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Sample records for magnetic field rings

  1. THE SNS RING DIPOLE MAGNETIC FIELD QUALITY.

    SciTech Connect

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

    2002-06-03

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

  2. Magnetic Field Control of Current through Molecular Ring Junctions

    NASA Astrophysics Data System (ADS)

    Rai, Dhurba; Galperin, Michael; Hod, Oded; Nitzan, Abraham

    2013-03-01

    We study circular currents driven by voltage bias in molecular wires with ring structures [J. Phys. Chem. C 114, 20583 (2010)]. We revisit magnetic field effects on molecular ring structures presenting conditions under which magnetic field control of molecular ring conduction is realizable. [Phys. Rev. B 85, 155440 (2012)]. We find these conditions to be (a) weak molecule-lead coupling, implying relatively distinct conduction resonances, (b) asymmetric junction structure (e.g., meta or ortho connected benzene ring rather than a para connection), and (c) minimal dephasing (implying low temperature) so as to maintain coherence between multiple pathways of conduction. When these conditions are satisfied, considerable sensitivity to the applied magnetic field normal to the molecular ring plane is found. Although sensitivity to magnetic field is suppressed by dephasing, quantitative estimates indicate that magnetic field control can be observed in suitably constructed molecular ring junctions. We demonstrate control of the spin-flip inelastic electron tunnelling spectroscopy (IETS) signal and discuss spin polarization of total and circular currents in a benzene ring junction with spin impurity [Phys. Rev. B 86, 045420 (2012)]. We gratefully acknowledge support by the National Science Foundation (CHE-1057930), the US-Israel Binational Science Foundation (Grant No. 2008282), and the Hellman Family Foundation.

  3. Measurements of magnetic fields by a ring laser.

    PubMed

    Zhang, J; Feng, T; Zhang, S; Jin, G

    1992-10-20

    The principle of measuring magnetic fields with a ring laser system is discussed. The main source of error, the Zeeman effect, is studied, and a corresponding technique to reduce it is described. An experimental setup is developed with a Faraday cell of a large product of the Verdet constant and the length. The experimental device obtains a sensitivity of 0.5 nT and a stability of 2 nT. PMID:20733862

  4. Externally controlled local magnetic field in a conducting mesoscopic ring coupled to a quantum wire

    SciTech Connect

    Maiti, Santanu K.

    2015-01-14

    In the present work, the possibility of regulating local magnetic field in a quantum ring is investigated theoretically. The ring is coupled to a quantum wire and subjected to an in-plane electric field. Under a finite bias voltage across the wire a net circulating current is established in the ring which produces a strong magnetic field at its centre. This magnetic field can be tuned externally in a wide range by regulating the in-plane electric field, and thus, our present system can be utilized to control magnetic field at a specific region. The feasibility of this quantum system in designing spin-based quantum devices is also analyzed.

  5. Externally controlled local magnetic field in a conducting mesoscopic ring coupled to a quantum wire

    NASA Astrophysics Data System (ADS)

    Maiti, Santanu K.

    2015-01-01

    In the present work, the possibility of regulating local magnetic field in a quantum ring is investigated theoretically. The ring is coupled to a quantum wire and subjected to an in-plane electric field. Under a finite bias voltage across the wire a net circulating current is established in the ring which produces a strong magnetic field at its centre. This magnetic field can be tuned externally in a wide range by regulating the in-plane electric field, and thus, our present system can be utilized to control magnetic field at a specific region. The feasibility of this quantum system in designing spin-based quantum devices is also analyzed.

  6. Magnetic Field Observations of the Ring Current in the Inner Magnetosphere and the Ionosphere

    NASA Astrophysics Data System (ADS)

    Le, G.

    2013-05-01

    We present the result of an extensive survey of the magnetic field observations in the inner magnetosphere and the ionosphere using magnetic field data from multiple spacecraft (Polar, Cluster, ISEE, AMPTE/CCE, and C/NOFS). The purpose of this study is to understand the magnetic field evolution during geomagnetic storms, and its implication to the ring current and loss mechanisms of ring current particles. The magnetic field generated by the ring current inflates the inner magnetosphere and causes magnetic field depressions in the equatorial magnetosphere and ionosphere. We perform statistical survey of the magnetic field depressions in the ionosphere and the entire inner magnetosphere to extract information about the ring current asymmetry and evolution. We find that the equatorial magnetic field depression exhibits strong local time dependence in both the high and low altitude observations. A strong partial ring current is formed during the storm main phase, and data from the low Earth orbit satellite enables us to track the rapid development of the partial ring current. Throughout the recovery phase, the partial ring current remains to be a permanent feature although the degree of asymmetry is reduced. In the early recovery phase, the partial ring current peaks near the dusk terminator as indicated by the peak of the magnetic field depression in the inner magnetosphere. As the recovery phase progresses, the partial ring current decays most quickly near the dusk and results in a dusk-to-midnight moving of the peak of the partial ring current. Thus the loss mechanisms work most effectively near the dusk.

  7. Planetary rings as relics of plasma proto-rings rotating in the magnetic field of a central body

    NASA Astrophysics Data System (ADS)

    Rabinovich, B.

    2007-08-01

    A possibility is discussed in accordance to hypothesis by H. Alfven, that the rings of large planets are relics of some plasma proto-rings rotating in the magnetic fields of central bodies. A finite-dimensional mathematical model of the system is synthesized using the solution of the boundary-value problem by the Boubnov - Galerkin method. The dipole magnetic field of the central body is assumed to have a small eccentricity, and the dipole axis - to be inclined at a small angle to the central body's axis of rotation which coincides with the ring's rotation axis. The proto-ring is supposed to be thin and narrow and having the same rotating axis as the central body. A medium forming the ring is cold rarefied plasma with high electron density, so that electric conductivity of the medium tends to infinity, as well as the magnetic Reynolds number. The original mathematical model is reduced to a system of finite-difference equations whose asymptotic analytical solution is obtained. Emphasis is placed on the problems of stability of the ring's steady state rotation and quantization of the eigenvalues of nondimensional sector velocity of the ring with respect to the central body. The solutions corresponding to magneto-gravitational and to magneto-gyroscopic waves are considered It is demonstrated that some rings characterized by integral quantum numbers are stable and long-living, while the rings which are associated with half-integer quantum numbers (rings>) are unstable and short-living. As a result, an evolutionally rife rotating plasma ring turns out to be stratified into a large number of narrow elite rings separated by gaps whose position correspond to anti-rings. The regions of possible existence of elite rings in near-central body space are determined. The main result of eigenvalue spectrum's analysis is as follows. Quantum numbers determining elite eigenvalues of the sector velocity of a ring (normalized in a certain manner) coincide with the quantum numbers appearing in the solution of the Schr¨odingerequation for a hydrogen atom. Perturbations of the elite orbits corresponding to this numbers satisfy the de Brogli quantum-mechanical condition. The solution of the model boundary-value problem has been applied to planetary rings origin and evolution. The main result is a mechanism of stratification of the evolutionally mature plasma proto-ring into a large number of narrow elite rings separated by anti-rings (gaps), which were playing a role of for present-day planetary rings. Another result is the theoretical substantiation of the presence in the nearplanetary space of a region of existence and stability of plasma rings. The data, which had been obtained in the course of the Voyager, Galileo, and Cassini missions were used for verification of theoretical results concerning the planetary rings and Io plasma thorus. The theoretical dates turned out to be in accordance with experimental dates. References Alfven H. Cosmic Plasma. Dordrecht: Reidel, 1961. Rabinovich B.I. Dynamics of Plasma Ring Rotating in the Magnetic Field of Central Body: Magneto-GravitationalWaves // Cosmic Research, 2006. V. 44. No. 1. P. 43-51. Rabinovich B.I. Dynamics of Plasma Ring Rotating in the Magnetic Field of Central Body: Magneto-Gyroscopic Waves. Problems of Stability and Quantization // Cosmic Research, 2006. V. 44. No. 2. P. 146 - 161. Gore, Rick. Voyager 1 at Saturn. Riddles of the Rings // National Geographic, 1981. V. 160. No. 1. P. 3 - 31. Porco, Carolyn. Captain 's Log.: 2004, 184 // The Planetary Report, 2004. V. 24, No. 5. P. 2 - 18.

  8. Transient Response of Single-Domain Y-Ba-Cu-O Rings to Pulsed Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Askew, T. R.; Weber, J. M.; Cha, Y. S.; Claus, H.; Veal, B. W.

    2002-08-01

    Shielding current limits and magnetic diffusion characteristics have been measured at 77 K for a set of YBCO single-domain rings. These were fabricated from melt-textured cylindrical YBCO monoliths that were densified to nearly 100%, and then oriented from a single seed. The rings were surrounded by a drive coil that can, under pulse conditions, achieve applied magnetic fields in excess of 1 T and induce currents in excess of 50 kA. Simultaneous magnetic characterization with a Rogowski coil and Hall probe was used to determine the induced current in the sample and the magnetic field in the center of the sample. Magnetic fields trapped in the samples were mapped with a scanning Hall probe. When compared with similar measurements on multidomain c-axisoriented YBCO rings, the flux penetration is faster and more uniform around the circumference of the ring. The observed critical current density, 15,000 A/cm2 at 77 K, is suitable for application in penetration-type fault current limiters. Separate measurements of the trapped magnetic field and critical current density in the rings are compared with results obtained by analysis of magnetic diffusion characteristics.

  9. Highly-sensitive magnetic field sensor based on fiber ring laser.

    PubMed

    Deng, Ming; Liu, Danhui; Huang, Wei; Zhu, Tao

    2016-01-11

    A highly sensitive magnetic field sensor based on a fiber ring laser has been proposed and experimentally demonstrated. The magnetic field sensor was fabricated by introducing a rotary apparatus modulated by an external magnetic field into the fiber cavity to twist one section of the fiber. Due to the remarkable birefringence change induced into the laser cavity, the beat frequency generated between two polarizations of the laser is sensitive to the variation of applied magnetic field intensity. Experimental results show that the polarization mode beat frequency linearly shifts with the increment of the magnetic field intensity and the sensitivity reaches up to 7.09 KHz/Oe in the range of 0 - 437 Oe. Therefore, it will be a promising candidate for the weak magnetic field applications including military, hazard forecast and biomedical fields. PMID:26832294

  10. Suppression of chaotic oscillations in a solid-state ring laser by a magnetic field

    SciTech Connect

    Kravtsov, Nikolai V; Firsov, V V; Pashinin, Pavel P; Sidorov, S S; Chekina, S N

    2003-04-30

    The possibility of suppressing chaotic oscillations in a bidirectional Nd{sup 3+} : YAG ring laser with the help of a constant magnetic field is considered. It is shown that the application of a constant magnetic field of a few tens of oersted on the active medium transfers the laser from the synchronous chaos regime to pulsed quasi-periodic generation. (control of laser radiation parameters)

  11. Measurements of the normal state persistent current in Au rings at high and low magnetic fields

    NASA Astrophysics Data System (ADS)

    Petkovic, Ivana; Ngo, Dustin; Lollo, Anthony; Harris, Jack

    2014-03-01

    Flux biased normal metal rings smaller than the phase coherence length can sustain persistent current (PC). We employ cantilever torque magnetometry to detect PC with high sensitivity, efficient background rejection, and in an electromagnetically clean environment. Previously, our group focused on the high magnetic field regime, where the PC is well described by single-particle theory. However at low magnetic field (few flux quanta) interaction effects are expected to be dominant. Previous low field studies by other groups employing SQUID and resonator-based techniques have found that Au, Ag, Cu, and GaAs rings show a large diamagnetic average PC, indicative of attractive e-e interactions. One possible explanation is that the superconductivity that would normally arise from this interaction is suppressed by a small number of magnetic impurities (~ 1 ppm), while the interaction-enhanced persistent current is not. In this talk we will describe measurements of Au rings. We have fabricated arrays of 100,000 rings with 125 nm radius on ultrasensitive silicon cantilevers. At high magnetic fields, we find that the PC agrees with single-particle theory. We also describe the results at low field, expected to give further insight into the many body ground state of this system. We gratefully acknowledge support from NSF Grant #1205861.

  12. Magnetic field distribution of injection chicane dipoles in Spallation Neutron Source accumulator ring

    SciTech Connect

    Wang, Jian-Guang

    2006-01-01

    We have performed 3D computing simulations to study the magnetic field distribution of the injection chicane dipoles in the SNS accumulator ring. The simulations yield the performance characteristics of the magnets and generate the magnetic field data in three dimensional grids for further beam tracking study. Based on the simulation data, a 3D multipole expansion of the chicane dipole field, consisting of the generalized gradients and their derivatives, has been made. The harmonic and pseudo-harmonic components in the expansion give much insight into the magnet physics and can fit directly into theoretical frame work of beam optics. The expansion is quasi-analytical by fitting numeric data into interpolation functions. A 5th-order representation of the magnetic field is generated, and the effects of even higher order terms on the field representation are discussed.

  13. The field line topology of a uniform magnetic field superposed on the field of a distributed ring current

    SciTech Connect

    Chance, M.S. . Plasma Physics Lab.); Greene, J.M.; Jensen, T.H. )

    1991-07-01

    A magnetic field line topology with nulls, generated by superimposing a uniform magnetic field onto the field from a distributed ring current, is analyzed. This simple model is amenable to substantial analytical progress and also facilitates the visualization of the three dimensional field geometry. Four nulls are seen to exist and representative field lines and tubes of flux found by numerical integration are presented. An infinite number of topologically distinct flux bundles is found. A convenient mapping is defined which proves very useful in distinguishing between and following the paths of the different tubes of flux as they traverse through the null system. The complexities already present in this simple but nontrivial configuration serve to emphasize the difficulties in analyzing more complicated geometries, but the intuition gained from this study proves beneficial in those cases. One such example is the application to a model of plasmoid formations in the earth's magnetotail. 7 refs., 19 figs.

  14. Magnetospheric environments of outer planet rings - influence of Saturn's axially symmetric magnetic field

    SciTech Connect

    Hood, L.L.

    1987-07-01

    Saturn's main rings exist within a zone of negligible magnetospheric losses and surface alteration effects, substantially due to the solid-body absorption of inwardly diffusing magnetospheric particles. This process is presently shown to be especially efficient in the inner magnetosphere of Saturn, due to the near-axial symmetry of the planetary magnetic field relative to the equatorial rotation plane; under the assumption of comparable diffusion rates, the inward magnetospheric particle transport is far more inhibited in the inner Saturnian magnetosphere than in the same regions of Jupiter and Uranus, even when only rings of comparable widths and depths are considered. In light of this, ring particle surface exposure to the ion fluxes of the radiation belt remains a prepossessing rationale for low Uranian ring albedos. 86 references.

  15. Antiferromagnetic resonance excitation by terahertz magnetic field resonantly enhanced with split ring resonator

    SciTech Connect

    Mukai, Y.; Hirori, H.; Yamamoto, T.; Kageyama, H.; Tanaka, K.

    2014-07-14

    Excitation of antiferromagnetic resonance (AFMR) in a HoFeO{sub 3} crystal combined with a split ring resonator (SRR) is studied using terahertz (THz) electromagnetic pulses. The magnetic field in the vicinity of the SRR is induced by the incident THz electric field component and excites spin oscillations that correspond to the AFMR, which are directly probed by the Faraday rotation of the polarization of a near-infrared probe pulse. The good agreement of the temperature-dependent magnetization dynamics with the calculation using the two-lattice Landau-Lifshitz-Gilbert equation confirms that the AFMR is excited by the THz magnetic field, which is enhanced at the SRR resonance frequency by a factor of 20 compared to the incident magnetic field.

  16. Ring Current Decay During Northward Turnings of The Interplanetary Magnetic Field

    NASA Astrophysics Data System (ADS)

    Monreal MacMahon, R.; Llop, C.; Miranda, R.

    The ring current formation and energization is thought to be the main consequence of geomagnetic storms and its strength is characterized by the Dst index which evolu- tion satisfies a simple and well-known differential equation introduced by Burton et al. (1975). Since then, several attempts and approaches have been done to study the evolution of the ring current whether introducing discrete values or continuous func- tions for the decay time involved. In this work, we study the character of the recovery phase of magnetic storms in response to well defined northward turnings of the inter- planetary magnetic field using our functional form of the decay time of ring current particles introduced previously.

  17. Magnetic field sensor using the fiber loop ring-down technique and an etched fiber coated with magnetic fluid.

    PubMed

    Shen, Tao; Feng, Yue; Sun, Binchao; Wei, Xinlao

    2016-02-01

    The fiber loop ring-down spectroscopy technique is introduced into the evanescent-field-based sensing scheme in order to create a new type of fiber-based magnetic field sensor. As a consequence, the sensitivity and stability of the magnetic field sensing system are significantly enhanced. The sensor head is constructed using a section of a single-mode fiber with its cladding partially etched. The process of fiber etching is described in detail, and the relationship between the diameter of the etched fiber and the etching time is experimentally investigated. After adopting the appropriate size of the etched fiber, the final experimental results show that the magnetic field strength has a well-defined linear relationship with the inverse of the ring-down time τ over a range of 30 mT with a sensitivity of 95.5 ns/mT. PMID:26836067

  18. Magnetic field control of the intraband optical absorption in two-dimensional quantum rings

    SciTech Connect

    Olendski, O.; Barakat, T.

    2014-02-28

    Linear and nonlinear optical absorption coefficients of the two-dimensional semiconductor ring in the perpendicular magnetic field B are calculated within independent electron approximation. Characteristic feature of the energy spectrum are crossings of the levels with adjacent nonpositive magnetic quantum numbers as the intensity B changes. It is shown that the absorption coefficient of the associated optical transition is drastically decreased at the fields corresponding to the crossing. Proposed model of the Volcano disc allows to get simple mathematical analytical results, which provide clear physical interpretation. An interplay between positive linear and intensity-dependent negative cubic absorption coefficients is discussed; in particular, critical light intensity at which additional resonances appear in the total absorption dependence on the light frequency is calculated as a function of the magnetic field and levels' broadening.

  19. Inner Magnetosphere Modeling at the CCMC: Ring Current, Radiation Belt and Magnetic Field Mapping

    NASA Astrophysics Data System (ADS)

    Rastaetter, L.; Mendoza, A. M.; Chulaki, A.; Kuznetsova, M. M.; Zheng, Y.

    2013-12-01

    Modeling of the inner magnetosphere has entered center stage with the launch of the Van Allen Probes (RBSP) in 2012. The Community Coordinated Modeling Center (CCMC) has drastically improved its offerings of inner magnetosphere models that cover energetic particles in the Earth's ring current and radiation belts. Models added to the CCMC include the stand-alone Comprehensive Inner Magnetosphere-Ionosphere (CIMI) model by M.C. Fok, the Rice Convection Model (RCM) by R. Wolf and S. Sazykin and numerous versions of the Tsyganenko magnetic field model (T89, T96, T01quiet, TS05). These models join the LANL* model by Y. Yu hat was offered for instant run earlier in the year. In addition to these stand-alone models, the Comprehensive Ring Current Model (CRCM) by M.C. Fok and N. Buzulukova joined as a component of the Space Weather Modeling Framework (SWMF) in the magnetosphere model run-on-request category. We present modeling results of the ring current and radiation belt models and demonstrate tracking of satellites such as RBSP. Calculations using the magnetic field models include mappings to the magnetic equator or to minimum-B positions and the determination of foot points in the ionosphere.

  20. Manipulating Majorana zero modes on atomic rings with an external magnetic field

    NASA Astrophysics Data System (ADS)

    Li, Jian; Neupert, Titus; Bernevig, B. Andrei; Yazdani, Ali

    2016-01-01

    Non-Abelian quasiparticles have been predicted to exist in a variety of condensed matter systems. Their defining property is that an adiabatic braid between two of them results in a non-trivial change of the quantum state of the system. The simplest non-Abelian quasiparticles--the Majorana bound states--can occur in one-dimensional electronic nano-structures proximity-coupled to a bulk superconductor. Here we propose a set-up, based on chains of magnetic adatoms on the surface of a thin-film superconductor, in which the control over an externally applied magnetic field suffices to create and manipulate Majorana bound states. We consider specifically rings of adatoms and show that they allow for the creation, annihilation, adiabatic motion and braiding of pairs of Majorana bound states by varying the magnitude and orientation of the external magnetic field.

  1. Manipulating Majorana zero modes on atomic rings with an external magnetic field.

    PubMed

    Li, Jian; Neupert, Titus; Bernevig, B Andrei; Yazdani, Ali

    2016-01-01

    Non-Abelian quasiparticles have been predicted to exist in a variety of condensed matter systems. Their defining property is that an adiabatic braid between two of them results in a non-trivial change of the quantum state of the system. The simplest non-Abelian quasiparticles--the Majorana bound states--can occur in one-dimensional electronic nano-structures proximity-coupled to a bulk superconductor. Here we propose a set-up, based on chains of magnetic adatoms on the surface of a thin-film superconductor, in which the control over an externally applied magnetic field suffices to create and manipulate Majorana bound states. We consider specifically rings of adatoms and show that they allow for the creation, annihilation, adiabatic motion and braiding of pairs of Majorana bound states by varying the magnitude and orientation of the external magnetic field. PMID:26791080

  2. Manipulating Majorana zero modes on atomic rings with an external magnetic field

    PubMed Central

    Li, Jian; Neupert, Titus; Bernevig, B. Andrei; Yazdani, Ali

    2016-01-01

    Non-Abelian quasiparticles have been predicted to exist in a variety of condensed matter systems. Their defining property is that an adiabatic braid between two of them results in a non-trivial change of the quantum state of the system. The simplest non-Abelian quasiparticles—the Majorana bound states—can occur in one-dimensional electronic nano-structures proximity-coupled to a bulk superconductor. Here we propose a set-up, based on chains of magnetic adatoms on the surface of a thin-film superconductor, in which the control over an externally applied magnetic field suffices to create and manipulate Majorana bound states. We consider specifically rings of adatoms and show that they allow for the creation, annihilation, adiabatic motion and braiding of pairs of Majorana bound states by varying the magnitude and orientation of the external magnetic field. PMID:26791080

  3. Design of fiber magnetic field sensor based on fiber Bragg grating Fabry-Perot cavity ring-down spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Qi; Chen, Haiyan

    2015-06-01

    A novel fiber magnetic sensor based on the fiber Bragg grating Fabry-Perot (FBG-FP) cavity ring-down technique with pulse laser injection is proposed and demonstrated theoretically. A general expression of the intensity of the output electric field is derived, and the effect of the external magnetic field on the ring-down time is discussed. The results show that the output light intensity and the ring-down time of the FBG-FP cavity are in the inverse proportion to the magnitude of the external magnetic field. Our results demonstrate the new concept of the fiber magnetic sensor with the FBG-FP cavity ring-down spectroscopy and the technical feasibility.

  4. Magnetic field sensing based on fiber loop ring-down spectroscopy and etched fiber interacting with magnetic fluid

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Liu, Xu; Zhao, Yong; Lv, Riqing; Hu, Haifeng; Li, Jin

    2015-12-01

    A novel magnetic field sensing system based on fiber loop ring-down spectroscopy (FLRDS) and etched fiber interacting with magnetic fluid (MF) is proposed and demonstrated for the first time. The enhanced evanescent field effect in the sensing part was achieved by etching the fiber with hydrofluoric acid. The influence of diameters of etched fiber to the performance of the sensor was investigated and discussed. In the sensing system, the etched fiber surrounded by MF was used as the sensing head and on account of the tunable refractive index and absorption coefficient of MF, the transmission spectrum would change with the magnetic field strength. In this letter, the FLRDS sensing system was theoretically modeled and FLRDS technique was utilized to modulate the transmission spectrum. The sensitivity of magnetic field sensing was enhanced significantly. In the experiment, performances of the magnetic field sensing system were tested by applying different measured magnetic field. The final results indicated that a sensitivity of 12.56 G/μs was achieved.

  5. Design of a three-axis magnetic field measurement system for the magnetic shield of the ring laser gyroscope

    NASA Astrophysics Data System (ADS)

    Rong, Chuiyu; Yao, Xu

    2015-10-01

    The magnetic field is one of the main causes of zero drift in a Ring Laser Gyroscope (RLG), which should be avoided by adopting a magnetic shielding system. The Gauss Meter is usually used to measure the magnetic shielding effectiveness. Generally, the traditional Gauss Meter has advantages of high measure range and high reliability, however, its drawbacks such as complex structure, high price and the PC client software cannot be customized at will, are also obvious. In this paper, aiming at a type of experimental magnetic shielding box of RLG, we design a new portable three-axis magnetic field measurement system. This system has both high modularity degree and reliability, with measuring range at ±48Gs, max resolution at 1.5mGs and can measure the magnetic field in x, y and z direction simultaneously. Besides, its PC client software can be easily customized to achieve the automatic DAQ, analysis, plotting and storage functions. The experiment shows that, this system can meet the measuring requirements of certain type of experimental magnetic shielding box for RLG, meanwhile, for the measurement of some other magnetic shielding effectiveness, this system is also applicable.

  6. Effects of electronic correlations and magnetic field on a molecular ring out of equilibrium

    NASA Astrophysics Data System (ADS)

    Nuss, Martin; von der Linden, Wolfgang; Arrigoni, Enrico

    2014-04-01

    We study the effects of electron-electron interactions on the steady-state characteristics of a hexagonal molecular ring in a magnetic field as a model for a benzene molecular junction. The system is driven out of equilibrium by applying a bias voltage across two metallic leads. We employ a model Hamiltonian approach to evaluate the effects of on-site as well as nearest-neighbor density-density-type interactions in a physically relevant parameter regime. Results for the steady-state current, charge density, and magnetization in three different junction setups (para, meta, and ortho) are presented. Our findings indicate that interactions beyond the mean-field level renormalize voltage thresholds as well as current plateaus. Electron-electron interactions lead to substantial charge redistribution as compared to the mean-field results. We identify a strong response of the circular current on the electronic structure of the metallic leads. Our results are obtained by steady-state cluster perturbation theory, a systematically improvable approximation to study interacting molecular junctions out of equilibrium, even in magnetic fields. Within this framework, general expressions for the current, charge density, and magnetization in the steady state are derived. The method is flexible and fast and can straightforwardly be applied to effective models as obtained from ab initio calculations.

  7. Effect of a permanent magnetic field on quasi-periodic and chaotic oscillation regimes in solid-state ring lasers

    SciTech Connect

    Aleshin, D A; Kravtsov, Nikolai V; Lariontsev, E G; Chekina, S N

    2005-01-31

    Features of nonlinear dynamics of solid-state ring lasers in quasi-periodic and chaotic oscillation regimes in a magnetic field are studied experimentally. Windows of periodic and quasi-periodic regimes within the region of dynamic chaos in a monolithic ring laser with periodically modulated pumping are observed experimentally for the first time. It is shown that an applied magnetic field changes the boundaries of the existence of various nonstationary regimes. It is established that, under certain conditions, lasing regimes can be switched in magnetic fields with strengths of {approx}1 Oe. (active media. lasers)

  8. Influence of a constant magnetic field on non-stationary operation regimes of solid-state ring lasers

    SciTech Connect

    Kravtsov, Nikolai V; Chekina, S N

    2007-02-28

    The effect of a constant magnetic field on the nonlinear radiation dynamics of a monolithic chip ring Nd:YAG laser pumped by modulated radiation is studied experimentally. It is found that the application of a constant magnetic field to the active element of the solid-state ring laser operating in the non-stationary regime results in the displacement of the regions of existence of quasi-periodic and chaotic lasing regimes to the low-frequency region of pump power modulation. In addition, the application of a magnetic field to the active element of the laser gives rise to the spectral nonreciprocity. (control of laser radiation parameters)

  9. Non-thermal Plasmas Around Massive Black Holes: Collective Modes, Ring Configurations and Magnetic Field Generation

    NASA Astrophysics Data System (ADS)

    Coppi, B.

    2013-10-01

    The discovered gamma-ray bubbles emanating from the center of Our Galaxy are a new motivation to develop theories for large scale structures in the Universe in terms of plasmas for which electromagnetic interactions are no less important than the relevant (e.g. density wave theory of spirals) gravitational interactions. Moreover, considering the observed emission spectra, the particle distributions in phase space cannot be represented by isotropic Maxwellian in significant cases. The consequent theory of plasmas surrounding rotating massive black holes has led to identify new stationary plasma and field configurations (in particular Solitary Rings) and modes, emerging from conventional (currentless) disks, that depend on the existence of temperature anisotropies. These modes, which produce outward transport of angular momentum at a significant rate, involve large amplifications of a seed magnetic field. In the related (by the envisioned non-linear mode evolution) stationary configurations, without a seed magnetic field, the field energy densities are of the order of the particle thermal energy densities. Thus a clear sequence of processes for the generation of magnetic fields in the Universe is identified. US DOE partly sponsored.

  10. Improved ring potential of QED at finite temperature and in the presence of weak and strong magnetic fields

    SciTech Connect

    Sadooghi, N.; Anaraki, K. Sohrabi

    2008-12-15

    Using the general structure of the vacuum polarization tensor {pi}{sub {mu}}{sub {nu}}(k{sub 0},k) in the infrared (IR) limit, k{sub 0}{yields}0, the ring contribution to the QED effective potential at finite temperature and the nonzero magnetic field is determined beyond the static limit, (k{sub 0}{yields}0, k{yields}0). The resulting ring potential is then studied in weak and strong magnetic field limits. In the weak magnetic field limit, at high temperature and for {alpha}{yields}0, the improved ring potential consists of a term proportional to T{sup 4}{alpha}{sup 5/2}, in addition to the expected T{sup 4}{alpha}{sup 3/2} term arising from the static limit. Here, {alpha} is the fine structure constant. In the limit of the strong magnetic field, where QED dynamics is dominated by the lowest Landau level, the ring potential includes a novel term consisting of dilogarithmic function (eB)Li{sub 2}(-(2{alpha}/{pi})(eB/m{sup 2})). Using the ring improved (one-loop) effective potential including the one-loop effective potential and ring potential in the IR limit, the dynamical chiral symmetry breaking of QED is studied at finite temperature and in the presence of the strong magnetic field. The gap equation, the dynamical mass and the critical temperature of QED in the regime of the lowest Landau level dominance are determined in the improved IR as well as in the static limit. For a given value of the magnetic field, the improved ring potential is shown to be more efficient in decreasing the critical temperature arising from the one-loop effective potential.

  11. Chiral phase transition in relativistic heavy-ion collisions with weak magnetic fields: Ring diagrams in the linear sigma model

    SciTech Connect

    Ayala, Alejandro; Bashir, Adnan; Raya, Alfredo; Sanchez, Angel

    2009-08-01

    Working in the linear sigma model with quarks, we compute the finite-temperature effective potential in the presence of a weak magnetic field, including the contribution of the pion ring diagrams and considering the sigma as a classical field. In the approximation where the pion self-energy is computed perturbatively, we show that there is a region of the parameter space where the effect of the ring diagrams is to preclude the phase transition from happening. Inclusion of the magnetic field has small effects that however become more important as the system evolves to the lowest temperatures allowed in the analysis.

  12. Ion Rings for Magnetic Fusion

    SciTech Connect

    Greenly, John, B.

    2005-07-31

    This Final Technical Report presents the results of the program, Ion Rings for Magnetic Fusion, which was carried out under Department of Energy funding during the period August, 1993 to January, 2005. The central objective of the program was to study the properties of field-reversed configurations formed by ion rings. In order to reach this objective, our experimental program, called the Field-reversed Ion Ring Experiment, FIREX, undertook to develop an efficient, economical technology for the production of field-reversed ion rings. A field-reversed configuration (FRC) in which the azimuthal (field-reversing) current is carried by ions with gyro-radius comparable to the magnetic separatrix radius is called a field-reversed ion ring. A background plasma is required for charge neutralization of the ring, and this plasma will be confined within the ring's closed magnetic flux. Ion rings have long been of interest as the basis of compact magnetic fusion reactors, as the basis for a high-power accelerator for an inertial fusion driver, and for other applications of high power ion beams or plasmas of high energy density. Specifically, the FIREX program was intended to address the longstanding question of the contribution of large-orbit ions to the observed stability of experimental FRCs to the MHD tilt mode. Typical experimental FRCs with s {approx} 2-4, where s is the ratio of separatrix radius to ion gyro-radius, have been stable to tilting, but desired values for a fusion reactor, s > 20, should be unstable. The FIREX ring would consist of a plasma with large s for the background ions, but with s {approx} 1 for the ring ions. By varying the proportions of these two populations, the minimum proportion of large-orbit ions necessary for stability could be determined. The incorporation of large-orbit ions, perhaps by neutral-beam injection, into an FRC has been advanced for the purpose of stabilizing, heating, controlling angular momentum, and aiding the formation of a reactor-scale FRC, and the FIREX program was intended to test the ideas behind this approach. We will describe in this report the technological development path and advances in physics understanding that allowed FIREX to reach a regime in which ion rings were reproducibly created with up to about half the current necessary to produce field reversal. Unfortunately, the experiments were limited to this level by a fundamental, unanticipated aspect of the physics of strong ion rings in plasma. The FIREX ring is a strongly anisotropic, current-carrying population of ions moving faster than the Alfven speed in the background plasma. The rapidly changing ring current excites very large-amplitude Alfven waves in the plasma, and these waves strongly affect the ring, causing rapid energy loss in a way that is not compatible with the success of the ring trapping scenario around which FIREX was designed. The result was that FIREX rings were always very short-lived. We will discuss the implication of these results for possible future use of large-orbit ions in FRCs. In short, it appears that a certain range of the parameters characterizing the ring Alfven mach number and distribution function must be avoided to allow the existence of a long-lived energetic ion component in an FRC. This report will explain why FIREX experimental results cannot be directly scaled to quantitatively predict this range for a particular FRC configuration. This will require accurate, three-dimensional simulations. FIREX results do constitute a very good dataset for validating such a code, and simulations already carried out during this program provide a guide to the important physics involved.

  13. Magnetic field measurement using a fiber laser sensor in ring arrangement

    NASA Astrophysics Data System (ADS)

    Nascimento, I. M.; Baptista, J. M.; Jorge, P. A. S.; Cruz, J. L.; Andrés, M. V.

    2015-05-01

    In this work an optical fiber laser with loop configuration was developed for magnetic field measurement. The transducer element is an FBG written in a HiBi fiber whose wavelength is modified using a magnetostrictive material that applies deformation in the presence of the magnetic field. The laser has a bandwidth of 450 MHz and operates in single polarization. A shift of 258.5 pm was observed in the laser operating wavelength for a magnetic field of 17.85 mT. Moreover, a maximum sensitivity of 14.72 pm/mT in the linear regime operation was achieved when increasing the magnetic field. The system provides a narrow emission line that is dependent on the magnetic field magnitude enabling high resolution interferometric measurement schemes. The laser response to AC magnetic fields was also characterized using a passive interferometer with higher sensitivity in the range of 8.32 to 17.93 mTRMS.

  14. Fulde-Ferrell-Larkin-Ovchinnikov states in a superconducting ring with magnetic fields: Phase diagram and the first-order phase transitions

    NASA Astrophysics Data System (ADS)

    Yoshii, Ryosuke; Takada, Satoshi; Tsuchiya, Shunji; Marmorini, Giacomo; Hayakawa, Hisao; Nitta, Muneto

    2015-12-01

    We find the angular Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) states (or the twisted kink crystals) in which a phase and an amplitude of a pair potential modulate simultaneously in a quasi-one-dimensional superconducting ring with a static Zeeman magnetic field applied on the ring and static Aharonov-Bohm magnetic flux penetrating the ring. The superconducting ring with magnetic flux produces a persistent current, whereas the Zeeman split of Fermi energy results in the spatial modulation of the pair potential. We show that these two magnetic fields stabilize the FFLO phase in a large parameter region of the magnetic fields. We further draw the phase diagram with the two kinds of first-order phase transitions; one corresponds to phase slips separating the Aharonov-Bohm magnetic flux, and the other separates the number of peaks of the pair amplitude for the Zeeman magnetic field.

  15. Effect of magnet alignment jittering in the damping ring and RTL on wake fields in the linac

    SciTech Connect

    Chao, A.; Rivkin, L.

    1984-01-01

    In order to reduce the beam emittance blow-up due to wake fields in the linac to a tolerable level, it is necessary that the beam injection into the linac does not jitter too much. The tolerance is set to be +- 13 ..mu..m in displacement or +- 0.3 ..mu..rad in angle at the injection point where E = 1.2 GeV. This tolerance assumes ..beta.. = 42 m at the injection point and represents about 2% of the local rms beam size. One potential source of injection jitter comes from the damping ring ejection kicker. Another - which is the subject of this study - is due to the jittering in the alignments of the damping ring and RTL magnets (due to earth motion, nearby pumps, etc.). We assume this alignment jittering is random from magnet to magnet. (If we do not plan to have a fast feedback at the linac injection point; these misalignments do not have to jitter from pulse to pulse; they could be slowly oscillating in time and be equally harmful.) We estimate the tolerance on the magnet alignment jittering to be 0.1 ..mu..m.

  16. Impurity coupled to an artificial magnetic field in a Fermi gas in a ring trap

    NASA Astrophysics Data System (ADS)

    nal, F. Nur; Hetnyi, B.; Oktel, M. .-.

    2015-05-01

    The dynamics of a single impurity interacting with a many-particle background is one of the central problems of condensed-matter physics. Recent progress in ultracold-atom experiments makes it possible to control this dynamics by coupling an artificial gauge field specifically to the impurity. In this paper, we consider a narrow toroidal trap in which a Fermi gas is interacting with a single atom. We show that an external magnetic field coupled to the impurity is a versatile tool to probe the impurity dynamics. Using a Bethe ansatz, we calculate the eigenstates and corresponding energies exactly as a function of the flux through the trap. Adiabatic change of flux connects the ground state to excited states due to flux quantization. For repulsive interactions, the impurity disturbs the Fermi sea by dragging the fermions whose momentum matches the flux. This drag transfers momentum from the impurity to the background and increases the effective mass. The effective mass saturates to the total mass of the system for infinitely repulsive interactions. For attractive interactions, the drag again increases the effective mass which quickly saturates to twice the mass of a single particle as a dimer of the impurity and one fermion is formed. For excited states with momentum comparable to number of particles, effective mass shows a resonant behavior. We argue that standard tools in cold-atom experiments can be used to test these predictions.

  17. Gravitomagnetic field of rotating rings

    NASA Astrophysics Data System (ADS)

    Ruggiero, Matteo Luca

    2016-04-01

    In the framework of the so-called gravitoelectromagnetic formalism, according to which the equations of the gravitational field can be written in analogy with classical electromagnetism, we study the gravitomagnetic field of a rotating ring, orbiting around a central body. We calculate the gravitomagnetic component of the field, both in the intermediate zone between the ring and the central body, and far away from the ring and central body. We evaluate the impact of the gravitomagnetic field on the motion of test particles and, as an application, we study the possibility of using these results, together with the Solar System ephemeris, to infer information on the spin of ring-like structures.

  18. Micromagnetic calculation of magnetization reversal in magnetic rings

    NASA Astrophysics Data System (ADS)

    Lopez-Diaz, Luis

    2002-03-01

    The success of using patterned magnetic nanoelements in Magnetic Random Access Memories (MRAM) depends entirely on our ability to control accurately their switching fields. In a recent study1, we showed that micron-sized narrow rings present well defined stable states and nucleation-free switching between them. In the first part of the talk we review our experimental studies on ring magnets. Pre-patterned Si(100) substrates were used to grow free-standing epitaxial ring magnets of Cu(100)/Co(100)/Cu(100)/Si(100) with 1.8 mm outer diameter, 1.2 mm inner diameter and 34 nm thickness. The samples were magnetically characterised using specially adapted magneto-optic Kerr effect. The measurements show that a two step switching process occurs at high fields, indicating the existence of two different stable states. In addition to the vortex state, which occurs at intermediate fields, we have identified a second state which is also stable at remanence and undergoes a simple and well characterised nucleation free domain wall propagation switching process. Moreover, it is confirmed that the rings reverse by falling into vortex states with different circulation when the field is applied in opposite directions. This means a particular vortex state (clockwise or counter-clockwise) can be prepared using a uniform field only, which can be important for technological applications. In the second part of the talk we use micromagnetic simulations to further explore the potential performance of narrow rings as memory cells in MRAM devices in terms of scalability and switching speed. We introduce two artificial notches at the outer surface of the rings in order to control accurately the depinning fields for the domain walls. According to our simulations, well defined onion states1 and switching by domain wall motion can be achieved for ring diameters down 180 nm. In order to speed up the switching process, two different approaches are considered. In the first one, a field pulse is applied in the plane of the ring and perpendicular to the walls. In this case the walls are depinned effectively and magnetization reversal can be achieved in a few ns. In the second approach, the field is applied perpendicular to the plane of the ring. This field drives the system out of equilibrium and precessional motion causes the walls move around the ring. With this approach, switching times can be lowered down to 220 ps, which is very promising for implementation in MRAM devices. 1. J. Rothman, M. Kläui, L. Lopez-Diaz, C.A.F. Vaz, A. Bleloch, J.A.C. Bland, Z. Cui and R. Speaks, Phys. Rev. Lett. 86, 1098 (2001).

  19. Extracting crack signal of magnetic ring based on MAX262

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Hou, De-xing; Qiu, Jian; Ye, Shu-liang

    2013-01-01

    Magnetic rings are widely used in electronic manufacturing. In the production process, various types of cracks exist, which severely reduce product performance. So it has important practical significance for the efficiency and accuracy detection of the magnetic rings defects. In this paper, a detecting instrument for magnetic rings defects is designed based on magnetostrictive effect, which uses an alternating magnetic field to encourage the ring producing vibration at one end of the ring, and at the other end a vibration transducer is used to catch the vibration signal. Considering that signals of vibration are difficult to obtain, a programmable filter based on the MAX262 chip is designed, using fourth-order Chebyshev band-pass filtering method to extract the weak signal ,which is used to determine the ring cracks. Numerous ring experiments show that this method can effectively detect the ring crack.

  20. Vortex formation in magnetic narrow rings

    NASA Astrophysics Data System (ADS)

    Bland, J. A. C.

    2002-03-01

    Underlying the current interest in magnetic elements is the possibility such systems provide both for the study of fundamental phenomena in magnetism (such as domain wall trapping and spin switching) and for technological applications, such as high density magnetic storage or magnetic random access memories (MRAM). One key issue is to control the magnetic switching precisely. To achieve this one needs first to have a well defined and reproducible remanent state, and second the switching process itself must be simple and reproducible. Among the many studied geometries, rings are shown to exhibit several advantages over other geometries, in that they show relatively simple stable magnetic states at remanence, with fast and simple magnetisation switching mechanisms. This is borne out of our systematic investigation of the magnetic properties of epitaxial and polycrystalline Co rings, where both the static, dynamic and transport properties have been studied. Magnetic measurements and micromagnetic simulations show that for appropriate ring structures a two step switching process occurs at high fields, indicating the existence of two different stable states. In addition to the vortex state, which occurs at intermediate fields, we have identified a new bi-domain state, which we term the `onion state', corresponding to opposite circulation of the magnetisation in each half of the ring. The magnetic elements were fabricated using a new technique based on the pre-patterning of Si ring structures and subsequent epitaxial growth of Cu/Co/Cu sandwich films on top of the Si elements. This technique has allowed the growth of epitaxial fcc Co(001) structures and in contrast to conventional lithographic methods, no damage to the magnetic layer structure is introduced by the patterning process [1,2]. We have studied the magnetic switching properties of arrays of narrow Co(100) epitaxial ring magnets, with outer diameters between 1 μm and 2 μm, varying inner diameters and varying film thickness, using magneto-optic Kerr effect (MOKE) magnetometry. The data indicates that the outer diameter of the ring only plays a minor role in determining the value of the switching field. As a general trend, the switching field decreases with increasing ring width and with decreasing film thickness. In particular, the dependence of the switching field on ring width becomes more pronounced for smaller ring widths. This stems from the fact that the vortex state becomes more stable for the narrower rings due to the exchange energy contribution to the barrier for reversal to the onion state. Thicker films also favour the vortex state over the onion state, since the magnetostatic energy associated with the latter state increases with film thickness [3]. Using micromagnetic simulations we show also that the magnetisation reversal in narrow rings can take place via a nucleation-free domain wall motion process when a field pulse is applied in the plane of the film and perpendicular to the net magnetisation. Switching times of the order of 400 ps can be achieved with this approach. A lower bound for the depinning time of the domain walls and a weak dependence of the domain wall velocity with the applied field are described [4]. The magnetic nanostructure of epitaxial fcc Co/Cu(001) circular elements has been imaged with scanning electron microscopy with polarisation analysis (SEMPA) [5]. The elements vary from disks to rings according to the dimensions of the inner diameter of the ring structure and have a nominal composition 4 nm Au/2 nm Cu/34 nm Co/100 nm Cu. In this study the outer diameter was fixed at 1.7 μm while the smallest ring width varies in the range 0.3-0.5 μm. A closed flux quadrant configuration is observed for some of the disks, characteristic of systems with cubic anisotropy (i.e., near vortex structure), besides other more complex configurations at remanence. The width of the 90^o domain wall in the disks is around 0.20 ± 0.05 μm. This value is larger than what expected for continuous films and is a result of the constraints imposed by the geometry of the element. The value is in good agreement with micromagnetic calculations. For the rings we observe directly the `onion-state', the closest configuration to saturation that these structures allow [1]. The results prove that this state is stable in zero applied field. The internal structure of the two head-to-head domain walls in the onion state is analysed. Wider rings (ring width w=0.5 μm) present vortex walls, whereas thinner ones (ring width w=0.3 μm) exhibit transverse walls [6]. This is in good agreement with micromagnetic simulations. We have also investigated the magnetic states and the switching properties of magnetic rings using magneto-resistance (MR) measurements. We chose narrow rings, where particularly simple magnetic states are expected. Some of the rings have notches of different sizes that help to pin, and thereby define, the positions of domain walls. The rings were fabricated using a multi-stage lift-off process, where six non-magnetic contacts in different positions of the ring were made. The rings consist of polycrystalline Co or Ni_80Fe_20 3-30 nm thick capped with 6 nm Au, with outer ring diameter 1.4 μm, ring width 80 nm, and notches of different sizes. Conventional MR-H loop measurements with a fixed magnetic field direction, and measurements with rotating constant field magnitude were performed. In one example of the first type of MR measurements, the direction of the field and the contacts were chosen so that at saturation the magnetization is perpendicular to the current. As expected, at saturation the resistance is low whereas at remanence it is high. There is a clear two-step switching process between the `onion' state and the vortex state as expected from previous studies on rings [1]. During the first switching the resistance increases, corresponding to the transition into the vortex state. Since no domain wall is present between the contacts, the magnetization is everywhere parallel to the current, and the resistance is high. After the second switching into the reverse `onion' state a domain wall is now present between the contacts. This means some of the magnetization in the transverse domain wall is perpendicular to the current and hence the resistance decreases. This shows that one can clearly distinguish between the onion and vortex state using MR measurements. In addition, using the field dependent voltage drop between different contacts, the switching field at which each part of the ring reverses can be determined. >From the second type of measurements clear hysteretic behaviour is seen, indicating that there is some domain wall pinning. This demonstrates that the position of the domain walls can be identified by looking at the voltage drop between different contacts. By measuring at different magnitudes of the applied field the pinning strength of the domain walls is determined, and in particular the dependence of the domain wall pinning on the notch size. Furthermore the structure of the domain wall changes for different notch sizes, and hence the contribution of the wall to the resistance changes as well. Real-time measurements between different contacts might allow for domain wall speed measurements and other domain wall propagation studies. References: [1] J. Rothman, M. Kläui, L. Lopez-Diaz, C.A.F. Vaz, A. Bleloch, J.A.C. Bland, Z. Cui, R. Speaks, Phys. Rev. Lett. 86 (2001) 1098. [2] Z. Cui, J. Rothman, M. Kläui, L. Lopez-Diaz, C.A.F. Vaz, J.A.C. Bland, to be published. [3] M. Kläui, L. Lopez-Diaz, J. Rothman, C.A.F. Vaz, J.A.C. Bland, Z. Cui, J. Magn. Magn. Mat., to be published. [4] L. Lopez-Diaz, J. Rothman, M. Kläui, J.A.C. Bland, IEEE Trans. Mag. 36 (2000) 3155. [5] C.A.F. Vaz, L. Lopez-Diaz, M. Kläui, J.A.C. Bland, T.L. Monchesky, J. Unguris, Z. Cui, 46th MMM Conference, Seattle, 2001. [6] R. D. McMichael and M. J. Donahue, IEEE Trans. Mag. 33, 4167-4169 (1997).

  1. Comparison of Simulated and Observed Ring Current Magnetic Field and Ion Fluxes and ENA Intensity during the 5 April 2010 Storm

    NASA Astrophysics Data System (ADS)

    Chen, M. W.; Lemon, C.; Guild, T. B.; Schulz, M.; Lui, A.; Keesee, A. M.; Goldstein, J.; Rodriguez, J. V.

    2011-12-01

    In this study we compare simulated and observed stormtime magnetic intensities, proton flux spectra and ENA intensity for the 5 April 2010 storm (minimum Dst ≈ -73 nT) to test how well self-consistent simulations can simultaneously reproduce these quantities. We simulate the ring current and plasma sheet using the magnetically and electrostatically self-consistent Rice Convection Model-Equilibrium (RCM-E) [Lemon et al., JGR, 2004] with a time-varying magnetopause driven by upstream solar wind and interplanetary magnetic field (IMF) conditions. We use ion temperatures inferred from TWINS energetic neutral atom (ENA) images and THEMIS/ESA and SST ion data, and proton densities from the empirical IMF-dependent model of Tsyganenko and Mukai [JGR, 2003] to guide our specification of the plasma sheet at 10 RE, our plasma boundary location in the RCM-E. The oxygen to proton density ratio at the plasma boundary is specified from the empirical Young et al. [JGR, 1982] study. We compare the simulated magnetic intensity with the magnetic intensity measured by magnetometers on the GOES satellites at geosynchronous (GEO) altitude (6.6 Earth radii) and on THEMIS satellites. The simulated and observed proton spectra (GOES-14/MAGPD) at GEO and global ENA intensity (TWINS 1 and 2) are compared. We discuss the response of the ring current magnetic field and ion flux distribution to expansions and compressions of the magnetosphere associated with the dynamic solar wind pressure for this storm event.

  2. The remote sensing of Saturn's rings. 1: The magnetic alinement of the ring particles

    NASA Technical Reports Server (NTRS)

    Evans, L. C.

    1973-01-01

    Because of the potential implications for the optical properties of Saturn's rings, the orientation of nonspherical ring particles at equilibrium is investigated with respect to four stochastic influences: interactions with the interplanetary medium, interactions with the expected magnetic field of Saturn, thermal fluctuations due to the internal temperature of the ring particles; collisions between ring particles. The solution of the homogeneous Fokker-Planck equation for nearly spherical spheroids is presented and investigated in general. Values of the pertinent physical parameters in the vicinity of Saturn are estimated, and the implications for the alignment of the ring particles are investigated. It is concluded that for some alignment mechanisms, small ring particles can be expected to be almost completely aligned. This alignment results in each particle spinning around its shortest body axis with this axis parallel to the magnetic field direction (perpendicular to the ring plane).

