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1

Magneto-optical sensing of magnetic field  

NASA Astrophysics Data System (ADS)

The non-reciprocity of magneto-optical reflection response by surface plasmon excitation in a planar glass/Fe/Au/air system with prism coupling is studied. We aim to find the optimal thicknesses of metallic layers with regard to the reflectance sensitivity to an external magnetic field. For this purpose, a corresponding response factor is introduced and applied. The numerically modeled prediction of sensitivity is verified by experimental measurements.

Vl?ek, Jaroslav; Les?ák, Michal; Pištora, Jaromír; Životský, Ond?ej

2013-01-01

2

Optical method for detecting variations of the magnetic field strength  

NASA Astrophysics Data System (ADS)

A method of detecting the magnetic field variation is proposed and implemented experimentally. The method employs the rotation of the speckle pattern of light transmitted through an optical fiber that is placed into a longitudinal magnetic field and the recording of a holographic grating in a photorefractive crystal using the speckle field. The possibility of detecting the shape of a 0.15-s magnetic field pulse is demonstrated experimentally.

Bolshakov, M. V.; Ershov, A. V.; Kundikova, N. D.

2011-04-01

3

Fiber Optic Magnetic Field Sensors Using Metallic Glass Coatings.  

NASA Astrophysics Data System (ADS)

In this thesis we have investigated the use of a magnetostrictive material with a single-mode optical fiber for detecting weak magnetic fields. The amorphous alloy Metglas^circler 2605SC (Fe_{81}B_ {13.5}Si_{3.5} C_2) was chosen as the magnetostrictive material because of the combination of its large magnetostriction and small magnetic anisotropy field among all available metals. For efficient coupling between the magnetostrictive material and the optical fiber, the magnetostrictive material was directly deposited onto the single-mode optical fiber. The coated fibers were used as the sensing element in the fiber optic magnetic field sensor (FOMS). Very high quality thick metallic glass films of the Metglas 2605 SC have been deposited using triode-magneton sputtering. This is the first time such material has been successfully deposited onto an optical fiber or onto any other substrate. The films were also deposited onto glass slides to allow the study of the magnetic properties of the film. The thicknesses of these films were 5-15 mum. The magnetic property of primary interest for our sensor application is the induced longitudinal magnetostrictive strain. However, the other magnetic properties such as magnetic anisotropy, surface and bulk coercivities, magnetic homogeneity and magnetization all affect the magnetostrictive response of the material. We have used ferromagnetic resonance (FMR) at microwave frequencies to study the magnetic anisotropy and homogeneity; vibrating sample magnetometry (VSM) to study the bulk magnetic hysteresis responses and coercivity; and the longitudinal magneto-optic kerr effect (LMOKE) to study the surface magnetic hysteresis responses and coercivity. The isothermalmagnetic annealing effect on these properties has also been studied in detail. The fiber optic magnetic field sensor constructed using the metallic-glass-coated fiber was tested. An electronic feedback control loop using a PZT cylinder was constructed for stabilizing the sensor operation. Magnetic field detection at different dither frequencies was studied in detail. The estimated minimum detectable magnetic field was about 3 times 10^{-7 } Oe. A simplified elastic model was used for the theoretical calculation of the phase shift induced in a metallic-glass -coated optical fiber with a longitudinal applied magnetic field. The phase shift as a function of coating thickness was calculated, and the experimental results at certain thicknesses were compared with the calculation. The frequency response of the FOMS was also studied in some detail. Three different configurations were used for the study of the frequency response. The results indicate that the resonances observed in the FOMS are most likely related to the mechanical resonance of the optical fiber.

Wang, Yu.

1990-01-01

4

Optical characterization of oligonucleotide DNA influenced by magnetic fields.  

PubMed

UV-VIS spectroscopic analysis of oligonucleotide DNA exposed to different magnetic fields was performed in order to investigate the relationship between DNA extinction coefficients and optical parameters according to magnetic-field strength. The results with the oligonucleotides adenine-thymine 100 mer (AT-100 DNA) and cytosine-guanine 100 mer (CG-100 DNA) indicate that the magnetic field influences DNA molar extinction coefficients and refractive indexes. The imaginary parts of the refractive index and molar extinction coefficients of the AT-100 and CG-100 DNA decreased after exposure to a magnetic field of 750 mT due to cleavage of the DNA oligonucleotides into smaller segments. PMID:24071986

Banihashemian, Seyedeh Maryam; Periasamy, Vengadesh; Mohammadi, Seyed Mohammad Hossein Mousa Kazemi; Ritikos, Richard; Rahman, Saadah Abdul

2013-09-25

5

Linear Birefringence and Linear Dichroism Coupled Optical Anisotropy of Magnetic Fluids by External Magnetic Fields  

Microsoft Academic Search

The optical anisotropy of magnetic fluids, including linear birefringence and linear dichroism simultaneously, under externally applied magnetic fields is investigated in this work. Analytical expressions to describe the polarization properties (direction of main polarization and degree of polarization) of the transmitted elliptically polarized light after the optically anisotropic magnetic fluids are obtained by theoretical derivation. Numerical examples are presented to

Shengli Pu; Min Dai; Guoqing Sun; Ming Liu

2009-01-01

6

Optically synthesized magnetic fields for ultracold neutral atoms  

NASA Astrophysics Data System (ADS)

Ultracold atoms hold great promise in simulating essential models in condensed matter physics. One apparent limitation is the charge neutrality of the atoms, which prevents access to a rich source of physics, for example, electrons in magnetic fields. We have circumvented this limitation by generating an effective vector potential with an optical coupling between internal states of the atoms. We have experimentally realized a synthetic magnetic field for ultracold neutral atoms, through the spatial variation of the effective vector potential. In our system, we use a two-photon Raman coupling to dress a rubidium 87 Bose-Einstein condensate (BEC), where the momentum difference between two Raman beams results in the modified energy-momentum dispersion of the dressed state, leading to an effective vector potential. We have created a synthetic magnetic field evidenced by the appearance of vortices in the BEC; this field is stable in the laboratory frame and allows for adding optical lattices with ease. Our optical approach is not subject to technical limitations of rotating systems, including the metastable nature of the rotating state, the limited maximum rotating velocity and the difficulty of applying stable rotating optical lattices. In our approach, with a suitable lattice configuration, it should be able to create sufficiently large synthetic magnetic fields in the quantum-Hall regime. Work done in collaboration with, Robert Compton, Karina Jimenez-Garcia, James Porto, and Ian Spielman, Joint Quantum Institute, National Institute of Standards and Technology, and University of Maryland.

Lin, Yu-Ju

2010-03-01

7

Vector optical fields with polarization distributions similar to electric and magnetic field lines.  

PubMed

We present, design and generate a new kind of vector optical fields with linear polarization distributions modeling to electric and magnetic field lines. The geometric configurations of "electric charges" and "magnetic charges" can engineer the spatial structure and symmetry of polarizations of vector optical field, providing additional degrees of freedom assisting in controlling the field symmetry at the focus and allowing engineering of the field distribution at the focus to the specific applications. PMID:23842405

Pan, Yue; Li, Si-Min; Mao, Lei; Kong, Ling-Jun; Li, Yongnan; Tu, Chenghou; Wang, Pei; Wang, Hui-Tian

2013-07-01

8

Optically synthesized electric and magnetic fields for ultracold neutral atoms  

NASA Astrophysics Data System (ADS)

Ultracold atoms hold great promise in simulating essential models in condensed matter physics. One apparent limitation is the charge neutrality of the atoms, preventing access to a rich source of physics, for example, electrons in magnetic fields. We have circumvented this limitation by generating an effective vector potential with an optical coupling between internal states of the atoms. We have made the first experimental realization of synthetic electric and magnetic fields for ultracold neutral atoms, through the temporal and spatial variation of the vector potential. In our system, we use a two-photon Raman coupling to dress a rubidium 87 Bose-Einstein condensate (BEC), where the momentum difference between two Raman beams results in the modified energy-momentum dispersion of the dressed state, leading to the effective vector potential. We have created a synthetic magnetic field evidenced by the appearance of vortices in the BEC; this field is stable in the laboratory frame and allows for adding optical lattices with ease. Our optical approach is not subject to the limitations of rotating systems; with a suitable lattice configuration, it should be able to create sufficiently large synthetic magnetic fields in the quantum-Hall regime. [Y.-J. Lin, R. L. Compton, K. Jimenez-Garcia, J. V. Porto, and I. B. Spielman, Nature, 462, 628 (2009).

Lin, Yu-Ju

2010-03-01

9

Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals  

NASA Astrophysics Data System (ADS)

Ferronematic materials composed of 4-cyano-4'-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (? n) and figure of merit of optical properties ( Q = ? n/?, where ? is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of Q R exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field.

Wang, Xiang; Pu, Shengli; Ji, Hongzhu; Yu, Guojun

2012-05-01

10

Enhanced magnetic-field-induced optical properties of nanostructured magnetic fluids by doping nematic liquid crystals.  

PubMed

Ferronematic materials composed of 4-cyano-4'-pentylbiphenyl nematic liquid crystal and oil-based Fe3O4 magnetic fluid were prepared using ultrasonic agitation. The birefringence (?n) and figure of merit of optical properties (Q?=??n/?, where ? is the extinction coefficient) of pure magnetic fluids and the as-prepared ferronematic materials were examined and compared. The figure of merit of optical properties weighs the birefringence and extinction of the materials and is more appropriate to evaluate their optical properties. Similar magnetic-field- and magnetic-particle-concentration-dependent properties of birefringence and figure of merit of optical properties were obtained for the pure magnetic fluids and the ferronematic materials. For the ferronematic materials, the values of Q increase with the volume fractions of nematic liquid crystal under certain fixed field strength and are larger than those of their corresponding pure magnetic fluids at high field region. In addition, the enhancement of Q value increases monotonously with the magnetic field and becomes remarkable when the applied magnetic field is beyond 50 mT. The maximum relative enhanced value of QR exceeds 6.8% in our experiments. The results of this work may conduce to extend the pragmatic applications of nanostructured magnetic fluids in optical field. PMID:22587542

Wang, Xiang; Pu, Shengli; Ji, Hongzhu; Yu, Guojun

2012-05-15

11

Magnetic field optical sensors using (TbY)IG crystals with stripe magnetic domain structure  

Microsoft Academic Search

In this paper, a new type of magnetic field optical sensor based on Faraday effect created by the magnetization rotation process in each stripe magnetic domain is proposed. For these sensors, (Tb0.19Y0.81)3Fe5O12 ((TbY)IG) crystals were used as Faraday element. At the wavelength of 1.3 ?m, the obtained sensitivity is 4.7×10-3 %\\/A\\/m. The small linearity error of the sensor output is

Kinya Okubo; Osamu Kamada

2005-01-01

12

Optical Signatures from Magnetic 2-D Electron Gases in High Magnetic Fields to 60 Tesla  

SciTech Connect

We present experiments in the 60 Tesla Long-Pulse magnet at the Los Alamos National High Magnetic Field Lab (NHMFL) focusing on the high-field, low temperature photoluminescence (PL) from modulation-doped ZnSe/Zn(Cd,Mn)Se single quantum wells. High-speed charge-coupled array detectors and the long (2 second) duration of the magnet pulse permit continuous acquisition of optical spectra throughout a single magnet shot. High-field PL studies of the magnetic 2D electron gases at temperatures down to 350mK reveal clear intensity oscillations corresponding to integer quantum Hall filling factors, from which we determine the density of the electron gas. At very high magnetic fields, steps in the PL energy are observed which correspond to the partial unlocking of antiferromagnetically bound pairs of Mn2+ spins.

Crooker, S.A.; Kikkawa, J.M.; Awschalom, D.D.; Smorchikova, I.P.; Samarth, N.

1998-11-08

13

Magneto-Optical Apparatus and Method for the Spatially-Resolved Detection of Weak Magnetic Fields.  

National Technical Information Service (NTIS)

A detector uses the magneto-optical Kerr effect and exploits the transition region between two magnetization states of a magneto-optical film to detect magnetic fields of less than 100 pT. The magnetic field of a subject is determined by examining the pol...

J. Gao J. G. Eden

2003-01-01

14

Fiber Optic Magnetometer for the Detection of DC Magnetic Fields without Hysteretic Ambiguity.  

National Technical Information Service (NTIS)

This invention relates to magnetometers, and more particularly to magnetometers of the fiber optic type. Sensing of magnetic fields using fiber optic interferometers has been demonstrated recently. In these devices, a two-arm Mach-Zehnder fiber interferom...

K. P. Koo G. H. Siegel

1984-01-01

15

Three-dimensional magnetic trap lattice on an atom chip with an optically induced fictitious magnetic field  

SciTech Connect

A robust type of three-dimensional magnetic trap lattice on an atom chip combining optically induced fictitious magnetic field with microcurrent-carrying wires is proposed. Compared to the regular optical lattice, the individual trap in this three-dimensional magnetic trap lattice can be easily addressed and manipulated.

Yan Hui [Laboratory of Quantum Information Technology, ICMP and SPTE, South China Normal University, Guangzhou 510006 (China)

2010-05-15

16

Artificial staggered magnetic field for ultracold atoms in optical lattices  

NASA Astrophysics Data System (ADS)

A time-dependent optical lattice with staggered particle current in the tight-binding regime was considered that can be described by a time-independent effective lattice model with an artificial staggered magnetic field. The low-energy description of a single-component fermion in this lattice at half-filling is provided by two copies of ideal two-dimensional massless Dirac fermions. The Dirac cones are generally anisotropic and can be tuned by the external staggered flux ?. For bosons, the staggered flux modifies the single-particle spectrum such that in the weak coupling limit, depending on the flux ?, distinct superfluid phases are realized. Their properties are discussed, the nature of the phase transitions between them is established, and Bogoliubov theory is used to determine their excitation spectra. Then the generalized superfluid-Mott-insulator transition is studied in the presence of the staggered flux and the complete phase diagram is established. Finally, the momentum distribution of the distinct superfluid phases is obtained, which provides a clear experimental signature of each phase in ballistic expansion experiments.

Lim, Lih-King; Hemmerich, Andreas; Smith, C. Morais

2010-02-01

17

Molecules in optical, electric, and magnetic fields: a personal perspective.  

PubMed

Physical chemistry and theoretical chemistry have advanced over the past 50 years from being largely qualitative to having a mature status based firmly on the principles of quantum and statistical mechanics. My interest in the chemical elements and their compounds has prompted me to learn more about the nature of matter through the measurement and interpretation of optical, electric, and magnetic properties of molecules. In addition to holding intrinsic interest, such properties tell us about charge and current distributions and form the basis of electro-optics, magneto-optics, and nonlinear optics. They also help us understand the nature and strength of long-range intermolecular forces, the hydrogen bond, and molecular biology-topics that are apparently forever young. PMID:15012437

Buckingham, A D

1998-01-01

18

Magnetic anisotropy in a permalloy microgrid fabricated by near-field optical lithography  

SciTech Connect

We report the fabrication and magnetic properties of permalloy microgrids prepared by near-field optical lithography and characterized using high-sensitivity magneto-optical Kerr effect techniques. A fourfold magnetic anisotropy induced by the grid architecture is identified. {copyright} 2001 American Institute of Physics.

Li, S. P.; Lebib, A.; Peyrade, D.; Natali, M.; Chen, Y.; Lew, W. S.; Bland, J. A. C.

2001-07-01

19

Optical Imaging and Magnetic Field Targeting of Magnetic Nanoparticles in Tumors  

PubMed Central

To address efficacy issues of cancer diagnosis and chemotherapy, we have developed a magnetic nanoparticle (MNP) formulation with combined drug delivery and imaging properties that can potentially be used in image-guided drug therapy. Our MNP consists of an iron-oxide magnetic core coated with oleic acid (OA) and stabilized with an amphiphilic block copolymer. Previously, we reported that our MNP formulation can provide prolonged contrast for tumor magnetic resonance imaging and can be loaded with hydrophobic anticancer agents for sustained drug delivery. In this study, we developed MNPs with optical imaging properties using new near-infrared dyes to quantitatively determine their long-term biodistribution and tumor localization with and without an external magnetic field in mice with xenograft breast tumors. MNPs localized slowly in the tumor, reaching a peak 48 h post injection before slowly declining over the next 11 days. One-hour exposure of the tumor to a magnetic field further enhanced MNP localization to tumors. Our MNPs can be developed with combined drug delivery and multimodal imaging properties to improve cancer diagnosis, provide sustained treatment, and monitor therapeutic effects in tumors over time.

Foy, Susan P.; Manthe, Rachel L.; Foy, Steven T.; Dimitrijevic, Sanja; Krishnamurthy, Nishanth; Labhasetwar, Vinod

2010-01-01

20

Neutron spin filter based on optically polarized 3 He in a near-zero magnetic field  

Microsoft Academic Search

A test of polarization of 3He nuclei via spin-exchange collisions with optically pumped rubidium atoms in an extremely low applied magnetic field was carried out. Permalloy magnetic shields were used to prevent a fast relaxation of 3He polarization owing to the inhomogeneity of a surrounding magnetic field. The whole installation was placed at the neutron beam line of the IBR-30

V. R Skoy; Yu. V. Prokofichev; V. N Sorokin; N. N. Kolachevski; I. I. Sobelman; A. V. Sermyagin

2003-01-01

21

Fiber-optic Faraday-effect magnetic-field sensor based on flux concentrators.  

PubMed

The principles and performance of a fiber-optic Faraday-effect magnetic-field sensor designed around an yttrium-iron-garnet (YIG) sensing element and two flux concentrators are described. The system design exploits the technique of polarization-rotated reflection in which a single polarization-maintaining optical fiber links the sensor head to the optical source and detection system. In the sensing head, ferrite flux concentrators are magnetically coupled to the YIG sensing element to achieve maximum sensitivity. The system exhibits a noise equivalent field of 6 pT/?Hz and a 3-dB bandwidth of~10 MHz. PMID:21068992

Deeter, M N

1996-01-01

22

Linear and nonlinear optical properties of anisotropic quantum dots in a magnetic field  

NASA Astrophysics Data System (ADS)

We have investigated the linear and nonlinear optical properties of a two-dimensional anisotropic quantum dot in a magnetic field. Based on the computed energies and wave functions, the linear, third-order nonlinear and total optical absorption coefficients as well as the refractive index changes have been examined. The results are presented as a function of the incident photon energy for the different cases of anisotropy, dot size and external magnetic field. The results show that the linear and nonlinear optical properties of anisotropic quantum dots are strongly affected by the degree of anisotropy, the dot size, the external magnetic field and the polarized direction of the incident electromagnetic wave. The result also shows that the size effect of anisotropy quantum dots on the optical absorptions is different from that of isotropic quantum dots.

Xie, Wenfang

2013-05-01

23

High sensitivity fiber-optic magnetic field sensors based on iron garnets  

Microsoft Academic Search

Ferrimagnetic iron garnet crystals form the basis of magneto-optic magnetic field sensors which offer high sensitivity, broadband frequency response, and fiber-optic compatability. Recent developments at NIST promise still greater performance for these sensors based on the magneto-optic Faraday effect. Specifically, new sensor head designs incorporating flux concentration devices and novel experimental iron garnet compositions demonstrate the potential for enhancing the

M. N. Deeter

1994-01-01

24

A novel all-fiber magneto-optic switch based on high-speed magnetic field module  

Microsoft Academic Search

All-fiber magneto-optic switch is presented in this paper which contains both of optical route and high-speed magnetic field module. The optical route has a 1×2 Fiber Polarization Beam Splitter (FPBS) and a 2×2 Dual Fiber Polarization Beam Splitter (DFPBS). The high-speed magnetic field module is core of all-fiber magneto-optic switch which changes the electronic pulse into magnetic pulse to control

Minfeng Wang; Zihua Weng; Xu Chen; Shaohan Lin; Qinping Wu

2007-01-01

25

Transmission and reflection of transverse-magnetic-polarized optical fields at stratified nonlinear media  

Microsoft Academic Search

For the first time we study the transmission and the reflection of transverse-magnetic-polarized optical fields which impinge obliquely on diverse multilayer systems showing distinct resonances of geometrical origin in the low-intensity limit. The individual layers are endowed with nonlinear materials, the complex dielectric functions of which depend on the local intensity of the optical wave. The field propagation is described

U. Trutschel; F. Lederer; U. Langbein

1989-01-01

26

Optical magnetic field probe working up to 15 GHz using CdTe electrooptic Crystals  

Microsoft Academic Search

This paper presents a new type of optical magnetic field probe designed to detect magnetic near-fields with high accuracy up to 15 GHz. The probe head consists of a loop antenna element and CdTe electrooptic crystals. The probe using CdTe has a resonant frequency higher than that of a previous probe using LiNbO3 because CdTe has a dielectric constant lower

Eiji Suzuki; Satoru Arakawa; Hiroyasu Ota; Ken Ichi Arai; Risaburo Sato

2005-01-01

27

Interferometric optical isolator employing a nonreciprocal phase shift operated in a unidirectional magnetic field.  

PubMed

An interferometric optical isolator that employs a nonreciprocal phase shift was studied. The optical isolator consisted of an interferometer with distinct layer structures. A traveling light wave underwent distinct nonreciprocal phase shifts such that the optical isolator could be operated in a unidirectional magnetic field. The optical isolator, in which the waveguide had a HfO2 cladding layer in one of the arms, was designed at a wavelength of 1.55 microm. The propagation distance of the nonreciprocal phase shifter required for the isolator's operation was less than 1.5 mm. The device's total length was less than 2 mm. An optical isolator with distinct layer structures was fabricated and evaluated. An isolation ratio of approximately 9.9 dB was obtained in the unidirectional magnetic field. PMID:15352401

Yokoi, Hideki; Shoji, Yuya; Shin, Etsu; Mizumoto, Tetsuya

2004-08-20

28

Observation of magnetic field-induced contraction of fission yeast cells using optical projection microscopy  

NASA Astrophysics Data System (ADS)

The charges in live cells interact with or produce electric fields, which results in enormous dielectric responses, flexoelectricity, and related phenomena. Here we report on a contraction of Schizosaccharomyces pombe (fission yeast) cells induced by magnetic fields, as observed using a phase-sensitive projection imaging technique. Unlike electric fields, magnetic fields only act on moving charges. The observed behavior is therefore quite remarkable, and may result from a contractile Lorentz force acting on diamagnetic screening currents. This would indicate extremely high intracellular charge mobilities. Besides, we observed a large electro-optic response from fission yeast cells.

Yang, Xi; Beckwith, A. W.

2005-03-01

29

Optical dc current and voltage measurement by superposing ac magnetic or electric field  

NASA Astrophysics Data System (ADS)

Optical DC current and voltage measurement using Faraday or Pockels effect necessitates the compensation of light intensity variation with some methods, because it is possible the intensity variation may give rise to a measuring error. We have proposed a method which suggests superposing AC magnetic field on linearly polarized light or AC electric field on elliptically polarized light and compensating light intensity variation by detecting AC components caused by constant AC magnetic or electric field. Experiments of long term stability for DC current and voltage measurement were carried out by using flint glass for DC current measurement and B12SiO20 (BSO) crystals for DC voltage measurement. An experimental result of DC current measurement where DC current of 1.0 A was passed under AC current of 1 kHz 1.5 Arms showed that the modulation depth without compensation through AC magnetic field varied largely with time because of the temperature rise of the flint glass, but that with compensation through AC magnetic field hardly varied with time and the effectiveness of AC magnetic field superposition was confirmed. The same compensation method was applied to optical DC voltage measurement using Pockels effect. An experimental result of DC voltage measurement where DC voltage of 500 V was applied under AC voltage of 5 kHz 50 Vrms clarified that the time variation of the modulation depth with compensation through AC electric field was small compared with that without compensation through AC electric field.

Higaki, Masaru; Fujii, Kunio; Yamaguchi, Shizuo

1999-05-01

30

Neutron spin filter based on optically polarized 3He in a near-zero magnetic field  

NASA Astrophysics Data System (ADS)

A test of polarization of 3He nuclei via spin-exchange collisions with optically pumped rubidium atoms in an extremely low applied magnetic field was carried out. Permalloy magnetic shields were used to prevent a fast relaxation of 3He polarization owing to the inhomogeneity of a surrounding magnetic field. The whole installation was placed at the neutron beam line of the IBR-30 facility, and used as a neutron spin filter. Thus, a prototype of new design of neutron polarizer was introduced. We intend to apply this experience for the full-scale KaTRIn facility to test the time reversal violation in neutron-nuclear reactions.

Skoy, V. R.; Prokofichev, Yu. V.; Sorokin, V. N.; Kolachevski, N. N.; Sobelman, I. I.; Sermyagin, A. V.

2003-04-01

31

High Pressure Optical Absorption in Cs 2 TCNQ 3 Complexes Grown Under the Influence of Magnetic Field  

Microsoft Academic Search

Crystals of the organic semiconductor Cs 2 TCNQ 3 have been grown under the influence of magnetic field of 5 T and their optical properties have been compared with the crystals grown without magnetic field. The magnetic field effect manifests itself as the enhancement of the intradimer charge transfer band S 1 , which appears at around 1.3 eV in

Hasanudin; N. Kuroda; T. Kagayama; T. Sugimoto; I. Mogi; K. Watanabe; M. Motokawa

2002-01-01

32

Optical emission, electron energy, density, wave magnetic field and spectrum measurements in a helicon plasma source  

Microsoft Academic Search

Summary form only given. Measurements and analysis of optical emission, electron energy analyzer, Langmuir and magnetic probe and wave spectra are presented for a wide range of helicon plasma source conditions. Helicon plasma source characteristics at lower argon neutral pressures of 2-6 mTorr at both low (200 G) and high (1.2 kG) magnetic field strengths and at high pressures (100

J. Scharer; B. White; S. Tysk; E. Paller; K. Akhtar

2002-01-01

33

Optical studies of multilayer graphene in magnetic fields  

Microsoft Academic Search

We report the optical properties of multilayer graphene thin films grown on silicon substrate. The room-temperature reflectance and transmittance of the samples were measured over the energy range from the far-infrared to near-infrared. To extract the optical constants of the films, we analyzed all of the layers of this thin-film structure using a Drude-Lorentz model. From the parameters obtained, we

Hsiang-Lin Liu; G. L. Carr; K. A. Worsley; M. E. Itkis; E. Bekyarova; R. C. Haddon; A. N. Caruso

2008-01-01

34

Experimental Realization of Strong Effective Magnetic Fields in an Optical Lattice  

SciTech Connect

We use Raman-assisted tunneling in an optical superlattice to generate large tunable effective magnetic fields for ultracold atoms. When hopping in the lattice, the accumulated phase shift by an atom is equivalent to the Aharonov-Bohm phase of a charged particle exposed to a staggered magnetic field of large magnitude, on the order of 1 flux quantum per plaquette. We study the ground state of this system and observe that the frustration induced by the magnetic field can lead to a degenerate ground state for noninteracting particles. We provide a measurement of the local phase acquired from Raman-induced tunneling, demonstrating time-reversal symmetry breaking of the underlying Hamiltonian. Furthermore, the quantum cyclotron orbit of single atoms in the lattice exposed to the magnetic field is directly revealed.

Aidelsburger, M.; Atala, M.; Trotzky, S.; Chen, Y.-A.; Bloch, I. [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet, Schellingstrasse 4, 80799 Muenchen (Germany); Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Nascimbene, S. [Fakultaet fuer Physik, Ludwig-Maximilians-Universitaet, Schellingstrasse 4, 80799 Muenchen (Germany); Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, 85748 Garching (Germany); Laboratoire Kastler Brossel, CNRS, UPMC, Ecole Normale Superieure, 24 rue Lhomond, 75005 Paris (France)

2011-12-16

35

Fiber optic DC magnetic field sensor with alternating current phase tracing  

Microsoft Academic Search

A sensitive DC magnetic field sensor based on magnetostrictive straining of optical fibers was demonstrated, which utilizes alternating current phase tracing (PTAC) homodyne scheme to eliminate phase drift. Comparison was carried out experimentally between direct current phase tracing (PTDC) and alternating current phase tracing, then expressions were presented. The results showed that the PTAC had better performance both in stabilization

Jianguang Xin; Mengchun Pan; Dixiang Chen; Qi Zhang; JiaFei Hu

2009-01-01

36

Observations of optical emissions and magnetic fields aboard of INTERBALL-2 satellite  

Microsoft Academic Search

In the work, the Bulgarian experiments aboard of the INTERBALL-Auroral probe satellites, namely the investigation of optical emissions in the ultra violet (UV) range (UVSIPS spectrometer) and the magnetic field experiment (IMAP-3 magnetometer), are described. To illustrate the common analysis of data from both units, the observations during the October 19, 1996 geomagnetic storm are analysed.

Kunyo Palazov; Stefan Spasov; Alexander Bochev; Petar Baynov

2003-01-01

37

Split ring aperture for optical magnetic field enhancement by radially polarized beam.  

PubMed

Inspired by Babinet's principle, we proposed a new plasmonic structure for enhancing the optical magnetic field, i.e. split ring aperture, whose complement is the well-known split ring. The split ring aperture exhibits a much better performance under radially polarized excitation than linearly polarized excitation. We attribute the ultra-high intensity enhancement in magnetic field to the symmetric matching between the aperture geometry and the direction of the electric field vector in each direction of radially excitation. The impact of the design parameters on the intensity enhancement and resonant wavelength is also investigated in details. PMID:23546066

Yang, Y; Dai, H T; Sun, X W

2013-03-25

38

Optical Transmittance and Dynamic Properties of Ferrofluids (Fe$_{3}$ O$_{4}$ ) Under DC-Biased Magnetic Fields  

Microsoft Academic Search

The dynamic property of ferrofluids under a dc-biased magnetic field was understood by the measurement of optical transmittance. The results show that immediately after the application of a magnetic field, the transmitted optical intensity decreases to a minimum and, then, increases until it becomes stable. From the microscopic images, they indicate that this effect is due to longitudinal aggregation of

Min-Feng Chung; Chao-Ming Fu

2011-01-01

39

Synchronized time- and high-field-resolved all-optical pump-probe magneto-optical setup based on a strong alternating magnetic field and its application in magnetization dynamics of high coercivity magnetic medium  

NASA Astrophysics Data System (ADS)

An alternating magnetic field (AMF) apparatus is developed and composed of an electromagnet and driving power supply. The structure of the electromagnet and configuration of the driving supply are described in detail. The apparatus can produce a peak magnetic field up to 9000 Oe and above under a small driving power at its resonance frequency of 1.14 kHz. Based on synchronization between the AMF and the femtosecond laser pulse train, a photomagnetic synchronized time- and high-field-resolved all-optical pump-probe magnetic-optical setup is developed. This setup has the ability to reinitialize any magnetic states between two successive laser pulses so that irreversible magnetization reversal dynamics can be studied. Dynamic Kerr hysteresis loops and magnetization reversal dynamics of high coercivity ferromagnetic TbFeCo and FePt films are demonstrated using this setup, showing importance of this synchronized time- and high-field-resolved all-optical pump-probe magnetic-optical setup in the research of ultrafast magnetization dynamics.

Wang, Zi-Xin; Li, Jia-Ming; Deng, Jun-Qi; Chen, Zhi-Feng; Lai, Tian-Shu

2011-03-01

40

Determination of Electric-Field, Magnetic-Field, and Electric-Current Distributions of Infrared Optical Antennas: A Near-Field Optical Vector Network Analyzer  

SciTech Connect

In addition to the electric field E(r), the associated magnetic field H(r) and current density J(r) characterize any electromagnetic device, providing insight into antenna coupling and mutual impedance. We demonstrate the optical analogue of the radio frequency vector network analyzer implemented in interferometric homodyne scattering-type scanning near-field optical microscopy (s-SNOM) for obtaining E(r), H(r), and J(r). The approach is generally applicable and demonstrated for the case of a linear coupled-dipole antenna in the midinfrared. The determination of the underlying 3D vector electric near-field distribution E(r) with nanometer spatial resolution and full phase and amplitude information is enabled by the design of probe tips with selectivity with respect to Ek and E? fabricated by focused ion-beam milling and nano-CVD.

Olmon, Robert L.; Rang, Matthias; Krenz, Peter M.; Lail, Brian A.; Saraf, Laxmikant V.; Boreman, Glenn D.; Raschke, Markus Bernd

2010-10-15

41

Nonlinear magneto-optical rotation with modulated light in tilted magnetic fields  

SciTech Connect

Larmor precession of laser-polarized atoms contained in antirelaxation-coated cells, detected via nonlinear magneto-optical rotation (NMOR), is a promising technique for a new generation of ultrasensitive atomic magnetometers. For magnetic fields directed along the light propagation direction, resonances in NMOR appear when linearly polarized light is frequency or amplitude modulated at twice the Larmor frequency. Because the frequency of these resonances depends on the magnitude but not the direction of the field, they are useful for scalar magnetometry. Additional NMOR resonances at the Larmor frequency appear when the magnetic field is tilted away from the light propagation direction in the plane defined by the light propagation and polarization vectors. These resonances, studied both experimentally and with a density matrix calculation in the present work, offer a convenient method of achieving additional information about a direction of the magnetic field.

Pustelny, S.; Gawlik, W.; Rochester, S. M.; Kimball, D. F. Jackson; Yashchuk, V. V.; Budker, D. [Centrum Badan Magnetooptycznych, M. Smoluchowski Institute of Physics, Jagiellonian University, Reymonta 4, 30-059 Krakow (Poland); Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 (United States); Department of Physics, California State University--East Bay, 25800 Carlos Bee Boulevard, Hayward, California 94542 (United States); Advanced Light Source Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300, USA and Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2006-12-15

42

Mirror magneto-optical trap exploiting hexapole-compensated magnetic field  

SciTech Connect

A mirror magneto-optical trap (MOT) that exploits a hexapole-compensated magnetic field was developed and used in the experimental surface trapping of neutral atoms. A pair of subsidiary wires, which was placed near the main current-carrying wire, was designed to improve the uniformity of the quadrupole magnetic field and thus increased the effective capture volume of our mirror-MOT. In the experiment, the number of {sup 87}Rb atoms captured with our mirror-MOT was approximately twice that captured with a conventional mirror-MOT.

Hyodo, Masaharu [Kobe Advanced ICT Research Center, NICT, 588-2 Iwaoka, Nishi-ku, Kobe 651-2492 (Japan); Nakayama, Kazuyuki [CREST, Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Watanabe, Masayoshi [Department of Electronic Engineering, University of Electro-Communications, Chofu 182-8585 (Japan); Ohmukai, Ryuzo [Department of Physics, Saitama University, Saitama 338-8570 (Japan)

2007-07-15

43

Measurement of Asymmetric Optical Pumping of Ions Accelerating in a Magnetic-field Gradient  

SciTech Connect

We report observations of asymmetric optical pumping of argon ions accelerating in a magnetic field gradient. The signature is a difference in the laser-induced-fluorescence (LIF) emission amplitude from a pair of Zeeman-split states. A model that reproduces the dependence of the asymmetry on magnetic-field and ion-velocity gradients is described. With the model, the fluorescence intensity ratio provides a new method of measuring ion collisionality. This phenomenon has implications for interpreting stellar plasma spectroscopy data which often exhibit unequal Zeeman state intensities.

Xuan Sun; Earl Scime; Mahmood Miah; Samuel Cohen; Frederick Skiff

2004-10-28

44

Cold atom trap with zero residual magnetic field: the ac magneto-optical trap.  

PubMed

A novel atom trap is described using alternating current to generate the magnetic B field, together with high speed polarization switching of the damping laser field. This combination produces a trap as effective as a standard magneto-optical trap (MOT), with the advantage that the average B field is zero. No net current is hence induced in surrounding conductive elements, and the B field produced by the ac MOT is found to switch off >300 times faster than a conventional MOT. New experiments can hence be performed, including charged particle probing or detection of the cold target ensemble. PMID:18999746

Harvey, Matthew; Murray, Andrew James

2008-10-22

45

Detection of radio-frequency magnetic fields using nonlinear magneto-optical rotation  

SciTech Connect

We describe a room-temperature alkali-metal atomic magnetometer for detection of small, high-frequency magnetic fields. The magnetometer operates by detecting optical rotation due to the precession of an aligned ground state in the presence of a small oscillating magnetic field. The resonance frequency of the magnetometer can be adjusted to any desired value by tuning the bias magnetic field. Based on experimentally measured signal-to-noise ratio, we demonstrate a sensitivity of 100 pG/{radical}(Hz) (rms) in a 3.5-cm-diameter paraffin coated cell. Assuming detection at the photon shot-noise limit, we project a sensitivity as low as 25 pG/{radical}(Hz) (rms)

Ledbetter, M. P.; Acosta, V. M.; Rochester, S. M.; Budker, D.; Pustelny, S.; Yashchuk, V. V. [Department of Physics, University of California at Berkeley, Berkeley, California 94720-7300 (United States); Centrum Badan Magnetooptycznych, Instytut Fizyki im. M. Smoluchowskiego, Uniwersytet Jagiellonski, Reymonta 4, 30-059 Krakow (Poland); Advanced Light Source Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2007-02-15

46

Analyses of Magnetic Field Distributions for the Measurement of Magnetic Resonance Signals using Optically Pumped Atomic Magnetometers  

NASA Astrophysics Data System (ADS)

In ultra-low field MRI with optically pumped atomic magnetometer (OPAM), it is required for the direct detection of MR signals with high sensitivity to match the resonant frequency of potassium to that of proton. A ferrite shield box, which has high-permeability and high electric resistance, is able to be utilized to match the resonant frequencies. In this study, analyses of magnetic field distributions in the vicinities of sample and potassium vapor cell of OPAM were carried out. In addition, the uniformities of the magnetic fields in the areas of sample and potassium vapor cell of OPAM and the magnetic field caused by MR signals were evaluated. These analyses indicated that the resonant frequencies of proton and potassium were matched by using the ferrite shield box with a number of combinations of height and thickness. The uniformities of the magnetic fields applied to a sample were found to be improved by placing the ferrite shield box far from the sample. Furthermore, regardless of the height, the magnetic field caused by MR signals was able to be measured.

