermilab has already built two successful full scale magnets. (author) 12 refs.; 3 figs.; 3 tabs

211

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

212

Electromagnetic showers in a strong magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We present the results concerning the main shower characteristics in a strong magnetic field obtained through shower simulation. The processes of magnetic bremsstrahlung and pair production were taken into account for values of the parameter $\\chi \\gg 1$. We compare our simulation results with a recently developed cascade theory in a strong magnetic field.

Anguelov, V.; Vankov, H.

2000-01-01

213

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

214

Inertial fusion reactors and magnetic fields  

International Nuclear Information System (INIS)

The application of magnetic fields of simple configurations and modest strengths to direct target debris ions out of cavities can alleviate recognized shortcomings of several classes of inertial confinement fusion (ICF) reactors. Complex fringes of the strong magnetic fields of heavy-ion fusion (HIF) focusing magnets may intrude into reactor cavities and significantly affect the trajectories of target debris ions. The results of an assessment of potential benefits from the use of magnetic fields in ICF reactors and of potential problems with focusing-magnet fields in HIF reactors conducted to set priorities for continuing studies are reported. Computational tools are described and some preliminary results are presented

215

Asymmetric Diffusion of Magnetic Field Lines  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

216

Topological constraints on magnetic field relaxation  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

217

The structure of helical interplanetary magnetic fields  

Science.gov (United States)

The interplanetary magnetic field is known to be highly helical. Although the detailed spatial structure of the fields has yet to be elucidated, the helicity spectrum has been conjectured to result from a random walk in the direction of a constant magnitude magnetic field vector. A model using three-dimensional fluctuations with variations in B is demonstrated giving a good fit to the helicity spectrum as well as to other properties of the interplanetary magnetic field.

Goldstein, M. L.; Roberts, D. A.; Fitch, C. A.

1991-01-01

218

ESA's magnetic field mission Swarm  

International Nuclear Information System (INIS)

Complete text of publication follows. Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme. The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution. The Mission shall deliver data that allow access to new insights into the Earth system by improving our understanding of the Earth's interior and climate. The mission is nominally scheduled for launch in 2011. After release from a single launcher, a side-by-side flying slowly decaying lower pair of satellites will be released at an initial altitude of about 490 km together with a third satellite that 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 that are required to separate and model various sources of the geomagnetic field and near-Earth current systems. At present the project is in the development phase. The current project status, product performance, and on-going scientific studies will be given special attention during the presentation.

219

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.

220

Electrolytic tiltmeters inside magnetic fields: Some observations  

Energy Technology Data Exchange (ETDEWEB)

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.

Alberdi, J. [CIEMAT, Madrid (Spain); Arce, P. [CIEMAT, Madrid (Spain); Barcala, J.M. [CIEMAT, Madrid (Spain); Calvo, E. [CIEMAT, Madrid (Spain); Ferrando, A. [CIEMAT, Madrid (Spain)]. E-mail: antonio.ferrando@ciemat.es; Josa, M.I. [CIEMAT, Madrid (Spain); Luque, J.M. [CIEMAT, Madrid (Spain); Molinero, A. [CIEMAT, Madrid (Spain); Navarrete, J. [CIEMAT, Madrid (Spain); Oller, J.C. [CIEMAT, Madrid (Spain); Yuste, C. [CIEMAT, Madrid (Spain); Calderon, A. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Garcia-Moral, L.A. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Gomez, G. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Gonzalez-Sanchez, F.J. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Martinez-Rivero, C. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Matorras, F. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Rodrigo, T. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Ruiz-Arbol, P. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Scodellaro, L. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Sobron, M. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Vila, I. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain); Virto, A.L. [Instituto de Fisica de Cantabria, CSIC-University of Cantabria, Santander (Spain)

2007-04-21

 
 
 
 
221

Magnetic Field Exposure and Cancer: Questions and Answers  

Science.gov (United States)

Magnetic Field Exposure and Cancer: Questions and Answers Key Points Electric and magnetic fields (EMF) are areas of energy that surround ... or weakened by walls and other objects, whereas magnetic fields are not. Since magnetic fields are more ...

222

Aggregation of magnetic holes in a rotating magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We have experimentally investigated field induced aggregation of nonmagnetic particles confined in a magnetic fluid layer when rotating magnetic fields were applied. After application of a magnetic field rotating in the plane of the fluid layer, the single particles start to form two-dimensional (2D) clusters, like doublets, triangels, and more complex structures. These clusters aggregated again and again to form bigger clusters. During this nonequilibrium process, a broad r...

C?erna?k, Jozef; Helgesen, Geir

2008-01-01

223

Bipolar pulse field for magnetic refrigeration  

Science.gov (United States)

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

Lubell, Martin S. (Oak Ridge, TN)

1994-01-01

224

Magnetic fields of Sun-like stars  

CERN Document Server

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

Fares, R

2013-01-01

225

Quarks and gluons in a magnetic field  

CERN Document Server

The quark gap equation under the rainbow truncation, with two versions of a phenomenological one-gluon exchange interaction and in the presence of a uniform magnetic field is considered. It is argued that in order to describe the quark condensate in the limit of vanishing magnetic fields, one must sum over the Landau levels. The resulting chiral quark condensate rises quadratically for small magnetic fields and linearly for large fields, in qualitative agreement with various recent lattice results. It is observed that when discussing quarks, the magnitude of the magnetic field must be considered relative to the scale of the strong interaction.

Watson, Peter

2013-01-01

226

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

227

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

228

Advances in Remote Sensing of Magnetic Fields  

Science.gov (United States)

In sharp contrast to stellar magnetic fields, geomagnetic fields have never been remotely sensed. If geomagnetic fields could be measured remotely at the nanotesla (nT) level or better, our understanding of the processes that produce these fields would advance markedly. Unlike characteristics such as topography and temperature, measurements of the magnetic field are determined almost exclusively in situ. The inability to remotely sense these fields has hindered their utility. The Remote Atmospheric Magnetics Workshop highlighted advances in this frontier area, focusing on lab- and field-based studies.

Purucker, Michael

2014-09-01

229

Relativistic stars with purely toroidal magnetic fields  

CERN Document Server

We investigate the effects of the purely toroidal magnetic field on the equilibrium structures of the relativistic stars. The master equations for obtaining equilibrium solutions of relativistic rotating stars containing purely toroidal magnetic fields are derived for the first time. To solve these master equations numerically, we extend the Cook-Shapiro-Teukolsky scheme for calculating relativistic rotating stars containing no magnetic field to incorporate the effects of the purely toroidal magnetic fields. By using the numerical scheme, we then calculate a large number of the equilibrium configurations for a particular distribution of the magnetic field in order to explore the equilibrium properties. We also construct the equilibrium sequences of the constant baryon mass and/or the constant magnetic flux, which model the evolution of an isolated neutron star as it loses angular momentum via the gravitational waves. Important properties of the equilibrium configurations of the magnetized stars obtained in th...

Kiuchi, Kenta

2008-01-01

230

Dilute Potts chain in a magnetic field  

International Nuclear Information System (INIS)

The Potts lattice gas in presence of a uniform magnetic field is solved exactly in one dimension. For negative values of the exchange parameter, the magnetization curve exhibits two or three steps, depending on the concentration of vacancies. These steps arise as a result of the competition between the exchange interaction and the magnetic field, being associated to different structural distribution of vacancies and to the magnetic ordering of one or both sublattices. (Author)

231

A carpet cloak for static magnetic field  

Science.gov (United States)

We present a two-dimensional carpet cloak for static magnetic field, a design that renders the magnetic response of a given volume invisible from its exterior, without altering the external magnetic fields. The device is designed using transformation optics method and can be implemented with alternating superconducting and magnetic material layers. Through the proper design of the constitutive tensors and relative thicknesses of each slab, we achieve the perfect performance of invisibility. Full wave numerical simulations confirm our design.

Wang, Rongfeng; Lei Mei, Zhong; Jun Cui, Tie

2013-05-01

232

Spontaneous magnetic fields in spherical laser targets  

International Nuclear Information System (INIS)

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

233

Steady high magnetic field facilities at ASIPP  

International Nuclear Information System (INIS)

Steady magnetic fields up to 20 T have been generated at the Institute of Plasma Physics, Academia Sinica (ASIPP), by a hybrid magnet consisting of an outer NbTi superconducting coil and an inner water-cooled Bitter coil in support of the research in high magnetic fields. This hybrid magnet with the other laboratory magnets, i.e. the water-cooled magnets with fields up to 14 T and the superconducting magnets capable of producing 8.0 T in different bores have been opened to the scientific community since 1992 and extensive studies on high Tc superconductors, semi-conductors, magnetic materials low-dimensional organic conductors as well as the chemical and biological effects of the high magnetic fields etc. have been conducted. To cope with the increasing demand for high fields and more magnet time, the 20 T hybrid magnet is ready to upgrade to 23 T. Based on the use of 40 MW fly-wheel generator power a future plan for constructing a 45T, 2 s flat-top quasisteady magnet has been proposed for creating new scientific opportunities at higher fields

234

FLINESH computer code for magnetic fields calculation  

International Nuclear Information System (INIS)

This paper describes the 'FLINESH' computer code for magnetic fields calculation developed for the simulation of field configurations in plasma magnetic confinement devices. The expressions for the poloidal field and flux, the program structure and the input parameters description are presented, and also the analysis of the graphic output possibilities. (L.C.J.A.). 12 refs, 14 figs, 2 tabs

235

Relativistic hydrogenic atoms in strong magnetic fields  

CERN Document Server

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

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

2006-01-01

236

High magnetic fields science and technology  

CERN Document Server

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

Miura, Noboru

2003-01-01

237

Dirac neutrinos and primordial magnetic fields  

International Nuclear Information System (INIS)

We consider random primordial magnetic fields and discuss their dissipation, coherence length L0, scaling behaviour and constraints implied by the primordial nucleosynthesis. Such magnetic fields could excite the right-helicity states of Dirac neutrinos, with adverse consequences for nucleosynthesis. We present solutions to the spin kinetic equation of a Dirac neutrino traversing a random magnetic field in the cases of large and small L0, taking also into account elastic collisions. Depending on the scaling behaviour and on the magnetic coherence length, the lower limit on the neutrino magnetic moment thus obtained could be as severe as 10-20?B. ((orig.))

238

Synchrotron Applications of High Magnetic Fields  

Energy Technology Data Exchange (ETDEWEB)

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

NONE

2006-07-01

239

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

240

Coulomb crystals in the magnetic field  

CERN Document Server

The body-centered cubic Coulomb crystal of ions in the presence of a uniform magnetic field is studied using the rigid electron background approximation. The phonon mode spectra are calculated for a wide range of magnetic field strengths and for several orientations of the field in the crystal. The phonon spectra are used to calculate the phonon contribution to the crystal energy, entropy, specific heat, Debye-Waller factor of ions, and the rms ion displacements from the lattice nodes for a broad range of densities, temperatures, chemical compositions, and magnetic fields. Strong magnetic field dramatically alters the properties of quantum crystals. The phonon specific heat increases by many orders of magnitude. The ion displacements from their equilibrium positions become strongly anisotropic. The results can be relevant for dusty plasmas, ion plasmas in Penning traps, and especially for the crust of magnetars (neutron stars with superstrong magnetic fields $B \\gtrsim 10^{14}$ G). The effect of the magnetic ...

Baiko, D A

2009-01-01

 
 
 
 
241

Magnetic nanoparticle sensing: decoupling the magnetization from the excitation field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

242

Comparing magnetic field extrapolations with measurements of magnetic loops  

CERN Document Server

We compare magnetic field extrapolations from a photospheric magnetogram with the observationally inferred structure of magnetic loops in a newly developed active region. This is the first time that the reconstructed 3D-topology of the magnetic field is available to test the extrapolations. We compare the observations with potential fields, linear force-free fields and non-linear force-free fields. This comparison reveals that a potential field extrapolation is not suitable for a reconstruction of the magnetic field in this young, developing active region. The inclusion of field-line-parallel electric currents, the so called force-free approach, gives much better results. Furthermore, a non-linear force-free computation reproduces the observations better than the linear force-free approximation, although no free parameters are available in the former case.

Wiegelmann, T; Solanki, S K; Inhester, B; Woch, J

2008-01-01

243

Very Light Extragalactic Jets with Magnetic Fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We explore the global structure and evolution of powerful radio sources located in clusters of galaxies and their interaction with the ambient gas, in particular with respect to the effects of magnetic fields. Recent observations of inverse-Compton emission from their cocoons at X-ray energies indicate that magnetic fields are present on a considerable (near-equipartition) level. To investigate the impact of magnetic fields on dynamics and morphology, we performed a series of magnetohydrodyna...