  3. Ring magnet firing angle control

    DOEpatents

    Knott, M.J.; Lewis, L.G.; Rabe, H.H.

    1975-10-21

    A device is provided for controlling the firing angles of thyratrons (rectifiers) in a ring magnet power supply. A phase lock loop develops a smooth ac signal of frequency equal to and in phase with the frequency of the voltage wave developed by the main generator of the power supply. A counter that counts from zero to a particular number each cycle of the main generator voltage wave is synchronized with the smooth AC signal of the phase lock loop. Gates compare the number in the counter with predetermined desired firing angles for each thyratron and with coincidence the proper thyratron is fired at the predetermined firing angle.

  4. Stereo ENA Imaging of the Ring Current and Multi-point Measurements of Suprathermal Particles and Magnetic Fields by TRIO-CINEMA

    NASA Astrophysics Data System (ADS)

    Lin, R. P.; Sample, J. G.; Immel, T. J.; Lee, D.; Horbury, T. S.; Jin, H.; SEON, J.; Wang, L.; Roelof, E. C.; Lee, E.; Parks, G. K.; Vo, H.

    2012-12-01

    The TRIO (Triplet Ionospheric Observatory) - CINEMA (Cubesat for Ions, Neutrals, Electrons, & Magnetic fields) mission consists of three identical 3-u cubesats to provide high sensitivity, high cadence, stereo measurements of Energetic Neutral Atoms (ENAs) from the Earth's ring current with ~1 keV FWHM energy resolution from ~4 to ~200 keV, as well as multi-point in situ measurements of magnetic fields and suprathermal electrons (~2 -200 keV) and ions (~ 4 -200 keV) in the auroral and ring current precipitation regions in low Earth orbit (LEO). A new Suprathermal Electron, Ion, Neutral (STEIN) instrument, using a 32-pixel silicon semiconductor detector with an electrostatic deflection system to separate ENAs from ions and from electrons below 30 keV, will sweep over most of the sky every 15 s as the spacecraft spins at 4 rpm. In addition, inboard and outboard (on an extendable 1m boom) miniature magnetoresistive sensor magnetometers will provide high cadence 3-axis magnetic field measurements. An S-band transmitter will be used to provide ~8 kbps orbit-average data downlink to the ~11m diameter antenna of the Berkeley Ground Station.The first CINEMA (funded by NSF) is scheduled for launch on August 14, 2012 into a 65 deg. inclination LEO. Two more identical CINEMAs are being developed by Kyung Hee University (KHU) in Korea under the World Class University (WCU) program, for launch in November 2012 into a Sun-synchronous LEO to form TRIO-CINEMA. A fourth CINEMA is being developed for a 2013 launch into LEO. This LEO constellation of nanosatellites will provide unique measurements highly complementary to NASA's RBSP and THEMIS missions. Furthermore, CINEMA's development of miniature particle and magnetic field sensors, and cubesat-size spinning spacecraft may be important for future constellation space missions. Initial results from the first CINEMA will be presented if available.

  5. Optimal placement of magnets in Indus-2 storage ring

    NASA Astrophysics Data System (ADS)

    Riyasat, Husain; A, D. Ghodke; Singh, Gurnam

    2015-03-01

    In Indus-2, by optimizing the position of the magnetic elements, using the simulated annealing algorithm, at different locations in the ring with their field errors, the effects on beam parameters have been minimized. Closed orbit distortion and beta beat are considerably reduced by optimizing the dipole and quadrupole magnets positions in the ring. For the Indus-2 storage ring, sextupole optimization gives insignificant improvement in dynamic aperture with chromaticity-correcting sextupoles. The magnets have been placed in the ring with the optimized sequence and storage of the beam has been achieved at injection energy without energizing any corrector magnets. Magnet sorting has led to the easy beam current accumulation and the measurement of parameters such as closed orbit distortion, beta function, dispersion, dynamic aperture etc.

  6. Single-ring magnetic cusp low gas pressure ion source

    DOEpatents

    Bacon, Frank M. (Albuquerque, NM); Brainard, John P. (Albuquerque, NM); O'Hagan, James B. (Albuquerque, NM); Walko, Robert J. (Albuquerque, NM)

    1985-01-01

    A single-ring magnetic cusp low gas pressure ion source designed for use in a sealed, nonpumped neutron generator utilizes a cathode and an anode, three electrically floating electrodes (a reflector behind the cathode, a heat shield around the anode, and an aperture plate), together with a single ring-cusp magnetic field, to establish and energy-filtering mechanism for producing atomic-hydrogen ions.

  7. Two-dimensional Magnetism in Arrays of Superconducting Rings

    NASA Astrophysics Data System (ADS)

    Reich, Daniel H.

    1996-03-01

    An array of superconducting rings in an applied field corresponding to a flux of Φ0 /2 per ring behaves like a 2D Ising antiferromagnet. Each ring has two energetically equivalent states with equal and opposite magnetic moments due to fluxoid quantization, and the dipolar coupling between rings favors antiparallel alignment of the moments. Using SQUID magnetometry and scanning Hall probe microscopy, we have studied the dynamics and magnetic configurations of micron-size aluminum rings on square, triangular, honeycomb, and kagomé lattices. We have found that there are significant antiferromagnetic correlations between rings, and that effects of geometrical frustration can be observed on the triangular and kagomé lattices. Long range correlations on the other lattices are suppressed by the analog of spin freezing that locks the rings in metastable states at low temperatures, and by quenched disorder due to imperfections in the fabrication. This disorder produces a roughly 1% variation in the rings' areas, which translates into an effective random field on the spins. The ring arrays are thus an extremely good realization of the 2D random-field Ising model. (Performed in collaboration with D. Davidović, S. Kumar, J. Siegel, S. B. Field, R. C. Tiberio, R. Hey, and K. Ploog.) (Supported by NSF grants DMR-9222541, and DMR-9357518, and by the David and Lucile Packard Foundation.)

  8. Janus Magnetic Rods, Ribbons, and Rings

    NASA Astrophysics Data System (ADS)

    Yan, Jing; Chaudhary, Kundan; Bae, Sung Chul; Lewis, Jennifer; Granick, Steve

    2013-03-01

    Dipolar particles are fundamental building blocks in nature and technology but the roles of anisotropy are seldom explored in their assembly. Here, we fabricate colloidal silica rods coated on one hemicylinder with a thin magnetic layer to satisfy multiple criteria: nearly monodisperse, easily imaged, and magnetic interaction dominant over gravity. We confirm long-predicted features of dipolar assembly and stress the microstructural variety brought about by shape and chemical anisotropy, especially by borrowing knowledge learned from molecules. We describe analogies to liquid crystalline deformations with bend, splay and twist; an analogy to cis/trans isomerism in organic molecules, which in this system can be controllably and reversibly switched; and a field-switching methodology to direct single ribbons into not only single but also multiple rings that can subsequently undergo hierarchical self-assembly. Going beyond earlier investigations of phase behavior, we show that dynamic reconfigurability presents subtle materials issues and possibilities.

  9. Particle simulations of ion rings for magnetic fusion

    SciTech Connect

    Lyster, P.M.

    1987-01-01

    This thesis contains a numerical study of the dynamics of axis encircling charged particles in ion rings and layers. Part of this work deals with the coalescence of ion rings to form field reversed rings, which may be useful for Compact Torus magnetic fusion reactors. The coalescence of weak ion rings with Compact Toroids is also investigated. This is important because a component of energetic particles may help to maintain the flux or stabilize these configurations against a number of macroscopic magnetohydrodynamic instabilities. Several different types of particle codes are used. RINGA and CIDER are two and one half-dimensional codes in cylindrical axisymmetric geometry. A theoretical and computational study is made of a mechanism by which ring translational energy is transferred to Alfven waves in a conductive plasma. A new collective phenomenon is discussed whereby the merging of rings is improved if they have stronger initial self fields. A study is made of the coalescence of strong field-reversed ion rings in highly conductive plasmas, in which it is found that magnetic field line reconnection is an important process. Finally, a study of the magnetic compression of ion layers in conductive plasmas is presented.

  10. Magnetic field characterization, re-tuning and first operation of the NIST undulator on the Duke 1 GeV storage ring

    NASA Astrophysics Data System (ADS)

    Johnson, L. E.; Denbeaux, G.; Madey, J. M. J.

    2000-06-01

    Originally built for an IR FEL project at the National Institute of Standards and Technology, the NIST undulator was acquired by Duke for use as a soft x-ray source on the 1 GeV storage ring. The Brobeck Division of Maxwell Laboratories constructed this 3.64 m long hybrid-design undulator. Initial Hall probe measurements on the magnetic field distribution of the undulator revealed field errors of more than 0.80% RMS. Initial phase errors for the device were more than 11 degrees. A series of in-situ and off-line measurements and modifications were employed to re-tune the magnetic field structure. Initial goals for the device called for the production of strong spectral characteristics through the 5th harmonic. Although rms field errors remained rather high (˜0.75%), phase errors were reduced to less than 5 degrees. A diagnostic beamline including a transmission grating spectrometer and a scanning wire beam profile monitor was constructed to characterize the spatial and spectral characteristics of the radiation. We report on this effort and the resulting first operation of this undulator source.

  11. Magnetic fields at neptune.

    PubMed

    Ness, N F; Acuña, M H; Burlaga, L F; Connerney, J E; Lepping, R P; Neubauer, F M

    1989-12-15

    The National Aeronautics and Space Administration Goddard Space Flight Center-University of Delaware Bartol Research Institute magnetic field experiment on the Voyager 2 spacecraft discovered a strong and complex intrinsic magnetic field of Neptune and an associated magnetosphere and magnetic tail. The detached bow shock wave in the supersonic solar wind flow was detected upstream at 34.9 Neptune radii (R(N)), and the magnetopause boundary was tentatively identified at 26.5 R(N) near the planet-sun line (1 R(N) = 24,765 kilometers). A maximum magnetic field of nearly 10,000 nanoteslas (1 nanotesla = 10(-5) gauss) was observed near closest approach, at a distance of 1.18 R(N). The planetary magnetic field between 4 and 15 R(N) can be well represented by an offset tilted magnetic dipole (OTD), displaced from the center of Neptune by the surprisingly large amount of 0.55 R(N) and inclined by 47 degrees with respect to the rotation axis. The OTD dipole moment is 0.133 gauss-R(N)(3). Within 4 R(N), the magnetic field representation must include localized sources or higher order magnetic multipoles, or both, which are not yet well determined. The obliquity of Neptune and the phase of its rotation at encounter combined serendipitously so that the spacecraft entered the magnetosphere at a time when the polar cusp region was directed almost precisely sunward. As the spacecraft exited the magnetosphere, the magnetic tail appeared to be monopolar, and no crossings of an imbedded magnetic field reversal or plasma neutral sheet were observed. The auroral zones are most likely located far from the rotation poles and may have a complicated geometry. The rings and all the known moons of Neptune are imbedded deep inside the magnetosphere, except for Nereid, which is outside when sunward of the planet. The radiation belts will have a complex structure owing to the absorption of energetic particles by the moons and rings of Neptune and losses associated with the significant changes in the diurnally varying magnetosphere configuration. In an astrophysical context, the magnetic field of Neptune, like that of Uranus, may be described as that of an "oblique" rotator. PMID:17756002

  12. Creation of magnetized jet using a ring of laser beams

    NASA Astrophysics Data System (ADS)

    Fu, Wen; Liang, Edison P.; Tzeferacos, Petros; Lamb, Donald Q.

    2015-12-01

    We propose a new way of generating magnetized supersonic jets using a ring laser to irradiate a flat surface target. Using 2D FLASH code simulations which include the Biermann Battery term, we demonstrate that strong toroidal fields can be generated and sustained downstream in the collimated jet outflow far from the target surface. The field strength can be controlled by varying the ring laser separation, thereby providing a versatile laboratory platform for studying the effects of magnetic field in a variety of astrophysical settings.

  13. Particle Simulations of Ion Rings for Magnetic Fusion.

    NASA Astrophysics Data System (ADS)

    Lyster, Peter Michael

    1987-09-01

    This thesis contains a numerical study of the dynamics of axis encircling charged particles in ion rings and layers. Part of this work deals with the coalescence of ion rings to form field reversed rings, which may be useful for Compact Torus magnetic fusion reactors. The coalescence of weak ion rings with Compact Toroids is also investigated. This is important because a component of energetic particles may help to maintain the flux or stabilize these configurations against a number of macroscopic magnetohydrodynamic instabilities. Several different types of particle codes are used. RINGA and CIDER are two and one half-dimensional codes in cylindrical axisymmetric geometry. For the RINGA code, a simple Ohm's law is used for modeling a resistive background plasma. For CIDER, the massless electron momentum equation is used for modeling a conductive background plasma. In a resistive plasma, ring coalescence can be achieved if the initial relative translational velocity is not excessive, and if the plasma conductivity is chosen to maximize the dissipation of ring energy. A theoretical and computational study is made of a mechanism by which ring translational energy is transferred to Alfven waves in a conductive plasma. A new collective phenomenon is discussed, whereby the merging of rings is improved if they have stronger initial self fields. A study is made of the coalescence of strong field-reversed ion rings in highly conductive plasmas, in which it is found that magnetic field line reconnection is an important process. Finally, a study of the magnetic compression of ion layers in conductive plasmas is presented. BAGSHAW, a one-dimensional particle code which treats the background plasma in the two fluid approximation, was developed for this purpose. Compression on a timescale which is comparable with the Alfven transit time may create considerable transients in the system. In a one-dimensional system, the plasma return current does not cancel the increase in the layer current which occurs during magnetic compression.

  14. Progress Report on the g-2 Storage Ring Magnet System

    SciTech Connect

    Bunce, G.A.; Cullen, J.; Danby, G.; Green, M.A.; Jackson, J.; Jia, L.; Krienen, F.; Meier, R.; Meng, W.; Morse, W.; Pai, C.; Polk, I.; Prodell, A.; Shutt, R.; Snydstrup, L.; Yamamoto, A.

    1995-06-01

    The 3.1 GeV muon storage ring for the g-2 experiment at Brookhaven National Laboratory has three large solenoid magnets that form a continuous 1.451 tesla storage ring dipole with an average beam bend radius of 7.1 meters. In addition to the three storage ring solenoids, there is an inflector dipole with nested dipole coils that create very little stray magnetic field. A superconducting shield on the inflector gets rid of most of the remaining stray flux. This paper reports on the progress made on the storage ring solenoid magnet system and the inflector as of June 1995. The results of cryogenic system tests are briefly reported.

  15. Stability of equilibrium of a superconducting ring that levitates in the field of a fixed ring with constant current

    NASA Astrophysics Data System (ADS)

    Bishaev, A. M.; Bush, A. A.; Gavrikov, M. B.; Kamentsev, K. E.; Kozintseva, M. V.; Savel'ev, V. V.; Sigov, A. S.

    2015-11-01

    In order to develop a plasma trap with levitating superconducting magnetic coils, it is necessary to search for their stable levitating states. An analytical expression for the potential energy of a single superconducting ring that captures a fixed magnetic flux in the field of a fixed ring with constant current versus the coordinate of the free ring on the axis of the system, deviation angle of its axis from the axis of the system, and radial displacement of its plane is derived for uniform gravity field in the thin ring approximation. The calculated stable levitation states of the superconducting ring in the field of the ring with constant current are proven in experiments. The generalization of such an approach to the levitation of several rings makes it possible to search for stable levitation states of several coils that form a magnetic system of a multipole trap.

  16. Magnetic record associated with tree ring density: possible climate proxy.

    PubMed

    Kletetschka, Gunther; Pruner, Petr; Venhodova, Daniela; Kadlec, Jaroslav

    2007-01-01

    A magnetic signature of tree rings was tested as a potential paleo-climatic indicator. We examined wood from sequoia tree, located in Mountain Home State Forest, California, whose tree ring record spans over the period 600 - 1700 A.D. We measured low and high-field magnetic susceptibility, the natural remanent magnetization (NRM), saturation isothermal remanent magnetization (SIRM), and stability against thermal and alternating field (AF) demagnetization. Magnetic investigation of the 200 mm long sequoia material suggests that magnetic efficiency of natural remanence may be a sensitive paleoclimate indicator because it is substantially higher (in average >1%) during the Medieval Warm Epoch (700-1300 A.D.) than during the Little Ice Age (1300-1850 A.D.) where it is <1%. Diamagnetic behavior has been noted to be prevalent in regions with higher tree ring density. The mineralogical nature of the remanence carrier was not directly detected but maghemite is suggested due to low coercivity and absence of Verwey transition. Tree ring density, along with the wood's magnetic remanence efficiency, records the Little Ice Age (LIA) well documented in Europe. Such a record suggests that the European LIA was a global phenomenon. Magnetic analysis of the thermal stability reveals the blocking temperatures near 200 degree C. This phenomenon suggests that the remanent component in this tree may be thermal in origin and was controlled by local thermal condition. PMID:17381844

  17. Condenser for illuminating a ring field

    DOEpatents

    Sweatt, William C.

    1994-01-01

    A series of segments of a parent aspheric mirror having one foci at at a si-point source of radiation and the other foci at the radius of a ring field have all but one or all of their beams translated and rotated by sets of mirrors such that all of the beams pass through the real entrance pupil of a ring field camera about one of the beams and fall onto the ring field radius as a coincident image as an arc of the ring field.

  18. Condenser for illuminating a ring field

    DOEpatents

    Sweatt, W.C.

    1994-11-01

    A series of segments of a parent aspheric mirror having one foci at a point source of radiation and the other foci at the radius of a ring field have all but one or all of their beams translated and rotated by sets of mirrors such that all of the beams pass through the real entrance pupil of a ring field camera about one of the beams and fall onto the ring field radius as a coincident image as an arc of the ring field. 5 figs.

  19. Magnet design for a low-emittance storage ring

    PubMed Central

    Johansson, Martin; Anderberg, Bengt; Lindgren, Lars-Johan

    2014-01-01

    The MAX IV 3 GeV storage ring, currently under construction, pursues the goal of low electron beam emittance by using a multi-bend achromat magnet lattice, which is realised by having several consecutive magnet elements precision-machined out of a common solid iron block, 2.3–3.4 m long. With this magnet design solution, instead of having 1320 individual magnets, the MAX IV 3 GeV storage ring is built up using 140 integrated ‘magnet block’ units, containing all these magnet elements. Major features of this magnet block design are compactness, vibration stability and that the alignment of magnet elements within each unit is given by the mechanical accuracy of the CNC machining rather than individual field measurement and adjustment. This article presents practical engineering details of implementing this magnet design solution, and mechanical + magnetic field measurement results from the magnet production series. At the time of writing (spring 2014), the production series, which is totally outsourced to industry, is roughly half way through, with mechanical/magnetic QA conforming to specifications. It is the conclusion of the authors that the MAX IV magnet block concept, which has sometimes been described as new or innovative, is from a manufacturing point of view simply a collection of known mature production methods and measurement procedures, which can be executed at fixed cost with a low level of risk. PMID:25177980

  20. Magnet design for a low-emittance storage ring.

    PubMed

    Johansson, Martin; Anderberg, Bengt; Lindgren, Lars Johan

    2014-09-01

    The MAX IV 3 GeV storage ring, currently under construction, pursues the goal of low electron beam emittance by using a multi-bend achromat magnet lattice, which is realised by having several consecutive magnet elements precision-machined out of a common solid iron block, 2.3-3.4 m long. With this magnet design solution, instead of having 1320 individual magnets, the MAX IV 3 GeV storage ring is built up using 140 integrated `magnet block' units, containing all these magnet elements. Major features of this magnet block design are compactness, vibration stability and that the alignment of magnet elements within each unit is given by the mechanical accuracy of the CNC machining rather than individual field measurement and adjustment. This article presents practical engineering details of implementing this magnet design solution, and mechanical + magnetic field measurement results from the magnet production series. At the time of writing (spring 2014), the production series, which is totally outsourced to industry, is roughly half way through, with mechanical/magnetic QA conforming to specifications. It is the conclusion of the authors that the MAX IV magnet block concept, which has sometimes been described as new or innovative, is from a manufacturing point of view simply a collection of known mature production methods and measurement procedures, which can be executed at fixed cost with a low level of risk. PMID:25177980

  1. Isochronous field study of the Rare-RI Ring

    NASA Astrophysics Data System (ADS)

    Abe, Y.; Yamaguchi, Y.; Wakasugi, M.; Uesaka, T.; Ozawa, A.; Suzaki, F.; Nagae, D.; Miura, H.; Yamaguchi, T.; Yano, Y.

    2015-11-01

    Construction of the Rare-RI Ring to measure masses of short-lived rare-RI with a relative precision of 10-6 is in progress at RIKEN. The Rare-RI Ring consists of six sectors where each sector consists of four dipole magnets. Since the mass measurement is done by the isochronous mass spectrometry in the Rare-RI Ring, creating isochronous magnetic field is one of the important issues in mass measurements with the Rare-RI Ring. In order to make an isochronous field, we installed ten trim coils in the two outer dipoles among the four dipoles in each sector magnet. The isochronism of the magnetic field have been confirmed by measuring time-of-flight (TOF) of alpha particles from an alpha-source (241Am). We measured TOF of alpha particles while changing the radial gradient of the magnetic field by trim coils and evaluated the isochronism from standard deviation of the TOF spectrum. The TOF width is minimum for a radial gradient of magnetic field (\\partial {B}z/\\partial r)/B0 = 0.205 m-1, which is in good agreement with the simulated value.

  2. Generation of vortex rings by nonstationary laser wake field

    SciTech Connect

    Tsintsadze, N.L.; Murtaza, G.; Shah, H.A.

    2006-01-15

    A new concept of generating quasistatic magnetic fields, vortex rings, and electron jets in an isotropic homogeneous plasma is presented. The propagation of plasma waves, generated by a relativistically intense short pulse laser, is investigated by using the kinetic model and a novel nonpotential, time-dependent ponderomotive force is derived by obtaining a hydrodynamic equation of motion. This force can in turn generate quasistatic magnetic fields, vortex rings, and electron jets. It is also shown that the vortex rings can become a means for accelerating electrons, which are initially in equilibrium. The conservation of canonical momentum circulation and the frozen-in condition for the vorticity is discussed. The excitation of the vortex waves by the modulation of the amplitude of the plasma waves is considered. These vortex waves, which generate a lower hybrid mode propagating across the generated magnetic field, are also investigated.

  3. Spin wave spectra in perpendicularly magnetized permalloy rings

    SciTech Connect

    Zhou, X.; Ding, J.; Adeyeye, A. O.; Kostylev, M.

    2015-03-16

    The dynamic behavior of perpendicularly magnetized permalloy circular rings is systematically investigated as a function of film thickness using broadband field modulated ferromagnetic resonance spectroscopy. We observed the splitting of one spin wave mode into a family of dense resonance peaks for the rings, which is markedly different from the single mode observed for continuous films of the same thickness. As the excitation frequency is increased, the mode family observed for the rings gradually converges into one mode. With the increase in the film thickness, a sparser spectrum of modes is observed. Our experimental results are in qualitative agreement with the dynamic micromagnetic simulations.

  4. Permanent magnet sextupole protocol and tolerances for the damping rings

    SciTech Connect

    Spencer, J.E.

    1985-09-05

    Response is given to various questions on alignment tolerances for the permanent magnet sextupoles (PMS's) in the damping rings. Consideration is given to rotational errors, strength/longitudinal placement errors, transverse placement errors, pitch/yaw or tilt errors, and harmonic field errors. Resulting error limits can be specified in terms of the maximum errors allowed in the distribution. (LEW)

  5. The g-2 storage ring superconducting magnet system

    SciTech Connect

    Green, M.A.; g-2 Collaboration

    1993-09-01

    The g-2 {mu} lepton (muon) storage ring is a single dipole magnet that is 44 meters in circumference. The storage ring dipole field is created by three large superconducting solenoid coils. A single outer solenoid, 15.1 meters in diameter, carries 254 kA. Two inner solenoids, 13.4 meters in diameter, carry 127 kA each in opposition to the current carried by the outer solenoid. A room temperature C shaped iron yoke returns the magnetic flux and shapes the magnetic field in a 180 mm gap where the stored muon beam circulates. The gap induction will be 1.47 T. This report describes the three large superconducting solenoids, the cryogenic system needed to keep them cold, the solenoid power supply and the magnet quench protection system.

  6. Inhomogeneities in spin states and magnetization reversal of geometrically identical elongated Co rings

    NASA Astrophysics Data System (ADS)

    Gao, X. S.; Adeyeye, A. O.; Goolaup, S.; Singh, N.; Jung, W.; Castaño, F. J.; Ross, C. A.

    2007-05-01

    The magnetic configurations and magnetic reversal processes in arrays of geometrically identical rounded rectangular Co rings have been investigated. Magnetic imaging reveals a range of configurations, including diagonal onion, horseshoe onion, and vortex states. Reversal from the onion to the vortex state can occur via different routes involving domain wall motion within the rings, and the mechanism depends on the applied field orientation.

  7. Storm-scale ring current morphology inferred from high-resolution empirical magnetic field modeling: storms driven by CMEs, CIRs, and those containing sawtooth and SMC events

    NASA Astrophysics Data System (ADS)

    Stephens, G. K.; Sitnov, M. I.; Ukhorskiy, A. Y.; Ohtani, S.; Vandegriff, J. D.

    2012-12-01

    In spite of several decades of intense investigations, the detailed structure and dynamics of the magnetospheric currents remains unclear especially during disturbed periods associated with magnetic storms and substorms. Until recently, empirical magnetic field models were strongly limited because they were built using predefined, hand-made current structures. New capabilities in the empirical reconstruction of the storm-scale current morphology and its evolution have become possible in the new-generation empirical model, TS07D, where the distribution of storm-scale equatorial currents is determined by regular basis function expansions and is largely dictated by data. We discuss the results of TS07D-based empirical reconstruction of the magnetospheric currents for differing global conditions. Firstly, we examine storms produced by two different drivers, Coronal Mass Ejections (CME) and Corotating Interaction Regions (CIR), and secondly, we examine storms containing two different magnetospheric convection states, those containing quasi-periodic sawtooth events and Steady Magnetospheric Convection (SMC) intervals. A distinctive feature of CME-driven storms is the hook-shaped current developing in the main phase, which combines features of ring and tail currents, while CIR-driven storms are featured by the belt-shaped current and strong reduction of the strength of field-aligned currents. Storms containing sawtooth injections are characterized by the formation of the equatorial storm-time current with an unusually broad radial extension, far beyond geosynchronous orbit across all local times. SMC periods are distinguished by a higher total pressure in the inner magnetosphere extending to larger distances with the appropriate changes in the equatorial currents and their closure paths. New data analysis opportunities offered by the APL-hosted model interface, including run-on-request case studies, the database of pre-processed model coefficients and radiation belt studies are also discussed.

  8. The Storage Ring Magnets of the Australian Synchrotron

    SciTech Connect

    Barg, B.; Jackson, A.; LeBlanc, G.; Huttel, E.; Tanabe, J.; /SLAC

    2005-05-11

    A 3 GeV Synchrotron Radiation Source is being built in Melbourne, Australia. Commissioning is foreseen in 2006. The Storage ring has a circumference of 216 m and has a 14 fold DBA structure. For the storage ring the following magnets will be installed: 28 dipoles with a field of 1.3 T, and a gradient of 3.35 T/m; 56 quadrupoles with a gradient of 18 T/m and 28 with a gradient of 10 T/m; 56 sextupoles with a strength of B'' = 350 T/m and 42 with 150 T/m. The sextupoles are equipped with additional coils for horizontal and vertical steering and for a skew quadrupole. The pole profile was determined by scaling the pole profile of the SPEAR magnets [1] to the aperture of the ASP magnets. The magnets are to be supplied by Buckley Systems Ltd in Auckland, New Zealand.

  9. Localization for robotic capsule looped by axially magnetized permanent-magnet ring based on hybrid strategy

    PubMed Central

    Yang, Wanan; Li, Yan; Qin, Fengqing

    2015-01-01

    To actively maneuver a robotic capsule for interactive diagnosis in the gastrointestinal tract, visualizing accurate position and orientation of the capsule when it moves in the gastrointestinal tract is essential. A possible method that encloses the circuits, batteries, imaging device, etc into the capsule looped by an axially magnetized permanent-magnet ring is proposed. Based on expression of the axially magnetized permanent-magnet rings magnetic fields, a localization and orientation model was established. An improved hybrid strategy that combines the advantages of particle-swarm optimization, clone algorithm, and the LevenbergMarquardt algorithm was found to solve the model. Experiments showed that the hybrid strategy has good accuracy, convergence, and real time performance. PMID:25733935

  10. Magnetic thin film Fe ring structures and devices

    NASA Astrophysics Data System (ADS)

    Hou, Yufeng

    Magnetic thin film ring structures show distinct magnetic states and highly reproducible switching behavior, which makes them candidates for multiple magnetoelectronic and sensing devices. The magnetic states and switching behaviors of thin film ring structures are closely related to their physical properties such as the lateral size, thickness, width and the material anisotropy. In order to systematically study the magnetic properties of thin film ring structures, we use different techniques such as photolithography and electron-beam lithography to fabricate magnetic thin film Fe ring structures with different outer diameter (Dout), thickness (tFe) and inner-to-outer diameter ratio ( Din/Dout). The magnetization reversal processes of these Fe ring structures are studied using magneto-optical Kerr effect and magnetic force microscopy. To explain the magnetic behavior of the Fe ring structures observed in experiments, we use LLG micromagnetic simulation to model the domain configuration of the Fe ring during switching. The evolution of magnetic reversal behaviors in Fe ring structures is also explained by calculating the energy densities of vortex state, single-domain state and axial state with micromagnetic simulator. To control the magnetic switching behavior of the Fe ring structures, exchange bias interfacial coupling is introduced into the ring structure by growing a bilayer of IrMn/Fe in the ring structure. By studying the angular dependence of the hysteresis loop shift, we find that exchange bias induces a magnetic unidirectional anisotropy and a collinear magnetic uniaxial anisotropy in the ring structure. Exchange bias induced magnetic anisotropies cause anisotropic magnetic reversal modes in IrMn/Fe (10 nm) ring and a higher one-step to two-step transitional thickness in IrMn/Fe (x nm) ring structures. After study the magnetic properties of the Fe rings and exchange biased IrMn/Fe rings, we incorporate them into one ring shape magnetic tunneling junction device with current perpendicular to plane configuration. In the ring-MTJ device, a Fe ring free layer and an exchange biased IrMn/Fe ring pinned layer are sandwiched by an MgO barrier layer between them. Depending on the relative orientation of the magnetization in the Fe ring and IrMn/Fe ring, the resistance of the device is higher when they are antiparallel than parallel, which may be used as memory element in a magnetoresistive random-access memory.

  11. A volume birdcage coil with an adjustable sliding tuner ring for neuroimaging in high field vertical magnets: ex and in vivo applications at 21.1 T

    PubMed Central

    Qian, Chunqi; Masad, Ihssan S.; Rosenberg, Jens T.; Elumalai, Malathy; Brey, William W.; Grant, Samuel C.; Gor’kov, Peter L.

    2012-01-01

    A tunable 900 MHz transmit/receive volume coil was constructed for 1H MR imaging of biological samples in a 21.1 T vertical bore magnet. To accommodate a diverse range of specimen and RF loads at such a high frequency, a sliding-ring adaptation of a low-pass birdcage was implemented through simultaneous alteration of distributed capacitance. To make efficient use of the constrained space inside the vertical bore, a modular probe design was implemented with a bottom-adjustable tuning and matching apparatus. The sliding ring coil displays good homogeneity and sufficient tuning range for different samples of various dimensions representing large span of RF loads. High resolution in vivo and ex vivo images of large rats (up to 350 g), mice and human postmortem tissues were obtained to demonstrate coil functionality and to provide examples of potential applications at 21.1 T. PMID:22750638

  12. A volume birdcage coil with an adjustable sliding tuner ring for neuroimaging in high field vertical magnets: Ex and in vivo applications at 21.1 T

    NASA Astrophysics Data System (ADS)

    Qian, Chunqi; Masad, Ihssan S.; Rosenberg, Jens T.; Elumalai, Malathy; Brey, William W.; Grant, Samuel C.; Gor'kov, Peter L.

    2012-08-01

    A tunable 900 MHz transmit/receive volume coil was constructed for 1H MR imaging of biological samples in a 21.1 T vertical bore magnet. To accommodate a diverse range of specimen and RF loads at such a high frequency, a sliding-ring adaptation of a low-pass birdcage was implemented through simultaneous alteration of distributed capacitance. To make efficient use of the constrained space inside the vertical bore, a modular probe design was implemented with a bottom-adjustable tuning and matching apparatus. The sliding ring coil displays good homogeneity and sufficient tuning range for different samples of various dimensions representing large span of RF loads. High resolution in vivo and ex vivo images of large rats (up to 350 g), mice and human postmortem tissues were obtained to demonstrate coil functionality and to provide examples of potential applications at 21.1 T.

  13. Quadrupole magnet for the APS (Advanced Photon Source) storage ring

    SciTech Connect

    Thompson, K.M.; Kim, S.H.; Lari, R.J.; Turner, L.R.; Vector Fields Ltd., Aurora, IL; Argonne National Lab., IL )

    1989-01-01

    An asymmetric core geometry has been selected for the quadrupole magnets in the storage ring of the Advanced Photon Source (APS) in order to accommodate the vacuum chamber and photon beam pipes. The requirements of the position beam make it necessary that the magnet be able to produce a field gradient of 20-T/m with high accuracy. The design for this magnet has been fully developed in preparation for the construction of a prototype. Some unique features included in the design are described. Design choices are being validated by extensive magnetic-field calculations in both two and three dimensions. The results of these calculations are presented. 6 refs., 4 figs., 5 tabs.

  14. Large magnetic storage ring for Bose-Einstein condensates

    SciTech Connect

    Arnold, A. S.; Garvie, C. S.; Riis, E.

    2006-04-15

    Cold atomic clouds and Bose-Einstein condensates have been stored in a 10 cm diameter vertically oriented magnetic ring. An azimuthal magnetic field enables low-loss propagation of atomic clouds over a total distance of 2 m, with a heating rate of less than 50 nK/s. The vertical geometry was used to split an atomic cloud into two counter-rotating clouds which were recombined after one revolution. The system will be ideal for studying condensate collisions and ultimately Sagnac interferometry.

  15. Magnetically induced pumping and memory storage in quantum rings

    NASA Astrophysics Data System (ADS)

    Cini, Michele; Perfetto, Enrico

    2011-12-01

    Nanoscopic rings pierced by external magnetic fields and asymmetrically connected to wires behave in sharp contrast with classical expectations. By studying the real-time evolution of tight-binding models in different geometries, we show that the creation of a magnetic dipole by a bias-induced current is a process that can be reversed: connected rings excited by an internal ac flux produce ballistic currents in the external wires. In particular we point out that by employing suitable flux protocols, single-parameter nonadiabatic pumping can be achieved, and an arbitrary amount of charge can be transferred from one side to the other. We also propose a setup that could serve a memory device, in which both the operations of writing and erasing can be efficiently performed.

  16. The Magnetic and Shielding Effects of Ring Current on Radiation Belt Dynamics

    NASA Technical Reports Server (NTRS)

    Fok, Mei-Ching

    2012-01-01

    The ring current plays many key roles in controlling magnetospheric dynamics. A well-known example is the magnetic depression produced by the ring current, which alters the drift paths of radiation belt electrons and may cause significant electron flux dropout. Little attention is paid to the ring current shielding effect on radiation belt dynamics. A recent simulation study that combines the Comprehensive Ring Current Model (CRCM) with the Radiation Belt Environment (RBE) model has revealed that the ring current-associated shielding field directly and/or indirectly weakens the relativistic electron flux increase during magnetic storms. In this talk, we will discuss how ring current magnetic field and electric shielding moderate the radiation belt enhancement.

  17. Controlling the magnetic susceptibility in an artificial elliptical quantum ring by magnetic flux and external Rashba effect

    SciTech Connect

    Omidi, Mahboubeh Faizabadi, Edris

    2015-03-21

    Magnetic susceptibility is investigated in a man-made elliptical quantum ring in the presence of Rashba spin-orbit interactions and the magnetic flux. It is shown that magnetic susceptibility as a function of magnetic flux changes between negative and positive signs periodically. The periodicity of the Aharonov-Bohm oscillations depends on the geometry of the region where magnetic field is applied, the eccentricity, and number of sites in each chain ring (the elliptical ring is composed of chain rings). The magnetic susceptibility sign can be reversed by tuning the Rashba spin-orbit strength as well. Both the magnetic susceptibility strength and sign can be controlled via external spin-orbit interactions, which can be exploited in spintronics and nanoelectronics.

  18. The Design and Construction of Permanent Magnet Lambertsons for the Recycler Ring at Fermilab

    NASA Astrophysics Data System (ADS)

    May, M. P.; Foster, G. W.; Jackson, G. J.; Schmitz, T. L.

    1997-05-01

    This paper will show and discuss the simple design of a permanent magnet Lambertson used to extract and inject 8 Gev. beam from the Main Injector Ring to the Recycler Ring, and from the Recycler Ring to the Main Injector. Pictures will show how four different magnets used to form the injection and extraction double dog legs are made from one universal design. Detailed assembly drawings will illustrate the construction techniques using solid pieces of steel instead of laminations. The field strength in both the bending region and the field free region will be discussed along with temperature compensation of the strontium ferrite magnetic bricks.

  19. Multi-ring-shaped optical field

    NASA Astrophysics Data System (ADS)

    Mei, Zhangrong; Zhao, Daomu; Gu, Juguan; Mao, Yonghua

    2016-04-01

    We introduce a novel class of planar random source producing far fields with multi-ring-shaped average intensity patterns by modeling the source degree of coherence, and confirm that such sources are physically genuine. Further, we derive the analytical expressions for the cross-spectral density (CSD) function of the beam-like fields generated by the novel source propagating in free space and in a linear isotropic random medium, and analyze the evolution of the spectral density and the state of coherence. It is shown that at some distance from the source the spectral density of the propagating beam in free space takes on the shape-invariant multi-ring profile, and the number of rings and intensity profiles of the beams can be flexibly adjusted by changing the source parameters. However, in atmospheric turbulence, we find that at sufficiently large distances from the source, the multi-ring profiles are destroyed by the medium, even if it remains such for intermediate distances from the source.

  20. Photospheric magnetic fields

    NASA Technical Reports Server (NTRS)

    Howard, R.

    1972-01-01

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

  1. Intense magnetic field phenomena

    SciTech Connect

    Weisheit, J.

    1994-12-31

    This article surveys three of the many challenging problems involving quantum phenomena in plasmas with magnetic fields B in the range 10{sup 8}--10{sup 10} Gauss: magnetic white dwarf stars, spectroscopic effects of motional (v {times} B) electric fields, and statistical models of many-electron atoms in strong B fields. It has proved difficult to make progress in this regime of field strengths, where Coulomb and magnetic interactions are comparable.

  2. The synchronous orbit magnetic field data set

    NASA Technical Reports Server (NTRS)

    Mcpherron, R. L.

    1979-01-01

    The magnetic field at synchronous orbit is the result of superposition of fields from many sources such as the earth, the magnetopause, the geomagnetic tail, the ring current and field-aligned currents. In addition, seasonal changes in the orientation of the earth's dipole axis causes significant changes in each of the external sources. Main reasons for which the synchronous orbit magnetic field data set is a potentially valuable resource are outlined. The primary reason why synchronous magnetic field data have not been used more extensively in magnetic field modeling is the presence of absolute errors in the measured fields. Nevertheless, there exists a reasonably large collection of synchronous orbit magnetic field data. Some of these data can be useful in quantitative modeling of the earth's magnetic field. A brief description is given of the spacecraft, the magnetometers, the standard graphical data displays, and the digital data files.

  3. Magnetic Fields in Galaxies

    NASA Astrophysics Data System (ADS)

    Zweibel, Ellen G.

    2011-08-01

    The origin and evolution of magnetic fields in the Universe is a cosmological problem. Although exotic mechanisms for magneotgenesis cannot be ruled out, galactic magnetic fields could have been seeded by magnetic fields from stars and accretion disks, and must be continuously regenerated due to the ongoing replacement of the interstellar medium. Unlike stellar dynamos, galactic dynamos operate in a multicomponent gas at low collisionality and high magnetic Prandtl number. Their background turbulence is highly compressible, the plasma β ~ 1, and there has been time for only a few large exponentiation times at large scale over cosmic time. Points of similarity include the importance of magnetic buoyancy, the large range of turbulent scales and tiny microscopic scales, and the coupling between the magnetic field and certain properties of the flow. Understanding the origin and maintenance of the large scale galactic magnetic field is the most challenging aspect of the problem.

  4. Muon Acceleration Using Fixed Field, Alternating Gradient (ffag) Rings

    NASA Astrophysics Data System (ADS)

    Summers, D. J.

    Given their 2.2 ?s lifetime, muons must be accelerated fairly rapidly for a neutrino factory or muon collider. Muon bunches tend to be large. Progress in fixed field, alternating gradient (FFAG) lattices to meet these challenges are reviewed. FFAG magnets are naturally wide; low momentum muons move from the low field side of a gradient magnet to the high field side as they gain energy. This can be exploited to do double duty and allow a large beam admittance without unduly increasing the magnetic field volume. If the amount of RF must be reduced to optimize cost, an FFAG ring can accommodate extra orbits. I describe scaling FFAGs in which the bends in each magnet are energy independent and non-scaling FFAGs in which the bends in each magnet do vary with muon energy. In all FFAG designs the sum of the bends in groups of magnets are constant; otherwise orbits would not close. Ways of keeping the accelerating beam in phase with the RF are described. Finally, a 1 MeV proof of principle scaling FFAG has been built at KEK and began accelerating protons in June 2000 with a 1 kHz repetition rate.

  5. 3D-Simulation Studies of SNS Ring Doublet Magnets

    SciTech Connect

    Wang, J.G.; Tsoupas N.; Venturini, M.

    2005-05-05

    The accumulator ring of the Spallation Neutron Source (SNS) at ORNL employs in its straight sections closely packed quadrupole doublemagnets with large aperture of R=15.1 cm an relatively short iron-to-iron distance of 51.4 cm. These quads have much extended fringe field, and magnetic interferences among them in the doublet assemblies is not avoidable. Though each magnet in the assemblies has been individually mapped to high accuracy of lower than 0.01 percent level, the experimental data including the magnetic interference effect will not be available. We have performed 3D computing simulations on a quadrupole doublet model in order to assess the degree of the interference and to obtain relevant data for the SNS commissioning and operation.

  6. Exact physical model for magnets in storage rings

    SciTech Connect

    Maletic, D.; Ruggiero, A.G.

    1992-12-31

    In this report we try to make estimates of both kinematic and field effects on the stability of a particle motion, by employing a truly Maxwellian representation of the magnetic field in exact equations of motion. For this purpose we adopt a simple FODO cell model, which repeats periodically to infinity. This model includes only quadrupoles and drifts, leaving out the bending magnets to avoid the problem of the trajectory curvature. We think this model is a physically consistent approximation of a storage ring. We derive several models with different levels of approximation and compare them by evaluating the importance of these effects. The relevance to long-term stability is being investigated in the meantime by comparing the different models with extensive computer simulations. The results will be shown in a subsequent report.

  7. The magnetic field of Jupiter

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.; Ness, N. F.

    1976-01-01

    The paper is concerned mainly with the intrinsic planetary field which dominates the inner magnetosphere up to a distance of 10 to 12 Jovian radii where other phenomena, such as ring currents and diamagnetic effects of trapped charged particles, become significant. The main magnetic field of Jupiter as determined by in-situ observations by Pioner 10 and 11 is found to be relatively more complex than a simple offset tilted dipole. Deviations from a simple dipole geometry lead to distortions of the charged particle L shells and warping of the magnetic equator. Enhanced absorption effects associated with Io and Amalthea are predicted. The results are consistent with the conclusions derived from extensive radio observations at decimetric and decametric wavelengths for the planetary field.

  8. Magnetic field generator

    DOEpatents

    Krienin, Frank

    1990-01-01

    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.

  9. On Cosmic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Florido, E.; Battaner, E.

    2010-12-01

    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.

  10. Asymmetric dipolar ring

    DOEpatents

    Prosandeev, Sergey A.; Ponomareva, Inna V.; Kornev, Igor A.; Bellaiche, Laurent M.

    2010-11-16

    A device having a dipolar ring surrounding an interior region that is disposed asymmetrically on the ring. The dipolar ring generates a toroidal moment switchable between at least two stable states by a homogeneous field applied to the dipolar ring in the plane of the ring. The ring may be made of ferroelectric or magnetic material. In the former case, the homogeneous field is an electric field and in the latter case, the homogeneous field is a magnetic field.

  11. Transition of polarized ions through the system of ring permanent magnets

    NASA Astrophysics Data System (ADS)

    Fimushkin, V. V.; Gapienko, I. V.; Plis, Yu A.; Prokofichev, Yu V.

    2016-02-01

    The task of the transportation of the polarized proton and deuteron beam of an energy 10-20 keV in the given magnetic field is considered. Specifically the magnetic field is produced by the system of a solenoid and some ring permanent magnets with contrary directed field. The Lorentz equations together with classic equations for vector and tensor polarizations have been solved. The results of the numerical simulation for a simple two- ring system are presented, which shows there is no essential depolarization in agrement with theoretical estimation.

  12. Magnetic Fields in Galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    Magnetic fields are a major agent in the interstellar medium. They contribute significantly to the total pressure which balances the gas disk against gravitation. They affect the gas flows in spiral arms (Gómez and Cox, 2002). The effective sound speed of the gas is increased by the presence of strong fields which reduce the shock strength. The interstellar fields are closely connected to gas clouds. They affect the dynamics of the gas clouds (Elmegreen, 1981; de Avillez and Breitschwerdt, 2004). The stability and evolution of gas clouds are also influenced by magnetic fields, but it is not understood how (Crutcher, 1999; see Chap. 7). Magnetic fields are essential for the onset of star formation as they enable the removal of angular momentum from the protostellar cloud during its collapse (magnetic braking, Mouschovias, 1990). Strong fields may shift the stellar mass spectrum towards the more massive stars (Mestel, 1990). MHD turbulence distributes energy from supernova explosions within the ISM (Subramanian, 1998) and regenerates the field via the dynamo process (Wielebinski, R., Krause, 1993, Beck et al., 1996; Sect. 6). Magnetic reconnection is a possible heating source for the ISM and halo gas (Birk et al., 1998). Magnetic fields also control the density and distribution of cosmic rays in the ISM. A realistic model for any process in the ISM needs basic information about the magnetic field which has to be provided by observations.

  13. Cobalt double-ring and double-dot structures: Magnetic properties

    NASA Astrophysics Data System (ADS)

    López-Urías, F.; Torres-Heredia, J. J.; Muñoz-Sandoval, E.

    2016-02-01

    The magnetization reversal mechanism of nanostructures of cobalt double-rings (D-rings) and double-dots (D-dots) is investigated in the framework of micromagnetic simulations. The arrays contain two identical coupled rings (wide and narrow) or dots with outer diameter of 200 nm and thicknesses ranging from 2-20 nm. Hysteresis loops, dipole-dipole and exchange energies are systematically calculated for the cases of the structures touching and the structures with a 50-nm inter-magnet separation; moreover, magnetization states along the hysteresis curve are analyzed. The results of both dot and ring D-magnets are compared with the corresponding individual magnets. Our results reveal that all D-ring (in contact and separated) arrays containing narrow rings exhibit non-null remanent magnetization; furthermore, higher coercive fields are promoted when the magnet thickness is increased. It is observed that the magnetization reversal is driven mainly by a clockwise rotation of onion-states, followed by states of frustrated vortices. Our results could help improve the understanding of the magnetic interactions in nanomagnet arrays.

  14. Colloidal ribbons and rings from Janus magnetic rods.

    PubMed

    Yan, Jing; Chaudhary, Kundan; Chul Bae, Sung; Lewis, Jennifer A; Granick, Steve

    2013-01-01

    Dipolar particles are fundamental building blocks in nature and technology, yet the effect of particle anisotropy is seldom explored. Here, we fabricate colloidal silica rods coated with a hemicylindrical magnetic layer to satisfy multiple criteria: nearly monodisperse, easily imaged and magnetic interaction that dominates over gravity. We confirm long-predicted features of dipolar assembly and stress the microstructural variety brought about by shape and constituent anisotropy, especially by extrapolating knowledge learned from literal molecules. In this colloidal system, we describe analogies to liquid crystalline deformations with bend, splay and twist; an analogy to cis/trans isomerism in organic molecules, which in our system can be controllably and reversibly switched; and a field-switching methodology to direct single ribbons into not only single but also multiple rings that can subsequently undergo hierarchical self-assembly. We highlight subtle material issues of control and design rules for reconfigurable dipolar materials with building blocks of complex shape. PMID:23443544

  15. Interplanetary magnetic field and geomagnetic Dst variations.

    NASA Technical Reports Server (NTRS)

    Patel, V. L.; Desai, U. D.

    1973-01-01

    The interplanetary magnetic field has been shown to influence the ring current field represented by Dst. Explorer 28 hourly magnetic field observations have been used with the hourly Dst values. The moderate geomagnetic storms of 60 gammas and quiet-time fluctuations of 10 to 30 gammas are correlated with the north to south change of the interplanetary field component perpendicular to the ecliptic. This change in the interplanetary field occurs one to three hours earlier than the corresponding change in the Dst field.

  16. Polar magnetic field reversal.

    NASA Astrophysics Data System (ADS)

    Benevolenskaya, E. E.

    2006-08-01

    The polar magnetic fields on the Sun have been an attractive subject for solar researches since Babcocks measured them in solar cycle 19 (Babcock and Babcock, 1955). One of the remarkable features of the polar magnetic fields is their reversal during the maxima of 11-year sunspot cycles (Babcock and Livingston, 1958; Babcock, 1959). I have present results of the investigations of the polar magnetic field using MDI data. It is found, that the polar magnetic field reversal is detected with SOHO/MDI data for polar region within 78deg - 88deg. The North Pole has changed polarity in CR1975 (April 2001). The South reversed later in CR1980 (September 2001). The total unsigned magnetic flux does not show the dramatic decreasing during the polar reversals due to omnipresent bi-polar small-scale magnetic elements (Severnyi 1965, Lin et al. 1994, Benevolenskaya 2004). The observational and theoretical aspects of the polar magnetic field reversals are discussed. References Babcock, H. W., and Babcock, H. D. 1955, ApJ, 121, 349 Babcock, H. W., Livingston W. C., 1958, Science, 127, 1058 Babcock, H. D., 1959, ApJ, 130, 364 Benevolenskaya, E. E. 2004, Astron. Astrophys., 428, L5 Lin, H., Varsik, J., Zirin, H., 1994, Solar Phys., 155, 243 Severnyi A. B., 1965, Soviet Astron. Letters, 9, 171

  17. Magnetic field dosimeter development

    SciTech Connect

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

    1980-09-01

    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.