Tsuchida, Masahiro; Oida, Takenori; Kobayashi, Tetsuo

47

Magnetic field alignment of supramolecular perylene/block copolymer complexes for electro-optic thin films  

NASA Astrophysics Data System (ADS)

The realization of nanostructured electro-optic materials by self-assembly is complicated by the persistence of structural defects which render the system properties isotropic on macroscopic length scales. Here we demonstrate the use of magnetic fields to facilitate large area alignment of a supramolecular system consisting of a poly(styrene-b-acrylic acid) (PS-b-PAA) diblock copolymer host and a semiconducting perylene ligand. Hydrogen bonding between the carboxylic acid groups of PAA and imidazole head group of the perylene species results in hierarchically ordered materials with smectic perylene layers in a matrix of hexagonally packed PS cylinders at appropriate stoichiometries. The smectic layers and the PS domains are strongly aligned by the application of large (> 2T) magnetic fields in a manner reflective of the positive diamagnetic anisotropy and the planar anchoring of perylene units at the PS interface. We use a combination of SAXS studies in-situ with applied magnetic fields, GISAXS and polarized optical transmission measurements to characterize the system. Magnetic fields thus offer a viable route for directing the self-assembly of functional materials based on rigid chromophores and further, that supramolecular approaches can be complementary to such efforts.

Gopinadhan, Manesh; Majewski, Pawel; Shade, Ryan; Dell, Emma; Gupta, Nalini; Campos, Luis; Osuji, Chinedum

2012-02-01

48

Optical orientation of Mn2+ ions in GaAs in weak longitudinal magnetic fields.  

PubMed

We report on optical orientation of Mn2+ ions in bulk GaAs subject to weak longitudinal magnetic fields (B?100??mT). A manganese spin polarization of 25% is directly evaluated by using spin-flip Raman scattering. The dynamical Mn2+ polarization occurs due to the s-d exchange interaction with optically oriented conduction band electrons. Time-resolved photoluminescence reveals a nontrivial electron spin dynamics, where the oriented Mn2+ ions tend to stabilize the electron spins. PMID:21561222

Akimov, I A; Dzhioev, R I; Korenev, V L; Kusrayev, Yu G; Sapega, V F; Yakovlev, D R; Bayer, M

2011-04-05

49

Magnetic Field Mapping and Biaxial Vector Operation for Biomagnetic Applications Using High-Sensitivity Optically Pumped Atomic Magnetometers  

NASA Astrophysics Data System (ADS)

Optically pumped alkali-metal atomic magnetometers are expected to be used not only for biomagnetic field measurements but also for magnetic resonance imaging because of their potential ultrahigh sensitivity. Here, we studied magnetic field mapping and biaxial vector operation using atomic magnetometers. A potassium atomic magnetometer was used in these measurements. First, we obtained sensor output signals by solving the Bloch equation. Next, we measured magnetic field distributions generated by a current dipole electrode that was placed in a spherical phantom, which simulated a group of simultaneously activated neurons in the human brain. We obtained vector contour maps of the magnetic field distributions from the dipoles oriented parallel and orthogonal to the pump laser beam and have found good agreement with theoretical magnetic field distributions. These results demonstrate practical applications of magnetic field mapping and biaxial vector operation using optically pumped atomic magnetometers.

Taue, Shuji; Sugihara, Yasuyuki; Kobayashi, Tetsuo; Ishikawa, Kiyoshi; Kamada, Keigo

2011-11-01

50

Fiber-optic extrinsic Fabry-Perot dc magnetic field sensor  

NASA Astrophysics Data System (ADS)

We demonstrate a compact extrinsic Fabry-Perot interferometer-based fiber-optic sensor that uses magnetostrictive amorphous metallic wire Unitika AF-10 (Fe_77.5B_15Si_7.5) as a sensor gauge for measuring dc magnetic fields. We present a theoretical model based on a Gaussian electric field distribution to analyze the sensor operation as a function of longitudinal air-gap separation. The model shows good agreement with the experimental results. A resolution of 50 nT over a range of 50-40,000 nT with a simple passive temperature-compensation method is obtained.

Oh, Ki D.; Wang, Anbo; Claus, Richard O.

2004-09-01

51

Fiber-optic extrinsic Fabry-Perot dc magnetic field sensor.  

PubMed

We demonstrate a compact extrinsic Fabry-Perot interferometer-based fiber-optic sensor that uses magnetostrictive amorphous metallic wire Unitika AF-10 (Fe77.5B15Si7.5) as a sensor gauge for measuring dc magnetic fields. We present a theoretical model based on a Gaussian electric field distribution to analyze the sensor operation as a function of longitudinal air-gap separation. The model shows good agreement with the experimental results. A resolution of 50 nT over a range of 50-40,000 nT with a simple passive temperature-compensation method is obtained. PMID:15460874

Oh, Ki D; Wang, Anbo; Claus, Richard O

2004-09-15

52

Optical fiber Fabry-Perot interferometric sensor for magnetic field measurement  

Microsoft Academic Search

A fiber-optic sensor based on the extrinsic Fabry-Perot interferometer (EFPI) is demonstrated to measure dc magnetic fields (100-35000 nT). A Metglas (Fe77.5B15Si7.5) wire-based magnetostrictive transducer is used as the reflector in two quadrature-phase-shifted EFPI sensor elements which are used to overcome phase ambiguity in the interferometric sensor. The simple sensor geometry gives both relatively low-vibration sensitivity and better than 99%

Ki Dong Oh; Jaydeep Ranade; Vivek Arya; Anbo Wang; Richard O. Claus

1997-01-01

53

Metallic-glass-coated optical fibers as magnetic-field sensors  

NASA Astrophysics Data System (ADS)

MetglasTM 2605 SC cast alloy was deposited directly onto single-mode optical fibers. Very thick amorphous films of 5 to 15 micrometers thickness were produced by triode-magnetron sputtering. The coated fibers were used as magnetic field sensing elements in one arm of a Mach-Zehnder interferometer. In the reference arm a section of fiber was wound around a piezoelectric (PZT) cylinder which was driven by a feedback correction signal to keep the sensor operating at quadrature. The sensing element was placed inside a chamber containing Helmholtz coils which produced both a dc field and an ac dither field. The magnetostructure response of the coating and the resulting phase shift in the optical fiber are dependent upon both of these fields. The phase shifts were measured as a function of the magnitudes of the dc and ac fields and the frequency of the ac field. The magnetostrictive responses had maximum values at discrete resonance frequencies. Experimental values of the magnetostriction parameter were obtained using experimental values of the phase shifts along with theoretical calculations of the magnetostrictive response. These calculations were based on a model of coherent rotation of magnetization and also an elastic model of the magnetostrictive strains for a cylindrical geometry. The maximum values of the magnetostriction parameter for the coated- fiber FOMS at resonance was estimated to be 10-5/Oe2 in comparison with non-resonant values of 5X10-5/Oe2 and 1X10-6/Oe2 for amorphous metal wire transducers and Metglas strip transducers, respectively, and 5X10-6/Oe2 for resonant Metglas cylindrical transducers.

Larson, Donald C.; Bibby, Yu Wang; Tyagi, S.

1991-08-01

54

Observations of vector magnetic fields with a magneto-optic filter  

NASA Astrophysics Data System (ADS)

The use of the magnetooptic filter to observe solar magnetic fields in the potassium line at 7699 A is described. The filter has been used in the Big Bear videomagnetograph since October 23. It gives a high sensitivity and dynamic range for longitudnal magnetic fields and enables measurement of transverse magnetic fields using the sigma component. Examples of the observations are presented.

Cacciani, Alessandro; Varsik, John; Zirin, Harold

1990-01-01

55

Defect-induced magneto-optic properties of MgO nanoparticles realized as optical-fiber-based low-field magnetic sensor  

NASA Astrophysics Data System (ADS)

The spintronic applications of defect-magnetism in oxides have been explored for a long time. However, limited success has been obtained. We report on FCC-structured, magnesium oxide nanoparticles (20 nm) deposited on the mirror-surface of single-mode-optical-fiber as an effective low-field magnetic sensor. These show magnetic behavior and good magneto-optic-Kerr-effect signal. Red-shift phenomenon has been found in the birefringence pattern, when a magnetic field is applied. The sensitivity of red-shift is 202.4 pm/mT. Such red-shift phenomenon is ascribed to the influences of defect-induced magnetism on the optical-wave propagation.

Rao, Ch. N.; Nakate, Umesh T.; Choudhary, R. J.; Kale, S. N.

2013-10-01

56

Frontiers in diffraction unlimited optical methods for spin manipulation, magnetic field sensing and imaging using diamond nitrogen vacancy defects  

NASA Astrophysics Data System (ADS)

The nitrogen vacancy defect centre in diamond has attracted intense research interest owing to their appealing optical and electronic properties, which have laid the ground for new approaches for diffraction unlimited optical methods. In particular, the optical detected magnetic resonance of the electron spin of nitrogen vacancy centre at room temperature underpins many areas in nanophotonics, spintronics and quantum optics. This article reviews the recent development of super-resolution imaging and sensing nanoscopy based on this fascinating defect centre in diamond. These breakthroughs are presently indicating a new class of nanoscale sensors of tiny magnetic and electric fields at room temperature, as well as emerging fluorescent and magnetic probes for next generation nanoscopy and all-optical spin recording.

Castelletto, Stefania; Li, Xiangping; Gu, Min

2012-11-01

57

Optical response of magnetic fluorescent microspheres used for force spectroscopy in the evanescent field.  

PubMed

Force spectroscopy based on magnetic tweezers is a powerful technique for manipulating single biomolecules and studying their interactions. The resolution in magnetic probe displacement, however, needs to be commensurate with molecular sizes. To achieve the desirable sensitivity in tracking displacements of the magnetic probe, some recent approaches have combined magnetic tweezers with total internal reflection fluorescence microscopy. In this situation, a typical force probe is a polymer microsphere containing two types of optically active components: a pure absorber (magnetic nanoparticles for providing the pulling force) and a luminophore (semiconducting nanoparticles or organic dyes for fluorescent imaging). To assess the system's capability fully with regard to tracking the position of the force probe with subnanometer accuracy, we developed a body-of-revolution formulation of the method of auxiliary sources (BOR-MAS) to simulate the absorption, scattering, and fluorescence of microscopic spheres in an evanescent electromagnetic field. The theoretical formulation uses the axial symmetry of the system to reduce the dimensionality of the modeling problem and produces excellent agreement with the reported experimental data on forward scattering intensity. Using the BOR-MAS numerical model, we investigated the probe detection sensitivity for a high numerical aperture objective. The analysis of both backscattering and fluorescence observation modes shows that the total intensity of the bead image decays exponentially with the distance from the surface (or the length of a biomolecule). Our investigations demonstrate that the decay lengths of observable optical power are smaller than the penetration depth of the unperturbed excitation evanescent wave. In addition, our numerical modeling results illustrate that the expected sensitivity for the decay length changes with the angle of incidence, tracking the theoretical penetration depth for a two-media model, and is sensitive to the bead size. The BOR-MAS methodology developed in this work for near-field modeling of bead-tracking experiments fully describes the fundamental photonic response of microscopic BOR probes at the subwavelength level and can be used for future improvements in the design of these probes or in the setup of bead-tracking experiments. PMID:20486724

Bijamov, Alex; Shubitidze, Fridon; Oliver, Piercen M; Vezenov, Dmitri V

2010-07-20

58

Optical Response of Magnetic-Fluorescent Microspheres Used for Force Spectroscopy in the Evanescent Field  

PubMed Central

Force spectroscopy based on magnetic tweezers is a powerful technique to manipulate single biomolecules and study their interactions. The resolution in a magnetic probe displacement, however, needs to be commensurate with molecular sizes. To achieve the desirable sensitivity in tracking displacements of the magnetic probe, some recent approaches have combined magnetic tweezers with total internal reflection fluorescence microscopy. In this situation, a typical force probe is a polymer microsphere containing two types of optically active components – a pure absorber (magnetic nanoparticles for providing the pulling force) and a luminophore (semiconducting nanoparticles or organic dyes for fluorescent imaging). In order to fully assess the system’s capability for tracking the position of the force probe with sub-nanometer accuracy, we developed a body-of-revolution formulation of the method of auxiliary sources (BOR-MAS) to simulate absorption, scattering, and fluorescence of microscopic spheres in an evanescent electromagnetic field. The theoretical formulation uses the axial symmetry of the system to reduce the dimensionality of the modeling problem and produces excellent agreement with the reported experimental data on forward scattering intensity. Using the BOR-MAS numerical model, we investigated the probe detection sensitivity for a high numerical aperture objective. The analysis of both backscattering and fluorescence observation modes shows that the total intensity of the bead image decays exponentially with the distance from the surface (or the length of a biomolecule). Our investigations demonstrate that the decay lengths of observable optical power are smaller than the penetration depth of the unperturbed excitation evanescent wave. In addition, our numerical modeling results illustrate that the expected sensitivity for the decay length changes with the incident angle, tracking the theoretical penetration depth for a two-media model, and is sensitive to the bead size. The BOR-MAS methodology developed in this work for near field modeling of bead tracking experiments fully describes the fundamental photonic response of microscopic BOR probes at the sub-wavelength level and can be used for future improvements in the design of these probes or in the setup of bead tracking experiments.

Bijamov, Alex; Shubitidze, Fridon; Oliver, Piercen M.; Vezenov, Dmitri V.

2010-01-01

59

Molecule formation in optical lattice wells by resonantly modulated magnetic fields  

SciTech Connect

We present a theoretical model for formation of molecules in an optical lattice well where a resonant coupling of atomic and molecular states is provided by small oscillations of a magnetic field in the vicinity of a Feshbach resonance. As opposed to an adiabatic sweep over the full resonance, this provides a coherent coupling with a frequency that can be tuned to meet resonance conditions in the system. The effective Rabi frequencies for this coupling are calculated and simulations show perfect Rabi oscillations. Robust production of molecules with an adiabatic sweep of the modulation frequency is demonstrated. For very large oscillation amplitudes, the Rabi oscillations are distorted but still effective and fast association is possible.

Bertelsen, Jesper Fevre; Moelmer, Klaus [Danish National Research Foundation Center for Quantum Optics, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

2006-01-15

60

Evolution of small-scale magnetic fields from combined adaptive optics and phase-diverse speckle imaging  

Microsoft Academic Search

We have obtained movies of the photospheric magnetic field at a sustained resolution of 0.2 arcsec by combining the adaptive optics system at the Dunn Solar Telescope with the Zurich Imaging Polarimeter I (ZIMPOL) and processing the data with Phase-Diverse Speckle Imaging and speckle deconvolution. The adaptive optics was correcting the low-order aberrations with an update rate of about 1.5

C. U. Keller; T. R. Rimmele; R. G. Paxman; J. H. Seldin; D. Carrara; K. Gleichman

2000-01-01

61

Fermi surface study of organic conductors using a magneto-optical measurement under high magnetic fields  

NASA Astrophysics Data System (ADS)

Magneto-optical measurements have been performed in organic conductors ?''-(BEDT-TTF)2CsCd(SCN)4 and ?-(BETS)2FeCl4. Although the zero magnetic field ground state of ?''-(BEDT-TTF)2CsCd(SCN)4is considered as the density wave state, periodic orbit resonances (POR's) attributed to quasi-one-dimensional (Q1D) and quasi-two-dimensional (Q2D) Fermi surfaces (FS's) have been observed above 6 T. The existence of these FS's are predicted by the band calculation based on room temperature lattice parameters. This result may suggest the destruction of the density wave state at 6 T, and the primal metallic state revives in the high field phase above 6 T. In the case of ?-(BETS)2FeCl4, large changes of the transmission intensity of electromagnetic waves around 10 T, which correspond to the insulator-metal transition, have been observed. However, no POR-like resonance has been observed. This may be due to the restriction of the observed frequency-field region.

Kimata, M.; Ohta, H.; Koyama, K.; Motokawa, M.; Kondo, R.; Kagoshima, S.; Tanaka, H.; Tokumoto, M.; Kobayashi, H.; Kobayashi, A.

2006-11-01

62

Experimental Investigation on Temperature Dependence of the Performance in a Magnetostrictive Fiber-Optic Interferometric Magnetic Field Sensor  

Microsoft Academic Search

This paper studies the temperature dependence of the performance in magnetostrictive fiber-optic Michelson interferometric magnetic field sensors. Experiments are carried out and the results show that the sensor system output, system sensitivity and transducer's mechanical resonant frequency are strongly affected by the ambient temperature. Fitted expressions are provided and compensation methods are demonstrated with experimental verification.

Xin Wang; Xinwan Li; Zhigang Du; Xiaoyang Wang; Jianping Chen

2009-01-01

63

Magnetic field interaction with guided light for detection of an active gaseous medium within an optical fiber.  

PubMed

We report a novel fiber-optic sensing architecture for the detection of paramagnetic gases. By interacting a modulated magnetic field with guided light within a microstructured optical fiber, it is possible to exploit Faraday Rotation Spectroscopy (FRS) within unprecedentedly small sample volumes. This approach, which utilizes magnetic circular birefringence and magnetic circular dichroism effects, is applied to a photonic bandgap fiber to detect molecular oxygen and operates at a wavelength of 762.309 nm. The optical fiber sensor has a 4.2 nL detection volume and 14.8 cm long sensing region. The observed FRS spectra are compared with a theoretical model that provides a first understanding of guided-mode FRS signals. This FRS guided-wave sensor offers the prospect of new compact sensing schemes. PMID:23389230

Englich, Florian V; Grabka, Michal; Lancaster, David G; Monro, Tanya M

2013-01-28

64

Detecting The Magnetic Field of the Transiting Exoplanet WASP-26b Through Near-UV and Optical Observations  

NASA Astrophysics Data System (ADS)

In November of 2011 WASP-26b was observed on the Steward Observatory 61” Kuiper Telescope using the Harris-R and Bessell-U filters to detect a possible magnetic field. It is suggested by Vidotto et. al. (2011), that it is possible to detect a magnetic field of a transiting exoplanet in the near-UV and optical bands by comparing asymmetries between the light curves. WASP-26b is a candidate for demonstrating this effect. Several other parameters to confirm and amend can be derived from the light curve including the planet’s mass, radius, density, surface gravity, distance, and orbital inclination.

Biddle, Lauren; Turner, J.; Smith, C.; Towner, A. P.; Walker-LaFollette, A.; Teske, J.

2013-01-01

65

Studying the reversal mode of the magnetization vector versus applied field angle using generalized magneto-optical ellipsometry  

SciTech Connect

The authors used the technique of vector Generalized Magneto-optical Ellipsometry to study the behavior of the magnetization vector of a 50 Co thin film as a function of external field magnitude and direction. With this method, which determines the both the direction and magnitude of the magnetization, averaged over the 1 mm incident laser beam, they were able to determine the relative contributions of magnetization rotation and domain formation to the reversal of M. The Co sample had a uniaxial in-plane anisotropy. The authors found that when the angle between the applied field and the easy axis was greater than {approximately} 40 degrees, the reversal occurred primarily by rotation of the magnetization, accompanied by a small reduction of the magnitude of M. In this angular region, the critical field-the field at which there is a large jump in the angle of M -- as a function of applied field angle followed a coherent rotation model. However, at applied field angles less than 40 degrees to the easy axis, they found a larger reduction in {vert_bar}M{vert_bar} occurring before and during the jump in the magnetization angle. The jump also occurred at fields much lower than those predicted by the coherent rotation model, indicating a reversal mode initiated by domain formation.

Pufall, M. R.; Berger, A.

1999-10-26

66

Optical soliton in dielectric fibers and self-organization of turbulence in plasmas in magnetic fields  

PubMed Central

One important discovery in the twentieth century physics is the natural formation of a coherent or a well-ordered structure in continuous media, in contrary to degradation of the state as predicted earlier from the second law of thermodynamics. Here nonlinearity plays the essential role in its process. The discovery of soliton, a localized stable wave in a nonlinear and dispersive medium and the self-organization of fluid turbulence are of the major examples. A soliton is formed primarily in one-dimensional medium where the dispersion and nonlinearity play the essential role. Here the temporal evolution can be described by an infinite dimensional Hamiltonian system that is integrable. While a self-organization appears in an infinite dimensional non-Hamiltonian (or dissipative) system where more than two conservative quantities exist in the limit of no dissipation. In this manuscript, by showing examples of the optical soliton in dielectric fibers and self-organization of turbulence in a toroidal plasma in a magnetic field, we demonstrate these interesting discoveries. The manuscript is intended to describe these discoveries more on philosophical basis with some sacrifice on mathematical details so that the idea is conveyed to those in the wide area of sciences.

Hasegawa, Akira

2009-01-01

67

Optical soliton in dielectric fibers and self-organization of turbulence in plasmas in magnetic fields.  

PubMed

One important discovery in the twentieth century physics is the natural formation of a coherent or a well-ordered structure in continuous media, in contrary to degradation of the state as predicted earlier from the second law of thermodynamics. Here nonlinearity plays the essential role in its process. The discovery of soliton, a localized stable wave in a nonlinear and dispersive medium and the self-organization of fluid turbulence are of the major examples. A soliton is formed primarily in one-dimensional medium where the dispersion and nonlinearity play the essential role. Here the temporal evolution can be described by an infinite dimensional Hamiltonian system that is integrable. While a self-organization appears in an infinite dimensional non-Hamiltonian (or dissipative) system where more than two conservative quantities exist in the limit of no dissipation. In this manuscript, by showing examples of the optical soliton in dielectric fibers and self-organization of turbulence in a toroidal plasma in a magnetic field, we demonstrate these interesting discoveries. The manuscript is intended to describe these discoveries more on philosophical basis with some sacrifice on mathematical details so that the idea is conveyed to those in the wide area of sciences. PMID:19145067

Hasegawa, Akira

2009-01-01

68

Investigating Electric Field Control of Magnetism with Neutron Scattering, Nonlinear Optics and Synchrotron X-Ray Spectromicroscopy  

NASA Astrophysics Data System (ADS)

This paper discusses recent efforts to control magnetism with electric fields in single and multilayer oxides, which has great potential to improve a variety of technological endeavors, such as magnetic sensing and magnetoelectric (ME) logic. The importance of electrical control of magnetism is followed by a discussion of multiferroics and MEs, which are the leading contenders for this task. The focus of this paper is on complementary methods in understanding the ME coupling, an essential step to electrical control of magnetism. Neutron scattering, nonlinear optics and X-ray spectromicroscopy are addressed in providing key parameters in the study of ME coupling. While primarily direct (single-phase multiferroics) ME materials are used as examples, the techniques discussed are also valuable to the study of indirect (e.g., multilayers and pillars) magnetoelectrics. We conclude with a summary of the field and future directions.

Holcomb, M. B.; Polisetty, S.; Rodríguez, A. Fraile; Gopalan, V.; Ramesh, R.

69

Errors of solar magnetographs in large-scale magnetic field observations, as caused by field-of-view effects of electro-optical polarization analyzers.  

NASA Astrophysics Data System (ADS)

The authors examine some aspects of the problem related to the production of "spurious" (not associated with the magnetic field) signals of solar magnetographs (the zero-level problem), caused by adjustment errors of the components of electro-optical polarization analyzers and/or by aperture nonuniformities of brightness. It is pointed out that these field-of-view effects are of important significance for observations of large-scale solar magnetic fields. Numerical estimates are made of the errors, as applied mainly to the STOP telescope at the Sayan Observatory.

Demidov, M. L.; Zhigalov, V. V.

70

Fiber-optic in-line magnetic field sensor based on the magnetic fluid and multimode interference effects  

NASA Astrophysics Data System (ADS)

A compact magnetic field sensor has been proposed based on multimode interference effects. It consists of typical multimode interferometer (MMI) immersed into the magnetic fluid (MF) which is formed by a section of square no-core fiber (NCF) spliced between two single-mode fibers. The transmission spectral characteristics of this MMI have been analyzed, and the spectral magnetic response of the proposed sensor has been investigated by immersing the NCF into the MF environment. The transmission response of the interference maxima exhibits a sensitivity of -0.01939 dB/Oe in the relatively linear range. Due to its low cost and compactness, this sensor would find potential applications in the measurement of magnetic field.

Lin, Wei; Miao, Yinping; Zhang, Hao; Liu, Bo; Liu, Yange; Song, Binbin

2013-10-01

71

Orthogonality parameter associated with a magnetic field gradient for single-site addressing in a 1D optical lattice  

NASA Astrophysics Data System (ADS)

We investigate the possibility of detecting atoms in a 1D optical lattice with the nearest-site resolution by using a magnetic resonance technique. A superimposed magnetic field gradient introduces a position-dependent Zeeman shift to label each site. Among the line-broadening mechanisms, we focus on sideband transitions between the motional states of the lower and the upper hyperfine levels. In addition to the sidebands of the axial motion induced by the field gradient itself, we consider those of the transverse motion induced by field misalignments with respect to the optical lattice. Parameters that determine the sideband strengths are identified in a manner analogous to the Lamb-Dicke parameter. The analysis shows that it is advantageous to use light and cold atoms in a deep optical potential well. An explicit expression for the lineshape of the hyperfine transition is obtained. We use it to calculate lineshapes for a cesium and a lithium atom in a typical optical lattice as well as those for the previously reported experiments using cesium atoms.

Choi, Jai-Min; Kim, Huidong; Han, Hyok Sang; Cho, Donghyun

2013-08-01

72

Development of an alternating magnetic-field-assisted finishing process for microelectromechanical systems micropore x-ray optics.  

PubMed

X-ray astronomy research is often limited by the size, weight, complexity, and cost of functioning x-ray optics. Micropore optics promises an economical alternative to traditional (e.g., glass or foil) x-ray optics; however, many manufacturing difficulties prevent micropore optics from being a viable solution. Ezoe et al. introduced microelectromechanical systems (MEMS) micropore optics having curvilinear micropores in 2008. Made by either deep reactive ion etching or x-ray lithography, electroforming, and molding (LIGA), MEMS micropore optics suffer from high micropore sidewall roughness (10-30nmrms) which, by current standards, cannot be improved. In this research, a new alternating magnetic-field-assisted finishing process was developed using a mixture of ferrofluid and microscale abrasive slurry. A machine was built, and a set of working process parameters including alternating frequency, abrasive size, and polishing time was selected. A polishing experiment on a LIGA-fabricated MEMS micropore optic was performed, and a change in micropore sidewall roughness of 9.3+/-2.5nmrms to 5.7+/-0.7nmrms was measured. An improvement in x-ray reflectance was also seen. This research shows the feasibility and confirms the effects of this new polishing process on MEMS micropore optics. PMID:20563204

Riveros, Raul E; Yamaguchi, Hitomi; Mitsuishi, Ikuyuki; Takagi, Utako; Ezoe, Yuichiro; Kato, Fumiki; Sugiyama, Susumu; Yamasaki, Noriko; Mitsuda, Kazuhisa

2010-06-20

73

Development of an alternating magnetic-field-assisted finishing process for microelectromechanical systems micropore x-ray optics  

SciTech Connect

X-ray astronomy research is often limited by the size, weight, complexity, and cost of functioning x-ray optics. Micropore optics promises an economical alternative to traditional (e.g., glass or foil) x-ray optics; however, many manufacturing difficulties prevent micropore optics from being a viable solution. Ezoe et al. introduced microelectromechanical systems (MEMS) micropore optics having curvilinear micropores in 2008. Made by either deep reactive ion etching or x-ray lithography, electroforming, and molding (LIGA), MEMS micropore optics suffer from high micropore sidewall roughness (10-30nmrms) which, by current standards, cannot be improved. In this research, a new alternating magnetic-field-assisted finishing process was developed using a mixture of ferrofluid and microscale abrasive slurry. A machine was built, and a set of working process parameters including alternating frequency, abrasive size, and polishing time was selected. A polishing experiment on a LIGA-fabricated MEMS micropore optic was performed, and a change in micropore sidewall roughness of 9.3{+-}2.5nmrms to 5.7{+-}0.7nmrms was measured. An improvement in x-ray reflectance was also seen. This research shows the feasibility and confirms the effects of this new polishing process on MEMS micropore optics.

Riveros, Raul E.; Yamaguchi, Hitomi; Mitsuishi, Ikuyuki; Takagi, Utako; Ezoe, Yuichiro; Kato, Fumiki; Sugiyama, Susumu; Yamasaki, Noriko; Mitsuda, Kazuhisa

2010-06-20

74

A study on magnetic near-field measurements above a patch antenna using an optical waveguide probe with a loop element  

Microsoft Academic Search

We developed a magnetic field probe consisting of a LiNbO3 optical waveguide modulator and a loop antenna element for accurate magnetic near-field measurements in the gigahertz range. We confirmed the probe invasiveness by measuring magnetic field distributions above a patch antenna operating at 2.49 GHz using the probe. Then we compared those measured results with those for shielded loop probes.

Masanon Takahashi; Huoyasu Ota; Ken Ichi Arai; R. Sato

2004-01-01

75

Magnetic fields in astrophysics  

Microsoft Academic Search

The evidence of cosmic magnetism is examined, taking into account the Zeeman effect, beats in atomic transitions, the Hanle effect, Faraday rotation, gyro-lines, and the strength and scale of magnetic fields in astrophysics. The origin of magnetic fields is considered along with dynamos, the conditions for magnetic field generation, the topology of flows, magnetic fields in stationary flows, kinematic turbulent

Ia. B. Zeldovich; A. A. Ruzmaikin; D. D. Sokolov

1983-01-01

76

Imaging of the magnetic field structure in megagauss plasmas by combining pulsed polarimetry with an optical Kerr effect shutter technique  

SciTech Connect

Pulsed polarimetry in combination with a high speed photographic technique based on the optical Kerr effect is described. The backscatter in a pulsed polarimeter is directed through a scattering cell and photographed using an {approx}1 ps shutter, essentially freezing the intensity pattern. The image provides both the local electron density and magnetic field distributions along and transverse to the laser sightline. Submillimeter spatial resolution is possible for probing wavelengths in the visible due to the high densities and strong optical activity. Pulsed polarimetry is thereby extended to centimeter-sized plasmas with n{sub e}>10{sup 19}-10{sup 20} cm{sup -3} and B>20-100 T (MG) produced by multiterawatt, multimega-ampere electrical drivers, wire Z pinches, and liner imploded magnetized plasmas.

Smith, R. J. [University of Washington, Box 352250, Seattle, Washington 98195 (United States)

2010-10-15

77

Imaging of the magnetic field structure in megagauss plasmas by combining pulsed polarimetry with an optical Kerr effect shutter technique.  

PubMed

Pulsed polarimetry in combination with a high speed photographic technique based on the optical Kerr effect is described. The backscatter in a pulsed polarimeter is directed through a scattering cell and photographed using an ?1?ps shutter, essentially freezing the intensity pattern. The image provides both the local electron density and magnetic field distributions along and transverse to the laser sightline. Submillimeter spatial resolution is possible for probing wavelengths in the visible due to the high densities and strong optical activity. Pulsed polarimetry is thereby extended to centimeter-sized plasmas with n(e)>10(19)-10(20)?cm(-3) and B>20-100?T (MG) produced by multiterawatt, multimega-ampere electrical drivers, wire Z pinches, and liner imploded magnetized plasmas. PMID:21033885

Smith, R J

2010-10-01

78

Time-resolved, optically detected NMR of fluids at high magnetic field  

NASA Astrophysics Data System (ADS)

We report on the use of optical Faraday rotation to monitor the nuclear-spin signal in a set of model 19F- and 1H-rich fluids. Our approach integrates optical detection with high-field, pulsed NMR so as to record the time-resolved evolution of nuclear-spins after rf excitation. Comparison of chemical-shift-resolved resonances allows us to set order-of-magnitude constrains on the relative amplitudes of hyperfine coupling constants for different bonding geometries. When evaluated against coil induction, the present detection modality suffers from poorer sensitivity, but improvement could be attained via multipass schemes. Because illumination is off-resonant i.e., the medium is optically transparent, this methodology could find extensions in a broad class of fluids and soft condensed matter systems.

Pagliero, Daniela; Dong, Wei; Sakellariou, Dimitris; Meriles, Carlos A.

2010-10-01

79

Degeneracy of Many-Body Quantum States in an Optical Lattice under a Uniform Magnetic Field  

SciTech Connect

We prove a theorem that shows the degeneracy of many-body states for particles in a periodic lattice and under a uniform magnetic field depends on the total particle number and the flux filling ratio. Noninteracting fermions and weakly interacting bosons are given as two examples. For the latter case, the phenomenon can also be physically understood in terms of destructive quantum interference of multiple symmetry-related tunneling paths between classical energy minima, which is reminiscent of the spin-parity effect discovered in magnetic molecular clusters. We also show that the quantum ground state of a mesoscopic number of bosons in this system is not a simple mean-field state but a fragmented state even for very weak interactions.

Zhang Jian; Jian Chaoming; Zhai Hui [Institute for Advanced Study, Tsinghua University, Beijing, 100084 (China); Ye Fei [College of Material Science and Optoelectronics Technology, Graduated University of Chinese Academy of Science, Beijing 100049 (China)

2010-10-08

80

Optical detection of NMR J-spectra at zero magnetic field  

Microsoft Academic Search

Scalar couplings of the form JI1·I2 between nuclei impart valuable information about molecular structure to nuclear magnetic-resonance spectra. Here we demonstrate direct detection of J-spectra due to both heteronuclear and homonuclear J-coupling in a zero-field environment where the Zeeman interaction is completely absent. We show that characteristic functional groups exhibit distinct spectra with straightforward interpretation for chemical identification. Detection is

M. P. Ledbetter; C. W. Crawford; A. Pines; D. E. Wemmer; S. Knappe; J. Kitching; D. Budker

2009-01-01

81

Magnetic Fields Matter  

NSDL National Science Digital Library

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,

82

Optical polarimetry toward the Pipe nebula: revealing the importance of the magnetic field  

NASA Astrophysics Data System (ADS)

Context: Magnetic fields are proposed to play an important role in the formation and support of self-gravitating clouds and the formation and evolution of protostars in such clouds. Aims: We attempt to understand more precisely how the Pipe nebula is affected by the magnetic field. Methods: We use R-band linear polarimetry collected for about 12 000 stars in 46 fields with lines of sight toward the Pipe nebula to investigate the properties of the polarization across this dark cloud complex. Results: Mean polarization vectors show that the magnetic field is locally perpendicular to the large filamentary structure of the Pipe nebula (the “stem”), indicating that the global collapse may have been driven by ambipolar diffusion. The polarization properties clearly change along the Pipe nebula. The northwestern end of the nebula (B59 region) is found to have a low degree of polarization and high dispersion in polarization position angle, while at the other extreme of the cloud (the “bowl”) we found mean degrees of polarization as high as ?15% and a low dispersion in polarization position angle. The plane of the sky magnetic field strength was estimated to vary from about 17 ?G in the B59 region to about 65 ?G in the bowl. Conclusions: We propose that three distinct regions exist, which may be related to different evolutionary stages of the cloud; this idea is supported by both the polarization properties across the Pipe and the estimated mass-to-flux ratio that varies between approximately super-critical toward the B59 region and sub-critical inside the bowl. The three regions that we identify are: the B59 region, which is currently forming stars; the stem, which appears to be at an earlier stage of star formation where material has been through a collapsing phase but not yet given birth to stars; and the bowl, which represents the earliest stage of the cloud in which the collapsing phase and cloud fragmentation has already started. Based on observations collected at Observatório do Pico dos Dias, operated by Laboratório Nacional de Astrofísica (LNA/MCT, Brazil).

Alves, F. O.; Franco, G. A. P.; Girart, J. M.

2008-08-01

83

Magnetic field line Hamiltonian  

SciTech Connect

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

Boozer, A.H.

1985-02-01

84

Linear and nonlinear optical absorption coefficients and refractive index changes in modulation-doped quantum wells: Effects of the magnetic field and hydrostatic pressure  

NASA Astrophysics Data System (ADS)

In this study, the linear, the third-order nonlinear and total optical absorption coefficients and refractive index changes of a modulation-doped GaAs/AlxGaAs quantum well are investigated numerically. In the effective-mass approximation, the electronic structure of modulation-doped quantum well is calculated by solving the Schrödinger and Poisson equations self-consistently. Optical properties are obtained using the compact density matrix approach. The effects of structure parameters, the applied magnetic field and the hydrostatic pressure on the optical properties of the modulation-doped quantum well are studied. Results show that the resonant peaks shift toward the higher (lower) energies with the increase in the magnetic field (pressure). The magnitude of the resonant peaks of the optical properties decreases with the increasing magnetic field or pressure.

Nazari, M.; Karimi, M. J.; Keshavarz, A.

2013-11-01

85

An approach to improving the signal-to-optical-noise ratio of pulsed magnetic field photonic sensors  

Microsoft Academic Search

During last years, interest in pulsed magnetic field sensors has widely increased. In fact, magnetic field measurement has a critical part in various scientific and technical areas. In order to research on pulsed magnetic field characteristic and corresponding measuring and defending means, a sensor with high immunity to electrical noise, high sensitivity, high accuracy and wide dynamic range is needed.

Jiang-Ping Wang; Yu-Quan Li

2008-01-01

86

Coherent Multifrequency Optical Fields  

NASA Astrophysics Data System (ADS)

An analysis of the generalized coherence of multifrequency optical fields is given, both in terms of observable quantities (coherence functions) and in terms of field quantities (analytical signal and amplitude spectral density of the field). The spectral structure of the generalized coherence function for a widespread class of multifrequency optical fields is given. Experimental results obtained by interferometrical investigation of the generalized coherence of such fields are presented.

Tudor, Tiberiu

2004-01-01

87

Magnetic-field control of photon echo from the electron-trion system in a CdTe quantum well: shuffling coherence between optically accessible and inaccessible states.  

PubMed

We report on magnetic field-induced oscillations of the photon echo signal from negatively charged excitons in a CdTe/(Cd,Mg)Te semiconductor quantum well. The oscillatory signal is due to Larmor precession of the electron spin about a transverse magnetic field and depends sensitively on the polarization configuration of the exciting and refocusing pulses. The echo amplitude can be fully tuned from the maximum down to zero depending on the time delay between the two pulses and the magnetic-field strength. The results are explained in terms of the optical Bloch equations accounting for the spin level structure of electrons and trions. PMID:23102368

Langer, L; Poltavtsev, S V; Yugova, I A; Yakovlev, D R; Karczewski, G; Wojtowicz, T; Kossut, J; Akimov, I A; Bayer, M

2012-10-12

88

Solar Magnetic Field  

NASA Astrophysics Data System (ADS)

Electrical currents flowing in the solar plasma generate a magnetic field, which is detected in the SOLAR ATMOSPHERE by spectroscopic and polarization measurements (SOLAR MAGNETIC FIELD: INFERENCE BY POLARIMETRY). The SOLAR WIND carries the magnetic field into interplanetary space where it can be measured directly by instruments on space probes....

Schüssler, M.; Murdin, P.