Gaibler, Volker

2008-01-01

244

Magnetic field screening effect in electroweak model  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

245

Magnetic Field Instabilities in Neutron Stars  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

246

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

247

Graphene spin capacitor for magnetic field sensing  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

248

Evolution of superhigh magnetic fields of magnetars  

CERN Document Server

In this paper, we consider the effect of Landau levels on the decay of superhigh magnetic fields of magnetars. Applying ${}^3P_2$ anisotropic neutron superfluid theory yield a second-order differential equation for a superhigh magnetic field $B$ and its evolutionary timescale $t$. The superhigh magnetic fields may evolve on timescales $\\sim (10^{6}-10^{7})$ yrs for common magnetars. According to our model, the activity of a magnetar may originate from instability caused by the high electron Fermi energy.

Gao, Z F; Yuan, J P; Jiang, L; Song, D L; Qiao, E L

2013-01-01

249

Multielectronic Atom in Magnetic Field Revisited  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

250

Magnetic Field of Relativistic Nonlinear Plasma Wave  

CERN Document Server

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 plasma wave. The numerical results well conform with predictions of the analytical consideration of weakly-nonlinear case.

Khachatrian, A G

2000-01-01

251

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

252

Statistics of magnetic fields on OBA stars  

Science.gov (United States)

Starting from recent measurements, we studied the statistical properties of the magnetic fields of OBA stars. As one of the statistically significant characteristics of the magnetic field we use the average effective magnetic field of the star, . We then investigated the distribution function f() of the magnetic fields of OBA stars. This function has a power-law dependence on , with an index of 2-3 and a fast decrease for ? 300 G for B-A stars and ? 80 G for O stars.

Kholtygin, A. F.; Hubrig, S.; Drake, N. A.; Sudnik, N. P.; Dushin, V. V.

2014-11-01

253

Magnetic monopole field exposed by electrons  

Science.gov (United States)

The experimental search for magnetic monopole particles has, so far, been in vain. Nevertheless, these elusive particles of magnetic charge have fuelled a rich field of theoretical study. Here, we created an approximation of a magnetic monopole in free space at the end of a long, nanoscopically thin magnetic needle. We experimentally demonstrate that the interaction of this approximate magnetic monopole field with a beam of electrons produces an electron vortex state, as theoretically predicted for a true magnetic monopole. This fundamental quantum mechanical scattering experiment is independent of the speed of the electrons and has consequences for all situations where electrons meet such monopole magnetic fields, as, for example, in solids. The set-up not only shows an attractive way to produce electron vortex states but also provides a unique insight into monopole fields and shows that electron vortices might well occur in unexplored solid-state physics situations.

Béché, Armand; van Boxem, Ruben; van Tendeloo, Gustaaf; Verbeeck, Jo

2014-01-01

254

Concentrator of magnetic field of light  

Science.gov (United States)

In the recent decade metamaterials with magnetic permeability different than unity and unusual response to the magnetic field of incident light have been intensively explored. Existence of magnetic artificial materials created an interest in a scanning near-field magnetic microscope for studies of magnetic responses of subwavelength elementary cells of those metamaterials. We present a method of measuring magnetic responses of such elementary cells within a wide range of optical frequencies with single probes of two types. The first type probe is made of a tapered silica fiber with radial metal stripes separated by equidistant slits of constant angular width. The second type probe is similar to metal coated, corrugated, tapered fiber apertured SNOM probe, but in this case corrugations are radially oriented. Both types of probes have internal illumination with azimuthally polarized light. In the near-field they concentrate into a subwavelength spot the longitudinal magnetic field component which is much stronger than the perpendicular electric one.

Wróbel, Piotr; Stefaniuk, Tomasz; Antosiewicz, Tomasz J.; Szoplik, Tomasz

2012-05-01

255

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

256

Magnetotransport in a spatially modulated magnetic field  

Scientific Electronic Library Online (English)

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

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

257

Electro-magnetically induced transparency in a static magnetic field  

Science.gov (United States)

We investigate both theoretically and experimentally the electro- magnetically induced transparency (EIT) phenomenon of atomic 87Rb at the room temperature with a static magnetic field lifting the degeneracy of all three involved hyperfine levels. Two collinearly propagating and linearly polarized laser fields (a probe field and a coupling field) are used to couple one hyperfine level (the upper level) of the 5P 1/2 state to two hyperfine levels (the lower levels) of the 5S 1/2 state, respectively. In the case of zero magnetic fields, we observed a deep EIT window with the contrast of about 66%. Here, the EIT window width is limited by both the spontaneous decay rate of the upper level and the coupling field intensity. When a magnetic field parallel to both laser beams is applied, the EIT window is split into three much narrower sub-windows with contrasts of about 32%. If the magnetic field is perpendicular to the laser beams, however, the EIT window is split into four much narrower sub-windows whose contrasts are 32% or 16%. This is because the decomposition of the linearly polarized optical fields strongly depends on the orientation of the used magnetic field. The underlying physics is that, in the limit of a weak probe field, an ideal degenerate three-level system can be split into three or four sets of independent three-level systems by a magnetic field due to the lifting of magnetic sublevels of the involved hyperfine levels. In this paper the absorption spectra corresponding to different magnetic field directions are clearly shown and compared. And a straightforward but effective theoretical method for analyzing the experimental results is put forward. Our theoretical calculations are in good agreement with the experimental results.

Wei, Xiao-Gang; Gao, Jin-Yue; Wu, Jin-Hui; Sun, Gui-Xia; Wang, Hai-Hua; Kang, Zhi-Hui; Shao, Zhuang; Jiang, Yun

2006-02-01

258

Magnetic field properties of SSC model dipole magnets  

International Nuclear Information System (INIS)

SSC 1.5m model dipole magnets were built and tested at Fermilab. Magnetic field properties were studied in term of transfer function variation and multipole components. The results were satisfactory. Observation of periodicity of remanent field along the axis is also reported

259

Magnetic field properties of SSC model dipole magnets  

Energy Technology Data Exchange (ETDEWEB)

SSC 1.5m model dipole magnets were built and tested at Fermilab. Magnetic field properties were studied in term of transfer function variation and multipole components. The results were satisfactory. Observation of periodicity of remanent field along the axis is also reported.

Wake, M.; Bossert, R.; Carson, J.; Delchamps, S.; Jaffery, T.S.; Kinney, W.; Koska, W.; Lamm, M.J.; Strait, J. [Fermi National Accelerator Lab., Batavia, IL (United States); Butteris, J.; Sims, R.; Winters, M. [Superconducting Super Collider Lab., Dallas, TX (United States)

1992-09-01

260

Magnetic field helicity in a coaxial discharge  

International Nuclear Information System (INIS)

The behavior of the dynamic sheath was studied for 4.4 kJ coaxial electrode discharge device operated with hydrogen gas at a pressure of 0.85 Torr. In normal mode operation, i.e. Without external magnetic field, it has been found that an induced axial magnetic field along the coaxial electrodes is created. With the application of 3.6 kg external axial magnetic field along the coaxial electrodes, both the plasma sheath current in the azimuthal direction, and the axial magnetic field, increased by about 2 times; during the first half cycle of discharge. For the second half cycle, results indicated that the self induced field is less than the applied axial magnetic field along the coaxial electrode. The applied field increase the rotating sheath current by 1.2 times. The experimental results of the azimuthal component of magnetic field B 0 along the axial electrodes indicated that ; the application of external magnetic field causes a decrease of B 0 to about 90%. Magnetic field helicity in a coaxial discharge. 4 figs

 
 
 
 
261

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

262

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.)

263

High ? studies in the Wisconsin Toroidal Octupole  

International Nuclear Information System (INIS)

A wide range of MHD stable high ? plasmas is produced in the Wisconsin Levitated Octupole. At or near the single fluid regime we obtain, in the bad curvature region, ? = nk(T/sub e/ + T/sub i/)8?/B2 approx. = 8%, twice the theoretical single fluid ballooning instability limit of 4%. We also obtain stable plasmas at ? approx. = 35%, 9 times the theoretical limit, in a regime in which both finite ion gyroradius and gyroviscosity effects are important

264

Studies of a poloidal divertor reversed field pinch  

International Nuclear Information System (INIS)

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

265

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.)

266

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)

267

Magnetic field test coils are temperature compensated  

Science.gov (United States)

Magnetic field test coils with auxiliary winding wound opposite to main coil winding eliminates changes in field configurations due to temperature changes. The auxiliary coil is made with aluminum wire.

1965-01-01

268

Magnetic field decay in model SSC dipoles  

International Nuclear Information System (INIS)

We have observed that some of our model SSC dipoles have long time constant decays of the magnetic field harmonics with amplitudes large enough to result in significant beam loss, if they are not corrected. The magnets were run at constant current at the SSC injection field level of 0.3 tesla for one to three hours and changes in the magnetic field were observed. One explanation for the observed field decay is time dependent superconductor magnetization. Another explanation involves flux creep or flux flow. Data are presented on how the decay changes with previous flux history. Similar magnets with different Nb-Ti filament spacings and matrix materials have different long time field decay. A theoretical model using proximity coupling and flux creep for the observed field decay is discussed. 10 refs., 5 figs., 2 tabs

269

Magnetic field decay in model SSC dipoles  

International Nuclear Information System (INIS)

The authors have observed that some of our model SSC dipoles have long time constant decays of the magnetic field harmonics with amplitudes large enough to result in significant beam loss, if they are not corrected. The magnets were run at constant current at the SSC injection field level of 0.3 tesla for one to three hours and changes in the magnetic field were observed. One explanation for the observed field decay is time dependent superconductor magnetization. Another explanation involves flux creep or flux flow. Data are presented on how the decay changes with previous flux history. Similar magnets with different Nb-Ti filament spacings and matrix materials have different long term field decay. A theoretical model using proximity coupling and flux creep for the observed field decay is discussed

270

Effects of primordial magnetic fields on CMB  

CERN Document Server

The origin of large-scale magnetic fields is an unsolved problem in cosmology. In order to overcome, a possible scenario comes from the idea that these fields emerged from a small primordial magnetic field (PMF), produced in the early universe. This field could lead to the observed large-scales magnetic fields but also, would have left an imprint on the cosmic microwave background (CMB). In this work we summarize some statistical properties of this PMFs on the FLRW background. Then, we show the resulting PMF power spectrum using cosmological perturbation theory and some effects of PMFs on the CMB anisotropies.

Hortua, Hector J

2014-01-01

271

Single-layer high field dipole magnets  

Energy Technology Data Exchange (ETDEWEB)

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

Vadim V. Kashikhin and Alexander V. Zlobin

2001-07-30

272

Extended Magnetization of Superconducting Pellets in Highly Inhomogeneous Magnetic Field  

Science.gov (United States)

The magnetization of superconducting pellets is a worth point in the development of trapped flux superconducting motors. Experimental and simulated data have been reported extensively according to the framework of one or several pulses of a homogeneous magnetizing field applied to a pellet or a set of pellets. In case of cylindrical rotors of low power motors with radial excitation, however, the use of the copper coils to produce the starting magnetization of the pellets produces a highly inhomogeneous magnetic field which cannot be reduced to a 2D standard model. In this work we present an analysis of the magnetization of the superconducting cylindrical rotor of a small motor by using a commercial FEM program, being the rotor magnetized by the working copper coils of the motor. The aim of the study is a report of the magnetization obtained and theheat generated in the HTSC pellets.

Maynou, R.; López, J.; Granados, X.; Torres, R.; Bosch, R.

273

The magnetic field of $\\zeta$ Ori A  

CERN Document Server

Magnetic fields play a significant role in the evolution of massive stars. About 7% of massive stars are found to be magnetic at a level detectable with current instrumentation and only a few magnetic O stars are known. Detecting magnetic field in O stars is particularly challenging because they only have few, often broad, lines to measure the field, which leads to a deficit in the knowledge of the basic magnetic properties of O stars. We present new spectropolarimetric Narval observations of $\\zeta$ Ori A. We also provide a new analysis of both the new and older data taking binarity into account. The aim of this study was to confirm the presence of a magnetic field in $\\zeta$ Ori A. We identify that it belongs to $\\zeta$ Ori Aa and characterize it.

Blazère, A; Bouret, J-C; Tkachenko, A

2014-01-01

274

Hybrid stars in a strong magnetic field  

Energy Technology Data Exchange (ETDEWEB)

We study the effects of high magnetic fields on the particle population and equation of state of hybrid stars using an extended hadronic and quark SU(3) non-linear realization of the sigma model. In this model the degrees of freedom change naturally from hadrons to quarks as the density and/or temperature increases. The effects of high magnetic fields and anomalous magnetic moment are visible in the macroscopic properties of the star, such as mass, adiabatic index, moment of inertia, and cooling curves. Moreover, at the same time that the magnetic fields become high enough to modify those properties, they make the star anisotropic. (orig.)

