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Sample records for field dipole magnets

  1. 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

  2. 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.

  3. Magnetic Field of a Dipole and the Dipole-Dipole Interaction

    ERIC Educational Resources Information Center

    Kraftmakher, Yaakov

    2007-01-01

    With a data-acquisition system and sensors commercially available, it is easy to determine magnetic fields produced by permanent magnets and to study the dipole-dipole interaction for different separations and angular positions of the magnets. For sufficiently large distances, the results confirm the 1/R[superscript 3] law for the magnetic field…

  4. Variable-field permanent magnet dipole

    SciTech Connect

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

    1993-10-01

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

  5. Single-layer high field dipole magnets

    SciTech Connect

    Vadim V. Kashikhin and Alexander V. Zlobin

    2001-07-30

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

  6. 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.

  7. Plasma expansion in the presence of a dipole magnetic field

    SciTech Connect

    Winske, D.; Omidi, N.

    2005-07-15

    Simulations of the initial expansion of a plasma injected into a stationary magnetized background plasma in the presence of a dipole magnetic field are carried out in two dimensions with a kinetic ion, massless fluid electron (hybrid) electromagnetic code. For small values of the magnetic dipole, the injected ions have large gyroradii compared to the scale length of the dipole field and are essentially unmagnetized. As a result, these ions expand, excluding the ambient magnetic field and plasma to form a diamagnetic cavity. However, for stronger magnetic dipoles, the ratio of the gyroradii of the injected ions to the dipole field scale length is small so that they remain magnetized, and hence trapped in the dipole field, as they expand. The trapping and expansion then lead to additional plasma currents and resulting magnetic fields that not only exclude the background field but also interact with the dipole field in a more complex manner that stretches the closed dipole field lines. A criterion to distinguish between the two regimes is derived and is then briefly discussed in the context of applying the results to the plasma sail scheme for the propulsion of small spacecraft in the solar wind.

  8. Magnetic field homogeneity perturbations in finite Halbach dipole magnets.

    PubMed

    Turek, Krzysztof; Liszkowski, Piotr

    2014-01-01

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

  9. Magnetic-field considerations in superferric dipole

    NASA Astrophysics Data System (ADS)

    Snowdon, S. C.

    1983-03-01

    Iron dominated magnets are characterized in the limit of infinite permeability by a pole shape that is a magnetic equipotential. Deviations from this ideal because of finite permeability are associated with differences in path length, local saturation, flux concentration in slotted pole if crenellation is used, and sub surface voids. For moderate field levels the variation in flux path length throughout the iron lowers the magnetic potential on the iron surface more for the longer paths. As the excitation increases, the permeability is lowered in regions of high flux density. Crenellation in this region offers some degree of control over the permeability by concentrating the flux. To a lesser degree sub surface voids can be used to control the reluctance of a flux path. The net result suggests that the shape of the effective air gap can be adjusted to be a magnetic equipotential sensibly equivalent to the ideal pole shape for infinite permeability.

  10. Magnetic field properties of Fermilab Energy-Saver dipoles

    SciTech Connect

    Hanft, R.; Brown, B.C.; Cooper, W.E.; Gross, D.A.; Michelotti, L.; Schmidt, E.E.; Turkot, F.

    1983-03-01

    At Fermilab we have operated a production line for the fabrication of 901 21 foot long superconducting dipoles for use in the Energy Saver/Doubler. At any one time 772 of these dipoles are installed in the accelerator and 62 in beamlines; the remainder are spares. Magnetic field data are now available for most of these dipoles; in this paper we present some of these data which show that we have been able to maintain the necessary consistency in field quality throughout the production process. Specifically we report harmonic field coefficients, showing that the mechanical design permits substantial reduction of the magnitudes of the normal and skew quadrupole harmonic coefficients; field shape profiles; integral field data; and field angle data.

  11. SKEW QUADRUPOLES IN RHIC DIPOLE MAGNETS AT HIGH FIELDS.

    SciTech Connect

    JAIN, A.; GUPTA, P.; THOMPSON, P.; WANDERER, P.

    1995-06-11

    In the RHIC arc dipoles, the center of the cold mass lies above the center of the cryostat. At the maximum design field, the magnetic flux lines leak through the yoke to the asymmetrically located cryostat, which provides an additional return path. This introduces a systematic top-bottom asymmetry leading to a skew quadrupole term at high fields. A similar asymmetry is also created by any difference in weights of the upper and the lower yoke halves. Data from measurements of several RHIC dipoles are presented to study this effect. In the current production series of the RDIC dipoles, an attempt is made to compensate the effect of the cryostat by an asymmetry in the iron yoke. Seven dipoles with this type of yoke have been cold tested, and show a reduced saturation in the skew quadrupole term, as expected.