2000-11-01

89

The Magnetic Field  

NSDL National Science Digital Library

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

Barker, Jeffrey

90

Magnetic Field Problem  

NSDL National Science Digital Library

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

91

Electro- and magneto-optical measurements of electric field strength in magnetic colloids based on liquid dielectrics  

NASA Astrophysics Data System (ADS)

The distribution of the electric field strength in liquid dielectrics containing colloidal magnetite particles was investigated based on the data of electro- and magneto-optical experiments. It is shown that the field distribution between plane-parallel electrodes is nonuniform. The dependences of the field enhancement in the near-electrode region on the temperature and average field strength in the cell are determined. The parameters of the near-electrode space charge are calculated based on the data of optical experiments.

Erin, K. V.

2011-07-01

92

Detection of Low-Intensity Magnetic Fields with a Magnetostrictive Fiber Optic Sensor.  

National Technical Information Service (NTIS)

This thesis presents the fabrication, evaluation, and performance results of a magnetostrictive fiber optic sensor. The sensor was fabricated using a Mach-Zehnder interferometric arrangement. Four classes of sensing arms were fabricate as: ribbons, cylind...

L. L. Picon

1993-01-01

93

Enhancing the volume and the optical quality of hen egg-white lysozyme crystals by coupling the salt concentration gradient crystallization method with a magnetic field.  

PubMed

The effect of coupling the salt concentration gradient crystallization method with the use of the paramagnetic salt MnCl(2) and a magnetic field is reported. The use of a simple magnetic device is proposed to have a significant effect on hen egg-white lysozyme crystal growth. Large single crystals greater than 10?mm(3) in volume with optical perfection were consistently obtained in this study. PMID:22997475

Magay, Elena; Cho, Sang Jin; Kim, Shin Ae

2012-09-13

94

Magnetic Fields in Galaxies  

NASA Astrophysics Data System (ADS)

Most of the visible matter in the Universe is ionized so that cosmic magnetic fields are quite easy to generate and, due to the lack of magnetic monopoles, hard to destroy. Magnetic fields have been measured in or around practically all celestial objects, either by in situ measurements of spacecrafts or by the electromagnetic radiation of embedded cosmic rays, gas, or dust. The Earth, the Sun, solar planets, stars, pulsars, the Milky Way, nearby galaxies, more distant (radio) galaxies, quasars, and even intergalactic space in clusters of galaxies have significant magnetic fields, and even larger volumes of the Universe may be permeated by "dark" magnetic fields. Information on cosmic magnetic fields has increased enormously as the result of the rapid development of observational methods, especially in radio astronomy. In the Milky Way, a wealth of magnetic phenomena was discovered, which are only partly related to objects visible in other spectral ranges. The large-scale structure of the Milky Way's magnetic field is still under debate. The available data for external galaxies can well be explained by field amplification and ordering via the dynamo mechanism. The measured field strengths and the similarity of field patterns and flow patterns of the diffuse ionized gas give strong indication that galactic magnetic fields are dynamically important. They may affect the formation of spiral arms, outflows, and the general evolution of galaxies. In spite of our increasing knowledge on magnetic fields, many important questions on the origin and evolution of magnetic fields, their first occurrence in young galaxies, or the existence of large-scale intergalactic fields remained unanswered. The present upgrades of existing instruments and several planned radio astronomy projects have defined cosmic magnetism as one of their key science projects.

Beck, Rainer; Wielebinski, Richard

95

Intergalactic magnetic fields  

Microsoft Academic Search

There is no observational support to the hypothesis of the most large-scale homogeneous magnetic field in the Universe. The best upper limit is given by interpretation of the Faraday rotation from the extragalactic radio sources. However the magnetic fields can be generated in the clusters of galaxies by a turbulence in the wakes of moving galaxies. These fields have an

A. A. Ruzmajkin

1991-01-01

96

Magnetic Field Example 1  

NSDL National Science Digital Library

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

Christian, Wolfgang; Belloni, Mario

2008-02-19

97

Magnetic Effects in Integrated Optics Effets Magnetiques en Optique Integree.  

National Technical Information Service (NTIS)

Nonreciprocal transmission equipment based on integrated optics was built and studied in order to better define the interface between a magnetic field and optical signals. Results led to the construction and testing of rectangular magneto-optical waveguid...

G. Hepner J. P. Castera

1977-01-01

98

Optical fiber system for the high resolution resonant Raman spectroscopy at 3He temperature in a high magnetic field  

NASA Astrophysics Data System (ADS)

A high-resolution resonant Raman spectroscopy system has been developed by using optical fibers and applied to the spin-flip Raman scattering experiment in CdZnTe/ CdZnMnTe quantum wells at 3He temperature in a high magnetic field up to 14 T. Excitation light from an external cavity laser diode or Ti:sapphire laser was introduced into the liquid 3He chamber by using polarization maintain fiber, and was incident on the sample at the angle of 45 degree through a GRIN collimation lens and a prism to deflect the reflected light from the luminescence/scattering detection pass. Luminescence and scattered light were collected efficiently into the bundled multi-mode fibers through a high NA objective lens and introduced into the slit of a 1.26 m single grating spectrometer equipped with a multi-channel CCD detector and a photon counter. The fiber system provides a convenient way to investigate the spin dynamics in an ideal environments; ultra-low temperature and radiation-free condition. Furthermore, the system is more sensitive than the conventional system utilizing a cryostat with the optical windows where multiple Fresnel loss and the small numerical aperture degrade the sensitivity.

Arahara, K.; Koyama, T.; Oto, K.; Muro, K.; Takeyama, S.; Karczewski, G.; Wojutowics, T.; Kossut, J.

2006-11-01

99

The Magnetic Field  

NSDL National Science Digital Library

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

Universe, Windows T.

1997-12-03

100

Optical magnetic imaging of living cells.  

PubMed

Magnetic imaging is a powerful tool for probing biological and physical systems. However, existing techniques either have poor spatial resolution compared to optical microscopy and are hence not generally applicable to imaging of sub-cellular structure (for example, magnetic resonance imaging), or entail operating conditions that preclude application to living biological samples while providing submicrometre resolution (for example, scanning superconducting quantum interference device microscopy, electron holography and magnetic resonance force microscopy). Here we demonstrate magnetic imaging of living cells (magnetotactic bacteria) under ambient laboratory conditions and with sub-cellular spatial resolution (400?nanometres), using an optically detected magnetic field imaging array consisting of a nanometre-scale layer of nitrogen-vacancy colour centres implanted at the surface of a diamond chip. With the bacteria placed on the diamond surface, we optically probe the nitrogen-vacancy quantum spin states and rapidly reconstruct images of the vector components of the magnetic field created by chains of magnetic nanoparticles (magnetosomes) produced in the bacteria. We also spatially correlate these magnetic field maps with optical images acquired in the same apparatus. Wide-field microscopy allows parallel optical and magnetic imaging of multiple cells in a population with submicrometre resolution and a field of view in excess of 100?micrometres. Scanning electron microscope images of the bacteria confirm that the correlated optical and magnetic images can be used to locate and characterize the magnetosomes in each bacterium. Our results provide a new capability for imaging bio-magnetic structures in living cells under ambient conditions with high spatial resolution, and will enable the mapping of a wide range of magnetic signals within cells and cellular networks. PMID:23619694

Le Sage, D; Arai, K; Glenn, D R; DeVience, S J; Pham, L M; Rahn-Lee, L; Lukin, M D; Yacoby, A; Komeili, A; Walsworth, R L

2013-04-25

101

Optical magnetic imaging of living cells  

PubMed Central

Magnetic imaging is a powerful tool for probing biological and physical systems. However, existing techniques either have poor spatial resolution compared to optical microscopy and are hence not generally applicable to imaging of sub-cellular structure (e.g., magnetic resonance imaging [MRI]1), or entail operating conditions that preclude application to living biological samples while providing sub-micron resolution (e.g., scanning superconducting quantum interference device [SQUID] microscopy2, electron holography3, and magnetic resonance force microscopy [MRFM]4). Here we demonstrate magnetic imaging of living cells (magnetotactic bacteria) under ambient laboratory conditions and with sub-cellular spatial resolution (400 nm), using an optically-detected magnetic field imaging array consisting of a nanoscale layer of nitrogen-vacancy (NV) colour centres implanted at the surface of a diamond chip. With the bacteria placed on the diamond surface, we optically probe the NV quantum spin states and rapidly reconstruct images of the vector components of the magnetic field created by chains of magnetic nanoparticles (magnetosomes) produced in the bacteria, and spatially correlate these magnetic field maps with optical images acquired in the same apparatus. Wide-field sCMOS acquisition allows parallel optical and magnetic imaging of multiple cells in a population with sub-micron resolution and >100 micron field-of-view. Scanning electron microscope (SEM) images of the bacteria confirm that the correlated optical and magnetic images can be used to locate and characterize the magnetosomes in each bacterium. The results provide a new capability for imaging bio-magnetic structures in living cells under ambient conditions with high spatial resolution, and will enable the mapping of a wide range of magnetic signals within cells and cellular networks5, 6.

Le Sage, D.; Arai, K.; Glenn, D. R.; DeVience, S. J.; Pham, L. M.; Rahn-Lee, L.; Lukin, M. D.; Yacoby, A.; Komeili, A.; Walsworth, R. L.

2013-01-01

102

Femtosecond laser inscribed Bragg sensor in Terfenol-D coated optical fibre with ablated microslot for the detection of static magnetic fields  

Microsoft Academic Search

A novel device for the detection and characterisation of static magnetic fields is presented. It consists of a femtosecond laser inscribed fibre Bragg grating (FBG) that is incorporated into an optical fibre with a femtosecond laser micromachined slot. The symmetry of the fibre is broken by the micro-slot, producing non-uniform strain across the fibre cross section. The sensing region is

G. N. Smith; T. Allsop; K. Kalli; C. Koutsides; R. Neal; K. Sugden; P. Culverhouse; I. Bennion

2011-01-01

103

Melatonin and magnetic fields.  

PubMed

There is public health concern raised by epidemiological studies indicating that extremely low frequency electric and magnetic fields generated by electric power distribution systems in the environment may be hazardous. Possible carcinogenic effects of magnetic field in combination with suggested oncostatic action of melatonin lead to the hypothesis that the primary effects of electric and magnetic fields exposure is a reduction of melatonin synthesis which, in turn, may promote cancer growth. In this review the data on the influence of magnetic fields on melatonin synthesis, both in the animals and humans, are briefly presented and discussed. PMID:12019358

Karasek, Michal; Lerchl, Alexander

2002-04-01

104

Solar Magnetic and Velocity Field Measurement System for Spacelab 2: The Solar Optical Universal Polarimeter (SOUP).  

National Technical Information Service (NTIS)

The Solar Optical Universal Polarimeter (SOUP) flew on the shuttle mission Spacelab 2 (STS-51F) in August, 1985, and collected historic solar observations. SOUP is the only solar telescope on either a spacecraft or balloon which has delivered long sequenc...

T. D. Tarbell A. M. Title

1992-01-01

105

Magnetic field generator  

DOEpatents

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

Krienin, Frank (Shoreham, NY)

1990-01-01

106

On Cosmic Magnetic Fields  

NASA Astrophysics Data System (ADS)

Magnetic fields are present in all astrophysical media. However, many models and interpretations of observations often ignore them, because magnetic fields are difficult to handle and because they produce complicated morphological features. Here we will comment on the basic intuitive properties, which even if not completely true, provide a first guiding insight on the physics of a particular astrophysical problem. These magnetic properties are not mathematically demonstrated here. How magnetic fields evolve and how they introduce dynamical effects are considered, also including a short comment on General Relativity Magnetohydrodynamics. In a second part we consider some audacious and speculative matters. They are answers to three questions: a) How draw a cube without lifting the pencil from the paper so that when the pen passes through the same side do in the same direction? B) Are MILAGRO anisotropies miraculous? C) Do cosmic magnetic lenses exist?. The last two questions deal with issues related with the interplay between magnetic fields and cosmic ray propagation.

Florido, E.; Battaner, E.

2010-12-01

107

Magnetic fields at Uranus  

Microsoft Academic Search

The conclusions drawn regarding the structure, behavior and composition of the Uranian magnetic field and magnetosphere as revealed by Voyager 2 data are summarized. The planet had a bipolar magnetotail and a bow shock wave which was observed 23.7 Uranus radii (UR) upstream and a magnetopause at 18.0 UR. The magnetic field observed can be represented by a dipole offset

N. F. Ness; M. H. Acuna; K. W. Behannon; L. F. Burlaga; J. E. P. Connerney; R. P. Lepping

1986-01-01

108

THE INTERPLANETARY MAGNETIC FIELD  

Microsoft Academic Search

A new analysis of magnetic and concurrent plasma data collected from the ; space probes Pionecr 5, Explorer 10, and Mariner 2 yields a new model of the ; interplanetary magnetic field. It is hypothesized that the observed ; interplanetary field F\\/sub i\\/ is due to motion of the magnetometer relative to a ; negatively charged rotating sun from which

V. A. BAILEY

1963-01-01

109

Cosmic Magnetic Fields  

Microsoft Academic Search

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

Elisabete M. de Gouveia Dal Pino; Dal Pino

2006-01-01

110

Development of an electro-optic step-by-step sampling system for IC's close electro-magnetic field measurement  

Microsoft Academic Search

In this work we aim to realize a step-by-step electro-optical probe which exploits the linear (Pockels) electro-optic effect to survey the electromagnetic field on the surface of RF integrated circuits. This probe measures the variation of light polarization induced by a lithium niobate crystal immersed in the electric field provided by the DUT. The measurements will demonstrate the main features

Lucio Rossi; G. Breglio; A. Irace; P. Spirito

2006-01-01

111

The Earth's Magnetic Field  

NSDL National Science Digital Library

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

112

Transduction of the Spin State Variable Between the Electron and Optical Polarization at Zero Magnetic Field.  

National Technical Information Service (NTIS)

A New Spin on Electronics: Utilizing the spin degree of freedom of an electron in a semiconductor device is the basis for the emerging field of spin electronics, or spintronics. The idea is that spin-polarized electrons can be introduced into a semiconduc...

A. T. Hanbicki B. T. Jonker C. H. Li G. Kioseoglou O. M. Van't Erve

2007-01-01

113

Magnetic field sensors and visualizers using magnetic photonic crystals  

NASA Astrophysics Data System (ADS)

Magneto-optical imaging is widely used to observe the domain patterns in magnetic materials, visualize defects in ferromagnetic objects, and measure the spatial distribution of stray magnetic fields. Optimized 1D magneto-photonic crystals enable a significant increase in the sensitivity of magneto-optical sensors. The properties of such devices based on the optimized reflection (doubled Faraday rotation) mode and the use of 1D magnetic photonic crystals as sensors are discussed. Experimental results of the fabrication and characterization of ferrite-garnet layers possessing uniaxial magnetic anisotropy are shown, and an optimized film structure suitable for magneto-optical imaging is proposed.

Vasiliev, Mikhail; Alameh, Kamal E.; Kotov, Viatcheslav

2008-06-01

114

The use of magnetic field effects on photosensitizer luminescence as a novel probe for optical monitoring of oxygen in photodynamic therapy  

NASA Astrophysics Data System (ADS)

The effect of a magnetic field on the steady-state and time-resolved optical emission of a custom fullerene-linked photosensitizer (PS) in liposome cell phantoms was studied at various oxygen concentrations (0.19-190 µM). Zeeman splitting of the triplet state and hyperfine coupling, which control intersystem crossing between singlet and triplet states, are altered in the presence of low magnetic fields (B < 320 mT), perturbing the luminescence intensity and lifetime as compared to the triplet state at B = 0. Measurements of the luminescence intensity and lifetime were performed using a time-domain apparatus integrated with a magnet. We propose that by probing magnet-affected optical emissions, one can monitor the state of oxygenation throughout the course of photodynamic therapy. Since the magnetic field effect (MFE) operates primarily by affecting the radical ion pairs related to type I photodynamic action, the enhancement or suppression of the MFE can be used as a measure of the dynamic equilibrium between the type I and II photodynamic pathways. The unique photo-initiated charge-transfer properties of the PS used in this study allow it to serve as both cytotoxic agent and oxygen probe that can provide in situ dosimetric information at close to real time.

Mermut, O.; Diamond, K. R.; Cormier, J.-F.; Gallant, P.; Hô, N.; Leclair, S.; Marois, J.-S.; Noiseux, I.; Morin, J.-F.; Patterson, M. S.; Vernon, M. L.

2009-01-01

115

The First Magnetic Fields  

NASA Astrophysics Data System (ADS)

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

Widrow, Lawrence M.; Ryu, Dongsu; Schleicher, Dominik R. G.; Subramanian, Kandaswamy; Tsagas, Christos G.; Treumann, Rudolf A.

2012-05-01

116

Magnetic Field Lines  

NSDL National Science Digital Library

This activity will introduce students to the idea of magnetic field lines--a concept they have probably encountered but may not fully grasp. Completing this activity and reading the corresponding background information should enable students to understand

Horton, Michael

2009-05-30

117

Magnetic field dosimeter development  

SciTech Connect

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

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

1980-09-01

118

Ultranarrow Optical Absorption and Two-Phonon Excitation Spectroscopy of Cu2O Paraexcitons in a High Magnetic Field  

Microsoft Academic Search

We show that in a magnetic field B the otherwise forbidden lowest exciton in Cu2O (paraexciton of Gamma2+ symmetry) gives rise to a narrow absorption line of 80 neV at a temperature of 1.2 K. The B2 dependence of the field-induced oscillator strength and the low energy shift DeltaE with increasing field strength are measured. From two-phonon excitation spectroscopy measurements

Jan Brandt; Dietmar Fröhlich; Christian Sandfort; Manfred Bayer; Heinrich Stolz; Nobuko Naka

2007-01-01

119

Magnetic field confinement for magnetically levitated vehicles  

SciTech Connect

A magnetically levitated vehicle adapted for movement along a guide way, comprising: a passenger compartment; first and second primary magnet means secured on the vehicle to produce a magnetic field having a magnetic flux density extending outward from the primary magnet means, to support the vehicle above and spaced from the guide way; and a plurality of confining magnets disposed on the vehicle to confine the magnetic flux extending outward from the primary magnet means and to reduce the strength of the primary magnetic field in the passenger compartment; wherein the primary magnet means has a capacity to produce a primary magnetic field having a maximum strength of at least 200 gauss in the passenger compartment, and the confining magnets maintain the strength of the primary magnetic field in the passenger compartment below 5 gauss.

Proise, M.

1993-05-25

120

Optical properties of magnetic and non-magnetic composites of ferrofluids  

Microsoft Academic Search

Composites consisting of magnetic and non-magnetic micronsize particles suspended in a ferrofluid (FF) constitute magnetorheological (MR) fluid. Structuring occurs in an applied magnetic field and can results in the solidification of the composites. A novel magneto-optical effect of extremum and inversion in sign with increasing applied magnetic field strength in this composite is observed. The field strengths at which the

Rajesh Patel; R. V. Upadhyay; R. V. Mehta

2006-01-01

121

Optical Auroral Observations at High Latitudes to Investigate Processes at the Foot of Magnetic Field Lines That Map Into the Interplanetary Medium  

NASA Astrophysics Data System (ADS)

At high magnetic latitudes the magnetic field lines, are open and they map from the ground into the interplanetary medium. Due to the larger offset between the geographic and geomagnetic poles in the Southern hemisphere the Antarctic Continent is especially suitable for making visible wavelength optical observations of the foot of such field lines. Near the Austral winter solstice the entire polar cap, the region of open field lines are in darkness. For many years optical observation had been conducted in the Antarctica, mostly at South Pole station, with focus on studying dayside auroral phenomena that may be associated with the reconnection process between the interplanetary and the Earth's field. Although a great deal has been learned from such ground based observations, satellite based global views especially those from the IMAGE satellite proton imager, that is quite blind to dayside solar produced luminosities, contributed significantly to our understanding of the global scale morphology of the high latitude regions. Ground based optical observatory arrays are still very useful for providing the small to medium scale view of the various phenomena and the development of such array of observatories in Antarctica are still being actively pursued. Although it is not its primary purpose, the ground based THEMIS array will also be on line in the near future and it will make observations of the nightside polar cap region. In the near future there will be several arrays in operation to study the region of field lines that map from the ground into the interplanetary medium.

Mende, S. B.

2005-12-01

122

Optical response of magnetically aligned nematic soft matter by transverse nemato-magnetic waves  

Microsoft Academic Search

Based on the method of molecular field dominated by magnetic component, it is shown that a homogeneous magnetically aligned nematic liquid crystal can respond to a circularly polarized optical field by transverse nemato-magnetic wave in which velocity of incompressible flow and director undergo coupled oscillations slowly traveling along the axis of magneto-optical anisotropy. The effect may be of practical interest

Sergey Bastrukov; Pik-Yin Lai; Dima Podgainy; Irina Molodtsova

2006-01-01

123

Magneto-optical contrast in near-field optics.  

PubMed

We propose a simple calculation of near-field magneto-optical (MO) images based on the beam propagation method. We calculate both Faraday rotation and circular dichroism contrasts of planar magnetic structures such as as-grown thin films and ion-irradiated samples. High-contrast near-field MO images are obtained, in good agreement with our experimental observations. PMID:11388293

Chen, Y; Kottler, V; Chappert, C; Essaidi, N

124

Planetary magnetic fields  

Microsoft Academic Search

The past several years have seen dramatic developments in the study of planetary magnetic fields, including a wealth of new data, mainly from the Galilean satellites and Mars, together with major improvements in our theoretical modeling effort of the dynamo process believed responsible for large planetary fields. These dynamos arise from thermal or compositional convection in fluid regions of large

David J. Stevenson

2003-01-01

125

Magnetic Multipole Field Model  

NSDL National Science Digital Library

The EJS Magnetic Multipole Field Model shows the field of a magnetic dipole or quadrupole with little compasses that indicate direction and relative field strength. A slider changes the angular orientation of the dipole and a movable compass shows the magnetic field direction and magnitude. Compass values can be recorded into a data table and analyzed using a built-in data analysis tool. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting âOpen Ejs Modelâ from the pop-up menu item. The Magnetic Multipole 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_em_MagneticMultipoleField.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 are available. They can be found by searching ComPADRE for Open Source Physics, OSP, or Ejs.

Christian, Wolfgang; Cox, Anne; Franciscouembre

2010-02-14

126

Magnetic Field Measurement System  

SciTech Connect

A magnetic field measurement system was designed, built and installed at MAX Lab, Sweden for the purpose of characterizing the magnetic field produced by Insertion Devices (see Figure 1). The measurement system consists of a large granite beam roughly 2 feet square and 14 feet long that has been polished beyond laboratory grade for flatness and straightness. The granite precision coupled with the design of the carriage yielded minimum position deviations as measured at the probe tip. The Hall probe data collection and compensation technique allows exceptional resolution and range while taking data on the fly to programmable sample spacing. Additional flip coil provides field integral data.

Kulesza, Joe; Johnson, Eric; Lyndaker, Aaron; Deyhim, Alex; Waterman, Dave; Blomqvist, K. Ingvar [Advanced Design Consulting USA, 126 Ridge Road, P.O. Box 187, Lansing, NY 14882 (United States); Dunn, Jonathan Hunter [MAX-lab, SE-221 00 Lund (Sweden)

2007-01-19

127

Magnetic Field Problem: Current  

NSDL National Science Digital Library

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

128

Crustal magnetic field of Mars  

Microsoft Academic Search

The equivalent source dipole technique is used to model the three components of the Martian lithospheric magnetic field. We use magnetic field measurements made on board the Mars Global Surveyor spacecraft. Different input dipole meshes are presented and evaluated. Because there is no global, Earth-like, inducing magnetic field, the magnetization directions are solved for together with the magnetization intensity. A

B. Langlais; M. E. Purucker; M. Mandea

2004-01-01

129

Electro-optic imaging chain for a biplanar fluorscope for neurosurgery: magnetic field sensitivity and contrast measurements  

NASA Astrophysics Data System (ADS)

The effects of magnetic fields on the microchannel plate (MCP) image intensifiers to be used in a novel biplanar fluoroscope are studied along with the system's overall contrast as a function of beam energy. For a second-generation device with wrap-around power supply, B-3dB values for the gain roll-off were found to be approximately 0.08 T (axial field) and 0.06 T (transverse field). The maximum image shift resulting from a 0.0035-T transverse field is found to be 0.065 mm, limited by centroid location error resulting from low-dose x- ray noise. The results of x-ray contrast studies suggests that the presently estimated 0.1-rad dose delivered on the patient (2-h magnetic stereotaxis procedure; 12% 'fluoro-on' duty cycle) might be reduced by increasing the x-ray energy.

Ramos, P. A.; Allison, Stephen W.; Molloy, J. A.; Lawson, Michael A.; Quate, E. G.; Ritter, Rogers C.; Gillies, George T.; Grady, M. S.; Howard, Matthew

1993-07-01

130

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Effective-Field Theory for Kinetic Ising Model on Honeycomb Lattice  

NASA Astrophysics Data System (ADS)

As an analytical method, the effective-field theory (EFT) is used to study the dynamical response of the kinetic Ising model in the presence of a sinusoidal oscillating field. The effective-field equations of motion of the average magnetization are given for the honeycomb lattice (Z = 3). The Liapunov exponent ? is calculated for discussing the stability of the magnetization and it is used to determine the phase boundary. In the field amplitude h0/ZJ-temperature T/ZJ plane, the phase boundary separating the dynamic ordered and the disordered phase has been drawn. In contrast to previous analytical results that predicted a tricritical point separating a dynamic phase boundary line of continuous and discontinuous transitions, we find that the transition is always continuous. There is inconsistency between our results and previous analytical results, because they do not introduce sufficiently strong fluctuations.

Shi, Xiao-Ling; Wei, Guo-Zhu

2009-05-01

131

Magnetic Fields in Galaxies  

NASA Astrophysics Data System (ADS)

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

Beck, Rainer

2012-05-01

132

The induced magnetic field.  

PubMed

Aromaticity is indispensable for explaining a variety of chemical behaviors, including reactivity, structural features, relative energetic stabilities, and spectroscopic properties. When interpreted as the spatial delocalization of ?-electrons, it represents the driving force for the stabilization of many planar molecular structures. A delocalized electron system is sensitive to an external magnetic field; it responds with an induced magnetic field having a particularly long range. The shape of the induced magnetic field reflects the size and strength of the system of delocalized electrons and can have a large influence on neighboring molecules. In 2004, we proposed using the induced magnetic field as a means of estimating the degree of electron delocalization and aromaticity in planar as well as in nonplanar molecules. We have since tested the method on aromatic, antiaromatic, and nonaromatic compounds, and a refinement now allows the individual treatment of core-, ?-, and ?-electrons. In this Account, we describe the use of the induced magnetic field as an analytical probe for electron delocalization and its application to a large series of uncommon molecules. The compounds include borazine; all-metal aromatic systems Al(4)(n-); molecular stars Si(5)Li(n)(6-n); electronically stabilized planar tetracoordinate carbon; planar hypercoordinate atoms inside boron wheels; and planar boron wheels with fluxional internal boron cluster moieties. In all cases, we have observed that planar structures show a high degree of electron delocalization in the ?-electrons and, in some examples, also in the ?-framework. Quantitatively, the induced magnetic field has contributions from the entire electronic system of a molecule, but at long range the contributions arising from the delocalized electronic ?-system dominate. The induced magnetic field can only indirectly be confirmed by experiment, for example, through intermolecular contributions to NMR chemical shifts. We show that calculating the induced field is a useful method for understanding any planar organic or inorganic system, as it corresponds to the intuitive Pople model for explaining the anomalous proton chemical shifts in aromatic molecules. Indeed, aromatic, antiaromatic, and nonaromatic molecules show differing responses to an external field; that is, they reduce, augment, or do not affect the external field at long range. The induced field can be dissected into different orbital contributions, in the same way that the nucleus-independent chemical shift or the shielding function can be separated into component contributions. The result is a versatile tool that is particularly useful in the analysis of planar, densely packed systems with strong orbital contributions directly atop individual atoms. PMID:21848282

Islas, Rafael; Heine, Thomas; Merino, Gabriel

2011-08-17

133

Magnetic field annihilators: invisible magnetization at the magnetic equator  

Microsoft Academic Search

Some distributions of magnetization give rise to magnetic fields that vanish everywhere above the surface, rendering these distributions of magnetization completely invisible. They are the annihilators of the magnetic inverse problem. Known examples are the infinite sheet with constant magnetization and the spherical shell of constant susceptibility magnetized by an arbitrary internal field. Here, we show that remarkably more interesting

S. Maus; V. Haak

2003-01-01

134

Development of an electro-optic step-by-step sampling system for IC's close electro-magnetic field measurement  

NASA Astrophysics Data System (ADS)

In this work we aim to realize a step-by-step electro-optical probe which exploits the linear (Pockels) electro-optic effect to survey the electromagnetic field on the surface of RF integrated circuits. This probe measures the variation of light polarization induced by a lithium niobate crystal immersed in the electric field provided by the DUT. The measurements will demonstrate the main features of this system which can be summarized in non-invasiveness, wide bandwidth, linearity and small spatial resolution. The LiNbO3 crystals have been developed by SELEX Sistemi Integrati S.p.A. Roma, and the whole research activity has been carried out under the sponsorship of the CRdC Nuove Tecnologie per le Attivita Produttive, the Campania Region Centre of Competence on New Technologies.

Rossi, Lucio; Breglio, G.; Irace, A.; Spirito, P.

2006-03-01

135

Magnetic Field Measurements in Beam Guiding Magnets  

Microsoft Academic Search

Electromagnets used as beam guiding elements in particle accelerators and colliders require very tight tole-rances on their magnetic fields and on their alignment along the particle path. This article describes the methods and equipment used for magnetic measurements in beam transport magnets. Descriptions are given of magnetic resonance techniques, various induction coil methods, Hall generator measurements, the fluxgate magnetometer as

K. N. Henrichsen

1998-01-01

136

Optical and magneto-optical properties of one-dimensional magnetized coupled resonator plasma photonic crystals  

SciTech Connect

In this paper, the optical and magneto-optical properties of one-dimensional magnetized coupled resonator plasma photonic crystals have been investigated. We use transfer matrix method to solve our magnetized coupled resonator plasma photonic crystals consist of dielectric and magnetized plasma layers. The results of the change in the optical and magneto-optical properties of structure as a result of the alteration in the structural properties such as thickness, plasma frequency and collision frequency, plasma filling factor, number of resonators and dielectric constant of dielectric layers and external magnetic field have been reported. The main feature of this structure is a good magneto-optical rotation that takes place at the defect modes and the edge of photonic band gap of our proposed optical magnetized plasma waveguide. Our outcomes demonstrate the potential applications of the device for tunable and adjustable filters or reflectors and active magneto-optic in microwave devices under structural parameter and external magnetic field.

Hamidi, S. M. [Laser and Plasma Research Institute, G. C., Shahid Beheshti University, Tehran 1983963113 (Iran, Islamic Republic of)

2012-01-15

137

The Heliospheric Magnetic Field  

NASA Astrophysics Data System (ADS)

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

Balogh, André; Erdõs, Géza

2013-06-01

138

Ultranarrow optical absorption and two-phonon excitation spectroscopy of Cu2O paraexcitons in a high magnetic field.  

PubMed

We show that in a magnetic field B the otherwise forbidden lowest exciton in Cu2O (paraexciton of Gamma(2)(+) symmetry) gives rise to a narrow absorption line of 80 neV at a temperature of 1.2 K. The B2 dependence of the field-induced oscillator strength and the low energy shift DeltaE with increasing field strength are measured. From two-phonon excitation spectroscopy measurements we derive by a merely kinematical analysis a very reliable value for the paraexciton mass. A blueshift and a broadening of the absorption line are observed for increasing excitation intensity. These observations are discussed in connection with a Bose-Einstein condensation of paraexcitons in Cu2O. PMID:18233254

Brandt, Jan; Fröhlich, Dietmar; Sandfort, Christian; Bayer, Manfred; Stolz, Heinrich; Naka, Nobuko

2007-11-19

139

Magnetic fields and cancer  

SciTech Connect

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

Jones, T.L.

1993-10-01

140

High magnetic field generation for laser-plasma experiments  

Microsoft Academic Search

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

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

2006-01-01

141

The influence of applied magnetic fields on the optical properties of zero- and one-dimensional CdSe nanocrystals  

NASA Astrophysics Data System (ADS)

Shape-dependent exciton relaxation dynamics of CdSe 0-D nanocrystals and 1-D nanorods were studied using low-temperature (4.2 K), time-resolved and intensity-integrated magneto-photoluminscence (MPL) spectroscopy. Analysis of the average MPL rate constants from several different nanocrystal quantum dots and rods excited by 400 nm light in applied magnetic fields up to 17.5 T revealed size-dependent energy gaps separating bright and dark exciton fine-structure states. For 1-D nanorods under strong cross-sectional confinement and large length-to-diameter aspect ratios, efficient mixing of bright and dark exciton states was achieved using relatively low applied field strengths (<=4 T). The effect was attributed, in part, to decreased confinement of CdSe hole states associated with the long axis of the nanorod, which resulted in reduction of the energy gaps separating the bright and dark states. Increased control over the angle formed between the applied field vectors and the nanocrystal c-axis led to more efficient and uniform mixing of nanorod exciton states than for quantum dots. The findings suggest 1-D nanostructures are advantageous over 0-D ones for field-responsive applications.Shape-dependent exciton relaxation dynamics of CdSe 0-D nanocrystals and 1-D nanorods were studied using low-temperature (4.2 K), time-resolved and intensity-integrated magneto-photoluminscence (MPL) spectroscopy. Analysis of the average MPL rate constants from several different nanocrystal quantum dots and rods excited by 400 nm light in applied magnetic fields up to 17.5 T revealed size-dependent energy gaps separating bright and dark exciton fine-structure states. For 1-D nanorods under strong cross-sectional confinement and large length-to-diameter aspect ratios, efficient mixing of bright and dark exciton states was achieved using relatively low applied field strengths (<=4 T). The effect was attributed, in part, to decreased confinement of CdSe hole states associated with the long axis of the nanorod, which resulted in reduction of the energy gaps separating the bright and dark states. Increased control over the angle formed between the applied field vectors and the nanocrystal c-axis led to more efficient and uniform mixing of nanorod exciton states than for quantum dots. The findings suggest 1-D nanostructures are advantageous over 0-D ones for field-responsive applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03252c

Blumling, Daniel E.; McGill, Stephen; Knappenberger, Kenneth L.

2013-09-01

142

Magnetization reversal in ultrashort magnetic field pulses  

NASA Astrophysics Data System (ADS)

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

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

2000-08-01

143

High-order optics of multipole magnets  

SciTech Connect

We have developed a new capability to compute third and fifth order Lie algebraic transfer maps for a family of realistic multipole magnets, including dipoles. The general Hamiltonian is expanded symbolically to arbitrary order. The vector potential off axis, for a given multipole symmetry, is determined from the appropriate magnetic field gradients and their longitudinal derivatives on axis. Subroutines to compute the required gradients are available for Halbach REC quadrupoles, and for general multipoles, with the current distribution on a cylindrical surface specified by a shape function. This function can be supplied by the user, or selected from internal options. Both the reference trajectory, and the map about it are calculated by numerical integration through the general magnetic field, using modular GENMAP software. This allows the calculation of curved reference trajectories in a general dipole magnet, as well as offset reference trajectories needed for misalignment tolerance studies. These new calculational capabilities have been added to the MARYLIE Lie Algebraic beam optics design code.

Walstrom, P.; Neri, F.; Mottershead, T.

1990-01-01

144

Magnetic Field Problem: Current and Magnets  

NSDL National Science Digital Library

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

Christian, Wolfgang; Belloni, Mario

2007-03-03

145

Magnetic Field Issues in Magnetic Resonance Imaging  

Microsoft Academic Search

Advances in Magnetic Resonance Imaging depend on the capability of the available hardware. Specifically, for the main magnet configuration, using derivative constraints, we can create a static magnetic field with reduced levels of inhomogeneity over a prescribed imaging volume. In the gradient coil, the entire design for the axial elliptical coil, and the mathematical foundation for the transverse elliptical coil

Labros Spiridon Petropoulos

1993-01-01

146

Ultrafast magneto-optics in nickel: magnetism or optics?  

PubMed

Several magnetic and optical processes contribute to the magneto-optical response of nickel thin films after excitation by a femtosecond laser pulse. We achieved a first complete identification by explicitly measuring the time-resolved Kerr ellipticity and rotation, as well as its temperature and magnetic field dependence in epitaxially grown (111) and (001) oriented Cu/Ni/Cu wedges. The first hundreds of femtoseconds the response is dominated by state filling effects. The true demagnetization takes approximately 0.5-1 ps. At the longer (sub-ns) time scales the spins are found to precess in their anisotropy field. Simple and transparent models are introduced to substantiate our interpretation. PMID:10991413

Koopmans; van Kampen M; Kohlhepp; de Jonge WJ

2000-07-24

147

Magnetic Fields In Relativistic Collisionless Shocks  

NASA Astrophysics Data System (ADS)

We present a systematic study on magnetic fields in Gamma-Ray Burst (GRB) relativistic shocks by making use of X-ray and optical afterglow observations, mostly coming from the Swift satellite. We use two methods to constrain the afterglow parameter epsilon_B (the fraction of energy in the magnetic field in the shocked plasma): 1. For the X-ray sample, the observed flux at the end of the X-ray steep decline is larger than or equal to the flux from the external-forward shock. 2. The observed optical afterglow flux arises from the external-forward shock emission. From the method for our X-ray sample (60 GRBs), we determine an upper limit on epsilon_B and from the method for our optical sample (35 GRBs), we determine a measurement for epsilon_B. Combining our X-ray and optical results, the median value we found for epsilon_B is ~ 10^-5. The distributions of epsilon_B from our X-ray and optical samples showed a wide distribution, with epsilon_B ranging from ~ 10^-7 - 10^-3. To characterize how much magnetic field amplification is needed, beyond shock compression of the seed magnetic field, we expressed our results for epsilon_B in terms of an amplification factor, AF. For both our X-ray and optical samples, the median value we found is AF ˜ 50-70. The distributions of AF from our X-ray and optical samples also showed a wide distribution, with AF ranging from ~ 1-1000. These results for epsilon_B and AF suggest that a weak amplification, in addition to shock compression, is needed to explain the afterglow observations. Our main conclusion is that shock compression and weak amplification of the magnetic field in GRB relativistic external shocks is sufficient to explain the afterglow data.

Santana, Rodolfo; Barniol Duran, R.; Kumar, P.