Dexheimer, V. [UFSC, Florianopolis (Brazil); Gettysburg College, Gettysburg, PA (United States); Negreiros, R. [Johann Wolfgang Goethe University, FIAS, Frankfurt (Germany); UFF, Instituto de Fisica, Niteroi (Brazil); Schramm, S. [Johann Wolfgang Goethe University, FIAS, Frankfurt (Germany)

2012-12-15

275

Magnetic isotope and magnetic field effects on the DNA synthesis.  

Science.gov (United States)

Magnetic isotope and magnetic field effects on the rate of DNA synthesis catalysed by polymerases ? with isotopic ions (24)Mg(2+), (25)Mg(2+) and (26)Mg(2+) in the catalytic sites were detected. No difference in enzymatic activity was found between polymerases ? carrying (24)Mg(2+) and (26)Mg(2+) ions with spinless, non-magnetic nuclei (24)Mg and (26)Mg. However, (25)Mg(2+) ions with magnetic nucleus (25)Mg were shown to suppress enzymatic activity by two to three times with respect to the enzymatic activity of polymerases ? with (24)Mg(2+) and (26)Mg(2+) ions. Such an isotopic dependence directly indicates that in the DNA synthesis magnetic mass-independent isotope effect functions. Similar effect is exhibited by polymerases ? with Zn(2+) ions carrying magnetic (67)Zn and non-magnetic (64)Zn nuclei, respectively. A new, ion-radical mechanism of the DNA synthesis is suggested to explain these effects. Magnetic field dependence of the magnesium-catalysed DNA synthesis is in a perfect agreement with the proposed ion-radical mechanism. It is pointed out that the magnetic isotope and magnetic field effects may be used for medicinal purposes (trans-cranial magnetic treatment of cognitive deceases, cell proliferation, control of the cancer cells, etc). PMID:23851636

Buchachenko, Anatoly L; Orlov, Alexei P; Kuznetsov, Dmitry A; Breslavskaya, Natalia N

2013-09-01

276

Magnetic Fields in Stars: Origin and Impact  

CERN Document Server

Various types of magnetic fields occur in stars: small scale fields, large scale fields, and internal toroidal fields. While the latter may be ubiquitous in stars due to differential rotation, small scale fields (spots) may be associated with envelop convection in all low and high mass stars. The stable large scale fields found in only about 10 per cent of intermediate mass and massive stars may be understood as a consequence of dynamical binary interaction, e.g., the merging of two stars in a binary. We relate these ideas to magnetic fields in white dwarfs and neutron stars, and to their role in core-collapse and thermonuclear supernova explosions.

Langer, N

2013-01-01

277

On interplanetary electric and magnetic fields  

International Nuclear Information System (INIS)

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

278

Programming the control of magnetic field measurements  

International Nuclear Information System (INIS)

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

279

Magnetic Fields and Rotations of Protostars  

CERN Document Server

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

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

2007-01-01

280

Photon-neutrino interactions in magnetic fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The low-energy two neutrino-two photon interactions in the presence of homogeneous magnetic field are studied. The cross sections in external magnetic field are shown to be larger than in vacuum by factor $\\sim (m_W /m_e) ^4(B/B_c) ^2$. The energy-loss rate due to the process $\\gamma \\gamma \\to \

R, Shaisultanov

1997-01-01

 
 
 
 
281

On the origins of galactic magnetic fields  

CERN Document Server

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

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

2009-01-01

282

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

283

Lattice Planar QED in external magnetic field  

Science.gov (United States)

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

Cea, P.; Cosmai, L.; Giudice, P.; Papa, A.

284

Lattice Planar QED in external magnetic field  

CERN Document Server

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

Cea, Paolo; Giudice, Pietro; Papa, Alessandro

2011-01-01

285

Vacuum magnetic fields with dense flux surfaces  

Energy Technology Data Exchange (ETDEWEB)

A procedure is given for eliminating resonances and stochasticity in nonaxisymmetric vacuum toroidal magnetic field. The results of this procedure are tested by the surface of section method. It is found that one can obtain magnetic fields with increased rotational transform and decreased island structure while retaining basically the same winding law.

Cary, J R

1982-05-01

286

Permanent magnet edge-field quadrupole  

Science.gov (United States)

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

Tatchyn, Roman O. (Mountain View, CA)

1997-01-01

287

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

288

Alignment of magnetic uniaxial particles in a magnetic field: Simulation  

Science.gov (United States)

The numerical investigations of the process of alignment of magnetically uniaxial Nd-Fe-B powders in an applied magnetic field were carried out using the discrete element method (DEM). It is shown that magnetic alignment of ensemble of spherical particles provides extremely high degree of alignment, which is achieved in low magnetic fields. A model of formation of anisotropic particles as a combination of spherical particles is suggested. The influence of the shape anisotropy and friction coefficient on the alignment degree was analyzed. The increase in the friction coefficient leads to a decrease in the alignment degree; the simulation results are in qualitative agreement with experimental dependences. It is shown that in magnetic fields higher than 5 T, the calculated field dependences of the alignment degree quantitatively render the experimental data. The increase of about 6% in the alignment degree in the experiments with addition of internal lubricant can be explained by the decrease of 14% in friction coefficient.

Golovnia, O. A.; Popov, A. G.; Sobolev, A. N.; Hadjipanayis, G. C.

2014-09-01

289

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

290

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

291

Magnetic reconnection driven by emergence of sheared magnetic field.  

Science.gov (United States)

Recurrent subflares (Class C) were observed in the NOAA 7608 active region on 27 October 1993. From multi-wavelength observations (white-light, magnetic field, H-alpha, X-ray), obtained during a coordinated campaign between Pic du Midi and Yohkoh, it appears that these flares were double ribbon flares caused by new flux emergence. As the flare begins, the X-ray emission observed with Yohkoh/SXT is loop-shaped with the axis almost parallel to the magnetic inversion line, while during the flare development, X-ray loops appear at the location of the emerging flux. The extrapolation of the photospheric magnetic field in a linear force-free field configuration allows identification of the magnetic configuration given by the flares. The H? flare ribbons are located at the intersections of the computed quasi-separatrice layers (QSLs) with the chromosphere. We show that the initial loop-shaped X-ray emission region is in fact formed by several smaller loops directed in a nearly orthogonal direction with their feet anchored close to or in the H? ribbons. During the flare development there are X-ray loops which represent only one foot of open or largescale magnetic loops. For the studied flares the puzzling soft X-rays observations could only be understood with the help of H? and magnetic data combined with a modeling of the coronal magnetic field. Further, from the deduced magnetic field topology, the width of the QSLs and our present knowledge of 3-D magnetic reconnection, we conclude that the flare was due to magnetic reconnection driven by emergence of sheared magnetic field impacting in the pre-existing coronal field.

Schmieder, B.; Aulanier, G.; Demoulin, P.; van Driel-Gesztelyi, L.; Roudier, T.; Nitta, N.; Cauzzi, G.

1997-09-01

292

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)

293

Magnetic Fields in the Solar Convection Zone  

Directory of Open Access Journals (Sweden)

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

Fan Yuhong

2004-07-01

294

Structure of magnetic fields in intracluster cavities  

CERN Document Server

Observations of clusters of galaxies show ubiquitous presence of X-ray cavities, presumably blown by the AGN jets. We consider magnetic field structures of these cavities. Stability requires that they contain both toroidal and poloidal magnetic fields, while realistic configurations should have vanishing magnetic field on the boundary. For axisymmetric configurations embedded in unmagnetized plasma, the continuity of poloidal and toroidal magnetic field components on the surface of the bubble then requires solving the elliptical Grad-Shafranov equation with both Dirichlet and Neumann boundary conditions. This leads to a double eigenvalue problem, relating the pressure gradients and the toroidal magnetic field to the radius of the bubble. We have found fully analytical stable solutions. This result is confirmed by numerical simulation. We present synthetic X-ray images and synchrotron emission profiles and evaluate the rotation measure for radiation traversing the bubble.

Gourgouliatos, Konstantinos Nektarios; Lyutikov, Maxim

2010-01-01

295

Orienting Paramecium with intense static magnetic fields  

Science.gov (United States)

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

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

2004-03-01

296

Coulomb Clusters in Axial Magnetic Field  

International Nuclear Information System (INIS)

The rotation of Coulomb clusters with different numbers of micron-sized particles is observed in an inductively coupled dusty plasma in the presence of an axial magnetic field. The rotation is found to be dependent on the particle number and configuration. Clusters with smaller numbers of particles require a higher magnetic field strength in order to initiate the rotation, the threshold magnetic field at which the cluster begins to rotate being proportional to the square of the number of particles in the cluster. The angular velocity of clusters increases and the radius of the clusters decreases as the magnetic field strength is increased. The relation between angular velocity and magnetic field is dependent on the number of particles in the cluster

297

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

298

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

299

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.

300

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

 
 
 
 
301

Comparison of adjustable permanent magnetic field sources  

Energy Technology Data Exchange (ETDEWEB)

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

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

2010-11-15

302

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

303

Horizontal Magnetic Fields in the Solar Photosphere  

CERN Document Server

The results of 2D MHD simulations of solar magnetogranulation are used to analyze the horizontal magnetic fields and the response of the synthesized Stokes profiles of the FeI 1564.85 nm line to the magnetic fields. Selected 1.5-h series of the 2D MHD models reproduces a region of the network fields with their immediate surrounding on the solar surface with the unsigned magnetic flux density of 192 G. According to the magnetic field distribution obtained, the most probable absolute strength of the horizontal magnetic field at an optical depth of tau_5 = 1 (tau_5 denotes tau at lambda = 500 nm) is 50 G, while the mean value is 244 G. On average, the horizontal magnetic fields are stronger than the vertical fields to heights of about 400 km in the photosphere due to their higher density and the larger area they occupy. The maximum factor by which the horizontal fields are greater is 1.5. Strong horizontal magnetic flux tubes emerge at the surface as spots with field strengths of more than 500 G. These are small...

Sheminova, V A

2009-01-01

304

Fractal properties of solar magnetic fields  

Science.gov (United States)

We study the spatial properties of solar magnetic fields using data from the Solar Vector Magnetograph of the Marshall Space Flight Center (MSFC) (FeI 5250.2 Å) and SOHO/MDI longitudinal magnetic field measurements (Ni 6767.8 Å) (96-min full-disk maps). Our study is focused on two objects: the fractal properties of sunspots and the fractal properties of the spatial magnetic field distribution of active and quiet regions considered as global structures. To study the spatial structure of sunspots, we use a well-known method of determining the fractal dimension based on an analysis of the perimeter—area relation. To analyze the fractal properties of the spatial magnetic field distribution over the solar surface, we use a technique developed by Higuchi. We have revealed the existence of three families of self-similar contours corresponding to the sunspot umbra, penumbra, and adjacent photosphere. The fractal coefficient has maxima near the umbra—penumbra and penumbra—photosphere boundaries. The fractal dependences of the longitudinal and transverse magnetic field distributions are similar, but the fractal numbers themselves for the transverse fields are larger than those for the longitudinal fields approximately by a factor of 1.5. The fractal numbers decrease with increasing mean magnetic field strength, implying that the magnetic field distribution is more regular in active regions.

Ioshpa, B. A.; Obridko, V. N.; Rudenchik, E. A.

2008-03-01

305

Chaotic magnetic fields: Particle motion and energization  

Energy Technology Data Exchange (ETDEWEB)

Magnetic field line equations correspond to a Hamiltonian dynamical system, so the features of a Hamiltonian systems can easily be adopted for discussing some essential features of magnetic field lines. The integrability of the magnetic field line equations are discussed by various authors and it can be shown that these equations are, in general, not integrable. We demonstrate several examples of realistic chaotic magnetic fields, produced by asymmetric current configurations. Particular examples of chaotic force-free field and non force-free fields are shown. We have studied, for the first time, the motion of a charged particle in chaotic magnetic fields. It is found that the motion of a charged particle in a chaotic magnetic field is not necessarily chaotic. We also showed that charged particles moving in a time-dependent chaotic magnetic field are energized. Such energization processes could play a dominant role in particle energization in several astrophysical environments including solar corona, solar flares and cosmic ray propagation in space.