  12. Part II: magnetic field produced by a current dipole.

    PubMed

    Cohen, D; Hosaka, H

    1976-01-01

    To understand the MCG, electrical models of the heart must be used in which the basic building-block is usually the current dipole. The dipole's magnetic field is generally made up of two parts: 1. the contribution by the dipole element itself, which is mathematically simple; 2. the contribution by the current generated in the volume conductor by the dipole, which is complicated and depends on the boundaries; for special boundaries this contribution is zero to Bz, the component of magnetic field which is normal to the boundary. This applies to the boundaries of the semi-infinite volume conductor, the infinite slab, and the sphere. This property allows great simplification in solving the magnetic forward and inverse problems. Because of its importance, it is proven with electrolytic tank experiments. Based on this property, a method is presented for estimating the presence of those dipole combinations which produce a suppressed surface potential; it consists of a visual examination of an "arrow" display of Bz.

  13. A spatio-temporal dipole simulation of gastrointestinal magnetic fields.

    PubMed

    Bradshaw, L Alan; Myers, Andrew; Wikswo, John P; Richards, William O

    2003-07-01

    We have developed a simulation of magnetic fields from gastrointestinal (GI) smooth muscle. Current sources are modeled as depolarization dipoles at the leading edge of the isopotential ring of electrical control activity (ECA) that is driven by coupled cells in the GI musculature. The dipole moment resulting from the known transmembrane potential distribution varies in frequency and phase depending on location in the GI tract. Magnetic fields in a homogeneous volume conductor are computed using the law of Biot-Savart and characterized by their spatial and temporal variation. The model predicts that the natural ECA frequency gradient may be detected by magnetic field detectors outside the abdomen. It also shows that propagation of the ECA in the gastric musculature results in propagating magnetic field patterns. Uncoupling of gastric smooth muscle cells disrupts the normal magnetic field propagation pattern. Intestinal ischemia, which has been experimentally characterized by lower-than-normal ECA frequencies, also produces external magnetic fields with lower ECA frequencies. PMID:12848351

  14. Pulsar Pair Cascades in a Distorted Magnetic Dipole Field

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Muslimov, Alex G.

    2010-01-01

    We investigate the effect of a distorted neutron star dipole magnetic field on pulsar pair cascade multiplicity and pair death lines. Using a simple model for a distorted dipole field that produces an offset polar cap (PC), we derive the accelerating electric field above the PC in space-charge-limited flow. We find that even a modest azimuthally asymmetric distortion can significantly increase the accelerating electric field on one side of the PC and, combined with a smaller field line radius of curvature, leads to larger pair multiplicity. The death line for producing pairs by curvature radiation moves downward in the P-P-dot diagram, allowing high pair multiplicities in a larger percentage of the radio pulsar population. These results could have important implications for the radio pulsar population, high energy pulsed emission, and the pulsar contribution to cosmic ray positrons.

  15. Beam induced electron cloud resonances in dipole magnetic fields

    NASA Astrophysics Data System (ADS)

    Calvey, J. R.; Hartung, W.; Makita, J.; Venturini, M.

    2016-07-01

    The buildup of low energy electrons in an accelerator, known as electron cloud, can be severely detrimental to machine performance. Under certain beam conditions, the beam can become resonant with the cloud dynamics, accelerating the buildup of electrons. This paper will examine two such effects: multipacting resonances, in which the cloud development time is resonant with the bunch spacing, and cyclotron resonances, in which the cyclotron period of electrons in a magnetic field is a multiple of bunch spacing. Both resonances have been studied directly in dipole fields using retarding field analyzers installed in the Cornell Electron Storage Ring. These measurements are supported by both analytical models and computer simulations.

  16. Oscillations of a dipole in a magnetic field: An experiment

    NASA Astrophysics Data System (ADS)

    Bisquert, Juan; Hurtado, Emilia; Mafé, Salvador; Pina, José

    1990-09-01

    The small oscillations of a parallelepidal magnet along the axis of a circular coil carrying an electric current have been analyzed theoretically and experimentally. The study of this system (a particular case of a magnetic dipole in motion in a nonuniform magnetic field) involves basic ideas from both mechanics and electromagnetism, and the equipment used in the experiment is very common in an undergraduate laboratory. Comparison with the experiment shows that a very simple theoretical approach gives good results. It is also shown how the introduction of some refinements in the physical model can improve the agreement between theory and experiment, though the theoretical analysis becomes more involved in this case. The use of the principle of superposition to calculate magnetic fields is emphasized throughout the article.

  17. Graded High Field Nb3Sn Dipole Magnets

    SciTech Connect

    Caspi, S.; Ferracin, P.; Gourlay, S.