2013-01-01

148

Integrated semiconductor magnetic field sensors  

Microsoft Academic Search

Recent developments in integrated silicon magnetic devices are reviewed, with particular attention given to integrated Hall plates, magnetic field-effect transistors, vertical and lateral bipolar magnetotransistors, magnetodiodes, and current-domain magnetometers. Also described are current developments in integrated magnetic field sensors based on III-V semiconductors and bulk Hall-effect devices. The discussion also covers magnetic device modeling and the incorporation of magnetic devices

H. P. Baltes; R. S. Popovic

1986-01-01

149

Optical Wide-Field Nanoscope  

NASA Astrophysics Data System (ADS)

We describe the wide-field optical nanoimaging capabilities of a novel nanoscope based on the surface plasmon polariton (SPP) tomography technique. In contrast to other optical subwavelength resolution techniques, in our approach for imaging nanosize features, enhanced evanescent waves are coupled to the far-field via leakage radiation associated with SPPs excited by near-field fluorescence; therefore wide-field images which are not out-of-plane diffraction-limited are formed directly in the microscope's camera.

Regan, Charles; Bernussi, Ayrton; Grave de Peralta, Luis

2012-10-01

150

High magnetic field generation for laser-plasma experiments  

SciTech Connect

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

Pollock, B. B.; Froula, D. H.; Davis, P. F.; Ross, J. S.; Fulkerson, S.; Bower, J.; Satariano, J.; Price, D.; Krushelnick, K.; Glenzer, S. H. [Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551 (United States)

2006-11-15

151

High Magnetic field generation for laser-plasma experiments  

SciTech Connect

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

Pollock, B B; Froula, D H; Davis, P F; Ross, J S; Fulkerson, S; Bower, J; Satariano, J; Price, D; Glenzer, S H

2006-05-01

152

Planetary magnetic fields  

NASA Astrophysics Data System (ADS)

The past several years have seen dramatic developments in the study of planetary magnetic fields, including a wealth of new data, mainly from the Galilean satellites and Mars, together with major improvements in our theoretical modeling effort of the dynamo process believed responsible for large planetary fields. These dynamos arise from thermal or compositional convection in fluid regions of large radial extent. The relevant electrical conductivities range from metallic values to values that may be only about 1% or less that of a typical metal, appropriate to ionic fluids and semiconductors. In all planets, the Coriolis force is dynamically important, but slow rotation may be more favorable for a dynamo than fast rotation. The maintenance and persistence of convection appears to be easy in gas giants and ice-rich giants, but is not assured in terrestrial planets because the quite high electrical conductivity of iron-rich cores guarantees a high thermal conductivity (through the Wiedemann-Franz law), which allows for a large core heat flow by conduction alone. In this sense, high electrical conductivity is unfavorable for a dynamo in a metallic core. Planetary dynamos mostly appear to operate with an internal field ~(2??/?)1/2 where ? is the fluid density, ? is the planetary rotation rate and ? is the conductivity (SI units). Earth, Ganymede, Jupiter, Saturn, Uranus, Neptune, and maybe Mercury have dynamos, Mars has large remanent magnetism from an ancient dynamo, and the Moon might also require an ancient dynamo. Venus is devoid of a detectable global field but may have had a dynamo in the past. The presence or absence of a dynamo in a terrestrial body (including Ganymede) appears to depend mainly on the thermal histories and energy sources of these bodies, especially the convective state of the silicate mantle and the existence and history of a growing inner solid core. Induced fields observed in Europa and Callisto indicate the strong likelihood of water oceans in these bodies.

Stevenson, David J.

2003-03-01

153

Study of weak solar magnetic fields  

NASA Astrophysics Data System (ADS)

There have been two major gains in this period: first, the completion and analysis of round-the-clock observations in cooperation with the Huairou Observatory in the People's Republic of China, which enabled us to obtained the first longterm observations of weak solar magnetic fields, and the application of the magneto-optic filter to the measurement of magnetic fields. The observations in collaboration with China have enabled us to make observations for as long as seven days of solar magnetic regions, with only short interruptions when the sun could not be seen from the U.S. and China. The stronger elements of the chromospheric network are rather long lived, lasting about 70 hours. In fact, it is possible that they last longer, because although the shape changes, it is often possible to still identify a magnetic entity. The second important result was that one could find definite evidence of magnetic field cancellation occurring after solar flares. The increased time coverage enabled us to check the evolution of the magnetic fields during this period. The other development, the use of the magneto-optic filter, is full of promise for the future. This filter is made by using a glass tube filled with potassium which is placed in a strong magnetic field.

Zirin, Harold

154

Iron free permanent magnet systems for charged particle beam optics  

SciTech Connect

The strength and astounding simplicity of certain permanent magnet materials allow a wide variety of simple, compact configurations of high field strength and quality multipole magnets. Here we analyze the important class of iron-free permanent magnet systems for charged particle beam optics. The theory of conventional segmented multipole magnets formed from uniformly magnetized block magnets placed in regular arrays about a circular magnet aperture is reviewed. Practical multipole configurations resulting are presented that are capable of high and intermediate aperture field strengths. A new class of elliptical aperture magnets is presented within a model with continuously varying magnetization angle. Segmented versions of these magnets promise practical high field dipole and quadrupole magnets with an increased range of applicability.

Lund, S.M.; Halbach, K.

1995-09-03

155

Dayside Optical and Magnetic Correlation Events  

NASA Astrophysics Data System (ADS)

Sudden, short-lived dayside auroral activity is often observed equatorward of the quiescent auroral oval. Several cases from the 1996 South Pole and United States Automatic Geophysical Observatory (AGO) data were examined. In all cases the optical events were accompanied by well-correlated magnetic impulsive events (MIE-s). Most optical auroral activity was primarily in 630 nm emission (soft electron precipitation presumably of plasma sheet or magnetosheath origin). Each optical event also shows the presence of much shorter lived 427.8 nm emission (harder electron precipitation with associated electron acceleration). In almost all events Keograms showed repeated poleward propagation indicating that the event started at lower latitudes and propagated to higher latitudes. The optical emissions showed distinct periodicities, which correlated well with the magnetic signature. All the events began equatorward of the pre-existing quiescent aurora indicating that they initiated in the region of closed field lines. The interplanetary magnetic field Bz component prior to the events was either small or positive in most cases. The majority of the observed events were consistent with being triggered by IMF Bz or solar wind pressure change. For some events no specific trigger was found.

Mende, S. B.; Frey, H. U.; Doolittle, J. H.; Lanzerotti, L.; Maclennan, C. G.

2001-05-01

156

Dayside optical and magnetic correlation events  

NASA Astrophysics Data System (ADS)

Sudden, short-lived dayside auroral activity is often observed equatorward of the quiescent auroral oval. Several cases from the 1996 South Pole and United States Automatic Geophysical Observatory data were examined. In all cases the optical events were accompanied by well-correlated magnetic impulsive events. Most optical auroral activity was primarily in 630-nm emission (soft electron precipitation presumably of plasma sheet or magnetosheath origin). Most optical events also show the presence of much shorter lived 427.8-nm emission (harder electron precipitation with associated electron acceleration). In almost all events the keograms showed repeated poleward propagation, indicating that the event started at lower latitudes and propagated to higher latitudes. The optical emissions showed distinct periodicities, which usually correlated well with the magnetic signature. All the events began equatorward of the preexisting quiescent aurora, indicating that they initiated in the region of closed field lines. The interplanetary magnetic field Bz component prior to the events was either small or positive in most cases. The majority of the observed events were consistent with being triggered by interplanetary Bz or solar wind pressure change. For some events, no specific trigger was found.

Mende, S. B.; Frey, H. U.; Doolittle, J. H.; Lanzerotti, L.; Maclennan, C. G.

2001-11-01

157

Field Computations of Optical Antennas  

Microsoft Academic Search

Antenna-based near-field optical microscopy and spectroscopy makes use of locally enhanced opti- cal fields created near laser-irradiated metal nanostructures acting as local probes. Using three- dimensional simulations based on the finite element method we study the electromagnetic fields near various optical antennas and we optimize their geometry in order to bring out a strong enhance- ment in a selected frequency

Roman Kappeler; Daniel Erni; Cui Xudong; Lukas Novotny

158

Spin microscope based on optically detected magnetic resonance  

DOEpatents

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2010-07-13

159

Spin microscope based on optically detected magnetic resonance  

DOEpatents

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2010-06-29

160

Spin microscope based on optically detected magnetic resonance  

DOEpatents

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2009-10-27

161

Spin microscope based on optically detected magnetic resonance  

DOEpatents

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of impaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2009-11-10

162

Spin microscope based on optically detected magnetic resonance  

DOEpatents

The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

Berman, Gennady P. (Los Alamos, NM); Chernobrod, Boris M. (Los Alamos, NM)

2007-12-11

163

Polarization Diagnostics of Solar Magnetic Fields  

NASA Astrophysics Data System (ADS)

The solar atmosphere is a highly ionized medium which is the playground of magnetic fields. In the deepest layer (the photosphere), magnetic fields disturb the 'normal' fluid motions forcing the plasma to behave incounterintuitive ways; in the outer layers (the chromosphere and the corona) magnetic fields rule, making the plasma levitate or even ejecting it out of the gravitational well of the Sun, with important consequences for us here on Earth. However, magnetic fields are elusive. The only quantitative evidence of their presence is through the polarization state of the light emitted by the plasma they are playing with. Remote sensing of magnetic fields from 150 million km away through spectropolarimetry is a challenge on applied physics as well as an art. It requires the application of quantum mechanics, radiative transfer theory, and advanced optics to the interpretation and analysis of spectropolarimetric observations. I will review standard diagnostic techniques and recent developments on this field. I will discuss their limitations and how to overcome them through the complementary aspects of different diagnostic techniques, spectral regions, and statistical analysis. Finally, I will review what are the main areas for progress in this regard: most notably, the 'measurement' of magnetic fields in the extremely dilute and weakly magnetized outer layers of the sun.

Manso Sainz, R.

2011-12-01

164

Fast superconducting magnetic field switch  

DOEpatents

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

Goren, Y.; Mahale, N.K.

1996-08-06

165

Evolution of twisted magnetic fields  

SciTech Connect

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

Zweibel, E.G.; Boozer, A.H.

1985-02-01

166

Near-field magneto-optics of quantum dots  

Microsoft Academic Search

Encouraged by the latest experimental developments as well as by the theoretical interest on the near-field (NF) optics of semiconductor quantum dots (QDs), we present our most recent theoretical results on the NF optical absorption and photoluminescence (PL) of single and coupled III-V QDs subjected additionally to an external magnetic field of variable orientation and magnitude. The zero-magnetic-field ``structural'' QD

Anna Zora; Constantinos Simserides; Georgios Triberis

2007-01-01

167

Exposure guidelines for magnetic fields  

SciTech Connect

The powerful magnetic fields produced by a controlled fusion experiment at Lawrence Livermore National Laboratory (LLNL) necessitated the development of personnel-exposure guidelines for steady magnetic fields. A literature search and conversations with active researchers showed that it is currently possible to develop preliminary exposure guidelines for steady magnetic fields. An overview of the results of past research into the bioeffects of magnetic fields was compiled, along with a discussion of hazards that may be encountered by people with sickle-cell anemia or medical electronic and prosthetic implants. The LLNL steady magnetic-field exposure guidelines along with a review of developments concerning the safety of time-varying fields were also presented in this compilation. Guidelines developed elsewhere for time varying fields were also given. Further research is needed to develop exposure standards for both steady or time-varying fields.

Miller, G.

1987-12-01

168

Stellar atmospheres with magnetic field  

Microsoft Academic Search

It is proposed that the most probable configuration of the magnetic field in the atmosphere of an Ap star is an almost force-free, poloidal field, close to a low-order multipole. Such a magnetic field can not change the structure of the atmosphere to any great extent, but the vertical component of the Lorentz force can decrease the effective gravity by

K. Stepien

1980-01-01

169

Microprobe for Measuring Magnetic Fields  

Microsoft Academic Search

The Hall effect has been widely utilized to measure magnetic fields. The relatively simple geometry of a Hall element suggested the use of such a device on a microscale as a probe to examine magnetic fields of small structures. Hall probes are described which were constructed with a sensitive area about 10×10 ?. Fields of less than 0.01 gauss were

D. D. Roshon Jr.

1962-01-01

170

Magnetic fields in galactic jets  

Microsoft Academic Search

The jet region of M87 is discussed to illustrate the astrophysical observations of radio sources, with note made of magnetic field phenomena contributing to radio frequency emissions. The jet appearing in M87 has been modelled as a continuous supersonic flow of plasma embedded in a self-consistent, ordered magnetic field. The field has both parallel and helical components, and may work

A. Ferrari

1982-01-01

171

Protogalactic evolution and magnetic fields  

Microsoft Academic Search

We show that the relatively strong magnetic fields ($\\\\ge 1 \\\\mu$G) in high\\u000aredshift objects can be explained by the combined action of an evolving\\u000aprotogalactic fluctuation and electrodynamic processes providing the magnetic\\u000aseed fields. Three different seed field mechanisms are reviewed and\\u000aincorporated into a spherical \\

Harald Lesch; Masashi Chiba

1994-01-01

172

Protogalactic evolution and magnetic fields  

Microsoft Academic Search

We show that the relatively strong magnetic fields (>=1muG) 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 \\

H. Lesch; M. Chiba

1995-01-01

173

Magnetic-field-dosimetry system  

DOEpatents

A device is provided for measuring the magnetic field dose and peak field exposure. The device includes three Hall-effect sensors all perpendicular to each other, sensing the three dimensional magnetic field and associated electronics for data storage, calculating, retrieving and display.

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

1981-01-21

174

A force sensor with five degrees of freedom using optical intensity modulation for usage in a magnetic resonance field  

NASA Astrophysics Data System (ADS)

In this paper, a precise small 5-DOF (degree of freedom) force sensor is proposed for use in a strong EMF (electromagnetic field) environment. Detecting modules using CFPs (carbon fiber plates) and transducing modules using the optical modulation principle are adopted in order not to be affected by the EMF. For miniaturization of the multi-DOF force sensor, a 2-DOF transducing module using a spherical mirror and a 3-DOF transducing module using a plane mirror were designed and integrated. The design parameters of highly sensitive transducing modules were investigated and determined experimentally. To combine with these transducing modules, a 2-DOF detecting module using CFP single leaf springs and a 3-DOF detecting module using a CFP tripod spring were also designed. Considering the easy calibration process and convenient design change, the elastic detecting modules were designed so that they deform independently according to each input force component. A calibration test confirmed that the detecting modules deform linearly and independently of the input force. The results of the evaluation tests showed that the range and resolution of forces were ±4 N and 0.94-7.1 mN and the range and resolution of moments were ±120 N mm and 0.023-0.034 N mm, respectively. The high sensitivity and the linearity of the measuring results were also verified.

Kim, Min-Gyu; Lee, Dong-Hyeok; Cho, Nahm-Gyoo

2013-04-01

175

Ultrafast heating and magnetic switching with weak external magnetic field  

NASA Astrophysics Data System (ADS)

The TbFeCo magneto-optical media with the coercivity of bigger than 1.0 kOe are used for the investigation of ultrafast heating and magnetic switching with the weak external magnetic field. It has been found that the laser-induced active region becomes larger with an external magnetic field because the boundary of the active region is magnetized with the assistance of the external field during the ultrafast heating. According to this physical phenomenon, the so called ``mark expansion method'' has been proposed for visual observation of ultrafast switching marks. Using this method, the ultrafast magnetic switching in TbFeCo media has been studied using 40 fs laser pulse with linear polarization. The result shows that the ultrafast magnetic switching can be implemented by the laser pulse with assistance of the weak external field of about 0.7 kOe. Further studies show that the area percentage of the magnetic mark expansion relative to its thermal mark decreases with the increasing of the laser pulse energy. There exists the threshold pulse energy that the active region is fully magnetized. The theoretical analysis of electron, spin, and lattice temperatures has been conducted to the active region of the media where the maximum spin temperature is close to the Curie temperature of the media. The result indicates that the media become active at 4.137 ps and the ultrafast heating plays a key role for the ultrafast magnetic switching. The weak external magnetic field provides sufficient driving force to control the magnetization direction in the media.

Li, J. M.; Xu, B. X.; Zhang, J.; Ye, K. D.

2013-01-01

176

The Sun's global magnetic field.  

PubMed

Our present-day understanding of solar and stellar magnetic fields is discussed from both an observational and theoretical viewpoint. To begin with, observations of the Sun's large-scale magnetic field are described, along with recent advances in measuring the spatial distribution of magnetic fields on other stars. Following this, magnetic flux transport models used to simulate photospheric magnetic fields and the wide variety of techniques used to deduce global coronal magnetic fields are considered. The application and comparison of these models to the Sun's open flux, hemispheric pattern of solar filaments and coronal mass ejections are then discussed. Finally, recent developments in the construction of steady-state global magnetohydrodynamic models are considered, along with key areas of future research. PMID:22665897

Mackay, Duncan H

2012-07-13

177

Estimation of fluctuating magnetic fields by an atomic magnetometer  

SciTech Connect

We present a theoretical procedure to estimate with an atomic magnetometer the time dependence of a magnetic field that fluctuates according to an Ornstein-Uhlenbeck process. The magnetometer applies the detected polarization rotation of an optical probe to measure a collective atomic spin, which precesses due to the magnetic field. Based on the noisy optical detection record, our consistent Gaussian update formalism provides an estimator for the magnetic fields, and we identify analytically the steady-state performance of this estimator. We show that the estimate of the current value of the magnetic field is further improved if noisy measurement data obtained also at later times are taken into account.

Petersen, Vivi; Moelmer, Klaus [QUANTOP--Danish National Research Foundation Center for Quantum Optics, Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

2006-10-15

178

Estimation of fluctuating magnetic fields by an atomic magnetometer  

NASA Astrophysics Data System (ADS)

We present a theoretical procedure to estimate with an atomic magnetometer the time dependence of a magnetic field that fluctuates according to an Ornstein-Uhlenbeck process. The magnetometer applies the detected polarization rotation of an optical probe to measure a collective atomic spin, which precesses due to the magnetic field. Based on the noisy optical detection record, our consistent Gaussian update formalism provides an estimator for the magnetic fields, and we identify analytically the steady-state performance of this estimator. We show that the estimate of the current value of the magnetic field is further improved if noisy measurement data obtained also at later times are taken into account.

Petersen, Vivi; Mølmer, Klaus

2006-10-01

179

Microwave Measurements of Coronal Magnetic Field  

Microsoft Academic Search

Magnetic field measurements of the solar corona using microwave observation are reviewed. The solar corona is filled with highly ionised plasma and magnetic field. Moving charged particles interact with magnetic field due to Lorentz force. This results in gyration motion perpendicular to the magnetic field and free motion along the magnetic field. Circularly polarized electro-magnetic waves interact with gyrating electrons

K. Shibasaki

2006-01-01

180

Magnetic Field of Mars  

NASA Astrophysics Data System (ADS)

An internal potential function was created using the averaged MGS vector data released by Mario Acuna for altitudes from 95 to 209 km above the Martian geoid, all longitudes, and latitudes from 87 degrees south to 78 degrees north. Even with some gaps in coverage it is found that a consistent internal potential function can be derived up to spherical harmonic terms of n = 65 using all three components of the data. Weighting the data according to the standard errors given, the model fits to 7-8 nT rms. The energy density spectrum of the harmonics is seen to peak near n = 39 with a value of 7 J/cu km and fall off to less than 0.5 J/cu km below n = 15 and above n = 55. Contour maps of the X (north) component drawn for 100 km altitude show the strongly anomalous region centered at 60 degrees S latitude and 180 degrees longitude, as well as the alternating east-west trends already observed by other groups. Maps of the other components show the anomalous region, but not the east-west trends. The dichotomy is also maintained with much weaker anomalies bounding the northern plains. The results herein as as well as those of others is limited by the sparse low-altitude data coverage as well as the accuracy of the observations in the face of significant spacecraft fields. Work by Connerney and Acuna have mitigated these sources somewhat, but the design of the spacecraft did not lend itself to accurate observations. Recent results reported by David Mitchell of the ER group have shown that the field observations are significantly influenced by the solar wind with the possibility that the present results may only reflect that portion of the internal field visible above 95 km altitude. Depending on the solar wind, the anomaly field may be shielded or distorted to produce spurious results. The spectrum we have obtained so far may only see the stronger portion of the signal with a significant weaker component hidden. Measurements of crustal anomalies versus relative ages of source bodies combined with later absolute dating of Martian geologic units could lead to a quantitative constraint on the thermal history of the planet, i.e. the time when convective dynamo generation ceased in the core. Determination of directions of magnetization of anomaly sources as a function of age combined with the expectation that the Martian dynamo field was roughly aligned with the rotation axis would lead to a means of investigating polar wandering for Mars. Preliminary analysis of two magnetic anomalies in the northern polar region has yielded paleomagnetic pole positions near 50 N, 135 W, about 30 degrees north of Olympus Mons. This location is roughly consistent with the orientation of the planet expected theoretically prior to the formation of the Tharsis region. In the future, more accurate observations of the vector field at the lowest possible altitudes would significantly improve our understanding of Martian thermal history, polar wandering, and upper crustal evolution. Mapping potential resources (e.g., iron-rich source bodies) for future practical use would also be a side benefit. Additional information is contained in the original abstract.

Cain, J. C.; Ferguson, B.; Mozzoni, D.; Hood, L.

2000-07-01

181

Near-field imaging of ultrathin magnetic films with in-plane magnetization.  

PubMed

A new approach to near-field magneto-optical imaging was developed capable of visualization of in-plane magnetization of ultrathin magnetic structures. The approach relies on the magneto-optical effect specific for thin magnetic layers and employs near-field transmission measurements of longitudinal and/or transverse magneto-optical effect arising from the presence of thin film interfaces. The near-field magneto-optical contrast of in-plane domain structure of ultrathin Co film has been demonstrated in different polarization configurations. PMID:12641761

Dickson, W; Takahashi, S; Pollard, R; Atkinson, R; Zayats, A V

2003-03-01

182

Evolution of primordial magnetic fields  

NASA Astrophysics Data System (ADS)

Here we briefly summarise the main phases which determine the dynamical evolution of primordial magnetic fields in the early universe. On the one hand, strong fields undergo damping due to excitations of plasma fluctuations, and, on the other hand, weak magnetic fields will be strongly amplified by the small-scale dynamo in a turbulent environment. We find that, under reasonable assumptions concerning the efficiency of a putative magnetogenesis era during cosmic phase transitions, surprisingly strong magnetic fields 10-13-10-11 G on comparatively small scales 100 pc -10 kpc may survive to prior to structure formation. Additionally, any weak magnetic field will be exponentially amplified during the collapse of the first minihalos until they reach equipartition with the turbulent kinetic energy. Hence, we argue that it seems possible for cluster magnetic fields to be entirely of primordial origin.

Banerjee, R.

2013-06-01

183

Cosmic Magnetic Fields - An Overview  

NASA Astrophysics Data System (ADS)

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

184

Measurements of magnetic field alignment  

SciTech Connect

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

Kuchnir, M.; Schmidt, E.E.

1987-11-06

185

Origin of cosmic magnetic fields.  

PubMed

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

2013-08-06

186

Magnetic Field Problem: Measuring Current  

NSDL National Science Digital Library

A cross section of two circular wire loops carrying the exact same current is shown above (position given in centimeters and magnetic field given in milli-Tesla). You can click-drag to read the magnitude of the magnetic field.

Christian, Wolfgang; Belloni, Mario

2007-03-03

187

High-performance magnetic field and quasi-current sensors  

Microsoft Academic Search

Summary form only given. Magnetic field sensors have been constructed from two pieces of polarizing optical fiber fusion spliced to a single piece of low birefringence optical fiber. This configuration was mounted on a quartz bar for good geometric stability. A 780-nm laser diode pigtailed with polarizing fiber is used as the optical source for the sensor and light at

J. W. Dawson; T. W. MacDougall; E. Hernandez

1996-01-01

188

Aspherical magnetically modulated optical nanoprobes (MagMOONs)  

NASA Astrophysics Data System (ADS)

Aspherical magnetic particles orient in a magnetic field due to magnetic shape anisotropy. They also emit different fluxes of light from their different geometric faces due to self-absorption and total internal reflection within the particles. The particles rotate in response to rotating magnetic fields and appear to blink as they rotate. We have made pancake and chain shaped particles and magnetically modulated their fluorescent intensities. Demodulating the signal extracts the probe fluorescence from electronic and optical backgrounds dramatically increasing signal to noise ratios. The probes have applications in sensitive and rapid immunoassays, improved intracellular sensors, and inexpensive single molecule analysis.

Anker, Jeffrey N.; Behrend, Caleb; Kopelman, Raoul

2003-05-01

189

Synthetic magnetic fields for ultracold neutral atoms.  

PubMed

Neutral atomic Bose condensates and degenerate Fermi gases have been used to realize important many-body phenomena in their most simple and essential forms, without many of the complexities usually associated with material systems. However, the charge neutrality of these systems presents an apparent limitation-a wide range of intriguing phenomena arise from the Lorentz force for charged particles in a magnetic field, such as the fractional quantum Hall effect in two-dimensional electron systems. The limitation can be circumvented by exploiting the equivalence of the Lorentz force and the Coriolis force to create synthetic magnetic fields in rotating neutral systems. This was demonstrated by the appearance of quantized vortices in pioneering experiments on rotating quantum gases, a hallmark of superfluids or superconductors in a magnetic field. However, because of technical issues limiting the maximum rotation velocity, the metastable nature of the rotating state and the difficulty of applying stable rotating optical lattices, rotational approaches are not able to reach the large fields required for quantum Hall physics. Here we experimentally realize an optically synthesized magnetic field for ultracold neutral atoms, which is evident from the appearance of vortices in our Bose-Einstein condensate. Our approach uses a spatially dependent optical coupling between internal states of the atoms, yielding a Berry's phase sufficient to create large synthetic magnetic fields, and is not subject to the limitations of rotating systems. With a suitable lattice configuration, it should be possible to reach the quantum Hall regime, potentially enabling studies of topological quantum computation. PMID:19956256

Lin, Y-J; Compton, R L; Jiménez-García, K; Porto, J V; Spielman, I B

2009-12-01

190

Detection of weak (?0.5–300 nT), low frequency (5–100 Hz) magnetic fields at room temperature by kilohertz modulation of the magneto-optical hysteresis in rare earth–iron garnet films  

Microsoft Academic Search

Periodic magnetic fields with frequencies in the 5–100 Hz range and peak strengths as low as 0.5 nT have been detected at 300 K by modulating at kHz rates the magneto-optical response of epitaxial (Tm,Bi)3(Ga,Fe)5O12 rare earth–iron garnet films at ?=532 nm. By exploiting the ?1°??T slope of the magneto-optical transition region between the two magnetization states of these low

J. M. Hafez; J. Gao; J. G. Eden

2007-01-01

191

Detection of weak (~0.5-300 nT), low frequency (5-100 Hz) magnetic fields at room temperature by kilohertz modulation of the magneto-optical hysteresis in rare earth-iron garnet films  

Microsoft Academic Search

Periodic magnetic fields with frequencies in the 5-100 Hz range and peak strengths as low as 0.5 nT have been detected at 300 K by modulating at kHz rates the magneto-optical response of epitaxial (Tm,Bi)3(Ga,Fe)5O12 rare earth-iron garnet films at lambda=532 nm. By exploiting the ~1°\\/muT slope of the magneto-optical transition region between the two magnetization states of these low

J. M. Hafez; J. Gao; J. G. Eden

2007-01-01

192

Magnetic field in a finite toroidal domain  

SciTech Connect

The magnetic field structure in a domain surrounded by a closed toroidal magnetic surface is analyzed. It is shown that ergodization of magnetic field lines is possible even in a regular field configuration (with nonvanishing toroidal component). A unified approach is used to describe magnetic fields with nested toroidal (possibly asymmetric) flux surfaces, magnetic islands, and ergodic field lines.

Ilgisonis, V. I.; Skovoroda, A. A., E-mail: skovorod@nfi.kiae.r [Russian Research Centre Kurchatov Institute (Russian Federation)

2010-05-15

193

A metafluid exhibiting strong optical magnetism.  

PubMed

Advances in the field of metamaterials have enabled unprecedented control of light-matter interactions. Metamaterial constituents support high-frequency electric and magnetic dipoles, which can be used as building blocks for new materials capable of negative refraction, electromagnetic cloaking, strong visible-frequency circular dichroism, and enhancing magnetic or chiral transitions in ions and molecules. While all metamaterials to date have existed in the solid-state, considerable interest has emerged in designing a colloidal metamaterial or "metafluid". Such metafluids would combine the advantages of solution-based processing with facile integration into conventional optical components. Here we demonstrate the colloidal synthesis of an isotropic metafluid that exhibits a strong magnetic response at visible frequencies. Protein-antibody interactions are used to direct the solution-phase self-assembly of discrete metamolecules comprised of silver nanoparticles tightly packed around a single dielectric core. The electric and magnetic response of individual metamolecules and the bulk metamaterial solution are directly probed with optical scattering and spectroscopy. Effective medium calculations indicate that the bulk metamaterial exhibits a negative effective permeability and a negative refractive index at modest fill factors. This metafluid can be synthesized in large-quantity and high-quality and may accelerate development of advanced nanophotonic and metamaterial devices. PMID:23919764

Sheikholeslami, Sassan N; Alaeian, Hadiseh; Koh, Ai Leen; Dionne, Jennifer A

2013-08-13

194

Optical currents in vector fields  

NASA Astrophysics Data System (ADS)

The influence of phase relations and the degree of mutual coherence of superimposing waves in the arrangements of twowave superposition on the characteristics of the microparticle's motion has been analyzed. The prospects of studying temporal coherence using the proposed approach are made. For the first time, we have shown experimentally the possibility of diagnostics the optical currents in liquids caused by polarization characteristics of an optical field alone, using test metallic particles of nanoscale.

Angelsky, O. V.; Gorsky, M. P.; Maksimyak, P. P.; Maksimyak, A. P.; Hanson, S. G.; Zenkova, C. Y.

2011-09-01

195

Optically detected magnetic resonance (ODMR) of photoexcited triplet states  

Microsoft Academic Search

Optically Detected Magnetic Resonance (ODMR) is a double resonance technique which combines optical measurements (fluorescence,\\u000a phosphorescence, absorption) with electron spin resonance spectroscopy. After the first triplet-state ODMR experiments in\\u000a zero magnetic field reported in 1968 by Schmidt and van der Waals, the number of double resonance studies on excited triplet\\u000a states grew rapidly. Photosynthesis has proven to be a fruitful

Donatella Carbonera

2009-01-01

196

Optical imaging through scattering media via magnetically modulated fluorescence.  

PubMed

A weak (< 1000 G) magnetic field can influence photochemical processes through its effect on electron spin dynamics in a photogenerated radical pair. In a solution of pyrene and dimethylaniline this effect manifests as magnetic field-dependent exciplex fluorescence. Here we describe magnetofluorescence imaging (MFI). A localized magnetic null defines a fluorescence detection volume, which is scanned through a sample to create an image. MFI forms an image without lenses and in the presence of arbitrarily strong optical scattering. The resolution of MFI is in principle not limited by optical diffraction, although the present implementation is far from the diffraction limit. PMID:21164893

Yang, Nan; Cohen, Adam E

2010-12-01

197

Magnetic fields and scintillator performance  

SciTech Connect

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

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

1995-06-01

198

Magnetic field structure of Mercury  

NASA Astrophysics Data System (ADS)

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

Hiremath, K. M.

2012-04-01

199

Cosmic Magnetic Fields – An Overview  

Microsoft Academic Search

\\u000a Magnetic fields have been known in antiquity. Aristotle attributes the first of what could be called a scientific discussion\\u000a on magnetism to Thales, who lived from about 625 BC. In China “magnetic carts” were in use to help the Emperor in his journeys\\u000a of inspection. Plinius comments that in the Asia Minor province of Magnesia shepherds’ staffs get at times

Richard Wielebinski; Rainer Beck

2010-01-01

200

Magnetic Pumping in Spatially Inhomogeneous Magnetic Fields.  

National Technical Information Service (NTIS)

Magnetic pumping by major-radius oscillation of a toroidal plasma can be made more practical by introducing a major-radius range within which the vertical-field gradient is sufficiently great so that major-radius perturbations are marginally stable or, be...

H. P. Furth R. A. Ellis

1972-01-01

201

Simulations of Photospheric Magnetic Fields  

Microsoft Academic Search

We have run plots of artificial data, which mimic solar magnetograms, through standard algorithms to critique several results reported in the literature. In studying correlation algorithms, we show that the differences in the profiles for the differential rotation of the photospheric magnetic field stem from different methods of averaging. We verify that the lifetimes of small magnetic features, or of

A. A. Smith; H. B. Snodgrass

1999-01-01

202

Measuring Earth's Magnetic Field Simply.  

ERIC Educational Resources Information Center

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

Stewart, Gay B.

2000-01-01

203

Magnetic Field Waves at Uranus.  

National Technical Information Service (NTIS)

The proposed research efforts funded by the UDAP grant to the BRI involve the study of magnetic field waves associated with the Uranian bow shock. This is a collaborative venture bringing together investigators at the BRI, Southwest Research Institute (Sw...

C. W. Smith M. L. Goldstein R. P. Lepping W. H. Mish H. K. Wong

1991-01-01

204

Thermometers in Low Magnetic Fields  

Microsoft Academic Search

In this article the effect of low amplitude DC magnetic fields on different types of thermometers is discussed. By means of\\u000a a precision water-cooled electromagnet, the effect of a magnetic field on platinum resistance thermometers, thermistors, and\\u000a type T, J, and K thermocouples was investigated, while thermometers were thermally stabilized in thermostatic baths. Four\\u000a different baths were used for temperatures

G. Gersak; S. Begus

2010-01-01

205

Theorem on magnet fringe field  

SciTech Connect

Transverse particle motion in particle accelerators is governed almost totally by non-solenoidal magnets for which the body magnetic field can be expressed as a series expansion of the normal (b{sub n}) and skew (a{sub n}) multipoles, B{sub y} + iB{sub x} = {summation}(b{sub n} + ia{sub n})(x + iy){sup n}, where x, y, and z denote horizontal, vertical, and longitudinal (along the magnet) coordinates. Since the magnet length L is necessarily finite, deflections are actually proportional to ``field integrals`` such as {bar B}L {equivalent_to} {integral} B(x,y,z)dz where the integration range starts well before the magnet and ends well after it. For {bar a}{sub n}, {bar b}{sub n}, {bar B}{sub x}, and {bar B}{sub y} defined this way, the same expansion Eq. 1 is valid and the ``standard`` approximation is to neglect any deflections not described by this expansion, in spite of the fact that Maxwell`s equations demand the presence of longitudinal field components at the magnet ends. The purpose of this note is to provide a semi-quantitative estimate of the importance of {vert_bar}{Delta}p{sub {proportional_to}}{vert_bar}, the transverse deflection produced by the ion-gitudinal component of the fringe field at one magnet end relative to {vert_bar}{Delta}p{sub 0}{vert_bar}, the total deflection produced by passage through the whole magnet. To emphasize the generality and simplicity of the result it is given in the form of a theorem. The essence of the proof is an evaluation of the contribution of the longitudinal field B{sub x} from the vicinity of one magnet end since, along a path parallel to the magnet axis such as path BC.

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

1995-12-31

206

Optically Detected Magnetic Resonance (ODMR) of Triplet States in Photosynthesis  

Microsoft Academic Search

The triplet state of aromatic molecules and of polyenes is a versatile probe of molecular structure and of the interactions\\u000a with the environment, through the zero-field splitting (ZFS) parameters and the sublevel decay rates. These tripletproperties\\u000a can be determined accurately with magnetic resonance. Optical detection of magnetic resonance (ODMR) is often advantageous\\u000a because it pairs the frequency resolution of magnetic

Arnold J. Hoff

207

Far-Field Optical Nanoscopy  

NSDL National Science Digital Library

This article discusses the physical concepts that have pushed fluorescenesce microscopy to the nanoscale, once the prerogative of electron and scanning probe microscopes. Initial applications indicate that emergent far-field optical nanoscopy will have a strong impact in the life sciences and in other areas benefiting from nanoscale visualization.

Stefan Hell (Max Planck Institute for Biophysical Chemistry;Department of NanoBiophotonics)

2007-05-25

208

A solar magnetic and velocity field measurement system for Spacelab 2: The Solar Optical Universal Polarimeter (SOUP)  

NASA Astrophysics Data System (ADS)

The Solar Optical Universal Polarimeter (SOUP) flew on the shuttle mission Spacelab 2 (STS-51F) in August, 1985, and collected historic solar observations. SOUP is the only solar telescope on either a spacecraft or balloon which has delivered long sequences of diffraction-limited images. These movies led to several discoveries about the solar atmosphere which were published in the scientific journals. After Spacelab 2, reflights were planned on the shuttle Sunlab mission, which was cancelled after the Challenger disaster, and on a balloon flights, which were also cancelled for funding reasons. In the meantime, the instrument was used in a productive program of ground-based observing, which collected excellent scientific data and served as instrument tests. Given here is an overview of the history of the SOUP program, the scientific discoveries, and the instrument design and performance.

Tarbell, Theodore D.; Title, Alan M.

1992-08-01

209

A solar magnetic and velocity field measurement system for Spacelab 2: The solar optical universal polarimeter (SOUP)  

NASA Astrophysics Data System (ADS)

The Solar Optical Universal Polarimeter flew on the Shuttle Mission Spacelab 2 (STS-51F) in August, 1985, and collected historic solar observations. SOUP is the only solar telescope on either a spacecraft or balloon which has delivered long sequences of diffraction-limited images. These movies led to several discoveries about the solar atmosphere which were published in the scientific journals. After Spacelab 2, reflights were planned on the Space Shuttle Sunlab Mission, which was cancelled after the Challenger disaster, and on balloon flights, which were also cancelled for funding reasons. In the meantime, the instrument was used in a productive program of ground-based observing, which collected excellent scientific data and served as instrument tests. This report gives an overview of the history of the SOUP program, the scientific discoveries, and the instrument design and performance.

Tarbell, Theodore D.; Title, Alan M.