Dasgupta, Brahmananda [CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Ram, Abhay K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Li, Gang [Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 and CSPAR, University of Alabama in Huntsville, Huntsville, AL 35805 (United States); Li, Xiaocan [Department of Physics, University of Alabama in Huntsville, Huntsville, AL 35899 (United States)

2014-02-11

306

Chaotic magnetic fields: Particle motion and energization  

International Nuclear Information System (INIS)

Magnetic field line equations correspond to a Hamiltonian dynamical system, so the features of a Hamiltonian systems can easily be adopted for discussing some essential features of magnetic field lines. The integrability of the magnetic field line equations are discussed by various authors and it can be shown that these equations are, in general, not integrable. We demonstrate several examples of realistic chaotic magnetic fields, produced by asymmetric current configurations. Particular examples of chaotic force-free field and non force-free fields are shown. We have studied, for the first time, the motion of a charged particle in chaotic magnetic fields. It is found that the motion of a charged particle in a chaotic magnetic field is not necessarily chaotic. We also showed that charged particles moving in a time-dependent chaotic magnetic field are energized. Such energization processes could play a dominant role in particle energization in several astrophysical environments including solar corona, solar flares and cosmic ray propagation in space

307

Magnetic field line reconnection in structurally unstable magnetic configurations  

International Nuclear Information System (INIS)

The transformation of structurally unstable magnetic configurations into structurally stable ones is studied both analytically and numerically. This transformation, which is forbidden in the ideal magnetohydrodynamics, is shown to occur in the process of magnetic field line reconnection. The regions near magnetic null lines of high orders are examined. Azimuthally symmetric perturbations are shown to cause the formation of a finite-size current region bounded by magnetic separatrices. It is shown that, as a result of asymmetric perturbations, configurations involving current sheets with different polarities arise at magnetic separatrices

308

Influence of AC external magnetic field perturbation on trapped magnetic field in HTS bulk  

International Nuclear Information System (INIS)

Electric motors and actuators are most promising future applications of HTS bulks. The HTS bulks in these electric machines are exposed to AC magnetic field perturbations. The perturbations cause AC losses in the bulks and also affect the magnetic field trapped in the bulks. In a previous work we measured AC losses in a YBCO bulk subject to the AC magnetic field and found the loss characteristics well followed the Bean model. In this work we experimentally studied the influence of the AC perturbations of the external magnetic field on the trapped field in a YBCO bulk. The experimental results showed that the application of the AC magnetic field decreased the trapped magnetic field even to zero. In this paper, the experimental results are presented and a reason for the decay of the trapped magnetic field is discussed based on the Bean model

309

Magnetic field structure evolution in RMF plasmas  

Science.gov (United States)

A study of magnetic field structure evolution during 40-ms plasma discharge had been performed in 80 cm long / 40 cm OD cylindrical chamber. Plasma current Ip˜2--3 kA is produced by applied 500 kHz rotating magnetic field. In experiments, the 2D profile of plasma current is changed by feeding a 10-ms pulse current to additional magnetic coil located at the midplane. Using newly developed magnetic field pick-up coils system, we scanned the magnetic field in cross-section of plasma. Two experimental regimes were studied: without external toroidal field (TF), and with TF produced by applied axial current. When a relatively small current (coil, in both cases the total plasma current measured with Rogowski coil experiences a jump (up to 100%), but the profile of current remains almost unchanged. When a larger current (1--2 kA) is applied to the midplane coil, the total plasma current drops; the magnetic structure changes differently in two regimes. In regime without TF, the magnetic field of plasma current is reversed at Rmagnetic field evolves during initial 1--3 ms transitional period of plasma formation.

Petrov, Yuri; Yang, Xiaokang; Huang, Tian-Sen

2007-11-01

310

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

311

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

312

Sonoluminescence: Coupling to an applied magnetic field  

Science.gov (United States)

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 for comparable magnetic fields involve energies no more than one percent the mechanical energy of bubble collapse. We conclude that the applied field must influence the system though its effect on some parameter which the bubble motion depends upon very sensitively. A few such mechanisms are suggested.

DiDonna, B. A.; Witten, T. A.; Young, J. B.

1998-09-01

313

Warm inflation in presence of magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

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.

Piccinelli, Gabriella [Centro Tecnológico, FES Aragón, Universidad Nacional Autónoma de México, Avenida Rancho Seco S/N, Bosques de Aragón, Nezahualcóyotl, Estado de México 57130 (Mexico); Sánchez, Ángel [Department of Physics, University of Texas at El Paso, El Paso, Texas 79968 (United States); Ayala, Alejandro; Mizher, Ana Julia [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Apartado Postal 70-543, México Distrito Federal 04510 (Mexico)

2013-07-23

314

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

315

Bending of magnetic filaments under a magnetic field.  

Science.gov (United States)

Magnetic beads and superparamagnetic (SP) colloid particles have successfully been employed for micromechanical manipulation of soft material, in situ probing of elastic properties, and design of smart materials (ferrogels). Here we derive analytical expressions for the equilibrium shape of magnetic fibers, considering two end-member cases, (a) SP or single-domain particles concentrated at the free end of cantilevered rods or tubes, and (b) filaments consisting of SP particles, with this case being mathematically equivalent to tubes containing SP particles. Our analysis yields also metastable equilibrium states (MES's), which only exist above a critical filament length, but become more stable with increasing magnetic field. The MES's for case (a) are, like the ground state, circular arcs, but more strongly bent. The multiform MES's in case (b), which comprise hairpin, sinuous, or even closed shapes, have recently been observed in experiments, too. We also study the effect of gravity on the balance between bending and magnetic energy, which leads to curves with inflection point if the influence of gravity is stronger than that of the magnetic field. Because of their simple experimental realization, case (a) magnetic filaments are deemed highly suitable for micromechanical experiments on long chains of polymer molecules. Another potential application of cantilevered magnetic filaments with magnetic material attached to the free end is in scanning probe microscopes. Because the magnetic field due to the magnetic tip is comparatively weak, the magnetization structure of the sample to be investigated would not be affected by the probe. Thus, for the examination of magnetically soft materials, probes in the form of magnetic filaments may hold advantages over tips usually employed in magnetic force microscopy. PMID:15697393

Shcherbakov, Valera P; Winklhofer, Michael

2004-12-01

316

Measurements of the magnetic field of strong field permanent sextupole magnets  

International Nuclear Information System (INIS)

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

317

Casimir effect in external magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

In this paper we examine the Casimir effect for charged fields in presence of external magnetic field. We consider scalar field (connected with spinless particles) and the Dirac field (connected with 1/2-spin particles). In both cases we describe quantum field using the canonical formalism. We obtain vacuum energy by direct solving field equations and using the mode summation method. In order to compute the renormalized vacuum energy we use the Abel-Plana formula.

Ostrowski, Marcin

2005-01-01

318

Magnetic fields in noninvasive brain stimulation.  

Science.gov (United States)

The idea that magnetic fields could be used therapeutically arose 2000 years ago. These therapeutic possibilities were expanded after the discovery of electromagnetic induction by the Englishman Michael Faraday and the American Joseph Henry. In 1896, Arsène d'Arsonval reported his experience with noninvasive brain magnetic stimulation to the scientific French community. In the second half of the 20th century, changing magnetic fields emerged as a noninvasive tool to study the nervous system and to modulate neural function. In 1985, Barker, Jalinous, and Freeston presented transcranial magnetic stimulation, a relatively focal and painless technique. Transcranial magnetic stimulation has been proposed as a clinical neurophysiology tool and as a potential adjuvant treatment for psychiatric and neurologic conditions. This article aims to contextualize the progress of use of magnetic fields in the history of neuroscience and medical sciences, until 1985. PMID:23787954

Vidal-Dourado, Marcos; Conforto, Adriana Bastos; Caboclo, Luis Otávio Sales Ferreira; Scaff, Milberto; Guilhoto, Laura Maria de Figueiredo Ferreira; Yacubian, Elza Márcia Targas

2014-04-01

319

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

320

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

 
 
 
 
321

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

322

Magnetic phase control by an electric field.  

Science.gov (United States)

The quest for higher data density in information storage is motivating investigations into approaches for manipulating magnetization by means other than magnetic fields. This is evidenced by the recent boom in magnetoelectronics and 'spintronics', where phenomena such as carrier effects in magnetic semiconductors and high-correlation effects in colossal magnetoresistive compounds are studied for their device potential. The linear magnetoelectric effect-the induction of polarization by a magnetic field and of magnetization by an electric field-provides another route for linking magnetic and electric properties. It was recently discovered that composite materials and magnetic ferroelectrics exhibit magnetoelectric effects that exceed previously known effects by orders of magnitude, with the potential to trigger magnetic or electric phase transitions. Here we report a system whose magnetic phase can be controlled by an external electric field: ferromagnetic ordering in hexagonal HoMnO3 is reversibly switched on and off by the applied field via magnetoelectric interactions. We monitor this process using magneto-optical techniques and reveal its microscopic origin by neutron and X-ray diffraction. From our results, we identify basic requirements for other candidate materials to exhibit magnetoelectric phase control. PMID:15282600

Lottermoser, Thomas; Lonkai, Thomas; Amann, Uwe; Hohlwein, Dietmar; Ihringer, Jörg; Fiebig, Manfred

2004-07-29

323

Faraday's Magnetic Field Induction Experiment  

Science.gov (United States)

This java simulation illustrates magnetic induction in a wire coil. The user can move a magnet in and out along the axis of a coil while a galvanometer shows the current induced in the coil. The deflection depends on the speed at which the coil moves.

Davidson, Michael

2010-12-29

324

Polarization Evolution in Strong Magnetic Fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Extremely strong magnetic fields change the vacuum index of refraction. Although this polarization dependent effect is small for typical neutron stars, it is large enough to decouple the polarization states of photons traveling within the field. The photon states evolve adiabatically and follow the changing magnetic field direction. The combination of a rotating magnetosphere and a frequency dependent state decoupling predicts polarization phase lags between different wave b...

Heyl, Jeremy S.; Shaviv, Nir J.

1999-01-01

325

Emittance measurement in a magnetic field  

International Nuclear Information System (INIS)

Emittance can be measured by intercepting an electron beam on a range thick plate and then observing the expansion of beamlets transmitted through small holes. The hole size is selected to minimize space charge effects. In the presence of a magnetic field the beamlets have a spiral trajectory and the usual field free formulation must be modified. To interpret emittance in the presence of a magnetic field an envelope equation is derived in the appropriate rotating frame. 1 ref

326

High magnetic field ?SR instrument scientific case  

International Nuclear Information System (INIS)

c field -4 Tesla), the energy associated with them is still modest in view of the thermal energy. Hence, the Zeeman energy splitting of a free electron in a magnetic field of 1 Tesla corresponds to a thermal energy as low as 0.67 Kelvin. It is worth mentioning that nowadays magnetic fields of the order of 10 to 15 Tesla are quite common in condensed matter laboratories and have opened up vast new exciting experimental possibilities. (author)

327

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

328

Magnetic field evolution in neutron stars  

CERN Document Server

Neutron stars contain persistent, ordered magnetic fields that are the strongest known in the Universe. However, their magnetic fluxes are similar to those in magnetic A and B stars and white dwarfs, suggesting that flux conservation during gravitational collapse may play an important role in establishing the field, although it might also be modified substantially by early convection, differential rotation, and magnetic instabilities. The equilibrium field configuration, established within hours (at most) of the formation of the star, is likely to be roughly axisymmetric, involving both poloidal and toroidal components. The stable stratification of the neutron star matter (due to its radial composition gradient) probably plays a crucial role in holding this magnetic structure inside the star. The field can evolve on long time scales by processes that overcome the stable stratification, such as weak interactions changing the relative abundances and ambipolar diffusion of charged particles with respect to neutr...

Reisenegger, Andreas

2007-01-01

329

Regulation of fields excited by permanent magnets  

International Nuclear Information System (INIS)

Two methods of fast regulation of fields excited by permanent magnets in salient-pole electron-optical lenses are described: 1)the hybrid method realized using the additional electromagnet introduced to a magnetic chain sequentially its field being composed or substracted with magnetosolid exciter field; 2)the method with saturation of a part of a magnetic circuit, with saturation being achievable at the begining or in the end of a regulation cycle. In the second method it is proposed to direct orthogonally the main flux excited by permanent magnets and the flux in the saturated part of the magnetic circuit excited using an electromagnet. It is shown that the second method allows one to reduce the required ampere-coils by more than an order as compared to the first method at one and the same regulation range and other equal conditions. The frequency of field regulation in the experimental mock-up was 10 kHz. 3 refs.; 2 figs

330

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

331

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

332

Helicity of the solar magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 t...

Tiwari, Sanjiv Kumar

2010-01-01

333

Neutron Star Crust in Strong Magnetic Fields  

Science.gov (United States)

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.