  18. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Chiba, Masashi

    The magnetic-field characteristics in spiral galaxies are investigated, with emphasis on the Milky Way. The dynamo theory is considered, and axisymmetric spiral (ASS) and bisymmetric spiral (BSS) magnetic fields are analyzed. Toroidal and poloidal magnetic fields are discussed.

  19. Particle optics of quadrupole doublet magnets in Spallation Neutron Source accumulator ring

    SciTech Connect

    Wang, Jian-Guang

    2006-12-01

    The SNS ring employs doublet quadrupoles and dipole-correctors in its straight sections. The electro-magnetic quadrupoles have a large aperture, small aspect ratio, and relatively short iron-to-iron distance. The corrector is even closer to one of the quads. There have been concerns on the magnetic fringe field and interference in the doublet magnets and their assemblies. We have performed 3D computing simulations to study magnetic field distributions in the doublet magnets. Further, we have analyzed the particle optics based on the z-dependent focusing functions of the quads. The effect of the magnetic fringe field and interference, including the third-order aberrations, on the particle motion are investigated. The lens parameters and the first-order hard edge models are derived and compared with the parameters used in the ring lattice calculations.

  20. Solar Wind Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Smith, E. J.

    1995-01-01

    The magnetic fields originate as coronal fields that are converted into space by the supersonic, infinitely conducting, solar wind. On average, the sun's rotation causes the field to wind up and form an Archimedes Spiral. However, the field direction changes almost continuously on a variety of scales and the irregular nature of these changes is often interpreted as evidence that the solar wind flow is turbulent.

  1. Electric and magnetic dipole couplings in split ring resonator metamaterials

    NASA Astrophysics Data System (ADS)

    Fan, Jing; Sun, Guang-Yong; Zhu, Wei-Ren

    2011-11-01

    In this paper, the electric and the magnetic dipole couplings between the outer and the inner rings of a single split ring resonator (SRR) are investigated. We numerically demonstrate that the magnetic resonance frequency can be substantially modified by changing the couplings of the electric and magnetic dipoles, and give a theoretical expression of the magnetic resonance frequency. The results in this work are expected to be conducive to a deeper understanding of the SRR and other similar metamaterials, and provide new guidance for complex metamaterials design with a tailored electromagnetic response.

  2. Hybrid permanent magnet gradient dipoles for the recycler ring at Fermilab

    SciTech Connect

    Brown, B.C.; Dimarco, J.; Foster, G.W.; Glass, H.D.; Haggard, J.E.; Harding, D.J.; Jackson, G.R.; May, M.R. Nicol, T.H.; Ostiguy, J.-F.; Schlabach, R.; Volk, J.T.

    1997-11-01

    Hybrid permanent magnets provide the magnetic fields for an anti- proton storage ring which is under construction at Fermilab. Using a combined function lattice, gradient magnets provide the bending, focusing and sextupole correction for the regular cells. Shorter magnets without sextupole are used in dispersion suppressor cells. These magnets use a 4.7 m ( 3 m) long iron shell for flux return, bricks of 25.4 mm thick strontium ferrite supply the flux and transversely tapered iron poles separated by aluminum spacers set the shape of the magnetic field. Central fields of 0.14 T with gradients of {approx}6%/inch ({approx}13%/inch) are required. Field errors are expected to be less than 10{sup -4} of the bend field over an aperture of {+-}40 mm (horizontal) {times} {+-}20 mm (vertical). Design, procurement, fabrication, pole potential adjustment, field shape trimming and measured fields will be reported.

  3. Analysis on the magnetic sensitivity in a total reflection prisms (TRP) ring resonator

    NASA Astrophysics Data System (ADS)

    Li, Dong; Zhao, Jianlin; Bi, Chao

    2015-07-01

    Based on the theory of transfer matrix and the condition of eigenmode self-reproduction, the model of the magnetic sensitivity in a total reflection prisms (TRP) ring laser resonator is established. Then the influences of the slight nonplanar effect on the output frequency difference and the magnetic sensitivity are analyzed theoretically and numerically. The results show that the slightly nonplanar effect will bring an additional ellipticity of the eigenmode and the environment magnetic field can produce an additional output frequency difference in a TRP ring laser resonator. It can also be found that the output frequency difference increases versus the augment of nonplanar angle and the intensity of magnetic field. These interesting results may be useful for designing and optimizing the structure of super high precision TRP ring laser gyroscopes.

  4. Magnetic Field Measurement System

    SciTech Connect

    Kulesza, Joe; Johnson, Eric; Lyndaker, Aaron; Deyhim, Alex; Waterman, Dave; Blomqvist, K. Ingvar; Dunn, Jonathan Hunter

    2007-01-19

    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.

  5. Analysis of ringing due to magnetic core materials used in pulsed nuclear magnetic resonance applications

    NASA Astrophysics Data System (ADS)

    Prabhu Gaunkar, Neelam; Nlebedim, Cajetan; Hadimani, Ravi; Bulu, Irfan; Song, Yi-Qiao; Mina, Mani; Jiles, David

    Oil-field well logging instruments employ pulsed nuclear magnetic resonance (NMR) techniques and use inductive sensors to detect and evaluate the presence of particular fluids in geological formations. Acting as both signal transmitters and receivers most inductive sensors employ magnetic cores to enhance the quality and amplitude of signals recorded during field measurements. It is observed that the magnetic core also responds to the applied input signal thereby generating a signal (`ringing') that interferes with the measurement of the signals from the target formations. This causes significant noise and receiver dead time and it is beneficial to eliminate/suppress the signals received from the magnetic core. In this work a detailed analysis of the magnetic core response and in particular loading of the sensor due to the presence of the magnetic core is presented. Pulsed NMR measurements over a frequency band of 100 kHz to 1MHz are used to determine the amplitude and linewidth of the signals acquired from different magnetic core materials. A lower signal amplitude and a higher linewidth are vital since these would correspond to minimal contributions from the magnetic core to the inductive sensor response and thus leading to minimized receiver dead time.

  6. DEGRADATION OF MAGNET EPOXY AT NSLS X-RAY RING.

    SciTech Connect

    HU,J.P.; ZHONG,Z.; HAAS,E.; HULBERT,S.; HUBBARD,R.

    2004-05-24

    Epoxy resin degradation was analyzed for NSLS X-ring magnets after two decades of 2.58-2.8 GeV continuous electron-beam operation, based on results obtained from thermoluminescent dosimeters irradiated along the NSLS ring and epoxy samples irradiated at the beamline target location. A Monte Carlo-based particle transport code, MCNP, was utilized to verify the dose from synchrotron radiation distributed along the axial- and transverse-direction in a ring model, which simulates the geometry of a ring quadrupole magnet and its central vacuum chamber downstream of the bending-magnet photon ports. The actual life expectancy of thoroughly vacuum baked-and-cured epoxy resin was estimated from radiation tests on similar polymeric materials using a radiation source developed for electrical insulation and mechanical structure studies.

  7. Particle optics of quadrupole doublet magnets in Spallation Neutron Source accumulator ring

    NASA Astrophysics Data System (ADS)

    Wang, J. G.

    2006-12-01

    The Spallation Neutron Source ring employs doublet quadrupoles and dipole correctors in its straight sections. The electromagnetic quadrupoles have a large aperture, small aspect ratio, and relatively short iron-to-iron distance. The corrector is even closer to one of the quads. There have been concerns on the magnetic fringe field and interference in the doublet magnets and their assemblies. We have performed 3D computing simulations to study magnetic field distributions in the doublet magnets. Further, we have analyzed the particle optics based on the z-dependent focusing functions of the quads. The effect of the magnetic fringe field and interference, including the third-order aberrations, on the particle motion are investigated. The lens parameters and the first-order hard edge models are derived and compared with the parameters used in the ring lattice calculations.

  8. Mercury's Magnetic Field

    NASA Astrophysics Data System (ADS)

    Johnson, C. L.

    2014-12-01

    Mercury is the only inner solar system body other than Earth to possess an active core dynamo-driven magnetic field and the only planet with a small, highly dynamic magnetosphere. Measurements made by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft have provided a wealth of data on Mercury's magnetic field environment. Mercury's weak magnetic field was discovered 40 years ago by the Mariner 10 spacecraft, but its large-scale geometry, strength and origin could not be definitively established. MESSENGER data have shown that the field is dynamo-generated and can be described as an offset axisymmetric dipole field (hereafter OAD): the magnetic equator lies ~0.2 RM (RM = 2440 km) north of the geographic equator and the dipole moment is 2.8 x1019 Am2 (~0.03% that of Earth's). The weak internal field and the high, but variable, solar wind ram pressure drive vigorous magnetospheric dynamics and result in an average distance from the planet center to the sub-solar magnetopause of only 1.42 RM. Magnetospheric models developed with MESSENGER data have allowed re-analysis of the Mariner 10 observations, establishing that there has been no measureable secular variation in the internal field over 40 years. Together with spatial power spectra for the OAD, this provides critical constraints for viable dynamo models. Time-varying magnetopause fields induce secondary core fields, the magnitudes of which confirm the core radius estimated from MESSENGER gravity and Earth-based radar data. After accounting for large-scale magnetospheric fields, residual signatures are dominated by additional external fields that are organized in the local time frame and that vary with magnetospheric activity. Birkeland currents have been identified, which likely close in the planetary interior at depths below the base of the crust. Near-periapsis magnetic field measurements at altitudes greater than 200 km have tantalizing hints of crustal fields, but crustal sources cannot be distinguished from core fields, nor cleanly separated from external fields. I will report on recent data acquired at altitudes as low as 25 km that have the potential to resolve these issues. The presence of remanent crustal fields would have profound implications for Mercury's thermal and dynamical histories.

  9. Magnetic field of the Earth

    NASA Astrophysics Data System (ADS)

    Popov, Aleksey

    2013-04-01

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

  10. Eruptive solar magnetic fields

    NASA Technical Reports Server (NTRS)

    Low, B. C.

    1981-01-01

    The quasi-steady evolution of solar magnetic fields in response to gradual photospheric changes is considered, with particular attention given to the threshold of a sudden eruption in the solar atmosphere. The formal model of an evolving, force-free field dependent on two Cartesian coordinates is extended to a field which is not force free but in static equilibrium with plasma pressure and gravity. The basic physics is illustrated through the evolution of a loop-shaped electric current sheet enclosing a potential bipolar field with footpoints rooted in the photosphere. A free-boundary problem is posed and then solved for the equilibrium configuration of the current sheet in a hydrostatically supported isothermal atmosphere. As the footpoints move apart to spread a constant photospheric magnetic flux over a larger region, the equilibria available extend the field to increasing heights.

  11. Conventional magnet storage rings for x-ray lithography

    SciTech Connect

    Bassetti, M.; Batchelor, K.; Galayda, J.; Halama, H.; Heese, R.; Hsieh, H.; Krinsky, S.; Murphy, J.; van Steenbergen, A.; Vignola, G.

    1986-10-01

    A first pass at the design of a conventional magnet storage ring for x-ray lithogrphy is presented. Electron beam size and power specifications are given, followed by a first pass at a lattice - a 4-fold symmetric, gradient FODO cell lattice using B = 1.6 Tesla C-magnets. (LEW)

  12. Magnetic Fields in Galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    The origin and evolution of cosmic magnetic fields, their strength and structure in intergalactic space, their first occurrence in young galaxies, and their dynamical importance for galaxy evolution remain widely unknown. Radio synchrotron emission, its polarization and its Faraday rotation are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized radio synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 μG) and in central starburst regions (50-100 μG). Such fields are dynamically important; they can affect gas flows and drive gas inflows in central regions. Polarized radio emission traces ordered fields which can be regular or anisotropic turbulent, generated from isotropic turbulent fields by compression or shear. The strongest ordered fields of 10-15 μG strength are generally found in interarm regions and follow the orientation of adjacent gas spiral arms. In galaxies with strong density waves, ordered (anisotropic turbulent) fields are also observed at the inner edges of the spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies, and in central regions of starburst galaxies. Ordered fields in interacting galaxies have asymmetric distributions and are an excellent tracer of past interactions between galaxies or with the intergalactic medium. Irregular galaxies host isotropic turbulent fields often of similar strength as in spiral galaxies, but only weak ordered fields. Faraday rotation measures (RM) of the diffuse polarized radio emission from the disks of several galaxies reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by a mean-field α -Ω dynamo. So far no indications were found in external galaxies of large-scale field reversals, like the one in the Milky Way. Ordered magnetic fields are also observed in radio halos around edge-on galaxies out to large distances from the plane, with X-shaped patterns. In the outflow cone above a starburst region of NGC 253, RM data indicate a helical magnetic field.

  13. High temperature spin dynamics in linear magnetic chains, molecular rings, and segments by nuclear magnetic resonance

    SciTech Connect

    Adelnia, Fatemeh; Lascialfari, Alessandro; Mariani, Manuel; Ammannato, Luca; Caneschi, Andrea; Rovai, Donella; Winpenny, Richard; Timco, Grigore; Corti, Maurizio Borsa, Ferdinando

    2015-05-07

    We present the room temperature proton nuclear magnetic resonance (NMR) nuclear spin-lattice relaxation rate (NSLR) results in two 1D spin chains: the Heisenberg antiferromagnetic (AFM) Eu(hfac){sub 3}NITEt and the magnetically frustrated Gd(hfac){sub 3}NITEt. The NSLR as a function of external magnetic field can be interpreted very well in terms of high temperature spin dynamics dominated by a long time persistence of the decay of the two-spin correlation function due to the conservation of the total spin value for isotropic Heisenberg chains. The high temperature spin dynamics are also investigated in Heisenberg AFM molecular rings. In both Cr{sub 8} closed ring and in Cr{sub 7}Cd and Cr{sub 8}Zn open rings, i.e., model systems for a finite spin segment, an enhancement of the low frequency spectral density is found consistent with spin diffusion but the high cut-off frequency due to intermolecular anisotropic interactions prevents a detailed analysis of the spin diffusion regime.

  14. Ultrafast precessional magnetization reversal by picosecond magnetic field pulse shaping.

    PubMed

    Gerrits, Th; Van Den Berg, H A M; Hohlfeld, J; Bär, L; Rasing, Th

    2002-08-01

    Since the invention of the first magnetic memory disk in 1954, much effort has been put into enhancing the speed, bit density and reliability of magnetic memory devices. In the case of magnetic random access memory (MRAM) devices, fast coherent magnetization rotation by precession of the entire memory cell is desired, because reversal by domain-wall motion is much too slow. In principle, the fundamental limit of the switching speed via precession is given by half of the precession period. However, under-critically damped systems exhibit severe ringing and simulations show that, as a consequence, undesired back-switching of magnetic elements of an MRAM can easily be initiated by subsequent write pulses, threatening data integrity. We present a method to reverse the magnetization in under-critically damped systems by coherent rotation of the magnetization while avoiding any ringing. This is achieved by applying specifically shaped magnetic field pulses that match the intrinsic properties of the magnetic elements. We demonstrate, by probing all three magnetization components, that reliable precessional reversal in lithographically structured micrometre-sized elliptical permalloy elements is possible at switching times of about 200 ps, which is ten times faster than the natural damping time constant. PMID:12152072

  15. High field superconducting magnets

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  16. Correlation of lunar far-side magnetized regions with ringed impact basins

    USGS Publications Warehouse

    Anderson, K.A.; Wilhelms, D.E.

    1979-01-01

    By the method of electron reflection, we have identified seven well-defined magnetized regions in the equatorial belt of the lunar far side sampled by the Apollo 16 Particles and Fields subsatellite. Most of these surface magnetic fields lie within one basin radius from the rim of a ringed impact basin, where thick deposits of basin ejecta are observed or inferred. The strongest of the seven magnetic features is linear, at least 250 km long, and radial to the Freundlich-Sharonov basin. The apparent correlation with basin ejecta suggests some form of impact origin for the observed permanently magnetized regions. ?? 1979.

  17. The Heliospheric Magnetic Field

    NASA Astrophysics Data System (ADS)

    Balogh, André; Erdõs, Géza

    2013-06-01

    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.

  18. Magnet design for an ultralow emittance storage ring

    NASA Astrophysics Data System (ADS)

    Saeidi, F.; Razazian, M.; Rahighi, J.; Pourimani, R.

    2016-03-01

    The Iranian Light Source Facility (ILSF) is a new 3 GeV synchrotron radiation laboratory which is in the design stage. The ILSF storage ring (SR) is based on a Five-Bend Achromat (5BA) lattice providing an ultra-low beam emittance of 0.48 nm rad. The ring is comprised of 100 pure dipole magnets, 320 quadrupoles, and 320 sextupoles with additional coils for dipole and skew quadrupole correctors. In this paper, we present some design features of the SR magnets and discuss the detailed physical design of these electromagnets. The related electrical and cooling calculations and mechanical design issues have been investigated as well.

  19. Magnetization dynamics using ultrashort magnetic field pulses

    NASA Astrophysics Data System (ADS)

    Tudosa, Ioan

    Very short and well shaped magnetic field pulses can be generated using ultra-relativistic electron bunches at Stanford Linear Accelerator. These fields of several Tesla with duration of several picoseconds are used to study the response of magnetic materials to a very short excitation. Precession of a magnetic moment by 90 degrees in a field of 1 Tesla takes about 10 picoseconds, so we explore the range of fast switching of the magnetization by precession. Our experiments are in a region of magnetic excitation that is not yet accessible by other methods. The current table top experiments can generate fields longer than 100 ps and with strength of 0.1 Tesla only. Two types of magnetic were used, magnetic recording media and model magnetic thin films. Information about the magnetization dynamics is extracted from the magnetic patterns generated by the magnetic field. The shape and size of these patterns are influenced by the dissipation of angular momentum involved in the switching process. The high-density recording media, both in-plane and perpendicular type, shows a pattern which indicates a high spin momentum dissipation. The perpendicular magnetic recording media was exposed to multiple magnetic field pulses. We observed an extended transition region between switched and non-switched areas indicating a stochastic switching behavior that cannot be explained by thermal fluctuations. The model films consist of very thin crystalline Fe films on GaAs. Even with these model films we see an enhanced dissipation compared to ferromagnetic resonance studies. The magnetic patterns show that damping increases with time and it is not a constant as usually assumed in the equation describing the magnetization dynamics. The simulation using the theory of spin-wave scattering explains only half of the observed damping. An important feature of this theory is that the spin dissipation is time dependent and depends on the large angle between the magnetization and the magnetic field.

  20. Effects of Magnetic Flux Circulation on Radiation Belt and Ring Current Populations

    NASA Astrophysics Data System (ADS)

    Mitchell, E. J.; Fok, M. H.

    2011-12-01

    The orientation of the interplanetary magnetic field (IMF) determines the location of the dayside merging line and the magnetic flux circulation patterns. Magnetic flux circulation determines the amount of energy which enters the magnetosphere and ionosphere. We use the Lyon-Fedder-Mobarry (LFM) global Magneto-Hydro-Dynamic (MHD) code to simulate both idealized and real solar wind cases. We use several satellites to validate the LFM simulation results for the real solar wind case studies. With these cases, we examine the magnetic flux circulation under differing IMF orientations. We also use the Comprehensive Ring Current Model (CRCM) and Radiation Belt Environment (RBE) model to examine the inner magnetospheric response to the orientation of the IMF. We will present the different magnetic flux circulation patterns and the resulting effects on the radiation belt and ring current population.

  1. A pump with flat-ring-shaped magnets

    NASA Astrophysics Data System (ADS)

    Saotome, H.; Hagiwara, T.; Sato, Y.

    1998-06-01

    Previously, authors developed a novel linear actuator with flat-ring-shaped magnets and applied it to a pump. In this article, the output power of the actuator and the efficiency of the pump are obtained by experiments. A pair of flat-ring-shaped Nd-Fe-B magnets having N and S poles on the surface are put on the same axis and face each other. Rotating one of the ring magnets in the direction of its circumference, an oscillating force occurs on the other magnet. When this magnet is restricted to linear motion along the axis, the mechanical power driving the rotating magnet is transferred to the linear motion power. A pump was made with this mechanism. The efficiency of the pump is experimentally obtained, where water pressure difference between the intake and the outlet has been changed. As a result, the efficiency of the pump attains to about 45%. The efficiency of the actuator itself is very high, because the actuator has no copper and iron losses, and a negligibly small eddy current loss.

  2. THE GALACTIC MAGNETIC FIELD

    SciTech Connect

    Jansson, Ronnie; Farrar, Glennys R.

    2012-12-10

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

  3. Radial magnetic field in magnetic confinement device

    NASA Astrophysics Data System (ADS)

    Xiong, Hao; Liu, Ming-Hai; Chen, Ming; Rao, Bo; Chen, Jie; Chen, Zhao-Quan; Xiao, Jin-Shui; Hu, Xi-Wei

    2015-09-01

    The intrinsic radial magnetic field (Br) in a tokamak is explored by the solution of the Grad-Shafranov equation in axisymmetric configurations through an expansion of the four terms of the magnetic surfaces. It can be inferred from the simulation results that at the core of the device, the tokamak should possess a three-dimensional magnetic field configuration, which could be reduced to a two-dimensional one when the radial position is greater than 0.6a. The radial magnetic field and the amzimuthal magnetic field have the same order of magnitude at the core of the device. These results can offer a reference for the analysis of the plasma instability, the property of the core plasma, and the magnetic field measurement. Project supported by the Special Domestic Program of ITER, China (Grant No. 2009GB105003).

  4. Superhorizon magnetic fields

    NASA Astrophysics Data System (ADS)

    Campanelli, Leonardo

    2016-03-01

    We analyze the evolution of superhorizon-scale magnetic fields from the end of inflation till today. Whatever is the mechanism responsible for their generation during inflation, we find that a given magnetic mode with wave number k evolves, after inflation, according to the values of k ηe , nk , and Ωk , where ηe is the conformal time at the end of inflation, nk is the number density spectrum of inflation-produced photons, and Ωk is the phase difference between the two Bogoliubov coefficients which characterize the state of that mode at the end of inflation. For any realistic inflationary magnetogenesis scenario, we find that nk-1≪|k ηe|≪1 , and three evolutionary scenarios are possible: (i) |Ωk∓π |=O (1 ) , in which case the evolution of the magnetic spectrum Bk(η ) is adiabatic, a2Bk(η )=const , with a being the expansion parameter; (ii) |Ωk∓π |≪|k ηe| , in which case the evolution is superadiabatic, a2Bk(η )∝η ; (iii) |k ηe|≪|Ωk∓π |≪1 or |k ηe|˜|Ωk∓π |≪1 , in which case an early phase of adiabatic evolution is followed, after a time η⋆˜|Ωk∓π |/k , by a superadiabatic evolution. Once a given mode reenters the horizon, it remains frozen into the plasma and then evolves adiabatically till today. As a corollary of our results, we find that inflation-generated magnetic fields evolve adiabatically on all scales and for all times in conformal-invariant free Maxwell theory, while they evolve superadiabatically after inflation on superhorizon scales in the nonconformal-invariant Ratra model, where the inflaton is kinematically coupled to the electromagnetic field. The latter result supports and, somehow, clarifies our recent claim that the Ratra model can account for the presence of cosmic magnetic fields without suffering from both backreaction and strong-coupling problems.

  5. Electric and magnetic fields

    NASA Technical Reports Server (NTRS)

    Kaufman, H. R.; Robinson, R. S.; Etters, R. D.

    1982-01-01

    A number of energy momentum anomalies are described that result from the use of Abraham-Lorentz electromagnetic theory. These anomalies have in common the motion of charged bodies or current carrying conductors relative to the observer. The anomalies can be avoided by using the nonflow approach, based on internal energy of the electromagnetic field. The anomalies can also be avoided by using the flow approach, if all contributions to flow work are included. The general objective of this research is a fundamental physical understanding of electric and magnetic fields which, in turn, might promote the development of new concepts in electric space propulsion. The approach taken is to investigate quantum representations of these fields.

  6. Low field magnetic resonance imaging

    DOEpatents

    Pines, Alexander; Sakellariou, Dimitrios; Meriles, Carlos A.; Trabesinger, Andreas H.

    2010-07-13

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

  7. Analysis of ringing effects due to magnetic core materials in pulsed nuclear magnetic resonance circuits

    NASA Astrophysics Data System (ADS)

    Prabhu Gaunkar, N.; Bouda, N. R. Y.; Nlebedim, I. C.; Hadimani, R. L.; Bulu, I.; Ganesan, K.; Song, Y. Q.; Mina, M.; Jiles, D. C.

    2015-05-01

    This work presents investigations and detailed analysis of ringing in a non-resonant pulsed nuclear magnetic resonance (NMR) circuit. Ringing is a commonly observed phenomenon in high power switching circuits. The oscillations described as ringing impede measurements in pulsed NMR systems. It is therefore desirable that those oscillations decay fast. It is often assumed that one of the causes behind ringing is the role of the magnetic core used in the antenna (acting as an inductive load). We will demonstrate that an LRC subcircuit is also set-up due to the inductive load and needs to be considered due to its parasitic effects. It is observed that the parasitics associated with the inductive load become important at certain frequencies. The output response can be related to the response of an under-damped circuit and to the magnetic core material. This research work demonstrates and discusses ways of controlling ringing by considering interrelationships between different contributing factors.

  8. Analysis of ringing effects due to magnetic core materials in pulsed nuclear magnetic resonance circuits

    SciTech Connect

    Prabhu Gaunkar, N. Bouda, N. R. Y.; Nlebedim, I. C.; Hadimani, R. L.; Mina, M.; Jiles, D. C.; Bulu, I.; Ganesan, K.; Song, Y. Q.

    2015-05-07

    This work presents investigations and detailed analysis of ringing in a non-resonant pulsed nuclear magnetic resonance (NMR) circuit. Ringing is a commonly observed phenomenon in high power switching circuits. The oscillations described as ringing impede measurements in pulsed NMR systems. It is therefore desirable that those oscillations decay fast. It is often assumed that one of the causes behind ringing is the role of the magnetic core used in the antenna (acting as an inductive load). We will demonstrate that an LRC subcircuit is also set-up due to the inductive load and needs to be considered due to its parasitic effects. It is observed that the parasitics associated with the inductive load become important at certain frequencies. The output response can be related to the response of an under-damped circuit and to the magnetic core material. This research work demonstrates and discusses ways of controlling ringing by considering interrelationships between different contributing factors.

  9. An evaluation of Tsyganenko magnetic field model

    SciTech Connect

    Fairfield, D.H. )

    1991-02-01

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

  10. Polar Magnetic Field Experiment

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1999-01-01

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

  11. Photonic Magnetic Field Sensor

    NASA Astrophysics Data System (ADS)

    Wyntjes, Geert

    2002-02-01

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

  12. Comparisons of Simulated and Observed Stormtime Magnetic Intensities and Ion Densities in the Ring Current

    NASA Astrophysics Data System (ADS)

    Chen, M. W.; Guild, T. B.; Lemon, C. L.; Schulz, M.

    2008-12-01

    Recent progress in ring current and plasma sheet modeling has shown the importance of a self-consistent treatment of particle transport and magnetic and electric fields in the inner magnetosphere. For example, the feedback of the ring current tends to mitigate the build-up of the asymmetric ring current and associated magnetic depressions during storm main phase. Models with and without self-consistency can lead to significantly different magnitudes and spatial distributions of plasma pressure and magnetic intensity during disturbed times. In this study we compare simulated and observed stormtime magnetic intensities and ion densities at geosynchronous altitude to test how well self-consistent simulations can simultaneously reproduce these quantities. We simulate the ring current and plasma sheet for conditions corresponding to the 12-14 August 2000 storm using the self-consistent Rice Convection Model-Equilibrium (RCM-E) [ Lemon et al., JGR, 2004]. Using the empirical IMF-dependent model of Tsyganenko and Mukai [JGR, 2003], we specify the plasma sheet pressure and density at 10 RE as the plasma boundary location in the RCM- E. We compare the simulated magnetic intensity at geosynchronous altitude (6.6 RE) with the magnetic intensity measured by magnetometers on the GOES G8, G10, and G11 satellites. The simulated ion densities at different magnetic local times are compared with those from the re-analysis model of LANL/MPA densities of O'Brien and Lemon [Space Weather, 2007]. This is a first step towards a more extensive comparison that will include other datasets, such as ion and magnetic field data from Polar, at locations closer to the Earth than geosynchronous altitude.

  13. Magnetic Fields: Visible and Permanent.

    ERIC Educational Resources Information Center

    Winkeljohn, Dorothy R.; Earl, Robert D.

    1983-01-01

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

  14. Formation and dynamics of a rotating proton ring in a magnetic mirror

    NASA Astrophysics Data System (ADS)

    Dreike, P. L.; Greenly, John B.; Hammer, D. A.; Sudan, R. N.

    1982-01-01

    Experimental results are presented on the formation and dynamics of a rotating energetic proton ring in a magnetic mirror field. An annular 430 keV proton beam from a magnetically insulated diode is injected through a cusp-like magnetic field to form a rotating proton beam in a 2 m long solenoidal magnetic field. With 15-400 mT of neutral gas in the 40 cm diam experimental chamber up to 83% of the 350 J total beam energy is in rotation, the axial velocity dispersion is small, and the beam is sharply defined radially with inner and outer radii of 7 and 13 cm, respectively. The beam is 90%-100% axially current neutralized by currents induced in the beam-generated plasma. Azimuthal plasma currents are observed in air, but not in hydrogen. In hydrogen a ring containing 5×1015 protons is formed with sufficiently small axial velocity dispersion so that the protons are confined axially by their own 3% diamagnetic well as they propagate about 1.3 m in an 8 kG solenoidal field. In air, up to 15% of the beam axial energy is inductively coupled to the induced plasma currents, and ≳50% reflections are achieved from a 1.23 mirror ratio magnetic mirror located 2 m from the ion injector. About 1% inductive energy coupling to a wall resistor array was observed in both air and hydrogen. A peak ring diamagnetism of 875 G was observed 50 cm from the injector at a point where the applied field was 11 kG (near the peak of an upstream mirror); this ring contained about 1×1016 protons.

  15. Reconnection of Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Birn, J.; Priest, E. R.

    2007-01-01

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

  16. Leptogenesis and primordial magnetic fields

    SciTech Connect

    Long, Andrew J.; Sabancilar, Eray; Vachaspati, Tanmay E-mail: eray.sabancilar@asu.edu

    2014-02-01

    The anomalous conversion of leptons into baryons during leptogenesis is shown to produce a right-handed helical magnetic field; in contrast, the magnetic field produced during electroweak baryogenesis is known to be left-handed. If the cosmological medium is turbulent, the magnetic field evolves to have a present day coherence scale ∼ 10 pc and field strength ∼ 10{sup −18} Gauss. This result is insensitive to the energy scale at which leptogenesis took place. Observations of the amplitude, coherence scale, and helicity of the intergalactic magnetic field promise to provide a powerful probe of physics beyond the Standard Model and the very early universe.

  17. Observations of galactic magnetic fields

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    Magnetic fields are enchored in gas clouds. Field lines are tangled in spiral arms, but highly regular between the arms. The similarity of pitch angles between gaseous and magnetic arms suggests a coupling between the density wave and the magnetic wave. Observations of large-scale patterns in Faraday rotation favour a dynamo origin of the regular fields. Fields in barred galaxies do not reveal the strong shearing shocks observed in the cold gas, but swing smoothly from the upstream region into the bar. Magnetic fields are important for the dynamcis of gas clouds, for the formation of spiral structures, bars and halos, and for mass and angular momentum transport in central regions.

  18. Fast superconducting magnetic field switch

    DOEpatents

    Goren, Yehuda; Mahale, Narayan K.

    1996-01-01

    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.

  19. Fast superconducting magnetic field switch

    DOEpatents

    Goren, Y.; Mahale, N.K.

    1996-08-06

    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.

  20. Martian external magnetic field proxies

    NASA Astrophysics Data System (ADS)

    Langlais, Benoit; Civet, Francois

    2015-04-01

    Mars possesses no dynamic magnetic field of internal origin as it is the case for the Earth or for Mercury. Instead Mars is characterized by an intense and localized magnetic field of crustal origin. This field is the result of past magnetization and demagnetization processes, and reflects its evolution. The Interplanetary Magnetic Field (IMF) interacts with Mars' ionized environment to create an external magnetic field. This external field is weak compared to lithospheric one but very dynamic, and may hamper the detailed analysis of the internal magnetic field at some places or times. Because there are currently no magnetic field measurements made at Mars' surface, it is not possible to directly monitor the external field temporal variability as it is done in Earth's ground magnetic observatories. In this study we examine to indirect ways of quantifying this external field. First we use the Advanced Composition Explorer (ACE) mission which measures the solar wind about one hour upstream of the bow-shock resulting from the interaction between the solar wind and the Earth's internal magnetic field. These measurements are extrapolated to Mars' position taking into account the orbital configurations of the Mars-Earth system and the velocity of particles carrying the IMF. Second we directly use Mars Global Surveyor magnetic field measurements to quantify the level of variability of the external field. We subtract from the measurements the internal field which is otherwise modeled, and bin the residuals first on a spatial and then on a temporal mesh. This allows to compute daily or semi daily index. We present a comparison of these two proxies and demonstrate their complementarity. We also illustrate our analysis by comparing our Martian external field proxies to terrestrial index at epochs of known strong activity. These proxies will especially be useful for upcoming magnetic field measurements made around or at the surface of Mars.

  1. Electric and Magnetic Dipole Coupling in Near-Infrared Split-Ring Metamaterial Arrays

    NASA Astrophysics Data System (ADS)

    Sersic, Ivana; Frimmer, Martin; Verhagen, Ewold; Koenderink, A. Femius

    2009-11-01

    We present experimental observations of strong electric and magnetic interactions between split ring resonators (SRRs) in metamaterials. We fabricated near-infrared planar metamaterials with different inter-SRR spacings along different directions. Our transmission measurements show blueshifts and redshifts of the magnetic resonance, depending on SRR orientation relative to the lattice. The shifts agree well with simultaneous magnetic and electric near-field dipole coupling. We also find large broadening of the resonance, accompanied by a decrease in effective cross section per SRR with increasing density due to superradiant scattering. Our data shed new light on Lorentz-Lorenz approaches to metamaterials.

  2. Electric and magnetic dipole coupling in near-infrared split-ring metamaterial arrays.

    PubMed

    Sersic, Ivana; Frimmer, Martin; Verhagen, Ewold; Koenderink, A Femius

    2009-11-20

    We present experimental observations of strong electric and magnetic interactions between split ring resonators (SRRs) in metamaterials. We fabricated near-infrared planar metamaterials with different inter-SRR spacings along different directions. Our transmission measurements show blueshifts and redshifts of the magnetic resonance, depending on SRR orientation relative to the lattice. The shifts agree well with simultaneous magnetic and electric near-field dipole coupling. We also find large broadening of the resonance, accompanied by a decrease in effective cross section per SRR with increasing density due to superradiant scattering. Our data shed new light on Lorentz-Lorenz approaches to metamaterials. PMID:20366039

  3. Evolution of twisted magnetic fields

    SciTech Connect

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

    1985-02-01

    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.

  4. PERMANENT MAGNET DESIGNS WITH LARGE VARIATIONS IN FIELD STRENGTH.

    SciTech Connect

    GUPTA,R.

    2004-01-21

    The use of permanent magnets has been investigated as an option for electron cooling ring for the proposed luminosity upgrade of RHIC. Several methods have been developed that allow a large variation in field strength. These design concepts were verified with computer simulations using finite element codes. It will be shown that the field uniformity is maintained while the field strength is mechanically adjusted.

  5. Exposure guidelines for magnetic fields

    SciTech Connect

    Miller, G.

    1987-12-01

    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.

  6. Magnetic field modification of optical magnetic dipoles.

    PubMed

    Armelles, Gaspar; Caballero, Blanca; Cebollada, Alfonso; Garcia-Martin, Antonio; Meneses-Rodríguez, David

    2015-03-11

    Acting on optical magnetic dipoles opens novel routes to govern light-matter interaction. We demonstrate magnetic field modification of the magnetic dipolar moment characteristic of resonant nanoholes in thin magnetoplasmonic films. This is experimentally shown through the demonstration of the magneto-optical analogue of Babinet's principle, where mirror imaged MO spectral dependencies are obtained for two complementary magnetoplasmonic systems: holes in a perforated metallic layer and a layer of disks on a substrate. PMID:25646869

  7. Magnetic-field-dosimetry system

    DOEpatents

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

    1981-01-21

    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.

  8. Radiation effects in a muon collider ring and dipole magnet protection

    SciTech Connect

    Mokhov, N.V.; Kashikhin, V.V.; Novitski, I.; Zlobin, A.V.; /Fermilab

    2011-03-01

    The requirements and operating conditions for a Muon Collider Storage Ring (MCSR) pose significant challenges to superconducting magnets. The dipole magnets should provide a high magnetic field to reduce the ring circumference and thus maximize the number of muon collisions during their lifetime. One third of the beam energy is continuously deposited along the lattice by the decay electrons at the rate of 0.5 kW/m for a 1.5-TeV c.o.m. and a luminosity of 10{sup 34} cm{sup -2}s{sup -1}. Unlike dipoles in proton machines, the MCSR dipoles should allow this dynamic heat load to escape the magnet helium volume in the horizontal plane, predominantly towards the ring center. This paper presents the analysis and comparison of radiation effects in MCSR based on two dipole magnets designs. Tungsten masks in the interconnect regions are used in both cases to mitigate the unprecedented dynamic heat deposition and radiation in the magnet coils.

  9. Rotating effects on an atom with a magnetic quadrupole moment confined to a quantum ring

    NASA Astrophysics Data System (ADS)

    Fonseca, I. C.; Bakke, Knut

    2016-03-01

    We investigate rotating effects on an atom with a magnetic quadrupole moment that interacts with a radial electric field in a two-dimensional quantum ring through a single-particle approximation (V.F. Dmitriev et al., Phys. Rev. C 50, 2358 (1994)). We show that a Coulomb-type and a linear-type scalar potentials stem from the interaction between magnetic quadrupole moment and a radial electric field under rotating effects. Besides, we discuss the dependence of the angular frequency on the angular velocity of the rotating frame and the quantum numbers of the system.

  10. The Sun's global magnetic field.

    PubMed

    Mackay, Duncan H

    2012-07-13

    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

  11. Vestibular stimulation by magnetic fields.

    PubMed

    Ward, Bryan K; Roberts, Dale C; Della Santina, Charles C; Carey, John P; Zee, David S

    2015-04-01

    Individuals working next to strong static magnetic fields occasionally report disorientation and vertigo. With the increasing strength of magnetic fields used for magnetic resonance imaging studies, these reports have become more common. It was recently learned that humans, mice, and zebrafish all demonstrate behaviors consistent with constant peripheral vestibular stimulation while inside a strong, static magnetic field. The proposed mechanism for this effect involves a Lorentz force resulting from the interaction of a strong static magnetic field with naturally occurring ionic currents flowing through the inner ear endolymph into vestibular hair cells. The resulting force within the endolymph is strong enough to displace the lateral semicircular canal cupula, inducing vertigo and the horizontal nystagmus seen in normal mice and in humans. This review explores the evidence for interactions of magnetic fields with the vestibular system. PMID:25735662

  12. Vestibular stimulation by magnetic fields

    PubMed Central

    Ward, Bryan K.; Roberts, Dale C.; Della Santina, Charles C.; Carey, John P.; Zee, David S.

    2015-01-01

    Individuals working next to strong static magnetic fields occasionally report disorientation and vertigo. With the increasing strength of magnetic fields used for magnetic resonance imaging (MRI) studies, these reports have become more common. It was recently learned that humans, mice and zebrafish all demonstrate behaviors consistent with constant peripheral vestibular stimulation while inside a strong, static magnetic field. The proposed mechanism for this effect involves a Lorentz force resulting from the interaction of a strong static magnetic field with naturally occurring ionic currents flowing through the inner ear endolymph into vestibular hair cells. The resulting force within the endolymph is strong enough to displace the lateral semicircular canal cupula, inducing vertigo and the horizontal nystagmus seen in normal mice and in humans. This review explores the evidence for interactions of magnetic fields with the vestibular system. PMID:25735662

  13. Practical method using superposition of individual magnetic fields for initial arrangement of undulator magnets

    NASA Astrophysics Data System (ADS)

    Tsuchiya, K.; Shioya, T.

    2015-04-01

    We have developed a practical method for determining an excellent initial arrangement of magnetic arrays for a pure-magnet Halbach-type undulator. In this method, the longitudinal magnetic field distribution of each magnet is measured using a moving Hall probe system along the beam axis with a high positional resolution. The initial arrangement of magnetic arrays is optimized and selected by analyzing the superposition of all distribution data in order to achieve adequate spectral quality for the undulator. We applied this method to two elliptically polarizing undulators (EPUs), called U#16-2 and U#02-2, at the Photon Factory storage ring (PF ring) in the High Energy Accelerator Research Organization (KEK). The measured field distribution of the undulator was demonstrated to be excellent for the initial arrangement of the magnet array, and this method saved a great deal of effort in adjusting the magnetic fields of EPUs.

  14. Practical method using superposition of individual magnetic fields for initial arrangement of undulator magnets

    SciTech Connect

    Tsuchiya, K.; Shioya, T.

    2015-04-15

    We have developed a practical method for determining an excellent initial arrangement of magnetic arrays for a pure-magnet Halbach-type undulator. In this method, the longitudinal magnetic field distribution of each magnet is measured using a moving Hall probe system along the beam axis with a high positional resolution. The initial arrangement of magnetic arrays is optimized and selected by analyzing the superposition of all distribution data in order to achieve adequate spectral quality for the undulator. We applied this method to two elliptically polarizing undulators (EPUs), called U#16-2 and U#02-2, at the Photon Factory storage ring (PF ring) in the High Energy Accelerator Research Organization (KEK). The measured field distribution of the undulator was demonstrated to be excellent for the initial arrangement of the magnet array, and this method saved a great deal of effort in adjusting the magnetic fields of EPUs.

  15. Magnetic fields around evolved stars

    NASA Astrophysics Data System (ADS)

    Leal-Ferreira, M.; Vlemmings, W.; Kemball, A.; Amiri, N.; Maercker, M.; Ramstedt, S.; Olofsson, G.

    2014-04-01

    A number of mechanisms, such as magnetic fields, (binary) companions and circumstellar disks have been suggested to be the cause of non-spherical PNe and in particular collimated outflows. This work investigates one of these mechanisms: the magnetic fields. While MHD simulations show that the fields can indeed be important, few observations of magnetic fields have been done so far. We used the VLBA to observe five evolved stars, with the goal of detecting the magnetic field by means of water maser polarization. The sample consists in four AGB stars (IK Tau, RT Vir, IRC+60370 and AP Lyn) and one pPN (OH231.8+4.2). In four of the five sources, several strong maser features were detected allowing us to measure the linear and/or circular polarization. Based on the circular polarization detections, we infer the strength of the component of the field along the line of sight to be between ~30 mG and ~330 mG in the water maser regions of these four sources. When extrapolated to the surface of the stars, the magnetic field strength would be between a few hundred mG and a few Gauss when assuming a toroidal field geometry and higher when assuming more complex magnetic fields. We conclude that the magnetic energy we derived in the water maser regions is higher than the thermal and kinetic energy, leading to the conclusion that, indeed, magnetic fields probably play an important role in shaping Planetary Nebulae.

  16. Neutron interference in the gravitational field of a ring laser

    NASA Astrophysics Data System (ADS)

    Fischetti, Robert D.; Mallett, Ronald L.

    2015-07-01

    The neutron split-beam interferometer has proven to be particularly useful in measuring Newtonian gravitational effects such as those studied by Colella, Overhauser, and Werner (COW). The development of the ring laser has led to numerous applications in many areas of physics including a recent general relativistic prediction of frame dragging in the gravitational field produced by the electromagnetic radiation in a ring laser. This paper introduces a new general technique based on a canonical transformation of the Dirac equation for the gravitational field of a general linearized spacetime. Using this technique it is shown that there is a phase shift in the interference of two neutron beams due to the frame-dragging nature of the gravitational field of a ring laser.

  17. Piston ring microwelding: Field/lab correlation and prevention

    SciTech Connect

    Shuster, M.; Mahler, F.; Deis, M.; Macy, D.; Frame, R.

    1996-12-31

    This paper will discuss the microwelding phenomenon between aluminum pistons and iron piston rings in internal combustion engines. The mechanism of microwelding as observed on field run engine hardware has been correlated with the microwelding mechanism generated in an accelerated laboratory bench test. Hardness distribution measurements, metallography, scanning electron microscopy, and EDS spectrometer have been used in the analysis of this surface damage mechanism. In this work, the metallurgical parameters were formulated which describe the microwelding phenomenon after field usage and after accelerated testing. It was demonstrated that the high output water-cooled two-stroke engine accelerated bench test reproduces the field run engine microwelding phenomenon in 30 minutes. It was shown that the best prevention of the microwelding phenomenon was provided when the piston and piston ring surfaces were separated by a soft, wear and heat resistant coating, integrally bonded to the piston ring.

  18. Magnetic response to applied electrostatic field in external magnetic field

    NASA Astrophysics Data System (ADS)

    Adorno, T. C.; Gitman, D. M.; Shabad, A. E.

    2014-04-01

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

  19. Theory of fossil magnetic field

    NASA Astrophysics Data System (ADS)

    Dudorov, Alexander E.; Khaibrakhmanov, Sergey A.

    2015-02-01

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

  20. Origin of cosmic magnetic fields.

    PubMed

    Campanelli, Leonardo

    2013-08-01

    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

  1. The Capacitive Magnetic Field Sensor

    NASA Astrophysics Data System (ADS)

    Zyatkov, D. O.; Yurchenko, A. V.; Balashov, V. B.; Yurchenko, V. I.

    2016-01-01

    The results of a study of sensitive element magnetic field sensor are represented in this paper. The sensor is based on the change of the capacitance with an active dielectric (ferrofluid) due to the magnitude of magnetic field. To prepare the ferrofluid magnetic particles are used, which have a followingdispersion equal to 50 < Ø < 56, 45 < Ø < 50, 40 < Ø < 45 and Ø < 40micron of nanocrystalline alloy of brand 5BDSR. The dependence of the sensitivity of the capacitive element from the ferrofluid with different dispersion of magnetic particles is considered. The threshold of sensitivity and sensitivity of a measuring cell with ferrofluid by a magnetic field was determined. The experimental graphs of capacitance change of the magnitude of magnetic field are presented.

  2. Measurements of magnetic field alignment

    SciTech Connect

    Kuchnir, M.; Schmidt, E.E.

    1987-11-06

    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.

  3. Non-disjunction mutations in Drosophila exposed to magnetic fields

    NASA Astrophysics Data System (ADS)

    Levengood, W. C.

    1987-09-01

    The frequency of XO mutations in Drosophila melanogaster was significantly higher than normal in magnetic field exposed, immature males, than in exposed, mature males. Mutation levels increased with magnetic field strength. Intercellular rings of black magnetic particles were formed in the high magnetic flux region of dorsally exposed, early stage pupae and to a lesser degree in the abdomen of young adult females. Orientation of minute, chromosome associated, magnetic domains within the microenvironment of the developing organism was believed to alter oxidative processes within maturing X+ sperm which during fertilization were incompatible with and destructive to an Xw chromosome in the zygote.

  4. Magnetic fields in young galaxies

    NASA Astrophysics Data System (ADS)

    Nordlund, Åke; Rögnvaldsson, Örnólfur

    We have studied the fate of initial magnetic fields in the hot halo gas out of which the visible parts of galaxies form, using three-dimensional numerical MHD-experiments. The halo gas undergoes compression by several orders of magnitude in the subsonic cooling flow that forms the cold disk. The magnetic field is carried along and is amplified considerably in the process, reaching μG levels for reasonable values of the initial ratio of magnetic to thermal energy density.

  5. The MAVEN Magnetic Field Investigation

    NASA Astrophysics Data System (ADS)

    Connerney, J. E. P.; Espley, J.; Lawton, P.; Murphy, S.; Odom, J.; Oliversen, R.; Sheppard, D.

    2015-12-01

    The MAVEN magnetic field investigation is part of a comprehensive particles and fields subsystem that will measure the magnetic and electric fields and plasma environment of Mars and its interaction with the solar wind. The magnetic field instrumentation consists of two independent tri-axial fluxgate magnetometer sensors, remotely mounted at the outer extremity of the two solar arrays on small extensions ("boomlets"). The sensors are controlled by independent and functionally identical electronics assemblies that are integrated within the particles and fields subsystem and draw their power from redundant power supplies within that system. Each magnetometer measures the ambient vector magnetic field over a wide dynamic range (to 65,536 nT per axis) with a resolution of 0.008 nT in the most sensitive dynamic range and an accuracy of better than 0.05 %. Both magnetometers sample the ambient magnetic field at an intrinsic sample rate of 32 vector samples per second. Telemetry is transferred from each magnetometer to the particles and fields package once per second and subsequently passed to the spacecraft after some reformatting. The magnetic field data volume may be reduced by averaging and decimation, when necessary to meet telemetry allocations, and application of data compression, utilizing a lossless 8-bit differencing scheme. The MAVEN magnetic field experiment may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. A spacecraft magnetic control program was implemented to provide a magnetically clean environment for the magnetic sensors and the MAVEN mission plan provides for occasional spacecraft maneuvers—multiple rotations about the spacecraft x and z axes—to characterize spacecraft fields and/or instrument offsets in flight.

  6. The MAVEN Magnetic Field Investigation

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Espley, J.; Lawton, P.; Murphy, S.; Odom, J.; Oliversen, R.; Sheppard, D.

    2014-01-01

    The MAVEN magnetic field investigation is part of a comprehensive particles and fields subsystem that will measure the magnetic and electric fields and plasma environment of Mars and its interaction with the solar wind. The magnetic field instrumentation consists of two independent tri-axial fluxgate magnetometer sensors, remotely mounted at the outer extremity of the two solar arrays on small extensions ("boomlets"). The sensors are controlled by independent and functionally identical electronics assemblies that are integrated within the particles and fields subsystem and draw their power from redundant power supplies within that system. Each magnetometer measures the ambient vector magnetic field over a wide dynamic range (to 65,536 nT per axis) with a quantization uncertainty of 0.008 nT in the most sensitive dynamic range and an accuracy of better than 0.05%. Both magnetometers sample the ambient magnetic field at an intrinsic sample rate of 32 vector samples per second. Telemetry is transferred from each magnetometer to the particles and fields package once per second and subsequently passed to the spacecraft after some reformatting. The magnetic field data volume may be reduced by averaging and decimation, when necessary to meet telemetry allocations, and application of data compression, utilizing a lossless 8-bit differencing scheme. The MAVEN magnetic field experiment may be reconfigured in flight to meet unanticipated needs and is fully hardware redundant. A spacecraft magnetic control program was implemented to provide a magnetically clean environment for the magnetic sensors and the MAVEN mission plan provides for occasional spacecraft maneuvers - multiple rotations about the spacecraft x and z axes - to characterize spacecraft fields and/or instrument offsets in flight.