    2007-06-01

    Dipole magnets with fields beyond 16T will require superconducting coils that are at least 40 mm thick, an applied pres-stress around 150 MPa and a protection scheme for stored energy in the range of 1-2 MJ/m. The coil size will have a direct impact on the overall magnet cost and the stored energy will raise new questions on protection. To reduce coil size and minimize risk, the coil may have to be graded. Grading is achieved by splitting the coil into several layers with current densities that match the short sample field in each layer. Grading, especially at high fields, can be effective; however it will also significantly raise the stress. In this paper we report on the results of a study on the coil size and field relation to that of the stress and stored energy. We then extend the results to graded coils and attempt to address high stress issues and ways to reduce it.

  18. Neptune radio emission in dipole and multipole magnetic fields

    NASA Technical Reports Server (NTRS)

    Sawyer, C. B.; King, N. V.; Romig, J. H.; Warwick, J. W.

    1995-01-01

    We study Neptune's smooth radio emission in two ways: we simulate the observations and we then consider the radio effects of Neptune's magnetic multipoles. A procedure to deduce the characteristics of radio sources observed by the Planetary Radio Astronomy experiment minimizes limiting assumptions and maximizes use of the data, including quantitative measurement of circular polarization. Study of specific sources simulates time variation of intensity and apparent polarization of their integrated emission over an extended time period. The method is applied to Neptune smooth recurrent emission (SRE). Time series are modeled with both broad and beamed emission patterns, and at two frequencies which exhibit different time variation of polarization. These dipole-based results are overturned by consideration of more complex models of Neptune's magnetic field. Any smooth emission from the anticipated auroral radio source is weak and briefly observed. Dominant SRE originates complex fields at midlatitude. Possible SRE source locations overlap that of 'high-latitude' emission (HLE) between +(out) and -(in) quadrupoles. This is the first identification of multipolar magnetic structure with a major source of planetary radio emission.

  19. Fabrication and test results of a high field, Nb3Sn superconducting racetrack dipole magnet

    SciTech Connect

    Benjegerdes, R.; Bish, P.; Byford, D.; Caspi, S.; Dietderich, D.R.; Gourlay, S.A.; Hafalia, R.; Hannaford, R.; Higley, H.; Jackson, A.; Lietzke, A.; Liggins, N.; McInturff, A.D.; O'Neill, J.; Palmerston, E.; Sabbi, G.; Scanlan, R.M.; Swanson, J.

    2001-06-15

    The LBNL Superconducting Magnet Program is extending accelerator magnet technology to the highest possible fields. A 1 meter long, racetrack dipole magnet, utilizing state-of-the-art Nb{sub 3}Sn superconductor, has been built and tested. A record dipole filed of 14.7 Tesla has been achieved. Relevant features of the final assembly and tested results are discussed.

  20. Nonadiabatic behavior of the magnetic moment of a charged particle in a dipole magnetic field

    NASA Technical Reports Server (NTRS)

    Murakami, Sadayoshi; Sato, Tetsuya; Hasegawa, Akira

    1990-01-01

    This paper investigates the dynamic behavior of the magnetic moment of a particle confined in a magnetic dipole field in the presence of a low-frequency electrostatic wave. It is shown that there exist two kinds of resonances (the bounce-E x B drift resonance and the wave-drift resonance) by which the adiabaticity of the magnetic moment is broken. The unstable conditions obtained by theoretical considerations showed good agreement with the numerical results.

  1. Magnetic field measurements of 1.5 meter model SSC collider dipole magnets at Fermilab

    SciTech Connect

    Lamm, M.J.; Bleadon, M.; Coulter, K.J.; Delchamps, S.; Hanft, R.; Jaffery, T.S.; Kinney, W.; Koska, W.; Ozelis, J.P.; Strait, J.; Wake, M.; DiMarco, J.

    1991-09-01

    Magnetic field measurements have been performed at Fermilab on 1.5 m magnetic length model dipoles for the Superconducting Supercollider. Harmonic measurements are recorded at room temperature before and after the collared coil is assembled into the yoke and at liquid helium temperature. Measurements are made as a function of longitudinal position and excitation current. High field data are compared with room temperature measurements of both the collared coil and the completed yoked magnet and with the predicted fields for both the body of the magnet and the coil ends.

  2. MAGNETIC FIELD MEASUREMENTS OF HD2, A HIgh Nb3Sn DIPOLE MAGNET

    SciTech Connect

    Wang, X.; Caspi, S.; Cheng, D. W.; Felice, H.; Ferracin, P.; Hafalia, R. R.; Joseph, J. M.; Lietzke, A. F.; Lizarazo, J.; McInturff, A. D.; Sabbi, G. L.; Sasaki, K.