Nandi, Rana; Bandyopadhyay, Debades

2011-09-01

334

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

335

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

336

Strongly interacting matter in magnetic fields  

Energy Technology Data Exchange (ETDEWEB)

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

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

2013-08-01

337

Double and triple octupole excitations in the A?150 region  

International Nuclear Information System (INIS)

The results of recent experiments performed at L.N.L. on multiple octupole excitations in the N=84 isotones are reviewed. In particular, the results on B(E3) strengths in 146Sm are discussed and expectations for higher-order octupole excitations are compared with the present experimental situation

338

Toroidal magnetic field simulation by special windings  

International Nuclear Information System (INIS)

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

339

Asymmetric Diffusion of Magnetic Field Lines  

CERN Document Server

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, the difference between forward and backward diffusion is not directly due to imbalance, but a non-trivial consequence of both imbalance and non-reversibility of turbulence. The asymmetric diffusion perpendicular to the mean magnetic field entails a variety of new physical phenomena, such as the production of parallel particle streaming in the presence of perpendicular particle gradients. Such streaming and associated instabilities could be significant for particle transport in laboratory, space and astrophysical plasmas.

Beresnyak, Andrey

2013-01-01

340

Design of integral magnetic field sensor  

International Nuclear Information System (INIS)

Magnetic field is one of the important physical parameters in the measuring process of pulsed EMP. We researched on anti-interference and high-sensitivity measurement technique of magnetic field in this report. Semi rigid cables were to bent into ringed antenna so that the antenna was shielded from electric-field interference and had little inductance; In order to have high sensitivity, operational transconductance amplifier was used to produce an active integrator; We designed an optical-electronic transferring module to upgrade anti-interference capability of the magnetic-field measurement system. A measurement system of magnetic field was accomplished. The measurement system was composed of antenna, integrator, and optical-electric transferring module and so on. We calibrated the measurement system in coaxial TEM cell. It indicates that, the measurement system's respondence of rise time is up to 2.5 ns, and output width at 90%-maximum of the pulse is wider than 200 ns. (authors)

 
 
 
 
341

Magnetic Field Induced Transition in Vanadium Spinels  

Science.gov (United States)

We study vanadium spinels AV2O4(A =Cd,Mg) in pulsed magnetic fields up to 65 T. A jump in magnetization at ?0H?40 T is observed in the single-crystal MgV2O4, indicating a field induced quantum phase transition between two distinct magnetic orders. In the multiferroic CdV2O4, the field induced transition is accompanied by a suppression of the electric polarization. By modeling the magnetic properties in the presence of strong spin-orbit coupling characteristic of vanadium spinels, we show that both features of the field induced transition can be successfully explained by including the effects of the local trigonal crystal field.

Mun, E. D.; Chern, Gia-Wei; Pardo, V.; Rivadulla, F.; Sinclair, R.; Zhou, H. D.; Zapf, V. S.; Batista, C. D.

2014-01-01

342

Black hole in an external magnetic field  

International Nuclear Information System (INIS)

The motion and scalar radiation emitted by particles moving near a spherically symmetric black hole immersed in an external asymptotically homogeneous stationary magnetic field is considered. It is shown that the magnetic field produces a potential barrier which prevents the escape of both charged and neutral particles at infinity in a plane orthogonal to the magnetic field. An exception are massless particles for which the projection of the angular momentum on the magnetic field is zero. Stable circular orbits for charged particles exist which correspond to an almost 100% mass defect; stable ultrarelativistic trajectories also exist. The intensity of the scalar radiation emitted by an ultrarelativistic particle moving along a stable orbit is ?2 times greater than that of the radiation emitted by a particle moving along an unstable geodesic in the Schwarzschild field, ? being the ratio of energy to mass

343

Magnetic field induced transition in vanadium spinels.  

Science.gov (United States)

We study vanadium spinels AV2O4 (A = Cd,Mg) in pulsed magnetic fields up to 65 T. A jump in magnetization at ?0H?40??T is observed in the single-crystal MgV2O4, indicating a field induced quantum phase transition between two distinct magnetic orders. In the multiferroic CdV2O4, the field induced transition is accompanied by a suppression of the electric polarization. By modeling the magnetic properties in the presence of strong spin-orbit coupling characteristic of vanadium spinels, we show that both features of the field induced transition can be successfully explained by including the effects of the local trigonal crystal field. PMID:24483929

Mun, E D; Chern, Gia-Wei; Pardo, V; Rivadulla, F; Sinclair, R; Zhou, H D; Zapf, V S; Batista, C D

2014-01-10

344

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

345

Nonfrustrated magnetoelectric with incommensurate magnetic order in magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We discuss a model nonfrustrated magnetoelectric in which strong enough magnetoelectric coupling produces incommensurate magnetic order leading to ferroelectricity. Properties of the magnetoelectric in magnetic field directed perpendicular to wave vector describing the spin helix are considered in detail. Analysis of classical energy shows that in contrast to naive expectation the onset of ferroelectricity takes place at a field $H_{c1}$ that is lower than the saturation fie...

Syromyatnikov, A. V.

2007-01-01

346

Octupole Correlations and Deformation In Ba, La and Pr  

International Nuclear Information System (INIS)

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

347

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

348

Discovery of magnetic fields in hot subdwarfs  

CERN Document Server

We present polarisation measurements of sdB and sdO stars using FORS1 on the VLT. The observations were made as part of a project to determine whether magnetic fields in two super-metal-rich stars can explain their extreme abundance peculiarities. Field strengths of up to ~1.5 kG have been measured at varying levels of significance in each of our six targets, however no clear evidence was found between apparently normal subdwarfs and the metal-rich objects. The origin of the magnetic fields is unknown. We also discuss the implications of our measurements for magnetic flux conservation in late stages of stellar evolution.

O'Toole, S J; Heber, U; Jordan, S

2005-01-01

349

Hyperon Stars in Strong Magnetic Fields  

CERN Document Server

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

Gomes, R O; Vasconcellos, C A Z

2013-01-01

350

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

351

Magnetic field dependent tunneling in glasses  

Science.gov (United States)

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 lifting of the dielectric saturation by weak magnetic fields and oscillations of the dielectric response in the low temperature resonant regime. As the 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. PMID:11017665

Strehlow; Wohlfahrt; Jansen; Haueisen; Weiss; Enss; Hunklinger

2000-02-28

352

Magnetic field quality analysis using ANSYS  

Energy Technology Data Exchange (ETDEWEB)

The design of superconducting magnets for particles accelerators requires a high quality of the magnetic field. This paper presents an ANSYS 4.4A Post 1 macro that computes the field quality performing a Fourier analysis of the magnetic field. The results show that the ANSYS solution converges toward the analytical solution and that the error on the multipole coefficients depends linearly on the square of the mesh size. This shows the good accuracy of ANSYS in computing the multipole coefficients. 2 refs., 16 figs., 4 tabs.

Dell' Orco, D.; Chen, Y.

1991-03-01

353

Graphene Nanoribbon in Sharply Localized Magnetic Fields  

CERN Document Server

We study the effect of a sharply localized magnetic field on the mobility of electrons in a strip (ribbon) of graphene sheet. The magnetic field is taken as a single and double delta type localized functions, which are the zero width limit of gaussian fields considered at a later stage. For both field configurations, we investigate the scattering behavior of electrons and evaluate analytically and numerically their transmission and reflection coefficients. The possibility of spacial confinement due to the inhomogeneous field configuration is also investigated.

Alhaidari, Abdulaziz D; Mouhafid, Abderrahim El; Jellal, Ahmed

2011-01-01

354

Working in the magnetic field of ultrahigh field MRI  

International Nuclear Information System (INIS)

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

355

Magnetic field considerations in fusion power plant environs  

Energy Technology Data Exchange (ETDEWEB)

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.

Liemohn, H.B.; Lessor, D.L.; Duane, B.H.

1976-09-01

356

Solar magnetic fields and convection. VII  

International Nuclear Information System (INIS)

The primordial field theory of solar magnetic fields whose three main features are, first, a permanent dipole-like magnetic field, second a mainly toroidal field formed by shearing and rolling into individual, helically twisted ropes as suggested by Babcock, and third a mechanism for reversing the toroidal field is reviewed. The theory explains numerous observational effects where the dynamo theory fails. (i) An active region forms when a rope section emerges and expands layer by layer to form a rotating arch filament system and then spots. Only a rope model explains the radial inflow of magnetic elements to build up a spot, as well as the spiral structure and other features pointed out by Babcock. (ii) The model explains umbral and penumbral structures, the Wilson depression, Evershed flow, the sunspot energy deficit and the very slow loss of flux fragments by some sunspots. (iii) The model is then extended to background magnetic fields to show that surface mangetic fields are like the uppermost branches of a magnetic 'tree' whose trunk is a flux rope. This explains unipolar magnetic regions, 'pepper and salt', and ephemeral active regions. Tension in the submerged flux submerged flux ropes accounts for the observed migrations of magnetic regions, active longitudes and magnetic longitudes. (iv) On a smaller scale spicules, mottles and other network elements are explained in terms of the tree structure. (v) the mechanism of reversal of the toroidal field system is expversal of the toroidal field system is explained and the manner of disposal of old toroidal fields. (vi) The basic error in the dynamo theory is discussed briefly. (Auth.)

357

Magnetic field measurements on ISABELLE storage ring magnets  

Energy Technology Data Exchange (ETDEWEB)

In 1978 the magnetic field shapes of six ISABELLE prototype dipole magnets were measured in detail. All the harmonic terms that are forbidden by symmetry in dipole magnets are found to have values that are zero to within the allowed tolerances. This result indicates that the random errors in conductor placement are within tolerances and that the assembly techniques are satisfactory in this regard. However, the first allowed error term in a dipole magnet, the sextupole term, is much too large, and varies greatly from magnet to magnet resulting in field errors at the edge of the desired good field region that are 10/sup -3/ of the central field value, whereas the tolerable field errors are of the order of 10/sup -4/ of the central field value. This large sextupole term has been traced to assembly errors which yield a coil assembly which instead of being circular in cross section is racetrack shaped, with the vertical axis being 10 to 20 thousandths of an inch greater than the horizontal axis. This problem will be corrected in the future production series.

Bleser, E.; Dahl, P.; Gardner, D.; Kaugerts, J.; McInturff, A.; Robins, K.; Sampson, W.; Schewe, P.

1979-01-01

358

Some Structural Properties of Solar Magnetic Fields  

Science.gov (United States)

We discuss some results of the study of spatial characteristics of solar magnetic fields. The analysis is based on the magnetic field data obtained with a new spectromagnetograph installed on the IZMIRAN Tower Telescope (Fe I 6302.5 Å) (Kozhevatov et al., 2002), the data of the MSFC solar vector magnetograph (Fe I 5250.2 Å) and the data of longitudinal magnetic 96 m daily maps of SOHO/MDI magnetograph (Ni I 6768 Å) downloaded through Internet. Our study was directed in some different ways: the fractal properties of sunspots; fractal properties of space distribution of the magnetic fields along great distances comparable with the size of active regions or active complexes; fractal properties of active and quiet regions as global entities. To do it we used some different methods, particularly, the well known method using the relation between the area and the perimeter of magnetic field lines (see (Feder, 1988; Meunier, 1999; Nesme-Ribes at al., 1996; Balke et al., 1993)) and technique developed by Higuchi (1988), who applied it to the investigation of long time series. Note also that magnetic structure in terms of the fractal models was developed earlier in (Zelenyi & Milovanov, 1991; Milovanov & Zelenyi, 1993; Mogilevskii, 1994; Mogilevskii, 2001; Abramenko et al., 2002; Abramenko, 2005; Salakhudinova & Golovko, 2005). The main results are: 1. Fractal analysis of sunspot magnetic field indicated the existence of three families of self-similar contour lines roughly belonging to the umbra, penumbra and the ambient photosphere correspondingly. The greatest fractal dimension corresponds to the regions of weakest fields (ambient photosphere), the least one corresponds to the intermediate region (penumbra). 2. More detailed analysis shows that the fractal coefficient has a maximum (about 1.50) near the umbra--penumbra interface. 3. The global fractal numbers of space distribution of magnetic field on solar surface is closely connected with the mean absolute values of the longitudinal magnetic field for this surface. The fractal numbers diminish with the rising of mean magnetic field (from values about 2.0 for the relatively quiet region to 1- 1.2 for very active regions). 4. The dependences of fractal numbers of the space distribution of longitudinal and transversal fields versus mean longitudinal field are similar by their character but the fractal values for transversal field are higher than the corresponding factor values for longitudinal field by factor about 1.5. This means that the distribution of transversal field along the space is more chaotic than the distribution of longitudinal field.