  7. Monte Carlo simulation for thermal assisted reversal process of micro-magnetic torus ring with bistable closure domain structure

    NASA Astrophysics Data System (ADS)

    Terashima, Kenichi; Suzuki, Kenji; Yamaguchi, Katsuhiko

    2016-04-01

    Monte Carlo simulations were performed for temperature dependences of closure domain parameter for a magnetic micro-torus ring cluster under magnetic field on limited temperature regions. Simulation results show that magnetic field on tiny limited temperature region can reverse magnetic closure domain structures when the magnetic field is applied at a threshold temperature corresponding to intensity of applied magnetic field. This is one of thermally assisted switching phenomena through a self-organization process. The results show the way to find non-wasteful pairs between intensity of magnetic field and temperature region for reversing closure domain structure by temperature dependence of the fluctuation of closure domain parameter. Monte Carlo method for this simulation is very valuable to optimize the design of thermally assisted switching devices.

  8. Cosmic Magnetic Fields - An Overview

    NASA Astrophysics Data System (ADS)

    Wielebinski, Richard; Beck, Rainer

    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.

  9. DC septum magnets for the damping rings of the SLC SLAC Linear Collider

    SciTech Connect

    Bijleveld, J.; Peterson, J.M.; Jensen, D.

    1986-07-01

    The injection/extraction systems of the 1.21 GeV Stanford Linear Collider (SLC) damping rings uses four pairs of water cooled septum magnets. Each pair consists of a thin-septum, low-field (3 mm, 3 kilogauss) magnet plus a thick-septum, high-field (12 mm, 8 kilogauss) model. In the latest design cooling reliability was improved by using stainless-steel tubing imbedded in the copper. The operating current in each is 2600 amperes, at a density of up to 120 amperes per mmS. Plasma-sprayed alumina is used to provide electrical insulation. The magnet system is compatible with 10 Z torr ultra-high vacuum. The magnet design, fabrication, and measurements are described.

  10. Performance improvement of an extraction Lambertson septum magnet in the SNS accumulator ring

    SciTech Connect

    Wang, Jian-Guang

    2009-04-01

    The SNS ring Extraction Lambertson Septum magnet contains a strong skew quadrupole term, which has been identified as the source of causing a beam profile distortion on the target. We have performed 3D computer simulations to study the magnetic field quality in the magnet. The skew quad term is computed with different methods in simulations and is compared to measurement data. The origin of the large skew quad term is thoroughly investigated. The remedy for minimizing the skew quad term by modifying the magnet is proposed. Particle tracking is performed to verify the beam profile evolution through the existing and modified septum. The magnetic interference to the septum performance from an adjacent quadrupole is also assessed.

  11. Electroplated FeNi ring cores for fluxgates with field induced radial anisotropy

    NASA Astrophysics Data System (ADS)

    Butta, M.; Ripka, P.; Janosek, M.; Pribil, M.

    2015-05-01

    Being able to control the anisotropy of a magnetic core plays an important role in the development of a fluxgate sensor. Our aim is to induce anisotropy orthogonal to the direction of excitation because it generates a stable, low-noise fluxgate, as cited in the literature. In this paper, we present an original method for electroplating a ring core for a fluxgate with built-in radial anisotropy by performing the electroplating in a radial field produced by a novel yoke. The results show that the resulting anisotropy is homogeneously radial and makes the magnetization rotate, avoiding domain wall movement for low excitation fields.

  12. Simulating and detecting artificial magnetic fields in trapped atoms

    SciTech Connect

    Rosenkranz, Matthias; Klein, Alexander; Jaksch, Dieter

    2010-01-15

    A Bose-Einstein condensate exhibiting a nontrivial phase induces an artificial magnetic field in immersed impurity atoms trapped in a stationary, ring-shaped optical lattice. We present an effective Hamiltonian for the impurities for two condensate setups: the condensate in a rotating ring and in an excited rotational state in a stationary ring. We use Bogoliubov theory to derive analytical formulas for the induced artificial magnetic field and the hopping amplitude in the limit of low condensate temperature where the impurity dynamics is coherent. As methods for observing the artificial magnetic field we discuss time-of-flight imaging and mass current measurements. Moreover, we compare the analytical results of the effective model to numerical results of a corresponding two-species Bose-Hubbard model. We also study numerically the clustering properties of the impurities and the quantum chaotic behavior of the two-species Bose-Hubbard model.

  13. The Primordial Origin Model of Magnetic Fields in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Sofue, Yoshiaki; Machida, Mami; Kudoh, Takahiro

    2010-10-01

    We propose a primordial-origin model for composite configurations of global magnetic fields in spiral galaxies. We show that a uniform tilted magnetic field wound up into a rotating disk galaxy can evolve into composite magnetic configurations comprising bisymmetric spiral (S = BSS), axisymmetric spiral (A = ASS), plane-reversed spiral (PR), and/or ring (R) fields in the disk, and vertical (V) fields in the center. By MHD simulations we show that these composite galactic fields are indeed created from a weak primordial uniform field, and that different configurations can co-exist in the same galaxy. We show that spiral fields trigger the growth of two-armed gaseous arms. The centrally accumulated vertical fields are twisted and produce a jet toward the halo. We found that the more vertical was the initial uniform field, the stronger was the formed magnetic field in the galactic disk.

  14. PREPROCESSING MAGNETIC FIELDS WITH CHROMOSPHERIC LONGITUDINAL FIELDS

    SciTech Connect

    Yamamoto, Tetsuya T.; Kusano, K.

    2012-06-20

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

  15. Operational experience with SLC damping ring kicker magnets

    SciTech Connect

    Mattison, T.; Cassel, R.; Donaldson, A.; Gross, G.; Harvey, A.

    1991-05-01

    The damping ring kickers for the SLAC Linear Collider must provide 7 mrad kicks to 1.2 GeV beams with 60 nsec rise and fall times and fit in a 50 cm length around a 21 mm diameter ceramic beam pipe. This requires that they operate at up to 40 KV. The construction and operation of two types of quasi-coaxial ferrite magnet potted with RTV silicone rubber is discussed. Production yield has been improved by changes in RTV degassing, transfer, and cure. Operation lifetime is dominated by voltage, radiation, and thermal cycling. 4 refs., 2 figs.

  16. MonitoRing - Magnetic induction measurement at your fingertip

    NASA Astrophysics Data System (ADS)

    Teichmann, D.; Foussier, J.; Löschcke, D.; Leonhardt, S.; Walter, M.

    2013-04-01

    The device presented in this paper is a sensor for monitoring pulse by measuring the bioimpedance of the thumb in an unobtrusive way. The sensor is based on magnetic induction measurement, a non-contact technique for measuring impedance changes of objects [1]. The sensor head of the presented system has the form of a ring and is worn on the finger. The developed technique renders the possibility of easy and unnoticed pulse recording during every day activities without the need for, e.g. electrodes, a pulse belt around the chest, or a pulse photoplethysmographic finger or ear clip.

  17. Eddy currents induced by RF magnetic fields in biological bodies

    NASA Astrophysics Data System (ADS)

    Lee, Jen-Hwang; Chen, Kun-Mu

    A new theoretical method for determining the electric field or the eddy current induced by a uniform RF magnetic field or a beam of RF magnetic field in a biological body of rotational symmetry is presented. The body is subdivided into a number of circular rings with various radii and cross-sectional areas. The induced electric field or eddy current in each ring is then numerically determined on the basis of the theory of vector potential and the moment method. Numerical examples are given, and the results based on the present theory are found to deviate significantly from the often used, quasi-static solutions. An experiment was conducted to measure the electric fields induced by a UHF magnetic field in phantom biological models. The theory was verified by the experiment and the existing theoretical results.

  18. Preface: Cosmic magnetic fields

    NASA Astrophysics Data System (ADS)

    Kosovichev, Alexander

    2015-02-01

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

  19. Rotating superconductor magnet for producing rotating lobed magnetic field lines

    DOEpatents

    Hilal, Sadek K.; Sampson, William B.; Leonard, Edward F.

    1978-01-01

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

  20. The magnetic field of Neptune

    NASA Technical Reports Server (NTRS)

    Connerney, J. E. P.; Acuna, Mario H.; Ness, Norman F.

    1992-01-01

    A model is given of the planetary magnetic field of Neptune based on a spherical harmonic analysis of the observations obtained by the Voyager 2. Generalized inverse techniques are used to partially solve a severely underdetermined inverse problem, and the resulting model is nonunique since the observations are limited in spatial distribution. Dipole, quadrupole, and octupole coefficients are estimated independently of other terms, and the parameters are shown to be well constrained by the measurement data. The large-scale features of the magnetic field including dipole tilt, offset, and harmonic content are found to characterize a magnetic field that is similar to that of Uranus. The traits of Neptune's magnetic field are theorized to relate to the 'ice' interior of the planet, and the dynamo-field generation reflects this poorly conducting planet.

  1. Low-Magnetic-Field Magnetars

    NASA Astrophysics Data System (ADS)

    Turolla, Roberto; Esposito, Paolo

    2013-11-01

    It is now widely accepted that soft gamma repeaters and anomalous X-ray pulsars are the observational manifestations of magnetars, i.e. sources powered by their own magnetic energy. This view was supported by the fact that these "magnetar candidates" exhibited, without exception, a surface dipole magnetic field (as inferred from the spin-down rate) in excess of the electron critical field (≃ 4.4×1013 G). The recent discovery of fully qualified magnetars, SGR 0418+5729 and Swift J1822.3-1606, with dipole magnetic field well in the range of ordinary radio pulsars posed a challenge to the standard picture, showing that a very strong field is not necessary for the onset of magnetar activity (chiefly bursts and outbursts). Here we summarize the observational status of the low-magnetic-field magnetars and discuss their properties in the context of the mainstream magnetar model and its main alternatives.

  2. Preflare magnetic and velocity fields

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  3. A RING OF POLARIZED LIGHT: EVIDENCE FOR TWISTED CORONAL MAGNETISM IN CAVITIES

    SciTech Connect

    Dove, J. B.; Gibson, S. E.; Rachmeler, L. A.; Tomczyk, S.; Judge, P.

    2011-04-10

    Coronal prominence cavities may be manifestations of twisted or sheared magnetic fields capable of storing the energy required to drive solar eruptions. The Coronal Multi-Channel Polarimeter (CoMP), recently installed at Mauna Loa Solar Observatory, can measure polarimetric signatures of current-carrying magnetohydrodynamic (MHD) systems. For the first time, this instrument offers the capability of daily full-Sun observations of the forbidden lines of Fe XIII with high enough spatial resolution and throughput to measure polarimetric signatures of current-carrying MHD systems. By forward-calculating CoMP observables from analytic MHD models of spheromak-type magnetic flux ropes, we show that a predicted observable for such flux ropes oriented along the line of sight is a bright ring of linear polarization surrounding a region where the linear polarization strength is relatively depleted. We present CoMP observations of a coronal cavity possessing such a polarization ring.

  4. Magnetic confinement in a ring-cusp ion thruster discharge plasma

    SciTech Connect

    Sengupta, Anita

    2009-05-01

    An experimental investigation, in conjunction with a volume averaged analytical model, has been developed to improve the confinement and production of the discharge plasma for plasma thrusters and ion sources. The research conducted explores the discharge performance of a ring-cusp ion source based on the magnetic field configuration, geometry, and power level. Analytical formulations for electron and ion confinement are developed to predict the ionization efficiency for a given discharge chamber design. Explicit determination of discharge loss and volume averaged plasma parameters are obtained via a series of experimental measurements on a ring-cusp NASA Solar Technology Application Readiness (NSTAR) ion thruster to assess the validity of the analytical model. Measurements of the discharge loss with multiple magnetic field configurations compare well with plasma parameter predictions for propellant utilizations between 80% and 95%. The results indicate that increasing the magnetic strength of the first closed magnetic contour line reduces Maxwellian electron diffusion and electrostatically confines the ion population and subsequent loss to the anode wall. The results also indicate that increasing the strength and minimizing the area of the magnetic cusps improves primary electron confinement, increasing the probability of an ionization collision prior to loss at the cusp.

  5. Magnetic Field of Strange Dwarfs

    NASA Astrophysics Data System (ADS)

    Baghdasaryan, D. S.

    2016-03-01

    The generation of a magnetic field in a strange quark star owing to differential rotation of the superfluid and superconducting quark core relative to the normal electron-nuclear crust of the star is examined. The maximum possible magnetic field on the surface is estimated for various models of strange dwarfs. Depending on the configuration parameters, i.e., the mass M and radius R of the star, a range of 103-105 G is found. These values of the magnetic field may be an additional condition for identification of strange dwarfs among the extensive class of observed white dwarfs.

  6. AC photovoltaic module magnetic fields

    SciTech Connect

    Jennings, C.; Chang, G.J.; Reyes, A.B.; Whitaker, C.M.

    1997-12-31

    Implementation of alternating current (AC) photovoltaic (PV) modules, particularly for distributed applications such as PV rooftops and facades, may be slowed by public concern about electric and magnetic fields (EMF). This paper documents magnetic field measurements on an AC PV module, complementing EMF research on direct-current PV modules conducted by PG and E in 1993. Although not comprehensive, the PV EMF data indicate that 60 Hz magnetic fields (the EMF type of greatest public concern) from PV modules are comparable to, or significantly less than, those from household appliances. Given the present EMF research knowledge, AC PV module EMF may not merit considerable concern.

  7. Magnetoconvection in sheared magnetic fields

    SciTech Connect

    Bian, N. H.; Garcia, O. E.

    2008-10-15

    The development of magnetoconvection in a sheared magnetic field is investigated. The equilibrium magnetic field B{sub 0} is horizontal and its orientation varies linearly along the vertical axis. Preliminary consideration of the transition from the inertial to the viscous regime of the gravitational resistive interchange instability, reveals that the latter is characterized by the existence of viscoresistive boundary layers of vertical width which scales as Q{sup -1/6}, where Q is the Chandrasekhar number. The situation is analogous to the one encountered in magnetically confined laboratory plasmas, where convective flows are constrained by the magnetic shear to develop in boundary layers located around resonant magnetic surfaces in order to fulfill the 'interchange condition'k{center_dot}B{sub 0}=0, where k is the wave vector of the magnetic perturbation. It follows that when the effect of thermal diffusion is taken into account in the process, convection can only occur above a certain critical value of the Rayleigh number which scales as Q{sup 2/3} for large Q. At the onset, the convection pattern is a superposition of identically thin convective rolls everywhere aligned with the local magnetic field lines and which therefore adopt the magnetic field geometry, a situation also reminiscent of the penumbra of sunspots. Using this degeneracy, equations describing the weakly nonlinear state are obtained and discussed. A reduced magnetohydrodynamic description of magnetoconvection is introduced. Since it is valid for arbitrary magnetic field configurations, it allows a simple extension to the case where there exists an inclination between the direction of gravity and the plane spanned by the equilibrium magnetic field. These reduced magnetohydrodynamic equations are proposed as a powerful tool for further investigations of magnetoconvection in more complex field line geometries.

  8. Nonlinear magnetization dynamics of antiferromagnetic spin resonance induced by intense terahertz magnetic field

    NASA Astrophysics Data System (ADS)

    Mukai, Y.; Hirori, H.; Yamamoto, T.; Kageyama, H.; Tanaka, K.

    2016-01-01

    We report on the nonlinear magnetization dynamics of a HoFeO3 crystal induced by a strong terahertz magnetic field resonantly enhanced with a split ring resonator and measured with magneto-optical Kerr effect microscopy. The terahertz magnetic field induces a large change (˜40%) in the spontaneous magnetization. The frequency of the antiferromagnetic resonance decreases in proportion to the square of the magnetization change. A modified Landau-Lifshitz-Gilbert equation with a phenomenological nonlinear damping term quantitatively reproduced the nonlinear dynamics.

  9. Magnetic Field Generation in Stars

    NASA Astrophysics Data System (ADS)

    Ferrario, Lilia; Melatos, Andrew; Zrake, Jonathan

    2015-10-01

    Enormous progress has been made on observing stellar magnetism in stars from the main sequence (particularly thanks to the MiMeS, MAGORI and BOB surveys) through to compact objects. Recent data have thrown into sharper relief the vexed question of the origin of stellar magnetic fields, which remains one of the main unanswered questions in astrophysics. In this chapter we review recent work in this area of research. In particular, we look at the fossil field hypothesis which links magnetism in compact stars to magnetism in main sequence and pre-main sequence stars and we consider why its feasibility has now been questioned particularly in the context of highly magnetic white dwarfs. We also review the fossil versus dynamo debate in the context of neutron stars and the roles played by key physical processes such as buoyancy, helicity, and superfluid turbulence, in the generation and stability of neutron star fields.

  10. The polar heliospheric magnetic field

    NASA Technical Reports Server (NTRS)

    Jokipii, J. R.; Kota, J.

    1989-01-01

    It is suggested that the polar heliospheric magnetic field, at large heliocentric distances, may deviate considerably from the generally accepted Archimedean spiral. Instead, it is suggested that the large-scale field near the poles may be dominated by randomly-oriented transverse magnetic fields with magnitude much larger than the average spiral. The average vector field is still the spiral, but the average magnitude may be much larger. In addition, the field direction is transverse to the radial direction most of the time instead of being nearly radial. This magnetic-field structure has important consequences for the transport of cosmic rays. Preliminary model calculations suggest changes in the radial gradient of galactic cosmic rays which may improve agreement with observations.

  11. Measuring Earth's Magnetic Field Simply.

    ERIC Educational Resources Information Center

    Stewart, Gay B.

    2000-01-01

    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)

  12. Effects of Magnetic Fields on Bar Substructures in Barred Galaxies

    NASA Astrophysics Data System (ADS)

    Kim, Woong-Tae

    2015-03-01

    To study the effects of magnetic fields on the properties of bar substructures, we run two-dimensional, ideal MHD simulations of barred galaxies under the influence of a non-axisymmetric bar potential. In the bar regions, magnetic fields reduce density compression in the dust-lane shocks, while removing angular momentum further from the gas at the shocks. This evidently results in a smaller and more distributed ring, and a larger mass inflows rate to the galaxy center in models with stronger magnetic fields. In the outer regions, an MHD dynamo due to the combined action of the bar potential and background shear operates, amplifying magnetic fields near the corotation resonance. In the absence of spiral arms, the amplified fields naturally shape into trailing magnetic arms with strong fields and low density. The reader is refereed to Kim & Stone (2012) for a detailed presentation of the simulation outcomes.

  13. RANDOM AND SYSTEMATIC FIELD ERRORS IN THE SNS RING: A STUDY OF THEIR EFFECTS AND COMPENSATION

    SciTech Connect

    GARDNER,C.J.; LEE,Y.Y.; WENG,W.T.

    1998-06-22

    The Accumulator Ring for the proposed Spallation Neutron Source (SNS) [l] is to accept a 1 ms beam pulse from a 1 GeV Proton Linac at a repetition rate of 60 Hz. For each beam pulse, 10{sup 14} protons (some 1,000 turns) are to be accumulated via charge-exchange injection and then promptly extracted to an external target for the production of neutrons by spallation. At this very high intensity, stringent limits (less than two parts in 10,000 per pulse) on beam loss during accumulation must be imposed in order to keep activation of ring components at an acceptable level. To stay within the desired limit, the effects of random and systematic field errors in the ring require careful attention. This paper describes the authors studies of these effects and the magnetic corrector schemes for their compensation.

  14. Magnetic fields on the Sun

    NASA Technical Reports Server (NTRS)

    Howard, R.

    1981-01-01

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

  15. Homometallic and Heterometallic Antiferromagnetic Rings: Magnetic Properties Studied by Nuclear Magnetic Resonance

    SciTech Connect

    Casadei, Cecilia

    2012-05-09

    The aim of the present thesis is to investigate the local magnetic properties of homometallic Cr{sub 8} antiferromagnetic (AFM) ring and the changes occurring by replacing one Cr{sup 3+} ion with diamagnetic Cd{sup 2+} (Cr{sub 7}Cd) and with Ni{sup 2+} (Cr{sub 7}Ni). In the heterometallic ring a redistribution of the local magnetic moment is expected in the low temperature ground state. We have investigated those changes by both {sup 53}Cr-NMR and {sup 19}F-NMR. We have determined the order of magnitude of the transferred hyperfine coupling constant {sup 19}F - M{sup +} where M{sup +} = Cr{sup 3+}, Ni{sup 2+} in the different rings. This latter result gives useful information about the overlapping of the electronic wavefunctions involved in the coordinative bond.

  16. Optical sensor of magnetic fields

    DOEpatents

    Butler, M.A.; Martin, S.J.

    1986-03-25

    An optical magnetic field strength sensor for measuring the field strength of a magnetic field comprising a dilute magnetic semi-conductor probe having first and second ends, longitudinally positioned in the magnetic field for providing Faraday polarization rotation of light passing therethrough relative to the strength of the magnetic field. Light provided by a remote light source is propagated through an optical fiber coupler and a single optical fiber strand between the probe and the light source for providing a light path therebetween. A polarizer and an apparatus for rotating the polarization of the light is provided in the light path and a reflector is carried by the second end of the probe for reflecting the light back through the probe and thence through the polarizer to the optical coupler. A photo detector apparatus is operably connected to the optical coupler for detecting and measuring the intensity of the reflected light and comparing same to the light source intensity whereby the magnetic field strength may be calculated.

  17. Magnetic measurements of the 10 T superconducting wiggler for the SPring-8 storage ring

    NASA Astrophysics Data System (ADS)

    Batrakov, A.; Borovikov, V.; Bekhtenev, E.; Fedurin, M.; Hara, M.; Karpov, G.; Kuzin, M.; Mezentsev, N.; Miahara, Y.; Shimada, T.; Shkaruba, V.; Soutome, K.; Tzumaki, K.

    2001-07-01

    In 1999, in the frame of the project ISTC #767 "Budker INP/RIKEN Slow Positron Source", the Budker Institute of Nuclear Physics had made a 10 T Three-pole Superconducting Wiggler. The wiggler will be the keystone of this project by its installation on the SPring-8 storage ring for powerful gamma ray generation ( λ c=450 keV ), that will be used for slow positron production ( Nγ( ɛ>1 MeV)˜10 15, γ/s I e=0.1 A ). A. Ando et al., Proposal of the high magnetic field super conducting WLS for slow positron source at SPring-8, presented at SR1 '97 Conference. In January, 2000, the wiggler was transported to SPring-8, where the last test and measurements were carried out in collaboration with Japan. In this article, the results of measurements of the magnetic field, finding the magnetic field amplitude by an NMR probe, the definition of feed current relations by stretch current wire method, the calibration of a Hall probe in the high magnetic field, and the measurement of the magnetic field profile by a Hall probe are presented.

  18. Magnetic field induced dynamical chaos

    SciTech Connect

    Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra

    2013-12-15

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

  19. Magnetic field induced dynamical chaos.

    PubMed

    Ray, Somrita; Baura, Alendu; Bag, Bidhan Chandra

    2013-12-01

    In this article, we have studied the dynamics of a particle having charge in the presence of a magnetic field. The motion of the particle is confined in the x-y plane under a two dimensional nonlinear potential. We have shown that constant magnetic field induced dynamical chaos is possible even for a force which is derived from a simple potential. For a given strength of the magnetic field, initial position, and velocity of the particle, the dynamics may be regular, but it may become chaotic when the field is time dependent. Chaotic dynamics is very often if the field is time dependent. Origin of chaos has been explored using the Hamiltonian function of the dynamics in terms of action and angle variables. Applicability of the present study has been discussed with a few examples. PMID:24387560

  20. Numerical analyses of trapped field magnet and stable levitation region of HTSC

    SciTech Connect

    Tsuchimoto, M.; Kojima, T.; Waki, H.; Honma, T.

    1995-05-01

    Stable levitation with a permanent magnet and a bulk high {Tc} superconductor (HTSC) is examined numerically by using the critical state model and the frozen field model. Differences between a permanent magnet and a trapped field magnet are first discussed from property of levitation force. Stable levitation region of the HTSC on a ring magnet and on a solenoid coil are calculated with the numerical methods. Obtained results are discussed from difference of the magnetic field configuration.

  1. Comparisons of Simulated and Observed Stormtime Magnetic Intensities and Ion Plasma Parameters in the Ring Current

    NASA Astrophysics Data System (ADS)

    Chen, M. W.; Guild, T. B.; Lemon, C.; Roeder, J. L.; Le, G.; Schulz, M.

    2009-12-01

    Recent progress in ring current and plasma sheet modeling has shown the importance of a self-consistent treatment of particle transport and magnetic and electric fields in the inner magnetosphere. Models with and without self-consistency can lead to significantly different magnitudes and spatial distributions of plasma pressure and magnetic intensity during disturbed times. In this study we compare simulated and observed stormtime magnetic intensities (GOES and Polar/MFE) and ion densities (LANL/MPA and Polar/CAMMICE) to test how well self-consistent simulations can simultaneously reproduce these quantities. We simulate the ring current and plasma sheet for conditions corresponding to the 11 August 2000 storm using the self-consistent Rice Convection Model-Equilibrium (RCM-E) [Lemon et al., JGR, 2004] with a constant magnetopause location. Using the empirical IMF-dependent model of Tsyganenko and Mukai [JGR, 2003], we specify the plasma sheet pressure and density at 10 RE as the plasma boundary location in the RCM-E. The simulated ion densities at different magnetic local times agree fairly well with those from the re-analysis model of LANL/MPA densities of O’Brien and Lemon [Space Weather, 2007]. We compare the simulated magnetic intensity with the magnetic intensity measured by magnetometers on the GOES satellites at geosynchronous altitude (6.6 RE) and on the Polar satellite. Agreement between the simulated and observed magnetic intensities tends to agree better on the nightside than on the dayside in the inner magnetosphere. In particular, the model cannot account for observed drops in the dayside magnetic intensity during decreases in the solar wind pressure. We will modify the RCM-E to include a time-varying magnetopause location to simulate compressions and expansions associated with variations in the solar wind pressure. We investigate whether this will lead to improved agreement between the simulated and model magnetic intensities.

  2. Theory of a ring laser. [electromagnetic field and wave equations

    NASA Technical Reports Server (NTRS)

    Menegozzi, L. N.; Lamb, W. E., Jr.

    1973-01-01

    Development of a systematic formulation of the theory of a ring laser which is based on first principles and uses a well-known model for laser operation. A simple physical derivation of the electromagnetic field equations for a noninertial reference frame in uniform rotation is presented, and an attempt is made to clarify the nature of the Fox-Li modes for an open polygonal resonator. The polarization of the active medium is obtained by using a Fourier-series method which permits the formulation of a strong-signal theory, and solutions are given in terms of continued fractions. It is shown that when such a continued fraction is expanded to third order in the fields, the familiar small-signal ring-laser theory is obtained.

  3. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Beck, Rainer

    2015-12-01

    Radio synchrotron emission, its polarization and Faraday rotation of the polarization angle are powerful tools to study the strength and structure of magnetic fields in galaxies. Unpolarized synchrotron emission traces isotropic turbulent fields which are strongest in spiral arms and bars (20-30 \\upmu G) and in central starburst regions (50-100 \\upmu G). Such fields are dynamically important; they affect gas flows and drive gas inflows in central regions. Polarized emission traces ordered fields, which can be regular or anisotropic turbulent, where the latter originates from isotropic turbulent fields by the action of compression or shear. The strongest ordered fields (10-15 \\upmu G) are generally found in interarm regions. In galaxies with strong density waves, ordered fields are also observed at the inner edges of spiral arms. Ordered fields with spiral patterns exist in grand-design, barred and flocculent galaxies and in central regions. Ordered fields in interacting galaxies have asymmetric distributions and are a tracer of past interactions between galaxies or with the intergalactic medium.—Faraday rotation measures of the diffuse polarized radio emission from galaxy disks reveal large-scale spiral patterns that can be described by the superposition of azimuthal modes; these are signatures of regular fields generated by mean-field dynamos. "Magnetic arms" between gaseous spiral arms may also be products of dynamo action, but need a stable spiral pattern to develop. Helically twisted field loops winding around spiral arms were found in two galaxies so far. Large-scale field reversals, like the one found in the Milky Way, could not yet be detected in external galaxies. In radio halos around edge-on galaxies, ordered magnetic fields with X-shaped patterns are observed. The origin and evolution of cosmic magnetic fields, in particular their first occurrence in young galaxies and their dynamical importance during galaxy evolution, will be studied with forthcoming radio telescopes like the Square Kilometre Array.

  4. Fast Magnetic Domain-Wall Motion in a Ring-Shaped Nanowire Driven by a Voltage.

    PubMed

    Hu, Jia-Mian; Yang, Tiannan; Momeni, Kasra; Cheng, Xiaoxing; Chen, Lei; Lei, Shiming; Zhang, Shujun; Trolier-McKinstry, Susan; Gopalan, Venkatraman; Carman, Gregory P; Nan, Ce-Wen; Chen, Long-Qing

    2016-04-13

    Magnetic domain-wall motion driven by a voltage dissipates much less heat than by a current, but none of the existing reports have achieved speeds exceeding 100 m/s. Here phase-field and finite-element simulations were combined to study the dynamics of strain-mediated voltage-driven magnetic domain-wall motion in curved nanowires. Using a ring-shaped, rough-edged magnetic nanowire on top of a piezoelectric disk, we demonstrate a fast voltage-driven magnetic domain-wall motion with average velocity up to 550 m/s, which is comparable to current-driven wall velocity. An analytical theory is derived to describe the strain dependence of average magnetic domain-wall velocity. Moreover, one 180° domain-wall cycle around the ring dissipates an ultrasmall amount of heat, as small as 0.2 fJ, approximately 3 orders of magnitude smaller than those in current-driven cases. These findings suggest a new route toward developing high-speed, low-power-dissipation domain-wall spintronics. PMID:27002341

  5. Magnetic fields in quiescent prominences

    NASA Technical Reports Server (NTRS)

    Van Ballegooijen, A. A.; Martens, P. C. H.

    1990-01-01

    The origin of the axial fields in high-latitude quiescent prominences is considered. The fact that almost all quiescent prominences obey the same hemisphere-dependent rule strongly suggests that the solar differential rotation plays an important role in producing the axial fields. However, the observations are inconsistent with the hypothesis that the axial fields are produced by differential rotation acting on an existing coronal magnetic field. Several possible explanations for this discrepancy are considered. The possibility that the sign of the axial field depends on the topology of the magnetic field in which the prominence is embedded is examined, as is the possibility that the neutral line is tilted with respect to the east-west direction, so that differential rotation causes the neutral line also to rotate with time. The possibility that the axial fields of quiescent prominences have their origin below the solar surface is also considered.

  6. Multipole Shimming of Permanent Magnets Using Harmonic CorrectorRings

    SciTech Connect

    Jachmann, Rebecca C.; Trease, David R.; Bouchard, Louis-S.; Sakellariou, Dimitris; Martin, Rachel W.; Schlueter, Ross D.; Budinger,Thomas F.; Pines, Alexander

    2006-10-23

    Shimming systems are required to provide sufficient fieldhomogeneity for high resolution NMR. In certain specialized applications,such as rotating-field NMR and portable (ex-situ) NMR, permanentmagnet-based shimming systems can provide considerable advantages. Wepresent a simple two-dimensional shimming method based on harmoniccorrector rings which can provide arbitrary multipole order shimmingcorrections. Results demonstrate, for example, that quadrupolar ordershimming improves the linewidth by up to and order of magnitude. Anadditional order of magnitude reduction is in principle achievable byultilizing this shimming method for z-gradient correction and higherorder xy gradients.

  7. Least Squares Magnetic-Field Optimization for Portable Nuclear Magnetic Resonance Magnet Design

    SciTech Connect

    Paulsen, Jeffrey L; Franck, John; Demas, Vasiliki; Bouchard, Louis-S.

    2008-03-27

    Single-sided and mobile nuclear magnetic resonance (NMR) sensors have the advantages of portability, low cost, and low power consumption compared to conventional high-field NMR and magnetic resonance imaging (MRI) systems. We present fast, flexible, and easy-to-implement target field algorithms for mobile NMR and MRI magnet design. The optimization finds a global optimum ina cost function that minimizes the error in the target magnetic field in the sense of least squares. When the technique is tested on a ring array of permanent-magnet elements, the solution matches the classical dipole Halbach solution. For a single-sided handheld NMR sensor, the algorithm yields a 640 G field homogeneous to 16 100 ppm across a 1.9 cc volume located 1.5 cm above the top of the magnets and homogeneous to 32 200 ppm over a 7.6 cc volume. This regime is adequate for MRI applications. We demonstrate that the homogeneous region can be continuously moved away from the sensor by rotating magnet rod elements, opening the way for NMR sensors with adjustable"sensitive volumes."

  8. Exact transfer functions for the PEP storage ring magnets and some general characteristics and techniques

    SciTech Connect

    Spencer, J.E.

    1982-05-01

    The exact, ion-optical transfer functions for the dipoles, quadrupoles and sextupoles of the PEP standard PODC cell are calculated for any single particle with initial coordinates (r, p, s). Modifications resulting from radiative energy loss are also calculated and discussed. These functions allow one to characterize individual magnets or classes of magnets by their aberrations and thereby simplify their study and correction. In contrast to high-energy spectrometers where aberrations are often analyzed away, those in storage rings drive series of high order resonances, even for perfect magnets (2), that can produce stop bands and other effects which can seriously limit performance. Thus, one would like to eliminate them altogether or failing this to develop local and global correction schemes. Even then, one should expect higher order effects to influence injection, extraction or single-pass systems either because of orbit distortions or overly large phase spece distortions such as may occur in low-beta insertions or any final-focus optics. The term exact means that the results here are based on solving the relativistic Lorentz force equation with accurate representations of measured magnetostatic fields. Such fields satisfy Maxwell's equations and are the actual fields seen by a particle as it propagates around a real storage ring. This is discussed in detail and illustrated with examples that show that this is possible, practical and may even be useful.

  9. The magnetic field of Mercury

    NASA Technical Reports Server (NTRS)

    Ness, N. F.

    1979-01-01

    The paper examines the magnetic field observations and their analyses relating to the determination of the Mercury magnetic field. Methods of analyzing data included: (1) comparison of bow shock and magnetopause relative positions at Mercury to the earth, (2) direct spherical harmonic analysis, (3) magnetosphere modeling by an image dipole, and (4) scaling of a mathematical model for the terrestrial magnetosphere. Dipole moments were determined using partial quadrupole and octupole terms to improve the least-square fit of models to observations; analyses by method (2) yield a convergent series of dipole moments values considered to best represent the intrinsic planetary field. Finally, it is suggested that the origin of the magnetic field of Mercury cannot be uniquely determined, but the sources of convective energy may be radiogenic decay and heat release, gravitational settling, and differentiation of processional torques.

  10. Optimization of the permanent magnet optical klystron for the SUPER-ACO storage ring free electron laser

    NASA Astrophysics Data System (ADS)

    Couprie, M. E.; Bazin, C.; Billardon, M.

    1989-06-01

    A permanent magnet optical klystron has been optimized for free electron laser experiments and optical harmonic generation on the new storage ring SUPER-ACO at Orsay. The conditions of the optimization and the different steps of the field characterization measurements of this insertion device are discussed. Its effects on the stored beam and the undulator radiation measurements are described.

  11. Variable-field permanent magnet quadrupole for the SSC

    SciTech Connect

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

    1993-10-01

    A set of compact variable-field permanent-magnet quadrupoles have been designed, fabricated, and tested for use In the SSC linac matching section. The quadrupoles have 24 mm-diameter apertures and 40 mm-long poles. The hybrid (permanent-magnet and iron) design, uses a fixed core of magnet material (NdFeB) and iron (C-1006) surrounded by a rotating ring of the same magnet material and iron. The quadrupole gradient-length product can be smoothly varied from a minimum of 0.7 T up to a maximum, of 4.3 T by a 90{degrees} rotation of the outer ring of iron and magnet material.

  12. Comparison of spin dynamics and magnetic properties in antiferromagnetic closed and open molecular Cr-based rings.

    PubMed

    Adelnia, Fatemeh; Bordonali, Lorenzo; Mariani, Manuel; Bordignon, Sara; Timco, Grigore; Winpenny, Richard; Borsa, Ferdinando; Lascialfari, Alessandro

    2015-12-23

    We present magnetization and (1)H nuclear magnetic resonance (NMR) measurements performed in both closed Cr8 and open Cr8Zn antiferromagnetic molecular rings in the temperature range 1.65  <  T  <  300 K at different external magnetic fields. The magnetization measurements on Cr8Zn are consistent with a small decrease of the exchange constant J(Cr-Cr) and a much smaller gap between the singlet ground state and the first magnetic excited state when compared with the same properties of the closed ring Cr8, in agreement with previous inelastic neutron scattering results. The temperature dependence of the (1)H NMR nuclear spin lattice relaxation rate (NSLR), 1/T1(T), was found to be similar in both open and closed rings with a magnetic field dependent peak centered at a temperature of the order of the corresponding exchange constant J(Cr-Cr). Such main peak in the NSLR could be fitted with a single correlation frequency ω(c1) as in most molecular magnets. At low temperature T  <  4 K, a new feature not observed in previous NMR measurements on antiferromagnetic rings and consisting in a smaller peak of 1/T1(T) which is well resolved only in Cr8Zn, was singled out. This low-T peak indicates the presence of a second correlation frequency ω(c2) of the magnetization, found to be quite different between the two rings and thus possibly reflecting the different low temperature level structure associated with the different spin topology. The presence of ω(c2) is confirmed by the NMR spin-spin relaxation rate enhancement, which generates a two-steps wipe-out effect of the NMR signal intensity. PMID:26609709

  13. Comparison of spin dynamics and magnetic properties in antiferromagnetic closed and open molecular Cr-based rings

    NASA Astrophysics Data System (ADS)

    Adelnia, Fatemeh; Bordonali, Lorenzo; Mariani, Manuel; Bordignon, Sara; Timco, Grigore; Winpenny, Richard; Borsa, Ferdinando; Lascialfari, Alessandro

    2015-12-01

    We present magnetization and 1H nuclear magnetic resonance (NMR) measurements performed in both closed Cr8 and open Cr8Zn antiferromagnetic molecular rings in the temperature range 1.65  <  T  <  300 K at different external magnetic fields. The magnetization measurements on Cr8Zn are consistent with a small decrease of the exchange constant J Cr-Cr and a much smaller gap between the singlet ground state and the first magnetic excited state when compared with the same properties of the closed ring Cr8, in agreement with previous inelastic neutron scattering results. The temperature dependence of the 1H NMR nuclear spin lattice relaxation rate (NSLR), 1/T 1(T), was found to be similar in both open and closed rings with a magnetic field dependent peak centered at a temperature of the order of the corresponding exchange constant J Cr-Cr. Such main peak in the NSLR could be fitted with a single correlation frequency ω c1 as in most molecular magnets. At low temperature T  <  4 K, a new feature not observed in previous NMR measurements on antiferromagnetic rings and consisting in a smaller peak of 1/T 1(T) which is well resolved only in Cr8Zn, was singled out. This low-T peak indicates the presence of a second correlation frequency ω c2 of the magnetization, found to be quite different between the two rings and thus possibly reflecting the different low temperature level structure associated with the different spin topology. The presence of ω c2 is confirmed by the NMR spin-spin relaxation rate enhancement, which generates a two-steps wipe-out effect of the NMR signal intensity.

  14. Indoor localization using magnetic fields

    NASA Astrophysics Data System (ADS)

    Pathapati Subbu, Kalyan Sasidhar

    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.

  15. Ring current particle distributions during the magnetic storms of 16-18 December 1971

    NASA Technical Reports Server (NTRS)

    Smith, P. H.; Hoffman, R. A.

    1972-01-01

    In an effort to summarize the constrasting development of the stormtime ring currents during the December 16-18, 1971 magnetic storms, maps were drawn indicating the proton energy density spatial/temporal distributions. The maps contain distributions for the 5 to 138 keV protons for each of seven orbits. The first storm was not characteristic of a single substorm nor a fully developed magnetic storm, but it was comprised of a sudden commencement, a positive phase, and multiple substorms producing a small depression in the magnetic field. The second storm was classical in development with a short two hour growth phase. Energy density distribution constrasts for the two storms show the second storm displayed three dominant features over the first storm. They were: (1) the intensities were 2 1/2 times larger, (2) the depths of penetration were 1/2 to 1 Reynolds number lower, and (3) the distribution became symmetric.

  16. Observations of Mercury's magnetic field

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.

    1975-01-01

    Magnetic field data obtained by Mariner 10 during the third and final encounter with the planet Mercury on 16 March 1975 were studied. A well developed bow shock and modest magnetosphere, previously observed at first encounter on 29 March 1974, were again observed. In addition, a much stronger magnetic field near closest approach, 400 gamma versus 98 gamma, was observed at an altitude of 327 km and approximately 70 deg north Mercurian latitude. Spherical harmonic analysis of the data provide an estimate of the centered planetary magnetic dipole of 4.7 x 10 to the 22nd power Gauss/cu cm with the axis tilted 12 deg to the rotation axis and in the same sense as Earth's. The interplanetary field was sufficiently different between first and third encounters that in addition to the very large field magnitude observed, it argues strongly against a complex induction process generating the observed planetary field. While a possibility exists that Mercury possesses a remanent field due to magnetization early in its formation, a present day active dynamo seems to be a more likely candidate for its origin.

  17. Galactic and Intergalactic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Klein, U.; Fletcher, A.

    This course-tested textbook conveys the fundamentals of magnetic fields and relativistic plasma in diffuse cosmic media, with a primary focus on phenomena that have been observed at different wavelengths. Theoretical concepts are addressed wherever necessary, with derivations presented in sufficient detail to be generally accessible. In the first few chapters the authors present an introduction to various astrophysical phenomena related to cosmic magnetism, with scales ranging from molecular clouds in star-forming regions and supernova remnants in the Milky Way, to clusters of galaxies. Later chapters address the role of magnetic fields in the evolution of the interstellar medium, galaxies and galaxy clusters. The book is intended for advanced undergraduate and postgraduate students in astronomy and physics and will serve as an entry point for those starting their first research projects in the field.

  18. Mars Crustal Magnetic Field Remnants

    NASA Technical Reports Server (NTRS)

    2001-01-01

    The radial magnetic field measured is color coded on a global perspective view that shows measurements derived from spacecraft tracks below 200 km overlain on a monochrome shaded relief map of the topography.

    This image shows especially strong Martian magnetic fields in the southern highlands near the Terra Cimmeria and Terra Sirenum regions, centered around 180 degrees longitude from the equator to the pole. It is where magnetic stripes possibly resulting from crustal movement are most prominent. The bands are oriented approximately east - west and are about 100 miles wide and 600 miles long, although the longest band stretches more than 1200 miles.

    The false blue and red colors represent invisible magnetic fields in the Martian crust that point in opposite directions. The magnetic fields appear to be organized in bands, with adjacent bands pointing in opposite directions, giving these stripes a striking similarity to patterns seen in the Earth's crust at the mid-oceanic ridges.

    These data were compiled by the MGS Magnetometer Team led by Mario Acuna at the Goddard Space Flight Center in Greenbelt, MD.

  19. Satellite to study earth's magnetic field

    NASA Technical Reports Server (NTRS)

    1979-01-01

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

  20. The magnetic field of the Milky Way

    NASA Astrophysics Data System (ADS)

    Reid, Mark J.

    Models of the magnetic field configuration of the Milky Way are reviewed. Current analyses of rotation measure data suggest that the Milky Way possesses a bisymmetric-like spiral magnetic field, that field reversals among spiral arms exist, and that the magnetic spiral may not closely match the mass spiral structure. Zeeman measurements of OH masers may provide alternative magnetic field information.

  1. Mechanical aspects of installation of integrated magnets at Solaris synchrotron storage ring

    NASA Astrophysics Data System (ADS)

    Wiechecki, Jaros?aw; Nietuby?, Robert; Kara?, Krzysztof; Wawrzyniak, Adriana; Johansson, Martin; Bulira, Pawe?

    2015-09-01

    Solaris synchrotron storage ring which has been assembled at the beginning of the 2015, consist of twelve integrated magnets blocks performing the part of double bend achromat. Both magnets as well as the whole ring as concept is a replica of Max IV 1.5 GeV ring and utilize pioneering integrated magnets approach. Solaris ring assembly forewent that of its Swedish twin. It is a successful proof of principle experiment showing the feasibility of the chosen approach. On the other hand it was an exercise which brought the knowledge on mechanical behavior of the magnets blocks and matching components, which is of unique importance for further integrated magnets implementations. Hereby we present selected issues related to the ring assembly: block stiffness verification and straightness rectification, vacuum chamber installation, alignment and mechanical stability of the assembled system.

  2. Photospheric and coronal magnetic fields

    SciTech Connect

    Sheeley, N.R., Jr. )

    1991-01-01

    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.

  3. The Giotto magnetic-field investigation

    NASA Technical Reports Server (NTRS)

    Neubauer, F. M.; Acuna, M. H.; Burlaga, L. F.; Franke, B.; Gramkow, B.; Mariani, F.; Musmann, G.; Ness, N. F.; Schmidt, H. U.; Terenzi, T.

    1986-01-01

    The objectives of the Giotto magnetometer experiment are the investigation of the interaction between Comet Halley and the solar wind 0.9 AU from the Sun, to within 500 km of the cometary nucleus, and the study of the interplanetary magnetic field. The instrumentation consists of a triaxial and a separate biaxial system of fluxgate sensors of the ring-core type, the associated analog electronics and a digital processor. The measuring ranges of + or 1 16 up to + or - 65536 nT are digitized by a 12-bit analog-to-digital converter. Memory modes allow the bridging of gaps in telemetry coverage of up to 10 days. Because of the dust hazard near closest approach, a magnetometer boom could not be included in the spacecraft design. The magnetic contamination problem was attacked by the use of two magnetometers and by a magnetic-cleanliness program. In-flight results show that the instrument is working flawlessly, though magnetic-contamination problems remain.

  4. Reduction of the beam emittance in the charged-particle storage rings with the help of periodic magnetic wigglers

    NASA Astrophysics Data System (ADS)

    Bogomyagkov, A. V.; Karyukina, K. Yu.; Levichev, E. B.

    2016-01-01

    Periodic magnetic structures (wigglers) have been successfully used for a long time for controlling beam parameters in charged-particle storage rings for various purposes (including the reduction of emittance). In this work, we optimize the optical functions of the storage ring gap into which a wiggler is installed for a more effective reduction of the emittance. Optimal solutions are obtained for the first time for FODOtype and theoretical minimum emittance (TME) structures. An original method is proposed for suppressing the contribution of the wiggler fields to the radiation excitation of the phase volume of the beam by modulating the field period along the wiggler axis.

  5. Magnetic fields around black holes

    NASA Astrophysics Data System (ADS)

    Garofalo, David A. G.

    Active Galactic Nuclei are the most powerful long-lived objects in the universe. They are thought to harbor supermassive black holes that range from 1 million solar masses to 1000 times that value and possibly greater. Theory and observation are converging on a model for these objects that involves the conversion of gravitational potential energy of accreting gas to radiation as well as Poynting flux produced by the interaction of the rotating spacetime and the electromagnetic fields originating in the ionized accretion flow. The presence of black holes in astrophysics is taking center stage, with the output from AGN in various forms such as winds and jets influencing the formation and evolution of the host galaxy. This dissertation addresses some of the basic unanswered questions that plague our current understanding of how rotating black holes interact with their surrounding magnetized accretion disks to produce the enormous observed energy. Two magnetic configurations are examined. The first involves magnetic fields connecting the black hole with the inner accretion disk and the other involves large scale magnetic fields threading the disk and the hole. We study the effects of the former type by establishing the consequences that magnetic torques between the black hole and the inner accretion disk have on the energy dissipation profile. We attempt a plausible explanation to the observed "Deep Minimum" state in the Seyfert galaxy MCG-6- 30-15. For the latter type of magnetic geometry, we study the effects of the strength of the magnetic field threading the black hole within the context of the cherished Blandford & Znajek mechanism for black hole spin energy extraction. We begin by addressing the problem in the non-relativistic regime where we find that the black hole-threading magnetic field is stronger for greater disk thickness, larger magnetic Prandtl number, and for a larger accretion disk. We then study the problem in full relativity where we show that our Newtonian results are excellent approximations for slowly spinning black holes. We proceed to address the issue of the spin dependence of the Blandford & Znajek power. The result we choose to highlight is our finding that given the validity of our assumption for the dynamical behavior of the so-called plunge region in black hole accretors, rotating black holes produce maximum Poynting flux via the Blandford & Znajek process for a black hole spin parameter of about a [approximate] 0.8. This is contrary to the conventional claim that the maximum electromagnetic flux is achieved for highest black hole spin.

  6. Pioneer 10 and 11 (Jupiter and Saturn) magnetic field experiments

    NASA Technical Reports Server (NTRS)

    Jones, D. E.

    1986-01-01

    Magnet field data obtained by the vector helium magnetometer (VHM) during the encounters of Jupiter (Pioneer 10 and 11) and Saturn (Pioneer 11) was analyzed and interpreted. The puzzling characteristics of the Jovian and Saturnian magnetospheric magnetic fields were studied. An apparent substorm (including thinning of the dayside tail current sheet) was observed at Jupiter, as well as evidence suggesting that at the magnetopause the cusp is at an abnormally low latitude. The characteristics of Saturn's ring current as observed by Pioneer 11 were dramatically different from those suggested by the Voyager observations. Most importantly, very strong perturbations in the azimuthal ring current magnetic field suggest that the plane of the ring was not in the dipole equatorial plane, being tilted 5 to 10 deg. relative to the dipole and undergoing significant changes during the encounter. When these changing currents were corrected for, an improved planetary field determination was obtained. In addition, the ring and azimuthal currents at Saturn displayed significantly different time dependences.

  7. Crystal field and magnetic properties

    NASA Technical Reports Server (NTRS)

    Flood, D. J.

    1977-01-01

    Magnetization and magnetic susceptibility measurements have been made in the temperature range 1.3 to 4.2 K on powdered samples of ErH3. The susceptibility exhibits Curie-Weiss behavior from 4.2 to 2 K, and intercepts the negative temperature axis at theta = 1.05 + or - 0.05 K, indicating that the material is antiferromagnetic. The low field effective moment is 6.77 + or - 0.27 Bohr magnetons per ion. The magnetization exhibits a temperature independent contribution, the slope of which is (5 + or - 1.2) x 10 to the -6th Weber m/kg Tesla. The saturation moment is 3.84 + or - 1 - 0.15 Bohr magnetons per ion. The results can be qualitatively explained by the effects of crystal fields on the magnetic ions. No definitive assignment of a crystal field ground state can be given, nor can a clear choice between cubically or hexagonally symmetric crystal fields be made. For hexagonal symmetry, the first excited state is estimated to be 86 to 100 K above the ground state. For cubic symmetry, the splitting is on the order of 160 to 180 K.

  8. Jupiter's magnetic field and magnetosphere

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.; Behannon, K. W.; Connerney, J. E. P.