1992-08-01

210

Optical magnetic resonance imaging with an ultra-narrow optical transition  

NASA Astrophysics Data System (ADS)

We demonstrate optical magnetic resonance imaging (OMRI) of a Bose-Einstein condensate of ytterbium atoms trapped in a one-dimensional (1D) optical lattice using an ultra-narrow optical transition 1S0?3P2 ( m=-2). We developed a vacuum chamber equipped with a thin glass cell, which provides high optical access and allows a compact design of magnetic coils. A line shape of a measured spectrum of the OMRI is well described by a spatial distribution of the atoms in a 1D optical lattice with the Thomas-Fermi approximation and an applied magnetic field gradient. The observed spectrum exhibits a periodic structure corresponding to the optical lattice periodicity.

Kato, S.; Shibata, K.; Yamamoto, R.; Yoshikawa, Y.; Takahashi, Y.

2012-07-01

211

High field magnetic resonance  

US Patent & Trademark Office Database

A magnetic resonance system is disclosed. The system includes a transceiver having a multichannel receiver and a multichannel transmitter, where each channel of the transmitter is configured for independent selection of frequency, phase, time, space, and magnitude, and each channel of the receiver is configured for independent selection of space, time, frequency, phase and gain. The system also includes a magnetic resonance coil having a plurality of current elements, with each element coupled in one to one relation with a channel of the receiver and a channel of the transmitter. The system further includes a processor coupled to the transceiver, such that the processor is configured to execute instructions to control a current in each element and to perform a non-linear algorithm to shim the coil.

2010-09-21

212

MAGNETIC FIELD MEASUREMENTS FOR FAST-CHANGING MAGNETIC FIELDS.  

SciTech Connect

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

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

2004-10-03

213

The National High Magnetic Field Laboratory  

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

214

Magnetic fields in neutron stars  

NASA Astrophysics Data System (ADS)

This work aims at studying how magnetic fields affect the observational properties and the long-term evolution of isolated neutron stars, which are the strongest magnets in the universe. The extreme physical conditions met inside these astronomical sources complicate their theoretical study, but, thanks to the increasing wealth of radio and X-ray data, great advances have been made over the last years. A neutron star is surrounded by magnetized plasma, the so-called magnetosphere. Modeling its global configuration is important to understand the observational properties of the most magnetized neutron stars, magnetars. On the other hand, magnetic fields in the interior are thought to evolve on long time-scales, from thousands to millions of years. The magnetic evolution is coupled to the thermal one, which has been the subject of study in the last decades. An important part of this thesis presents the state-of-the-art of the magneto-thermal evolution models of neutron stars during the first million of years, studied by means of detailed simulations. The numerical code here described is the first one to consistently consider the coupling of magnetic field and temperature, with the inclusion of both the Ohmic dissipation and the Hall drift in the crust.

Viganò, Daniele

2013-09-01

215

Optical lattice polarization effects on magnetically induced optical atomic clock transitions  

SciTech Connect

We derive the frequency shift for a forbidden optical transition J=0{yields}J{sup '}=0 caused by the simultaneous actions of an elliptically polarized lattice field and a static magnetic field. We find that a simple configuration of lattice and magnetic fields leads to a cancellation of this shift to first order in lattice intensity and magnetic field. In this geometry, the second-order lattice intensity shift can be minimized as well by use of optimal lattice polarization. Suppression of these shifts could considerably enhance the performance of the next generation of atomic clocks.

Taichenachev, A. V.; Yudin, V. I.; Oates, C. W. [Institute of Laser Physics SB RAS, Novosibirsk 630090 (Russian Federation) and Novosibirsk State University, Novosibirsk 630090 (Russian Federation); National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)

2007-08-15

216

Magnetic fields in merging spirals - the Antennae  

NASA Astrophysics Data System (ADS)

We present an extensive study of magnetic fields in a system of merging galaxies. We obtained for NGC 4038/39 (the Antennae) radio total intensity and polarization maps at 8.44 GHz, 4.86 GHz and 1.49 GHz using the VLA in the C and D configurations. The galaxy pair possesses bright, extended radio emission filling the body of the whole system, with no dominant nuclear sources. The radio thermal fraction of NGC 4038/39 was found to be about 50% at 10.45 GHz, higher than in normal spirals. Most of the thermal emission is associated with star-forming regions, but only a part of these are weakly visible in the optical domain because of strong obscuration. The mean total magnetic fields in both galaxies are about two times stronger (?20 ?G) than in normal spirals. However, the degree of field regularity is rather low, implying tangling of the regular component in regions with interaction-enhanced star formation. Our data combined with those in H I, H?, X-rays and in far infrared allow us to study local interrelations between different gas phases and magnetic fields. We distinguish several radio-emitting regions with different physical properties and at various evolutionary stages: the rudimentary magnetic spiral, the northern cool part of the dark cloud complex extending between the galaxies, its warm southern region, its southernmost star-forming region deficient in radio emission, and the highly polarized northeastern ridge associated with the base of an unfolding tidal tail. The whole region of the dark cloud complex shows a coherent magnetic field structure, probably tracing the line of collision between the arms of merging spirals while the total radio emission reveals hidden star formation nests. The southern region is a particularly intense merger-triggered starburst. Highly tangled magnetic fields reach there strengths of ?30 ?G, even larger than in both individual galaxies, possibly due to compression of the original fields pulled out from the parent disks. In the northeastern ridge, away from star-forming regions, the magnetic field is highly coherent with a strong regular component of 10 ?G tracing gas shearing motions along the tidal tail. We find no signs of field compression by infalling gas there. The radio spectrum is much steeper in this region indicating aging of the CR electron population as they move away from their sources in star-forming regions. Modelling Faraday rotation data shows that we deal with a three-dimensionally curved structure of magnetic fields, becoming almost parallel to the sky plane in the southeastern part of the ridge.

Chy?y, K. T.; Beck, R.

2004-04-01

217

Black holes and magnetic fields  

NASA Astrophysics Data System (ADS)

The exact mechanism of formation of highly relativistic jets from galactic nuclei and microquasars remains unknown but most accepted models involve a central black hole and a strong external magnetic field. This idea is based on assumption that the black hole rotates and the magnetic field threads its horizon. Magnetic torques provide a link between the hole and the surrounding plasma which then becomes accelerated. We first review our work on black holes immersed in external stationary vacuum (electro)magnetic fields in both test-field approximation and within exact general-relativistic solutions. A special attention will be paid to the Meissner-type effect of the expulsion of the flux of external axisymmetric stationary fields across rotating (or charged) black holes when they approach extremal states. This is a potential threat to any electromagnetic mechanism launching the jets at the account of black-hole rotation because it inhibits the extraction of black-hole rotational energy. We show that the otherwise very useful "membrane viewpoint of black holes" advocated by Thorne, Price and Macdonald does not represent an adequate formalism in the context of the field expulsion from extreme black holes. After briefly summarizing the results for black holes in magnetic fields in higher dimensions - the expulsion of stationary axisymmetric fields was demonstrated to occur also for extremal black-hole solutions in string theory and Kaluza-Klein theory - we shall review astrophysically relevant axisymmetric numerical simulations reported recently by Gammie, Komissarov, Krolik and others. Although the field expulsion has not yet been observed in these time-dependent simulations, they may still be too far away from the extreme limit at which the black-hole Meissner effect should show up. We mention some open problems which, according to our view, deserve further investigation.

Bi?ák, Ji?í; Karas, Vladimír; Ledvinka, Tomáš

2007-04-01

218

Simulations of magnetic fields in the cosmos  

Microsoft Academic Search

The origin of large-scale magnetic fields in clusters of galaxies remains controversial. The intergalactic magnetic field within filaments should be less polluted by magnetised outflows from active galaxies than magnetic fields in clusters. Therefore, filaments may be a better laboratory to study magnetic field amplification by structure formation than galaxy clusters, which typically host many more active galaxies. We present

M. Brüggen; M. Hoeft

2006-01-01

219

Indoor localization using magnetic fields  

NASA Astrophysics Data System (ADS)

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

220

HMI Magnetic Field Data Products  

NASA Astrophysics Data System (ADS)

The Helioseismic and Magnetic Imager (HMI) instrument on the Solar Dynamics Observatory (SDO) spacecraft will begin observing the solar photospheric magnetic field continuously after commissioning in early 2009. This paper describes the HMI magnetic processing pipeline and the expected data products that will be available. The full disk line-of-sight magnetic field will be available every minute with 1" resolution. Comparable vector measurements collected over a three-minute time interval will ordinarily be averaged for at least 10 minutes before inversion. Useful Quick Look products for forecasting purposes will be available a few minutes after observation. Final products will be computed within 36 hours and made available through the SDO Joint Science Operations Center (JSOC). Three kinds of magnetic data products have been defined - standard, on-demand, and on-request. Standard products, such as frequently updated synoptic charts, are made all the time on a fixed cadence. On-demand products, such as high cadence full-disk disambiguated vector magnetograms, will be generated whenever a user asks for them. On-request products, such as high-resolution time series of MHD model solutions, will be generated as resources allow. This paper describes the observations, magnetograms, synoptic and synchronic products, and field model calculations that will be produced by the HMI magnetic pipeline.

Hoeksema, J.; Hmi, M. T.

2008-05-01

221

Tunneling in a magnetic field  

SciTech Connect

Quantum tunneling across a static potential barrier in a static magnetic field is very sensitive to an analytical form of the potential barrier. Depending on that, the oscillatory structure of the modulus of the wave function can be formed in the direction of tunneling. Due to an underbarrier interference, the probability of tunneling through a higher barrier can be larger than through a lower one. For some barriers the quantum interference of underbarrier cyclotron paths results in a strong enhancement of tunneling. This occurs in the vicinity of the certain magnetic field and is referred to as Euclidean resonance. This strongly contrasts to the Wentzel, Kramers, and Brillouin type tunneling which occurs with no magnetic field.

Ivlev, B. [Department of Physics and Astronomy and NanoCenter, University of South Carolina, Columbia, South Carolina 29208 (United States) and Instituto de Fisica, Universidad Autonoma de San Luis Potosi, San Luis Potosi, San Luis Potosi 78000 Mexico

2006-05-15

222

Thermalization in external magnetic field  

NASA Astrophysics Data System (ADS)

In the AdS/CFT framework meson thermalization in the presence of a constant external magnetic field in a strongly coupled gauge theory has been studied. In the gravitational description the thermalization of mesons corresponds to the horizon formation on the flavour D7-brane which is embedded in the AdS 5 × S 5 background in the probe limit. The apparent horizon forms due to the time-dependent change in the baryon number chemical potential, the injection of baryons in the gauge theory. We will numerically show that the thermalization happens even faster in the presence of the magnetic field on the probe brane. We observe that this reduction in the thermalization time sustains up to a specific value of the magnetic field.

Ali-Akbari, Mohammad; Ebrahim, Hajar

2013-03-01

223

Electro-mechanical resonant magnetic field sensor  

NASA Astrophysics Data System (ADS)

We describe a new type of magnetic field sensor, which is termed as an Electro-Mechanical Resonant Sensor (EMRS). The key part of this sensor is a small conductive elastic element with low damping rate and therefore, a high /Q fundamental mode of frequency f1. An AC current is driven through the elastic element which, in the presence of a magnetic field, causes an AC force on the element. When the frequency of the AC current matches the resonant frequency of the element, maximum vibration of the element occurs and this can be measured precisely by optical means. We have built and tested a model sensor of this type by using for the elastic element, a length of copper wire of diameter 0.030mm formed into a loop shape. The wire motion was measured using a light-emitting diode photo-transistor assembly. This sensor demonstrated a sensitivity better than 0.001G for an applied magnetic field of ~1G and a good selectivity for the magnetic field direction. The sensitivity can be easily improved by a factor of /~10-100 by a more sensitive measurement of the elastic element motion and by having the element in vacuum to reduce the drag force.

Temnykh, Alexander B.; Lovelace, Richard V. E.

2002-05-01

224

Magnetic field heating study of Fe-doped Au nanoparticles  

NASA Astrophysics Data System (ADS)

Fe-doped Au nanoparticles are ideal for biological applications over magnetic oxides due to their conjugation chemistry, optical properties, and surface chemistry. We present an AC magnetic field heating study of 8 nm Fe-doped Au nanoparticles which exhibit magnetic behavior. Magnetic heating experiments were performed on stable aqueous solutions of the nanoparticles at room temperature. The nanoparticles exhibit magnetic field heating, with a specific absorption rate (SAR) of 1.84 W/g at 40 MHz and H=100 A/m. The frequency dependence of the heating follows general trends predicted by power loss equations and is similar to traditional materials.

Wijaya, Andy; Brown, Katherine A.; Alper, Joshua D.; Hamad-Schifferli, Kimberly

2007-02-01

225

Influence of switchable magnetic field on the modulation property of nanostructured magnetic fluids  

NASA Astrophysics Data System (ADS)

Magnetic fluid is a kind of colloidal material with tunable microstructure and unique optical properties. The tunable magneto-optical modulation property of magnetic fluid under externally switchable magnetic field with various modulation periods is investigated theoretically and experimentally. The transitional modulation period (lower limit of the working frequency) between the square-like and oscillation-like modulation is achieved and found to be magnetic-field- and sample-concentration-dependent. The modulation mechanism is analyzed and ascribed to the dynamic microstructure of magnetic fluid under different modulation periods of external magnetic fields. The result of this work may be helpful for the pragmatic applications of magnetic fluid based on the square-like modulation.

Ji, Hongzhu; Pu, Shengli; Wang, Xiang; Yu, Guojun

2012-10-01

226

Sub-Doppler laser cooling in a magnetic field  

SciTech Connect

This paper reports on sub-Doppler laser cooling processes in a light field of constant polarization with an applied magnetic field. A theoretical model is developed to describe these experiments that is valid for arbitrary transition schemes. Adding the magnetic field to the optical molasses gives rise to new phenomena such as cooling of atoms to a non-zero velocity that can also be used to test the 1-D model. (AIP)

Shang, S.; Sheehy, B.; van der Straten, P.; Metcalf, H. (Physics Department, State University of New York, Stony Brook, New York 11790 (United States))

1991-08-05

227

Photospheric Magnetic Field: Quiet Sun  

NASA Astrophysics Data System (ADS)

The solar photosphere is the layer in which the magnetic field has been most reliably and most often measured. Zeeman- and Hanle-effect based probes have revealed many details of a rich variety of structures and dynamic processes, but the number of open and debated questions has remained large. The magnetic field in the quiet Sun has maintained a particularly large number of secrets and has been a topic of a particularly lively debate as new observations and analysis techniques have revealed new and often unexpected aspects of its organization, physical structure and origin.

Solanki, S. K.

2009-06-01

228

Sound waves in solids in magnetic field  

NASA Astrophysics Data System (ADS)

In this communication we present a theoretical analysis of sound modes in non-magnetic solids or fluids in static and uniform magnetic field. The physics behind is based on the so-called gyromagnetic phenomena i.e., the appearance of a magnetic moment due to the intrinsic orbital moment of vibrational modes. The gyromagnetic contributions into the Lagrangian describing vibrations, conceptually dramatically modify the correlation (and linear response) functions of the displacements. Namely, in the response function one gets singular branching points (instead of simple poles which determine sound mode dispersion laws). In practical terms the corrections are very small although X-ray and optic experimental techniques have progressed to the point where observations of such very small effects are not hopeless.

Dzyaloshinskii, I. E.; Kats, E. I.

2011-11-01

229

Photospheric and coronal magnetic fields  

SciTech Connect

Research on small-scale and large-scale photospheric and coronal magnetic fields during 1987-1990 is reviewed, focusing on observational studies. Particular attention is given to the new techniques, which include the correlation tracking of granules, the use of highly Zeeman-sensitive infrared spectral lines and multiple lines to deduce small-scale field strength, the application of long integration times coupled with good seeing conditions to study weak fields, and the use of high-resolution CCD detectors together with computer image-processing techniques to obtain images with unsurpassed spatial resolution. Synoptic observations of large-scale fields during the sunspot cycle are also discussed. 101 refs.

Sheeley, N.R., Jr. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

230

Novel optical devices based on the tunable refractive index of magnetic fluid and their characteristics  

NASA Astrophysics Data System (ADS)

As a new type of functional material, magnetic fluid (MF) is a stable colloid of magnetic nanoparticles, dressed with surfactant and dispersed in the carrier liquid uniformly. The MF has many unique optical properties, and the most important one is its tunable refractive index property. This paper summarizes the properties of the MF refractive index and the related optical devices. The refractive index can be easily controlled by external magnetic field, temperature, and so on. But the tunable refractive index of MF has a relaxation effect. As a result, the response time is more than milliseconds and the MF is only suitable for low speed environment. Compared with the traditional optical devices, the magnetic fluid based optical devices have the tuning ability. Compared with the tunable optical devices (the electro-optic devices (LiNbO3) of more than 10 GHz modulation speed, acoustic-optic devices (Ge) of more than 20 MHz modulation speed), the speed of the magnetic fluid based optical devices is low. Now there are many applications of magnetic fluid based on the refractive index in the field of optical information communication and sensing technology, such as tunable beam splitter, optical-fiber modulator, tunable optical gratings, tunable optical filter, optical logic device, tunable interferometer, and electromagnetic sensor. With the development of the research and application of magnetic fluid,a new method, structure and material to improve the response time can be found, which will play an important role in the fields of optical information communication and sensing technology.

Zhao, Yong; Zhang, Yuyan; Lv, Riqing; Wang, Qi

2011-12-01

231

Tracking charged particles through magnetic fields using MCNP and MCNPX  

Microsoft Academic Search

The MCNP and MCNPX multiparticle Monte Carlo transport codes have been modified with a patch that allows specialized tracking of charged particles through the magnetic fields of a charged-particle beam optics system using pregenerated maps output from the COSY INFINITY code. A map is the rule for updating the particles' phase-space through a magnetic element. A file containing a single

J. A. Favorite; K. J. Adams; J. D. Zumbro

1999-01-01

232

Magnetic Field from Loops Model  

NSDL National Science Digital Library

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

233

Magnetic field generation in Galactic molecular clouds  

NASA Astrophysics Data System (ADS)

We investigate the magnetic field which is generated by turbulent motions of a weakly ionized gas. Galactic molecular clouds give us an example of such a medium. As in the Kazantsev-Kraichnan model we assume a medium to be homogeneous and a neutral gas velocity field to be isotropic and ? correlated in time. We take into consideration the presence of a mean magnetic field, which defines a preferred direction in space and eliminates isotropy of magnetic field correlators. Evolution equations for the anisotropic correlation function are derived. Isotropic cases with zero mean magnetic field as well as with small mean magnetic field are investigated. It is shown that stationary bounded solutions exist only in the presence of the mean magnetic field for the Kolmogorov neutral gas turbulence. The dependence of the magnetic field fluctuations amplitude on the mean field is calculated. The stationary anisotropic solution for the magnetic turbulence is also obtained for large values of the mean magnetic field.

Istomin, Ya. N.; Kiselev, A.

2013-10-01

234

FIELD CHARACTERIZATION OF XFEL QUADRUPOLE MAGNETS  

Microsoft Academic Search

A rotating coil setup for magnetic field characterization and fiducialization of XFEL quadrupole magnets is pre- sented. The instrument allows measurement of the rel- ative position of the magnetic axis with accuracy better than 1 ?m and measurement of weak magnetic error field components. Tests and evaluation based on a FLASH quadrupole magnet are presented together with a discus- sion

A. Hedqvist; H. Danared; F. Hellberg; J. Pfluger

235

EXPLORER 10 MAGNETIC FIELD MEASUREMENTS  

Microsoft Academic Search

Magnetic field measurements made by means of Explorer 10 over geocentric ; distances of 1.8 to 42.6R\\/sub e\\/ on March 25experiment on the same satellite are ; referenced in interpretations. The close-in data are consistent with the ; existence of a very weak ring current below 3R\\/sub e\\/ along the trajectory, but ; alternative explanations for the field deviations are

J. P. Heppner; N. F. Ness; C. S. Scearce; T. L. Skillman

1963-01-01

236

Magnetic fields in extragalactic jets  

Microsoft Academic Search

Observations indicate that jets (i.e., charged particle beams) are emitted from the central black hole sources of active galactic nuclei and quasars. Magnetic fields are produced in e(-)-p or e(-)-e(+)-p jets when electrons (and positrons) are slowed with respect to protons in the jets. Interaction with an ambient interstellar gas or external radiation field can cause such drift velocities. Calculations

William K. Rose

1987-01-01

237

Magnetic fields in extragalactic jets  

Microsoft Academic Search

Observations indicate that jets are emitted from the central black hole sources of active galactic nuclei and quasars. Magnetic fields are produced in e--p or e--e+-p jets when electrons and positrons are slowed with respect to protons in the jets. Interaction with an ambient interstellar gas or external radiation field can cause such drift velocities. In this paper calculations for

William K. Rose

1987-01-01

238

The somatosensory evoked magnetic fields  

Microsoft Academic Search

Averaged magnetoencephalography (MEG) following somatosensory stimulation, somatosensory evoked magnetic field(s) (SEF), in humans are reviewed. The equivalent current dipole(s) (ECD) of the primary and the following middle-latency components of SEF following electrical stimulation within 80–100 ms are estimated in area 3b of the primary somatosensory cortex (SI), the posterior bank of the central sulcus, in the hemisphere contralateral to the

Ryusuke Kakigi; Minoru Hoshiyama; Motoko Shimojo; Daisuke Naka; Hiroshi Yamasaki; Shoko Watanabe; Jing Xiang; Kazuaki Maeda; Khanh Lam; Kazuya Itomi; Akinori Nakamura

2000-01-01

239

Optics of magnetic photonic crystals with mu-negative materials  

NASA Astrophysics Data System (ADS)

In this paper, we have made an analysis of the optics of magnetic photonic crystals having mu-negative materials. We consider the magnetic photonic crystal with different values of the magnetic permeability of the materials (PIM). Such materials will be affected by the applied magnetic field and can also exhibit the properties of superconducting materials. We infer that PhC with MNM and PIM materials can be used as tunable devices by choosing proper thickness, damping factor, and mu-value of the PIM.

Kumar, N.; Thapa, K. B.; Janma, Ram; Pandey, G. N.; Reena

2013-06-01

240

Influence of crossed electric and quantizing magnetic fields on the Einstein relation in nonlinear optical, optoelectronic and related materials: Simplified theory, relative comparison and suggestion for experimental determination  

Microsoft Academic Search

An attempt is made to study the Einstein relation for the diffusivity-to-mobility ratio (DMR) under crossed fields’ configuration in nonlinear optical materials on the basis of a newly formulated electron dispersion law by incorporating the crystal field in the Hamiltonian and including the anisotropies of the effective electron mass and the spin–orbit splitting constants within the framework of kp formalisms.

S. Pahari; S. Bhattacharya; D. De; S. M. Adhikari; A. Niyogi; A. Dey; N. Paitya; S. C. Saha; K. P. Ghatak; P. K. Bose

2010-01-01

241

Magnetic Field Issues in Magnetic Resonance Imaging.  

NASA Astrophysics Data System (ADS)

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

Petropoulos, Labros Spiridon

242

Advances in Magnetic Field Sensors  

Microsoft Academic Search

The most important milestone in the field of magnetic sensors was when AMR sensors started to replace Hall sensors in many applications where the greater sensitivity of AMRs was an advantage. GMR and SDT sensors finally found applications. We also review the development of miniaturization of fluxgate sensors and refer briefly to SQUIDs, resonant sensors, GMIs, and magnetomechanical sensors.

Pavel Ripka; Michal Janosek

2010-01-01

243

Random Field Effect in Magnets.  

National Technical Information Service (NTIS)

In order to explore the consequences of random field effects we have carried out a series of neutron scattering experiments on three prototypical diluted Ising magnets. The systems studied are Rb sub 2 Co sub 7 Mg sub 3 F sub 4 which is a model two dimens...

R. J. Birgeneau

1982-01-01

244

Magnetic Field Waves at Uranus.  

National Technical Information Service (NTIS)

The research efforts funded by the Uranus Data Analysis Program (UDAP) grant to the Bartol Research Institute (BRI) involved the study of magnetic field waves associated with the Uranian bow shock. Upstream wave studies are motivated as a study of the phy...

C. W. Smith M. L. Goldstein R. P. Lepping W. H. Mish H. K. Wong

1994-01-01

245

Radiative transfer in very strong magnetic fields  

NASA Astrophysics Data System (ADS)

The study of the cooling of neutron stars has been undertaken by many researchers in the past twenty-five years, but this study has been made difficult by the inherent theoretical and observational uncertainties; most observations of their thermal X-ray flux have yielded only upper limits. More sensitive satellites such as ROSAT and AXAF may provide more positive flux information, and it is important to know how to interpret these data in terms of surface temperature. One of the most important factors in this interpretation is the effect of the surface magnetic field.Young neutron stars are believed to have extremely strong magnetic fields, on the order of 10(12)G. These fields dominate the physics of the atmosphere. In particular, atoms in the atmospheres of neutron stars have much greater binding energies than in the zero-field case, and they are constrained to move along the field lines. We use a multiconfigurational Hartree-Fock code, modified for very strong magnetic fields, to calculate wavefunctions, energies and oscillator strengths for several atoms in representative values of the magnetic field.We then use these simulations to construct model atmospheres for neutron stars. Because of the low mass necessary for optical depth unity in the soft X-rays (typically [...]) and because of the short time scale for gravitational separation (~ 1 - 100s), the photosphere is likely to consist of a pure element. Numerous processes could cause many elements to be important, so we investigate atmospheres consisting of pure hydrogen, helium, carbon, nitrogen and silicon in magnetic fields of 9.4 x 10(11)G, 2.35 x 10(12)G, and 4.7 x 10(12)G.We also use the high-field energies to investigate soft X-ray lines in gamma-ray bursts. Highly ionized elements could create absorption lines in the 1-15keV range, and the identification of such lines in conjunction with cyclotron lines would determine the magnetic field and gravitational redshift on the surface of the star, which would provide clues to the equation of state on the interior. We conclude with a discussion of the prospect of identifying these lines with future satellites.

Miller, Michael Coleman

246

NMR imaging in the earth's magnetic field.  

PubMed

The most important and very expensive part of a magnetic resonance imaging set-up is the magnet, which is capable of generating a constant and highly homogeneous magnetic field. Here a new MR imaging technique without the magnet is introduced. This technique uses the earth's magnetic field instead of a magnetic field created by a magnet. This new method has not yet reached the stage of medical application, but the first images obtained by MRIE (magnetic resonance imaging in the earth's field) show that the resolution is close to that expected based on sensitivity estimations. PMID:2233218

Stepisnik, J; Erzen, V; Kos, M

1990-09-01

247

Separation of magnetic field lines  

SciTech Connect

The field lines of magnetic fields that depend on three spatial coordinates are shown to have a fundamentally different behavior from those that depend on two coordinates. Unlike two-coordinate cases, a flux tube in a magnetic field that depends on all three spatial coordinates that has a circular cross section at one location along the tube characteristically has a highly distorted cross section at other locations. In an ideal evolution of a magnetic field, the current densities typically increase. Crudely stated, if the current densities increase by a factor {sigma}, the ratio of the long to the short distance across a cross section of a flux tube characteristically increases by e{sup 2{sigma}}, and the ratio of the longer distance to the initial radius increases as e{sup {sigma}}. Electron inertia prevents a plasma from isolating two magnetic field structures on a distance scale shorter than c/{omega}{sub pe}, which is about 10 cm in the solar corona, and reconnection must be triggered if {sigma} becomes sufficiently large. The radius of the sun, R{sub Circled-Dot-Operator }=7 Multiplication-Sign 10{sup 10}cm is about e{sup 23} times larger, so when {sigma} Greater-Than-Or-Equivalent-To 23, two lines separated by c/{omega}{sub pe} at one location can be separated by the full scale of any magnetic structures in the corona at another. The conditions for achieving a large exponentiation, {sigma}, are derived, and the importance of exponentiation is discussed.

Boozer, Allen H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States)

2012-11-15

248

Active Region Magnetic Fields. I. Plage Fields  

NASA Astrophysics Data System (ADS)

We present observations taken with the Advanced Stokes Polarimeter (ASP) in active-region plages and study the frequency distribution of the magnetic field strength (B), inclination with respect to vertical ( gamma ), azimuthal orientation ( chi ), and filling factor (f). The most common values at disk center are B = 1400 G, gamma < 10 deg, no preferred east-west orientation, and f = 15%. At disk center, there is a component of weak (<1000 G), more horizontal fields that corresponds to arching field lines connecting footpoints of different polarities. The center-to-limb variation (CLV) of the field strength shows that, close to the limb ( mu = 0.3), the field strength is reduced to 800 G from its disk-center value. This can be interpreted as a gradient of B with height in solar plages of around -3 G km-1. From this CLV study, we also deduce that magnetic field lines remain vertical for the entire range of heights involved. A similar analysis is performed for structures found in active regions that show a continuous distribution of azimuths (resembling sunspots) but that do not have a darkening in continuum. These "azimuth centers" show slightly larger values of B than normal plages, in particular at their magnetic center. Filling factors are also larger on average for these structures. The velocities in the magnetic component of active regions have been studied for both averaged Stokes profiles over the entire active region and for the spatially resolved data. The averaged profiles (more representative of high filling factor regions) do not show any significant mean velocities. However, the spatial average of Doppler velocities derived from the spatially resolved profiles (i.e., unweighted by filling factor) show a net redshift at disk center of 200 m s-1. The spatially resolved velocities show a strong dependence on filling factor. Both mean velocities and standard deviations are reduced when the filling factor increases. This is interpreted as a reduction of the p-mode amplitude within the magnetic component. Strong evidence for velocities transverse to the magnetic field lines has been found. Typical rms values are between 200 and 300 m s-1, depending on the filling factor. The possible importance of these transverse motions for the dynamics of the upper atmospheric layers is discussed. The asymmetries of the Stokes profiles and their CLV have been studied. The averaged Stokes V profiles show amplitude and area asymmetries that are positive at disk center and become negative at the limb. Both asymmetries, and for the two Fe I lines, are maximized away from disk center. The spatially resolved amplitude asymmetries show a clear dependence on filling factor: the larger the filling factor, the smaller the amplitude asymmetry. On the other hand, the area asymmetry is almost independent of the filling factor. The only observed dependence is the existence of negative area-asymmetry profiles at disk center for filling factors smaller than 0.2. Around 20% of the observed points in a given plage have negative area asymmetry. The amplitude asymmetry of Stokes V is, on the other hand, always positive. The amplitude asymmetries of the linear polarization profiles are observed to have the same sign as the Stokes V profiles. Similarly, the same CLV variation of the linear polarization amplitude asymmetries as for Stokes V has been found. The scenarios in which this similarity can exist are studied in some detail.

Martinez Pillet, V.; Lites, B. W.; Skumanich, A.

1997-01-01

249

Electron dynamics in inhomogeneous magnetic fields.  

PubMed

This review explores the dynamics of two-dimensional electrons in magnetic potentials that vary on scales smaller than the mean free path. The physics of microscopically inhomogeneous magnetic fields relates to important fundamental problems in the fractional quantum Hall effect, superconductivity, spintronics and graphene physics and spins out promising applications which will be described here. After introducing the initial work done on electron localization in random magnetic fields, the experimental methods for fabricating magnetic potentials are presented. Drift-diffusion phenomena are then described, which include commensurability oscillations, magnetic channelling, resistance resonance effects and magnetic dots. We then review quantum phenomena in magnetic potentials including magnetic quantum wires, magnetic minibands in superlattices, rectification by snake states, quantum tunnelling and Klein tunnelling. The third part is devoted to spintronics in inhomogeneous magnetic fields. This covers spin filtering by magnetic field gradients and circular magnetic fields, electrically induced spin resonance, spin resonance fluorescence and coherent spin manipulation. PMID:21393794

Nogaret, Alain

2010-06-04

250

Magnetic fields in the cosmos  

SciTech Connect

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

Parker, E.N.

1983-08-01

251

Behavior of magnetic liquids in an inhomogeneous magnetic field  

SciTech Connect

The authors present experimental results from the investigation of the behavior of certain magnetic liquids differeing in the degree of stability in inhomogenous magnetic fields. The growth of holding presure of sealing step at rest is reviewed and the increase of effective viscosity in inhomogeneous magnetic fields is studied. The behaviors of magnetic liquids in an inhomogeneous magnetic field are sensitive to structural changes caused by the field. Significant differences are demonstrated between magnetic liquids with the same saturation magnetization but different particle size distribution.

Anton, I.; Bika, D.; Potents, I.; Vekash, L.

1986-01-01

252

Optical and magnetic manipulation of hybrid micro and nanoparticle sensors  

Microsoft Academic Search

Microparticles and nanoparticles have been used in a wide variety of applications ranging from biomedical to optical and electronic technologies. The microscopic and mesoscopic size scale of single particles makes them ideal tools for probing the local environments of biological cells, sensing the viscous properties of fluids and surfaces on the microscale, and interacting with photonic and magnetic fields. But

Rodney Ray Agayan

2008-01-01

253

SQUID-Detected Magnetic Resonance Imaging in Microtesla Magnetic Fields  

Microsoft Academic Search

We describe studies of nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) of liquid samples at room temperature in microtesla magnetic fields. The nuclear spins are prepolarized in a strong transient field. The magnetic signals generated by the precessing spins, which range in frequency from tens of Hz to several kHz, are detected by a low-transition temperature dc

R. McDermott; N. Kelso; S. K. Lee; M. MöBetale; M. Mück; W. Myers; B. ten Haken; H. C. Seton; A. H. Trabesinger; A. Pines; J. Clarke

2004-01-01

254

Two dimensional frustrated magnets in high magnetic field  

Microsoft Academic Search

Frustrated magnets in high magnetic field have a long history of offering beautiful surprises to the patient investigator. Here we present the results of extensive classical Monte Carlo simulations of a variety of models of two dimensional magnets in magnetic field, together with complementary spin wave analysis. Striking results include (i) a massively enhanced magnetocaloric effect in antiferromagnets bordering on

L. Seabra; N. Shannon; P. Sindzingre; T. Momoi; B. Schmidt; P. Thalmeier

2009-01-01

255

The HMI Magnetic Field Pipeline  

NASA Astrophysics Data System (ADS)

The Helioseismic and Magnetic Imager (HMI) will provide frequent full-disk magnetic field data after launch of the Solar Dynamics Observatory (SDO), currently scheduled for fall 2009. 16 megapixel line-of-sight magnetograms (Blos) will be recorded every 45 seconds. A full set of polarized filtergrams needed to determine the vector magnetic field requires 90 seconds. Quick-look data will be available within a few minutes of observation. Quick-look space weather and browse products must have identified users, and the list currently includes full disk magnetograms, feature identification and movies, 12-minute disambiguated vector fields in active region patches, time evolution of AR indices, synoptic synchronic frames, potential and MHD model results, and 1 AU predictions. A more complete set of definitive science data products will be offered about a day later and come in three types. "Pipeline” products, such as full disk vector magnetograms, will be computed for all data on an appropriate cadence. A larger menu of "On Demand” products, such as Non-Linear Force Free Field snapshots of an evolving active region, will be produced whenever a user wants them. Less commonly needed "On Request” products that require significant project resources, such as a high resolution MHD simulation of the global corona, will be created subject to availability of resources. Further information can be found at the SDO Joint Science Operations Center web page, jsoc.stanford.edu

Hoeksema, Jon Todd; Liu, Y.; Schou, J.; Scherrer, P.; HMI Science Team

2009-05-01

256

Magnetic Resonance Imaging System Based on Earth's Magnetic Field  

Microsoft Academic Search

This article describes both the setup and the use of a system for magnetic resonance imaging (MRI) in the Earth's magnetic field. Phase instability caused by temporal fluctuations of Earth's field can be successfully improved by using a reference signal from a separate Earth's field nuclear magnetic resonance (NMR) spectrometer\\/magnetometer. In imaging, it is important to correctly determine the phase

Ales Mohoric; Gorazd Planinsic; Miha Kos; Andrej Duh; Janez Stepisnik

2004-01-01

257

Magnetic field of atrial depolarization.  

PubMed

The isomagnetic maps of normal subjects and patients with right and left atrial overloading were recorded to determine the characteristic features of the magnetic field of atrial depolarization. The isomagnetic maps examined in this study indicated the instantaneous current source, which specifically localizes the current sources due to the right and left atria, respectively. The magnetic field recorded with a second derivative gradiometer clearly detected the cardiac current source from the right atrium, which is located close to the anterior chest wall, thus this method improved the diagnostic sensitivity for right atrial overloading. In patients with left atrial overloading, the isomagnetic map showed multiple dipoles due to the right and left atria, respectively, which are difficult to be detected by the electrocardiogram or isopotential map. These results suggest that the magnetocardiogram provides useful information on the current source to supplement information obtained by the conventional electrocardiogram. PMID:2978585

Takeuchi, A; Watanabe, K; Katayama, M; Nomura, M; Nakaya, Y; Mori, H

258

Magnetic field detection enhancement in an external cavity fiber Fabry-Perot sensor  

Microsoft Academic Search

The sensitivity of an extrinsic fiber-optic magnetic field sensor using a gallium doped yttrium iron garnet (Ga:YIG) bulk optic crystal has been significantly improved by incorporating a Fabry-Perot resonator around the crystal

R. B. Wagreich; C. C. Davis

1996-01-01

259

Anisotropic Magnetism in Field-Structured Composites  

SciTech Connect

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

Anderson, Robert A.; Martin, James E.; Odinek, Judy; Venturini, Eugene

1999-06-24

260

Studies on Somatosensory Evoked Magnetic Fields.  

National Technical Information Service (NTIS)

Spatiotemporal patterns of somatosensory evoked magnetic fields to stimulation of upper and lower limb nerves were examined in healthy humans. The studies summarized here provide the first magnetic field maps over the primary foot projection area after li...

J. Huttunen

1987-01-01

261

Luminescence in applied magnetic fields  

NASA Astrophysics Data System (ADS)

Metal complexes and solids were synthesized and subjected to photoexcitation measurements under the influence of externally applied magnetic fields. The photoluminescence of complexes of rhodium (I) and iridium (I) displayed both field induced emission bands and a many fold shortening of the excited state lifetime. Both the decay rates and the induced emission band intensities showed a quadratic dependence on the applied field. A several fold shortening of the phosphorescence from the octaphosphitoplatinum (II) anion under an applied field (50 T) was also observed. Spectroscopic studies of several bis (N-heterocyclic) complexes of copper (I) were also concluded and complete group theoretic assignments of the charge transfer excited states were made. The technique of Thermal Modulation was perfected and applied to the study of the exited states of transition metal complexes with near degenerate emitting states.

Crosby, G. A.