Ioshpa, B.; Mogilevskii, E.; Obridko, V.

2007-05-01

359

The CMS Magnetic Field Map Performance  

CERN Document Server

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

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

2010-01-01

360

Discovery of a magnetic field on Vega  

CERN Document Server

We report the detection of a magnetic field on Vega through spectropolarimetric observations. We acquired 257 Stokes V high signal-to-noise and high-resolution echelle spectra during four consecutive nights with NARVAL spectropolarimeter at the 2-m Telescope Bernard Lyot of Observatoire du Pic du Midi (France). A circularly polarized signal in line profiles is detected after gathering the contribution of about 1200 spectral lines for each spectrum and summing up the signal over the 257 spectra. Interpreting this polarization as a Zeeman signature leads to a value of $-0.6 \\pm 0.3$ G for the disk-averaged line-of-sight component of the surface magnetic field. This is the first time a magnetic field is unambiguously detected in an A-type star which is not an Ap chemically peculiar star. Moreover, the Vega longitudinal magnetic field is smaller by about two orders of magnitude than the longitudinal magnetic field (taken at its maximum phase) of the most weakly magnetic Ap stars. Magnetic fields similar to the Ve...

Lignières, F; Böhm, T; Aurière, M

2009-01-01

 
 
 
 
361

Gravimetric Measurement of Magnetic Field Gradient Spatial Distribution  

Digital Repository Infrastructure Vision for European Research (DRIVER)

Magnetic interaction between a weighing sample and an external magnetic field allows to measure characteristics of magnetic field (a sample with known magnetic characteristics), as well as the magnetic properties of a sample (a known magnetic field). Measurement of materials magnetic permeability is a well known application of this method. In this paper we restrict ourselves to the measurement of magnetic field spatial distribution, which was achieved by scanning of samples ...

Arutunian, S. G.; Dobrovolski, N. M.; Egiazarian, S. L.; Mailian, M. R.; Sinenko, I. G.; Sinjavski, A. V.; Vasiniuk, I. E.

1999-01-01

362

The rotation-magnetic field relation  

CERN Document Server

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

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

2008-01-01

363

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

364

Review: Magnetic fields of O stars  

CERN Document Server

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

Wade, G A

2014-01-01

365

Relativistic magnetic gyroscope wheel in electromagnetic fields  

International Nuclear Information System (INIS)

Consideration is given to the precession of a relativistic magnetic gyroscope wheel (GW) which when rotating moves forward in electromagnetic field. It is guessed that orientation of its own mechanical moment (spin) and that of the gyroscope wheel's magnetic moment coincides. Elegant formulation of the classical spin equations and of the criterion of magnetic GW free motion is presented. General solutions of the equations of spin precession are derived

366

Magnetic field gradient effects on Rayleigh-Taylor instability with continuous magnetic field and density profiles  

Energy Technology Data Exchange (ETDEWEB)

In this paper, the effects of magnetic field gradient (i.e., the magnetic field transition layer effects) on the Rayleigh-Taylor instability (RTI) with continuous magnetic field and density profiles are investigated analytically. The transition layers of magnetic field and density with two different typical profiles are studied and the analytic expressions of the linear growth rate of the RTI are obtained. It is found that the magnetic field effects strongly reduce the linear growth rate of the RTI, especially when the perturbation wavelength is short. The linear growth rate of the RTI increases with the thickness of the magnetic field transition layer, especially for the case of small thickness of the magnetic field transition layer. When the magnetic field transition layer width is long enough, the linear growth rate of the RTI can be saturated. Thus when one increases the width of the magnetic field transition layer, the linear growth rate of the RTI increases only in a certain range, which depends on the magnetic field strength. The numerical results are compared with the analytic linear growth rates and they agree well with each other.

Yang, B. L. [Graduate School, China Academy of Engineering Physics, Beijing 100088 (China); Wang, L. F.; Ye, W. H. [HEDPS and CAPT, Peking University, Beijing 100871 (China); LCP, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Xue, C. [LCP, Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

2011-07-15

367

Magnetic field gradient effects on Rayleigh-Taylor instability with continuous magnetic field and density profiles  

International Nuclear Information System (INIS)

In this paper, the effects of magnetic field gradient (i.e., the magnetic field transition layer effects) on the Rayleigh-Taylor instability (RTI) with continuous magnetic field and density profiles are investigated analytically. The transition layers of magnetic field and density with two different typical profiles are studied and the analytic expressions of the linear growth rate of the RTI are obtained. It is found that the magnetic field effects strongly reduce the linear growth rate of the RTI, especially when the perturbation wavelength is short. The linear growth rate of the RTI increases with the thickness of the magnetic field transition layer, especially for the case of small thickness of the magnetic field transition layer. When the magnetic field transition layer width is long enough, the linear growth rate of the RTI can be saturated. Thus when one increases the width of the magnetic field transition layer, the linear growth rate of the RTI increases only in a certain range, which depends on the magnetic field strength. The numerical results are compared with the analytic linear growth rates and they agree well with each other.

368

Magnetic fields of HgMn stars  

DEFF Research Database (Denmark)

Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have failed to detect magnetic fields, indicating an upper limit on the longitudinal field between 8 and 15G. In these LSD studies, assumptions were made that all spectral lines are identical in shape and can be described by a scaled mean profile. Aims. We re-analyse the available spectropolarimetric material by applying the moment technique on spectral lines of inhomogeneously distributed elements separately. Furthermore, we present new determinations of the mean longitudinal magnetic field for the HgMn star HD 65949 and the hotter analog of HgMn stars, the PGa star HD 19400, using FORS 2 installed at the VLT. We also give new measurements of the eclipsing system ARAur with a primary star of HgMn peculiarity, which were obtained with the SOFIN spectropolarimeter installed at the Nordic Optical Telescope. Methods. We downloaded from the European Southern Observatory (ESO) archive the publically available HARPS spectra for eight HgMn stars and one normal and one superficially normal B-type star obtained in 2010. Out of this sample, three HgMn stars belong to spectroscopic double-lined systems. The application of the moment technique to the HARPS and SOFIN spectra allowed us to study the presence of the longitudinal magnetic field, the crossover effect, and quadratic magnetic fields. Results for the HgMn star HD 65949 and the PGa star HD 19400 are based on a linear regression analysis of low-resolution spectra obtained with FORS 2 in spectropolarimetric mode. Results. Our measurements of the magnetic field with the moment technique using spectral lines of several elements separately reveal the presence of a weak longitudinal magnetic field, a quadratic magnetic field, and the crossover effect on the surface of several HgMn stars aswell as normal and superficially normal B-type stars. Furthermore, our analysis suggests the existence of intriguing correlations between the strength of the magnetic field, abundance anomalies, and binary properties. The results are discussed in the context of possible mechanisms responsible for the development of the element patches and complex magnetic fields on the surface of late B-type stars.

Hubrig, S.; Gonzalez, J. F.

2012-01-01

369

Influence of magnetic field on turbomolecular pumps  

International Nuclear Information System (INIS)

Because Magnetically suspended turbo-molecular pumps (TMPs) with dry backing pumps are very preferable to achieve and maintain UHV without oil contamination, recently they have been widely used in nuclear fusion devices and sometimes in particle accelerators. In order to use them in these fields some researches have been published into the influence of the magnetic fields on TMPs. However, these evaluations were carried out under some ambiguous magnetic fields and only about the special type of TMPs. Thus, we have intended to establish the standard for dealing with the influence of magnetic field on TMPs. First of all, the influence has been exactly investigated for two parts: one is due to the vertical magnetic field, and the other due to the parallel component. A solenoid of diameter 500 mm and length 1500 mm has been newly constructed to examine the TMPs in the uniform magnetic fields. This solenoid has 1493 turns per m, therefore, letting a current of about 9.0A flow leads to generate the axial magnetic field of 100 gauss in the central region. The axial magnetic field is uniform with the deviation less than 0.5% in the cylindrical region of 400 mm in a diameter and 280 mm long at the center. The radial component is only about 0.5% of the axial one. We have studied the influence of the magnetic field on the TMPs of Osaka vacuum Products Co., Ltd. This TMP has not only the magnetic suspension bearing but the spirally grooved rotor, which endures such high backing pd rotor, which endures such high backing pressures as 500 Pa. The TMP is set on the table made of Al and the direction to the axis of solenoid was adjusted by the support attached to the table. We have measured the rotating speed, power for driving the rotor, and the rotor temperature as a function of the magnetic fields. In the field vertical to the rotating axis, both the rotor temperature and the driving power clearly increased even at 10 Gauss. On the other hand, they had no changes at 100 Gauss in a parallel field. In this paper the experimental results are shown in detail. (author)

370

Prediction of the interplanetary magnetic field strength  

Science.gov (United States)

A new model of the coronal and interplanetary magnetic field can predict both the interplanetary magnetic field strength and its polarity from measurements of the photospheric magnetic field. The model includes the effects of the large-scale horizontal electric currents flowing in the inner corona, of the warped heliospheric current sheet in the upper corona, and of volume currents flowing in the region where the solar wind plasma totally controls the magnetic field. The model matches the MHD solution for a simple dipole test case better than earlier source surface and current sheet models. The strength and polarity of the radial interplanetary magnetic field component predicted for quiet time samples in each year from 1977 to 1986 agree with observations made near the Earth's orbit better than the hybrid MHD-source surface model (Wang and Sheeley, 1988). The results raise the question of whether coronal holes are the only solar source of the interplantary magnetic field in the solar wind. If some interplanetary flux originates outside coronal holes, the model can match the observed field using the accepted 1.8 saturation correction factor for lambda 5250 A magnetograph observations. Requiring open flux to come exclusively from coronal holes requires and additional factor of two.

Zhao, Xuepu; Hoeksema, J. Todd

1995-01-01

371

Evolution of Magnetic Fields in Supernova Remnants  

CERN Document Server

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

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

2008-01-01

372

Cosmic Magnetic Fields and the CMB  

CERN Document Server

I describe the imprint of primordial magnetic fields on the CMB. I show that these are observable only if the field amplitude is of the order of $B\\gsim 10^{-9}G$ on Mpc scale. I further argue that such fields are strongly constrained by the stochastic background of gravity waves which they produce. Primordial magnetic fields, which are strong enough to be seen in the CMB, are compatible with the nucleosynthesis bound, only if their spectrum is close to scale invariant, or maybe if helical magnetic fields provoke an inverse cascade. For helical fields, the CMB signature is especially interesting. It contains parity violating T-B and E--B correlations.

Durrer, R

2006-01-01

373

Magnetic fields in laser heated plasmas  

International Nuclear Information System (INIS)

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

374

Vlasov equation in the stochastic magnetic field  

International Nuclear Information System (INIS)

We investigate the Vlasov equation in the stochastic magnetic field as a stochastic Li ouville equation and derive the equation for the ensemble-averaged distribution function. The term resulting from the stochastic magnetic field has the derivatives with respect to both the velocity and the real space coordinates, which is a contrast to both the real space diffusion as seen in the guiding center picture and the velocity space diffusion as in the quasi-linear theory of the Vlasov equation including the electric field fluctuations. We find that this term retains the mass and energy conservation properties of the original Lorentz force due to the stochastic magnetic field and yields the additional force in the momentum equation. This additional force produced by the stochastic field gives the drift velocity which corresponds to the familiar real space diffusion of the guiding center in the stochastic field. The finite Larmor radius effect on the diffusion is also estimated. (author)

375

Toroidal Plasma Containment with Rotating Magnetic Field.  

Science.gov (United States)

Experimental investigations were conducted on a toroidal plasma with alternating pinch- and theta-pinch magnetic fields as well as with a theta-pinch and with a screw pinch. For the alternating pinch, the resultant magnetic vector is rotating, so that the...

D. E. Brown, H. G. Loos

1966-01-01

376

Parameterization of the LHCb Magnetic Field Map  

International Nuclear Information System (INIS)

A parameterization of the LHCb magnetic field is presented. It is derived from an analysis of data from a high-precision survey in and around the 4 Tm dipole magnet. By optimally using both data measurements and simulation values, a precision of less than 10-3 Tesla is achieved for the two polarities.