    1983-01-01

    Among the planets of the solar system, Jupiter is unique in connection with its size and its large magnetic moment, second only to the sun's. The Jovian magnetic field was first detected indirectly by radio astronomers who postulated its existence to explain observations of nonthermal radio emissions from Jupiter at decimetric and decametric wavelengths. Since the early radio astronomical studies of the Jovian magnetosphere, four spacecraft have flown by the planet at close distances and have provided in situ information about the geometry of the magnetic field and its strength. The Jovian magnetosphere is described in terms of three principal regions. The inner magnetosphere is the region where the magnetic field created by sources internal to the planet dominates. The region in which the equatorial currents flow is denoted as the middle magnetosphere. In the outer magnetosphere, the field has a large southward component and exhibits large temporal and/or spatial variations in magnitude and direction in response to changes in solar wind pressure.

  9. Electric field enhancement and far-field radiation pattern of the nanoantenna with concentric rings.

    PubMed

    Chen, Shih-Wen; Huang, Yi-Han; Chao, Bo-Kai; Hsueh, Chun-Hway; Li, Jia-Han

    2014-12-01

    The optical antennas have the potential in various applications because of their field enhancement and directivity control. The directivity of a dipole antenna can be improved by directivity-enhanced Raman scattering structure, which is a combination of a dipole antenna and a ring reflector layer on a ground plane. The concentric rings can collect the light into the center hole. Depending upon the geometry of the antenna inside the hole, different electric field enhancements can be achieved. In this paper, we propose to combine the concentric rings with the directivity-enhanced Raman scattering structure in order to study its electric field enhancement and the far-field radiation pattern by finite-difference time-domain simulations. Compared with the structure without the concentric rings over the ground plane, it is found that our proposed structure can obtain stronger electric field enhancements and narrower radiation beams because the gold rings can help to couple the light into the nanoantenna and they also scatter light into the far field and modify the far-field radiation pattern. The designed structures were fabricated and the chemical molecules of thiophenol were attached on the structures for surface-enhanced Raman scattering (SERS) measurements. The measured results show that the structure with concentric rings can have stronger SERS signals. The effects of the dielectric layer thickness in our proposed structure on the near-field enhancements and far-field radiation are also investigated. The proposed structure can be useful for several nanoantenna applications, such as sensing or detecting. PMID:26088981

  10. Separation of magnetic field lines

    SciTech Connect

    Boozer, Allen H.

    2012-11-15

    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.

  11. The effects of magnetic field in plume region on the performance of multi-cusped field thruster

    SciTech Connect

    Hu, Peng Liu, Hui Yu, Daren; Gao, Yuanyuan; Mao, Wei

    2015-10-15

    The performance characteristics of a Multi-cusped Field Thruster depending on the magnetic field in the plume region were investigated. Five magnetic field shielding rings were separately mounted near the exit of discharge channel to decrease the strength of magnetic field in the plume region in different levels, while the magnetic field in the upstream was well maintained. The test results show that the electron current increases with the decrease of magnetic field strength in the plume region, which gives rise to higher propellant utilization and lower current utilization. On the other hand, the stronger magnetic field in the plume region improves the performance at low voltages (high current mode) while lower magnetic field improves the performance at high voltages (low current mode). This work can provide some optimal design ideas of the magnetic strength in the plume region to improve the performance of thruster.

  12. The effects of magnetic field in plume region on the performance of multi-cusped field thruster

    NASA Astrophysics Data System (ADS)

    Hu, Peng; Liu, Hui; Mao, Wei; Yu, Daren; Gao, Yuanyuan

    2015-10-01

    The performance characteristics of a Multi-cusped Field Thruster depending on the magnetic field in the plume region were investigated. Five magnetic field shielding rings were separately mounted near the exit of discharge channel to decrease the strength of magnetic field in the plume region in different levels, while the magnetic field in the upstream was well maintained. The test results show that the electron current increases with the decrease of magnetic field strength in the plume region, which gives rise to higher propellant utilization and lower current utilization. On the other hand, the stronger magnetic field in the plume region improves the performance at low voltages (high current mode) while lower magnetic field improves the performance at high voltages (low current mode). This work can provide some optimal design ideas of the magnetic strength in the plume region to improve the performance of thruster.

  13. Magnetic fields in spiral galaxies

    NASA Astrophysics Data System (ADS)

    Krause, Marita

    2015-03-01

    The magnetic field structure in edge-on galaxies observed so far shows a plane-parallel magnetic field component in the disk of the galaxy and an X-shaped field in its halo. The plane-parallel field is thought to be the projected axisymmetric (ASS) disk field as observed in face-on galaxies. Some galaxies addionionally exhibit strong vertical magnetic fields in the halo right above and below the central region of the disk. The mean-field dynamo theory in the disk cannot explain these observed fields without the action of a wind, which also probably plays an important role to keep the vertical scale heights constant in galaxies of different Hubble types and star formation activities, as has been observed in the radio continuum: At λ6 cm the vertical scale heights of the thin disk and the thick disk/halo in a sample of five edge-on galaxies are similar with a mean value of 300 +/- 50 pc for the thin disk and 1.8 +/- 0.2 kpc for the thick disk (a table and references are given in Krause 2011) with our sample including the brightest halo observed so far, NGC 253, with strong star formation, as well as one of the weakest halos, NGC 4565, with weak star formation. If synchrotron emission is the dominant loss process of the relativistic electrons the outer shape of the radio emission should be dumbbell-like as has been observed in several edge-on galaxies like e.g. NGC 253 (Heesen et al. 2009) and NGC 4565. As the synchrotron lifetime t syn at a single frequency is proportional to the total magnetic field strength B t -1.5, a cosmic ray bulk speed (velocity of a galactic wind) can be defined as v CR = h CR /t syn = 2 h z /t syn , where h CR and h z are the scale heights of the cosmic rays and the observed radio emission at this freqnency. Similar observed radio scale heights imply a self regulation mechanism between the galactic wind velocity, the total magnetic field strength and the star formation rate SFR in the disk: v CR ~ B t 1.5 ~ SFR ~ 0.5 (Niklas & Beck 1997).

  14. Magnetic fields in the sun

    NASA Technical Reports Server (NTRS)

    Mullan, D. J.

    1974-01-01

    The observed properties of solar magnetic fields are reviewed, with particular reference to the complexities imposed on the field by motions of the highly conducting gas. Turbulent interactions between gas and field lead to heating or cooling of the gas according to whether the field energy density is less or greater than the maximum kinetic energy density in the convection zone. The field strength above which cooling sets in is 700 gauss. A weak solar dipole field may be primeval, but dynamo action is also important in generating new flux. The dynamo is probably not confined to the convection zone, but extends throughout most of the volume of the sun. Planetary tides appear to play a role in driving the dynamo.

  15. Diagnostics of vector magnetic fields

    NASA Technical Reports Server (NTRS)

    Stenflo, J. O.

    1985-01-01

    It is shown that the vector magnetic fields derived from observations with a filter magnetograph will be severely distorted if the spatially unresolved magnetic structure is not properly accounted for. Thus the apparent vector field will appear much more horizontal than it really is, but this distortion is strongly dependent on the area factor and the temperature line weakenings. As the available fluxtube models are not sufficiently well determined, it is not possible to correct the filter magnetograph observations for these effects in a reliable way, although a crude correction is of course much better than no correction at all. The solution to this diagnostic problem is to observe simultaneously in suitable combinations of spectral lines, and/or use Stokes line profiles recorded with very high spectral resolution. The diagnostic power of using a Fourier transform spectrometer for polarimetry is shown and some results from I and V spectra are illustrated. The line asymmetries caused by mass motions inside the fluxtubes adds an extra complication to the diagnostic problem, in particular as there are indications that the motions are nonstationary in nature. The temperature structure appears to be a function of fluxtube diameter, as a clear difference between plage and network fluxtubes was revealed. The divergence of the magnetic field with height plays an essential role in the explanation of the Stokes V asymmetries (in combination with the mass motions). A self consistent treatment of the subarcsec field geometry may be required to allow an accurate derivation of the spatially averaged vector magnetic field from spectrally resolved data.

  16. Bacterial Growth in Weak Magnetic Field

    NASA Astrophysics Data System (ADS)

    Masood, Samina

    2015-03-01

    We study the growth of bacteria in a weak magnetic field. Computational analysis of experimental data shows that the growth rate of bacteria is affected by the magnetic field. The effect of magnetic field depends on the strength and type of magnetic field. It also depends on the type of bacteria. We mainly study gram positive and gram negative bacteria of rod type as well as spherical bacteria. Preliminary results show that the weak magnetic field enhances the growth of rod shape gram negative bacteria. Gram positive bacteria can be even killed in the inhomogeneous magnetic field.

  17. Rings

    NASA Astrophysics Data System (ADS)

    Elliot, James; Kerr, Richard

    1987-04-01

    Rings recounts one of the most fascinating stories to emerge from our recent exploration of the solar system. In the past decade scientists have learned more about this beautiful astronomical phenomenon than was ever known before. James Elliot played a leading role in the scientific group that discovered the rings of Uranus, and Richard Kerr has covered Voyager's encounters with Jupiter, Saturn, and Uranus for Science magazine. Together they capture the excitement of the new discoveries - the first since Galileo observed Saturn's rings in 1610 - while showing the central role serendipity can play in scientific progress. James Elliot is Professor of Astronomy and Physics at MIT and Director of the George R. Wallace, Jr., Astrophysical Observatory. Richard Kerr is a senior writer on the research news staff of Science magazine. Copies of the tape that recorded the discovery of the Uranian rings are available from The MIT Press.

  18. Explaining Mercury's peculiar magnetic field

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  19. Field errors in superconducting magnets

    SciTech Connect

    Barton, M.Q.

    1982-01-01

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

  20. Magnetic fields in irregular galaxies

    NASA Astrophysics Data System (ADS)

    Chyzy, Krzysztof T.

    Radio data of large irregular galaxies reveal some extended synchrotron emission with a substantial degree of polarization. In the case of NGC 4449 strong galaxy-scale regular magnetic fields were found, in spite of the lack of ordered rotation required for the conventional dynamo action. The rigidly rotating large irregular NGC 55 shows vertical polarized spurs connected with a network of ionized gas filaments. Small dwarf irregulars show only isolated polarized spots.

  1. High Steady Magnetic Field Processing of Functional Magnetic Materials

    NASA Astrophysics Data System (ADS)

    Rivoirard, Sophie

    2013-07-01

    The materials science community has been enriched for some decades now by the "magneto-science" approach, which consists of applying a magnetic field during material processing. The development of anisotropic properties by applying a steady magnetic field is now a well-established effect in the material processing of magnetic substances, which benefits from the unidirectional and static nature of the field delivered by superconducting magnets. Among other effects, magnetic anisotropy in functional magnetic materials, which arises from the alignment of magnetic moments under external field, can be developed at various structural scales. Magnetic ordering, magnetic patterning, and texturation are at the origin of this anisotropy development. Texture is developed in materials from magnetic orientation due to magnetic forces and torques or from stored energy. In metals and alloys, for instance, this effect can occur either in their liquid state or during solid-state thermomagnetic treatments and can thus impact significantly the material functional magnetic properties. Today's improved superconducting magnet technology allows higher field intensities to be delivered more easily (1 T up to several tens of Teslas) and enables researchers to gather evidence on magnetic field effects that were formerly thought to be negligible. The magneto-thermodynamic effect is one of them and involves the magnetization energy as an additional parameter to tailor microstructures. Control of functional properties can thus result from magnetic monitoring of the phase transformation, and kinetics can be impacted by the magnetic energy contribution.

  2. Performance analysis of a brushless dc motor due to magnetization distribution in a continuous ring magnet

    NASA Astrophysics Data System (ADS)

    Hur, Jin; Jung, In-Soung; Sung, Ha-Gyeong; Park, Soon-Sup

    2003-05-01

    This paper represents the force performance of a brushless dc motor with a continuous ring-type permanent magnet (PM), considering its magnetization patterns: trapezoidal, trapezoidal with dead zone, and unbalanced trapezoidal magnetization with dead zone. The radial force density in PM motor causes vibration, because vibration is induced the traveling force from the rotating PM acting on the stator. Magnetization distribution of the PM as well as the shape of the teeth determines the distribution of force density. In particular, the distribution has a three-dimensional (3-D) pattern because of overhang, that is, it is not uniform in axial direction. Thus, the analysis of radial force density required dynamic analysis considering the 3-D shape of the teeth and overhang. The results show that the force density as a source of vibration varies considerably depending on the overhang and magnetization distribution patterns. In addition, the validity of the developed method, coupled 3-D equivalent magnetic circuit network method, with driving circuit and motion equation, is confirmed by comparison of conventional method using 3D finite element method.

  3. Dynamic domain wall chirality rectification by rotating magnetic fields

    NASA Astrophysics Data System (ADS)

    Bisig, Andre; Mawass, Mohamad-Assaad; Stärk, Martin; Moutafis, Christoforos; Rhensius, Jan; Heidler, Jakoba; Gliga, Sebastian; Weigand, Markus; Tyliszczak, Tolek; Van Waeyenberge, Bartel; Stoll, Hermann; Schütz, Gisela; Kläui, Mathias

    2015-03-01

    We report on the observation of magnetic vortex domain wall chirality reversal in ferromagnetic rings that is controlled by the sense of rotation of a magnetic field. We use time-resolved X-ray microscopy to dynamically image the chirality-switching process and perform micromagnetic simulations to deduce the switching details from time-resolved snapshots. We find experimentally that the switching occurs within less than 4 ns and is observed in all samples with ring widths ranging from 0.5 μm to 2 μm, ring diameters between 2 μm and 5 μm, and a thickness of 30 nm, where a vortex domain wall is present in the magnetic onion state of the ring. From the magnetic contrast in the time-resolved images, we can identify effects of thermal activation, which plays a role for the switching process. Moreover, we find that the process is highly reproducible so that the domain wall chirality can be set with high fidelity.

  4. Neutron Interference in the Gravitational Field of a Ring Laser

    NASA Astrophysics Data System (ADS)

    Fischetti, Robert

    2013-04-01

    A number of analyses of neutron interference effects due to various metric perturbations have been found in the literature [1,2]. However, the approach of each author depends on a specific metric. I will present a new general technique giving the Foldy-Wouthuysen transformed Hamiltonian for a Dirac particle in the most general linearized space-time metric. I will then apply this new technique to calculate the phase shift on a neutron beam interferometer due to the gravitational field of a ring laser [3].[4pt] [1] D. M Greenberger and A. W. Overhauser, Rev. Mod. Phys. 51, 43--78 (1979).[0pt] [2] F. W. Hehl and W. T. Ni, Phys. Rev. D, vol 42, no. 6, pp. 2045-2048, 1990.[0pt] [3] R. L. Mallett, Phys. Lett. A 269, 214 (2000).

  5. Measurements of Solar Vector Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J. (Editor)

    1985-01-01

    Various aspects of the measurement of solar magnetic fields are presented. The four major subdivisions of the study are: (1) theoretical understanding of solar vector magnetic fields; (3) techniques for interpretation of observational data; and (4) techniques for data display.

  6. Anisotropic Magnetism in Field-Structured Composites

    SciTech Connect

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

    1999-06-24

    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.

  7. Variability in Martian Magnetic Field Topology

    NASA Astrophysics Data System (ADS)

    Brain, D. A.; Halekas, J. S.; Eastwood, J. P.; Ulusen, D.; Lillis, R. J.

    2014-07-01

    We have determined the locations of open and closed magnetic field lines at Mars as a function of four different controlling influences: solar wind magnetic field direction, solar wind pressure, martian season, and solar EUV flux.

  8. Magnetic holes in the solar wind. [(interplanetary magnetic fields)

    NASA Technical Reports Server (NTRS)

    Turner, J. M.; Burlaga, L. F.; Ness, N. F.; Lemaire, J. F.

    1976-01-01

    An analysis is presented of high resolution interplanetary magnetic field measurements from the magnetometer on Explorer 43 which showed that low magnetic field intensities in the solar wind at 1 AU occur as distinct depressions or 'holes'. These magnetic holes are new kinetic-scale phenomena, having a characteristic dimension on the order of 20,000 km. They occurred at a rate of 1.5/day in the 18-day time span (March 18 to April 6, 1971) that was analyzed. Most of the magnetic holes are characterized by both a depression in the absolute value of the magnetic field, and a change in the magnetic field direction; some of these are possibly the result of magnetic merging. However, in other cases the magnetic field direction does not change; such holes are not due to magnetic merging, but might be a diamagnetic effect due to localized plasma inhomogeneities.

  9. Performance of the cold cathode gauges in a high and misaligned magnetic field

    SciTech Connect

    Hseuh, H.C.; Jiang, W.S.; Mapes, M. )

    1994-07-01

    Cold cathode gauge tubes without their permanent magnets will be used to monitor the vacuum systems of a muon storage ring, presently under construction at Brookhaven. The fringe field of the storage ring's superconducting magnet will be used to sustain the gauge discharge. Three commercial cold cathode gauges, a Penning type, a grounded Penning and an inverted magnetron, have been studied for their suitability under this high and misaligned magnetic field. Using an electromagnet, the discharge intensities of these gauges have been measured at pressures from 10[sup [minus]8] to 10[sup [minus]5] Torr, magnetic fields from a few hundred Gauss to 15 kG, and alignment angles from 0[degree] to 50[degree]. The discharge intensity of the Penning gauge increases with increasing magnetic field misalignment and decreases gradually with increasing pressure and magnetic field. At small misalignment, the discharge intensity of the grounded Penning decreases with increasing magnetic field, and if the misalignment is large, it drops off abruptly at high magnetic field. The discharge intensity of the grounded Penning peaks around 1[times]10[sup [minus]6] Torr if the magnetic field is low; and at a high magnetic field, it drops off gradually with increasing pressure. At lower pressures, the discharge intensity of the inverted magnetron gauge remains fairly constant with an increasing magnetic field, but decreases with increasing magnetic field at higher pressure ranges. Its discharge intensity also decreases rapidly with increasing misalignment.

  10. Rotating copper plasmoid in external magnetic field

    SciTech Connect

    Pandey, Pramod K.; Thareja, Raj K.

    2013-02-15

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

  11. Penetration of plasma across a magnetic field

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

    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.

  12. Field configuration of beam excited modes in the Advanced Photon Source (APS) storage ring waveguides

    NASA Astrophysics Data System (ADS)

    Brauer, S. O.; Kustom, R. L.; Uslenghi, P. L. E.

    Argonne National Laboratory (ANL) is in the process of building a positron accelerator and storage ring, the Advanced Photo source (APS). The RF system for the APS storage ring uses 16 cylindrical TM010-like, reentrant cavities operating at 351.93 MHz to resupply energy lost by the beam due to synchrotron radiation. The stored beam will have approximately 60 bunches, 5 mA per bunch, for a total beam current of 300 mA. Calculations of the threshold current for coupled-bench instabilities in the storage ring have indicated that several beam-induced higher-order modes (HOM's) will reduce the threshold for beam stability and therefore should be damped. Previous data taken using a pillbox cavity showed that it is likely that some of these modes couple, through the coupling loop, from the storage ring cavity into the waveguide. This study investigates the electric and magnetic field configuration of each HOM present in the waveguide. A pillbox and a prototype storage ring cavity, together with various WR2300 waveguide components, are used to obtain the measurements needed for the determination of the mode configuration of the HOM's at the frequencies of interest. To avoid the development of beam instabilities due to the existence of these HOM's in the RF cavity, damping of the modes will be required. The HOM's present in the RF cavity coupling into the loop coupler and traveling through the coupler into the waveguide, may allow damping of some of the HOM's by insertion of dampers into the waveguide adjacent to each cavity.

  13. Superposition of DC magnetic fields by cascading multiple magnets in magnetic loops

    NASA Astrophysics Data System (ADS)

    Sun, Fei; He, Sailing

    2015-09-01

    A novel method that can effectively collect the DC magnetic field produced by multiple separated magnets is proposed. With the proposed idea of a magnetic loop, the DC magnetic field produced by these separated magnets can be effectively superimposed together. The separated magnets can be cascaded in series or in parallel. A novel nested magnetic loop is also proposed to achieve a higher DC magnetic field in the common air region without increasing the DC magnetic field in each magnetic loop. The magnetic loop can be made by a magnetic hose, which is designed by transformation optics and can be realized by the combination of super-conductors and ferromagnetic materials.

  14. Magnetic field gradient measurement on magnetic cards using magnetic force microscopy

    NASA Astrophysics Data System (ADS)

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

    2002-05-01

    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.

  15. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings

    NASA Astrophysics Data System (ADS)

    Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew; Krishnan, Kannan M.

    2014-11-01

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe3O4 nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy.

  16. Interplanetary magnetic field data book

    NASA Technical Reports Server (NTRS)

    King, J. H.

    1975-01-01

    An interplanetary magnetic field (IMF) data set is presented that is uniform with respect to inclusion of cislunar IMF data only, and which has as complete time coverage as presently possible over a full solar cycle. Macroscale phenomena in the interplanetary medium (sector structure, heliolatitude variations, solar cycle variations, etc.) and other phenomena (e.g., ground level cosmic-ray events) for which knowledge of the IMF with hourly resolution is necessary, are discussed. Listings and plots of cislunar hourly averaged IMP parameters over the period November 27, 1963, to May 17, 1974, are presented along with discussion of the mutual consistency of the IMF data used herein. The magnetic tape from which the plots and listings were generated, which is available from the National Space Science Data Center (NSSDC), is also discussed.

  17. The Giotto magnetic field investigation

    NASA Technical Reports Server (NTRS)

    Neubauer, F. M.; Musmann, G.; Acuna, M. H.; Burlaga, L. F.; Ness, N. F.; Mariani, F.; Wallis, M.; Ungstrup, E.; Schmidt, H.

    1983-01-01

    The Giotto spacecraft will carry sensors for investigating the interplanetary magnetic field while en route and the interaction between the solar wind magnetoplasma and Halley's Comet neutral gas outflow during close approach. Giotto will carry an outboard biaxial fluxgate system and inboard electronics. The instrumentation draws 1.2 kW and weighs 1.31 kg. Sampling rates will be 28/sec during close encounter, covering selectable ranges from 16 nT to 65,535 nT. In-flight calibration techniques are under development to ensure magnetic cleanliness will be obtained. Measurements are also planned of the inbound bow shock, the magnetosheath and the cometary ionopause. The data will be collected as close as 1000 km from the comet surface.

  18. Bats respond to very weak magnetic fields.

    PubMed

    Tian, Lan-Xiang; Pan, Yong-Xin; Metzner, Walter; Zhang, Jin-Shuo; Zhang, Bing-Fang

    2015-01-01

    How animals, including mammals, can respond to and utilize the direction and intensity of the Earth's magnetic field for orientation and navigation is contentious. In this study, we experimentally tested whether the Chinese Noctule, Nyctalus plancyi (Vespertilionidae) can sense magnetic field strengths that were even lower than those of the present-day geomagnetic field. Such field strengths occurred during geomagnetic excursions or polarity reversals and thus may have played an important role in the evolution of a magnetic sense. We found that in a present-day local geomagnetic field, the bats showed a clear preference for positioning themselves at the magnetic north. As the field intensity decreased to only 1/5th of the natural intensity (i.e., 10 μT; the lowest field strength tested here), the bats still responded by positioning themselves at the magnetic north. When the field polarity was artificially reversed, the bats still preferred the new magnetic north, even at the lowest field strength tested (10 μT), despite the fact that the artificial field orientation was opposite to the natural geomagnetic field (P<0.05). Hence, N. plancyi is able to detect the direction of a magnetic field even at 1/5th of the present-day field strength. This high sensitivity to magnetic fields may explain how magnetic orientation could have evolved in bats even as the Earth's magnetic field strength varied and the polarity reversed tens of times over the past fifty million years. PMID:25922944

  19. Safety concerns related to magnetic field exposure.

    PubMed

    Silva, Amanda K Andriola; Silva, Erica L; Egito, E Sócrates T; Carriço, Artur S

    2006-11-01

    The recent development of superconducting magnets has resulted in a huge increase in human exposure to very large static magnetic fields of up to several teslas (T). Considering the rapid advances in applications and the great increases in the strength of magnetic fields used, especially in magnetic resonance imaging, safety concerns about magnetic field exposure have become a key issue. This paper points out some of these safety concerns and gives an overview of the findings about this theme, focusing mainly on mechanisms of magnetic field interaction with living organisms and the consequent effects. PMID:17021785

  20. Symmetry restoration at finite temperature with weak magnetic fields

    NASA Astrophysics Data System (ADS)

    Navarro, Jorge; Sánchez, Angel; Tejeda-Yeomans, Maria Elena; Ayala, Alejandro; Piccinelli, Gabriella

    2010-12-01

    We study symmetry restoration at finite temperature in the standard model during the electroweak phase transition in the presence of a weak magnetic field. We compute the finite temperature effective potential up to the contribution of ring diagrams, using the broken phase degrees of freedom, and keep track of the gauge parameter dependence of the results. We show that under these conditions, the phase transition becomes stronger first order.

  1. Interaction between two magnetic dipoles in a uniform magnetic field

    NASA Astrophysics Data System (ADS)

    Ku, J. G.; Liu, X. Y.; Chen, H. H.; Deng, R. D.; Yan, Q. X.

    2016-02-01

    A new formula for the interaction force between two magnetic dipoles in a uniform magnetic field is derived taking their mutual magnetic interaction into consideration and used to simulate their relative motion. Results show that when the angle β between the direction of external magnetic field and the centerline of two magnetic dipoles is 0 ° or 90 °, magnetic dipoles approach each other or move away from each other in a straight line, respectively. And the time required for them to contact each other from the initial position is related to the specific susceptibility and the diameter of magnetic particles, medium viscosity and magnetic field strength. When β is between 0 ° and 90 °, magnetic dipole pair performs approximate elliptical motion, and the motion trajectory is affected by the specific susceptibility, diameter and medium viscosity but not magnetic field strength. However, time required for magnetic dipoles to complete the same motion trajectory is shorter when adopting stronger magnetic field. Moreover, the subsequent motion trajectory of magnetic dipoles is ascertained once the initial position is set in a predetermined motion trajectory. Additionally, magnetic potential energy of magnetic dipole pairs is transformed into kinetic energy and friction energy during the motion.

  2. Magnetic measurements on an in-vacuum undulator for the NSLS x-ray ring

    SciTech Connect

    Rakowsky, G.; Aspenleiter, J.J.; Graves, W.S.

    1997-07-01

    Magnetic measurements have been performed on the In-Vacuum Undulator (IVUN), built jointly by BNL and SPring-8 for the NSLS X-ray Ring. The IVUN magnet has a Halback-type, pure-permanent magnet structure with a period of 11 mm and a minimum gap of 2 mm. Results of magnetic measurements utilizing Hall probe, moving wire and pulsed wire techniques will be presented and compared.

  3. Magnetic field sources and their threat to magnetic media

    NASA Technical Reports Server (NTRS)

    Jewell, Steve

    1993-01-01

    Magnetic storage media (tapes, disks, cards, etc.) may be damaged by external magnetic fields. The potential for such damage has been researched, but no objective standard exists for the protection of such media. This paper summarizes a magnetic storage facility standard, Publication 933, that ensures magnetic protection of data storage media.

  4. Suppression of magnetic relaxation by a transverse alternating magnetic field

    SciTech Connect

    Voloshin, I. F.; Kalinov, A. V.; Fisher, L. M. Yampol'skii, V. A.

    2007-07-15

    The evolution of the spatial distribution of the magnetic induction in a superconductor after the action of the alternating magnetic field perpendicular to the trapped magnetic flux has been analyzed. The observed stabilization of the magnetic induction profile is attributed to the increase in the pinning force, so that the screening current density becomes subcritical. The last statement is corroborated by direct measurements.

  5. Simple method for the generation of multiple homogeneous field volumes inside the bore of superconducting magnets.

    PubMed

    Chou, Ching-Yu; Ferrage, Fabien; Aubert, Guy; Sakellariou, Dimitris

    2015-01-01

    Standard Magnetic Resonance magnets produce a single homogeneous field volume, where the analysis is performed. Nonetheless, several modern applications could benefit from the generation of multiple homogeneous field volumes along the axis and inside the bore of the magnet. In this communication, we propose a straightforward method using a combination of ring structures of permanent magnets in order to cancel the gradient of the stray field in a series of distinct volumes. These concepts were demonstrated numerically on an experimentally measured magnetic field profile. We discuss advantages and limitations of our method and present the key steps required for an experimental validation. PMID:26182891

  6. Nuclear magnetic resonance apparatus for pulsed high magnetic fields.

    PubMed

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

    2012-08-01

    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. PMID:22938280

  7. Ring formation in the quasi-two-dimensional system of the patchy magnetic spheres

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng-yu; Jian, Xing-liang; Lu, Wei

    2016-04-01

    Fabricating new functional materials has always been at the center of colloidal science, and how to form circular rings is a meaningful challenge due to their special electronic, magnetic and optical properties. Magnetic colloidal spheres can self-assemble into rings, but these rings have an uncontrollable length and shape and also have to coexist with chains and defected clusters. To make the most of magnetic spheres being able to self-assemble into rings, a patch is added to the surface of the sphere to form a chiral link between particles. The structural transition in the system of patchy magnetic spheres is studied using the Monte Carlo simulation. When the patch angle is in the interval {{60}{^\\circ}} to {{75}{^\\circ}} , rings become the dominant structure if the strength of patchy interaction exceeds a particular threshold and the shape of these rings is close to the circle. With an increase in the patch angle, the threshold of patchy interaction decreases and the average length of the circular ring increases approximately from 5 to 8.5.

  8. Ring formation in the quasi-two-dimensional system of the patchy magnetic spheres.

    PubMed

    Zhang, Cheng-Yu; Jian, Xing-Liang; Lu, Wei

    2016-04-13

    Fabricating new functional materials has always been at the center of colloidal science, and how to form circular rings is a meaningful challenge due to their special electronic, magnetic and optical properties. Magnetic colloidal spheres can self-assemble into rings, but these rings have an uncontrollable length and shape and also have to coexist with chains and defected clusters. To make the most of magnetic spheres being able to self-assemble into rings, a patch is added to the surface of the sphere to form a chiral link between particles. The structural transition in the system of patchy magnetic spheres is studied using the Monte Carlo simulation. When the patch angle is in the interval [Formula: see text] to [Formula: see text], rings become the dominant structure if the strength of patchy interaction exceeds a particular threshold and the shape of these rings is close to the circle. With an increase in the patch angle, the threshold of patchy interaction decreases and the average length of the circular ring increases approximately from 5 to 8.5. PMID:26965459

  9. The Galactic Magnetic Field as Viewed from the VLA

    NASA Astrophysics Data System (ADS)

    van Eck, Cameron; Brown, Jo-Anne

    2009-05-01

    Interstellar magnetic fields play critical roles in many astrophysical processes. Yet despite their importance, our knowledge about magnetic fields in our Galaxy remains limited. For the field within the Milky Way much of what we do know comes from radio astronomy, through observations of polarization and Faraday rotation measures (RMs) of extragalactic sources and pulsars. A high angular density of RM measurements in several critical areas of the Galaxy is needed to clarify the Galactic magnetic field structure. Understanding the overall structure of the magnetic field will subsequently help us determine the origin and evolution of the field. In an effort to determine the overall structure of the field, Sun et al. (2008) produced 3 models of the Galactic magnetic field based on RM measurements available at the time. These models made distinct predictions for RMs in a region of the inner Galaxy at low Galactic latitude. Using observations made with the Very Large Array (VLA), we have determined RMs for sources in this critical region. In this talk we will present the results of our study and show how the RMs strongly support the ASS+RING model.

  10. Permanent Magnet Ecr Plasma Source With Magnetic Field Optimization

    DOEpatents

    Doughty, Frank C.; Spencer, John E.

    2000-12-19

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

  11. Chiral plasmons without magnetic field.

    PubMed

    Song, Justin C W; Rudner, Mark S

    2016-04-26

    Plasmons, the collective oscillations of interacting electrons, possess emergent properties that dramatically alter the optical response of metals. We predict the existence of a new class of plasmons-chiral Berry plasmons (CBPs)-for a wide range of 2D metallic systems including gapped Dirac materials. As we show, in these materials the interplay between Berry curvature and electron-electron interactions yields chiral plasmonic modes at zero magnetic field. The CBP modes are confined to system boundaries, even in the absence of topological edge states, with chirality manifested in split energy dispersions for oppositely directed plasmon waves. We unveil a rich CBP phenomenology and propose setups for realizing them, including in anomalous Hall metals and optically pumped 2D Dirac materials. Realization of CBPs will offer a powerful paradigm for magnetic field-free, subwavelength optical nonreciprocity, in the mid-IR to terahertz range, with tunable splittings as large as tens of THz, as well as sensitive all-optical diagnostics of topological bands. PMID:27071090

  12. Magnetic Fields in Irregular Galaxies: NGC 4214

    NASA Astrophysics Data System (ADS)

    Kepley, Amanda A.; Wilcots, E. M.; Robishaw, T.; Heiles, C.; Zweibel, E.

    2006-12-01

    Magnetic fields are an important component of the interstellar medium of galaxies. They provide support, transfer energy from supernovae, provide a possible heating mechanism, and channel gas flows (Beck 2004). Despite the importance of magnetic fields in the ISM, it is not well known what generates and sustains galactic magnetic fields or how magnetic fields, gas, and stars interact in galaxies. The magnetic fields may be especially important in low-mass galaxies like irregulars where the magnetic pressure may be great enough for the field to be dynamically important. However, only four irregular galaxies besides the LMC and the SMC have observed magnetic field structures. The goal of our project is to significantly increase the number of irregular galaxies with observed magnetic field structure. Here we present preliminary results for one of the galaxies in our sample: NGC 4214. Using the VLA and the GBT, we have obtained 3cm, 6cm, and 20cm radio continuum polarization observations of this well-studied galaxy. Our observations allow us to investigate the effects of NGC 4214's high star formation rate, slow rotation rate, and weak bar on the structure of its magnetic field. We find that NGC 4214's magnetic field has an S-shaped structure, with the central field following the bar and the outer edges curving to follow the shape of the arms. The mechanism for generating these fields is still uncertain. A. Kepley is funded by an NSF Graduate Research Fellowship.

  13. Magnetic field waves at Uranus

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  14. Magnetic fields from the electroweak phase transition

    SciTech Connect

    Tornkvist, O.

    1998-02-01

    I review some of the mechanisms through which primordial magnetic fields may be created in the electroweak phase transition. I show that no magnetic fields are produced initially from two-bubble collisions in a first-order transition. The initial field produced in a three-bubble collision is computed. The evolution of fields at later times is discussed.

  15. Magnetic field effects on microwave absorbing materials

    NASA Technical Reports Server (NTRS)

    Goldberg, Ira; Hollingsworth, Charles S.; Mckinney, Ted M.

    1991-01-01

    The objective of this program was to gather information to formulate a microwave absorber that can work in the presence of strong constant direct current (DC) magnetic fields. The program was conducted in four steps. The first step was to investigate the electrical and magnetic properties of magnetic and ferrite microwave absorbers in the presence of strong magnetic fields. This included both experimental measurements and a literature survey of properties that may be applicable to finding an appropriate absorbing material. The second step was to identify those material properties that will produce desirable absorptive properties in the presence of intense magnetic fields and determine the range of magnetic field in which the absorbers remain effective. The third step was to establish ferrite absorber designs that will produce low reflection and adequate absorption in the presence of intense inhomogeneous static magnetic fields. The fourth and final step was to prepare and test samples of such magnetic microwave absorbers if such designs seem practical.

  16. ESA's Magnetic Field Mission Swarm

    NASA Astrophysics Data System (ADS)

    Haagmans, R.; Kern, M.; Plank, G.; Menard, Y.

    2008-12-01

    Swarm is the fifth Earth Explorer mission in ESA's Living Planet Programme. The objective of the Swarm mission is to provide the best ever survey of the geomagnetic field and its temporal evolution. The Mission shall deliver data that allow access to new insights into the Earth system by improving our understanding of the Earth's interior and climate. The mission is nominally scheduled for launch in 2010. After release from a single launcher, a side-by-side flying slowly decaying lower pair of satellites will be released at an initial altitude of about 490 km together with a third satellite that will be lifted to 530 km to complete the Swarm constellation. High-precision and high-resolution measurements of the strength, direction and variation of the magnetic field, complemented by precise navigation, accelerometer and electric field measurements, will provide the observations that are required to separate and model various sources of the geomagnetic field. At present the project is in the development phase. The current project status, planned products and performances, and on-going scientific studies will be given special attention during the presentation. There will also be outlook to the next planned Swarm workshop.

  17. Magnetic switching in ultrashort field pulses (abstract)

    NASA Astrophysics Data System (ADS)

    Back, C. H.; Weller, D.; Heidmann, J.; Mauri, D.; Garwin, E. L.; Siegmann, H. C.

    1997-04-01

    The Ginzburg-Landau-Lifshitz (GLL) equation, which describes the time dependence of spin precesssion in an external magnetic field1 relates the minimal field required to reverse the magnetization at fixed pulse length to the anisotropy field of the sample.23 We have systematically varied this parameter between 1.3 and about 5.0 T in a series of perpendicularly magnetized Co/Pt multilayer films and studied the magnetization reversal in picosecond in plane field pulses. Such pulses of several Tesla field strength and ultrashort duration were obtained in the final focus test beam section of the Stanford Linear Accelerator Center. The resulting magnetization pattern, which is reminiscent of the field during exposure, is subsequently analyzed with Kerr microscopy2 (see Fig. 1). As a prominent feature, we observe a beam field related switching radius from up to down magnetization which we compare to the theoretically expected field within the GLL formalism.

  18. Deformation of Water by a Magnetic Field

    ERIC Educational Resources Information Center

    Chen, Zijun; Dahlberg, E. Dan

    2011-01-01

    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…

  19. Exploring Magnetic Fields with a Compass

    ERIC Educational Resources Information Center

    Lunk, Brandon; Beichner, Robert

    2011-01-01

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

  20. Exploring Magnetic Fields with a Compass

    ERIC Educational Resources Information Center

    Lunk, Brandon; Beichner, Robert

    2011-01-01

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

  1. Deformation of Water by a Magnetic Field

    ERIC Educational Resources Information Center

    Chen, Zijun; Dahlberg, E. Dan

    2011-01-01

    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

  2. [Analysis of peculiarities of magnetic field effect].

    PubMed

    Macheret, Ie L; Murashko, N K

    2003-01-01

    In the article is analyzed the influence of a magnetic field of the Earth on human, state of his health and necessity of magnetic diagnostics. The magnetic fields is an effective preventive and tentative method in case of an early development of diseases. PMID:14723128

  3. Magnetic field effect on charged Brownian swimmers

    NASA Astrophysics Data System (ADS)

    Sandoval, M.; Velasco, R. M.; Jiménez-Aquino, J. I.

    2016-01-01

    We calculate the effective diffusion of a spherical self-propelled charged particle swimming at low Reynolds number, and subject to a time-dependent magnetic field and thermal agitation. We find that the presence of an external magnetic field may reduce or enhance (depending on the type of swimming and magnetic field applied) the swimmer's effective diffusion, hence we get another possible strategy to control its displacement. For swimmers performing reciprocal motion, and under an oscillating time-dependent magnetic field, mechanical resonance appears when the swimmer and magnetic frequencies coincide, thus enhancing the particle's effective diffusion. Our analytical results are compared with Brownian Dynamics simulations and we obtain excellent agreement.

  4. Baryon onset in a magnetic field

    NASA Astrophysics Data System (ADS)

    Haber, Alexander; Preis, Florian; Schmitt, Andreas

    2016-01-01

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

  5. Influence of segmentation of ring-shaped NdFeB magnets with parallel magnetization on cylindrical actuators.

    PubMed

    Eckert, Paulo Roberto; Goltz, Evandro Claiton; Flores Filho, Aly Ferreira

    2014-01-01

    This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines. PMID:25051032

  6. Influence of Segmentation of Ring-Shaped NdFeB Magnets with Parallel Magnetization on Cylindrical Actuators

    PubMed Central

    Eckert, Paulo Roberto; Goltz, Evandro Claiton; Filho, Aly Ferreira Flores

    2014-01-01

    This work analyses the effects of segmentation followed by parallel magnetization of ring-shaped NdFeB permanent magnets used in slotless cylindrical linear actuators. The main purpose of the work is to evaluate the effects of that segmentation on the performance of the actuator and to present a general overview of the influence of parallel magnetization by varying the number of segments and comparing the results with ideal radially magnetized rings. The analysis is first performed by modelling mathematically the radial and circumferential components of magnetization for both radial and parallel magnetizations, followed by an analysis carried out by means of the 3D finite element method. Results obtained from the models are validated by measuring radial and tangential components of magnetic flux distribution in the air gap on a prototype which employs magnet rings with eight segments each with parallel magnetization. The axial force produced by the actuator was also measured and compared with the results obtained from numerical models. Although this analysis focused on a specific topology of cylindrical actuator, the observed effects on the topology could be extended to others in which surface-mounted permanent magnets are employed, including rotating electrical machines. PMID:25051032

  7. Quantum ring solitons and nonlocal effects in plasma wake field excitations

    SciTech Connect

    Fedele, R.; Tanjia, F.; De Nicola, S.; Jovanovic, D.; Shukla, P. K.

    2012-10-15

    A theoretical investigation of the quantum transverse beam motion for a cold relativistic charged particle beam travelling in a cold, collisionless, strongly magnetized plasma is carried out. This is done by taking into account both the individual quantum nature of the beam particles (single-particle uncertainty relations and spin) and the self consistent interaction generated by the plasma wake field excitation. By adopting a fluid model of a strongly magnetized plasma, the analysis is carried out in the overdense regime (dilute beams) and in the long beam limit. It is shown that the quantum description of the collective transverse beam dynamics is provided by a pair of coupled nonlinear governing equations. It comprises a Poisson-like equation for the plasma wake potential (driven by the beam density) and a 2D spinorial Schroedinger equation for the wave function, whose squared modulus is proportional to the beam density, that is obtained in the Hartree's mean field approximation, after disregarding the exchange interactions. The analysis of this pair of equations, which in general exhibits a strong nonlocal character, is carried out analytically as well as numerically in both the linear and the nonlinear regimes, showing the existence of the quantum beam vortices in the form of Laguerre-Gauss modes and ring envelope solitons, respectively. In particular, when the relation between the plasma wake field response and the beam probability density is strictly local, the pair of the governing equations is reduced to the 2D Gross-Pitaevskii equation that allows one to establish the conditions for the self focusing and collapse. These conditions include the quantum nature of the beam particles. Finally, when the relation between the plasma wake field response and the beam probability density is moderately nonlocal, the above pair of equations permits to follow the spatio-temporal evolution of a quantum ring envelope soliton. Such a structure exhibits small or violent breathing, but it remains very stable for long time.

  8. Quantum ring solitons and nonlocal effects in plasma wake field excitations

    NASA Astrophysics Data System (ADS)

    Fedele, R.; Tanjia, F.; De Nicola, S.; Jovanović, D.; Shukla, P. K.

    2012-10-01

    A theoretical investigation of the quantum transverse beam motion for a cold relativistic charged particle beam travelling in a cold, collisionless, strongly magnetized plasma is carried out. This is done by taking into account both the individual quantum nature of the beam particles (single-particle uncertainty relations and spin) and the self consistent interaction generated by the plasma wake field excitation. By adopting a fluid model of a strongly magnetized plasma, the analysis is carried out in the overdense regime (dilute beams) and in the long beam limit. It is shown that the quantum description of the collective transverse beam dynamics is provided by a pair of coupled nonlinear governing equations. It comprises a Poisson-like equation for the plasma wake potential (driven by the beam density) and a 2D spinorial Schrödinger equation for the wave function, whose squared modulus is proportional to the beam density, that is obtained in the Hartree's mean field approximation, after disregarding the exchange interactions. The analysis of this pair of equations, which in general exhibits a strong nonlocal character, is carried out analytically as well as numerically in both the linear and the nonlinear regimes, showing the existence of the quantum beam vortices in the form of Laguerre-Gauss modes and ring envelope solitons, respectively. In particular, when the relation between the plasma wake field response and the beam probability density is strictly local, the pair of the governing equations is reduced to the 2D Gross-Pitaevskii equation that allows one to establish the conditions for the self focusing and collapse. These conditions include the quantum nature of the beam particles. Finally, when the relation between the plasma wake field response and the beam probability density is moderately nonlocal, the above pair of equations permits to follow the spatio-temporal evolution of a quantum ring envelope soliton. Such a structure exhibits small or violent breathing, but it remains very stable for long time.

  9. Analysis of magnetic field levels at KSC

    NASA Technical Reports Server (NTRS)

    Christodoulou, Christos G.

    1994-01-01

    The scope of this work is to evaluate the magnetic field levels of distribution systems and other equipment at Kennedy Space Center (KSC). Magnetic fields levels in several operational areas and various facilities are investigated. Three dimensional mappings and contour are provided along with the measured data. Furthermore, the portion of magnetic fields generated by the 60 Hz fundamental frequency and the portion generated by harmonics are examined. Finally, possible mitigation techniques for attenuating fields from electric panels are discussed.

  10. Planetary Rings

    NASA Astrophysics Data System (ADS)

    Tiscareno, Matthew S.

    Planetary rings are the only nearby astrophysical disks and the only disks that have been investigated by spacecraft (especially the Cassini spacecraft orbiting Saturn). Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 10- 7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close range and in real time in planetary rings.We review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We then review planetary rings by type. The A, B, and C rings of Saturn, plus the Cassini Division, comprise our solar system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are found both at Uranus (where they comprise the main rings entirely) and at Saturn (where they are embedded in the broad disk) and are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally confined arcs at Neptune, Saturn, and Jupiter. Finally, every known ring system includes a substantial component of diffuse dusty rings.Planetary rings have shown themselves to be useful as detectors of planetary processes around them, including the planetary magnetic field and interplanetary impactors as well as the gravity of nearby perturbing moons. Experimental rings science has made great progress in recent decades, especially numerical simulations of self-gravity wakes and other processes but also laboratory investigations of coefficient of restitution and spectroscopic ground truth. The age of self-sustained ring systems is a matter of debate; formation scenarios are most plausible in the context of the early solar system, while signs of youthfulness indicate at least that rings have never been static phenomena.

  11. Destruction of a Magnetic Mirror-Trapped Hot Electron Ring by an Alfv'en Wave

    NASA Astrophysics Data System (ADS)

    Wang, Yuhou; Gekelman, Walter; Pribyl, Patrick; Papadopoulos, Konstantinos

    2012-10-01

    Highly energetic electrons produced naturally or artificially can be trapped in the earth's radiation belts for months, posing a danger to valuable space satellites. Concepts that can lead to mitigation of the radiation belts have drawn a great deal of interest. In this work, we demonstrated that a shear Alfv'en wave can effectively de-trap energetic electrons confined by a magnetic mirror field.footnotetextY. Wang, W. Gekelman, P. Pribyl, and K. Papadopoulos, Phys. Rev. Lett. 108, 105002 (2012). The experiment is performed in a quiescent afterglow plasma in the Large Plasma Device (LaPD) at UCLA (ne=0.1-1x10^12/cm^3, Te=0.5eV, B0=400-1600G, L=18m, and diameter=0.6m). A hot electron ring (along with hard x-rays of energies up to 3 MeV) is generated by 2nd harmonic ECRH (P=25kW, τpulse=20-50ms, f=2.45GHz) and is trapped in a magnetic mirror field (L=3m, Rmirror=1.1-4). A shear Alfv'en wave (f 0.5fci, Bwave/B0 0.1% ) is launched with a rotating magnetic field antenna with arbitrary polarity. The circularly polarized Alfv'en wave is observed to dramatically scatter the trapped fast electrons out of the mirror within as little as 10 wave cycles. A collimated detector outside the vacuum vessel detects X-rays of E>100 keV. X-ray images are reconstructed from more than 1000 chord projections at each axial location by computed tomography. The de-trapped electrons are observed outside the mirror field region.

  12. Magnetic field topology of the RS CVn star II Pegasi

    NASA Astrophysics Data System (ADS)

    Kochukhov, O.; Mantere, M. J.; Hackman, T.; Ilyin, I.

    2013-02-01

    Context. The dynamo processes in cool active stars generate complex magnetic fields responsible for prominent surface stellar activity and variability at different time scales. For a small number of cool stars magnetic field topologies were reconstructed from the time series of spectropolarimetric observations using the Zeeman Doppler imaging (ZDI) method, often yielding surprising and controversial results. Aims: In this study we follow a long-term evolution of the magnetic field topology of the RS CVn binary star II Peg using a more self-consistent and physically more meaningful modelling approach compared to previous ZDI studies. Methods: We collected high-resolution circular polarisation observations of II Peg using the SOFIN spectropolarimeter at the Nordic Optical Telescope. These data cover 12 epochs spread over 7 years, comprising one of the most comprehensive spectropolarimetric data sets acquired for a cool active star. A multi-line diagnostic technique in combination with a new ZDI code is applied to interpret these observations. Results: We have succeeded in detecting clear magnetic field signatures in average Stokes V profiles for all 12 data sets. These profiles typically have complex shapes and amplitudes of ~10-3 of the unpolarised continuum, corresponding to mean longitudinal fields of 50-100 G. Magnetic inversions using these data reveals evolving magnetic fields with typical local strengths of 0.5-1.0 kG and complex topologies. Despite using a self-consistent magnetic and temperature mapping technique, we do not find a clear correlation between magnetic and temperature features in the ZDI maps. Neither do we confirm the presence of persistent azimuthal field rings found in other RS CVn stars. Reconstruction of the magnetic field topology of II Peg reveals significant evolution of both the surface magnetic field structure and the extended magnetospheric field geometry on the time scale covered by our observations. From 2004 to 2010 the total field energy drastically declined and the field became less axisymmetric. This also coincided with the transition from predominantly poloidal to mainly toroidal field topology. Conclusions: A qualitative comparison of the ZDI maps of II Peg with the prediction of dynamo theory suggests that the magnetic field in this star is produced mainly by the turbulent ?2 dynamo rather than the solar ?? dynamo. Our results do not show a clear active longitude system, nor is there evidence of the presence of an azimuthal dynamo wave. Based on observations obtained with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, at the Spanish Observatorio del Roque de los Muchachos of the Instituto Astrofisica de Canarias.

  13. Magnetometer measures orthogonal components of magnetic fields

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Driven magnetometer accurately measures the components of a low strength magnetic field in each of three mutually perpendicular directions. To accomplish this, it employs the principle of magnetic resonance in optically pumped rubidium vapor.

  14. Bipolar pulse field for magnetic refrigeration

    DOEpatents

    Lubell, Martin S.

    1994-01-01

    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.

  15. Bipolar pulse field for magnetic refrigeration

    DOEpatents

    Lubell, M.S.

    1994-10-25

    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.

  16. Application peculiarities of magnetic materials for protection from magnetic fields

    NASA Astrophysics Data System (ADS)

    Wai, P.; Dmitrenko, V.; Grabchikov, S.; Vlasik, K.; Novikov, A.; Petrenko, D.; Trukhanov, V.; Ulin, S.; Uteshev, Z.; Chernysheva, V.; Shustov, A.