    2009-05-04

    The Superconducting Magnet Program at Lawrence Berkeley National Laboratory has designed and tested HD2, a 1 m long Nb{sub 3}Sn accelerator-type dipole based on a simple block-type coil geometry with flared ends. HD2 represents a step toward the development of cost-effective accelerator quality magnets operating in the range of 13-15 T. The design was optimized to minimize geometric harmonics and to address iron saturation and conductor magnetization effects. Field quality was measured during recent cold tests. The measured harmonics are presented and compared to the design values.

  3. Interaction of counter-streaming plasma flows in a dipole magnetic field

    NASA Astrophysics Data System (ADS)

    Shaikhislamov, I. F.; Posukh, V. G.; Melekhov, A. V.; Prokopov, P. A.; Boyarintsev, E. L.; Zakharov, Yu P.; Ponomarenko, A. G.

    2016-11-01

    The transient interaction of counter-streaming super-sonic plasma flows in a dipole magnetic dipole is studied in a laboratory experiment. First quasi-stationary flow is produced by θ -pinch and forms a magnetosphere around the magnetic dipole, while laser beams focused at the surface of the dipole cover launch a second explosive plasma expanding outward from the inner dipole region. The laser plasma is energetic enough to disrupt the magnetic field and to sweep through the background plasma for large distances. Probe measurements showed that far from the initially formed magnetosphere laser plasma carries within itself a magnetic field of the same direction but an order of magnitude larger than the vacuum dipole field at considered distances. Because no compression of the magnetic field at the front of the laser plasma was observed, the realised interaction is different from previous experiments and theoretical models of laser plasma expansion into a uniform magnetized background. It was deduced based on the obtained data that, while expanding through the inner magnetosphere, laser plasma picks up a magnetised shell formed by background plasma and carries it for large distances beyond the previously existing magnetosphere.

  4. Is the Non-Dipole Magnetic Field Random?

    NASA Technical Reports Server (NTRS)

    Walker, Andrew D.; Backus, George E.

    1996-01-01

    Statistical modelling of the Earth's magnetic field B has a long history. In particular, the spherical harmonic coefficients of scalar fields derived from B can be treated as Gaussian random variables. In this paper, we give examples of highly organized fields whose spherical harmonic coefficients pass tests for independent Gaussian random variables. The fact that coefficients at some depth may be usefully summarized as independent samples from a normal distribution need not imply that there really is some physical, random process at that depth. In fact, the field can be extremely structured and still be regarded for some purposes as random. In this paper, we examined the radial magnetic field B(sub r) produced by the core, but the results apply to any scalar field on the core-mantle boundary (CMB) which determines B outside the CMB.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Wang, J. G.

    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 pseudoharmonic 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 quasianalytical 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.

  7. Dipole magnetic field of neutron stars in f(R) gravity

    NASA Astrophysics Data System (ADS)

    Bakirova, Elizat; Folomeev, Vladimir

    2016-10-01

    The structure of an interior dipole magnetic field of neutron stars in f( R) gravity is considered. For this purpose, the perturbative approaches are used when both the deviations from general relativity and the deformations of spherically symmetric configurations associated with the presence of the magnetic field are assumed to be small. Solutions are constructed which describe relativistic, spherically symmetric configurations consisting of a gravitating magnetized perfect fluid modeled by a realistic equation of state. Comparing configurations from general relativity and modified gravity, we reveal possible differences in the structure of the magnetic field which occur in considering neutron stars in modified gravity.

  8. Magnetic design and field optimization of a superferric dipole for the RISP fragment separator

    NASA Astrophysics Data System (ADS)

    Zaghloul, A.; Kim, J. Y.; Kim, D. G.; Jo, H. C.; Kim, M. J.

    2015-10-01

    The in-flight fragment separator of the Rare Isotope Science Project requires eight dipole magnets to produce a gap field of 1.7 T in a deflection sector of 30 degree with a 6-m central radius. If the beam-optics requirements are to be met, an integral field homogeneity of a few units (1 unit = 10-4) must be achieved. A superferric dipole magnet has been designed by using the Low-Temperature Superconducting wire NbTi and soft iron of grade SAE1010. The 3D magnetic design and field optimization have been performed using the Opera code. The length and the width of the air slots in the poles have been determined in an optimization process that considered not only the uniformity of the field in the straight section but also the field errors in the end regions. The field uniformity has also been studied for a range of operation of the dipole magnet from 0.4 T to 1.7 T. The magnetic design and field uniformity are discussed.

  9. The high field superferric magnet Design and test of a new dipole magnet for future hadron colliders

    NASA Astrophysics Data System (ADS)

    Colvin, John C.; Hinterberger, Henry; Russell Huson, F.; Mackay, William W.; Mann, Thomas L.; McIntyre, Peter M.; Phillips, Gerald C.; Pissanetzky, Sergio; Rocha, Richard; Schmidt, William M.; Shotzman, Garry; Wenzel, William A.; Fen Xie, Wan; Zeigler, John C.