1989-08-01

262

Simulations of Photospheric Magnetic Fields  

NASA Astrophysics Data System (ADS)

We have run plots of artificial data, which mimic solar magnetograms, through standard algorithms to critique several results reported in the literature. In studying correlation algorithms, we show that the differences in the profiles for the differential rotation of the photospheric magnetic field stem from different methods of averaging. We verify that the lifetimes of small magnetic features, or of small patterns of these features in the large-scale background field, are on the order of months, rather than a few days. We also show that a meridional flow which is cycle dependent creates an artifact in the correlation-determined magnetic rotation which looks like a torsional oscillation; and we compare this artifact to the torsional patterns that have been reported. Finally, we simulate the time development of a large-scale background field created solely from an input of artifical, finite-lifetime 'sunspot' bipoles. In this simulation, we separately examine the effects of differential rotation, meridional flow and Brownian motion (random walk, which we use rather than diffusion), and the inclination angles of the sunspot bipoles (Joy's law). We find, concurring with surface transport equation models, that a critical factor for producing the patterns seen on the Sun is the inclination angle of the bipolar active regions. This work was supported by NSF grant 9416999.

Smith, A. A.; Snodgrass, H. B.

1999-05-01

263

Optical Reflection Study of Low-Dimensional Quantum Magnets  

NASA Astrophysics Data System (ADS)

We performed a linear optical reflection analysis of a low-dimensional, frustrated quantum magnet. Strongly-correlated low-dimensional systems are important for understanding spin-excitations, which form an important class of low-energy phenomena. Of particular interest are how these spin excitations arise and are then tuned by the environment (e.g. temperature, applied magnetic field). The temperature dependence of the reflection spectra from 215 K down to 4 K was measured. Magnetic field dependence of the reflection spectra from 0 T to 35 T was also measured. We will discuss the behavior of the reflection edge with temperature and magnetic field and its correlation with spin excitations.

Cherian, Judy; Tokumoto, Takahisa; Zhou, Haidong; McGill, Stephen

2013-03-01

264

Field Concentrator Based Resonant Magnetic Sensor  

Microsoft Academic Search

A novel resonant magnetic sensor based on the combination of a mechanical resonator and a magnetic field concentrator with two gaps is reported. In contrast to previous Lorentz force based resonant magnetic sensors, a high sensitivity is achieved without modulated driving current and complex feedback electronics. Furthermore, compared to magnetic moment based resonant magnetic sensors, the new concept requires no

S. Brugger; P. Simon; O. Paul

2006-01-01

265

Color Superconducting Matter in a Magnetic Field  

SciTech Connect

We investigate the effect of a magnetic field on cold dense quark matter using an effective model with four-Fermi interactions. We find that the gap parameters representing the predominant pairing between the different quark flavors show oscillatory behavior as a function of the magnetic field. We point out that due to electric and color neutrality constraints the magnetic fields as strong as presumably existing inside magnetars might induce significant deviations from the gap structure at a zero magnetic field.

Fukushima, Kenji [RIKEN BNL Research Center, Brookhaven National Laboratory, Upton, New York 11973 (United States); Warringa, Harmen J. [Department of Physics, Bldg. 510A, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2008-01-25

266

Trajectory and optical parameters in a non-linear stray field  

Microsoft Academic Search

A new optics for the main CERN Proton Synchrotron (CPS) magnet is modeled to allow a precise description of the ejected beams. For that purpose, field maps of the magnet have been measured for the various operational current settings. They include the central field, the end stray field and the lateral stray field. In order to get a functional form

Django Manglunki; M. Martini; I. Kirsten

1996-01-01

267

Numerical Simulation In Magnetic Drug Targeting. Magnetic Field Source Optimization  

Microsoft Academic Search

\\u000a This paper presents numerical simulation model and results on magnetic drug targeting therapy. The study aims at investigating\\u000a the aggregate blood - magnetic carrier flow interaction with an external magnetic field. Another objective was finding the\\u000a optimal magnetic field source configuration that provides for flows that best assist in magnetic drug targeting. In order\\u000a to evaluate the effects we used

A. Dobre; A. M. Morega

268

Magnetic field gradient measurement on magnetic cards using magnetic force microscopy  

NASA Astrophysics Data System (ADS)

The magnetic field gradients of magnetic stripe cards, which are developed for classifying magnetic particles used in magnetic particle inspections, have been measured using a magnetic force microscope (MFM). The magnetic force exerted on a MFM probe by the stray field emanating from the card was measured to determine the field gradients. The results are in good agreement with the field gradients estimated from the magnetizing field strengths used in the encoding process. .

Lo, C. C. H.; Leib, J.; Jiles, D. C.; Chedister, W. C.

2002-05-01

269

Magnetic fields in the early Universe  

Microsoft Academic Search

This review concerns the origin and the possible effects of magnetic fields in the early Universe. We start by providing the reader with a short overview of the current state of the art of observations of cosmic magnetic fields. We then illustrate the arguments in favor of a primordial origin of magnetic fields in the galaxies and in the clusters

Dario Grasso; Hector R. Rubinstein

2001-01-01

270

Primordial magnetic field limits from cosmological data  

SciTech Connect

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

Kahniashvili, Tina [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Department of Physics, Laurentian University, Ramsey Lake Road, Sudbury, Ontario P3E 2C (Canada); Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Tevzadze, Alexander G. [Abastumani Astrophysical Observatory, Ilia State University, 2A Kazbegi Ave, Tbilisi, GE-0160 (Georgia); Faculty of Exact and Natural Sciences, Tbilisi State University, 1 Chavchavadze Avenue, Tbilisi, GE-0128 (Georgia); Sethi, Shiv K. [McWilliams Center for Cosmology and Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, Pennsylvania 15213 (United States); Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Pandey, Kanhaiya [Raman Research Institute, Sadashivanagar, Bangalore 560080 (India); Ratra, Bharat [Department of Physics, Kansas State University, 116 Cardwell Hall, Manhattan, Kansas 66506 (United States)

2010-10-15

271

Penetration of plasma across a magnetic field  

NASA Astrophysics Data System (ADS)

Experiments were performed at the Nevada Terawatt Facility to investigate the plasma penetration across an externally applied magnetic field. In experiment, a short-pulse laser ablates a polyethylene laser target, producing a plasma which interacts with an external magnetic field. The mechanism which allows the plasma to penetrate the applied magnetic field in experiment will be discussed.

Plechaty, C.; Presura, R.; Wright, S.; Neff, S.; Haboub, A.

2009-08-01

272

Magnetic field reversals in the Milky Way  

Microsoft Academic Search

Radio observations of nearby spiral galaxies have tremendously enhanced our knowledge of their global magnetic field distributions. Recent theoretical developments in the area of dynamos have also helped in the interpretation of magnetic field data in spiral galaxies. When it comes to the magnetic field in the Milky Way galaxy, our position in the Milky Way's galactic disk hinders our

J. P. Vallee

1996-01-01

273

Transmission line magnetic fields; Measurements and calculations  

Microsoft Academic Search

Recent controversy over 60 Hz magnetic fields has heightened public awareness of overhead transmission lines. As a result, there is increasing motivation to study the magnetic fields form transmission lines. The most cost effective means to conduct research into transmission line magnetic fields is with computer or reduced-scale line models. However, from the standpoint of public perception and acceptance, it

B. A. Clairmont; G. B. Johnson; J. H. Dunlap

1992-01-01

274

Primordial magnetic field limits from cosmological data  

NASA Astrophysics Data System (ADS)

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

Kahniashvili, Tina; Tevzadze, Alexander G.; Sethi, Shiv K.; Pandey, Kanhaiya; Ratra, Bharat

2010-10-01

275

The coherence of multifrequency optical fields  

NASA Astrophysics Data System (ADS)

An analysis of the generalized coherence of multifrequency optical fields is given, both in terms of observable quantities (coherence functions) and in terms of field quantities (analytical signal and amplitude spectral density of the field). The spectral structure of the generalized coherence function for a widespread class of multifrequency optical fields is given. Experimental results obtained by interferometrical investigation of the generalized coherence of such fields are presented.

Tudor, Tiberiu S.

2004-06-01

276

Evolution of normal pulsar magnetic fields  

NASA Astrophysics Data System (ADS)

Results and new progress of the origin and evolution of pulsar magnetic fields are reviewed. Lots of models about how such strong magnetic fields were generated, mainly two kinds of structures were proposed for initial magnetic fields: fields confined in the cores and fields confined in the crusts of neutron stars. No consensus has been reached on whether the magnetic fields decay or not, despite some observational evidence for the evolution of magnetic fields. The discrepancy between characteristic ages and kinematic ages indicates that the magnetic fields decay exponentially. On the other hand, the braking indices of several young pulsars and the comparison between pulsar characteristic ages and the ages of associated supernova remnants suggest that the magnetic fields of young pulsars grow like a power-law. Pulsar population synthesis is one of the most important methods to investigate the evolution of magnetic fields. Many simulations show that if magnetic fields do decay exponentially, the e-folding decay time should be 100 Myr or longer. The numerical calculations of the Ohmic decay in the crust indicate that the scenario of exponential decay is oversimple, and the evolution could be divided into four possible phases approximately: exponential decay, no decay, power-law decay and exponential decay again. The model of magnetic fields expulsion induced by spin-down suggests that the magnetic fields decay only in a period between 107yr and 108yr.

Sun, Xiaohui; Han, Jinlin

2002-06-01

277

Periodic rotation of magnetization in a non-centrosymmetric soft magnet induced by an electric field  

NASA Astrophysics Data System (ADS)

The control of magnetism with an electric field is a challenging area with the potential to affect fields related to magnetic data storage, sensors and magnetic random access memory. Although there are some successful examples of such control based on the use of magnetic metals and semiconductors, energy loss caused by current flow is a problem that needs to be addressed. In particular, the repeatable control of magnetization with an electric field can be disturbed by joule heat loss. In this regard, non-centrosymmetric insulating magnets are good candidates for controlling magnetization without energy loss, in which the linear magnetoelectric effect has an essential role. Moreover, such magnets exhibit an unconventional magneto-optical effect, which allows the time-resolved detection of the magnetization direction. Here, we show a periodic oscillation of the magnetization direction by +/-20? in a non-centrosymmetric soft magnet (Cu,Ni)B2O4, which is induced by an a.c. electric field of 2kHz. The present study provides a strategy for identifying materials in which the magnetization direction can be modulated at high speed with an electric field.

Saito, M.; Ishikawa, K.; Konno, S.; Taniguchi, K.; Arima, T.

2009-08-01

278

Magnetic-field-dependent excitation transfer in quantum wells of diluted magnetic semiconductor  

NASA Astrophysics Data System (ADS)

We studied the excitation transfer in double quantum wells of a diluted magnetic semiconductor using a scanning near-field optical microscope at 7 K in external magnetic fields up to 9 T. In each quantum well, local energy minima are generated by local fluctuation of layer thickness and doping concentration of magnetic components. Excitons relax into the local energy minima and transfer between the minima via near-field optical interactions even across quantum wells toward stable sites at which to localize. We measured the intensity maps of near-field photoluminescence with spatial resolution estimated to be 30 nm under varying external magnetic fields. The measurement position reproducibility was confirmed by scanning tunneling microscope images. Analysis of the maps derived the magnetic-field dependence of the typical size of exciton-localization sites for each quantum well. Based on these results, we investigated the excitation transfer between the two quantum wells lying in different layers of the double quantum well system, and showed that the exciton transfer takes place at the two specific applied magnetic-field intensities that result in the crossing of Zeeman-split energy levels of the two different wells. We concluded that both the localization and the inter-quantum-well transfer of excitons are able to be controlled by an external magnetic field. This provides the basis for functional devices operating without any wiring.

Uchiyama, K.; Kubota, S.; Matsumoto, T.; Kobayashi, K.; Hori, H.

2013-10-01

279

Near-field magneto-optical microscopy in collection and illumination mode  

Microsoft Academic Search

We present a new design and the application of a near-field magneto-optical microscope, which combines the operation in the collection (PSTM) or illumination mode (NSOM) and the simultaneous application of an external magnetic field. Magnetic information is obtained via polarisation contrast showing the relative orientation of the magnetisation in magnetic thin films and microstructures due to the Faraday effect in

Frank Matthes; Hubert Brückl; Günter Reiss

1998-01-01

280

Crustal Magnetic Fields of Terrestrial Planets  

NASA Astrophysics Data System (ADS)

Magnetic field measurements are very valuable, as they provide constraints on the interior of the telluric planets and Moon. The Earth possesses a planetary scale magnetic field, generated in the conductive and convective outer core. This global magnetic field is superimposed on the magnetic field generated by the rocks of the crust, of induced (i.e. aligned on the current main field) or remanent (i.e. aligned on the past magnetic field). The crustal magnetic field on the Earth is very small scale, reflecting the processes (internal or external) that shaped the Earth. At spacecraft altitude, it reaches an amplitude of about 20 nT. Mars, on the contrary, lacks today a magnetic field of core origin. Instead, there is only a remanent magnetic field, which is one to two orders of magnitude larger than the terrestrial one at spacecraft altitude. The heterogeneous distribution of the Martian magnetic anomalies reflects the processes that built the Martian crust, dominated by igneous and cratering processes. These latter processes seem to be the driving ones in building the lunar magnetic field. As Mars, the Moon has no core-generated magnetic field. Crustal magnetic features are very weak, reaching only 30 nT at 30-km altitude. Their distribution is heterogeneous too, but the most intense anomalies are located at the antipodes of the largest impact basins. The picture is completed with Mercury, which seems to possess an Earth-like, global magnetic field, which however is weaker than expected. Magnetic exploration of Mercury is underway, and will possibly allow the Hermean crustal field to be characterized. This paper presents recent advances in our understanding and interpretation of the crustal magnetic field of the telluric planets and Moon.

Langlais, Benoit; Lesur, Vincent; Purucker, Michael E.; Connerney, Jack E. P.; Mandea, Mioara

2010-05-01

281

Nuclear magnetic resonance apparatus for pulsed high magnetic fields  

NASA Astrophysics Data System (ADS)

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

Meier, Benno; Kohlrautz, Jonas; Haase, Jürgen; Braun, Marco; Wolff-Fabris, Frederik; Kampert, Erik; Herrmannsdörfer, Thomas; Wosnitza, Joachim

2012-08-01

282

Magnetic Fields in the Milky Way, Derived from Radio Continuum Observations and Faraday Rotation Studies  

Microsoft Academic Search

Magnetic fields are found everywhere in our Universe. We know that our Earth possesses a dipolar magnetic field. Magnetic\\u000a fields have been observed on the Sun either as optical streamers during solar eclipses and by using remote sensing methods.\\u000a Magnetic fields of the solar planets have been studied in situ by measurements made by magnetometers on various spacecraft.\\u000a Stars, supernova

Richard Wielebinski

283

Near Field Spectroscopy of Quantum Dots Under Magnetic Field  

Microsoft Academic Search

We present the basic steps for the study of the linear near field absorption spectra of semiconductor quantum dots under magnetic field of variable orientation. We show that the application of the magnetic field alone is sufficient to induce -increasing the spot illuminated by the near field probe- interesting features to the absorption spectra.

Anna Zora; Constantinos Simserides; Georgios Triberis

2005-01-01

284

Near Field Spectroscopy of Quantum Dots Under Magnetic Field  

Microsoft Academic Search

We present the basic steps for the study of the linear near field absorption spectra of semiconductor quantum dots under magnetic field of variable orientation. We show that the application of the magnetic field alone is sufficient to induce -increasing the spot illuminated by the near field probe- interesting features to the absorption spectra.

Anna Zora; Constantinos Simserides; Georgios Triberis

2004-01-01

285

The origins of lunar crustal magnetic fields  

NASA Astrophysics Data System (ADS)

This thesis is devoted to understanding the origins of lunar crustal magnetism. We wish to understand the processes which have created and modified the crustal magnetic field distribution that we observe today, and to determine whether the Moon ever had an active magnetohydrodynamic dynamo. Previously, our only measurements of lunar magnetic fields came from the Explorer 35 and Apollo missions. Data coverage was incomplete, but sufficient to establish some systematics of the crustal field distribution. With new data from the Magnetometer and Electron Reflectometer instrument on Lunar Prospector, we have generated the first completely global maps of the lunar crustal fields. We use measurements of electrons magnetically reflected above the lunar surface, which we then correct for the effects of electrostatic fields (which also reflect electrons), and convert to estimates of surface magnetic fields. The resulting global map shows that impact basins and craters (especially the youngest) generally have low magnetic fields, suggesting impact demagnetization, primarily by shock effects. A secondary signature of some large lunar basins (especially older ones) is the presence of a more localized central magnetic anomaly. Meanwhile, the largest regions of strong crustal fields lie antipodal to young large impact basins, suggesting shock remanent magnetization due to a combination of antipodal focussing of seismic energy and/or ejecta and plasma compression of ambient magnetic fields. Smaller regions of strong magnetic fields are sometimes associated with basin ejecta, and basin and crater ejecta terranes have the strongest average fields outside of the antipodal regions. This implies that impact-generated magnetization may extend beyond the antipodal regions. The antipodal, non-antipodal, and central basin magnetic fields, as well as returned samples, can all be used to estimate the lunar magnetic field history and place constraints on a possible lunar dynamo. All of these quantities provide evidence for stronger magnetic fields early in the Moon's history, and thereby suggest the existence of an ancient core dynamo.

Halekas, Jasper S.

286

Magnetic field observations in Comet Halley's coma  

NASA Astrophysics Data System (ADS)

During the encounter with Comet Halley, the magnetometer (MISCHA) aboard the Vega 1 spacecraft observed an increased level of magnetic field turbulence, resulting from an upstream bow wave. Both Vega spacecraft measured a peak field strength of 70-80 nT and observed draping of magnetic field lines around the cometary obstacle. An unexpected rotation of the magnetic field vector was observed, which may reflect either penetration of magnetic field lines into a diffuse layer related to the contact surface separating the solar-wind and cometary plasma, or the persistence of pre-existing interplanetary field structures.

Riedler, W.; Schwingenschuh, K.; Yeroshenko, Ye. G.; Styashkin, V. A.; Russell, C. T.

1986-05-01

287

Magnetic field modulation of intense surface plasmon polaritons.  

PubMed

We present correlated experimental and theoretical studies on the magnetic field modulation of Surface Plasmon Polaritons (SPPs) in Au/Co/Au trilayers. The trilayers were grown by sputter deposition on glass slides with the Co films placed at different distances from the surface and with different thickness. We show that it is possible to tailor Au/Co/Au trilayers with the critical thickness needed for optimum excitation of SPPs leading to large localized electromagnetic fields. The modification of the SPP wave vector by externally applied magnetic fields was investigated by measuring the magneto-optical activity in transverse configuration. In addition, using magneto-optics as a tool we determined the spatial distribution of the SPP generated electromagnetic fields within Au/Co/Au samples by analyzing the field-dependent optical response, demonstrating that it is possible to excite SPPs that exhibit large electromagnetic fields that are also magneto-optically active and therefore can be modulated by externally applied magnetic fields. PMID:20588615

Clavero, C; Yang, K; Skuza, J R; Lukaszew, R A

2010-04-12

288

Magnetic field seeding by galactic winds  

Microsoft Academic Search

The origin of intergalactic magnetic fields is still a mystery and several scenarios have been proposed so far: among them, primordial phase transitions, structure-formation shocks and galactic outflows. In this work, we investigate how efficiently galactic winds can provide an intense and widespread `seed' magnetization. This may be used to explain the magnetic fields observed today in clusters of galaxies

Serena Bertone; Corina Vogt; Torsten Enßlin

2006-01-01

289

Invited Safety of Strong, Static Magnetic Fields  

Microsoft Academic Search

Issues associated with the exposure of patients to strong, static magnetic fields during magnetic resonance imaging (MRI) are reviewed and discussed. The history of human exposure to magnetic fields is reviewed, and the contra- dictory nature of the literature regarding effects on human health is described. In the absence of ferromagnetic for- eign bodies, there is no replicated scientific study

John F. Schenck

2000-01-01

290

Intergalactic Magnetic Fields from Quasar Outflows  

Microsoft Academic Search

Outflows from quasars inevitably pollute the intergalactic medium (IGM) with magnetic fields. The short-lived activity of a quasar leaves behind an expanding magnetized bubble in the IGM. We model the expansion of the remnant quasar bubbles and calculate their distribution as a function of size and magnetic field strength at different redshifts. We generically find that by a redshift z~3,

Steven R. Furlanetto; Abraham Loeb

2001-01-01

291

Magnetic fields in Local Group dwarf irregulars  

Microsoft Academic Search

Aims: We wish to clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and to assess the role of dwarf galaxies in the magnetization of the Universe. Methods: We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100-m

K. T. Chyzy; M. Wezgowiec; R. Beck; D. J. Bomans

2011-01-01

292

Deformation of Water by a Magnetic Field  

ERIC Educational Resources Information Center

|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

293

Baking a magnetic-field display  

NASA Astrophysics Data System (ADS)

Copy machine developer powder is an alternative for creating permanent displays of magnetic fields. A thin layer of developer powder on a sheet of paper placed over a magnet can be baked in the oven, producing a lasting image of a magnetic field.

Cavanaugh, Terence; Cavanaugh, Catherine

1998-02-01

294

Exploring Magnetic Fields with a Compass  

ERIC Educational Resources Information Center

|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…

Lunk, Brandon; Beichner, Robert

2011-01-01

295

Cluster magnetic fields from galactic outflows  

Microsoft Academic Search

We performed cosmological, magnetohydrodynamical simulations to follow the evolution of magnetic fields in galaxy clusters, exploring the possibility that the origin of the magnetic seed fields is galactic outflows during the starburst phase of galactic evolution. To do this, we coupled a semi-analytical model for magnetized galactic winds as suggested by Bertone, Vogt & Enßlin to our cosmological simulation. We

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

2009-01-01

296

Sub arcsec evolution of solar magnetic fields  

Microsoft Academic Search

Context: .The evolution of the concentrated magnetic field in flux tubes is one challenge of the nowadays Solar physics which requires time sequence with high spatial resolution. Aims: .Our objective is to follow the properties of the magnetic concentrations during their life, in intensity (continuum and line core), magnetic field and Doppler velocity. Methods: .We have observed solar region NOAA

Th. Roudier; J. M. Malherbe; J. Moity; S. Rondi; P. Mein; Ch. Coutard

2006-01-01

297

An Extraordinary Magnetic Field Map of Mars  

NASA Astrophysics Data System (ADS)

A new global map of the magnetic field of Mars, with an order of magnitude improved sensitivity to crustal magnetization, is derived from Mars Global Surveyor mapping orbit magnetic field data. With this comes greatly improved spatial resolution and geologic intrpretation.

Connerney, J. E. P.; Acuna, M. H.; Ness, N. F.; Mitchell, D. L.; Lin, R. P.

2004-03-01

298

Magnetic optics for proton radiography  

Microsoft Academic Search

High energy protons of 10 to 50 GeV can be used to radiograph dense objects. Because the transmitted beam particles undergo multiple Coulomb scattering (MCS) in the object, a magnetic lens system is used to focus the particles exiting each point of the object onto a distant image plane. Without the lens, the MCS would seriously blur the radiographic image.

C. Thomas Mottershead; John D. Zumbro

1997-01-01

299

Rotating magnetic beacons magnetic field strength size in SAGD  

Microsoft Academic Search

Rotation magnetic beacons magnetic field strength is very important to drill parallel horizontal twin wells in steam assisted\\u000a gravity drainage (SAGD). This paper analyzes a small magnet with a diameter of 25.4 mm. At each end, there is a length of\\u000a 12.6 mm with permanent magnet, and in the middle, there is a length of 78mm with magnetic materials. The

Bing Tu; Desheng Li; Enhuai Lin; Bin Luo; Jian He; Lezhi Ye; Jiliang Liu; Yuezhong Wang

2010-01-01

300

Novel optical devices based on the transmission properties of magnetic fluid and their characteristics  

NASA Astrophysics Data System (ADS)

Magnetic fluid has many unique optical properties. It has numerous potential applications in developing optical devices because of its versatile optical properties. This paper summarizes the physical origins and control mechanisms of the MF transmission properties, and the related optical devices based on the transmission properties of magnetic fluid. In recent years, there are many applications in optical information communication and sensing technology, such as optical switches, tunable optical gratings, coarse wavelength-division multiplexing, magnetic-field sensors, current sensor. The qualitative and quantitative analysis about the physical configuration, the operating principle, and the characteristics of those optical devices are given. The valuable potential problems and the solutions that are related to optical properties and optical devices based on magnetic fluid are expounded in detail, and potential new types of MF-based optical devices are proposed. It can be concluded that the transmission properties of MF will be improved greatly, and the characteristics of present optical devices based on magnetic fluid will be made better continually and it will play an important role in the fields of optical information communication and sensing technology.

Zhao, Yong; Lv, Riqing; Zhang, Yuyan; Wang, Qi

2012-09-01

301

Optical design of optical switches for diverse field spectroscopy  

NASA Astrophysics Data System (ADS)

Diverse field spectroscopy is a new concept in which any part of a field can be optically captured and send to the entrance slit of a spectrograph. It is more general than integral field spectroscopy, multi-object spectroscopy and even multi-integral-field spectroscopy which combine the two as in the KMOS instrument. In diverse field spectroscopy, point sources and extended sources are simultaneously optically captured in an optimal way that fully use the spectrograph for only the regions of interest; as opposed to multi-integral-field spectroscopy where rectangular or square fields are fully captured, the capturing mechanism will follow the complex shapes of the sources removing any useless field which can then be use for other sources instead or permit to observe larger sources. Optical switches can be programmed to transmit any subset of the spatial elements of a field to the spectrograph. We present the different optical designs of switches that we made, some using micromirrors arrays, others small lenses. We also present conceptual designs of low cost projects for Échelle spectrographs as the SALT HRS and for the FMOS spectrographs on SUBARU. A critical aspect of the designs is to minimize the cost so that the switches can be mass-produced while maintaining high optical performances. A general discussion will be made of the relation between the total cost of the switch system plus spectrograph and the multiplex advantage with respect to an integral-field spectrograph giving the same performances.

Content, Robert; Murray, Graham J.; Allington-Smith, Jeremy R.

2010-07-01

302

Electric-field control of magnetic domain wall motion and local magnetization reversal  

NASA Astrophysics Data System (ADS)

Spintronic devices currently rely on magnetic switching or controlled motion of domain walls by an external magnetic field or spin-polarized current. Achieving the same degree of magnetic controllability using an electric field has potential advantages including enhanced functionality and low power consumption. Here we report on an approach to electrically control local magnetic properties, including the writing and erasure of regular ferromagnetic domain patterns and the motion of magnetic domain walls, in CoFe-BaTiO3 heterostructures. Our method is based on recurrent strain transfer from ferroelastic domains in ferroelectric media to continuous magnetostrictive films with negligible magnetocrystalline anisotropy. Optical polarization microscopy of both ferromagnetic and ferroelectric domain structures reveals that domain correlations and strong inter-ferroic domain wall pinning persist in an applied electric field. This leads to an unprecedented electric controllability over the ferromagnetic microstructure, an accomplishment that produces giant magnetoelectric coupling effects and opens the way to electric-field driven spintronics.

Lahtinen, Tuomas H. E.; Franke, Kévin J. A.; van Dijken, Sebastiaan

2012-02-01

303

Unique topological characterization of braided magnetic fields  

NASA Astrophysics Data System (ADS)

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

Yeates, A. R.; Hornig, G.

2013-01-01

304

Optical magnetism in metal nanoforests  

NASA Astrophysics Data System (ADS)

We discuss the optical properties metal nanoforests - a composite metamaterial in which silver nanowires are aligned inside a finite-thickness dielectric host medium. Using finite-element modelling and a self-consistent extraction of effective-medium parameters, we find that this structure can enable an effective optical diamagnetic response that is orders of magnitude stronger compared to that of naturally occurring diamagnetic materials. Our analysis reveals that there is a frequency region where the nanoforest exhibits strong diamagnetic response while simultaneously allowing for high transmission of incident electromagnetic waves. Our analysis shows that the phenomena are robust to the presence of disorder, in the occurrence of which it can still facilitate high figure-of-merit diamagnetic responses.

Cook, James; Tsakmakidis, Kosmas; Hess, Ortwin

2009-08-01

305

Polarization-independent magnetic control of the light phase in a chiral optical fiber  

NASA Astrophysics Data System (ADS)

The proposition is made to fine-tune the phase of an unpolarized guided mode in a chiral optical waveguide, or fiber, by a static magnetic field applied in the direction of the light propagation. The core of the fiber should consist of randomly oriented chiral molecules, and the magnetic field-induced change of the refractive index would be due to the magnetochiral effect [1]. Although the magnetochiral birefringence is very small for magnetic field strengths obtainable under routine laboratory conditions, the induced phase shift for a given magnetic field should be maximized by increasing the pathlength of light inside the field. This would be technically achievable by winding the optical fiber axially many times around the electric solenoid that generates the magnetic field, in such a way that the path of the light inside the fiber follows closely and over a distance as long as possible the magnetic induction lines.

Wagnière, Georges H.

2012-10-01

306

Boston University Physics Applets: Magnetic Field Demonstration  

NSDL National Science Digital Library

This web page is an interactive physics simulation that explores magnetic fields. The user can add currents coming into or out of a simulated grid, and see the fields created. There is also a selection of pre-created fields, including bar magnets, loops, opposing magnets, and coils in uniform fields. Double-clicking on any point displays the full loop created by the magnetic field. This item is part of a larger collection of introductory physics simulations developed by the author. This is part of a collection of similar simulation-based student activities.

Duffy, Andrew

2008-08-23

307

Bipolar pulse field for magnetic refrigeration  

DOEpatents

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

308

Bipolar pulse field for magnetic refrigeration  

DOEpatents

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

Lubell, M.S.

1994-10-25

309

Near-Field Magnetic Dipole Moment Analysis.  

National Technical Information Service (NTIS)

This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective...

P. K. Harris

2003-01-01

310

Constant Current Source for Stable Magnetic Fields.  

National Technical Information Service (NTIS)

An electronic control system for stabilization of currents in magnetic fields is described. Three superimposed control stages with different characteristics provide optimum elimination of all interfering factors. The use of electrostatic and magnetic shie...

K. Weyand

1976-01-01

311

Transient horizontal magnetic fields in solar plage regions  

NASA Astrophysics Data System (ADS)

Aims:We report the discovery of isolated, small-scale emerging magnetic fields in a plage region with the Solar Optical Telescope aboard Hinode. Methods: Spectro-polarimetric observations were carried out with a cadence of 34 s for the plage region located near disc center. The vector magnetic fields are inferred by Milne-Eddington inversion. Results: The observations reveal widespread occurrence of transient, spatially isolated horizontal magnetic fields. The lateral extent of the horizontal magnetic fields is comparable to the size of photospheric granules. These horizontal magnetic fields seem to be tossed about by upflows and downflows of the granular convection. We also report an event that appears to be driven by the magnetic buoyancy instability. We refer to buoyancy-driven emergence as type 1 and convection-driven emergence as type 2. Although both events have magnetic field strengths of about 600 G, the filling factor of type 1 is a factor of two larger than that of type 2. Conclusions: Our finding suggests that the granular convection in the plage regions is characterized by a high rate of occurrence of granular-sized transient horizontal fields.

Ishikawa, R.; Tsuneta, S.; Ichimoto, K.; Isobe, H.; Katsukawa, Y.; Lites, B. W.; Nagata, S.; Shimizu, T.; Shine, R. A.; Suematsu, Y.; Tarbell, T. D.; Title, A. M.

2008-04-01

312

Theory and application of magnetically shaped liquid optical surfaces  

NASA Astrophysics Data System (ADS)

This work describes a new class of flexible optical materials that can be dynamically shaped in a magnetic field. The materials are a combination of a superparamegnetic colloid known as a ferrofluid, coated with a Metal Liquid-Like Film (MELLF) to provide a reflective surface. Without the mechanical constraints of solid optical surfaces, liquid mirrors offer greatly improved stroke. The ease of fabrication of liquid optical surfaces also offers the potential for substantial cost savings over traditional materials. I begin by presenting an overview of current deformable mirror technology used in adaptive optics and then describe the underlying magnetic and hydrodynamic theory of magnetic liquid mirrors. The design and testing of a prototype deformable mirror is discussed in detail and simulations of the mirror shape under various conditions are presented. A variety of magnetic fluids were characterized to determine response time and maximum deformation. Strokes in excess of 20 mu m were demonstrated at frequencies up to 10 Hz with no measurable actuator hysteresis. The reflectivity of coated ferrofluids was measured to determine temporal and spatial variations. Coated ferrofluids were found to have stable reflectivity for periods of 14 days and deposition techniques being developed by chemists at Universite Laval show considerable promise to extend this duration. Preliminary experimental results and simulations of wavefront control are presented. The suitability of magnetic liquid mirrors for a number of adaptive optics applications is discussed in terms of the experimental results with the prototype mirror described earlier. Finally, a number of methods to improve the performance of magnetic liquid mirrors are proposed.

Laird, Philip Rodney

313

THE EARTH'S YOUNG MAGNETIC FIELD  

Microsoft Academic Search

Invisible lines of magnetic force enclose our planet in what scientists call adipolarmagneticfield. Today these lines go from magnetic south to magnetic north, which are offset a few degrees from the geographic poles. Some minerals, like magnetite, can \\

Trevor Major

314

Optical activity in media with noncoplanar magnetization distribution  

SciTech Connect

Natural optical activity in magnetic media for which the exchange interaction dominates is studied theoretically. It is shown using a phenomenological theory that the optical activity effect can be observed in a medium with a nonuniform noncoplanar magnetization distribution without an inversion center. A microscopic theory of the optical activity is constructed for a medium with a helicoidal magnetic structure.

Karashtin, E. A., E-mail: notfromme@yandex.ru; Udalov, O. G.; Fraerman, A. A. [Russian Academy of Sciences, Institute of Microstructure Physics (Russian Federation)

2009-12-15

315

Arc Discharges in a Curved Magnetic Field.  

National Technical Information Service (NTIS)

An experiment on arc discharges in hydrogen in a curved magnetic field is described. For a few milliseconds the discharge current flowed between two electrodes along the field lines of a toroidal magnetic field over an angle of 258 deg. The plasma was not...

F. C. Schueller

1974-01-01

316

Is the intergalactic magnetic field primordial?  

Microsoft Academic Search

We consider the various methods used to constrain the possible field strength of the present day intergalactic field and findB0(G)-10 as a probable upper bound. It is suggested that the observed intergalactic magnetic field might not be primordial in origin but rather the result of magnetic flux leakage from galaxies and clusters of galaxies.

Martin Beech

1985-01-01

317

Intergalactic magnetic field and galactic WARPS  

Microsoft Academic Search

An alternative explanation of galactic warps is proposed, in which the intergalactic magnetic field (IGMF) is responsible for these structures. The model predicts that, to be efficient, the magnetic field must have a direction not much different from 45 deg with the galactic plane. The required values of the field strength are uncertain, of about 10 nG, higher values being

E. Battaner; E. Florido; M. L. Sanchez-Saavedra

1990-01-01

318

Fiber Bragg Grating Magnetic Field Sensor  

Microsoft Academic Search

In this paper we demonstrate experimentally a magnetic field sensor using a fiber Bragg grating. The shift in the Bragg condition as a result of strain applied on the fiber mounted on a nickel base by the magnetic field gives an indirect measure of the field. The proposed method overcomes the need for long fiber lengths required in methods such

K. V. Madhav; K. Ravi Kumar; T. Srinivas; S. Asokan

2006-01-01

319

Is the intergalactic magnetic field primordial?  

NASA Astrophysics Data System (ADS)

The various methods used to constrain the possible field strength of the present day intergalactic field are considered, and Bzero (G) less than 10 to the -10th is found as a probable upper bound. It is suggested that the observed intergalactic magnetic field might not be primordial in origin but rather the result of magnetic flux leakage from galaxies and clusters of galaxies.

Beech, M.

1985-11-01

320

Magnetic resonance reversals in optically pumped alkali-metal vapor  

Microsoft Academic Search

We report an unusual phenomenon, peculiar sign reversals of the ground-state magnetic resonances and of the zero-dip resonance (Zeeman resonance at zero field) of optically pumped, alkali-metal vapors. These anomalies occur when a weak circularly polarized D1 laser light is tuned to pump atoms predominantly from the lower ground-state hyperfine multiplet. One can understand the signal reversals in a simple,

F. Gong; Y.-Y. Jau; W. Happer

2007-01-01

321

Static uniform magnetic fields and amoebae  

SciTech Connect

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

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

1997-03-01

322

Optical second harmonic generation in the centrosymmetric magnetic semiconductors EuTe and EuSe  

NASA Astrophysics Data System (ADS)

The magnetic europium chalcogenide semiconductors EuTe and EuSe are investigated by the spectroscopy of second harmonic generation (SHG) in the vicinity of the optical band gap formed by transitions involving the 4f and 5d electronic orbitals of the magnetic Eu2+ ions. In these materials with centrosymmetric crystal lattice the electric-dipole SHG process is symmetry forbidden so that no signal is observed in zero magnetic field. Signal appears, however, in applied magnetic field with the SHG intensity being proportional to the square of magnetization. The magnetic field and temperature dependencies of the induced SHG allow us to introduce a type of nonlinear optical susceptibility determined by the magnetic-dipole contribution in combination with a spontaneous or induced magnetization. The experimental results can be described qualitatively by a phenomenological model based on a symmetry analysis and are in good quantitative agreement with microscopic model calculations accounting for details of the electronic energy and spin structure.

Kaminski, B.; Lafrentz, M.; Pisarev, R. V.; Yakovlev, D. R.; Pavlov, V. V.; Lukoshkin, V. A.; Henriques, A. B.; Springholz, G.; Bauer, G.; Abramof, E.; Rappl, P. H. O.; Bayer, M.

2010-04-01

323

Classical Theory of Optical Near Field  

NASA Astrophysics Data System (ADS)

The main purpose of this chapter is to present the quasi-static picture of an optical field in the vicinity of small-scale material. The quasi-static picture depends on the fact that the induced boundary charge density dominates the optical near field of a small-scale material via Coulomb's law; therefore, such an optical near field is of a non-radiative or longitudinal nature. This simple physics leads to an intuitive understanding, even in complicated systems with magneto- and electro-optical effects. As prerequisites, the definitions of elementary concepts are given: "retardation effect," "diffraction limit," "near field," and "far field." Furthermore, two numerical methods are presented using the minimum degree of freedom of an electromagnetic field; one is described by the scalar potential adequate for a quasi-static system and the other by a dual vector potential for general optical systems. This chapter is restricted to linear optical effects and is a revised version of the article titled by "Classical Theory on Electromagnetic Near Field" in Progress in Nano-Electro-Optics II (Springer-Verlag Berlin Heidelberg, 2004).