    2016-02-01

    In different materials for magnetic shields, the maximum permeability is achieved for different values of the magnetic field. This determines the choice of material. So for protection from magnetic fields strength of 10 - 150 A/m it is advisable to apply the amorphous ribbon 84KXCP. For stronger fields (more than 400 A/m) it is recommended to use MFS based on Ni20Fe80. Use of these materials allows creating an effective shield working in a wide range of magnetic field strengths.

  17. Onset of necking in electro-magnetically formed rings

    NASA Astrophysics Data System (ADS)

    Triantafyllidis, Nicolas; Waldenmyer, Joshua R.

    2004-09-01

    The electromagnetic forming (EMF) process is an attractive manufacturing technique, which uses electromagnetic (Lorentz) body forces to fabricate metallic parts. One of the many advantages of EMF is the considerable ductility increase observed in several metals, with aluminum featuring prominently among them. The quantitative explanation of this phenomenon is the primary motivation of this work. To study the ductility increase due to EMF, an aluminum ring is placed outside a fixed coil, which is connected to a capacitor. Upon the capacitor's discharge, the time varying current in the coil induces a larger current in the ring specimen and the resulting Lorentz forces make it expand. The coupled coil-ring electromagnetic and thermomechanical problem is solved, using an experimentally obtained constitutive model for a particular aluminum alloy. Our results show that for realistic imperfections, the EMF ring starts necking at strains about six times larger than its static counterpart, as observed experimentally. This study establishes the importance of solving the fully coupled electromagnetic and thermomechanical problem and provides insight on how different constitutive parameters influence ductility in an EMF process.

  18. Magnetic Field Topology of Sigmoids

    NASA Astrophysics Data System (ADS)

    Son, J. H.; Canfield, R. C.; Acton, L. W.

    2004-12-01

    Sigmoids are studied due to their eruptive nature, which affects the Earth and the space atmosphere. The shape of the sigmoid (S-shaped or inverse S-shaped) is an indicator of eruption. The origin of this shape has been the topic of many research papers. One such paper by Fan and Gibson, The Emergence of a Twisted Magnetic Flux Tube Into a Preexisting Coronal Arcade, appeared in 2003. Fan and Gibson argue that a sigmoid with left-handed twist has left-handed writhe, which gives the sigmoid its S-shape and right-handed twist the inverse S-shape. Our study determined that there is no correlation between a sigmoid's handedness and shape as claimed in the paper by Fan and Gibson. Doing a statistical study observing the topology of the sigmoid using the data from Yohkoh Soft X-ray Telescope, we classified each sigmoid by its shape, twist, and magnetic field lines. We found that 23% of our data was right-handed and S-shaped, 33% was left-handed and S-shaped, 22% was right-handed and inverse S-shaped, and 22% was left-handed and inverse-S shaped. Thus, we found no systematic relationship between the handedness and shape of the sigmoid -- in disagreement with Fan and Gibson.

  19. Magnetic field waves at Uranus

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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 (SwRI), and Goddard Space Flight Center (GSFC). In addition, other collaborations have been formed with investigators granted UDAP funds for similar studies and with investigators affiliated with other Voyager experiments. These investigations and the corresponding collaborations are included in the report. The proposed effort as originally conceived included an examination of waves downstream from the shock within the magnetosheath. However, the observations of unexpected complexity and diversity within the upstream region have necessitated that we confine our efforts to those observations recorded upstream of the bow shock on the inbound and outbound legs of the encounter by the Voyager 2 spacecraft.

  20. The CASSIOPE/e-POP Magnetic Field Instrument (MGF)

    NASA Astrophysics Data System (ADS)

    Wallis, D. D.; Miles, D. M.; Narod, B. B.; Bennest, J. R.; Murphy, K. R.; Mann, I. R.; Yau, A. W.

    2015-06-01

    Field-aligned currents couple energy between the Earth's magnetosphere and ionosphere and are responsible for driving both micro and macro motions of plasma and neutral atoms in both regimes. These currents are believed to be a contributing energy source for ion acceleration in the polar ionosphere and may be detected via measurements of magnetic gradients along the track of a polar orbiting spacecraft, usually the north-south gradients of the east-west field component. The detection of such gradients does not require observatory class measurements of the geomagnetic field. The Magnetic Field instrument (MGF) measures the local magnetic field onboard the Enhanced Polar Outflow Probe (e-POP) satellite by using two ring-core fluxgate sensors to characterize and remove the stray spacecraft field. The fluxgate sensors have their heritage in the MAGSAT design, are double wound for reduced mass and cross-field dependence, and are mounted on a modest 0.9 m carbon-fiber boom. The MGF samples the magnetic field 160 times per sec (˜50 meters) to a resolution of 0.0625 nT and outputs data at 1952 bytes per second including temperature measurements. Its power consumption is 2.2 watts, and its noise level is 7 pT per root Hz at 1 Hz.

  1. On the Motion of the Field of a Permanent Magnet

    ERIC Educational Resources Information Center

    Leus, Vladimir; Taylor, Stephen

    2011-01-01

    A description is given of a series of recent experiments using a rotating magnetic circuit comprising a permanent magnet ring and yoke, and a stationary conductor in the air gap between the ring and yoke. The EMF induced in this case cannot be described by a simple application of Faraday's flux law. This is because the magnetic flux in the air gap

  2. On the Motion of the Field of a Permanent Magnet

    ERIC Educational Resources Information Center

    Leus, Vladimir; Taylor, Stephen

    2011-01-01

    A description is given of a series of recent experiments using a rotating magnetic circuit comprising a permanent magnet ring and yoke, and a stationary conductor in the air gap between the ring and yoke. The EMF induced in this case cannot be described by a simple application of Faraday's flux law. This is because the magnetic flux in the air gap…

  3. Swarm: ESA's Magnetic Field Mission

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  4. Representation of magnetic fields in space

    NASA Technical Reports Server (NTRS)

    Stern, D. P.

    1975-01-01

    Several methods by which a magnetic field in space can be represented are reviewed with particular attention to problems of the observed geomagnetic field. Time dependence is assumed to be negligible, and five main classes of representation are described by vector potential, scalar potential, orthogonal vectors, Euler potentials, and expanded magnetic field.

  5. DC-based magnetic field controller

    DOEpatents

    Kotter, D.K.; Rankin, R.A.; Morgan, J.P.

    1994-05-31

    A magnetic field controller is described for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a Hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage. 1 fig.

  6. DC-based magnetic field controller

    DOEpatents

    Kotter, Dale K.; Rankin, Richard A.; Morgan, John P,.

    1994-01-01

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

  7. Magnetic field effects on plasma ionization balance

    SciTech Connect

    Weisheit, J.C.

    1995-12-31

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

  8. Nonlinear energy dissipation of magnetic nanoparticles in oscillating magnetic fields

    NASA Astrophysics Data System (ADS)

    Soto-Aquino, D.; Rinaldi, C.

    2015-11-01

    The heating of magnetic nanoparticle suspensions subjected to alternating magnetic fields enables a variety of emerging applications such as magnetic fluid hyperthermia and triggered drug release. Rosensweig (2002) [25] obtained a model for the heat dissipation rate of a collection of non-interacting particles. However, the assumptions made in this analysis make it rigorously valid only in the limit of small applied magnetic field amplitude and frequency (i.e., values of the Langevin parameter that are much less than unity and frequencies below the inverse relaxation time). In this contribution we approach the problem from an alternative point of view by solving the phenomenological magnetization relaxation equation exactly for the case of arbitrary magnetic field amplitude and frequency and by solving a more accurate magnetization relaxation equation numerically. We also use rotational Brownian dynamics simulations of non-interacting magnetic nanoparticles subjected to an alternating magnetic field to estimate the rate of energy dissipation and compare the results of the phenomenological theories to the particle-scale simulations. The results are summarized in terms of a normalized energy dissipation rate and show that Rosensweig's expression provides an upper bound on the energy dissipation rate achieved at high field frequency and amplitude. Estimates of the predicted dependence of energy dissipation rate, quantified as specific absorption rate (SAR), on magnetic field amplitude and frequency, and particle core and hydrodynamic diameter, are also given.

  9. Minimizing magnetic fields for precision experiments

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  10. Minimizing magnetic fields for precision experiments

    SciTech Connect

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

    2015-06-21

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

  11. Bats Respond to Very Weak Magnetic Fields

    PubMed Central

    Tian, Lan-Xiang; Pan, Yong-Xin; Metzner, Walter; Zhang, Jin-Shuo; Zhang, Bing-Fang

    2015-01-01

    How animals, including mammals, can respond to and utilize the direction and intensity of the Earth’s magnetic field for orientation and navigation is contentious. In this study, we experimentally tested whether the Chinese Noctule, Nyctalus plancyi (Vespertilionidae) can sense magnetic field strengths that were even lower than those of the present-day geomagnetic field. Such field strengths occurred during geomagnetic excursions or polarity reversals and thus may have played an important role in the evolution of a magnetic sense. We found that in a present-day local geomagnetic field, the bats showed a clear preference for positioning themselves at the magnetic north. As the field intensity decreased to only 1/5th of the natural intensity (i.e., 10 μT; the lowest field strength tested here), the bats still responded by positioning themselves at the magnetic north. When the field polarity was artificially reversed, the bats still preferred the new magnetic north, even at the lowest field strength tested (10 μT), despite the fact that the artificial field orientation was opposite to the natural geomagnetic field (P<0.05). Hence, N. plancyi is able to detect the direction of a magnetic field even at 1/5th of the present-day field strength. This high sensitivity to magnetic fields may explain how magnetic orientation could have evolved in bats even as the Earth’s magnetic field strength varied and the polarity reversed tens of times over the past fifty million years. PMID:25922944

  12. Measurement of magnetic fields in stars

    SciTech Connect

    Landstreet, J.D.

    1980-05-01

    A review is presented of techniques of measuring magnetic fields in nondegenerate stars. The strengths and limitations of the classical photographic field measurement technique are compared to those of various photoelectric methods developed during the past decade, particularly the Balmer-line Zeeman analyzer technique. The problem of modeling magnetic data to infer the magnetic field geometry of an observed star is discussed. In the few cases where sufficient data are available to test the centered dipole geometry, it is found to be inadequate. It appears that most magnetic stars have field geometries at least as complex as the oblique decentered dipole (or dipole plus parallel linear quadrupole) model.

  13. Quark matter in a strong magnetic field

    SciTech Connect

    Chakrabarty, S.

    1996-07-01

    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.}

  14. Flow Transitions in a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.

    1996-01-01

    Critical Rayleigh numbers have been measured in a liquid metal cylinder of finite height in the presence of a rotating magnetic field. Several different stability regimes were observed, which were determined by the values of the Rayleigh and Hartmann numbers. For weak rotating magnetic fields and small Rayleigh numbers, the experimental observations can be explained by the existence of a single non-axisymmetric meridional roll rotating around the cylinder, driven by the azimuthal component of the magnetic field. The measured dependence of rotational velocity on magnetic field strength is consistent with the existence of laminar flow in this regime.

  15. Ferroelectric Cathodes in Transverse Magnetic Fields

    SciTech Connect

    Alexander Dunaevsky; Yevgeny Raitses; Nathaniel J. Fisch

    2002-07-29

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

  16. Magnetic vector field tag and seal

    DOEpatents

    Johnston, Roger G.; Garcia, Anthony R.

    2004-08-31

    One or more magnets are placed in a container (preferably on objects inside the container) and the magnetic field strength and vector direction are measured with a magnetometer from at least one location near the container to provide the container with a magnetic vector field tag and seal. The location(s) of the magnetometer relative to the container are also noted. If the position of any magnet inside the container changes, then the measured vector fields at the these locations also change, indicating that the tag has been removed, the seal has broken, and therefore that the container and objects inside may have been tampered with. A hollow wheel with magnets inside may also provide a similar magnetic vector field tag and seal. As the wheel turns, the magnets tumble randomly inside, removing the tag and breaking the seal.

  17. Operating a magnetic nozzle helicon thruster with strong magnetic field

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazunori; Komuro, Atsushi; Ando, Akira

    2016-03-01

    A pulsed axial magnetic field up to ˜2.8 kG is applied to a 26-mm-inner-diameter helicon plasma thruster immersed in a vacuum chamber, and the thrust is measured using a pendulum target. The pendulum is located 30-cm-downstream of the thruster, and the thruster rf power and argon flow rate are fixed at 1 kW and 70 sccm (which gives a chamber pressure of 0.7 mTorr). The imparted thrust increases as the applied magnetic field is increased and saturates at a maximum value of ˜9.5 mN for magnetic field above ˜2 kG. At the maximum magnetic field, it is demonstrated that the normalized plasma density, and the ion flow energy in the magnetic nozzle, agree within ˜50% and of 10%, respectively, with a one-dimensional model that ignores radial losses from the nozzle. This magnetic nozzle model is combined with a simple global model of the thruster source that incorporates an artificially controlled factor α, to account for radial plasma losses to the walls, where α = 0 and 1 correspond to zero losses and no magnetic field, respectively. Comparison between the experiments and the model implies that the radial losses in the thruster source are experimentally reduced by the applied magnetic field to about 10% of that obtained from the no magnetic field model.

  18. Studying dynamic chaos in microwave ring generators based on normally magnetized ferromagnetic film

    NASA Astrophysics Data System (ADS)

    Kondrashov, A. V.; Ustinov, A. B.; Kalinikos, B. A.

    2016-02-01

    We present results of an experimental investigation of the transition to a microwave dynamic chaos regime in ring oscillators based on normally magnetized yttrium iron garnet (YIG) films. It is established that an increase in the ring gain leads to the sequential generation of monochromatic, periodic, quasi-periodic, and chaotic signals. The quasi-periodic regime is characterized by the appearance of secondary modulation of the signal amplitude. In the regime of dynamic chaos generation, the parameters can be controlled by gain of the ring.

  19. Pulsed magnetic field magnetic force microscope and evaluation of magnetic properties of soft magnetic tips

    NASA Astrophysics Data System (ADS)

    Zheng, Yangdong; Yoshimura, Satoru; Egawa, Genta; Zheng, Fu; Kinoshita, Yukinori; Saito, Hitoshi

    2015-08-01

    A pulsed magnetic field magnetic force microscope (PMF-MFM) is developed for evaluation of the magnetic properties of nano-scale materials and devices, as well as the characteristics of MFM tips. We present the setup of the PMF-MFM system, and focus on the evaluation of a FeCo soft magnetic tip by PMF-MFM. We find a new theoretical method to calculate tip magnetization curves (M-H curves) using MFM phase signals. We measure the MFM phase and amplitude signals for the FeCo tip during the presence of the pulsed magnetic fields oriented parallel and antiparallel to the initial tip magnetization direction, and acquire the tip coercivity H c ~ 1.1?kOe. The tip M-H curves are also calculated using the MFM phase signals data. We obtain the basic features of the tip magnetic properties from the tip M-H curves.

  20. Magnetized quark matter with a magnetic-field dependent coupling

    NASA Astrophysics Data System (ADS)

    Li, Chang-Feng; Yang, Li; Wen, Xin-Jian; Peng, Guang-Xiong

    2016-03-01

    It was recently derived that the QCD running coupling is a function of the magnetic field strength under the strong magnetic field approximation. Inspired by this progress and based on the self-consistent solutions of gap equations, the properties of two-flavor and three-flavor quark matter are studied in the framework of the Nambu-Jona-Lasinio model with a magnetic-field-dependent running coupling. We find that the dynamical quark masses as functions of the magnetic field strength are not monotonous in the fully chirally broken phase. Furthermore, the stability of magnetized quark matter with the running coupling is enhanced by lowering the free energy per baryon, which is expected to be more stable than that of the conventional constant coupling case. It is concluded that the magnetized strange quark matter described by running coupling can be absolutely stable.

  1. Reducing Field Distortion in Magnetic Resonance Imaging

    NASA Technical Reports Server (NTRS)

    Eom, Byeong Ho; Penanen, Konstantin; Hahn, Inseob

    2010-01-01

    A concept for a magnetic resonance imaging (MRI) system that would utilize a relatively weak magnetic field provides for several design features that differ significantly from the corresponding features of conventional MRI systems. Notable among these features are a magnetic-field configuration that reduces (relative to the conventional configuration) distortion and blurring of the image, the use of a superconducting quantum interference device (SQUID) magnetometer as the detector, and an imaging procedure suited for the unconventional field configuration and sensor. In a typical application of MRI, a radio-frequency pulse is used to excite precession of the magnetic moments of protons in an applied magnetic field, and the decaying precession is detected for a short time following the pulse. The precession occurs at a resonance frequency proportional to the strengths of the magnetic field and the proton magnetic moment. The magnetic field is configured to vary with position in a known way; hence, by virtue of the aforesaid proportionality, the resonance frequency varies with position in a known way. In other words, position is encoded as resonance frequency. MRI using magnetic fields weaker than those of conventional MRI offers several advantages, including cheaper and smaller equipment, greater compatibility with metallic objects, and higher image quality because of low susceptibility distortion and enhanced spin-lattice-relaxation- time contrast. SQUID MRI is being developed into a practical MRI method for applied magnetic flux densities of the order of only 100 T

  2. Magnetic field evolution in interacting galaxies

    NASA Astrophysics Data System (ADS)

    Drzazga, R. T.; Chyży, K. T.; Jurusik, W.; Wiórkiewicz, K.

    2011-09-01

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

  3. Cosmic Magnetic Fields (IAU S259)

    NASA Astrophysics Data System (ADS)

    Strassmeier, Klaus G.; Kosovichev, Alexander G.; Beckman, John E.

    2009-06-01

    Preface K. G. Strassmeier, A. G. Kosovichev and J. E. Beckman; Organising committee; Conference photograph; Conference participants; Session 1. Interstellar magnetic fields, star-forming regions and the Death Valley Takahiro Kudoh and Elisabeta de Gouveia Dal Pino; Session 2. Multi-scale magnetic fields of the Sun; their generation in the interior, and magnetic energy release Nigel O. Weiss; Session 3. Planetary magnetic fields and the formation and evolution of planetary systems and planets; exoplanets Karl-Heinz Glassmeier; Session 4. Stellar magnetic fields: cool and hot stars Swetlana Hubrig; Session 5. From stars to galaxies and the intergalactic space Dimitry Sokoloff and Bryan Gaensler; Session 6. Advances in methods and instrumentation for measuring magnetic fields across all wavelengths and targets Tom Landecker and Klaus G. Strassmeier; Author index; Object index; Subject index.

  4. Variation of the ion composition in the ring current during magnetic storms: Van Allen Probes observations

    NASA Astrophysics Data System (ADS)

    Luo, Hao; Du, Aimin; Ge, Yasong; Cao, Xin; Zhang, Ying; Wang, Yuan

    2015-04-01

    It has been reported that the energy density of the oxygen ions in the ring current region will show more enhancements than protons during magnetic storms. Knowing how the ion composition changes during a magnetic storm is important for understanding the dynamic processes in the inner magnetosphere. By using ion flux data from HOPE and RBSPICE instruments on board the Van Allen probes, we study the energy density variation of both protons and oxygen ions during fifteen strong magnetic storms (minimum Dst < -80 nT) happened during year 2013 to 2014. Results provide important details about the ion composition at different storm stages and different magnetic local times. Results also give important indications about the ion acceleration in the inner magnetosphere and the source of the ring current ions during the magnetic storms.

  5. Magnetic field optimization of permanent magnet undulators for arbitrary polarization

    NASA Astrophysics Data System (ADS)

    Bahrdt, J.; Frentrup, W.; Gaupp, A.; Scheer, M.; Englisch, U.

    2004-01-01

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

  6. CONSTRUCTION AND POWER TEST OF THE EXTRACTION KICKER MAGNET FOR SNS ACCUMULATOR RING.

    SciTech Connect

    PAI, C.; HAHN, H.; HSEUH, H.; LEE, Y.; MENG, W.; MI,J.; SANDBERG, J.; TODD, R.; ET AL.

    2005-05-16

    Two extraction kicker magnet assemblies that contain seven individual pulsed magnet modules each will kick the proton beam vertically out of the SNS accumulator ring into the aperture of the extraction Lambertson septum magnet. The proton beam then travels to the 1.4 MW SNS target assembly. The 14 kicker magnets and major components of the kicker assembly have been fabricated in BNL. The inner surfaces of the kicker magnets were coated with TiN to reduce the secondary electron yield. All 14 PFN power supplies have been built, tested and delivered to OWL. Before final installation, a partial assembly of the kicker system with three kicker magnets was assembled to test the functions of each critical component in the system. In this paper we report the progress of the construction of the kicker components, the TIN coating of the magnets, the installation procedure of the magnets and the full power test of the kicker with the PFN power supply.

  7. Effects and Correction of Closed Orbit Magnet Errors in the SNS Ring

    SciTech Connect

    Bunch, S.C.; Holmes, J.

    2004-01-01

    We consider the effect and correction of three types of orbit errors in SNS: quadrupole displacement errors, dipole displacement errors, and dipole field errors. Using the ORBIT beam dynamics code, we focus on orbit deflection of a standard pencil beam and on beam losses in a high intensity injection simulation. We study the correction of these orbit errors using the proposed system of 88 (44 horizontal and 44 vertical) ring beam position monitors (BPMs) and 52 (24 horizontal and 28 vertical) dipole corrector magnets. Correction is carried out numerically by adjusting the kick strengths of the dipole corrector magnets to minimize the sum of the squares of the BPM signals for the pencil beam. In addition to using the exact BPM signals as input to the correction algorithm, we also consider the effect of random BPM signal errors. For all three types of error and for perturbations of individual magnets, the correction algorithm always chooses the three-bump method to localize the orbit displacement to the region between the magnet and its adjacent correctors. The values of the BPM signals resulting from specified settings of the dipole corrector kick strengths can be used to set up the orbit response matrix, which can then be applied to the correction in the limit that the signals from the separate errors add linearly. When high intensity calculations are carried out to study beam losses, it is seen that the SNS orbit correction system, even with BPM uncertainties, is sufficient to correct losses to less than 10-4 in nearly all cases, even those for which uncorrected losses constitute a large portion of the beam.

  8. Magnetic field decay in model SSC dipoles

    SciTech Connect

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

    1988-08-01

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

  9. Effect of disorder on magnetic resonance band gap of split-ring resonator structures.

    PubMed

    Aydin, Koray; Guven, Kaan; Katsarakis, Nikos; Soukoulis, Costas; Ozbay, Ekmel

    2004-11-29

    We investigated the influence of periodicity, misalignment, and disorder on the magnetic resonance gap of split-ring resonators (SRRs) which are essential components of left handed-metamaterials (LHMs). The resonance of a single SRR which is induced by the split is experimentally demonstrated by comparing transmission spectra of SRR and closed ring resonator. Misaligning the SRR boards do not affect the magnetic resonance gap, while destroying the periodicity results in a narrower band gap. The disorder in SRR layers cause narrower left-handed pass band and decrease the transmission level of composite metamaterials (CMMs), which may significantly affect the performance of these LHMs. PMID:19488229

  10. The Evolution of the Earth's Magnetic Field.

    ERIC Educational Resources Information Center

    Bloxham, Jeremy; Gubbins, David

    1989-01-01

    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)

  11. Cantilever magnetometry in pulsed magnetic fields

    NASA Astrophysics Data System (ADS)

    Naughton, M. J.; Ulmet, J. P.; Narjis, A.; Askenazy, S.; Chaparala, M. V.; Hope, A. P.

    1997-11-01

    The technique of cantilever magnetometry is shown to be functional in pulsed magnetic fields. Employing micromachined single crystal silicon cantilevers and capacitance detection, we demonstrated a utilizable sensitivity to magnetic moment of 2.510-12 Am2 in magnetic fields to 36 T, representing an improvement of more than a factor of 10 over competing technologies. Torque magnetization measurements on microcrystals of anisotropic superconductors are presented as evidence of the feasibility of the technique in long pulse magnets of pulse duration 0.1-1 s.

  12. Observation of field-induced domain wall propagation in magnetic nanowires by magnetic transmission X-ray microscopy

    SciTech Connect

    Bryan, M. T.; Fry, P. W.; Fischer, P.; Allwood, D. A.

    2007-12-01

    Magnetic transmission X-ray microscopy (M-TXM) is used to image domain walls in magnetic ring structures formed by a 300 nm wide, 24 nm thick Ni{sub 81}Fe{sub 19} nanowire. Both transverse and vortex type domain walls are observed after application of different field sequences. Domain walls can be observed by comparing images obtained from opposite field sequences, or else domain wall propagation observed by comparing successive images in a particular field sequence. This demonstrates the potential use of M-TXM in developing and understanding planar magnetic nanowire behavior.

  13. Magnetic field evolution of accreting neutron stars

    NASA Astrophysics Data System (ADS)

    Istomin, Y. N.; Semerikov, I. A.

    2016-01-01

    The flow of a matter, accreting on to a magnetized neutron star, is accompanied by an electric current. The closing of the electric current occurs in the crust of a neutron stars in the polar region across the magnetic field. But the conductivity of the crust along the magnetic field greatly exceeds the conductivity across the field, so the current penetrates deep into the crust down up to the superconducting core. The magnetic field, generated by the accretion current, increases greatly with the depth of penetration due to the Hall conductivity of the crust is also much larger than the transverse conductivity. As a result, the current begins to flow mainly in the toroidal direction, creating a strong longitudinal magnetic field, far exceeding an initial dipole field. This field exists only in the narrow polar tube of r width, narrowing with the depth, i.e. with increasing of the crust density ρ, r ∝ ρ-1/4. Accordingly, the magnetic field B in the tube increases with the depth, B∝ρ1/2, and reaches the value of about 1017 Gauss in the core. It destroys superconducting vortices in the core of a star in the narrow region of the size of the order of 10 cm. Because of generated density gradient of vortices, they constantly flow into this dead zone and the number of vortices decreases, the magnetic field of a star decreases as well. The attenuation of the magnetic field is exponential, B = B0(1 + t/τ)-1. The characteristic time of decreasing of the magnetic field τ is equal to τ ≃ 103 yr. Thus, the magnetic field of accreted neutron stars decreases to values of 108-109 Gauss during 107-106 yr.

  14. Magnetic fields in Neutron Stars

    NASA Astrophysics Data System (ADS)

    Viganò, D.; Pons, J. A.; Miralles, J. A.; Rea, N.

    2015-05-01

    Isolated neutron stars show a diversity in timing and spectral properties, which has historically led to a classification in different sub-classes. The magnetic field plays a key role in many aspects of the neutron star phenomenology: it regulates the braking torque responsible for their timing properties and, for magnetars, it provides the energy budget for the outburst activity and high quiescent luminosities (usually well above the rotational energy budget). We aim at unifying this observational variety by linking the results of the state-of-the-art 2D magneto-thermal simulations with observational data. The comparison between theory and observations allows to place two strong constraints on the physical properties of the inner crust. First, strong electrical currents must circulate in the crust, rather than in the star core. Second, the innermost part of the crust must be highly resistive, which is in principle in agreement with the presence of a novel phase of matter so-called nuclear pasta phase.

  15. Magnetic field shielding project. Final report

    SciTech Connect

    Fugate, D.; Whittemore, T.R.; Feero, W.E.; Hoburg, J.F.; Olsen, R.G.

    1998-11-01

    Magnetic field management research at EPRI has had three major components: transmission, distribution, and shielding. Shielding people and equipment from 60-Hz magnetic fields provided a particularly challenging objective. Although much was known and the science was well developed for shielding radio frequency fields, little was known about shielding power frequency fields. EPRI mounted a large research effort that reviewed basic principles; developed theory and practice; performed tests and verifications; and produced software and guides for design of effective shields.

  16. Relaxed plasmas in external magnetic fields

    SciTech Connect

    Spies, G.O. ); Li, J. )

    1994-09-01

    The extension of the theory of relaxed plasmas to external magnetic fields whose field lines intersect the wall is concisely formulated and then applied to the Extrap experiment [J. R. Drake, Plasma Phys. Controlled Fusion [bold 26], 387 (1984)]. It is found that the external octupole field, though not affecting the phenomenon of current saturation, inhibits field reversal at parts of the wall if it is sufficiently strong to generate magnetic x points within the plasma.

  17. Diffusion of magnetic field via turbulent reconnection

    NASA Astrophysics Data System (ADS)

    Santos de Lima, Reinaldo; Lazarian, Alexander; de Gouveia Dal Pino, Elisabete M.; Cho, Jungyeon

    2010-05-01

    The diffusion of astrophysical magnetic fields in conducting fluids in the presence of turbulence depends on whether magnetic fields can change their topology via reconnection in highly conducting media. Recent progress in understanding fast magnetic reconnection in the presence of turbulence is reassuring that the magnetic field behavior in computer simulations and turbulent astrophysical environments is similar, as far as magnetic reconnection is concerned. This makes it meaningful to perform MHD simulations of turbulent flows in order to understand the diffusion of magnetic field in astrophysical environments. Our studies of magnetic field diffusion in turbulent medium reveal interesting new phenomena. First of all, our 3D MHD simulations initiated with anti-correlating magnetic field and gaseous density exhibit at later times a de-correlation of the magnetic field and density, which corresponds well to the observations of the interstellar media. While earlier studies stressed the role of either ambipolar diffusion or time-dependent turbulent fluctuations for de-correlating magnetic field and density, we get the effect of permanent de-correlation with one fluid code, i.e. without invoking ambipolar diffusion. In addition, in the presence of gravity and turbulence, our 3D simulations show the decrease of the magnetic flux-to-mass ratio as the gaseous density at the center of the gravitational potential increases. We observe this effect both in the situations when we start with equilibrium distributions of gas and magnetic field and when we follow the evolution of collapsing dynamically unstable configurations. Thus the process of turbulent magnetic field removal should be applicable both to quasi-static subcritical molecular clouds and cores and violently collapsing supercritical entities. The increase of the gravitational potential as well as the magnetization of the gas increases the segregation of the mass and magnetic flux in the saturated final state of the simulations, supporting the notion that the reconnection-enabled diffusivity relaxes the magnetic field + gas system in the gravitational field to its minimal energy state. This effect is expected to play an important role in star formation, from its initial stages of concentrating interstellar gas to the final stages of the accretion to the forming protostar.

  18. High concentration ferronematics in low magnetic fields

    NASA Astrophysics Data System (ADS)

    Tóth-Katona, T.; Salamon, P.; Éber, N.; Tomašovičová, N.; Mitróová, Z.; Kopčanský, P.

    2014-12-01

    We investigated experimentally the magneto-optical and dielectric properties of magnetic-nanoparticle-doped nematic liquid crystals (ferronematics). Our studies focus on the effect of the very small orienting bias magnetic field Bbias, and that of the nematic director pretilt at the boundary surfaces in our systems sensitive to low magnetic fields. Based on the results we assert that Bbias is not necessarily required for a detectable response to low magnetic fields, and that the initial pretilt, as well as the aggregation of the nanoparticles play an important (though not yet explored enough) role.

  19. METALLIZATION OF CERAMIC VACUUM CHAMBERS FOR SNS RING INJECTION KICKER MAGNETS.

    SciTech Connect

    HE,P.; HSEUH,H.C.; TODD,R.J.

    2002-04-22

    Ceramic chambers will be used in the pulsed kicker magnets for the injection of H{sup -} into the US Spallation Neutron Source (SNS) accumulator ring. There are two reasons for using ceramic chambers in kickers: (1) to avoid shielding of a fast-changing external magnetic field by metallic chamber walls; and (2) to reduce heating due to eddy currents. The inner surfaces of the ceramic chambers will be coated with a conductive layer, possibly titanium (Ti) or copper with a titanium nitride (TiN) overlayer, to reduce the beam coupling impedance and provide passage for beam image current. This paper describes the development of sputtering method for the 0.83m long 16cm inner diameter ceramic chambers. Coatings of Ti, Cu and TiN with thicknesses up to 10 {micro}m were produced by means of DC magnetron sputtering. The difficulty of coating insulators was overcome with the introduction of an anode screen. Films with good adhesion, uniform longitudinal thickness, and conductivity were produced.

  20. Two-axis magnetic field sensor

    NASA Technical Reports Server (NTRS)

    Jander, Albrecht (Inventor); Nordman, Catherine A. (Inventor); Qian, Zhenghong (Inventor); Smith, Carl H. (Inventor)

    2006-01-01

    A ferromagnetic thin-film based magnetic field sensor with first and second sensitive direction sensing structures each having a nonmagnetic intermediate layer with two major surfaces on opposite sides thereof having a magnetization reference layer on one and an anisotropic ferromagnetic material sensing layer on the other having a length in a selected length direction and a smaller width perpendicular thereto and parallel to the relatively fixed magnetization direction. The relatively fixed magnetization direction of said magnetization reference layer in each is oriented in substantially parallel to the substrate but substantially perpendicular to that of the other. An annealing process is used to form the desired magnetization directions.

  1. Fluctuating magnetic field induced resonant activation

    SciTech Connect

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

    2014-12-14

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

  2. Passive Superconducting Flux Conservers for Rotating-Magnetic-Field-Driven Field-Reversed Configurations

    SciTech Connect

    Oz, E.; Myers, C. E.; Edwards, M. R.; Berlinger, B.; Brooks, A.; Cohen, S. A.

    2011-01-05

    The Princeton Field-Reversed Configuration (PFRC) experiment employs an odd-parity rotating magnetic field (RMFo) current drive and plasma heating system to form and sustain high-Β plasmas. For radial confinement, an array of coaxial, internal, passive, flux-conserving (FC) rings applies magnetic pressure to the plasma while still allowing radio-frequency RMFo from external coils to reach the plasma. The 3 ms pulse duration of the present experiment is limited by the skin time (τfc) of its room-temperature copper FC rings. To explore plasma phenomena with longer characteristic times, the pulse duration of the next-generation PFRC-2 device will exceed 100 ms, necessitating FC rings with (τfc > 300 ms. In this paper we review the physics of internal, discrete, passive FCs and describe the evolution of the PFRC's FC array. We then detail new experiments that have produced higher performance FC rings that contain embedded high-temperature superconducting (HTS) tapes. Several HTS tape winding configurations have been studied and a wide range of extended skin times, from 0.4 s to over 103 s, has been achieved. The new FC rings must carry up to 3 kA of current to balance the expected PFRC-2 plasma pressure, so the dependence of the HTS-FC critical current on the winding configuration and temperature was also studied. From these experiments, the key HTS-FC design considerations have been identified and HTS-FC rings with the desired performance characteristics have been produced.

  3. Ground Vehicle Navigation Using Magnetic Field Variation

    NASA Astrophysics Data System (ADS)

    Shockley, Jeremiah A.

    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.

  4. Modeling the evolution of galactic magnetic fields

    SciTech Connect

    Yar-Mukhamedov, D.

    2015-04-15

    An analytic model for evolution of galactic magnetic fields in hierarchical galaxy formation frameworks is introduced. Its major innovative components include explicit and detailed treatment of the physics of merger events, mass gains and losses, gravitational energy sources and delays associated with formation of large-scale magnetic fields. This paper describes the model, its implementation, and core results obtained by its means.

  5. General magnetic field on convective stars

    NASA Astrophysics Data System (ADS)

    Plachinda, S.

    2004-10-01

    The presence of weak general magnetic field for 21 stars with vigorous convection (spectral types F9-M3 and luminosity classes I-V) is detected. Variation of the general magnetic field as a function of stellar rotation is determined for two solar-like stars: ξ Boo A and 61 Cyg A.

  6. Magnetic Fields at the Center of Coils

    ERIC Educational Resources Information Center

    Binder, Philippe; Hui, Kaleonui; Goldman, Jesse

    2014-01-01

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

  7. Magnetic fields in the early Universe

    NASA Astrophysics Data System (ADS)

    Grasso, D.; Rubinstein, H. R.

    2001-07-01

    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 of galaxies. We argue that the most promising way to test this hypothesis is to look for possible imprints of magnetic fields on the temperature and polarization anisotropies of the cosmic microwave background radiation (CMBR). With this purpose in mind, we provide a review of the most relevant effects of magnetic fields on the CMBR. A long chapter of this review is dedicated to particle-physics-inspired models which predict the generation of magnetic fields during the early Universe evolution. Although it is still unclear if any of these models can really explain the origin of galactic and intergalactic magnetic fields, we show that interesting effects may arise anyhow. Among these effects, we discuss the consequences of strong magnetic fields on the big-bang nucleosynthesis, on the masses and couplings of the matter constituents, on the electroweak phase transition, and on the baryon and lepton number violating sphaleron processes. Several intriguing common aspects, and possible interplay, of magnetogenesis and baryogenesis are also discussed.

  8. Permanent magnet edge-field quadrupole

    DOEpatents

    Tatchyn, Roman O.

    1997-01-01

    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.

  9. Permanent magnet edge-field quadrupole

    DOEpatents

    Tatchyn, R.O.

    1997-01-21

    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.

  10. Interplanetary stream magnetism: Kinematic effects. [solar magnetic fields and wind

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Barouch, E.

    1974-01-01

    The particle density, and the magnetic field intensity and direction are calculated in corotating streams of the solar wind, assuming that the solar wind velocity is constant and radial and that its azimuthal variations are not two rapid. The effects of the radial velocity profile in corotating streams on the magnetic fields were examined using kinematic approximation and a variety of field configurations on the inner boundary. Kinematic and dynamic effects are discussed.

  11. Construction of cardiac tissue rings using a magnetic tissue fabrication technique.

    PubMed

    Akiyama, Hirokazu; Ito, Akira; Sato, Masanori; Kawabe, Yoshinori; Kamihira, Masamichi

    2010-01-01

    Here we applied a magnetic force-based tissue engineering technique to cardiac tissue fabrication. A mixture of extracellular matrix precursor and cardiomyocytes labeled with magnetic nanoparticles was added into a well containing a central polycarbonate cylinder. With the use of a magnet, the cells were attracted to the bottom of the well and allowed to form a cell layer. During cultivation, the cell layer shrank towards the cylinder, leading to the formation of a ring-shaped tissue that possessed a multilayered cell structure and contractile properties. These results indicate that magnetic tissue fabrication is a promising approach for cardiac tissue engineering. PMID:21152282

  12. Comparison of adjustable permanent magnetic field sources

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

  13. Levitation of a magnet by an alternating magnetic field

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  14. Orienting Paramecium with intense static magnetic fields

    NASA Astrophysics Data System (ADS)

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

    2004-03-01

    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).

  15. Processing of polymers in high magnetic fields

    SciTech Connect

    Douglas, E.P.; Smith, M.E.; Benicewicz, B.C.; Earls, J.D.; Priester, R.D. Jr.

    1996-05-01

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

  16. Magnetic Helicity and Large Scale Magnetic Fields: A Primer

    NASA Astrophysics Data System (ADS)

    Blackman, Eric G.

    2015-05-01

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

  17. Chaotic magnetic fields: Particle motion and energization

    SciTech Connect

    Dasgupta, Brahmananda; Ram, Abhay K.; Li, Gang; Li, Xiaocan

    2014-02-11

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

  18. Measurement of AC magnetic field distribution using magnetic resonance imaging.

    PubMed

    Ider, Y Z; Muftuler, L T

    1997-10-01

    Electric currents are applied to body in numerous applications in medicine such as electrical impedance tomography, cardiac defibrillation, electrocautery, and physiotherapy. If the magnetic field within a region is measured, the currents generating these fields can be calculated using the curl operator. In this study, magnetic fields generated within a phantom by currents passing through an external wire is measured using a magnetic resonance imaging (MRI) system. A pulse sequence that is originally designed for mapping static magnetic field inhomogeneity is adapted. AC current in the form of a burst sine wave is applied synchronously with the pulse sequence. The frequency of the applied current is in the audio range with an amplitude of 175-mA rms. It is shown that each voxel value of sequential images obtained by the proposed pulse sequence is modulated similar to a single tone broadband frequency modulated (FM) waveform with the ac magnetic field strength determining the modulation index. An algorithm is developed to calculate the ac magnetic field intensity at each voxel using the frequency spectrum of the voxel signal. Experimental results show that the proposed algorithm can be used to calculate ac magnetic field distribution within a conducting sample that is placed in an MRI system. PMID:9368117

  19. Magnetic field distribution inside the aperture of a steerer magnet prototype

    NASA Astrophysics Data System (ADS)

    Chiriţă, Ionel; Dan, Daniel; Tănase, Nicolae

    2015-11-01

    The High Energy Storage Ring (HESR), an important part of the Facility for Antiproton and Ion Research (FAIR) international project [1], which will be set up in Darmstadt in the next years, contains, among other magnets, several corrector magnets used for vertical and horizontal beam deviation. A prototype of a 2mrad vertical steerer magnet was designed by National Institute for R&D in Electrical Engineering (ICPE-CA) Romania in close cooperation with Forschungszentrum Jülich Germany [2] and then manufactured and tested by ICPE-CA [3], Romanian Institute for Electrical Engineering—Advanced Research. Magnetic field measurements using a 3D Hall probe were performed. Measured data and their analysis are presented. The system used for Hall probe positioning and data acquisition is also described.

  20. Morphology and magnetic flux distribution in superparamagnetic, single-crystalline Fe3O4 nanoparticle rings

    PubMed Central

    Takeno, Yumu; Murakami, Yasukazu; Sato, Takeshi; Tanigaki, Toshiaki; Park, Hyun Soon; Shindo, Daisuke; Ferguson, R. Matthew

    2014-01-01

    This study reports on the correlation between crystal orientation and magnetic flux distribution of Fe3O4 nanoparticles in the form of self-assembled rings. High-resolution transmission electron microscopy demonstrated that the nanoparticles were single-crystalline, highly monodispersed, (25 nm average diameter), and showed no appreciable lattice imperfections such as twins or stacking faults. Electron holography studies of these superparamagnetic nanoparticle rings indicated significant fluctuations in the magnetic flux lines, consistent with variations in the magnetocrystalline anisotropy of the nanoparticles. The observations provide useful information for a deeper understanding of the micromagnetics of ultrasmall nanoparticles, where the magnetic dipolar interaction competes with the magnetic anisotropy. PMID:25422526

  1. Magnetic field effects on the motion of circumplanetary dust

    NASA Astrophysics Data System (ADS)

    Jontof-Hutter, Daniel Simon

    Hypervelocity impacts on satellites or ring particles replenish circumplanetary dusty rings with grains of all sizes. Due to interactions with the plasma environment and sunlight, these grains become electrically charged. We study the motion of charged dust grains launched at the Kepler orbital speed, under the combined effects of gravity and the electromagnetic force. We conduct numerical simulations of dust grain trajectories, covering a broad range of launch distances from the planetary surface to beyond synchronous orbit, and the full range of charge-to-mass ratios from ions to rocks, with both positive and negative electric potentials. Initially, we assume that dust grains have a constant electric potential, and, treating the spinning planetary magnetic field as an aligned and centered dipole, we map regions of radial instability (positive grains only), where dust grains are driven to escape or collide with the planet at high speed, and vertical instability (both positive and negative charges) whereby grains launched near the equatorial plane and are forced up magnetic field lines to high latitudes, where they may collide with the planet. We derive analytical criteria for local stability in the equatorial plane, and solve for the boundaries between all unstable and stable outcomes. Comparing our analytical solutions to our numerical simulations, we develop an extensive model for the radial, vertical and azimuthal motions of dust grains of arbitrary size and launch location. We test these solutions at Jupiter and Saturn, both of whose magnetic fields are reasonably well represented by aligned dipoles, as well as at the Earth, whose magnetic field is close to an anti-aligned dipole. We then evaluate the robustness of our stability boundaries to more general conditions. Firstly, we examine the effects of non-zero launch speeds, of up to 0.5 km s-1, in the frame of the parent body. Although these only weakly affect stability boundaries, we find that the influence of a launch impulse on stability boundaries strongly depends on its direction. Secondly, we focus on the effects of higher-order magnetic field components on orbital stability. We find that vertical stability boundaries are particularly sensitive to a moderate vertical offset in an aligned dipolar magnetic field. This configuration suffices as a model for Saturn's full magnetic field. The vertical instability also expands to cover a wider range of launch distances in slightly tilted magnetic dipoles, like the magnetic field configurations for Earth and Jupiter. By contrast, our radial stability criteria remain largely unaffected by both dipolar tilts and vertical offsets. Nevertheless, a tilted dipole magnetic field model introduces non-axisymmetric forces on orbiting dust grains, which are exacerbated by the inclusion of other higher-order magnetic field components, including the quadrupolar and octupolar terms. Dust grains whose orbital periods are commensurate with the spatial periodicities of a rotating non-axisymmetric magnetic field experience destabilizing Lorentz resonances. These have been studied by other authors for the largest dust grains moving on perturbed Keplerian ellipses. With Jupiter's full magnetic field as our model, we extend the concept of Lorentz resonances to smaller dust grains and find that these can destabilize trajectories on surprisingly short timescales, and even cause negatively-charged dust grains to escape within weeks. We provide detailed numerically-derived stability maps highlighting the destabilizing effects of specific higher-order terms in Jupiter's magnetic field, and we develop analytical solutions for the radial locations of these resonances for all charge-to-mass ratios. We include stability maps for the full magnetic field configurations of Jupiter, Saturn, and Earth, to compare with our analytics. We further provide numerically-derived stability maps for the tortured magnetic fields of Uranus and Neptune. Relaxing the assumption of constant electric charges on dust, we test the effects of time-variable grain charging on dust grain motion in two distinct environments. Firstly, we examine orbital stability in the tenuous plasma of Jupiter's main ring and gossamer ring where sunlight, the dominant source of grain charging, is periodically interrupted by transit through the planetary shadow. This dramatically expands dynamical instabilities to cover a large range of grain sizes. Secondly, we study the motion of dust grain orbits in the dense plasma environment of the Io torus. Here dust grain charges deviate little from equilibrium, and our stability map conforms closely to that of constant, negatively-charged dust grains. Finally, we focus on the poorly understood spokes in Saturn's B ring, highlighting the observational constraints on spokes, and present our hypothesis for spoke formation.

  2. How do galaxies get their magnetic fields?

    NASA Astrophysics Data System (ADS)

    Beck, Alexander; Dolag, Klaus; Lesch, Harald

    2015-08-01

    The origin of magnetic fields in high-redshift and present-day galaxies is a long-standing problem. In this talk, we present a model for the seeding and evolution of magnetic fields in protogalaxies. Supernova (SN) explosions during the assembly of a protogalaxy self-consistently provide magnetic seed fields, which are subsequently amplified by compression, shear flows and random motions.Our model explains the origin of strong magnetic fields of $\\mu$G amplitude within the first starforming protogalactic structures shortly after the first stars have formed.We present cosmological simulations with the GADGET code of Milky Way-like galactic halo formation using a standard LCDM cosmology and analyse the strength and distribution of the evolving magnetic field.Within starforming regions and given typical dimensions and magnetic field strengths in canonical SN remnants, we inject a dipole-shape magnetic field at a rate of nG/Gyr. Subsequently, the magnetic field strength increases exponentially on timescales of a few ten million years within the innermost regions of the halo.Furthermore, turbulent diffusion, shocks and gas motions transport the magnetic field towards the halo outskirts. At redshift z=0, the entire galactic structures are magnetized and the field amplitude is of the order of a few microG in the center of the halo and nG at the virial radius. Additionally, we analyse the intrinsic rotation measure (RM) of the forming galactic halo over redshift. The mean halo intrinsic RM peaks between redshifts z=4 and z=2 and reaches absolute values around 1000 rad/m^2. Towards redshift z=0, the intrinsic RM values decline to a mean value below 10 rad/m^2. At high redshifts, the distribution of individual starforming and thus magnetized regions is widespread leading to a widespread distribution of large intrinsic RMs. Our model for the evolution of galactic magnetic fields solves the joint problem of magnetic field seeding and subsequent amplification and distribution. The magnetic fields in galaxies are a direct consequence of the very basic processes of star and galaxy formation.

  3. Exact scattering matrix of graphs in magnetic field and quantum noise

    SciTech Connect

    Caudrelier, Vincent; Mintchev, Mihail; Ragoucy, Eric

    2014-08-15

    We consider arbitrary quantum wire networks modelled by finite, noncompact, connected quantum graphs in the presence of an external magnetic field. We find a general formula for the total scattering matrix of the network in terms of its local scattering properties and its metric structure. This is applied to a quantum ring with N external edges. Connecting the external edges of the ring to heat reservoirs, we study the quantum transport on the graph in ambient magnetic field. We consider two types of dynamics on the ring: the free Schrödinger and the free massless Dirac equations. For each case, a detailed study of the thermal noise is performed analytically. Interestingly enough, in presence of a magnetic field, the standard linear Johnson-Nyquist law for the low temperature behaviour of the thermal noise becomes nonlinear. The precise regime of validity of this effect is discussed and a typical signature of the underlying dynamics is observed.

  4. Harmonics suppression in electromagnets with application to the ALS storage ring corrector magnet design

    SciTech Connect

    Schlueter, R.D.

    1991-01-28

    This memo presents an analytical development for prediction of skew harmonics in a iron core C-magnet to due arbitrarily positioned electromagnet coils. A structured approach is presented for the suppression of an arbitrary number of harmonic components to arbitrarily low values. Application of the analytical harmonic strength calculations coupled to the structured harmonic suppression approach is presented in the context of the design of the ALS storage ring corrector magnets.

  5. The Measurement of Magnetic Fields

    ERIC Educational Resources Information Center

    Berridge, H. J. J.

    1973-01-01

    Discusses five experimental methods used by senior high school students to provide an accurate calibration curve of magnet current against the magnetic flux density produced by an electromagnet. Compares the relative merits of the five methods, both as measurements and from an educational viewpoint. (JR)

  6. The magnetic field of ζ Orionis A

    NASA Astrophysics Data System (ADS)

    Blazère, A.; Neiner, C.; Tkachenko, A.; Bouret, J.-C.; Rivinius, Th.

    2015-10-01

    Context. ζ Ori A is a hot star claimed to host a weak magnetic field, but no clear magnetic detection was obtained so far. In addition, it was recently shown to be a binary system composed of a O9.5I supergiant and a B1IV star. Aims: We aim at verifying the presence of a magnetic field in ζ Ori A, identifying to which of the two binary components it belongs (or whether both stars are magnetic), and characterizing the field. Methods: Very high signal-to-noise spectropolarimetric data were obtained with Narval at the Bernard Lyot Telescope (TBL) in France. Archival HEROS, FEROS and UVES spectroscopic data were also used. The data were first disentangled to separate the two components. We then analyzed them with the least-squares deconvolution technique to extract the magnetic information. Results: We confirm that ζ Ori A is magnetic. We find that the supergiant component ζ Ori Aa is the magnetic component: Zeeman signatures are observed and rotational modulation of the longitudinal magnetic field is clearly detected with a period of 6.829 d. This is the only magnetic O supergiant known as of today. With an oblique dipole field model of the Stokes V profiles, we show that the polar field strength is ~140 G. Because the magnetic field is weak and the stellar wind is strong, ζ Ori Aa does not host a centrifugally supported magnetosphere. It may host a dynamical magnetosphere. Its companion ζ Ori Ab does not show any magnetic signature, with an upper limit on the undetected field of ~300 G. Based on observations obtained at the Télescope Bernard Lyot (USR5026) operated by the Observatoire Midi-Pyrénées, Université de Toulouse (Paul Sabatier), Centre National de la Recherche Scientifique of France.Appendix A is available in electronic form at http://www.aanda.org

  7. The magnetic field in the disk of our Galaxy

    NASA Astrophysics Data System (ADS)

    Han, J. L.; Qiao, G. J.