377

Magnetic monopoles and the survival of galactic magnetic fields  

International Nuclear Information System (INIS)

The most stringent, mass-independent limit on the flux of magnetic monopoles is based upon the survival of the galactic magnetic fields, the so-called ''Parker limit'': F-16 cm-2sr-1sec-1. We reexamine this limit, taking into account the monopole's mass and velocity distribution, and the observed structure of the galactic magnetic field. We derive flux limits which depend upon the monopole's mass and velocity, and the strength, coherence length, and regeneration time of the galactic magnetic field. The largest monopole flux consistent with both the survival of the galactic magnetic field and the bounds from the mass density contributed by monopoles is Fapprox. =10-12 cm-2sr-1sec-1, arising for monopoles of mass approx. =1019 GeV with velocity approx. =3 x 10-3c which cluster with the Galaxy. An observed flux greater than this would have profound implications for our understanding of the galactic magnetic field, and we briefly explore some exotic possibilities. Of course, this bound is not applicable to a local source (e.g., the Sun, atmospheric cosmic-ray production, etc.)

378

Conformal anomaly and primordial magnetic fields  

CERN Document Server

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

Agullo, Ivan

2013-01-01

379

The Magnetic Field of Helmholtz Coils  

Science.gov (United States)

Describes the magnetic field of Helmholtz coils qualitatively and then provides the basis for a quantitative expression. Since the mathematical calculations are very involved, a computer program for solving the mathematical expression is presented and explained. (GS)

Berridge, H. J. J.

1975-01-01

380

Fractal structure of the interplanetary magnetic field  

International Nuclear Information System (INIS)

Under some conditions, time series of the interplanetary magnetic field strength and components have the properties of fractal curves. Magnetic field measurements made near 8.5 AU by Voyager 2 from June 5 to August 24, 1981 were self-similar over time scales from approximately 20 sec to approximately 3 x 100,000 sec, and the fractal dimension of the time series of the strength and components of the magnetic field was D = 5/3, corresponding to a power spectrum P(f) approximately f sup -5/3. Since the Kolmogorov spectrum for homogeneous, isotropic, stationary turbulence is also f sup -5/3, the Voyager 2 measurements are consistent with the observation of an inertial range of turbulence extending over approximately four decades in frequency. Interaction regions probably contributed most of the power in this interval. As an example, one interaction region is discussed in which the magnetic field had a fractal dimension D = 5/3

 
 
 
 
381

A Topology for the Penumbral Magnetic Fields  

CERN Document Server

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

Almeida, J Sanchez

2009-01-01

382

Magnetic field diagnostic from translational Stark effect  

International Nuclear Information System (INIS)

A method of magnetic field determination using translational Stark effect and Zeeman effect is outlined. An approximation, valid for relatively high probe atom velocities is developed in detail and its applicability is put in evidence. (author). 3 refs

383

Faraday's Law Problem: Describing Magnetic Fields  

Science.gov (United States)

A loop of wire travels from the right to the left through an inhomogeneous magnetic field. (The green line is at x=0 is for your reference.) The induced emf in the loop is shown in Volts in the animation.

Christian, Wolfgang; Belloni, Mario

2007-03-03

384

End fields of CBA superconducting magnets  

International Nuclear Information System (INIS)

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

385

Orientation effects in pulsed magnetic field treatment  

International Nuclear Information System (INIS)

This paper presents the orientation effects on residual stress release by pulsed magnetic field treatment. Specimens are produced by tungsten inert gas (TIG) welding and the initial residual stresses in them are measured by the hole-drilling method. With different orientations these specimens are treated in the same magnetic field and the residual stresses are measured for the second time. By comparing the stress values before and after treatment it is obvious that magnetic field treatment effects are related to orientations. Based on a referred ferromagnetics formula, a supposition is proposed and a further survey of the magnetostriction constant is carried out. All experimental results support the proposed model and a prescription is given for pulsed magnetic field treatments

386

Orientation effects in pulsed magnetic field treatment  

Energy Technology Data Exchange (ETDEWEB)

This paper presents the orientation effects on residual stress release by pulsed magnetic field treatment. Specimens are produced by tungsten inert gas (TIG) welding and the initial residual stresses in them are measured by the hole-drilling method. With different orientations these specimens are treated in the same magnetic field and the residual stresses are measured for the second time. By comparing the stress values before and after treatment it is obvious that magnetic field treatment effects are related to orientations. Based on a referred ferromagnetics formula, a supposition is proposed and a further survey of the magnetostriction constant is carried out. All experimental results support the proposed model and a prescription is given for pulsed magnetic field treatments.

Cai Zhipeng [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)]. E-mail: czpdme@tsinghua.edu.cn; Lin Jian [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Zhao Haiyan [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Lu Anli [Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China)

2005-05-25

387

Magnetic Field Amplification in Young Galaxies  

CERN Document Server

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

Schober, Jennifer; Klessen, Ralf S

2013-01-01

388

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

Science.gov (United States)

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

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

1999-01-01

389

Laminated magnet field coil sheath  

Science.gov (United States)

A method for manufacturing a magnetic cable trim coil in a sheath assembly for use in a cryogenic particle accelerator. A precisely positioned pattern of trim coil turns is bonded to a flexible substrate sheath that is capable of withstanding cryogenic operating conditions. In the method of the invention the flexible substrate sheath, with the trim coil pattern precisely location relative to a bore tube assembly of an accelerator and is then bonded to the bore tube with a tape suitable for cryogenic application. The resultant assembly can be readily handled and installed within an iron magnet yoke assembly of a suitable cryogenic particle accelerator. 1 fig.

Skaritka, J.R.

1987-05-15

390

Magnetic field effect in hybrid nanostructures  

Digital Repository Infrastructure Vision for European Research (DRIVER)

We examine the effect of the magnetic field on the proximity effect in nanostructures, self consistently using the Bogoliubov-deGennes formalism within the two dimensional extended Hubbard model. We calculate the local density of states and the pair amplitude. We study several nanostructures: superconductor - two dimensional electron gas, superconductor - ferromagnet. In these structures the magnetic field can be considered as a modulation parameter for the proximity effect.

Stefanakis, N.

2003-01-01

391

Charmonia and Bottomonia in a Magnetic Field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

392

Magnetic fields of HgMn stars  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. We re-analyse available spectropolarimetric material by applying the moment technique on spectral lines of inhomogeneously distributed elements separately. Furthermore, we present new determinations of the mean longitudinal magnetic field for the HgMn star HD65949 and the hotter analog of HgMn stars...

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

2012-01-01

393

Polarization tensors in a strong magnetic field  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The vacuum polarization tensor in strong external magnetic fields has been evaluated numerically for various strengths of magnetic fields and momenta of photons under the threshold of the $e^{\\pm}$ pair creation. The fitting formula has been obtained which reproduces the calculated results within 10 % of error. The proper time method is employed further to obtain the retarded polarization tensor for finite temperature plasmas.

Kohri, K.; Yamada, Shoichi

2001-01-01

394

Hyperon bulk viscosity in strong magnetic fields  

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

395

Explosion of soliton in a magnetic field  

International Nuclear Information System (INIS)

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

396

Magnetic field corrections to solar oscillation frequencies  

International Nuclear Information System (INIS)

Investigations of solar oscillations have revealed a slight but systematic decrease in frequencies of low-degree p-modes from 1980 to 1984. The authors attribute this decrease to a magnetic field within the solar interior evolving over the solar cycle. It is estimated that magnetic field strengths at the base of the convection zone of at least 5 x 105 G are required to produce the observed frequency decrease. (U.K.)

397

Planetary Magnetic Fields and Climate Evolution  

Science.gov (United States)

We explore the possible connections between magnetic fields and climate at the terrestrial bodies Venus, Earth, Mars, and Titan. Magnetic fields are thought to have negligible effects on the processes that change a planet's climate, except for processes that alter the abundance of atmospheric gases. Particles can be added or removed at the top of an atmosphere, where collisions are infrequent and a more substantial fraction of particles are ionized (and therefore subject to magnetic forces) than at lower altitudes. The absence of a global magnetic field at Mars for much of its history may have contributed to the removal of a substantial fraction of its atmosphere to space. The persistence of a global magnetic field should have decreased both ionization and removal of atmospheric ions by several processes, and may have indirectly decreased the loss rate of neutral particles as well. While it is convenient to think of magnetic fields as shields for planetary atmospheres from impinging plasma (such as the solar wind), observations of ions escaping from Earth's polar cusp regions suggest that magnetic shielding effects may not be as effective as previously thought. One explanation that requires further testing is that magnetic fields transfer momentum and energy from incident plasma to localized regions of the atmosphere, resulting in similar (or possibly greater) escape rates than if the momentum and energy were imparted more globally to the atmosphere in the absence of a magnetic field. Trace gases can be important for climate despite their low relative abundance in planetary atmospheres. At Venus, removal of O+ over the history of the planet has likely contributed to the loss of water from the atmosphere, leading to a runaway greenhouse situation and having implications for the chemistry of atmosphere-surface interactions. Conversely, Titan's robust atmospheric chemistry may result from the addition of trace amounts of oxygen from Saturn's magnetosphere, which then participate in chemical reactions that produce carbon monoxide (CO) and carbon dioxide (CO2). Models of the entire atmosphere system (including planetary plasma interactions) should continue to shed light on the connections between magnetic fields and climate, as well as models that consider a single planetary body in both magnetized and unmagnetized states. Future measurements, such as those that will be made by the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft to Mars, will provide better constraints on the importance of magnetic fields in the evolution of atmospheres.

Brain, D. A.; Leblanc, F.; Luhmann, J. G.; Moore, T. E.; Tian, F.

398

Representation of magnetic fields in space  

International Nuclear Information System (INIS)

Several mathematical methods which are available for the description of magnetic fields in space are reviewed. Examples of the application of such methods are given, with particular emphasis on work related to the geomagnetic field, and their individual properties and associated problems are described. The methods are grouped in five main classes: methods based on the current density j, methods using the scalar magnetic potential ?, toroidal and poloidal components of the field and spherical vector harmonics, Euler potentials, and local expansions of the field near a given reference point. Special attenuation is devoted to models of the magnetosphere, to the uniqueness of ? as derived from observed data, and to the L parameter

399

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

400

Interaction of magnetic fields with liquid structures  

International Nuclear Information System (INIS)

A mechanism of the interaction of a magnetic field with liquid is suggested. The mechanism of the influence of electromagnetic fields (EMF) on biological processes can result in either the change of rates of biochemical reactions due to the change of water properties in EMF, or the change of configurations of biologically active molecules, or both of them. For the soliton model of bulk knitted structures in a magnetic field, the statistical integral and the configurational contributions to free energy, entropy, and specific heat were calculated. It is shown that the concentration of solitons depends on external fields

 
 
 
 
401

Untwisting magnetic fields in the solar corona  

Science.gov (United States)

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

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

2012-07-01

402

Power source device for poroidal magnetic field  

International Nuclear Information System (INIS)

Purpose: To eliminate external disturbances between power sources for poroidal magnetic fields and effectively prevent increase of the power source capacity. Constitution: Poroidal magnetic field power sources used for controlling the plasma cross sectional shape or controlling the plasma position involve a problem that external disturbances are applied for the poroidal magnetic field power sources with each other due to the induced voltage between plurality or poroidal magnetic field coils, or power source capacity is increased. The present invention dissolves this problem. That is, a plurality of circuits each comprising a poroidal magnetic field coil and a power source for supplying current thereto connected in series to each other are connected in parallel with each other. A common current return line is disposed to each of the circuits and a decoupling transformer is disposed to the circuit corresponding at least to a portion of the poroidal magnetic field coils for offsetting the mutual inductance between each of the coils. In this way, the induction voltage between the coils with each other can be offset by the decoupling through the transformer. (Kamimura, M.)

403

Magnetic Fields in Stellar Astrophysics  

CERN Document Server

This is a white paper submitted to the Stars and Stellar Evolution (SSE) Science Frontier Panel (SFP) of the NRC's 2010 Astronomy and Astrophysics Decadal Survey. The white paper is endorsed by the NSF Physics Frontier Center for Magnetic Self-Organization in Laboratory and Astrophysical Plasmas (CMSO).