Banno, Itsuki

324

Extraterrestrial Magnetic Fields: Achievements and Opportunities  

Microsoft Academic Search

The major scientific achievements associated with the measurement of magnetic fields in space over the past decade and a half are reviewed. Aspects of space technology relevant to magnetic-field observations are discussed, including the different types of magnetometers used and how they operate, problems arising from spacecraft-generated magnetic fields and the appropriate countermeasures that have been developed and on-board processing

EDWARD J. SMITHAND; Charles Sonett

1976-01-01

325

Modeling solar force-free magnetic fields  

Microsoft Academic Search

A class of nonlinear force-free magnetic fields is presented, described in terms of the solutions to a second-order, nonlinear ordinary differential equation. These magnetic fields are three-dimensional, filling the infinite half-space above a plane where the lines of force are anchored. They model the magnetic fields of the sun over active regions with a striking geometric realism. The total energy

B. C. Low; Y. Q. Lou

1990-01-01

326

Induced Magnetic Anisotropy of Ferrofluid Frozen in Magnetic Fields  

Microsoft Academic Search

The magnetization process of a ferrofluid whose carrier fluid is paraffin was investigated in the temperature range from 77 K to 300 K, as a function of the cooling field intensity and freezing rate. Phase transitions between the liquid and solid states can be simulated by using the ferrofluids as a magnetic probe. A uniaxial magnetic anisotropy was induced by

N. Inaba; H. Miyajima; S. Taketomi; S. Chikazumi

1989-01-01

327

Swarm: ESA's Magnetic Field Mission  

NASA Astrophysics Data System (ADS)

Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme, and is scheduled for launch in 2013. The objective of the Swarm mission is to provide the best-ever survey of the geomagnetic field and its temporal evolution using a constellation of 3 identical satellites. The Mission shall deliver data that allow access to new insights into the Earth system by improved scientific understanding of the Earth's interior and near-Earth electromagnetic environment. After launch and triple satellite release at an initial altitude of about 490 km, a pair of the satellites will fly side-by-side with slowly decaying altitude, while the third satellite will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations required to separate and model various sources of the geomagnetic field and near-Earth current systems. The mission science goals are to provide a unique view into Earth's core dynamics, mantle conductivity, crustal magnetisation, ionospheric and magnetospheric current systems and upper atmosphere dynamics - ranging from understanding the geodynamo to contributing to space weather. The scientific objectives and results from recent scientific studies will be presented. In addition the current status of the project, which is presently in the final stage of the development phase, will be addressed. A consortium of European scientific institutes is developing a distributed processing system to produce geophysical (Level 2) data products for the Swarm user community. The setup of the Swarm ground segment and the contents of the data products will be addressed. More information on Swarm can be found at www.esa.int/esaLP/LPswarm.html.

Plank, Gernot; Haagmans, Roger; Floberghagen, Rune; Menard, Yvon

2013-04-01

328

Magnetic superfluid state in the frustrated spinel oxide CdCr2O4 revealed by ultrahigh magnetic fields  

NASA Astrophysics Data System (ADS)

We investigated the magnetic-field-induced phases of a typical three-dimensional frustrated magnet, CdCr2O4, in magnetic fields of up to 120 T using both the electromagnetic induction method and magneto-optical spectroscopy of the d-d transitions and the exciton-magnon-phonon transitions. Anomalies were observed in the magneto-optical absorption intensity as well as the differential magnetization prior to a fully polarized magnetic phase, revealing a magnetic phase associated with changes in both the crystal and magnetic structures accompanied by the first-order phase transition. A magnetic superfluid state, such as an umbrella-like magnetic structure or a spin-nematic state, is proposed as a candidate for this phase, which is found universally in the series of chromium spinel oxides, ACr2O4 (A = Zn, Cd, Hg).

Miyata, Atsuhiko; Takeyama, Shojiro; Ueda, Hiroaki

2013-06-01

329

Magneto-optical studies of magnetization processes in high-Tc superconductors structure.  

SciTech Connect

Magneto-optical imaging is a powerful tool for nondestructive quality control and scientific research through visualization of magnetic fields around any magnetic flux or current carrying sample. It allows real time observations of domain structures and their transformations in magnetics, static and dynamic field patterns due to inhomogeneous currents in electric circuits and superconductors, and reveals distortions of the fields due to defects. In addition to qualitative pictures showing different details in the intensities of the magneto-optical images, one can obtain quantitative maps of field distributions and retrieve values of the underlying currents or magnetization variations. In this review we discuss the advantages of magneto-optics for studies of superconductors, show its place among other techniques, and report recent results in magneto-optical investigations of high temperature superconductors (HTS).

Vlasko-Vlasox, V. K.

1998-12-02

330

Five years of magnetic field management  

SciTech Connect

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

Durkin, C.J.; Fogarty, R.P.; Halleran, T.M.; Mark, Dr. D.A.; Mukhopadhyay, A.

1995-01-01

331

Quark matter in a strong magnetic field  

SciTech Connect

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

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

1996-07-01

332

Two dimensional frustrated magnets in high magnetic field  

NASA Astrophysics Data System (ADS)

Frustrated magnets in high magnetic field have a long history of offering beautiful surprises to the patient investigator. Here we present the results of extensive classical Monte Carlo simulations of a variety of models of two dimensional magnets in magnetic field, together with complementary spin wave analysis. Striking results include (i) a massively enhanced magnetocaloric effect in antiferromagnets bordering on ferromagnetic order, (ii) a route to an m = 1/3 magnetization plateau on a square lattice, and (iii) a cascade of phase transitions in a simple model of AgNiO2.

Seabra, L.; Shannon, N.; Sindzingre, P.; Momoi, T.; Schmidt, B.; Thalmeier, P.

2009-01-01

333

The Magnetic Fields of the Quiet Sun  

NASA Astrophysics Data System (ADS)

This work reviews our understanding of the magnetic fields observed in the quiet Sun. The subject has undergone a major change during the last decade (quiet revolution), and it will remain changing since the techniques of diagnostic employed so far are known to be severely biased. Keeping these caveats in mind, our work covers the main observational properties of the quiet Sun magnetic fields: magnetic field strengths, unsigned magnetic flux densities, magnetic field inclinations, as well as the temporal evolution on short time-scales (loop emergence), and long time-scales (solar cycle). We also summarize the main theoretical ideas put forward to explain the origin of the quiet Sun magnetism. A final prospective section points out various areas of solar physics where the quiet Sun magnetism may have an important physical role to play (chromospheric and coronal structure, solar wind acceleration, and solar elemental abundances).

Sánchez Almeida, J.; Martínez González, M.

2011-04-01

334

Optical Properties of Magnetic Semiconductors  

NASA Astrophysics Data System (ADS)

We have employed Infrared Sprectroscopy (IR) and Ellipsometry to explore the band structure of thin films and digitally doped superlattices of Ga1-xMnxAs, prepared in the group of D.D. Awschalom (UCSB). These measurements reveal the important role played by the Mn induced impurity band in the band structure and ferromagnetism of Ga1-xMnxAs. Our IR work on Digital Ferromagnetic Heterostructures reveals a unique ability to tune their optical properties as well as their intrinsic electronic structure without changing the doping/defect level. This work is in collaboration with E.J. Singley, D.N. Basov (University of California, San Diego) J. Stephens, R.K. Kawakami, and D.D. Awschalom(University of California, Santa Barbara).

Burch, Kenneth

2005-03-01

335

Comparative numerical analysis of magnetic and optical radiation propagation in adult human head  

NASA Astrophysics Data System (ADS)

In this work, magnetic and optical propagation in human head are modeled by FDTD and Monte Carlo methods. Both of them use a realistic high-resolution three-dimensional human head mesh. The numerical methods are applied to the analysis of magnetic and optical radiation distribution in the brain using different sources. The results show the characteristics of both types of stimulation, and highlight the spatial selectivity achieved by optical sources, which entails a high potential for illuminating specific brain regions. The presented approach can be applied for predictive purposes in magnetic stimulation techniques and in the emerging field of optical brain stimulation.

Ortega-Quijano, Noé; Fanjul-Vélez, Félix; Salas-García, Irene; Arce-Diego, José Luis

2013-06-01

336

Motion Field and Optical Flow: Qualitative Properties.  

National Technical Information Service (NTIS)

The optical flow, a 2-D field that can be associated with the variation of the image brightness pattern, and the 2-D motion field, the projection on the image plane of the 3-D velocity field of a moving scene, are in general different, unless very special...

A. Verri T. Poggio

1986-01-01

337

PRINCIPLE OF CORRECTION OF ASYMMETRIC MAGNETIC FIELDS IN BENDING MAGNETS  

Microsoft Academic Search

The generation of a high quality electron beam by a race- track microtron (RTM) requires highly precise magnetic fields in the two reversing magnets. At the RTM cascade MAMI (Mainz Microtron), a precision of 10 ?4 for the ver- tical field component By was achieved by symmetrical sur- face coils placed at the upper and lower pole surface in each

F. Hagenbuck; P. Jennewein; K.-H. Kaiser; H.-J. Kreidel; U. Ludwig-Mertin; M. Seidl

2002-01-01

338

Applications of Near Field Optical Microscopy  

Microsoft Academic Search

\\u000a Scanning Near-field Optical Microscopy (SNOM), based on metal coated adiabatically tapered fibres, combined with shear force\\u000a feedback and operated in illumination mode, has proven to be the most powerful SNOM arrangement, because of its true localisation\\u000a of the optical interaction, its true optical contrast (fluorescence, polarisation, etc.) and its sensitivity down to the single\\u000a molecular level. We present the first

NIEK VAN HULST; Marco Moers; Erik Borgonjen

339

Resonant Magnetic Field Sensors Based On MEMS Technology  

PubMed Central

Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to detect external magnetic fields through the displacement of resonant structures, which are measured with optical, capacitive, and piezoresistive sensing techniques. From these, the optical sensing presents immunity to electromagnetic interference (EMI) and reduces the read-out electronic complexity. Moreover, piezoresistive sensing requires an easy fabrication process as well as a standard packaging. A description of the operation mechanisms, advantages and drawbacks of each sensor is considered. MEMS magnetic field sensors are a potential alternative for numerous applications, including the automotive industry, military, medical, telecommunications, oceanographic, spatial, and environment science. In addition, future markets will need the development of several sensors on a single chip for measuring different parameters such as the magnetic field, pressure, temperature and acceleration.

Herrera-May, Agustin L.; Aguilera-Cortes, Luz A.; Garcia-Ramirez, Pedro J.; Manjarrez, Elias

2009-01-01

340

Resonant Magnetic Field Sensors Based On MEMS Technology.  

PubMed

Microelectromechanical systems (MEMS) technology allows the integration of magnetic field sensors with electronic components, which presents important advantages such as small size, light weight, minimum power consumption, low cost, better sensitivity and high resolution. We present a discussion and review of resonant magnetic field sensors based on MEMS technology. In practice, these sensors exploit the Lorentz force in order to detect external magnetic fields through the displacement of resonant structures, which are measured with optical, capacitive, and piezoresistive sensing techniques. From these, the optical sensing presents immunity to electromagnetic interference (EMI) and reduces the read-out electronic complexity. Moreover, piezoresistive sensing requires an easy fabrication process as well as a standard packaging. A description of the operation mechanisms, advantages and drawbacks of each sensor is considered. MEMS magnetic field sensors are a potential alternative for numerous applications, including the automotive industry, military, medical, telecommunications, oceanographic, spatial, and environment science. In addition, future markets will need the development of several sensors on a single chip for measuring different parameters such as the magnetic field, pressure, temperature and acceleration. PMID:22408480

Herrera-May, Agustín L; Aguilera-Cortés, Luz A; García-Ramírez, Pedro J; Manjarrez, Elías

2009-09-30

341

Magnetic-field effects in non-magnetic glasses  

NASA Astrophysics Data System (ADS)

Recently, it was found that the multi-component glass a-BaO-Al2O3-SiO2 exhibits unusual magnetic properties at very low temperatures. Thus the question arises whether this is a specialty of that particular glass or a more general phenomenon. We report here on our studies of the magnetic-field dependence of the dielectric properties of the borosilicate glass BK7 which contains only a negligible amount of magnetic impurities. Since this glass also responds sensitively to magnetic fields, our investigations demonstrate that the reaction of glasses to magnetic fields is not caused by magnetic impurities but reflects a more general phenomenon. In addition, we have observed that the variation of the dielectric constant and the loss angle with magnetic field depend on the amplitude of the electric field that is used to measure the glass capacitance. We present the data and discuss possible origins of the magnetic-field phenomena in non-magnetic glasses.

Wohlfahrt, M.; Strehlow, P.; Enss, C.; Hunklinger, S.

2001-12-01

342

Magnetohydrodynamics of the Earth'S Magnetic Field.  

National Technical Information Service (NTIS)

A survey of observational and theoretical work pertaining to the origin of planetary magnetic fields is given with special emphasis on the dynamo theory which attempts to explain these fields as arising from magnetohydrodynamic regenerative action. Some p...

G. Venezian

1967-01-01

343

Cosmic Rays in the Earth'S Magnetic Field.  

National Technical Information Service (NTIS)

Studies are presented of the behavior of cosmic rays in the earth's magnetic field. It discusses the theory of motion of charged particles in an idealized field model and presents results of trajectory calculations of asymptotic directions and cutoff rigi...

L. I. Dorman V. S. Smirnov M. I. Tyasto

1973-01-01

344

The Evolution of the Earth's Magnetic Field.  

ERIC Educational Resources Information Center

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

Bloxham, Jeremy; Gubbins, David

1989-01-01

345

Tracing magnetic fields with ground state alignment  

NASA Astrophysics Data System (ADS)

Observational studies of magnetic fields are vital as magnetic fields play a crucial role in various astrophysical processes, including star formation, accretion of matter, transport processes (e.g. transport of heat), and cosmic rays. The existing ways of magnetic field studies have their limitations. Therefore, it is important to explore new effects that can bring information about magnetic field. We identified a process “ground state alignment” as a new way to determine the magnetic field direction in diffuse medium. The consequence of the process is the polarization of spectral lines resulting from scattering and absorption from aligned atomic/ionic species with fine or hyperfine structure. The alignment is due to anisotropic radiation impinging on the atom/ion, while the magnetic field induces precession and realign the atom/ion and therefore the polarization of the emitted or absorbed radiation reflects the direction of the magnetic field. The atoms get aligned at their low levels and, as the life-time of the atoms/ions we deal with is long, the alignment induced by anisotropic radiation is susceptible to extremely weak magnetic fields (1G?B?10-15G). Compared to the upper level Hanle effect, atomic realignment is most suitable for the studies of magnetic field in the diffuse medium, where magnetic field is relatively weak. The corresponding physics of alignment is based on solid foundations of quantum electrodynamics and in a different physical regime the alignment has become a part of solar spectroscopy. In fact, the effects of atomic/ionic alignment, including the realignment in magnetic field, were studied in the laboratory decades ago, mostly in relation to the maser research. Recently, the atomic effect has been already detected in observations from circumstellar medium and this is a harbinger of future extensive magnetic field studies. It is very encouraging that a variety of atoms with fine or hyperfine splitting of the ground or metastable states exhibit the alignment and the resulting polarization degree in some cases exceeds 20%. A unique feature of the atomic realignment is that they can reveal the 3D orientation of magnetic field. In this paper, we shall review the basic physical processes involved in atomic realignment. We shall also discuss its applications to interplanetary, circumstellar and interstellar magnetic fields. In addition, our research reveals that the polarization of the radiation arising from the transitions between fine and hyperfine states of the ground level can provide a unique diagnostics of magnetic fields, including those in the early universe.

Yan, Huirong; Lazarian, A.

2012-08-01

346

Field-Portable Fiber-Optic Gravimeter.  

National Technical Information Service (NTIS)

Researchers examined the feasibility of a field-portable fiber-optic gravimeter. Such a gravimeter, if successful, would provide a simple alternative to present, complex, delicate reference/observatory devices. The phase I research objective was to demons...

C. M. Davis

1989-01-01

347

Magnetic optics for proton radiography  

SciTech Connect

High energy protons of 10 to 50 GeV can be used to radiograph dense objects. Because the transmitted beam particles undergo multiple coulomb scattering (MCS) in the object, a magnetic lens system is used to focus the particles exiting each point of the object onto a distant image plane. Without the lens, the MCS would seriously blur the radiographic image. Correlations can be introduced in the illuminating beam to cancel a major part of the chromatic and geometric aberrations in the lens, while providing locations inside the lens where the rays are sorted by MCS angle. This allows the introduction of angle cut apertures to aid material identification. The requirement for a matched multistage lens system with successively smaller angle-cut apertures leads to the use of minus-identity ({minus}I) lenses, in which the angle sorting is in the longitudinal mid plane of the lens, and the exit beam correlations are the same as the input correlations. A single stage {minus}I lens has been successfully tested at Brookhaven with 10-GeV protons and another is being used in dynamic experiments with 0.8-GeV protons at Los Alamos. The resolution achievable at higher energies is briefly surveyed.

Mottershead, C.T.; Zumbro, J.D.

1997-10-01

348

Tracking charged particles through magnetic fields using MCNP and MCNPX  

SciTech Connect

The MCNP and MCNPX multiparticle Monte Carlo transport codes have been modified with a patch that allows specialized tracking of charged particles through the magnetic fields of a charged-particle beam optics system using pregenerated maps output from the COSY INFINITY code. A map is the rule for updating the particles' phase-space through a magnetic element. A file containing a single COSY map is assigned to each magnetic cell, which must be a vacuum. For current applications, the COSY maps are generated for protons, but any charged particle will be properly transported.

Favorite, J.A.; Adams, K.J.; Zumbro, J.D.

1999-07-01

349

Magnetic induction-induced resistive heating of optical fibers and gratings.  

PubMed

Magnetic induction heating of optical fibers packaged with a steel plate is studied using a fiber Bragg grating. The dependence on the induced wavelength shift with magnetic field is obtained for a commercially available induction heater. More than a 300°C temperature rise is observed within seconds. The potential of magnetic induction as an efficient and rapid means of modulating devices and as a novel approach to potential optical based magnetic field and current sensing is proposed and discussed. The extension of the ideas into micro and nanophotonics is described. PMID:23503262

Canning, John; Naqshbandi, Masood; Cook, Kevin; Huyang, George

2013-03-15

350

Dynamic Faraday magneto-optical properties of the water-based Fe3O4 magnetic fluids  

Microsoft Academic Search

Dynamic properties of water-based Fe3O4 magnetic fluids are investigated in AC magnetic field. The magnetic fluid films with 6?m thick are implemented in magneto-optical rotation effect by self-designed experimental platform. The transmitted light intensity of magnetic fluids diluted into different mass percentage concentration are presented and compared with magneto-optical glass. A new property of Faraday effect of magnetic fluid is

Du Lin; Wang Shibin; Lin Sen

2010-01-01

351

Magnetic Field Investigations During ROSETTA's Steins Flyby  

NASA Astrophysics Data System (ADS)

During the recent Steins flyby of the ROSETTA spacecraft magnetic field measurements have been made with both, the RPC orbiter magnetometer and the ROMAP lander magnetometer. These combined magnetic field measurements allow a detailed examination of any magnetic signatures caused either directly by the asteroid or indirectly by Steins different modes of interaction with the solar wind. Comparing our measurements with simulation results show that Steins does not possess a significant remanent magnetization. The magnetization is estimated at less than 1 mAm2/kg. This is significantly different from results at Braille and Gaspra.

Glassmeier, K.; Auster, H.; Richter, I.; Motschmann, U.; RPC/ROMAP Teams

2009-05-01

352

Modeling Magnetic Field Topology at Jupiter with the Khurana Magnetic Field Model  

NASA Astrophysics Data System (ADS)

To explore the degree of coupling between the interplanetary magnetic field (IMF) and Jupiter's magnetosphere, we traced magnetic field lines from the polar region of the planet using the Khurana [1997, 2005] magnetic field model. We used a parameterized definition of the Jovian magnetopause created by Joy et al. [2002] that varies with the value of the solar wind dynamic pressure. We searched for field lines that cross the magnetopause and that potentially connect to the interplanetary magnetic field. We further explored the variation on magnetic field structure with local time orientation of Jupiter's dipole (i.e. Central Meridian Longitude) as well as upstream solar wind and IMF conditions.

Cohen, I.; Bagenal, F.

2008-12-01

353

Magnetic and other field effects on prochiral chemical reactions  

NASA Astrophysics Data System (ADS)

Experiments are reported in which three prochiral organic reactions were conducted in the presence of a ca. 1T magnetic field which was oriented with reference to the earth's geometric axes. The sign and magnitude of the rotation varied with the macroscopic orientation of the magnetic field and the time that the reaction was performed. Control measurements were in accord with expectations. The fact that the sign of the observed optical rotation of the product was reversed for all three reported reactions when the magnetic field was reversed for reactions conducted on the same day suggests that either the observed asymmetric synthesis was due to the reactions being conducted in a chiral physical field or extremely unusual stochastic processes were involved.

Piotrowska, Krystyna; Edwards, Deborah; Mitch, Alan; Dougherty, Ralph C.

1980-09-01

354

Constrained superfields and supersymmetric magnetic field systems  

SciTech Connect

After Lancaster the authors examine chiral constraints in N = 2 superspace formulation for supersymmetric magnetic field systems. Such odd constraints are connected with the so-called spin-orbit coupling procedure of supersymmetrization. They propose new even constraints for magnetic supersymmetric systems and relate them to the standard procedure enhanced by Witten. These models describing spin-one half particles moving in a plane with a transverse magnetic field are compared and discussed. The cases of a constant magnetic field and of the harmonic oscillator are connected through different correspondences.

Dehin, D.; Hussin, V. (Universite de Liege, Physique Theorique et Mathematique, Institut de Physique au Sart Tilman, Batiment B.5, B-4000 Liege (BE))

1988-01-01

355

Ionospheric electric fields, currents, and resulting magnetic fields variations  

NASA Astrophysics Data System (ADS)

This thesis uses an equivalent circuit model to calculate ionospheric electric fields, current densities and introduced magnetic fields variations on the ground. The role of the field aligned current is examined. Using different wind models, we studied the electric field variations with altitude, season and solar activity. The ionospheric eastward electric field changes very little within the whole ionosphere. The southward (equatorward) electric field is large and changes quickly with height in the E region although it is nearly constant in the F region. The prereversal enhancement of the eastward electric field is produced by the F region dynamo. We conclude that the Forbes and Gillette tidal wind can reproduce most features of the Jicamarca experiment and the AE-E and DE-2 satellite observations of the electric fields. The HWM90 empirical wind model failed to produce the observed electric field and it seems the semidiurnal wind in HWM90 is too strong. The field aligned current is located mainly in the E and low F region. The non-coincidence of the geomagnetic and geographic equators has a strong effect on the field aligned current in the equatorial zone. The field aligned currents driven by Forbes' winds for March equinox and December solstice flow mainly from the southern to northern hemisphere in the morning and vice versa in the afternoon at F region heights. The observed magnetic field variations on the ground are well reproduced in our simulations. The field aligned current is the main contributor to the eastward magnetic field component in the equatorial zone. The longitudinal inequality of the northward magnetic field is introduced mainly by the variations of the local magnetic field intensity. The electric field variations have only a minor effect. The northward magnetic field variations with the solar activity are introduced by changes of the E region equatorward electric field and the Hall conductivity.

Du, Junhu

356

Magnetic field associated with active electrochemical corrosion  

Microsoft Academic Search

The purpose of this work is to provide a better understanding of the underlying sources of the magnetic field associated with ongoing electrochemical corrosion, to investigate the spatio-temporal information content of the corrosion magnetic field, and to evaluate its potential utility in non-invasive quantification of hidden corrosion. The importance of this work lies in the fact that conventional electrochemical instruments

Afshin Abedi

2000-01-01

357

Coronal Heating and the Photospheric Magnetic Field  

Microsoft Academic Search

Since magnetic field typically plays a role (either active or passive) in coronal heating theories, it may be possible to evaluate these theories by investigating the relationship between the coronal energy budget (the total power requirement of the corona) and measurable properties of the photospheric magnetic field. The X-ray flux is a useful proxy for the total power required to

C. E. Parnell; P. A. Sturrock

1997-01-01

358

Variability and topology of solar magnetic field  

Microsoft Academic Search

Observations of the large scale magnetic field in the photosphere taken at the Wilcox Solar Observatory since 1976 up to 2005 have been analyzed to deduce its latitudinal and longitudinal structures, its differential rotation, and their variability in time. The main results are the following: - The latitudinal structure of the solar magnetic field with a period of polarity change

E. A. Gavryuseva

2006-01-01

359

Astrophysical magnetic fields and nonlinear dynamo theory  

Microsoft Academic Search

The current understanding of astrophysical magnetic fields is reviewed, focusing on their generation and maintenance by turbulence. In the astrophysical context this generation is usually explained by a self-excited dynamo, which involves flows that can amplify a weak ‘seed’ magnetic field exponentially fast. Particular emphasis is placed on the nonlinear saturation of the dynamo. Analytic and numerical results are discussed

Axel Brandenburg; Kandaswamy Subramanian

2005-01-01

360

Coulomb crystals in the magnetic field  

NASA Astrophysics Data System (ADS)

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?1014G ). The effect of the magnetic field on ion displacements in a strongly magnetized neutron star crust can suppress the nuclear reaction rates and make them extremely sensitive to the magnetic-field direction.

Baiko, D. A.

2009-10-01

361

Magnetic field decay in model SSC dipoles  

Microsoft Academic Search

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

W. S. Gilbert; R. F. Althaus; P. J. Barale; R. W. Benjegerdes; M. A. Green; M. I. Green; R. M. Scanlan

1989-01-01

362

Biological effects of high DC magnetic fields  

Microsoft Academic Search

The principal focus of the program is the analysis of magnetic field effects on physiological functions in experimental animals and selected organ and tissue systems. A major research effort has involved the use of electrical recording techniques to detect functional alterations in the cardiovascular, neural, and visual systems during the application of DC magnetic fields. These systems involve ionic conduction

Tenforde

1981-01-01

363

Magnetic fields and the solar corona  

Microsoft Academic Search

Coronal magnetic fields calculated by the methods developed in Paper I (Altschuler and Newkirk, 1969) and the empirical description of the solar corona of November 1966 derived in Paper II (Newkirket al., 1970) are combined in order to investigate what connection exists between the magnetic fields and the density structure of the corona.

Gordon Newkirk; Martin D. Altschuler

1970-01-01

364

Pure phase encode magnetic field gradient monitor  

Microsoft Academic Search

Numerous methods have been developed to measure MRI gradient waveforms and k-space trajectories. The most promising new strategy appears to be magnetic field monitoring with RF microprobes. Multiple RF microprobes may record the magnetic field evolution associated with a wide variety of imaging pulse sequences. The method involves exciting one or more test samples and measuring the time evolution of

Hui Han; Rodney P. MacGregor; Bruce J. Balcom

2009-01-01

365

Efficient Characterization of Magnetic Field Sources  

Microsoft Academic Search

A technique for the estimation of the magnetic field intensity emitted by industrial installations is presented. The method is best-suited for investigation of environmental magnetic field for health purposes. Simulation and measurement case-studies supporting the provided theoretical results are discussed

M. Bertocco; F. Dughiero; C. Greggio; E. Sieni; A. Sona

2006-01-01

366

Magnetic fields, branes, and noncommutative geometry  

Microsoft Academic Search

We construct a simple physical model of a particle moving on the infinite noncommutative 2-plane. The model consists of a pair of opposite charges moving in a strong magnetic field. In addition, the charges are connected by a spring. In the limit of large magnetic field, the charges are frozen into the lowest Landau levels. Interactions of such particles include

Daniela Bigatti; Leonard Susskind

2000-01-01

367

Directional discontinuities in the interplanetary magnetic field  

Microsoft Academic Search

It is shown that the interplanetary magnetic field has different characteristics on different scales, and it is noted that a given physical theory may not be applicable or relevant on all scales. Four scales are defined in terms of time intervals on which the data may be viewed. Many discontinuities in the magnetic-field direction are seen on the mesoscale (˜

Leonard F. Burlaga

1969-01-01

368

Magnetic Fields, Ball Lightning and Campanology  

Microsoft Academic Search

WOODING suggests1 that ball lightning is a plasma vortex ring structure produced by a process similar to the ablation of a solid surface by a high power laser pulse. A plasma vortex ring structure requires a magnetic field; here I present two pieces of evidence to show that a magnetic field is associated with ball lightning, and which may help

A. J. F. Blair

1973-01-01

369

Magnetic field propagation in a stellar dynamo  

Microsoft Academic Search

Numerical simulations of stellar dynamos are reviewed. Dynamic dynamo models solve the nonlinear, three-dimensional, time-dependent, magnetohydrodynamic equations for the convective velocity, the thermodynamic variables, and the generated magnetic field in a rotating, spherical shell of ionized gas. When the dynamo operates in the convection zone, the simulated magnetic fields propagate away from the equator in the opposite direction inferred from

Gary A. Glatzmaier

1985-01-01

370

Ground Vehicle Navigation Using Magnetic Field Variation  

NASA Astrophysics Data System (ADS)

The Earth's magnetic field has been the bedrock of navigation for centuries. The latest research highlights the uniqueness of magnetic field measurements based on position due to large scale variations as well as localized perturbations. These observable changes in the Earth's magnetic field as a function of position provide distinct information which can be used for navigation. This dissertation describes ground vehicle navigation exploiting variation in Earth's magnetic field using a self-contained navigation system consisting of only a magnetometer and magnetic field maps. In order to achieve navigation, effective calibration enables repeatable magnetic field measurements from different vehicles and facilitates mapping of the observable magnetic field as a function of position. A new modified ellipsoid calibration technique for strapdown magnetometers in large vehicles is described, as well as analysis of position measurement generation comparing a multitude of measurement compositions using existing and newly developed likelihood techniques. Finally, navigation solutions are presented using both a position measurement and direct incorporation of the magnetometer measurements via a particle filter to demonstrate road navigation in three different environments. Emphatically, the results affirm that navigation using magnetic field variation in ground vehicles is viable and achieves adequate performance for road level navigation.

Shockley, Jeremiah A.

371

Space Quantization in a Gyrating Magnetic Field  

Microsoft Academic Search

The nonadiabatic transitions which a system with angular momentum J makes in a magnetic field which is rotating about an axis inclined with respect to the field are calculated. It is shown that the effects depend on the sign of the magnetic moment of the system. We therefore have an absolute method for measuring the sign and magnitude of the

I. I. Rabi

1937-01-01

372

Hydrogen atom moving across a magnetic field  

SciTech Connect

A hydrogen atom moving across a magnetic field is considered in a wide region of magnitudes of magnetic field and atom momentum. We solve the Schroedinger equation of the system numerically using an imaginary time method and find wave functions of the lowest states of atom. We calculate the energy and the mean electron-nucleus separation as a function of atom momentum and magnetic field. All the results obtained could be summarized as a phase diagram on the 'atom-momentum - magnetic-field' plane. There are transformations of wave-function structure at critical values of atom momentum and magnetic field that result in a specific behavior of dependencies of energy and mean interparticle separation on the atom momentum P. We discuss a transition from the Zeeman regime to the high magnetic field regime. A qualitative analysis of the complicated behavior of wave functions vs P based on the effective potential examination is given. We analyze a sharp transition at the critical momentum from a Coulomb-type state polarized due to atom motion to a strongly decentered (Landau-type) state at low magnetic fields. A crossover occurring at intermediate magnetic fields is also studied.

Lozovik, Yu.E.; Volkov, S.Yu. [Institute of Spectroscopy, Troitsk, Moscow region, 142190 (Russian Federation)

2004-08-01

373

Magnetic isotope and magnetic field effects on the DNA synthesis.  

PubMed

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

2013-07-13

374

Magnetic isotope and magnetic field effects on the DNA synthesis  

PubMed Central

Magnetic isotope and magnetic field effects on the rate of DNA synthesis catalysed by polymerases ? with isotopic ions 24Mg2+, 25Mg2+ and 26Mg2+ in the catalytic sites were detected. No difference in enzymatic activity was found between polymerases ? carrying 24Mg2+ and 26Mg2+ ions with spinless, non-magnetic nuclei 24Mg and 26Mg. However, 25Mg2+ ions with magnetic nucleus 25Mg were shown to suppress enzymatic activity by two to three times with respect to the enzymatic activity of polymerases ? with 24Mg2+ and 26Mg2+ 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 Zn2+ ions carrying magnetic 67Zn and non-magnetic 64Zn nuclei, respectively. A new, ion–radical mechanism of the DNA synthesis is suggested to explain these effects. Magnetic field dependence of the magnesium-catalysed DNA synthesis is in a perfect agreement with the proposed ion–radical mechanism. It is pointed out that the magnetic isotope and magnetic field effects may be used for medicinal purposes (trans-cranial magnetic treatment of cognitive deceases, cell proliferation, control of the cancer cells, etc).

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

2013-01-01

375

Vehicle detection using a magnetic field sensor  

Microsoft Academic Search

The measurement of vehicle magnetic moments and the results from use of a fluxgate magnetic sensor to actuate a lighting system from the magnetic fields of passing vehicles is reported. A typical U.S. automobile has a magnetic moment of about 200 A-m2(Ampere-meters2), while for a school bus it is about 2000 A-m2. When the vehicle is modeled as an ideal

S. V. Marshall

1978-01-01

376

Intergalactic Magnetic Fields from Quasar Outflows  

Microsoft Academic Search

Outflows from quasars inevitably pollute the intergalactic medium (IGM) with magnetic fields. The short-lived activity of\\u000a a quasar leaves behind an expanding magnetized bubble in the IGM. We model the expansion of the remnant quasar bubbles and\\u000a calculate their distribution as a function magnetic field strength at different redshifts. We find that by a redshift \\u000a z ~ <\\/font\\u000a>3z \\\\sim

Steven Furlanetto; Abraham Loeb

2002-01-01

377

Permanent magnet edge-field quadrupole  

DOEpatents

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. 10 figs.

Tatchyn, R.O.

1997-01-21

378

High Field Magnets With HTS Conductors  

Microsoft Academic Search

Development of high-field magnets using high temperature superconductors (HTS) is a core activity at the NHMFL. Magnet technology based on both YBCO-coated tape conductors and Bi-2212 round wires is being pursued. Two specific projects are underway. The first is a user magnet with a 17 T YBCO coil set which, inside an LTS outsert, will generate a combined field of

H. W. Weijers; U. P. Trociewitz; W. D. Markiewicz; J. Jiang; D. Myers; E. E. Hellstrom; A. Xu; J. Jaroszynski; P. Noyes; Y. Viouchkov; D. C. Larbalestier

2010-01-01

379

Magnetic Instabilities in High Field Superconductors  

Microsoft Academic Search

In the process of magnetizing cylindrical specimens of a typical high field superconductor Nb-50 at.%Ti, flux jumps were induced by magnetic disturbances. The stability limit field Hfj increased steadily with increasing temperature, and no magnetic instability occurred for temperatures in excess of about 6.5 K. The calculation of Hfj was performed taking into account the cylindrical sample geometry and the

Tatsuo Akachi; Takeshi Ogasawara; Ko Yasukochi

1981-01-01

380

Fiber optic network links oil field controls  

SciTech Connect

To improve automation in the Lost Hills waterflood near Bakersfield, Calif., Chevron U.S.A. Production Co. created a network of remote and central programmable logic controller (PLC) with industrial-strength fiber optics. The network allows for centralized control of information on each well's performance and the field's operational problem. Information can now be more accurately and quickly accessed and managed from the central processing plant and the mainframe accounting system. The installed network uses 3M brand Series 6000 modular fiber optics that are industrial-strength with a large-core of 200[mu]. Since the 1920s, Chevron U.S.A. Production Co. has produced more than 86 million bbl of oil and 173 bcf of gas from the Lost Hills field in California's San Joaquin valley. Waterflooding of the field began in spring 1992. The paper describes field operations, earlier automation efforts, the options reviewed, the fiber optic option, and field installation.

Carswell, P.W. (Chevron U.S.A. Production Co., Bakersfield, CA (United States)); Neeley, J.R. (3M Telecom Systems Group, Austin, TX (United States))

1994-03-07

381

Taming the Collapse of Optical Fields  

NASA Astrophysics Data System (ADS)

Field collapse, which occurs in various nonlinear systems, has attracted much attention, owing to its universality, complexity, and applicability. A great challenge and expectation is to achieve the controllable and designable collapsing pattern. Here we predict theoretically and demonstrate experimentally the novel collapsing behaviors of the vector optical fields in a self-focusing Kerr medium. Surprisingly, the results reveal that the collapse of the vector optical field is controllable and designable by engineering the distribution of hybrid states of polarization, and has the robust feature insensitive to the random noise. Our idea has its significance which it opens a new window for manipulating the optical field and the different kinds of field, and then facilitates to push the related researches.

Li, Si-Min; Li, Yongnan; Wang, Xi-Lin; Kong, Ling-Jun; Lou, Kai; Tu, Chenghou; Tian, Yongjun; Wang, Hui-Tian

2012-12-01

382

Orienting Paramecium with intense static magnetic fields  

NASA Astrophysics Data System (ADS)

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 < B < 8 T were applied to immobilized (non-swimming) 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

383

Materials Processing in Magnetic Fields  

NASA Astrophysics Data System (ADS)

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

Schneider-Muntau, Hans J.; Wada, Hitoshi

384

Warm inflation in presence of magnetic fields  

NASA Astrophysics Data System (ADS)

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; Sánchez, Ángel; Ayala, Alejandro; Mizher, Ana Julia

2013-07-01

385

Color imaging the magnetic field distribution in superconductors  

SciTech Connect

A magneto-optically active glass was used to image the magnetic field distribution in superconductors using the Faraday effect. Polarized white light illumination of the glass resulted in various colors depending on the setting of the analyzing polaroid. These colors are shown to be consistent with the known dependence of the Faraday rotation angle on the applied magnetic field, the temperature of the glass, and the wavelength of the light. This technique was used to observe field distributions in polycrystalline and single-crystal YBa{sub 2}Cu{sub 3}O{sub 7} samples. In the ceramic sample, the field was uniform within the resolution (50 {mu}m) of this technique and field magnitudes were measured with a 10% accuracy. In the single crystal, the magnetic field distribution was not uniform showing field gradients imaged as color gradients on the pictures of the glass. Contours of constant magnetic field were drawn from these photographs and from these, a critical current density of 10{sup 9} A/m{sup 2} was deduced in an external field of 136 mT.