    1994-08-01

    The magnetic field in the disk of our Galaxy is investigated by using the Rotation Measures (RMs) of pulsars and Extragalactic Radio Sources (ERSes). Through analyses of the RMs of carefully selected pulsar samples, it is found that the Galaxy has a global field of BiSymmetric Spiral (BSS) configuration, rather than a concentric ring or an AxiSymmetric Spiral (ASS) configuration. The Galactic magnetic field of BSS structure is supposed to be of primordial origin. The pitch angle of the BSS structure is -8.2deg+/-0.5deg. The field geometry shows that the field goes along the Carina-Sagittarius arm, which is delineated by Giant Molecular Clouds (GMCs). The amplitude of the BSS field is 1.8+/-0.3μG. The first field strength maximum is at r_0_=11.9+/-0.15 kpc in the direction of l=180deg. The field is strong in the interarm regions and it reverses in the arm regions. In the vicinity of the Sun, it has a strength of ~1.4μG and reverses at 0.2-0.3kpc in the direction of l=0deg. Because of the unknown electron distribution of the Galaxy and other difficulties, it is impossible to derive the galactic field from the RMs of ERSes very quantitatively. Nevertheless, the RMs of ERSes located in the region of the two galactic poles are used to estimate the vertical component of the local galactic field, which is found to have a strength of 0.2-0.3μG and is directed from the south galactic pole to the north galactic pole. The scale height of the magnetic disk of the Galaxy is estimated from the RMs of all-sky distributed ERSes, being about 1.2+/-0.4pc. The regular magnetic field of our Galaxy, which is probably similar to that of M81, extends far from the optical disk.

  8. Diamagnetism in zigzag hexagonal graphene rings

    NASA Astrophysics Data System (ADS)

    Xu, Ning; Chen, Qiao; Tian, Hongyu; Wang, Baolin; Ding, Jianwen

    2016-03-01

    The electronic structure and magnetic response of hexagonal graphene rings have been studied within the tight-binding formalism. The calculations show that hexagonal graphene rings possess unusually large diamagnetic moments in the presence of a perpendicular magnetic field. The magnetic-field-driven carriers flow clockwise and anticlockwise along the inner and outer edge of rings owing to quantum Hall effect. The value of magnetic moment is almost proportional to the number of atoms of rings, due to more conduction electrons participating in magnetic moment forming process. Additionally, we find the diamagnetic moment shows a relative weak dependence on the temperature.

  9. Antiaromatic character of 16 ? electron octaethylporphyrins: magnetically induced ring currents from DFT-GIMIC calculations.

    PubMed

    Fliegl, Heike; Pichierri, Fabio; Sundholm, Dage

    2015-03-19

    The magnetically induced current density susceptibility, also called current density, has been calculated for a recently synthesized octaethylporphyrin (OEP) zinc(II) dication with formally 16 ? electrons. Numerical integration of the current density passing selected chemical bonds yields the current pathway around the porphyrinoid ring and the strength of the ring current. The current strengths show that the OEP-Zn(II) dication is strongly antiaromatic, as also concluded experimentally. The calculation of the ring current pathway shows that all 24 ? electrons participate in the transport of the ring current because the current splits into inner and outer branches of practically equal strengths at the four pyrrolic rings. The corresponding neutral octaethylporphyrinoid without Zn and inner hydrogens is found to be antiaromatic, sustaining a paratropic ring current along the inner pathway with 16 ? electrons. The neutral OEP-Zn(II) molecule with formally 18 ? electrons is found to be almost as aromatic as free-base porphyrin. However, also in this case, all 26 ? electrons contribute to the ring current, as for free-base porphyrin. A comparison of calculated and measured (1)H NMR chemical shifts is presented. The current strength susceptibility under experimental conditions has been estimated by assuming a linear relation between experimental shielding constants and calculated current strengths. PMID:25141236

  10. Magnetic fields in noninvasive brain stimulation.

    PubMed

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

    2014-04-01

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

  11. On the magnetic fields in voids

    NASA Astrophysics Data System (ADS)

    Beck, A. M.; Hanasz, M.; Lesch, H.; Remus, R.-S.; Stasyszyn, F. A.

    2013-02-01

    We study the possible magnetization of cosmic voids by void galaxies. Recently, observations revealed isolated star-forming galaxies within the voids. Furthermore, a major fraction of a voids volume is expected to be filled with magnetic fields of a minimum strength of about 10-15 G on Mpc scales. We estimate the transport of magnetic energy by cosmic rays (CR) from the void galaxies into the voids. We assume that CRs and winds are able to leave small isolated void galaxies shortly after they assembled, and then propagate within the voids. For a typical void, we estimate the magnetic field strength and volume-filling factor depending on its void galaxy population and possible contributions of strong active galactic nuclei (AGNs) which border the voids. We argue that the lower limit on the void magnetic field can be recovered, if a small fraction of the magnetic energy contained in the void galaxies or void bordering AGNs is distributed within the voids.

  12. Field Mapping System for Solenoid Magnet

    NASA Astrophysics Data System (ADS)

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

    2007-01-01

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

  13. Magnetic-field-controlled reconfigurable semiconductor logic.

    PubMed

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

    2013-02-01

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

  14. Ohm's law for mean magnetic fields

    SciTech Connect

    Boozer, A.H.

    1984-11-01

    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.

  15. Modeling solar force-free magnetic fields

    NASA Astrophysics Data System (ADS)

    Low, B. C.; Lou, Y. Q.

    1990-03-01

    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 and the free energy associated with the electric current are finite and can be calculated directly from the magnetic field at the plane boundary using the virial theorem. In the study of solar magnetic fields with data from vector magnetographs, there is a long-standing interest in devising algorithms to extrapolate for the force-free magnetic field in a given domain from prescribed field values at the boundary. The closed-form magnetic fields of this paper open up an opportunity for testing the reliability and accuracy of algorithms that claim the capability of performing this extrapolation. The extrapolation procedure as an ill-posed mathematical problem is discussed.

  16. Dynamic Magnetic Field Applications for Materials Processing

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Grugel, Richard N.; Motakef, S.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Magnetic fields, variable in time and space, can be used to control convection in electrically conducting melts. Flow induced by these fields has been found to be beneficial for crystal growth applications. It allows increased crystal growth rates, and improves homogeneity and quality. Particularly beneficial is the natural convection damping capability of alternating magnetic fields. One well-known example is the rotating magnetic field (RMF) configuration. RMF induces liquid motion consisting of a swirling basic flow and a meridional secondary flow. In addition to crystal growth applications, RMF can also be used for mixing non-homogeneous melts in continuous metal castings. These applied aspects have stimulated increasing research on RMF-induced fluid dynamics. A novel type of magnetic field configuration consisting of an axisymmetric magnetostatic wave, designated the traveling magnetic field (TMF), has been recently proposed. It induces a basic flow in the form of a single vortex. TMF may find use in crystal growth techniques such as the vertical Bridgman (VB), float zone (FZ), and the traveling heater method. In this review, both methods, RMF and TMF are presented. Our recent theoretical and experimental results include such topics as localized TMF, natural convection dumping using TMF in a vertical Bridgman configuration, the traveling heater method, and the Lorentz force induced by TMF as a function of frequency. Experimentally, alloy mixing results, with and without applied TMF, will be presented. Finally, advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, will be discussed.

  17. Origin of magnetic fields in galaxies

    SciTech Connect

    Souza, Rafael S. de; Opher, Reuven

    2010-03-15

    Microgauss magnetic fields are observed in all galaxies at low and high redshifts. The origin of these intense magnetic fields is a challenging question in astrophysics. We show here that the natural plasma fluctuations in the primordial Universe (assumed to be random), predicted by the fluctuation -dissipation theorem, predicts {approx}0.034 {mu}G fields over {approx}0.3 kpc regions in galaxies. If the dipole magnetic fields predicted by the fluctuation-dissipation theorem are not completely random, microgauss fields over regions > or approx. 0.34 kpc are easily obtained. The model is thus a strong candidate for resolving the problem of the origin of magnetic fields in < or approx. 10{sup 9} years in high redshift galaxies.

  18. External-field-free magnetic biosensor

    SciTech Connect

    Li, Yuanpeng; Wang, Yi; Klein, Todd; Wang, Jian-Ping

    2014-03-24

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

  19. Polarized radiation diagnostics of stellar magnetic fields

    NASA Astrophysics Data System (ADS)

    Mathys, Gautier

    The main techniques used to diagnose magnetic fields in stars from polarimetric observations are presented. First, a summary of the physics of spectral line formation in the presence of a magnetic field is given. Departures from the simple case of linear Zeeman effect are briefly considered: partial Paschen-Back effect, contribution of hyperfine structure, and combined Stark and Zeeman effects. Important approximate solutions of the equation of transfer of polarized light in spectral lines are introduced. The procedure for disk-integration of emergent Stokes profiles, which is central to stellar magnetic field studies, is described, with special attention to the treatment of stellar rotation. This formalism is used to discuss the determination of the mean longitudinal magnetic field (through the photographic technique and through Balmer line photopolarimetry). This is done within the specific framework of Ap stars, which, with their unique large-scale organized magnetic fields, are an ideal laboratory for studies of stellar magnetism. Special attention is paid to those Ap stars whose magnetically split line components are resolved in high-dispersion Stokes I spectra, and to the determination of their mean magnetic field modulus. Various techniques of exploitation of the information contained in polarized spectral line profiles are reviewed: the moment technique (in particular, the determination of the crossover and of the mean quadratic field), Zeeman-Doppler imaging, and least-squares deconvolution. The prospects that these methods open for linear polarization studies are sketched. The way in which linear polarization diagnostics complement their Stokes I and V counterparts is emphasized by consideration of the results of broad band linear polarization measurements. Illustrations of the use of various diagnostics to derive properties of the magnetic fields of Ap stars are given. This is used to show the interest of deriving more physically realistic models of the geometric structure of these fields. How this can possibly be achieved is briefly discussed. An overview of the current status of polarimetric studies of magnetic fields in non-degenerate stars of other types is presented. The final section is devoted to magnetic fields of white dwarfs. Current knowledge of magnetic fields of isolated white dwarfs is briefly reviewed. Diagnostic techniques are discussed, with particular emphasis on the variety of physical processes to be considered for understanding of spectral line formation over the broad range of magnetic field strengths encountered in these stars.

  20. Manipulating Cells with Static Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Valles, J. M.; Guevorkian, K.

    2005-07-01

    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.

  1. Quantitative modeling of planetary magnetospheric magnetic fields

    NASA Technical Reports Server (NTRS)

    Walker, R. J.

    1979-01-01

    Three new quantitative models of the earth's magnetospheric magnetic field have recently been presented: the Olson-Pfitzer model, the Tsyganenko model, and the Voigt model. The paper reviews these models in some detail with emphasis on the extent to which they have succeeded in improving on earlier models. The models are compared with the observed field in both magnitude and direction. Finally, the application to other planetary magnetospheres of the techniques used to model the earth's magnetospheric magnetic field is briefly discussed.

  2. Ohm's law for mean magnetic fields

    SciTech Connect

    Boozer, A.H.

    1986-05-01

    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.

  3. Surface magnetic fields across the HR Diagram

    NASA Astrophysics Data System (ADS)

    Landstreet, John D.

    2015-10-01

    The past 20 years have seen remarkable advances in spectropolarimetric instrumentation that have allowed us, for the first time, to identify some magnetic stars in most major stages of stellar evolution. We are beginning to see the broad outline of how such fields change during stellar evolution, to confront theoretical hypotheses and models of magnetic field structure and evolution with detailed data, and to understand more of the ways in which the presence of a field in turn affects stellar structure and evolution.

  4. The magnetic fields of young stars

    NASA Astrophysics Data System (ADS)

    Yang, Hao

    2009-06-01

    The T Tauri stars (TTSs) are young, solar-type stars which display many spectral pecularities. Understanding the magnetic properties of TTSs is a key to make sense of their curious behaviors. First, high resolution optical and infrared (IR) echelle spectra are analyzed to measure the surface magnetic field of the classical T Tauri star (CTTS) TW Hydrae. Key stellar parameters are determined from detailed spectrum synthesis of atomic and molecular absorption features in the optical, and then modeling the line profiles of the four magnetically sensitive Ti I lires in the K band yields the average magnetic field on TW Hydrae. Extensive Monté Carlo tests are performed to quantify systematic errors in the analysis technique, finding that reasonable errors in the effective temperature or surface gravity produce around 10% uncertainty in the magnetic field measurements. Then a similar analysis technique is applied to detect strong magnetic fields on 5 additional stars in the TW Hydrae Association (TWA) as well as 14 TTSs in the Orion Nebula Cluster (ONC). We combine these measurements with previous measurements of 14 stars in Taurus to study the potential evolution of magnetic field properties during the first 10 million years of stellar evolution. In addition, to probe the magnetic geometry on the surface of TW Hydrae, high resolution circular spectropolarimetry of this star is analyzed to measure the net longitudinal magnetic field. Significant polarization is detected on the final night of six consecutive nights of observing, but no net polarization is seen on other nights. This longitudinal field detection is still much lower than that which would be consistent with a dipole geometry on the stellar suface. On the other hand, strong circular polarization is detected in the He I l5876 and Ca II l8498 emission lines, indicating a strong field in the line forming regions of these features. Overall, strong magnetic fields of kG level are commonly found among TTSs and the magnetic configuration is probably not a simple dipole as current magnetospheric accretion theories assume. With magnetic pressure likely dominating over gas pressure in the stellar photospheres, the entire stellar surfaces could be covered with magnetic fields, and this might be responsible for the underproduction of the X-ray emission of TTSs. It is also suggested that these large-scale magnetic fields could be of a primordial origin.

  5. Biological effects of high DC magnetic fields

    SciTech Connect

    Tenforde, T.S.

    1981-06-01

    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 processes, and are therefore potentially sensitive to electrodynamic interactions with an applied magnetic field. In the specific case of the visual system, magnetic interactions could also arise through orientational effects on the magnetically anisotropic photopigment molecules within retinal photoreceptor cells. In addition to studies with potentially sensitive target tissues, an evaluation is being made of magnetic field effects on a broad range of other physiological functions in laboratory mammals, including the measurement of circadian rhythms using noninvasive recording techniques. Results of investigations of magnetic field effects on the conformation of DNA, and on the growth and development of plants and insects are also reported. Figures and tables provide a brief summary of some representative observations in each of the research areas described. No significant alterations were observed in any of the physiological parameters examined to date, with the exception of major changes that occur in the electrocardiogram during magnetic field exposure. Studies with several species of animals have provided evidence that this phenomenon is attributable to electrical potentials that are induced during pulsatile blood flow in the aorta and in other major vessels of the circulatory system.

  6. Field mapping system for cyclotron magnet

    NASA Astrophysics Data System (ADS)

    Park, K. H.; Jung, Y. G.; Kim, D. E.; Kang, B. K.; Yoon, M.; Chai, J. S.; Kim, Y. S.

    2005-06-01

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

  7. Vector Magnetic Field in Emerging Flux Regions

    NASA Astrophysics Data System (ADS)

    Schmieder, B.; Pariat, E.

    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):

  8. An Extraordinary Magnetic Field Map of Mars

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    The Mars Global Surveyor spacecraft has completed two Mars years in nearly circular polar orbit at a nominal altitude of 400 km. The Mars crust is at least an order of magnitude more intensely magnetized than that of the Earth [1], and intriguing in both its global distribution and geometric properties [2,3]. Measurements of the vector magnetic field have been used to map the magnetic field of crustal origin to high accuracy [4]. We present here a new map of the magnetic field with an order of magnitude increased sensitivity to crustal magnetization. The map is assembled from > 2 full years of MGS night-side observations, and uses along-track filtering to greatly reduce noise due to external field variations.

  9. Quark matter under strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Peres Menezes, Débora; Laércio Lopes, Luiz

    2016-02-01

    We revisit three of the mathematical formalisms used to describe magnetized quark matter in compact objects within the MIT and the Nambu-Jona-Lasinio models and then compare their results. The tree formalisms are based on 1) isotropic equations of state, 2) anisotropic equations of state with different parallel and perpendicular pressures and 3) the assumption of a chaotic field approximation that results in a truly isotropic equation of state. We have seen that the magnetization obtained with both models is very different: while the MIT model produces well-behaved curves that are always positive for large magnetic fields, the NJL model yields a magnetization with lots of spikes and negative values. This fact has strong consequences on the results based on the existence of anisotropic equations of state. We have also seen that, while the isotropic formalism results in maximum stellar masses that increase considerably when the magnetic fields increase, maximum masses obtained with the chaotic field approximation never vary more than 5.5%. The effect of the magnetic field on the radii is opposed in the MIT and NJL models: with both formalisms, isotropic and chaotic field approximation, for a fixed mass, the radii increase with the increase of the magnetic field in the MIT bag model and decrease in the NJL, the radii of quark stars described by the NJL model being smaller than the ones described by the MIT model.

  10. Magnetic field generation at high magnetic Reynolds number

    NASA Technical Reports Server (NTRS)

    Levy, E. H.

    1978-01-01

    The lowest-order contribution of finite electrical resistivity to the process of magnetic-field regeneration at high magnetic Reynolds number is calculated. It is found that finite resistivity changes the calculated regeneration rate by less than a factor of 2.

  11. Magnetic reconnection at the edge of Uranus's magnetic field

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2014-09-01

    A new modeling study sheds light on how the magnetosphere of Uranus compares to those of other planets. Magnetospheres around the inner planets Mercury and Earth are primarily driven by the solar wind—the charged particles spewed out from the Sun—through magnetic reconnection, in which the planet's magnetic field lines break and reconnect, releasing energy in the process.

  12. Field of a moving locked charge as applied to beambeam interactions in storage rings

    NASA Astrophysics Data System (ADS)

    Silenko, Alexander J.

    2015-12-01

    It is shown that the Lorentz transformation cannot in general be formally applied to potentials and fields of particles locked in a certain region. In particular, this property relates to nucleons in nuclei and to particles and nuclei in storage rings. Even if they move with high velocities, their electric fields are defined by the Coulomb law. The result obtained is rather important for the planned deuteron electric-dipole-moment experiment in storage rings.

  13. Normal glow discharge in axial magnetic field

    NASA Astrophysics Data System (ADS)

    Surzhikov, S.; Shang, J.

    2014-10-01

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

  14. The magnetic field of Mercury, part 1

    NASA Technical Reports Server (NTRS)

    Ness, N. F.; Behannon, K. W.; Lepping, R. P.; Whang, Y. C.

    1974-01-01

    An updated analysis and interpretation is presented of the magnetic field observations obtained during the Mariner 10 encounter with the planet Mercury. The combination of data relating to position of the detached bow shock wave and magnetopause, and the geometry and magnitude of the magnetic field within the magnetosphere-like region surrounding Mercury, lead to the conclusion that an internal planetary field exists with dipole moment approximately 5.1 x 10 the 22nd power Gauss sq cm. The dipole axis has a polarity sense similar to earth's and is tilted 7 deg from the normal to Mercury's orbital plane. The magnetic field observations reveal a significant distortion of the modest Hermean field (350 Gamma at the equator) by the solar wind flow and the formation of a magnetic tail and neutral sheet which begins close to the planet on the night side. The composite data is not consistent with a complex induction process driven by the solar wind flow.

  15. Magnetic fields in an expanding universe

    NASA Astrophysics Data System (ADS)

    Kastor, David; Traschen, Jennie

    2014-04-01

    We find a solution to 4D Einstein-Maxwell theory coupled to a massless dilaton field, for all values of the dilaton coupling, describing a Melvin magnetic field in an expanding universe with ‘stiff matter’ equation of state parameter w = +1. As the universe expands, magnetic flux becomes more concentrated around the symmetry axis for dilaton coupling a\\lt1/\\sqrt{3} and more dispersed for a\\gt1/\\sqrt{3}. An electric field circulates around the symmetry axis in the direction determined by Lenz's law. For a = 0 the magnetic flux through a disc of fixed comoving radius is proportional to the proper area of the disc. This result disagrees with the usual expectation based on a test magnetic field that this flux should be constant, and we show why this difference arises. We also find a Melvin solution in an accelerating universe with w = -7/9 for a dilaton field with a certain exponential potential.

  16. Electric-field guiding of magnetic skyrmions

    NASA Astrophysics Data System (ADS)

    Upadhyaya, Pramey; Yu, Guoqiang; Amiri, Pedram Khalili; Wang, Kang L.

    2015-10-01

    We theoretically study equilibrium and dynamic properties of nanosized magnetic skyrmions in thin magnetic films with broken inversion symmetry, where an electric field couples to magnetization via spin-orbit coupling. Based on a symmetry-based phenomenology and micromagnetic simulations we show that this electric-field coupling, via renormalizing the micromagnetic energy, modifies the equilibrium properties of the skyrmion. This change, in turn, results in a significant alteration of the current-induced skyrmion motion. Particularly, the speed and direction of the skyrmion can be manipulated by designing a desired energy landscape electrically, which we describe within Thiele's analytical model and demonstrate in micromagnetic simulations including electric-field-controlled magnetic anisotropy. We additionally use this electric-field control to construct gates for controlling skyrmion motion exhibiting a transistorlike and multiplexerlike function. The proposed electric-field effect can thus provide a low-energy electrical knob to extend the reach of information processing with skyrmions.

  17. Dissipative charged fluid in a magnetic field

    NASA Astrophysics Data System (ADS)

    Abbasi, Navid; Davody, Ali

    2016-05-01

    We study the collective excitations in a dissipative charged fluid at zero chemical potential when an external magnetic field is present. While in the absence of magnetic field, four collective excitations appear in the fluid, we find five hydrodynamic modes here. This implies that the magnetic field splits the degeneracy between the transverse shear modes. Using linear response theory, we then compute the retarded response functions. In particular, it turns out that the correlation between charge and the energy fluctuations will no longer vanish, even at zero chemical potential. By use of the response functions, we also derive the relevant Kubo formulas for the transport coefficients.

  18. Magnetic field quality analysis using ANSYS

    SciTech Connect

    Dell'Orco, D.; Chen, Y.

    1991-03-01

    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.

  19. XUV harmonic enhancement by magnetic fields

    SciTech Connect

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

    1986-09-01

    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.

  20. Environmental magnetic fields: Influences on early embryogenesis

    SciTech Connect

    Cameron, I.L.; Hardman, W.E.; Winters, W.D.; Zimmerman, S.; Zimmerman, A.M. )

    1993-04-01

    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.

  1. Complex Magnetic Fields of Compact Stars

    NASA Astrophysics Data System (ADS)

    Mason, Paul A.

    2015-08-01

    Observational evidence for strong magnetic fields of accreting white dwarfs, in cataclysmic binaries, and accreting neutron stars, in low mass X-ray binaries, is reviewed. Increasingly, complex magnetic fields have been involked to explain effects that cannot be modelled with pure dipolar fields. This has been the result of both improved observations, providing stronger field constraints, as well as robust modelling techniques. While observations are often not able to clearly differentiate between dipolar and multi-polar fileds, examples are shown that suggest that complex fields are likely a quite common feature of compact stars.

  2. Ring-field TMA for PRISMA: theory, optical design, and performance measurements

    NASA Astrophysics Data System (ADS)

    Calamai, Luciano; Barsotti, Stefano; Fossati, Enrico; Formaro, Roberto; Thompson, Kevin P.

    2015-09-01

    PRISMA (PRecursore IperSpettrale della Missione Applicativa) Hyperspectral Payload is an Electro-Optical instrument developed in Selex ES for the dedicated ASI (Italian Space Agency) mission for Earth observation. The performance requirements for this mission are stringent and have led to an instrument design that is based on a Ring-Field Three Mirror Anastigmat (Ring-Field TMA), a two channel prism dispersion based spectrometer (VNIR and SWIR), and a Panchromatic Camera. The Ring-Field TMA contains three mirrors (two conics and one conic with some higher order correction). Exceptional performance has been achieved by not only introducing 3rd order astigmatism to balance the 5th astigmatism at the ring field zone as is traditional in an Offner-type design but, additionally, 3rd order coma has been controlled to align the balance of the linear and field cubic coma terms at the same ring field zone. The predicted wavefront performance of the design over the field of view will be highlighted. An assembly and alignment procedure for the Ring-Field TMA has been developed from the results of the sensitivity and tolerances analysis. The tilt and decenter sensitivity of the design form is nearly exclusively determined by 3rd order binodal astigmatism. The nodal position is linear with perturbation, which greatly simplifies the decisions on alignment compensators. The manufactured mirrors of the Ring-Field TMA have been aligned at Selex ES and as will be reported the preliminary results in terms of optical quality are in good agreement with the predicted as-built performance, both on-axis and in the field.

  3. Some Structural Properties of Solar Magnetic Fields

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

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

  4. The theory of the Galactic magnetic field

    NASA Technical Reports Server (NTRS)

    Zweibel, Ellen G.

    1987-01-01

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

  5. Magnetic properties and hyperfine interactions in Cr8, Cr7Cd, and Cr7Ni molecular rings from 19F-NMR

    NASA Astrophysics Data System (ADS)

    Bordonali, L.; Garlatti, E.; Casadei, C. M.; Furukawa, Y.; Lascialfari, A.; Carretta, S.; Troiani, F.; Timco, G.; Winpenny, R. E. P.; Borsa, F.

    2014-04-01

    A detailed experimental investigation of the 19F nuclear magnetic resonance is made on single crystals of the homometallic Cr8 antiferromagnetic molecular ring and heterometallic Cr7Cd and Cr7Ni rings in the low temperature ground state. Since the F- ion is located midway between neighboring magnetic metal ions in the ring, the 19F-NMR spectra yield information about the local electronic spin density and 19F hyperfine interactions. In Cr8, where the ground state is a singlet with total spin ST = 0, the 19F-NMR spectra at 1.7 K and low external magnetic field display a single narrow line, while when the magnetic field is increased towards the first level crossing field, satellite lines appear in the 19F-NMR spectrum, indicating a progressive increase in the Boltzmann population of the first excited state ST = 1. In the heterometallic rings, Cr7Cd and Cr7Ni, whose ground state is magnetic with ST = 3/2 and ST = 1/2, respectively, the 19F-NMR spectrum has a complicated structure which depends on the strength and orientation of the magnetic field, due to both isotropic and anisotropic transferred hyperfine interactions and classical dipolar interactions. From the 19F-NMR spectra in single crystals we estimated the transferred hyperfine constants for both the F--Ni2+ and the F--Cd2+ bonds. The values of the hyperfine constants compare well to the ones known for F--Ni2+ in KNiF3 and NiF2 and for F--Cr3+ in K2NaCrF6. The results are discussed in terms of hybridization of the 2s, 2p orbitals of the F- ion and the d orbitals of the magnetic ion. Finally, we discuss the implications of our results for the electron-spin decoherence.

  6. Magnetic properties and hyperfine interactions in Cr₈, Cr₇Cd, and Cr₇Ni molecular rings from ¹⁹F-NMR.

    PubMed

    Bordonali, L; Garlatti, E; Casadei, C M; Furukawa, Y; Lascialfari, A; Carretta, S; Troiani, F; Timco, G; Winpenny, R E P; Borsa, F

    2014-04-14

    A detailed experimental investigation of the (19)F nuclear magnetic resonance is made on single crystals of the homometallic Cr8 antiferromagnetic molecular ring and heterometallic Cr7Cd and Cr7Ni rings in the low temperature ground state. Since the F(-) ion is located midway between neighboring magnetic metal ions in the ring, the (19)F-NMR spectra yield information about the local electronic spin density and (19)F hyperfine interactions. In Cr8, where the ground state is a singlet with total spin S(T) = 0, the (19)F-NMR spectra at 1.7 K and low external magnetic field display a single narrow line, while when the magnetic field is increased towards the first level crossing field, satellite lines appear in the (19)F-NMR spectrum, indicating a progressive increase in the Boltzmann population of the first excited state S(T) = 1. In the heterometallic rings, Cr7Cd and Cr7Ni, whose ground state is magnetic with S(T) = 3/2 and S(T) = 1/2, respectively, the (19)F-NMR spectrum has a complicated structure which depends on the strength and orientation of the magnetic field, due to both isotropic and anisotropic transferred hyperfine interactions and classical dipolar interactions. From the (19)F-NMR spectra in single crystals we estimated the transferred hyperfine constants for both the F(-)-Ni(2+) and the F(-)-Cd(2+) bonds. The values of the hyperfine constants compare well to the ones known for F(-)-Ni(2+) in KNiF3 and NiF2 and for F(-)-Cr(3+) in K2NaCrF6. The results are discussed in terms of hybridization of the 2s, 2p orbitals of the F(-) ion and the d orbitals of the magnetic ion. Finally, we discuss the implications of our results for the electron-spin decoherence. PMID:24735298

  7. Magnetic properties and hyperfine interactions in Cr8, Cr7Cd, and Cr7Ni molecular rings from 19F-NMR

    SciTech Connect

    Bordonali, L; Garlatti, E; Casadei, C M; Furukawa, Y; Lascialfari, A; Carretta, S; Troiani, F; Timco, G; Winpenny, R E; Borsa, F

    2014-04-14

    A detailed experimental investigation of the 19F nuclear magnetic resonance is made on single crystals of the homometallic Cr₈ antiferromagnetic molecular ring and heterometallic Cr₇Cd and Cr₇ Ni rings in the low temperature ground state. Since the F- ion is located midway between neighboring magnetic metal ions in the ring, the 19F-NMR spectra yield information about the local electronic spin density and ¹⁹F hyperfine interactions. In Cr8, where the ground state is a singlet with total spin S T = 0, the ¹⁹F-NMR spectra at 1.7 K and low external magnetic field display a single narrow line, while when the magnetic field is increased towards the first level crossing field, satellite lines appear in the ¹⁹F-NMR spectrum, indicating a progressive increase in the Boltzmann population of the first excited state S T = 1. In the heterometallic rings, Cr₇Cd and Cr₇ Ni, whose ground state is magnetic with S T = 3/2 and S T = 1/2, respectively, the ¹⁹F-NMR spectrum has a complicated structure which depends on the strength and orientation of the magnetic field, due to both isotropic and anisotropic transferred hyperfine interactions and classical dipolar interactions. From the 19F-NMR spectra in single crystals we estimated the transferred hyperfine constants for both the F⁻-Ni2⁺ and the F⁻-Cd2⁺ bonds. The values of the hyperfine constants compare well to the ones known for F⁻-Ni2⁺ in KNiF₃ and NiF₂ and for F⁻-Cr³⁺ in K₂NaCrF₆. The results are discussed in terms of hybridization of the 2s, 2p orbitals of the F⁻ ion and the d orbitals of the magnetic ion. Finally, we discuss the implications of our results for the electron-spin decoherence.

  8. Directed Plasma Flow across Magnetic Field

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

    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.

  9. Magnetic Field Strengths in Photodissociation Regions

    NASA Astrophysics Data System (ADS)

    Balser, Dana S.; Anish Roshi, D.; Jeyakumar, S.; Bania, T. M.; Montet, Benjamin T.; Shitanishi, J. A.

    2016-01-01

    We measure carbon radio recombination line (RRL) emission at 5.3 {{GHz}} toward four H ii regions with the Green Bank Telescope to determine the magnetic field strength in the photodissociation region (PDR) that surrounds the ionized gas. Roshi suggests that the non-thermal line widths of carbon RRLs from PDRs are predominantly due to magneto-hydrodynamic waves, thus allowing the magnetic field strength to be derived. We model the PDR with a simple geometry and perform the non-LTE radiative transfer of the carbon RRL emission to solve for the PDR physical properties. Using the PDR mass density from these models and the carbon RRL non-thermal line width we estimate total magnetic field strengths of B? 100{--}300 ? {{G}} in W3 and NGC 6334A. Our results for W49 and NGC 6334D are less well constrained with total magnetic field strengths between B? 200{--}1000 ? {{G}}. H i and OH Zeeman measurements of the line of sight magnetic field strength ({B}{{los}}), taken from the literature, are between a factor of ? 0.5{--}1 of the lower bound of our carbon RRL magnetic field strength estimates. Since | {B}{{los}}| ?slant B, our results are consistent with the magnetic origin of the non-thermal component of carbon RRL widths.

  10. Space applications of superconductivity - High field magnets

    NASA Technical Reports Server (NTRS)

    Fickett, F. R.

    1979-01-01

    The paper discusses developments in superconducting magnets and their applications in space technology. Superconducting magnets are characterized by high fields (to 15T and higher) and high current densities combined with low mass and small size. The superconducting materials and coil design are being improved and new high-strength composites are being used for magnet structural components. Such problems as maintaining low cooling temperatures (near 4 K) for long periods of time and degradation of existing high-field superconductors at low strain levels can be remedied by research and engineering. Some of the proposed space applications of superconducting magnets include: cosmic ray analysis with magnetic spectrometers, energy storage and conversion, energy generation by magnetohydrodynamic and thermonuclear fusion techniques, and propulsion. Several operational superconducting magnet systems are detailed.

  11. Tracing Magnetic Fields by Atomic Alignment in Extended Radiation Fields

    NASA Astrophysics Data System (ADS)

    Zhang, Heshou; Yan, Huirong; Dong, Le

    2015-05-01

    Tracing magnetic field is crucial as magnetic field plays an important role in many astrophysical processes. Earlier studies have demonstrated that ground state alignment (GSA) is an effective way to detect a weak magnetic field (1G≳ B≳ {{10}-15} G) in a diffuse medium. We explore the atomic alignment in the presence of an extended radiation field for both absorption lines and emission lines. The alignment in the circumstellar medium, binary systems, disks, and the local interstellar medium are considered in order to study the alignment in the radiation field where the pumping source has a clear geometric structure. Furthermore, the multipole expansion method is adopted to study GSA induced in the radiation field with unidentified pumping sources. We study the alignment in the dominant radiation components of the general radiation field: the dipole and quadrupole radiation field. We discuss the approximation of GSA in a general radiation field by summing the contribution from the dipole and quadrupole radiation field. We conclude that GSA is a powerful tool for detecting weak magnetic fields in the diffuse medium in general radiation fields.

  12. Compact Electric- And Magnetic-Field Sensor

    NASA Technical Reports Server (NTRS)

    Winterhalter, Daniel; Smith, Edward

    1994-01-01

    Compact sensor measures both electric and magnetic fields. Includes both short electric-field dipole and search-coil magnetometer. Three mounted orthogonally providing triaxial measurements of electromagnetic field at frequencies ranging from near 0 to about 10 kHz.

  13. Recent biophysical studies in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Maret, Georg

    1990-06-01

    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.

  14. Nonlinear magnetization dynamics under circularly polarized field.

    PubMed

    Bertotti, G; Serpico, C; Mayergoyz, I D

    2001-01-22

    Exact analytical results are presented for the nonlinear large motion of the magnetization vector in a body with uniaxial symmetry subject to a circularly polarized field. The absence of chaos, the existence of pure time-harmonic magnetization modes with no generation of higher-order harmonics, and the existence of quasiperiodic magnetization modes with spontaneous breaking of the rotational symmetry are proven. Application to ferromagnetic resonance and connection with the Stoner-Wohlfarth model are discussed. PMID:11177922

  15. High Field Pulse Magnets with New Materials

    NASA Astrophysics Data System (ADS)

    Li, L.; Lesch, B.; Cochran, V. G.; Eyssa, Y.; Tozer, S.; Mielke, C. H.; Rickel, D.; van Sciver, S. W.; Schneider-Muntau, H. J.

    2004-11-01

    High performance pulse magnets using the combination of CuNb conductor and Zylon fiber composite reinforcement with bore sizes of 24, 15 and 10 mm have been designed, manufactured and tested to destruction. The magnets successfully reached the peak fields of 64, 70 and 77.8 T respectively with no destruction. Failures occurred near the end flanges at the layer. The magnet design, manufacturing and testing, and the mode of the failure are described and analyzed.

  16. Magnetic monopoles in field theory and cosmology.

    PubMed

    Rajantie, Arttu

    2012-12-28

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

  17. On the Helicity of Open Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Prior, C.; Yeates, A. R.

    2014-06-01

    We reconsider the topological interpretation of magnetic helicity for magnetic fields in open domains, and relate this to the relative helicity. Specifically, our domains stretch between two parallel planes, and each of these ends may be magnetically open. It is demonstrated that, while the magnetic helicity is gauge-dependent, its value in any gauge may be physically interpreted as the average winding number among all pairs of field lines with respect to some orthonormal frame field. In fact, the choice of gauge is equivalent to the choice of reference field in the relative helicity, meaning that the magnetic helicity is no less physically meaningful. We prove that a particular gauge always measures the winding with respect to a fixed frame, and propose that this is normally the best choice. For periodic fields, this choice is equivalent to measuring relative helicity with respect to a potential reference field. However, for aperiodic fields, we show that the potential field can be twisted. We prove by construction that there always exists a possible untwisted reference field.

  18. On the helicity of open magnetic fields

    SciTech Connect

    Prior, C.; Yeates, A. R.

    2014-06-01

    We reconsider the topological interpretation of magnetic helicity for magnetic fields in open domains, and relate this to the relative helicity. Specifically, our domains stretch between two parallel planes, and each of these ends may be magnetically open. It is demonstrated that, while the magnetic helicity is gauge-dependent, its value in any gauge may be physically interpreted as the average winding number among all pairs of field lines with respect to some orthonormal frame field. In fact, the choice of gauge is equivalent to the choice of reference field in the relative helicity, meaning that the magnetic helicity is no less physically meaningful. We prove that a particular gauge always measures the winding with respect to a fixed frame, and propose that this is normally the best choice. For periodic fields, this choice is equivalent to measuring relative helicity with respect to a potential reference field. However, for aperiodic fields, we show that the potential field can be twisted. We prove by construction that there always exists a possible untwisted reference field.

  19. Constraints on primordial magnetic fields from inflation

    NASA Astrophysics Data System (ADS)

    Green, Daniel; Kobayashi, Takeshi

    2016-03-01

    We present generic bounds on magnetic fields produced from cosmic inflation. By investigating field bounds on the vector potential, we constrain both the quantum mechanical production of magnetic fields and their classical growth in a model independent way. For classical growth, we show that only if the reheating temperature is as low as Treh lesssim 102 MeV can magnetic fields of 10-15 G be produced on Mpc scales in the present universe. For purely quantum mechanical scenarios, even stronger constraints are derived. Our bounds on classical and quantum mechanical scenarios apply to generic theories of inflationary magnetogenesis with a two-derivative time kinetic term for the vector potential. In both cases, the magnetic field strength is limited by the gravitational back-reaction of the electric fields that are produced simultaneously. As an example of quantum mechanical scenarios, we construct vector field theories whose time diffeomorphisms are spontaneously broken, and explore magnetic field generation in theories with a variable speed of light. Transitions of quantum vector field fluctuations into classical fluctuations are also analyzed in the examples.

  20. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, John R.

    1987-12-01

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

  1. Laminated magnet field coil sheath

    DOEpatents

    Skaritka, J.R.

    1987-05-15

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

  2. Negative Index of Refraction Observed in a Single Layer of ClosedRing Magnetic Dipole Resonators

    SciTech Connect

    Hao, Zhao; Martin, Michael C.; Harteneck, Bruce; Cabrini,Stefano; Anderson, Erik H.

    2007-11-27

    We report the results of a spectroscopic study of a singlelayer of metallic single closed ring resonators on free-standing thinmembrane at near-normal and grazing angles of incidence. When themagnetic component of the light is perpendicular to the ring plane, weobserve a negative index of refraction down to -1 around 150 terahertz(THz), attributed to a strong magnetic dipolar resonance and a broadelectric resonance in this metamaterial. We experimentally identify thedifferent resonance modes and the spectral region of negative refractiveindex on a series of samples with different feature and lattice sizes,comparing to electromagnetic simulations.

  3. Magnetic space-based field measurements

    NASA Technical Reports Server (NTRS)

    Langel, R. A.

    1981-01-01

    Satellite measurements of the geomagnetic field began with the launch of Sputnik 3 in May 1958 and have continued sporadically in the intervening years. A list of spacecraft that have made significant contributions to an understanding of the near-earth geomagnetic field is presented. A new era in near-earth magnetic field measurements began with NASA's launch of Magsat in October 1979. Attention is given to geomagnetic field modeling, crustal magnetic anomaly studies, and investigations of the inner earth. It is concluded that satellite-based magnetic field measurements make global surveys practical for both field modeling and for the mapping of large-scale crustal anomalies. They are the only practical method of accurately modeling the global secular variation. Magsat is providing a significant contribution, both because of the timeliness of the survey and because its vector measurement capability represents an advance in the technology of such measurements.

  4. Estimating the magnetic field strength from magnetograms

    NASA Astrophysics Data System (ADS)

    Asensio Ramos, A.; Martnez Gonzlez, M. J.; Manso Sainz, R.

    2015-05-01

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

  5. High-field magnetization of magnetic graphite intercalation compounds

    NASA Astrophysics Data System (ADS)

    Nicholls, J. T.; McNiff, E. J., Jr.; Dresselhaus, G.

    1990-09-01

    We report low-temperature, high-field (T<=4.2 K, H=0-18 teslas) magnetization measurements of CoCl2- and NiCl2-graphite intercalation compounds (GIC's), both parallel (M) and perpendicular (M⊥) to the c axis. From the saturation magnetization values of the stage-1 and stage-2 CoCl2-GIC's, we have been able to measure the anisotropy of the g values, and thus calculate the amount of XY spin anisotropy in these compounds. Magnetization measurements show that upon intercalation, the Co2+ ions retain their anisotropic magnetic behavior. In addition, the state-1 CoCl2-GIC's exhibit unusual hysteresis phenomena when the magnetization is measured along the c axis. Upon doping of the stage-1 CoCl2-GIC's with nonmagnetic Mg2+ ions, the magnitude of the hysteresis in M(H) decreases and the magnetization saturates. In contrast to the behavior of the stage-1 CoCl2-GIC's, state-1 NiCl2-GIC's exhibit a very small XY spin anisotropy. The magnetization M(H) is featureless for magnetic fields H>1 tesla and exhibits no high-field hysteresis. The high-field c-axis magnetization of unintercalated highly oriented pyrolytic graphite was also examined; the susceptibility was χ==M/H=-28.5×10-6 emu/g, and low-field de Haas-van Alphen oscillations were observed with a frequency consistent with previously identified majority hole carriers.

  6. Heat Capacity Measurements in Pulsed Magnetic Fields

    SciTech Connect

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

    1998-10-23

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

  7. The significance of vector magnetic field measurements

    NASA Technical Reports Server (NTRS)

    Hagyard, M. J.

    1990-01-01

    Observations of four flaring solar active regions, obtained during 1980-1986 with the NASA Marshall vector magnetograph (Hagyard et al., 1982 and 1985), are presented graphically and characterized in detail, with reference to nearly simultaneous Big Bear Solar Observatory and USAF ASW H-alpha images. It is shown that the flares occurred where local photospheric magnetic fields differed most from the potential field, with initial brightening on either side of a magnetic-neutral line near the point of maximum angular shear (rather than that of maximum magnetic-field strength, typically 1 kG or greater). Particular emphasis is placed on the fact that these significant nonpotential features were detected only by measuring all three components of the vector magnetic field.

  8. Magnetic Field Response Measurement Acquisition System

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E.; Taylor, Bryant D.; Shams, Qamar A.; Fox, Robert L.

    2005-01-01

    A measurement acquisition method that alleviates many shortcomings of traditional measurement systems is presented in this paper. The shortcomings are a finite number of measurement channels, weight penalty associated with measurements, electrical arcing, wire degradations due to wear or chemical decay and the logistics needed to add new sensors. The key to this method is the use of sensors designed as passive inductor-capacitor circuits that produce magnetic field responses. The response attributes correspond to states of physical properties for which the sensors measure. A radio frequency antenna produces a time-varying magnetic field used to power the sensor and receive the magnetic field response of the sensor. An interrogation system for discerning changes in the sensor response is presented herein. Multiple sensors can be interrogated using this method. The method eliminates the need for a data acquisition channel dedicated to each sensor. Methods of developing magnetic field response sensors and the influence of key parameters on measurement acquisition are discussed.

  9. Magnetic Field Response Measurement Acquisition System

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E. (Inventor); Taylor, Bryant D. (Inventor); Shams, Qamar A. (Inventor); Fox, Robert L. (Inventor); Fox, Christopher L. (Inventor); Fox, Melanie L. (Inventor); Bryant, Robert G. (Inventor)

    2006-01-01

    Magnetic field response sensors designed as passive inductor-capacitor circuits produce magnetic field responses whose harmonic frequencies correspond to states of physical properties for which the sensors measure. Power to the sensing element is acquired using Faraday induction. A radio frequency antenna produces the time varying magnetic field used for powering the sensor, as well as receiving the magnetic field response of the sensor. An interrogation architecture for discerning changes in sensor s response kequency, resistance and amplitude is integral to the method thus enabling a variety of measurements. Multiple sensors can be interrogated using this method, thus eliminating the need to have a data acquisition channel dedicated to each sensor. The method does not require the sensors to be in proximity to any form of acquisition hardware. A vast array of sensors can be used as interchangeable parts in an overall sensing system.

  10. Fractal structure of the interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Klein, L. W.

    1985-01-01

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

  11. High-Field Superconducting Magnets Supporting PTOLEMY

    NASA Astrophysics Data System (ADS)

    Hopkins, Ann; Luo, Audrey; Osherson, Benjamin; Gentile, Charles; Tully, Chris; Cohen, Adam

    2013-10-01

    The Princeton Tritium Observatory for Light, Early Universe, Massive Neutrino Yield (PTOLEMY) is an experiment planned to collect data on Big Bang relic neutrinos, which are predicted to be amongst the oldest and smallest particles in the universe. Currently, a proof-of-principle prototype is being developed at Princeton Plasma Physics Laboratory to test key technologies associated with the experiment. A prominent technology in the experiment is the Magnetic Adiabatic Collimation with an Electrostatic Filter (MAC-E filter), which guides tritium betas along magnetic field lines generated by superconducting magnets while deflecting those of lower energies. B field mapping is performed to ensure the magnets produce a minimum field at the midpoint of the configuration of the magnets and to verify accuracy of existing models. Preliminary tests indicate the required rapid decrease in B field strength from the bore of the more powerful 3.35 T magnet, with the field dropping to 0.18 T approximately 0.5 feet from the outermost surface of the magnet.

  12. Bounce averaged diffusion coefficients in a physics based magnetic field geometry from RAM-SCB

    NASA Astrophysics Data System (ADS)

    Zhao, Lei; Yu, Yiqun; Delzanno, Gian Luca; Jordanova, Vania K.

    2014-10-01

    In this work we explore wave-particle interaction in the radiation belt. By applying quasilinear theory, we obtain the particle diffusion coefficients in both pitch angle and energy for different configurations of the Earth's magnetic field. We consider the Earth's magnetic dipole field as a reference, and compare the results against non-dipole field configurations corresponding to quiet and stormy conditions. The latter are obtained with RAM-SCB, a code that models the Earth's ring current and provide a realistic modeling of the Earth's magnetic field. The bounce averaged electron pitch angle diffusion coefficients are calculated for each magnetic field configuration. The equatorial pitch angle, wave frequency and spectral distribution of whistler waves are shown to affect the bounce averaged diffusion coefficients. In addition, wave-particle resonance is significantly influenced by the magnetic field configuration: in storm conditions, diffusion is strongly reduced for some equatorial pitch angles.

  13. Causes of Ring-Related Leg Injuries in Birds – Evidence and Recommendations from Four Field Studies

    PubMed Central

    Griesser, Michael; Schneider, Nicole A.; Collis, Mary-Anne; Overs, Anthony; Guppy, Michael; Guppy, Sarah; Takeuchi, Naoko; Collins, Pete; Peters, Anne; Hall, Michelle L.

    2012-01-01

    One of the main techniques for recognizing individuals in avian field research is marking birds with plastic and metal leg rings. However, in some species individuals may react negatively to rings, causing leg injuries and, in extreme cases, the loss of a foot or limb. Here, we report problems that arise from ringing and illustrate solutions based on field data from Brown Thornbills (Acanthiza pusilla) (2 populations), Siberian Jays (Perisoreus infaustus) and Purple-crowned Fairy-wrens (Malurus coronatus). We encountered three problems caused by plastic rings: inflammations triggered by material accumulating under the ring (Purple-crowned Fairy-wrens), contact inflammations as a consequence of plastic rings touching the foot or tibio-tarsal joint (Brown Thornbills), and toes or the foot getting trapped in partly unwrapped flat-band colour rings (Siberian Jays). Metal rings caused two problems: the edges of aluminium rings bent inwards if mounted on top of each other (Brown Thornbills), and too small a ring size led to inflammation (Purple-crowned Fairy-wrens). We overcame these problems by changing the ringing technique (using different ring types or larger rings), or using different adhesive. Additionally, we developed and tested a novel, simple technique of gluing plastic rings onto metal rings in Brown Thornbills. A review of studies reporting ring injuries (N = 23) showed that small birds (<55 g body weight) are more prone to leg infections while larger birds (>35 g) tend to get rings stuck over their feet. We give methodological advice on how these problems can be avoided, and suggest a ringing hazard index to compare the impact of ringing in terms of injury on different bird species. Finally, to facilitate improvements in ringing techniques, we encourage online deposition of information regarding ringing injuries of birds at a website hosted by the European Union for Bird Ringing (EURING). PMID:23300574

  14. Accretion and Current Discs Controlled by Strong Magnetic Field

    NASA Astrophysics Data System (ADS)

    Belenkaya, Elena

    2012-06-01

    In the presence of a strong magnetic field, accretion discs surrounding neutron stars, black holes, and white dwarfs have their inner edges at their Alfvén radii, i.e., at the distance where magnetic energy density becomes equal to the kinetic energy density. Young stars, X-ray binaries, active galactic nuclei possess discs which could generate jets. Jets arise at the inner boundary of the disc at the Alfvén radius when magnetic field is sufficiently strong. We emphasize here that not only accretion discs possess this feature. The inner edge of the heliospheric current sheet is located at the solar Alfván radius. The inner edges of the Jovian magnetodisc and Saturnian ring current are also placed close to their Alfván radii. Thus, in the presence of a strong magnetic field the inner edges of a lot of astrophysical discs are located at Alfván radii regardless of the nature of their origin, material, and motion direction. This means that discs under such conditions are well described by MHD theory.