    1988-07-01

    The Texas Accelerator Center has successfully tested a 6 T superferric dipole magnet of a design appropriate for future hadron colliders. The magnet surpassed the design field (90% of the short sample limit) on its first quench without training. The measured field quality is in excellent agreement with design calculations and meets collider requirements. The magnetic field design was developed at Rice University and is the subject of a Master's thesis. The features of the design include simple construction, efficient use of superconductor, and adequate containment of magnetic forces. A straightforward extension of the design to an 8 T dipole is under development. The high-field superferric magnet constitutes a significant improvement in magnet performance and cost for future accelerators.

  10. Magnetic field measurements of full length 50 mm aperture SSC dipole magnets at Fermilab

    SciTech Connect

    Strait, J.; Bossert, R.; Carson, J.; Delchamps, S.W.; Gourlay, S.; Hanft, R.; Koska, W.; Kuchnir, M.; Lamm, M.J.; Mazur, P.O.; Mokhtarani, A.; Orris, D.; Ozelis, J.; Wake, M. ); Devred, A.; DiMarco, J.; Kuzminski, J.; Puglisi, M.; Tompkins, J.C.; Yu, Y.; Zhao, Y.; Zheng, H. ); Ogitsu, T. (Supe

    1992-09-01

    Thirteen 16 m long, 50 mm aperture SSC dipole magnets, designed jointly by Fermilab, Brookhaven National Laboratory, Lawrence Berkeley Laboratory and the SSC Laboratory, have been built at Fermilab. The first nine magnets have been fully tested to date. The allowed harmonics are systematically shifted from zero by amounts larger than the specification. The unallowed harmonics, with the exception of the skew sextupole, are consistent with zero. The magnet-to-magnet RMS variation of all harmonics is much smaller than the specification.

  11. Mechanism of formation of a dipole magnetic field in the central regions of active galaxies

    NASA Astrophysics Data System (ADS)

    Andreasyan, R. R.

    1996-01-01

    A model of the formation of large-scale magnetic fields of dipole configuration in the central regions (r ≈ 100 pc) of active galaxies is studied. It is assumed that these regions contain a rapidly rotating, highly ionized gas (Ω ≈ 5·10-15 sec, Ne ≈ 103 cm-3). Ionized matter escapes from the center of the region with a velocity of several hundred km/sec and is entrained by the rotation of the surrounding medium. Biermann's "battery" effect [L. Biermann, Z. Naturforsch., 5a, 65 (1950)] operates under such conditions, and circular electric currents are formed in the medium, which amplify the dipole magnetic fields. During the active phase of a galaxy, about 108 years, the magnetic field strength at the boundary of this region may reach 10-4 10-3 G.

  12. Efficient injection of an intense positron beam into a dipole magnetic field

    NASA Astrophysics Data System (ADS)

    Saitoh, H.; Stanja, J.; Stenson, E. V.; Hergenhahn, U.; Niemann, H.; Pedersen, T. Sunn; Stoneking, M. R.; Piochacz, C.; Hugenschmidt, C.

    2015-10-01

    We have demonstrated efficient injection and trapping of a cold positron beam in a dipole magnetic field configuration. The intense 5 eV positron beam was provided by the NEutron induced POsitron source MUniCh facility at the Heinz Maier-Leibnitz Zentrum, and transported into the confinement region of the dipole field trap generated by a supported, permanent magnet with 0.6 T strength at the pole faces. We achieved transport into the region of field lines that do not intersect the outer wall using the {E}× {B} drift of the positron beam between a pair of tailored plates that created the electric field. We present evidence that up to 38% of the beam particles are able to reach the intended confinement region and make at least a 180° rotation around the magnet where they annihilate on an insertable target. When the target is removed and the {E}× {B} plate voltages are switched off, confinement of a small population persists for on the order of 1 ms. These results lend optimism to our larger aims to apply a magnetic dipole field configuration for trapping of both positrons and electrons in order to test predictions of the unique properties of a pair plasma.

  13. Studies of time dependence of fields in TEVATRON superconducting dipole magnets

    SciTech Connect

    Hanft, R.W.; Brown, B.C.; Herrup, D.A.; Lamm, M.J.; McInturff, A.D.; Syphers, M.J.

    1988-08-22

    The time variation in the magnetic field of a model Tevatron dipole magnet at constant excitation current has been studied. Variations in symmetry allowed harmonic components over long time ranges show a log t behavior indicative of ''flux creep.'' Both short time range and long time range behavior depend in a detailed way on the excitation history. Similar effects are seen in the remnant fields present in full-scale Tevatron dipoles following current ramping. Both magnitudes and time dependences are observed to depend on details for the ramps, such as ramp rate, flattop duration, and number of ramps. In a few magnets, variations are also seen in symmetry unallowed harmonics. 9 refs., 10 figs.