Uzdensky, Dmitri; Ji, Hantao; Townsend, Richard; Yamada, Masaaki

2009-01-01

404

Octupole focusing in transport and acceleration systems  

International Nuclear Information System (INIS)

The radio-frequency quadrupole (RFQ) linac is capable of accelerating high-current, low-velocity ion beams. In accelerator systems comprising an RFQ and higher velocity accelerating structures, the current bottleneck still typically occurs within the RFQ. This limiting current is quite high in most cases, but linacs with even higher currents may be required in the future. We have begun a study of higher multipole systems to determine their capability for focusing and accelerating very high currents. We have chosen first to examine a radio-frequency octupole (RFO) transport system, and have developed a smooth-approximation analytical description that includes the conditions for input radial matching of a zero space-charge beam. Further, we have constructed a multiparticle beam-dynamics simulation program that accepts the low-current matched beam and gradually increases the beam current as it is transported. This results in a matched high-current beam, and the procedure can be used to determine the saturation-current limit of a periodic octupole system. As expected, at high currents the beam develops a hollow radial distribution that reduces the space-charge defocusing; initial results show that high currents can be transported. For acceleration, we have formulated the design parameters for a section of RFO linac, including the potential function, acceleration, and focusing efficiencies, and the geometry of the radially modulated pole tips

405

Octupole focusing in transport and accelerator systems  

International Nuclear Information System (INIS)

The radio-frequency quadrupole (RFQ) linac is capable of accelerating high-current, low-velocity ion beams. In accelerator systems comprising an RFQ and higher velocity accelerating structures, the current bottleneck still typically occurs within the RFQ. This limiting current is quite high in most cases, but linacs with even higher currents may be required in the future. We have begun a study of higher multipole systems to determine their capability or focusing and accelerating very high currents. We have chosen first to examine a radio-frequency octupole (RFQ) transport system, and have developed a smooth-approximation analytical description that includes the conditions for input radial matching of a zero space-charge beam. Further, we have constructed a multiparticle beam-dynamics simulation program that accepts the low-current matched beam and gradually increases the beam current as it is transported. This results in a matched high-current beam, and the procedure can be used to determine the saturation-current limit of a periodic octupole system. As expected, at high currents the beam develops a hollow radial distribution that reduces the space-charge defocusing; initial results show that high currents can be transported. For acceleration, we have formulated the design parameters for a section of RFQ linac, including the potential function, acceleration, and focusing efficiencies, and the geometry of the radially modulated

406

Persistence of octupole correlations in $^{231}/Ra$  

CERN Document Server

The structure of /sup 231/Ra, the heaviest odd Ra nucleus currently accessible for detailed spectroscopic investigation, has been studied in the beta /sup -/ decay of /sup 231/Fr. The main purpose has been to verify whether fast B(E1) rates and significant octupole correlations recently established in /sup 229/Ra persist in /sup 231 /Ra, The excited states in /sup 231/Ra have been determined for the first time. Spins and parities have been deduced from conversion electron measurements, while level half-lives in the ps and ns ranges have been measured with the Advanced Time Delayed beta gamma gamma (t) method. The moderately fast B(E1) rates found for transitions connecting the lowest-lying K/sup pi /=5/2/sup +or-/ and K/sup pi /=1 /2/sup +or-/ bands, reveal the persistence of octupole collective effects in /sup 231/Ra, although the B(E1) rates are lower than in /sup 229/Ra. These findings reinforce the differences in the B(E1) systematics between isotonic Ra and Th nuclei. (42 refs).

Fraile-Prieto, L M; Mach, H; Boutami, R; Aas, A J; Fogelberg, B; Gracía-Raffi, L M; Grant, I S; Gulda, K; Hagebø, E; Kurcewicz, W; Kvasil, J; López, M J; Løvhøiden, G; Martínez, T; Rubio, B; Taín, J L; Tengblad, O

2001-01-01

407

Students’ Difficulties in Understanding the Concepts of Magnetic Field Strength, Magnetic Flux Density and Magnetization  

Digital Repository Infrastructure Vision for European Research (DRIVER)

The concepts of magnetic field strength, magnetic flux density and magnetization are important fundamental conceptsin magnetism. However, these concepts are often confused by students due mostly to different notations andinterpretations. This confusion inhibits learning by students about magnetic properties of magnets and ofparamagnetic, ferromagnetic and diamagnetic materials. It is therefore very crucial to determine some students’difficulties on these specific concepts. Hence, we prepare...

Tanel, Zafer; Erol, Mustafa

2008-01-01

408

Magnetic reconnection in collisionless plasmas - Prescribed fields  

Science.gov (United States)

The structure of the dissipation region during magnetic reconnection in collisionless plasma is investigated by examining a prescribed two-dimensional magnetic x line configuration with an imposed inductive electric field E(y). The calculations represent an extension of recent MHD simulations of steady state reconnection (Biskamp, 1986; Lee and Fu, 1986) to the collisionless kinetic regime. It is shown that the structure of the x line reconnection configuration depends on only two parameters: a normalized inductive field and a parameter R which represents the opening angle of the magnetic x lines.

Burkhart, G. R.; Drake, J. F.; Chen, J.

1990-01-01

409

Magnetic Field Apparatus (MFA) Hardware Test  

Science.gov (United States)

The objectives of this study are threefold: (1) Provide insight into water delivery in microgravity and determine optimal germination paper wetting for subsequent seed germination in microgravity; (2) Observe the behavior of water exposed to a strong localized magnetic field in microgravity; and (3) Simulate the flow of fixative (using water) through the hardware. The Magnetic Field Apparatus (MFA) is a new piece of hardware slated to fly on the Space Shuttle in early 2001. MFA is designed to expose plant tissue to magnets in a microgravity environment, deliver water to the plant tissue, record photographic images of plant tissue, and deliver fixative to the plant tissue.

Anderson, Ken; Boody, April; Reed, Dave; Wang, Chung; Stuckey, Bob; Cox, Dave

1999-01-01

410

Instantons and Sphalerons in a Magnetic Field  

International Nuclear Information System (INIS)

I study the properties of the Euclidean Dirac equation for a light fermion in the presence of both a constant abelian magnetic field and an SU(2) instanton. In particular, I analyze the zero modes analytically in various limits, in order to compare with recent lattice QCD results, and study the implications for the electric dipole moment of the instanton induced by the magnetic field. I also present a holographic computation of the sphaleron rate of a strongly coupled plasma in a the presence of a constant magnetic flux and discuss its physical implications on heavy ion collisions

411

QCD quark condensate in external magnetic fields  

CERN Document Server

We present a comprehensive analysis of the light condensates in QCD with 1+1+1 sea quark flavors at zero and nonzero temperatures of up to 190 MeV and external magnetic fields B<1 GeV^2/e. We employ stout smeared staggered fermions with physical quark masses and extrapolate the results to the continuum limit. At low temperatures we confirm the magnetic catalysis scenario predicted by many model calculations while around the crossover the condensate develops a complex dependence on the external magnetic field, resulting in a decrease of the transition temperature.

Bali, G S; Endrodi, G; Fodor, Z; Katz, S D; Schafer, A

2012-01-01

412

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

413

The interplay between magnetic fields and convection  

Science.gov (United States)

The development of hydrodynamic dynamo theory is considered, taking into account investigations related to the solar cycle. Before constructing any detailed models of the solar cycle it is necessary to understand both the kinematic effect of convection on the magnetic field and the dynamical effect of the distorted field on the motion. The effect of a convective eddy on the magnetic field can be explored by studying an isolated sphere or cylinder rotating as a solid body in an otherwise uniform field. It is shown that reconnection of the lines of force leads to flux expulsion. A summary is provided of the relevant aspects of magnetoconvection, and a description is presented of some new results, obtained from numerical experiments at fairly high Rayleigh numbers. The computations illustrate the complexity of the nonlinear interaction between magnetic fields and convection.

Weiss, N. O.

1981-12-01

414

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

Energy Technology Data Exchange (ETDEWEB)

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 H{sub c2} 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 H{sub c2}. This negates the conventional thinking that superconductivity and magnetic fields are antagonistic.

Tessema, G.X.; Gamble, B.K.; Skove, M.J.; Lacerda, A.H.; Mielke, C.H.

1998-08-22

415

Fast Reconnection of Weak Magnetic Fields  

Science.gov (United States)

Fast magnetic reconnection refers to annihilation or topological rearrangement of magnetic fields on a timescale that is independent (or nearly independent) of the plasma resistivity. The resistivity of astrophysical plasmas is so low that reconnection is of little practical interest unless it is fast. Yet, the theory of fast magnetic reconnection is on uncertain ground, as models must avoid the tendency of magnetic fields to pile up at the reconnection layer, slowing down the flow. In this paper it is shown that these problems can be avoided to some extent if the flow is three dimensional. On the other hand, it is shown that in the limited but important case of incompressible stagnation point flows, every flow will amplify most magnetic fields. Although examples of fast magnetic reconnection abound, a weak, disordered magnetic field embedded in stagnation point flow will in general be amplified, and should eventually modify the flow. These results support recent arguments against the operation of turbulent resistivity in highly conducting fluids.

Zweibel, Ellen G.

1998-01-01

416

Charged Particles in Chaotic Magnetic Fields  

Science.gov (United States)

As new questions arise as of how particles travel through space, new methods of answering these questions can be implemented. By using chaotic streamlines in the Arnold-Beltrami-Childress (ABC) flows, particles can be set in motion at any point on an imaginary 2? x 2? x 2? cube. Trough computer codes written to track the different paths these particles can take, the paths can be observed. A chaotic magnetic field is recreated and introduced through a computer code as well as the magnetic field that has a determined start and end position. Histograms and Poincaré sections are created to record the information. The purpose of this experiment is to observe the charged particles on the chaotic magnetic field and on the constant magnetic field. Through tracking the distances the particle traveled during an allocated time the diffusion of particles in magnetic fields can be further understood, however, not completely. Furthermore these fields can widely occur in nature, in astrophysical environments, such as solar fares, solar corona, solar wind, and also in laboratory plasmas, thus, with further studies these fields can help understand them. Figure 1. Six principal vortexes Figure 2. Poincare Section of Vortexes

Vega Recalde, C. L.; Heerikhuisen, J.; Dasgupta, B.

2013-12-01

417

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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 norma...

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

2000-01-01

418

Magnetic Field Response Measurement Acquisition System  

Science.gov (United States)

Magnetic field response sensors designed as passive inductor- capacit or circuits produce magnetic field responses whose harmonic frequenci es correspond to states of physical properties for which the sensors measure. Power to the sensing element is acquired using Faraday induc tion. A radio frequency antenna produces the time varying magnetic fi eld used for powering the sensor, as well as receiving the magnetic field response of the sensor. An interrogation architecture for disce rning changes in sensor's response frequency, resistance and amplitud e is integral to the method thus enabling a variety of measurements. Multiple sensors can be interrogated using this method, thus eliminat ing the need to have a data acquisition channel dedicated to each se nsor. The method does not require the sensors to be in proximity to a ny form of acquisition hardware. A vast array of sensors can be used as interchangeable parts in an overall sensing system.

Woodward, Stanley E. (Inventor); Taylor, Bryant D. (Inventor)

2007-01-01

419

Magnetic marker based homogeneous bioassays utilizing rotating magnetic fields  

Science.gov (United States)

Magnetic nanoparticles (MNPs) as markers in bioassays utilizing rotating instead of alternating magnetic fields predict an improved sensitivity regarding quantitative protein detection. This finding is based on numerical solutions of the Fokker-Planck equation and pronounced for increasing field amplitudes. In order to verify this prediction, the phase lag change of MNPs in rotating magnetic fields up to 5 mT is measured. The magnetic markers are functionalized single core iron oxide nanoparticles with different sizes. Antibodies which specifically bind to the MNPs cause the phase lag change. The increase of the phase lag change strongly depends on the particle parameters. MNPs with a core diameter of 30 nm show for 5 mT, a significant difference between the two field types. This difference is less pronounced for the 25 nm MNPs due to the increasing influence of Néel relaxation processes and for the 40 nm particles, due to the reduced saturation magnetization. A further improvement for the 30 nm MNPs with field amplitudes over 5 mT is simulated based on the determined particle parameters.

Dieckhoff, Jan; Schilling, Meinhard; Ludwig, Frank

2014-05-01

420

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

Digital Repository Infrastructure Vision for European Research (DRIVER)

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

 
 
 
 
421

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

422

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.

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A deep dynamo generating Mercury's magnetic field.  

Science.gov (United States)

Mercury has a global magnetic field of internal origin and it is thought that a dynamo operating in the fluid part of Mercury's large iron core is the most probable cause. However, the low intensity of Mercury's magnetic field--about 1% the strength of the Earth's field--cannot be reconciled with an Earth-like dynamo. With the common assumption that Coriolis and Lorentz forces balance in planetary dynamos, a field thirty times stronger is expected. Here I present a numerical model of a dynamo driven by thermo-compositional convection associated with inner core solidification. The thermal gradient at the core-mantle boundary is subadiabatic, and hence the outer region of the liquid core is stably stratified with the dynamo operating only at depth, where a strong field is generated. Because of the planet's slow rotation the resulting magnetic field is dominated by small-scale components that fluctuate rapidly with time. The dynamo field diffuses through the stable conducting region, where rapidly varying parts are strongly attenuated by the skin effect, while the slowly varying dipole and quadrupole components pass to some degree. The model explains the observed structure and strength of Mercury's surface magnetic field and makes predictions that are testable with space missions both presently flying and planned. PMID:17183319

Christensen, Ulrich R

2006-12-21