  15. Magnetic fields and massive star formation

    SciTech Connect

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

    2014-09-10

    Massive stars (M > 8 M {sub ☉}) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 μm obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of ≲0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within 40° of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the outflow axis appears to be randomly oriented with respect to the magnetic field in the core. This result suggests that at the scale of accretion disks (≲ 10{sup 3} AU), angular momentum and dynamic interactions possibly due to close binary or multiple systems dominate over magnetic fields. With this unprecedentedly large sample of massive clumps, we argue on a statistical basis that magnetic fields play an important role during the formation of dense cores at spatial scales of 0.01-0.1 pc in the context of massive star and cluster star formation.

  16. Nonlinear diffusion waves in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Oreshkin, V. I.; Chaikovsky, S. A.; Labetskaya, N. A.; Datsko, I. M.; Rybka, D. V.; Ratakhin, N. A.; Khishchenko, K. V.

    2015-11-01

    The nonlinear diffusion of a magnetic field and the large-scale instabilities arising upon an electrical explosion of conductors in a superstrong (2-3 MG) magnetic field were investigated experimentally on the MIG high-current generator (up to 2.5 peak current, 100 ns current rise time). It was observed that in the nonlinear stage of the process, the wavelength of thermal instabilities (striations) increased with a rate of 1.5-3 km/s.

  17. Magnetic Fields and Massive Star Formation

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

    Massive stars (M > 8 M ⊙) typically form in parsec-scale molecular clumps that collapse and fragment, leading to the birth of a cluster of stellar objects. We investigate the role of magnetic fields in this process through dust polarization at 870 μm obtained with the Submillimeter Array (SMA). The SMA observations reveal polarization at scales of lsim0.1 pc. The polarization pattern in these objects ranges from ordered hour-glass configurations to more chaotic distributions. By comparing the SMA data with the single dish data at parsec scales, we found that magnetic fields at dense core scales are either aligned within 40° of or perpendicular to the parsec-scale magnetic fields. This finding indicates that magnetic fields play an important role during the collapse and fragmentation of massive molecular clumps and the formation of dense cores. We further compare magnetic fields in dense cores with the major axis of molecular outflows. Despite a limited number of outflows, we found that the outflow axis appears to be randomly oriented with respect to the magnetic field in the core. This result suggests that at the scale of accretion disks (lsim 103 AU), angular momentum and dynamic interactions possibly due to close binary or multiple systems dominate over magnetic fields. With this unprecedentedly large sample of massive clumps, we argue on a statistical basis that magnetic fields play an important role during the formation of dense cores at spatial scales of 0.01-0.1 pc in the context of massive star and cluster star formation.

  18. Plasma diffusion through multidipole magnetic fields

    NASA Astrophysics Data System (ADS)

    Ferreira, J. L.

    1992-03-01

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

  19. Plasma diffusion through multidipole magnetic fields

    NASA Astrophysics Data System (ADS)

    Ferreira, Jose Leonardo

    The diffusion of a cold plasma through multidipole fields of a magnetic picket fence is presented. The ion diffusion and trapping is determined by electric potentials inside the multidipole fields. The electron diffusion is regulated by an anomalous transport process driven by an ion acoustic instability inside the magnetic sheath. Particles drifting with velocities above the ion acoustic speed generates high amplitude turbulent waves responsible for all anomalous diffusion process.

  20. Plasma diffusion through multidipole magnetic fields

    NASA Astrophysics Data System (ADS)

    Ferreira, Jose Leonardo

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

  1. The magnetic field investigation on Cluster

    NASA Technical Reports Server (NTRS)

    Balogh, A.; Cowley, S. W. H.; Southwood, D. J.; Musmann, G.; Luhr, H.; Neubauer, F. M.; Glassmeier, K.-H.; Riedler, W.; Heyn, M. F.; Acuna, M. H.

    1988-01-01

    The magnetic field investigation of the Cluster four-spacecraft mission is designed to provide intercalibrated measurements of the B magnetic field vector. The instrumentation and data processing of the mission are discussed. The instrumentation is identical on the four spacecraft. It consists of two triaxial fluxgate sensors and of a failure tolerant data processing unit. The combined analysis of the four spacecraft data will yield such parameters as the current density vector, wave vectors, and the geometry and structure of discontinuities.

  2. Interstellar magnetic fields: An observational perspective

    SciTech Connect

    Goodman, A.A.

    1989-01-01

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

  3. Magnetic field transfer device and method

    DOEpatents

    Wipf, S.L.

    1990-02-13

    A magnetic field transfer device includes a pair of oppositely wound inner coils which each include at least one winding around an inner coil axis, and an outer coil which includes at least one winding around an outer coil axis. The windings may be formed of superconductors. The axes of the two inner coils are parallel and laterally spaced from each other so that the inner coils are positioned in side-by-side relation. The outer coil is outwardly positioned from the inner coils and rotatable relative to the inner coils about a rotational axis substantially perpendicular to the inner coil axes to generate a hypothetical surface which substantially encloses the inner coils. The outer coil rotates relative to the inner coils between a first position in which the outer coil axis is substantially parallel to the inner coil axes and the outer coil augments the magnetic field formed in one of the inner coils, and a second position 180[degree] from the first position, in which the augmented magnetic field is transferred into the other inner coil and reoriented 180[degree] from the original magnetic field. The magnetic field transfer device allows a magnetic field to be transferred between volumes with negligible work being required to rotate the outer coil with respect to the inner coils. 16 figs.

  4. Magnetic field transfer device and method

    DOEpatents

    Wipf, Stefan L.

    1990-01-01

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

  5. Fusion component design for the moving-ring field-reversed mirror reactor

    SciTech Connect

    Carlson, G.A.

    1981-01-28

    This partial report on the reactor design contains sections on the following: (1) burner section magnet system design, (2) plasma ring energy recovery, (3) vacuum system, (4) cryogenic system, (5) tritium flows and inventories, and (6) reactor design and layout. (MOW)

  6. The magnetic field of a permanent hollow cylindrical magnet

    NASA Astrophysics Data System (ADS)

    Reich, Felix A.; Stahn, Oliver; Müller, Wolfgang H.

    2015-12-01

    Based on the rational version of Muc(AXWELL)'s equations according to Tuc(RUESDELL) and Tuc(OUPIN) or KOVETZ, cf. (Kovetz in Electromagnetic theory, Oxford University Press, Oxford, 2000; Truesdell and Toupin in Handbuch der Physik, Bd. III/1, Springer, Berlin, pp 226-793; appendix, pp 794-858, 2000), we present, for stationary processes, a closed-form solution for the magnetic flux density of a hollow cylindrical magnet. Its magnetization is constant in axial direction. We consider Muc(AXWELL)'s equations in regular and singular points that are obtained by rational electrodynamics, adapted to stationary processes. The magnetic flux density is calculated analytically by means of a vector potential. We obtain a solution in terms of complete elliptic integrals. Therefore, numerical evaluation can be performed in a computationally efficient manner. The solution is written in dimensionless form and can easily be applied to cylinders of arbitrary shape. The relation between the magnetic flux density and the magnetic field is linear, and an explicit relation for the field is presented. With a slight modification the result can be used to obtain the field of a solid cylindrical magnet. The mathematical structure of the solution and, in particular, singularities are discussed.

  7. Dynamic signatures of quiet sun magnetic fields

    NASA Technical Reports Server (NTRS)

    Martin, S. F.

    1983-01-01

    The collision and disappearance of opposite polarity fields is observed most frequently at the borders of network cells. Due to observational limitations, the frequency, magnitude, and spatial distribution of magnetic flux loss have not yet been quantitatively determined at the borders or within the interiors of the cells. However, in agreement with published hypotheses of other authors, the disapperance of magnetic flux is speculated to be a consequence of either gradual or rapid magnetic reconnection which could be the means of converting magnetic energy into the kinetic, thermal, and nonthermal sources of energy for microflares, spicules, the solar wind, and the heating of the solar corona.

  8. In-plane magnetic field dependence of electric field-induced magnetization switching

    NASA Astrophysics Data System (ADS)

    Kanai, S.; Nakatani, Y.; Yamanouchi, M.; Ikeda, S.; Matsukura, F.; Ohno, H.

    2013-08-01

    Electric field-induced magnetization switching through magnetization precession is investigated as a function of in-plane component of external magnetic field for a CoFeB/MgO-based magnetic tunnel junction with perpendicular easy axis. The switching probability is an oscillatory function of the duration of voltage pulses and its magnitude and period depend on the magnitude of in-plane magnetic field. Experimental results are compared with simulated ones by using Landau-Lifshitz-Gilbert-Langevin equation, and possible factors determining the probability are discussed.

  9. The ring current.

    NASA Technical Reports Server (NTRS)

    Sugiura, M.

    1972-01-01

    The topology of delta-B (i.e., the observed scalar magnetic field intensity minus a scalar reference field intensity) in the magnetosphere has been established by the Rb magnetometer observations on OGO's 3 and 5. This delta-B topology provides a convenient framework, on the basis of which the complex features found by the earlier magnetic field observations made by Explorers 10, 12, 14, 26 and Electron 2 can be reinterpreted to fit a unified simple picture of the magnetospheric field distortions including the inflation of the equatorial magnetosphere by the ring current. It is proposed that the quiet-time ring current consists of two parts, the inner ring current imbedded deeply inside the plasmapause and the outer ring current flowing in the plasma sheet.

  10. Application of the Green's function method to some nonlinear problems of an electron storage ring. Part III. Beam-size enhancement due to the presence of nonlinear magnets in a ring

    SciTech Connect

    Kheifets, S.

    1983-01-01

    A perturbation method which allows one to find the distribution function and the beam size for a broad class of storage ring nonlinear problems is described in Part I of this work. In present note I apply this method to a particular problem. Namely, I want to evaluate an enhancement of the vertical beam size of a bunch due to the presence of the ring of nonlinear magnetic fields. The main part of the work deals with sextupole magnets. Formula for the beam size in the presence of octupole fields are also developed to the first order in the octupole strength, although octupole magnets are not widely used in present storage ring designs. This calculation is done mainly because the octupole field has the same symmetry as the beam-beam force for the head-on collision. This will give us the opportunity to compare the conduct of the bunch due to this two types of nonlinear kicks. The general terms of the applicability of the Green's function method is discussed in the first part of this work.

  11. Research of weak pulsed magnetic field system derived from the time, displacement, and static magnetic field.

    PubMed

    Zhao, Xiao-Dong; Qian, Zheng

    2015-10-01

    The accurate measurement of dynamic characteristics in weak magnetic sensors is urgently required as a greater number of applications for these devices are found. In this paper, a novel weak pulsed magnetic field system is presented. The underlying principle is to drive a permanent magnet passing another magnet rapidly, producing a pulsed weak magnetic field. The magnitude of the field can be adjusted by changing the velocity and distance between the two magnets. The standard value of the pulsed dynamic magnetic field can be traced back to the accurate measurement of time, displacement, and static magnetic field. In this study a detailed procedure for producing a pulse magnetic field system using the above method is outlined after which a theoretical analysis of the permanent magnet movement is discussed. Using the described apparatus a milli-second level pulse-width with a milli-Tesla magnetic field magnitude is used to study the dynamic characteristics of a giant magnetoresistance sensor. We conclude by suggesting possible improvements to the described apparatus. PMID:26520987

  12. Research of weak pulsed magnetic field system derived from the time, displacement, and static magnetic field

    NASA Astrophysics Data System (ADS)

    Zhao, Xiao-Dong; Qian, Zheng

    2015-10-01

    The accurate measurement of dynamic characteristics in weak magnetic sensors is urgently required as a greater number of applications for these devices are found. In this paper, a novel weak pulsed magnetic field system is presented. The underlying principle is to drive a permanent magnet passing another magnet rapidly, producing a pulsed weak magnetic field. The magnitude of the field can be adjusted by changing the velocity and distance between the two magnets. The standard value of the pulsed dynamic magnetic field can be traced back to the accurate measurement of time, displacement, and static magnetic field. In this study a detailed procedure for producing a pulse magnetic field system using the above method is outlined after which a theoretical analysis of the permanent magnet movement is discussed. Using the described apparatus a milli-second level pulse-width with a milli-Tesla magnetic field magnitude is used to study the dynamic characteristics of a giant magnetoresistance sensor. We conclude by suggesting possible improvements to the described apparatus.

  13. Magnetic Field Apparatus (MFA) Hardware Test

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  14. QCD quark condensate in external magnetic fields

    NASA Astrophysics Data System (ADS)

    Bali, G. S.; Bruckmann, F.; Endrődi, G.; Fodor, Z.; Katz, S. D.; Schäfer, A.

    2012-10-01

    We present a comprehensive analysis of the light condensates in QCD with 1+1+1 sea quark flavors (with mass-degenerate light quarks of different electric charges) at zero and nonzero temperatures of up to 190 MeV and external magnetic fields B<1GeV2/e. We employ stout smeared staggered fermions with physical quark masses and extrapolate the results to the continuum limit. At low temperatures we confirm the magnetic catalysis scenario predicted by many model calculations while around the crossover the condensate develops a complex dependence on the external magnetic field, resulting in a decrease of the transition temperature.

  15. Magnetic buoyancy and the escape of magnetic fields from stars

    NASA Technical Reports Server (NTRS)

    Parker, E. N.

    1984-01-01

    A loss of magnetic flux through the free surface of a star into the surrounding space has important implications for the generation of the field within the star. The present investigation is concerned with the physics of the escape of net azimuthal flux from a star. The obtained results are used as a basis for the interpretation of some recent observations of the detailed behavior of magnetic fields emerging through the surface of the sun. The buoyancy of an isolated horizontal magnetic flux tube beneath the surface of a star causes the tube to rise at a rate comparable to the Alfven speed. The necessary conditions for escape of the flux are considered along with aspects of magnetic buoyancy, and the conditions on the sun. It appears that the observed retraction of bipolar magnetic fields at the end of their life at the surface is the one phenomenon which requires dynamical intervention. Attention is given to known dynamical effects which suppress the buoyant rise of an azimuthal magnetic field.

  16. NIST Undulator Magnetic Field Characterization

    NASA Astrophysics Data System (ADS)

    Johnson, L. E.; Denbeaux, G.; Madey, J. M. J.; Straub, K. D.

    1997-05-01

    A 3.64 m undulator was constructed by the Brobeck Division of Maxwell Laboratories for FEL experiments at NIST in Washington, DC. The Duke University FEL Lab has since acquired the undulator for use as a soft x-ray source. We report on our effort to transform the undulator into a high performance soft x-ray insertion device through careful characterization of the existing magnet blocks, sorting and trimming.

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

    SciTech Connect

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

    1998-08-22

    The National High Magnetic Field Laboratory, funded by the National Science Foundation and other US federal Agencies, has in recent years built a wide range of magnetic fields, DC 25 to 35 Tesla, short pulse 50 - 60 Tesla, and quasi-continuous 60 Tesla. Future plans are to push the frontiers to 45 Tesla DC and 70 to 100 Tesla pulse. This user facility, is open for national and international users, and creates an excellent tool for materials research (metals, semiconductors, superconductors, biological systems ..., etc). Here we present results of a systematic study of the upper critical field of a novel superconducting material which is considered a promising candidate for the search for superconductivity beyond H{sub c2} as proposed by several new theories. These theories predict that superconductors with low carrier density can reenter the superconducting phase beyond the conventional upper critical field H{sub c2}. This negates the conventional thinking that superconductivity and magnetic fields are antagonistic.

  18. Critical Magnetic Field Determination of Superconducting Materials

    SciTech Connect

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

    2011-11-04

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

  19. Magnetic fields in early-type stars

    NASA Astrophysics Data System (ADS)

    Grunhut, Jason H.; Neiner, Coralie

    2015-10-01

    For several decades we have been cognizant of the presence of magnetic fields in early-type stars, but our understanding of their magnetic properties has recently (over the last decade) expanded due to the new generation of high-resolution spectropolarimeters (ESPaDOnS at CFHT, Narval at TBL, HARPSpol at ESO). The most detailed surface magnetic field maps of intermediate-mass stars have been obtained through Doppler imaging techniques, allowing us to probe the small-scale structure of these stars. Thanks to the effort of large programmes (e.g. the MiMeS project), we have, for the first time, addressed key issues regarding our understanding of the magnetic properties of massive (M > 8 M ⊙) stars, whose magnetic fields were only first detected about fifteen years ago. In this proceedings article we review the spectropolarimetric observations and statistics derived in recent years that have formed our general understanding of stellar magnetism in early-type stars. We also discuss how these observations have furthered our understanding of the interactions between the magnetic field and stellar wind, as well as the consequences and connections of this interaction with other observed phenomena.

  20. Fast Reconnection of Weak Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Zweibel, Ellen G.

    1998-01-01

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

  1. Magnetic field dissipation in converging flows

    NASA Astrophysics Data System (ADS)

    Melia, Fulvio; Kowalenko, Victor

    2001-11-01

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

  2. Electrostatic acceleration of helicon plasma using a cusped magnetic field

    SciTech Connect

    Harada, S.; Baba, T.; Uchigashima, A.; Iwakawa, A.; Sasoh, A.; Yokota, S.; Yamazaki, T.; Shimizu, H.

    2014-11-10

    The electrostatic acceleration of helicon plasma is investigated using an electrostatic potential exerted between the ring anode at the helicon source exit and an off-axis hollow cathode in the downstream region. In the downstream region, the magnetic field for the helicon source, which is generated by a solenoid coil, is modified using permanent magnets and a yoke, forming an almost magnetic field-free region surrounded by an annular cusp field. Using a retarding potential analyzer, two primary ion energy peaks, where the lower peak corresponds to the space potential and the higher one to the ion beam, are detected in the field-free region. Using argon as the working gas with a helicon power of 1.5 kW and a mass flow rate of 0.21 mg/s, the ion beam energy is on the order of the applied acceleration voltage. In particular, with an acceleration voltage lower than 150 V, the ion beam energy even exceeds the applied acceleration voltage by an amount on the order of the electron thermal energy at the exit of the helicon plasma source. The ion beam energy profile strongly depends on the helicon power and the applied acceleration voltage. Since by this method the whole working gas from the helicon plasma source can, in principle, be accelerated, this device can be applied as a noble electrostatic thruster for space propulsion.

  3. Wideband optical fiber magnetic field sensor

    SciTech Connect

    Martin, S.J.; Butler, M.A.

    1985-01-01

    The attractive features of fiber optic telemetry, including large signal bandwidth and electrical isolation, may be maintained while eliminating the disadvantages of fiber sensing. This can be accomplished by incorporating a sensing element having the appropriate characteristics. In this paper we will discuss the use of the semi-magnetic semiconductor Cd/sub 1-x/Mn/sub x/Te as a magnetic field sensing element taking into account the Verdet constant, the band gap, and the sensitivity of the material. The manner in which a magnetic semiconductor, such as Cd/sub 1-x/Mn/sub x/Te, could be used to implement a sensor is shown. This sensor system is particularly appropriate for measurement of rapidly varying magnetic fields in electrically noisy environments and may find application in the detection of intense RF fields. 5 refs., 5 figs.

  4. Slowly rotating pulsars and magnetic field decay

    NASA Astrophysics Data System (ADS)

    Han, J. L.

    1997-02-01

    Two dozen long period pulsars are separated from the swarm of ordinary pulsars by an obvious gap in the P versus Sd diagram (where Sd=log˙(P)+21.0), with a plausible upper boundary for ordinary pulsars. Possible pulsar evolutionary tracks are discussed to explain the diagram in terms of previously suggested scenarios of magnetic field decay. The (P-Sd) diagram is difficult to understand if there is no magnetic field decay during the active life of pulsars. However, if the magnetic fields of neutron stars decay exponentially, almost all slowly rotating pulsars must have been injected with a very long initial spin period of about 2 seconds, which seems impossible. Based on qualitative analyses, it is concluded that magnetic fields of neutron stars decay as a power-law, with a time scale related to the initial field strengths. The plausible boundary and the gap are suggested to naturally divide pulsars with distinct magnetic "genes", ie. pulsars which were born from strongly magnetized progenitors -- such as Bp stars, and pulsars born from normal massive stars. The possibility remains open that a fraction of slowly rotating pulsars were injected with long initial spin periods, while others would have a classical pulsar evolution history. It is suggested that PSR B1849+00 was born in the supernova remnant Kes-79 with an initial period of about 2 seconds.

  5. Magnetic fields in the solar photosphere.

    PubMed

    Bushby, Paul J

    2008-12-13

    Recent high-resolution observations of the surface of the Sun have revealed the fine structure of a vast array of complex photospheric magnetic features. Observations of these magnetic field structures have already greatly enhanced our theoretical understanding of the interactions between magnetic fields and turbulent convection, and future photospheric observations will inevitably present new theoretical challenges. In this review, I discuss recent progress that has been made in the modelling of photospheric magnetic fields. In particular, I focus upon the complex field structures that are observed within the umbrae and the penumbrae of sunspots. On a much smaller scale, I also discuss models of the highly localized magnetic field structures that are observed in less magnetically active regions of the photosphere. As the spatial resolution of telescopes has improved over the last few years, it has now become possible to observe these features in detail, and theoretical models can now describe much of this behaviour. In the last section of this review, I discuss some of the remaining unanswered questions. PMID:18812304

  6. Spin rotation by Earth's gravitational field in a “frozen-spin” ring

    NASA Astrophysics Data System (ADS)

    Orlov, Yuri; Flanagan, Eanna; Semertzidis, Yannis

    2012-10-01

    Detailed calculations of spin rotation by the Earth's gravitational field in a frozen-spin ring are presented in three different coordinate systems and used (a) to show that the systematic error caused by gravitation in a proposed electric dipole moment measurement can be unambiguously determined, and (b) to propose measuring the spin-gravity effect in a dedicated frozen-spin ring using electrons.

  7. Measurements of Photospheric and Chromospheric Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Lagg, Andreas; Lites, Bruce; Harvey, Jack; Gosain, Sanjay; Centeno, Rebecca

    2015-12-01

    The Sun is replete with magnetic fields, with sunspots, pores and plage regions being their most prominent representatives on the solar surface. But even far away from these active regions, magnetic fields are ubiquitous. To a large extent, their importance for the thermodynamics in the solar photosphere is determined by the total magnetic flux. Whereas in low-flux quiet Sun regions, magnetic structures are shuffled around by the motion of granules, the high-flux areas like sunspots or pores effectively suppress convection, leading to a temperature decrease of up to 3000 K. The importance of magnetic fields to the conditions in higher atmospheric layers, the chromosphere and corona, is indisputable. Magnetic fields in both active and quiet regions are the main coupling agent between the outer layers of the solar atmosphere, and are therefore not only involved in the structuring of these layers, but also for the transport of energy from the solar surface through the corona to the interplanetary space. Consequently, inference of magnetic fields in the photosphere, and especially in the chromosphere, is crucial to deepen our understanding not only for solar phenomena such as chromospheric and coronal heating, flares or coronal mass ejections, but also for fundamental physical topics like dynamo theory or atomic physics. In this review, we present an overview of significant advances during the last decades in measurement techniques, analysis methods, and the availability of observatories, together with some selected results. We discuss the problems of determining magnetic fields at smallest spatial scales, connected with increasing demands on polarimetric sensitivity and temporal resolution, and highlight some promising future developments for their solution.

  8. Secondary resonance magnetic force microscopy using an external magnetic field for characterization of magnetic thin films

    NASA Astrophysics Data System (ADS)

    Liu, Dongzi; Mo, Kangxin; Ding, Xidong; Zhao, Liangbing; Lin, Guocong; Zhang, Yueli; Chen, Dihu

    2015-09-01

    A bimodal magnetic force microscopy (MFM) that uses an external magnetic field for the detection and imaging of magnetic thin films is developed. By applying the external modulation magnetic field, the vibration of a cantilever probe is excited by its magnetic tip at its higher eigenmode. Using magnetic nanoparticle samples, the capacity of the technique which allows single-pass imaging of topography and magnetic forces is demonstrated. For the detection of magnetic properties of thin film materials, its signal-to-noise ratio and sensitivity are demonstrated to be superior to conventional MFM in lift mode. The secondary resonance MFM technique provides a promising tool for the characterization of nanoscale magnetic properties of various materials, especially of magnetic thin films with weak magnetism.

  9. Electric/magnetic field sensor

    DOEpatents

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

    2009-01-27

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

  10. A novel condenser for EUV lithography ring-field projection optics

    SciTech Connect

    Chapman, H; Nugent, K A

    1999-07-15

    A condenser for a ring-field extreme ultra-violet (EUV) projection lithography camera is presented. The condenser consists of a gently undulating mirror, that we refer to as a ripple plate, and which is illuminated by a collimated beam at grazing incidence. The light is incident along the ripples rather than across them, so that the incident beam is reflected onto a cone and subsequently focused on to the arc of the ring field. A quasistationary illumination is achieved, since any one field point receives light from points on the ripples, which are distributed throughout the condenser pupil. The design concept can easily be applied to illuminate projection cameras with various ring-field and numerical aperture specifications. Ray-tracing results are presented of a condenser for a 0.25 NA EUV projection camera.

  11. Physical studies of heterometallic rings: an ideal system for studying magnetically-coupled systems.

    PubMed

    Timco, Grigore A; McInnes, Eric J L; Winpenny, Richard E P

    2013-02-21

    Heterometallic rings of general formula [Cat][M(7)M'F(8)(O(2)C(t)Bu)(8)] (M = a trivalent metal, M' = a divalent metal, cat = a secondary ammonium cation, caesium or rubidium) contain an octagon of metal centres with each metal-metal edge bridged by a fluoride and two carboxylates. The rings when M = Cr(III) give remarkably beautiful EPR and INS spectra, and allow us to examine new techniques. Use of these techniques allows us to study the models used to describe magnetic behaviour in exchange coupled systems. In this tutorial review we discuss the two main approaches to modelling magnetic data - the strong exchange limit and the microscopic Hamiltonian approaches, aiming to explain the major differences between the two approaches. We also describe some more esoteric measurements and theories. PMID:22990593

  12. Passive magnetic shielding in static gradient fields

    NASA Astrophysics Data System (ADS)

    Bidinosti, C. P.; Martin, J. W.

    2014-04-01

    The effect of passive magnetic shielding on dc magnetic field gradients imposed by both external and internal sources is studied for two idealized shield models: concentric spherical and infinitely-long cylindrical shells of linear material. It is found that higher-order multipoles of an externally applied magnetic field are always shielded progressively better for either geometry by a factor related to the order of the multipole. In regard to the design of internal coil systems, we determine reaction factors for the general multipole field and provide examples of how one can take advantage of the coupling of the coils to the innermost shell to optimize the uniformity of the field. Furthermore, we provide formulae relevant to active magnetic compensation systems which attempt to stabilize the interior fields by sensing and cancelling the exterior fields close to the outermost shell. Overall this work provides a comprehensive framework that is useful for the analysis and optimization of dc magnetic shields, serving as a theoretical and conceptual design guide as well as a starting point and benchmark for finite-element analysis.

  13. Variability in Martian magnetic field topology

    NASA Astrophysics Data System (ADS)

    Brain, D. A.; Halekas, J. S.; Eastwood, J. P.; Ulusen, D.; Lillis, R. J.

    2013-12-01

    Martian crustal magnetic fields form localized mini-magnetosphere structures that extend in some regions well above the Martian ionosphere, interacting directly with the draped external interplanetary magnetic field (IMF). In some regions the crustal magnetic field lines are closed, locally shielding the ionosphere from external plasma. In other locations the crustal field lines are open, allowing exchange of plasma between the ionosphere and the surrounding plasma interaction region. The average magnetic topology as a function of geographic location has been mapped previously, using ~7 years of Mars Global Surveyor electron observations recorded at constant altitude and local time. In this previous work, pitch angle distributions of suprathermal electrons were examined for the presence of loss cones to determine whether field lines were open or closed. Here we apply the same technique to describe how magnetic topology varies with four external drivers: solar wind pressure, IMF orientation, solar EUV flux, and Martian season. We see that some locations on Mars change topology frequently depending upon external conditions, while others have a relatively static field topology.

  14. DC-magnetic field vector measurement

    NASA Technical Reports Server (NTRS)

    Schmidt, R.

    1981-01-01

    A magnetometer experiment was designed to determine the local magnetic field by measuring the total of the Earth's magnetic field and that of an unknown spacecraft. The measured field vector components are available to all onboard experiments via the Spacelab command and data management system. The experiment consists of two parts, an electronic box and the magnetic field sensor. The sensor includes three independent measuring flux-gate magnetometers, each measuring one component. The physical background is the nonlinearity of the B-H curve of a ferrite material. Two coils wound around a ferrite rod are necessary. One of them, a tank coil, pumps the ferrite rod at approximately 20 kilohertz. As a consequence of the nonlinearity, many harmonics can be produced. The second coil (i.e., the detection coil) resonates to the first harmonic. If an unknown dc or low-frequency magnetic field exists, the amplitude of the first harmonic is a measure for the unknown magnetic field. The voltages detected by the sensors are to be digitized and transferred to the command and data management system.

  15. Galactic magnetic fields and hierarchical galaxy formation

    NASA Astrophysics Data System (ADS)

    Rodrigues, L. F. S.; Shukurov, A.; Fletcher, A.; Baugh, C. M.

    2015-07-01

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

  16. UNDERSTANDING THE GEOMETRY OF ASTROPHYSICAL MAGNETIC FIELDS

    SciTech Connect

    Broderick, Avery E.; Blandford, Roger D.

    2010-08-01

    Faraday rotation measurements have provided an invaluable technique for probing the properties of astrophysical magnetized plasmas. Unfortunately, typical observations provide information only about the density-weighted average of the magnetic field component parallel to the line of sight. As a result, the magnetic field geometry along the line of sight, and in many cases even the location of the rotating material, is poorly constrained. Frequently, interpretations of Faraday rotation observations are dependent upon underlying models of the magnetic field being probed (e.g., uniform, turbulent, equipartition). However, we show that at sufficiently low frequencies, specifically below roughly 13(RM/1 rad m{sup -2}){sup 1/4}(B/1 G){sup 1/2} MHz, the character of Faraday rotation changes, entering what we term the 'super-adiabatic regime' in which the rotation measure (RM) is proportional to the integrated absolute value of the line-of-sight component of the field. As a consequence, comparing RMs at high frequencies with those in this new regime provides direct information about the geometry of the magnetic field along the line of sight. Furthermore, the frequency defining the transition to this new regime, {nu}{sub SA}, depends directly upon the local electron density and magnetic field strength where the magnetic field is perpendicular to the line of sight, allowing the unambiguous distinction between Faraday rotation within and in front of the emission region. Typical values of {nu}{sub SA} range from 10 kHz (below the ionospheric cutoff, but above the heliospheric cutoff) to 10 GHz, depending upon the details of the Faraday rotating environment. In particular, for resolved active galactic nuclei, including the black holes at the center of the Milky Way (Sgr A*) and M81, {nu}{sub SA} ranges from roughly 10 MHz to 10 GHz, and thus can be probed via existing and up-coming ground-based radio observatories.

  17. Measurement of the magnetic field of small magnets with a smartphone: a very economical laboratory practice for introductory physics courses

    NASA Astrophysics Data System (ADS)

    Arribas, Enrique; Escobar, Isabel; Suarez, Carmen P.; Najera, Alberto; Beléndez, Augusto

    2015-11-01

    In this work, we propose an inexpensive laboratory practice for an introductory physics course laboratory for any grade of science and engineering study. This practice was very well received by our students, where a smartphone (iOS, Android, or Windows) is used together with mini magnets (similar to those used on refrigerator doors), a 20 cm long school rule, a paper, and a free application (app) that needs to be downloaded and installed that measures magnetic fields using the smartphone’s magnetic field sensor or magnetometer. The apps we have used are: Magnetometer (iOS), Magnetometer Metal Detector, and Physics Toolbox Magnetometer (Android). Nothing else is needed. Cost of this practice: free. The main purpose of the practice is that students determine the dependence of the component x of the magnetic field produced by different magnets (including ring magnets and sphere magnets). We obtained that the dependency of the magnetic field with the distance is of the form x-3, in total agreement with the theoretical analysis. The secondary objective is to apply the technique of least squares fit to obtain this exponent and the magnetic moment of the magnets, with the corresponding absolute error.

  18. Magnetic nanoparticles for applications in oscillating magnetic field

    SciTech Connect

    Peeraphatdit, Chorthip

    2010-12-15

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

  19. Probing Magnetic Fields with GALFACTS

    NASA Astrophysics Data System (ADS)

    George, S. J.; Stil, J. M.; Andrecut, M.; Taylor, A. R.

    2012-09-01

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

  20. Hyperon bulk viscosity in strong magnetic fields

    SciTech Connect

    Sinha, Monika; Bandyopadhyay, Debades

    2009-06-15

    We study the bulk viscosity of neutron star matter including {lambda} hyperons in the presence of quantizing magnetic fields. Relaxation time and bulk viscosity due to both the nonleptonic weak process involving {lambda} hyperons and direct Urca processes are calculated here. In the presence of a strong magnetic field of 10{sup 17} G, the hyperon bulk viscosity coefficient is reduced, whereas bulk viscosity coefficients due to direct Urca processes are enhanced compared with their field free cases when many Landau levels are populated by protons, electrons, and muons.

  1. Evolution of weak solar magnetic fields

    NASA Technical Reports Server (NTRS)

    Zirin, H.

    1985-01-01

    The present evaluation of Big Bear videomagnetograph studies of the evolution of weak solar magnetic fields notes that the general weak network fields are the remnants of ephemeral regions which also play a role in the field diffusion as proposed by Marsh (1978). The intranetwork elements show a shorter lifetime and much more rapid motion than the network elements. They are in some cases noted to stream into existing network elements and may merge to form new elements, but need also show no preferential motion to the network edges. There seem to be fewer ephemeral regions in magnetically active areas.

  2. Primordial magnetic fields and nonlinear electrodynamics

    SciTech Connect

    Kunze, Kerstin E.

    2008-01-15

    The creation of large scale magnetic fields is studied in an inflationary universe where electrodynamics is assumed to be nonlinear. After inflation ends electrodynamics becomes linear and thus the description of reheating and the subsequent radiation dominated stage are unaltered. The nonlinear regime of electrodynamics is described by Lagrangians having a power-law dependence on one of the invariants of the electromagnetic field. It is found that there is a range of parameters for which primordial magnetic fields of cosmologically interesting strengths can be created.

  3. On deflection fields, weak-focusing and strong-focusing storage rings for polar molecules.

    PubMed

    de Nijs, Adrian J; Bethlem, Hendrick L

    2011-11-14

    In this paper, we analyze electric deflection fields for polar molecules in terms of a multipole expansion and derive a simple but rather insightful expression for the force on the molecules. Ideally, a deflection field exerts a strong, constant force in one direction, while the force in the other directions is zero. We show how, by a proper choice of the expansion coefficients, this ideal can be best approximated. We present a design for a practical electrode geometry based on this analysis. By bending such a deflection field into a circle, a simple storage ring can be created; the direct analog of a weak-focusing cyclotron for charged particles. We show that for realistic parameters a weak-focusing ring is only stable for molecules with a very low velocity. A strong-focusing (alternating-gradient) storage ring can be created by arranging many straight deflection fields in a circle and by alternating the sign of the hexapole term between adjacent deflection fields. The acceptance of this ring is numerically calculated for realistic parameters. Such a storage ring might prove useful in experiments looking for an EDM of elementary particles. PMID:21979152

  4. Magnetic microchains and microswimmers in an oscillating magnetic field.

    PubMed

    Ido, Yasushi; Li, Yan-Hom; Tsutsumi, Hiroaki; Sumiyoshi, Hirotaka; Chen, Ching-Yao

    2016-01-01

    Superparamagnetic micro-bead chains and microswimmers under the influence of an oscillating magnetic field are studied experimentally and numerically. The numerical scheme composed of the lattice Boltzmann method, immersed boundary method, and discrete particle method based on the simplified Stokesian dynamics is applied to thoroughly understand the interaction between the micro-bead chain (or swimmer), the oscillating magnetic field, and the hydrodynamics drag. The systematic experiments and simulations demonstrated the behaviors of the microchains and microswimmers as well as the propulsive efficiencies of the swimmers. The effects of key parameters, such as field strengths, frequency, and the lengths of swimmer, are thoroughly analyzed. The numerical results are compared with the experiments and show good qualitative agreements. Our results proposed an efficient method to predict the motions of the reversible magnetic microdevices which may have extremely valuable applications in biotechnology. PMID:26858808

  5. Observation of Magnetic Resonances in Electron Clouds in a Positron Storage Ring

    SciTech Connect

    Pivi, M.T.F.; Ng, J.S.T.; Cooper, F.; Kharakh, D.; King, F.; Kirby, R.E.; Kuekan, B.; Spencer, Cherrill M.; Raubenheimer, T.O.; Wang, L.F.; /SLAC

    2011-08-24

    The first experimental observation of magnetic resonances in electron clouds is reported. The resonance was observed as a modulation in cloud intensity for uncoated as well as TiN-coated aluminum surfaces in the positron storage ring of the PEP-II collider at SLAC. Electron clouds frequently arise in accelerators of positively charged particles, and severely impact the machines performance. The TiN coating was found to be an effective remedy, reducing the cloud intensity by three orders of magnitude.

  6. The identification of hot electron rings in spindle cusp using a magnetic dipole analyzer

    SciTech Connect

    Leal-Quiros, E.; Prelas, M.A. . Dept. of Nuclear Engineering)

    1991-12-01

    This paper reports on a magnetic dipole analyzer that has been built and used to measure fundamental parameters on the M4X, an experimental mirror machine with a spindle cusp and simple mirror modes of operation. A result using the M4X is the direct observation of the dimagnetic effect during the formation of hot electron rings in the spindle cusp configuration using electron cyclotron resonance heating.

  7. Intermittent character of interplanetary magnetic field fluctuations

    SciTech Connect

    Bruno, Roberto; Carbone, Vincenzo; Chapman, Sandra; Hnat, Bogdan; Noullez, Alain; Sorriso-Valvo, Luca

    2007-03-15

    Interplanetary magnetic field magnitude fluctuations are notoriously more intermittent than velocity fluctuations in both fast and slow wind. This behavior has been interpreted in terms of the anomalous scaling observed in passive scalars in fully developed hydrodynamic turbulence. In this paper, the strong intermittent nature of the interplanetary magnetic field is briefly discussed comparing results performed during different phases of the solar cycle. The scaling properties of the interplanetary magnetic field magnitude show solar cycle variation that can be distinguished in the scaling exponents revealed by structure functions. The scaling exponents observed around the solar maximum coincide, within the errors, to those measured for passive scalars in hydrodynamic turbulence. However, it is also found that the values are not universal in the sense that the solar cycle variation may be reflected in dependence on the structure of the velocity field.

  8. Magnetic fields during high redshift structure formation

    NASA Astrophysics Data System (ADS)

    Schleicher, D. R. G.; Latif, M.; Schober, J.; Schmidt, W.; Bovino, S.; Federrath, C.; Niemeyer, J.; Banerjee, R.; Klessen, R. S.

    2013-06-01

    We explore the amplification of magnetic fields in the high-redshift Universe. For this purpose, we perform high-resolution cosmological simulations following the formation of primordial halos with {˜ 107} M_⊙, revealing the presence of turbulent structures and complex morphologies at resolutions of at least 32 cells per Jeans length. Employing a turbulence subgrid-scale model, we quantify the amount of unresolved turbulence and show that the resulting turbulent viscosity has a significant impact on the gas morphology, suppressing the formation of low-mass clumps. We further demonstrate that such turbulence implies the efficient amplification of magnetic fields via the small-scale dynamo. We discuss the properties of the dynamo in the kinematic and non-linear regime, and explore the resulting magnetic field amplification during primordial star formation. We show that field strengths of ˜ 10-5 G can be expected at number densities of ˜ 5 cm-3.

  9. Magnetic field dissipation in D-sheets

    NASA Technical Reports Server (NTRS)

    Burlaga, L. F.; Scudder, J. D.

    1973-01-01

    The effects of magnetic field annihilation at a tangential or rotational discontinuity in a resistive plasma are examined. The magnetic field intensity profile depends on (1) the field intensities far from the current sheet (+ and - infinity), (2) the angle between the two intensities, and (3) the electrical resistivity. For a tangential discontinuity, the theory predicts a depression in B, centered at the discontinuity, and it predicts a monotonic transition. The theory provides satisfactory fits to the magnetic field intensity and proton temperature profiles observed for two extremely broad D-sheets in the solar wind. Assuming a diffusion time 10 days, one obtains effective resistivities or approximately = 3 x 10 to the 12th power and 2 x 10 to the 13th power emu for the D-sheets. Either resistivity at directional discontinuities is much lower than 10 to the 12th power emu or annihilation does not always occur at discontinuities.

  10. Magnetic field generation from cosmological perturbations.

    PubMed

    Takahashi, Keitaro; Ichiki, Kiyotomo; Ohno, Hiroshi; Hanayama, Hidekazu

    2005-09-16

    In this Letter, we discuss the generation of magnetic field from cosmological perturbations. We consider the evolution of three component plasma (electron, proton, and photon) evaluating the collision term between electrons and photons up to the second order. The collision term is shown to induce electric current, which then generates magnetic field. There are three contributions, two of which can be evaluated from the first-order quantities, while the other one is fluid vorticity, which is purely second order. We estimate the magnitudes of the former contributions and show that the amplitude of the produced magnetic field is about approximately 10(-19) G at 10 Mpc comoving scale at the decoupling. Compared to astrophysical and inflationary mechanisms for seed-field generation, our study suffers from much less ambiguities concerning unknown physics and/or processes. PMID:16197062

  11. Magnetic Fields at the Center of Coils

    NASA Astrophysics Data System (ADS)

    Binder, Philippe; Hui, Kaleonui; Goldman, Jesse

    2014-12-01

    In this note we synthesize and extend expressions for the magnetic field at the center of very short and very long current-carrying coils. Elementary physics textbooks present the following equation for the magnetic field inside a very long current-carrying coil (solenoid): Bsol=μ0(N/L)I, (1) where I is the current, N the number of windings, and L the coil length. It is obtained directly from Ampère's law, ignores end effects (hence it assumes an infinite coil), and is valid over the entire cross-section of the coil. The field is in the axial direction and it follows the right-hand rule convention. For N superposed loops of radius R each carrying current I, the multi-loop magnetic field at the center is given by Bml=μ0(N/2 R) I. (2)

  12. Magnetic fields in superconducting neutron stars.

    PubMed

    Lander, S K

    2013-02-15

    The interior of a neutron star is likely to be predominantly a mixture of superfluid neutrons and superconducting protons. This results in the quantization of the star's magnetic field into an array of thin flux tubes, producing a macroscopic force very different from the Lorentz force of normal matter. We show that in an axisymmetric superconducting equilibrium the behavior of a magnetic field is governed by a single differential equation. Solving this, we present the first self-consistent superconducting neutron star equilibria with poloidal and mixed poloidal-toroidal fields and also give the first quantitative results for the corresponding magnetically induced distortions to the star. The poloidal component is dominant in all our configurations. We suggest that the transition from normal to superconducting matter in a young neutron star may cause a large-scale field rearrangement. PMID:25166363

  13. STRESS GERMINATION RING TEST WITH IIRB AND FIELD VALIDATION IN MICHIGAN

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This test was conducted to validate field emergence on lines selected by European breeding companies for a ‘ring test’ to evaluate the water germination stress test developed at East Lansing for predicting relative field emergence. Water and hydrogen peroxide germination tests were conducted prior t...

  14. Magnetic field data on Fermilab Energy-Saver quadrupoles

    SciTech Connect

    Schmidt, E.E.; Brown, B.C.; Cooper, W.E.; Fisk, H.E.; Gross, D.A.; Hanft, R.; Ohnuma, S.; Turkot, F.T.

    1983-03-01

    The Fermilab Energy Saver/Doubler (Tevatron) accelerator contains 216 superconducting quadrupole magnets. Before installation in the Tevatron ring, these magnets plus an additional number of spares were extensively tested at the Fermilab Magnet Test Facility (MTF). Details on the results of the tests are presented here.

  15. Ring dykes as partially captured inclined sheets: insights from field observations and numerical modelling

    NASA Astrophysics Data System (ADS)

    Browning, John; Gudmundsson, Agust

    2014-05-01

    The subsurface structure of caldera-bounding ring faults remains a contentious issue. Analogue models provide useful insights into an underlying fault structure; however, results are commonly benchmarked only by near-surface observations and geophysical interpretations. Here we present field observations of a deeply eroded and uniquely well exposed section of caldera ring fault in a Tertiary central volcano in south-western Iceland. The Hafnarfjall ring fault represents the outermost fault complex of an elliptical caldera with an original diameter of approximately 5 km. Vertical displacement is estimated to be > 300 m on the steeply inward-dipping ring fault. Field observations (presented here) of the exposed section of the ring fault, however, show that the fault does not exhibit a constant dip. Hafnarfjall is a predominantly basaltic edifice made of many hundreds of lava flows, although thin layers of tuff and intrusions of more evolved magmas are also observed. These layers have contrasting mechanical properties; therefore local heterogeneities within the original edifice may have altered the stress field enough to influence the propagation of ring faults during collapse. The lava pile on the outer margins of the caldera dips shallowly to the southeast. Within the caldera, dips increase dramatically toward the centre of subsidence and, furthermore, increase with depth. Several thin (< 1 m) dykes occupy an approximately 5 m section within the ring fault; this region is interpreted to have once acted mechanically as the fault core with a lower stiffness or Young's modulus than the surrounding host rock. Many faults which have been active over an extended period develop a damage zone around the fault core; this is a zone of high fracture frequency which is generally stiffer than the core but softer or more compliant than the surrounding host rock. We observe a number of inclined sheets, presumably originating from the shallow magma chamber within the caldera margin, which become either arrested or deflected upon contact with the ring fault. Sheets that deflect into the fault may be wrongly interpreted at the surface as a ring dyke directly connected with extrusion of magma during collapse caldera formation. Using the commercial numerical modelling software COMSOL, we offer a mechanical explanation for the deflection of inclined sheets into sub-vertical dykes at a mechanically stratified fault damage zone and core. A model is proposed whereby ring faults can act as a barrier for the propagation of inclined sheets away from a magma chamber within the caldera. Furthermore, stress field homogenisation within the fault core can promote vertical dyke propagation, which offers a further explanation for the prevalence of renewed volcanism along caldera ring faults.

  16. DNA-assembled nanoparticle rings exhibit electric and magnetic resonances at visible frequencies.

    PubMed

    Roller, Eva-Maria; Khorashad, Larousse Khosravi; Fedoruk, Michael; Schreiber, Robert; Govorov, Alexander O; Liedl, Tim

    2015-02-11

    Metallic nanostructures can be used to manipulate light on the subwavelength scale to create tailored optical material properties. Next to electric responses, artificial optical magnetism is of particular interest but difficult to achieve at visible wavelengths. DNA-self-assembly has proved to serve as a viable method to template plasmonic materials with nanometer precision and to produce large quantities of metallic objects with high yields. We present here the fabrication of self-assembled ring-shaped plasmonic metamolecules that are composed of four to eight single metal nanoparticles with full stoichiometric and geometric control. Scattering spectra of single rings as well as absorption spectra of solutions containing the metamolecules are used to examine the unique plasmonic features, which are compared to computational simulations. We demonstrate that the electric and magnetic plasmon resonance modes strongly correlate with the exact shape of the structures. In particular, our computations reveal the magnetic plasmons only for particle rings of broken symmetries, which is consistent with our experimental data. We stress the feasibility of DNA self-assembly as a method to create bulk plasmonic materials and metamolecules that may be applied as building blocks in plasmonic devices. PMID:25611357

  17. DNA-Assembled Nanoparticle Rings Exhibit Electric and Magnetic Resonances at Visible Frequencies

    PubMed Central

    2015-01-01

    Metallic nanostructures can be used to manipulate light on the subwavelength scale to create tailored optical material properties. Next to electric responses, artificial optical magnetism is of particular interest but difficult to achieve at visible wavelengths. DNA-self-assembly has proved to serve as a viable method to template plasmonic materials with nanometer precision and to produce large quantities of metallic objects with high yields. We present here the fabrication of self-assembled ring-shaped plasmonic metamolecules that are composed of four to eight single metal nanoparticles with full stoichiometric and geometric control. Scattering spectra of single rings as well as absorption spectra of solutions containing the metamolecules are used to examine the unique plasmonic features, which are compared to computational simulations. We demonstrate that the electric and magnetic plasmon resonance modes strongly correlate with the exact shape of the structures. In particular, our computations reveal the magnetic plasmons only for particle rings of broken symmetries, which is consistent with our experimental data. We stress the feasibility of DNA self-assembly as a method to create bulk plasmonic materials and metamolecules that may be applied as building blocks in plasmonic devices. PMID:25611357

  18. Whistler Modes with Wave Magnetic Fields Exceeding the Ambient Field

    SciTech Connect

    Stenzel, R.L.; Urrutia, J.M.; Strohmaier, K.D.

    2006-03-10

    Whistler-mode wave packets with fields exceeding the ambient dc magnetic field have been excited in a large, high electron-beta plasma. The waves are induced with a loop antenna with dipole moment either along or opposite to the dc field. In the latter case the excited wave packets have the topology of a spheromak but are propagating in the whistler mode along and opposite to the dc magnetic field. Field-reversed configurations with net zero helicity have also been produced. The electron magnetohydrodynamics fields are force free, have wave energy density exceeding the particle energy density, and propagate stably at subelectron thermal velocities through a nearly uniform stationary ion density background.

  19. A diode for accelerating hydrogen nuclides with electron conductivity suppressed by an internal ring magnet

    NASA Astrophysics Data System (ADS)

    Shikanov, A. E.; Vovchenko, E. D.; Kozlovskii, K. I.; Shatokhin, V. L.

    2015-05-01

    We present new experimental data on the acceleration of deuterons in a small-size magnetically insulated diode. Plasma containing deuterons was created at the anode during irradiation of a TiD target by a focused laser beam with a wavelength of 1.06 μm. The accelerating voltage pulse was formed by an Arkadiev-Marx generator. A circular cathode was arranged symmetrically relative to the anode and represented a permanent ring magnet with an inner radius not exceeding 0.02 m and a magnetic induction of up to 0.4 T at the center, which ensured magnetic insulation of the accelerating gap. The experiments showed that the current of accelerated deuterons with energies of up to 300 eV can reach a level of 0.5 kA at pulse durations of ≤0.5 μs.

  20. AMPTE/CCE magnetic field studies of the September 4, 1984 storm

    NASA Technical Reports Server (NTRS)

    Potemra, T. A.; Zanetti, L. J.; Acuna, M. H.

    1985-01-01

    The AMPTE/CCE (active magnetospheric particle tracer explorer/charge composition explorer) magnetic-field observations acquired during the September 4, 1984 geomagnetic storm are described. The observations are used to determine magnetospheric regions and boundaries and are also used as the primary index of the development, evolution, and distribution of the ring current. The results of an analysis of the observations are presented. It is shown that a magnetic compression observed inside the magnetosphere by CCE and outside by ISEE-2 is interpreted as a sudden impulse. From an estimation of magnetopause normals at each crossing, it is concluded that the magnetic variations that occur are due to a contraction and expansion of the entire magnetosphere. Local magnetic-field depressions are observed during two inbound dusk passes, confirming that the ring current never developed in the dawn sector.