  14. 3D Design, Contruction, and Field Analysis of CIS Main Dipole Magnets

    NASA Astrophysics Data System (ADS)

    Berg, G. P. A.; Fox, W.; Friesel, D. L.; Rinckel, T.

    1997-05-01

    The lattice for CIS ( Cooler Injection Synchroton ) requires four laminated 90^circ main dipole magnets with bending radius ρ = 1.273 m, EFL = 2 m, and an edge angle of 12^circ. Optimum Cooler injection and injection in the planned 15 GeV LISS ring requires operation up to about 1.75 T. Initial operation of 1 Hz, with later upgrade to 5 Hz is planned. We will present 2D and 3D field calculations used to optimize the shape of laminations and endpacks of the magnet. Endpacks are designed to determine edge angle and to compensate hexapole components, in particular above 1.4 T where saturation becomes significant. The large dipole curvature required a new type of dipole construction. Each magnet consists of wedge shaped blocks fabricated from stamped lamination of cold rolled low carbon iron. B-stage (dry) epopy was used for bonding and insulation. The end blocks are machined to include the calculated 3D shape of the endpacks. All four magnets were mapped in the field range from 0.3 T - 1.8 T. Comparison of calculations and data in terms of B(I) curves, EFL, edge angle, and hexapole component as function of field excitation will be presented. The constructed magnets are well within expected specifications.

  15. Axial variations in the magnetic field of superconducting dipoles and quadrupoles

    SciTech Connect

    Ghosh, A.K.; Robins, K.E.; Sampson, W.B.

    1993-09-01

    A periodic variation in the magnetic field along the axis has been observed in both quadrupole and dipole magnets made from superconducting cable. This oscillation is present in all components of the field and has a wavelength equal to the transposition length of the cable. In general the amplitude of these variations increases with magnet current and is not reversible. The residual field patten at zero current depends on the energizing cycle and increases with time spent at high field. The decay of the oscillations has a complex time dependence which contains some extremely long time constants. Unbalanced currents in the individual strands of the cable appear to cause these effects and the field variations can only be completely erased by raising the magnet above its critical temperature.

  16. Thermal equilibrium of non-neutral plasma in dipole magnetic field

    SciTech Connect

    Sato, N.; Kasaoka, N.; Yoshida, Z.

    2015-04-15

    Self-organization of a long-lived structure is one of the remarkable characteristics of macroscopic systems governed by long-range interactions. In a homogeneous magnetic field, a non-neutral plasma creates a “thermal equilibrium,” which is a Boltzmann distribution on a rigidly rotating frame. Here, we study how a non-neutral plasma self-organizes in inhomogeneous magnetic field; as a typical system, we consider a dipole magnetic field. In this generalized setting, the plasma exhibits its fundamental mechanism that determines the relaxed state. The scale hierarchy of adiabatic invariants is the determinant; the Boltzmann distribution under the topological constraint by the robust adiabatic invariants (hence, the homogeneous distribution with respect to the fragile invariant) is the relevant relaxed state, which turns out to be a rigidly rotating clump of particles (just same as in a homogeneous magnetic field), while the density is no longer homogeneous.

  17. Measuring the Forces Between Magnetic Dipoles

    NASA Astrophysics Data System (ADS)

    Gayetsky, Lisa E.; Caylor, Craig L.

    2007-09-01

    We describe a simple undergraduate lab in which students determine how the force between two magnetic dipoles depends on their separation. We consider the case where both dipoles are permanent and the case where one of the dipoles is induced by the field of the other (permanent) dipole. Agreement with theoretically expected results is quite good.

  18. Measuring the Forces between Magnetic Dipoles

    ERIC Educational Resources Information Center

    Gayetsky, Lisa E.; Caylor, Craig L.

    2007-01-01

    We describe a simple undergraduate lab in which students determine how the force between two magnetic dipoles depends on their separation. We consider the case where both dipoles are permanent and the case where one of the dipoles is induced by the field of the other (permanent) dipole. Agreement with theoretically expected results is quite good.