Batalla, E.; Zwartz, E.G.; Goudreault, R.; Wright, L.S. (Department of Physics, Royal Military College of Canada, Kingston, Ontario (Canada))

1990-08-01

386

Ohm's law for mean magnetic fields  

SciTech Connect

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

Boozer, A.H.

1984-11-01

387

Whole field reflectance optical tomography  

NASA Astrophysics Data System (ADS)

Optical imaging through highly scattering media such as biological tissues is a topic of intense research, especially for biomedical applications. Diverse optical systems are currently under study and development for displaying the functional imaging of the brain and for the detection of breast tumors. From the theoretical point of view, a suitable description of light propagation in tissues involves the Radiative Transfer Equation, which considers the energetic aspects of light propagation. However, this equation cannot be solved analytically in a closed form and the Diffusion Approximation is normally used. Experimentally it is possible to use Transmission or Reflection geometries and Time Resolved, Frequency Modulated or CW sources. Each configuration has specific advantages and drawbacks, depending on the desired application. In the present contribution, we investigate the reflected light images registered by a CCD camera when scattering and absorbing inhomogeneities are located at different depths inside turbid media. This configuration is of particular interest for the detection and optical characterization of changes in blood flow in organs, as well as for the detection and characterization of inclusions in those cases for which the transmission slab geometry is not well suited. Images are properly normalized to the background intensity and allow analyzing relative large areas (typically 5 × 5 cm2) of the tissue. We tested the proposal using Numerical Monte Carlo simulations implemented in a Graphic Processing Unit (Video accelerating Card). Calculations are thus several orders of magnitude faster than those run in CPU. Experimental results in phantoms are also given.

Carbone, Nicolás A.; García, Héctor A.; di Rocco, Héctor O.; Iriarte, Daniela I.; Pomarico, Juan A.; Ranea Sandoval, Héctor F.

2011-08-01

388

Probing Primordial Magnetic Fields Using Ly? Clouds  

NASA Astrophysics Data System (ADS)

From previous studies of the effect of primordial magnetic fields on early structure formation, we know that the presence of primordial magnetic fields during early structure formation could induce more perturbations at small scales (at present 1-10 h -1 Mpc) as compared to the usual ?CDM theory. Matter power spectra over these scales are effectively probed by cosmological observables such as shear correlation and Ly? clouds. In this paper we discuss the implications of primordial magnetic fields on the distribution of Ly? clouds. We simulate the line-of-sight density fluctuation including the contribution coming from the primordial magnetic fields. We compute the evolution of Ly? opacity for this case and compare our theoretical estimates of Ly? opacity with the existing data to constrain the parameters of the primordial magnetic fields. We also discuss the case when the two density fields are correlated. Our analysis yields an upper bound of roughly 0.3-0.6 nG on the magnetic field strength for a range of nearly scale-invariant models, corresponding to a magnetic field power spectrum index n ~= -3.

Pandey, Kanhaiya L.; Sethi, Shiv K.

2013-01-01

389

Mercury's internal magnetic field: Constraints on fields of crustal origin  

NASA Astrophysics Data System (ADS)

Observations of Mercury's internal magnetic field during MESSENGER's first flyby (M1) and the first and third flybys of Mariner 10 (M10-I, M10-III) suggest that small-scale crustal magnetic fields, if they exist, are at the limit of resolution. Small-scale crustal fields are most easily identified near closest approach (CA) as features with wavelengths comparable to, or larger than, the spacecraft altitude. One small feature (< 4 nT in magnitude) encountered near CA during MESSENGER's first flyby may be either a crustal magnetic field or a plasma pressure effect. By means of Parker's constrained optimization approach, with no assumptions on the direction of magnetization, we can place constraints on the product of magnetization and magnetized layer thickness from such observations. The second flyby (M2) will allow additional constraints to be placed on the presence of small-scale fields, and correlations will be possible among topographic profiles measured by the Mercury Laser Altimeter (MLA), features seen on MESSENGER and Mariner 10 images, and any variations in the internal field. This flyby will acquire the first images of the CA region of M10-III, which has been pivotal in establishing the dipolar character of Mercury's magnetic field. Our ability to isolate small-scale crustal magnetic fields has been hindered by the limited coverage to date, as well as the difficulty in isolating the internal field. Across the terrestrial planets and the Moon, minimum magnetization contrast and iron abundance in the crust show a positive correlation. This correlation suggests that crustal iron content plays a determining role in the strength of crustal magnetization.

Purucker, M. E.; Sabaka, T. J.; Solomon, S. C.; Anderson, B. J.; Korth, H.; Zuber, M. T.; Neumann, G. A.; Head, J. W.; Johnson, C. L.; Uno, H.

2008-12-01

390

An optical E-field sensor  

Microsoft Academic Search

An electric field sensor utilizing a spherical antenna, a bulk electrooptic crystal, and an optical fiber link for measurement of high-amplitude transient electric fields is presented. The sensor transducer, which is based on the polarimetric reflection principle, is located inside the antenna. A laser-generated signal transmitted by a fiber is modulated by the test signal in the crystal inside the

H. Kopola; A. Thansandote; J. Chrostowski; S. S. Stuchly

1990-01-01

391

Optical fiber electric field intensity sensor  

Microsoft Academic Search

In this paper the results of the experimental investigation of fiber optic electric field intensity sensor are presented. These sensors are based on electroluminescent effect which consists in the light emission by some substances placed in variable electric field. The luminescent effect is observed in some composite semiconductors, among other - ZnS, doped by Mn, for high its concentration, order

Tadeusz Pustelny; Barbara M. Pustelny

2001-01-01

392

Measurement of interaction force between small distances sandwiched with magnetic fluid under magnetic field  

NASA Astrophysics Data System (ADS)

In this contribution, the interactive force measurement between 10nm distance under magnetic field is carried out. Previous measurement of the interactive force is reported by Israelachivili et al. However, its measurement under magnetic field has not been performed. The methodology described in this paper is easier as the distance between two surfaces is not measured optically but dynamically. Therefore, it is different from the previous reported studies. Based on the results of the measurement of the interactive force, the diameter of the particle suspended in a solution under magnetic field is also estimated. Moreover, it may be predictable how the clusters have been formed. The method described will be very useful for new productions based on magnetic fluid.

Miyazaki, T.; Shibayama, A.; Sato, T.; Fujita, T.

2002-11-01

393

The Protogalactic Origin for Cosmic Magnetic Fields  

Microsoft Academic Search

It is demonstrated that strong magnetic fields are produced from a zero\\u000ainitial magnetic field during the pregalactic era, when galaxies are first\\u000aforming. Their development proceeds in three phases. In the first phase, weak\\u000amagnetic fields are created by the Biermann battery mechanism, acting in\\u000ashocked parts of the intergalactic medium where caustics form and intersect. In\\u000athe second

Russell M. Kulsrud; Renyue Cen; Jeremiah P. Ostriker; Dongsu Ryu

1996-01-01

394

Turbulence and Magnetic Fields in Astrophysical Plasmas  

Microsoft Academic Search

Magnetic fields permeate the Universe. They are found in planets, stars, accretion discs, galaxies, clusters of galaxies,\\u000a and the intergalactic medium. While there is often a component of the field that is spatially coherent at the scale of the\\u000a astrophysical object, the field lines are tangled chaotically and there are magnetic fluctuations at scales that range over\\u000a orders of magnitude.

Alexander A. Schekochihin; Steven C Cowley

2007-01-01

395

Ohm's law for mean magnetic fields  

SciTech Connect

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

Boozer, A.H.

1986-05-01

396

Emittance measurement in a magnetic field  

SciTech Connect

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.

Boyd, J.K.

1991-04-15

397

Manipulating Cells with Static Magnetic Fields  

NASA Astrophysics Data System (ADS)

We review our investigations of the use of static magnetic fields, B, for manipulating cells and cellular processes. We describe how B fields modify the cell division pattern of frog embryos and consequently can be used to probe the pattern determinants. We also observe that magnetic fields modify the swimming behavior of Paramecium Caudatum. We describe these modifications and their potential application to investigations of their swimming behavior.

Valles, J. M.; Guevorkian, K.

2005-07-01

398

Magnetic field effects on dielectrophoresis in manganites  

NASA Astrophysics Data System (ADS)

Perovskite-type manganese oxides (manganites) are of interest for many of the different properties they possess, including colossal magnetoresistance (CMR) and ferroelectric behavior. With the application of an electric field, large resistance decreases have been noted near the insulator-to-metal transition temperature in samples of (La1-yPry)1-xCaxMnO3 (LPCMO). Two proposed models have emerged to explain the behavior, dielectric breakdown and dielectrophoresis, with experimental evidence showing some aspects of the dielectrophoresis model to be correct. However, neither model accounts for magnetic interactions among the ferromagnetic metallic regions and the effects of a magnetic field applied in conjunction with an electric field. We have performed measurements on LPCMO samples by varying the strength and orientation of the magnetic field and the applied voltage. Cross-shaped microstructures have been made on LPCMO samples to allow us to investigate the effects of sample size on dielectrophoresis. We will present resistance and magnetization data obtained on LPCMO samples at various magnetic field strengths, magnetic field orientations, and sample sizes to elucidate the effect of magnetic interactions on dielectrophoresis induced transport and magnetic properties.

Grant, Daniel; Dragiev, Galin; Biswas, Amlan

2013-03-01

399

Vector Magnetic Field in Emerging Flux Regions  

NASA Astrophysics Data System (ADS)

A crucial phase in magnetic flux emergence is the rise of magnetic flux tubes through the solar photosphere, which represents a severe transition between the very different environments of the solar interior and corona. Multi-wavelength observations with Flare Genesis, TRACE, SoHO, and more recently with the vector magnetographs at THEMIS and Hida (DST) led to the following conclusions. The fragmented magnetic field in the emergence region - with dipped field lines or bald patches - is directly related with Ellerman bombs, arch filament systems, and overlying coronal loops. Measurements of vector magnetic fields have given evidence that undulating "serpentine" fields are present while magnetic flux tubes cross the photosphere. See the sketch below, and for more detail see Pariat et al. (2004, 2007); Watanabe et al. (2008):

Schmieder, B.; Pariat, E.

400

Magnetic field considerations in fusion power plant environs  

Microsoft Academic Search

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

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

1976-01-01

401

Controlling molecular scattering in optical lattices and fields  

NASA Astrophysics Data System (ADS)

Experimental physicists accomplished striking progress in preparing ultracold polar molecules in a precise quantum state [1]. Soon enough, one can envision ``ideal'' experiments of molecular physics where all quantum states of molecules can be addressed and detected. In addition, ultracold polar molecules benefit from a vast tool set of controls. Molecular chemical reactions can be enhanced by electric fields [2] or can be suppressed by optical lattices [3]. If the molecules have a magnetic dipole moment, they can also be controlled by magnetic fields. Starting from these ideas, we want to investigate what would be a scattering event between two molecules in an optical lattice, and in the presence of an electric and magnetic field. We will choose, as a probe example, the OH molecule which has either an electric and magnetic dipole moment. We will compare the effect of these additional external controls on the differential cross section and ask if we can trace back some information on the inter-molecular potential. [4pt] [1] Ni et al.,Science 322,231(2008).[0pt] [2] Qu'em'ener et al., Phys. Rev. A 81, 022702 (2010); Ni et al., Nature 464, 1324 (2010).[0pt] [3] Qu'em'ener et al., Phys. Rev. A 81, 060701(R)(2010); Phys. Rev. A 83, 012705 (2011); de Miranda et al., Nature Physics 7, 502 (2011).

Quéméener, Goulven; Bohn, John

2012-06-01

402

Magnetic Field Extrapolations And Current Sheets  

NASA Astrophysics Data System (ADS)

Solar flares and coronal mass ejections (CMEs) --- phenomena which impact our society, but are scientifically interesting in themselves --- are driven by free magnetic energy in the coronal magnetic field. Since the coronal magnetic field cannot be directly measured, modelers often extrapolate the coronal field from the photospheric magnetograms --- the only field measurements routinely available. The best extrapolation techniques assume that the field is force free (coronal currents parallel the magnetic field), but that currents are not simply a linear function of the magnetic field. Recent tests, however, suggest that such non-linear force-free field (NLFFF) extrapolation techniques often underestimate free magnetic energy. We hypothesize that, since relaxation-based NLFFF techniques tend to smooth field discontinuities, such approaches will fail when current sheets are present. Here, we test this hypothesis by applying the Optimization NLFFF method to two configurations from an MHD simulation --- one with strong current concentrations, and one with weak concentrations. This work is supported by a NASA Sun-Earth Connections Theory grant to UC-Berkeley.

Welsch, Brian; De Moortel, I.; McTiernan, J. M.

2007-05-01

403

Neutron Star Crust in Strong Magnetic Fields  

NASA Astrophysics Data System (ADS)

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

404

Global magnetic fields: variation of solar minima  

NASA Astrophysics Data System (ADS)

The topology of the large-scale magnetic field of the Sun and its role in the development of magnetic activity were investigated using H ? charts of the Sun in the period 1887-2011. We have considered the indices characterizing the minimum activity epoch, according to the data of large-scale magnetic fields. Such indices include: dipole-octopole index, area and average latitude of the field with dominant polarity in each hemisphere and others. We studied the correlation between these indices and the amplitude of the following sunspot cycle, and the relation between the duration of the cycle of large-scale magnetic fields and the duration of the sunspot cycle. The comparative analysis of the solar corona during the minimum epochs in activity cycles 12 to 24 shows that the large-scale magnetic field has been slow and steadily changing during the past 130 years. The reasons for the variations in the solar coronal structure and its relation with long-term variations in the geomagnetic indices, solar wind and Gleissberg cycle are discussed. We also discuss the origin of the large-scale magnetic field. Perhaps the large-scale field leads to the generation of small-scale bipolar ephemeral regions, which in turn support the large-scale field. The existence of two dynamos: a dynamo of sunspots and a surface dynamo can explain phenomena such as long periods of sunspot minima, permanent dynamo in stars and the geomagnetic field.

Tlatov, Andrey G.; Obridko, Vladimir N.

2012-07-01

405

Characterization and manipulation of a high-magnetic field trap  

NASA Astrophysics Data System (ADS)

We report on the characterization of an efficient atom trap within a background magnetic field of 2.6 Tesla. Up to 10?8 Rubidium atoms are recaptured from a cold atomic beam with a 2-3% collection efficiency, in a cigar-shaped volume and cooled with a six-beam optical molasses. The aspect ratio of the trap is measured as a function of the magnetic field curvature, which can be varied to produce a range of trap shapes. The trapping lineshape is both narrow and asymmetric, as is characteristic of laser-cooling of atoms or ions in an external trapping potential. Additional features of the high magnetic field trap include cooling onto hollow shell-like structures. Simulation results are also presented.

Paradis, Eric; Raithel, Georg

2012-06-01

406

Optical Fiber Sensors from Laboratory to Field Trials  

NASA Astrophysics Data System (ADS)

Fiber optic metrology developed at the CEA LIST laboratories involves fiber Bragg grating sensors, distributed Brillouin optical time domain reflectometry and optically stimulated luminescence dosimetry. Recent activities in optical fiber sensing are reviewed from laboratory experiments to field trials.

Ferdinand, P.; Magne, S.; Laffont, G.; Dewynter, V.; Maurin, L.; Prudhomme, C.; Roussel, N.; Giuseffi, M.; Maguis, S.

407

New Magnetic phases of holmium in a magnetic field  

SciTech Connect

We have examined the behavior of two well-characterized single crystals ofholmium in a magnetic field applied along the /ital c/ axis in a temperaturerange from 90 to 140 K, using magnetization and dilatometric measurements. Wehave found several new phases in this previously unexplored region of the phasediagram.

Steinitz, M. O.; Kahrizi, M.; Tindall, D. A.; Ali, N.

1989-07-01

408

Relationship between the magnetic hyperfine field and the magnetic moment  

Microsoft Academic Search

Based on experimental data it is shown, for some chosen alloys and compounds of iron, that there is no unique relationship between the 57Fe-site magnetic hyperfine field, Bhf, and the magnetic moment per Fe atom, ?. Instead, the Bhf–? plot consists of several branches, each of them being characteristic of a given alloy or compound. Consequently, the effective proportionality constant

S. M. Dubiel

2009-01-01

409

How are static magnetic fields detected biologically?  

NASA Astrophysics Data System (ADS)

There is overwhelming evidence that life, from bacteria to birds to bats, detects magnetic fields, using the fields for orientation or navigation. Indeed there are recent reports (based on Google Earth imagery) that cattle and deer align themselves with the earth's magnetic field. [1]. The development of frog and insect eggs are changed by high magnetic fields, probably through known physical mechanisms. However, the mechanisms for eukaryotic navigation and alignment are not clear. Persuasive published models will be discussed. Evidence, that static magnetic fields might produce therapeutic effects, will be updated [2]. [4pt] [1] S. Begall, et al., Proc Natl Acad Sci USA, 105:13451 (2008). [0pt] [2] L. Finegold and B.L. Flamm, BMJ, 332:4 (2006).

Finegold, Leonard

2009-03-01

410

Magnetic and magneto-optical properties of CdS:Mn quantum dots in PVA matrix  

NASA Astrophysics Data System (ADS)

We have studied the magnetic and magneto-optical properties of CdS:Mn quantum dots in polyvinyl alcohol matrix synthesized by co-precipitation method. The size of quantum dots was estimated by means of absorption spectroscopy. The results of measurements of magnetic susceptibility as a function of temperature and spectral dependence of the Faraday rotation of CdS:Mn quantum dots / polyvinyl alcohol composites are presented. In this work magnetic susceptibility was investigated by Faraday's method at the temperatures of (78-300) K in magnetic fields of (0.05-0.8) T. The inverse magnetic susceptibility as a function of temperature follows a Curie Weiss law. Formation of ferromagnetic coupling between magnetic ions is supposed. Magneto-optical Faraday rotation has been investigated in the wavelength region (400-700) nm at temperature 300 K in a magnetic field up to 5 T. Sign of the Verdet constant is found to be negative.

Fediv, V. I.; Savchuk, A. I.; Frasunyak, V. M.; Makoviy, V. V.; Savchuk, O. A.

2010-09-01

411

2-D Optical Imaging of Permanent Magnet ECR Source  

NASA Astrophysics Data System (ADS)

Optical images of a permanent magnet ECR source were collected with a CCD camera (W. Getty and J. Geddes, J. Vac. Sci. Technol. B 12, pp. 408-415 (Jan/Feb 1994)) The plasma images were focused directly on the CCD. The images indicate field patterns for various pressures, flowrates, and power. A 1-kW, 2.45 GHz microwave source is connected through a circulator and a three-stub tuner to a horn which expands the microwave aperture to a 15 cm x 20 cm rectangle. The horn is attached to the top plate of the vacuum chamber which holds a 15 cm x 20 cm aluminum 6 slot grill containing 5 rows of permanent magnets. The ECR surface of 875 G is approximately 1 cm from the grill. The plasma expands to fill the 28-cm diameter chamber. Depending upon the magnetic configuration and the input conditions, the mode of the plasma changes. This is noted in the two dimensional optical images observed by the CCD. These results will be compared to Langmuir probe data, microwave interferometry, and optical emission spectroscopy. Etch results of oxide patterned silicon wafers will also be discussed. The results of these diagnostics indicate the uniformity of this new plasma source in different modes of operation.

Wilson, Aaron R.; Shannon, Steve S.; Brake, Mary L.; Getty, Ward D.

1996-10-01

412

XUV harmonic enhancement by magnetic fields  

SciTech Connect

We examine three ways to enhance harmonic output of an XUV planar free-electron laser (FEL) operating in the Compton regime. The first method is to increase the rms static magnetic field, making it as large as possible. The second is by adding effective magnetic fields at the harmonics, thereby increasing the coupling to the harmonics. The third is by phase programming; i.e. programming the magnetic field to introduce jumps in the phase of the electrons as they move through phase space.

Elliott, C.J.; Schmitt, M.J.

1986-09-01

413

Magnetic field dependent tunneling in glasses  

PubMed

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

414

Magnetic field structures in chemically peculiar stars  

NASA Astrophysics Data System (ADS)

We report the results of magnetic field modelling of around 50 CP stars, performed using the "magnetic charges" technique. The modelling shows that the sample reveals four main types of magnetic configurations: 1) a central dipole, 2) a dipole, shifted along the axis, 3) a dipole, shifted across the axis, and 4) complex structures. The vast majority of stars has the field structure of a dipole, shifted from the center of the star. This shift can have any direction, both along and across the axis. A small percentage of stars possess field structures, formed by two or more dipoles.

Glagolevskij, Yu. V.

2011-04-01

415

Magnetic field quality analysis using ANSYS  

SciTech Connect

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

416

Magnetic Field Dependent Tunneling in Glasses  

NASA Astrophysics Data System (ADS)

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.

Strehlow, P.; Wohlfahrt, M.; Jansen, A. G. M.; Haueisen, R.; Weiss, G.; Enss, C.; Hunklinger, S.

2000-02-01

417

[Weak magnetic fields and cognitive activity].  

PubMed

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

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

418

Environmental magnetic fields: Influences on early embryogenesis  

SciTech Connect

A 10-mG, 50 to 60-Hz magnetic field is in the intensity and frequency range that people worldwide are often exposed to in homes and in the workplace. Studies about the effects of 50- to 100-Hz electromagnetic fields on various species of animal embryos (fish, chick, fly, sea urchin, rat, and mouse) indicate that early stages of embryonic development are responsive to fluctuating magnetic fields. Chick, sea urchin, and mouse embryos are responsive to magnetic field intensities of 10-100 mG. Results from studies on sea urchin embryos indicate that exposure to conditions of rotating 60-Hz magnetic fields, e.g., similar to those in our environment, interferes with cell proliferation at the morula stage in a manner dependent on field intensity. The cleavage stages, prior to the 64-cell stage, were not delayed by this rotating 60-Hz magnetic field suggesting that the ionic surges, DNA replication, and translational events essential for early cleavage stages were not significantly altered. Studies of histone synthesis in early sea urchin embryos indicated that the rotating 60-Hz magnetic field decreased zygotic expression of early histone genes at the morula stage and suggests that this decrease in early histone production was limiting to cell proliferation. Whether these comparative observations from animal development studies will be paralleled by results from studies of human embryogenesis, as suggested by some epidemiology studies, has yet to be established. 38 refs.

Cameron, I.L.; Hardman, W.E.; Winters, W.D.; Zimmerman, S.; Zimmerman, A.M. (Univ. of Texas Health Science Center, San Antonio (United States))

1993-04-01

419

Plasma Dynamics in Pulsed Strong Magnetic Fields  

NASA Astrophysics Data System (ADS)

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

Maron, Yitzhak

2003-10-01

420

First Magnetic Field Models for Recently Discovered Magnetic ? Cephei and Slowly Pulsating B Stars  

NASA Astrophysics Data System (ADS)

Despite of the importance of magnetic fields for the full understanding of the properties of pulsating ? Cephei and slowly pulsating B (SPB) stars, these fields have scarcely been studied over the rotation cycle until now. During the past two years we have obtained multi-epoch polarimetric spectra of several ? Cephei and SPB stars with FORS 2 at the Very Large Telescope and SOFIN at the Nordic Optical Telescope to search for a rotation period and to constrain the geometry of the magnetic field. The rotation periods and magnetic field geometries were determined for three ? Cephei stars, ?1 CMa, 15 CMa, and V1449 Aql, the candidate ? Cephei star ? Pyx, and the SPB star 33 Eri.

Hubrig, S.; Schöller, M.; Ilyin, I.; Briquet, M.; Morel, T.; De Cat, P.

2012-09-01

421

Magnetic impulses and associated optical signatures in the dayside aurora  

SciTech Connect

The authors present five magnetic impulse events observed at South Pole and in the magnetically conjugate area at Iqaluit. The magnetic signatures recorded during these events appear to be similar to those discussed by several authors as possible ionospheric signatures of sporadic dayside reconnection via the flux transfer process. Coordinated ground-based image-intensified all sky camera data were acquired at South Pole during the events. The optical data show that prior to the onset of each of the events the dayside cusp aurora is several degrees poleward of the station, signifying event initiation on closed field lines. Overhead aurora appears at the onset of the magnetic event and precipitation seems to expand over a large region equatorward of the quiescent cusp aurora. As the event decays the aurora dies away and the quiescent dayside cusp aurora, in four out of five cases, returns poleward of the station. This morphology is inconsistent with the model in which the ground based signature of an FTE is caused by a field aligned current configuration moving over a ground station in the antisunward direction. The observations show temporal events which begin at or inside the boundary of closed field lines.

Mende, S.B.; Rairden, R.L. (Lockheed Palo Alto Research Laboratories, CA (USA)); Lanzerotti, L.J.; Maclennan, C.G. (AT T Bell Laboratories, Murray Hill, NJ (USA))

1990-02-01

422

Recent biophysical studies in high magnetic fields  

NASA Astrophysics Data System (ADS)

A brief overview of biophysical effects of steady magnetic fields is given. The need of high field strength is illustrated by several recent diamagnetic orientation experiments. They include rod-like viruses, purple membranes and chromosomes. Results of various studies on bees, quails, rats and pigeons exposed to fields above 7 T are also resumed.

Maret, Georg

1990-06-01

423

Directed Plasma Flow across Magnetic Field  

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

424

TRANSITION REGION MAGNETIC FIELD AND POLAR MAGNETIC DISTURBANCES  

Microsoft Academic Search

The Explorer 12 measurements of the magnetic field outside the magnetosphere are compared with ground magnetograms from arctic observatories. Results indicate that an exterior field with a southerly component tends to be associated with ground disturbance, whereas a northward field is associated with quiet conditions. Examples are presented show- ing how a north-to-south field-direction change accompanies an increase in ground

D. H. Fairfield; L. J. Jr. Cahill

1966-01-01

425

Magnetic field evolution of accreting neutron stars  

NASA Astrophysics Data System (ADS)

We discuss the effect of accretion on the evolution of the magnetic field of a neutron star and highlight the main unresolved issues. Charged, accreted matter is funneled towards the magnetic poles where it heats the stellar surface and alters its magnetic structure resulting in an overall reduction of the magnetic dipole moment. Mechanisms for accretion-induced field reduction include accelerated Ohmic decay, vortex-fluxoid interactions, and magnetic burial or screening. We discuss how these can be integrated into a global model and detail recent self-consistent, three-dimensional, magneto-hydrodynamic, calculations (using analytic Grad-Shafranov methods and the numerical solver ZEUS-MP) which incorporate global resistive instabilities. These models can explain why neutron stars in binaries have systematically lower magnetic dipole moments than isolated neutron stars. Finally we discuss applications including the evolution of accreting millisecond pulsars and type-I X-ray bursts, magnetars, and gravitational waves.

Payne, D. J. B.; Vigelius, M.; Melatos, A.

2008-10-01

426

Reconnection Rates of Magnetic Fields.  

National Technical Information Service (NTIS)

The Sweet-Parker and Petschek scalings of magnetic reconnection rate are modified to include the effect of the viscosity. The modified scalings show that the viscous effect can be important in high- beta plasmas. The theoretical reconnection scalings are ...

W. Park D. A. Monticello R. B. White

1983-01-01

427

Two-Cascade Magnetic Field Stabilizer of the Installation for Measuring Neutron Electric Dipole Moment.  

National Technical Information Service (NTIS)

A two-cascade magnetic field stabilizer of installation for the measurement of neutron electrical dipole moment (EDM) using ultracold neutrons has been constructed and tested. Quantum cesium magnetometers (QCM) with optical pumping placed inside a ferroma...

A. N. Kozlov Y. V. Nikitenko Y. V. Taran

1980-01-01

428

Field Directed Ordering in Magnetic Nanocrystal Structures  

NASA Astrophysics Data System (ADS)

Iron oxide nanocrystals (NCs) have been the focus of intense research owing to the observation of tunable magnetic properties which could lead to advances in many fields including magnetic storage devices and medicine. We have been targeting the use of iron oxide NCs as magnetoresistance (MR) based sensors using ordered NC arrays. In this work, we will present our efforts toward using external magnetic fields to induce intraparticle ordering in iron oxide NC drop cast films. We use x-ray diffraction to analyze effects of the external fields on the NC array structure, while using SQUID magnetometry to probe the effects of NC interactions on the magnetic properties of iron oxide NCs ranging from 5 - 20 nm in diameter. MR measurements suggest large changes in the MR ratio can be achieved using the directed ordering approach for NC arrays. Our work could provide new avenues towards the fabrication of new magnetic devices.

Lawson, Stuart; Meulenberg, Robert

2013-03-01

429

Magnetic Instabilities in High Field Superconductors  

NASA Astrophysics Data System (ADS)

In the process of magnetizing cylindrical specimens of a typical high field superconductor Nb-50 at.%Ti, flux jumps were induced by magnetic disturbances. The stability limit field Hfj increased steadily with increasing temperature, and no magnetic instability occurred for temperatures in excess of about 6.5 K. The calculation of Hfj was performed taking into account the cylindrical sample geometry and the critical state equation JcB1-?{=}?. According to the relative magnitudes of the magnetic diffusivity Dm and the thermal diffusivity Dt, the expression of Hfj was derived for two cases; (1) Dm>Dt, and (2) Dm?Dt. Good agreement between experiment and theory was obtained on the stability limit field Hfj and the temperature above which magnetic instabilities do not take place.

Akachi, Tatsuo; Ogasawara, Takeshi; Yasuk?chi, K?

1981-08-01

430

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

SciTech Connect

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

431

Magnetic fields around BOK globules: CCD polarimetry of CB 4  

NASA Astrophysics Data System (ADS)

The small Bok globule CB 4 was probed using a CCD imaging polarimeter in order to create a detailed map of the magnetic field associated with this cloud. Stars as faint as 17th mag at V band were measured polarimetrically with uncertainties less than 1%. Sky transmission variations were minimized via a system of synchronous polaroid rotation and bidirectional charge shifting. In all, 80 stars behind the periphery of the globule were accurately analyzed polarimetrically. The large-scale (1-2 pc) magnetic field direction around CB 4 was found to be very uniform (P.A. = 63.3 deg +/- 1.1 deg). Double-Gaussian fitting of the polarization position angle histogram gave a dispersion of 10 deg about the primary field direction. Possible field-line compression was found inward of approximately 0.2 pc from the cloud center. No appreciable twisting of field lines was found. By plotting stellar separations against differences of polarization angles, CB 4 was found to have a magnetic field decorrelation length of approximately 0.1 pc, similar to the size of the visually opaque cire, but much smaller than the size of the bright optical rim or CO half-power contour of approximately 0.5 pc. The magnetic field decorrelation length may be related to a characteristic transient clumping size, or perhaps even to clumps of a more permanent nature.

Kane, Brian D.; Clemens, Dan P.; Leach, Robert W.; Barvainis, Richard

1995-05-01

432

Optical spins and nano-antenna array for magnetic therapy.  

PubMed

Magnetic therapy is an alternative medicine practice involving the use of magnetic fields subjected to certain parts of the body and stimulates healing from a range of health problems. In this paper, an embedded nano-antenna system using the optical spins generated from a particular configuration of microrings (PANDA) is proposed. The orthogonal solitons pairs corresponding to the left-hand and right-hand optical solitons (photons) produced from dark-bright soliton conversion can be simultaneously detected within the system at the output ports. Two possible spin states which are assigned as angular momentum of either +? or -? will be absorbed by an object whenever this set of orthogonal solitons is imparted to the object. Magnetic moments could indeed arise from the intrinsic property of spins. By controlling some important parameters of the system such as soliton input power, coupling coefficients and sizes of rings, output signals from microring resonator system can be tuned and optimized to be used as magnetic therapy array. PMID:23686955

Thammawongsa, N; Mitatha, S; Yupapin, P P

2013-05-15

433

Magnetic power inverter: AC voltage generation from DC magnetic fields  

NASA Astrophysics Data System (ADS)

We propose a method that allows power conversion from DC magnetic fields to AC electric voltages using domain wall (DW) motion in ferromagnetic nanowires. The device concept relies on spinmotive force, voltage generation due to magnetization dynamics. Sinusoidal modulation of the nanowire width introduces a periodic potential for a DW, the gradient of which exerts variable pressure on the traveling DW. This results in time variation of the DW precession frequency and the associated voltage. Using a one-dimensional model, we show that the frequency and amplitude of the AC outputs can be tuned by the DC magnetic fields and wire-design.

Ieda, Jun'ichi; Maekawa, Sadamichi

2012-12-01

434

Ultrafast all-optical magnetization reversal in GdFeCo films around plasmonic nanostructures  

NASA Astrophysics Data System (ADS)

It has recently been experimentally demonstrated that reproducible and controllable all-optical magnetization reversal in GdFeCo films can be achieved with a single ultrafast (from 40fs to 3ps) femtosecond laser pulse. While the microscopic origin of the effect is still unclear, we suggest that the effect is caused by a combination of light-induced quasi-static magnetic field, with dynamic thermal effects due to laser heating, as well as magnetic fields generated by thermoelectric effect-caused electrical currents. This finding reveals great potential for ultrafast data storage through magnetic switching without the aid of an external magnetic field. It was further recently predicted that utilization of plasmonic nanostructures may provide the way to achieve fast all-optical magnetization switching with smaller/cheaper laser sources with longer pulse durations. We will present the simulations of temporal dynamics of magnetization reversal around plasmonic nanostructures with the combination of Landau Lifshitz Bloch and finite element modeling. Our modeling results predict that plasmonic nanostructures can significantly alter all-optical magnetization switching process and may help achieve a number of technologically important effects that cannot be achieved otherwise. Results of experimental studies of optical magnetization reversal in GdFeCo films around plasmonic nanostructures are also provided.

Kochergin, Vladimir; Cherepov, Sergiy; Schwartz, Robert N.; Flanagan, Kevin; Krivorotov, Ilya N.; Kochergin, Evgeniy V.; Wang, Kang L.

2013-09-01

435

A subwavelength plasmonic metamolecule exhibiting magnetic-based optical Fano resonance  

NASA Astrophysics Data System (ADS)

The lack of symmetry between electric and magnetic charges, a fundamental consequence of the small value of the fine-structure constant, is directly related to the weakness of magnetic effects in optical materials. Properly tailored plasmonic nanoclusters have been proposed recently to induce artificial optical magnetism based on the principle that magnetic effects are indistinguishable from specific forms of spatial dispersion of permittivity at optical frequencies. In a different context, plasmonic Fano resonances have generated a great deal of interest, particularly for use in sensing applications that benefit from sharp spectral features and extreme field localization. In the absence of natural magnetism, optical Fano resonances have so far been based on purely electric effects. In this Letter, we demonstrate that a subwavelength plasmonic metamolecule consisting of four closely spaced gold nanoparticles supports a strong magnetic response coupled to a broad electric resonance. Small structural asymmetries in the assembled nanoring enable the interaction between electric and magnetic modes, leading to the first observation of a magnetic-based Fano scattering resonance at optical frequencies. Our findings are supported by excellent agreement with simulations and analytical calculations, and represent an important step towards the quest for artificial magnetism and negative refractive index metamaterials at optical frequencies.

Shafiei, Farbod; Monticone, Francesco; Le, Khai Q.; Liu, Xing-Xiang; Hartsfield, Thomas; Alù, Andrea; Li, Xiaoqin

2013-02-01

436

Magnetic and Magneto-Optic Behavior of Bismuth and Thulium Substituted Yttrium Iron Garnets  

Microsoft Academic Search

The magnetic and magneto-optic properties of a series of thulium and bismuth substituted YIG thin films have been studied. The magnetic properties studied are the effective g-value and the first order cubic anisotropy field. The magneto-optic property investigated is the Faraday rotation constant. Thulium substitution in the garnet system shows an anamolously low effective g-value and typical temperature dependence of

Terry Blake Mitchell

1986-01-01

437

Modulating the Magnetic Field to Improve Magnetic Sensors  

NASA Astrophysics Data System (ADS)

The sensitivity of most magnetic sensors is affected by 1/f noise. Modulating the magnetic field to be detected by magnetic sensors can improve their performance by minimizing the effect of this 1/f noise and, in some cases, also have them operate in a narrow frequency band where they have higher sensitivity. We present approaches for modulating the field. One approach is the MEMS flux concentrator can be used with small magnetic sensors and another, based on using a rotating disc containing flux concentrators that can be used with large magnetic sensors, such as magnetoelectric sensors, that have an increased sensitivity at their mechanical resonance frequency. Sidebands observed around the modulation frequency demonstrate the applicability of these approaches. The MEMS flux concentrator has improved the signal to noise ratio in the power spectrum by a factor of 15. The sensors have the potential to achieve sensitivities of a few pT/Hz^1/2 at 1 Hz.

Edelstein, Alan; Petrie, Jonathan; Fine, Jonathan; Fischer, Greg; Burnette, James; Srinivasan, Gopal; Mandal, Sanjay

2011-03-01

438

Wire codes, magnetic fields, and childhood cancer  

SciTech Connect

Childhood cancer has been modestly associated with wire codes, an exposure surrogate for power frequency magnetic fields, but less consistently with measured fields. The authors analyzed data on the population distribution of wire codes and their relationship with several measured magnetic field metrics. In a given geographic area, there is a marked trend for decreased prevalence from low to high wire code categories, but there are differences between areas. For average measured fields, there is a positive relationship between the mean of the distributions and wire codes but a large overlap among the categories. Better discrimination is obtained for the extremes of the measurement values when comparing the highest and the lowest wire code categories. Instability of measurements, intermittent fields, or other exposure conditions do not appear to provide a viable explanation for the differences between wire codes and magnetic fields with respect to the strength and consistency of their respective association with childhood cancer.

Kheifets, L.I.; Kavet, R.; Sussman, S.S. [Electric Power Research Inst., Palo Alto, CA (United States)

1997-05-01

439

Magnetic Dipole Field 3D Model  

NSDL National Science Digital Library

The Magnetic Dipole Field 3D Model displays the field lines and field vectors of a dipole located at the origin and oriented along the z-axis. Users can compute the field line passing through a point by dragging the a marker within the 3D view. Users can also visualize the field vectors in a plane passing though the center of the dipole. The Magnetic Dipole Field 3D Model was developed using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_em_MagneticDipole3D.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.

Christian, Wolfgang

2012-08-11