  19. Surface temperature of a magnetized neutron star and interpretation of the ROSAT data. 1: Dipole fields

    NASA Technical Reports Server (NTRS)

    Page, Dany

    1995-01-01

    We model the temperature distribution at the surface of a magnetized neutron star and study the effects on the observed X-ray spectra and light curves. Generalrelativistic effects, i.e., redshift and lensing, are fully taken into account. Atmospheric effects on the emitted spectral flux are not included: we consider only blackbody emission at the local effective temperature. In this first paper we restrict ourselves to dipole fields. General features are studied and compared with the ROSAT data from the pulsars 0833 - 45 (Vela), 0656 + 14, 0630 + 178 (Geminga), and 1055 - 52, the four cases for which there is strong evidence that thermal radiation from the stellar surface is detected. The composite spectra we obtain are not very different from a blackbody spectrum at the star's effective temperature. We conclude that, as far as blackbody spectra are considered, temperature estimates using single-temperature models give results practically identical to our composite models. The change of the (composite blackbody) spectrum with the star's rotational phase is also not very large and may be unobservable inmost cases. Gravitational lensing strongly suppresses the light curve pulsations. If a dipole field is assumed, pulsed fractions comparable to the observed ones can be obtained only with stellar radii larger than those which are predicted by current models of neutron star struture, or with low stellar masses. Moreover, the shapes of the theoretical light curves with dipole fields do not correspond to the observations. The use of magnetic spectra may raise the pulsed fraction sufficiently but will certainly make the discrepancy with the light curve shapes worse: dipole fields are not sufficient to interpret the data. Many neutron star models with a meson condensate or hypersons predict very small radii, and hence very strong lensing, which will require highly nondipolar fields to be able to reproduce the observed pulsed fractions, if possible at all: this may be a new

  20. Magnetic Field Mapping and Integral Transfer Function Matching of the Prototype Dipoles for the NSLS-II at BNL

    SciTech Connect

    He, P.; Jain, A., Gupta, R., Skaritka, J., Spataro, C., Joshi, P., Ganetis, G., Anerella, M., Wanderer, P.

    2011-03-28

    The National Synchrotron Light Source-II (NSLS-II) storage ring at Brookhaven National Laboratory (BNL) will be equipped with 54 dipole magnets having a gap of 35 mm, and 6 dipoles having a gap of 90 mm. Each dipole has a field of 0.4 T and provides 6 degrees of bending for a 3 GeV electron beam. The large aperture magnets are necessary to allow the extraction of long-wavelength light from the dipole magnet to serve a growing number of users of low energy radiation. The dipoles must not only have good field homogeneity (0.015% over a 40 mm x 20 mm region), but the integral transfer functions and integral end harmonics of the two types of magnets must also be matched. The 35 mm aperture dipole has a novel design where the yoke ends are extended up to the outside dimension of the coil using magnetic steel nose pieces. This design increases the effective length of the dipole without increasing the physical length. These nose pieces can be tailored to adjust the integral transfer function as well as the homogeneity of the integrated field. One prototype of each dipole type has been fabricated to validate the designs and to study matching of the two dipoles. A Hall probe mapping system has been built with three Group 3 Hall probes mounted on a 2-D translation stage. The probes are arranged with one probe in the midplane of the magnet and the others vertically offset by {+-}10 mm. The field is mapped around a nominal 25 m radius beam trajectory. The results of measurements in the as-received magnets, and with modifications made to the nose pieces are presented.

  1. Diffusion-mediated dephasing in the dipole field around a single spherical magnetic object.

    PubMed

    Buschle, Lukas R; Kurz, Felix T; Kampf, Thomas; Triphan, Simon M F; Schlemmer, Heinz-Peter; Ziener, Christian Herbert

    2015-11-01

    In this work, the time evolution of the free induction decay caused by the local dipole field of a spherical magnetic perturber is analyzed. The complicated treatment of the diffusion process is replaced by the strong-collision-approximation that allows a determination of the free induction decay in dependence of the underlying microscopic tissue parameters such as diffusion coefficient, sphere radius and susceptibility difference. The interplay between susceptibility- and diffusion-mediated effects yields several dephasing regimes of which, so far, only the classical regimes of motional narrowing and static dephasing for dominant and negligible diffusion, respectively, were extensively examined. Due to the asymmetric form of the dipole field for spherical objects, the free induction decay exhibits a complex component in contradiction to the cylindrical case, where the symmetric local dipole field only causes a purely real induction decay. Knowledge of the shape of the corresponding frequency distribution is necessary for the evaluation of more sophisticated pulse sequences and a detailed understanding of the off-resonance distribution allows improved quantification of transverse relaxation.

  2. Birotor dipole model for Saturn's inner magnetic field from CASSINI RPWS measurements and MAG data

    NASA Astrophysics Data System (ADS)

    Galopeau, Patrick H. M.

    2016-10-01

    The radio and plasma wave science (RPWS) experiment on board the Cassini spacecraft, orbiting around Saturn since July 2004, revealed the presence of two distinct and variable rotation periods in the Saturnian kilometric radiation (SKR). These two periods were attributed to the northern and southern hemispheres respectively. The existence of a double period makes the study of the planetary magnetic field much more complicated and the building of a field model, based on the direct measurements of the MAG experiment from the magnetometers embarked on board Cassini, turns out to be uncertain. The first reason is the difficulty for defining a longitude system linked to the variable period, because the internal magnetic field measurements from MAG are not continuous. The second reason is the existence itself of two distinct periods which could imply the existence of a double rotation magnetic structure generated by Saturn's dynamo. However, the radio observations from the RPWS experiment allow a continuous and accurate follow-up of the rotation phase of the variable two periods, since the SKR emission is permanently observable and produced very close to the planetary surface. A wavelet transform analysis of the intensity of the SKR signal received at 290 kHz was performed in order to calculate the rotation phase of each Saturnian hemisphere. A dipole model was proposed for Saturn's inner magnetic field: this dipole presents the particularity to rotate around Saturn's axis at two different angular velocities; it is tilted and not centered. Then it is possible to fit the MAG data for each Cassini's revolution around the planet the periapsis of which is less than 5 Saturnian radii. This study suggests that Saturn's inner magnetic field is neither stationary nor fully axisymmetric. Such a result can be used as a boundary condition for modelling and constraining the planetary dynamo.

  3. Stress management as an enabling technology for high-field superconducting dipole magnets

    NASA Astrophysics Data System (ADS)

    Holik, Eddie Frank, III

    This dissertation examines stress management and other construction techniques as means to meet future accelerator requirement demands by planning, fabricating, and analyzing a high-field, Nb3Sn dipole. In order to enable future fundamental research and discovery in high energy accelerator physics, bending magnets must access the highest fields possible. Stress management is a novel, propitious path to attain higher fields and preserve the maximum current capacity of advanced superconductors by managing the Lorentz stress so that strain induced current degradation is mitigated. Stress management is accomplished through several innovative design features. A block-coil geometry enables an Inconel pier and beam matrix to be incorporated in the windings for Lorentz Stress support and reduced AC loss. A laminar spring between windings and mica paper surrounding each winding inhibit any stress transferral through the support structure and has been simulated with ALGORRTM. Wood's metal filled, stainless steel bladders apply isostatic, surface-conforming preload to the pier and beam support structure. Sufficient preload along with mica paper sheer release reduces magnet training by inhibiting stick-slip motion. The effectiveness of stress management is tested with high-precision capacitive stress transducers and strain gauges. In addition to stress management, there are several technologies developed to assist in the successful construction of a high-field dipole. Quench protection has been designed and simulated along with full 3D magnetic simulation with OPERARTM. Rutherford cable was constructed, and cable thermal expansion data was analysed after heat treatment. Pre-impregnation analysis techniques were developed due to elemental tin leakage in varying quantities during heat treatment from each coil. Robust splicing techniques were developed with measured resistivites consistent with nO joints. Stress management has not been incorporated by any other high field dipole

  4. Proposal for a cryogenic magnetic field measurement system for SSC dipole magnets

    SciTech Connect

    Green, M.I.; Hansen, L.

    1991-03-01

    This proposal describes the research and development required, and the subsequent fabrication of, a system capable of making integrated magnetic multipole measurements of cryogenic 40-mm-bore SSC dipole magnets utilizing a cryogenic probe. Our experience and some preliminary studies indicate that it is highly unlikely that a 16-meter-long probe can be fabricated that will have a twist below several milliradians at cryogenic temperatures. We would anticipate a twist of several milliradians just as a result of cooldown stresses. Consequently, this proposal describes a segmented 16-meter-long probe, for which we intend to calibrate the phase of each segment to within 0.1 milliradians. The data for all segments will be acquired simultaneously, and integrated data will be generated from the vector sums of the individual segments. The calibration techniques and instrumentation required to implement this system will be described. The duration of an integral measurement at one current is expected to be under 10 seconds. The system is based on an extrapolation of the techniques used at LBL to measure cryogenic 1-meter models of SSC magnets with a cryogenic probe. It should be noted that the expansion of the dipole bore from 40 to 50 mm may make a warm-finger device practical at a cost of approximately one quarter of the cryogenic probe. A warm quadrupole measurement system can be based upon the same principles. 5 refs., 9 figs., 1 tab.

  5. Generalized magnetotail equilibria: Effects of the dipole field, thin current sheets, and magnetic flux accumulation

    NASA Astrophysics Data System (ADS)

    Sitnov, M. I.; Merkin, V. G.

    2016-08-01

    Generalizations of the class of quasi-1-D solutions of the 2-D Grad-Shafranov equation, first considered by Schindler in 1972, are investigated. It is shown that the effect of the dipole field, treated as a perturbation, can be included into the original 1972 class solution by modification of the boundary conditions. Some of the solutions imply the formation of singularly thin current sheets. Equilibrium solutions for such sheets resolving their singular current structure on the scales comparable to the thermal ion gyroradius can be obtained assuming anisotropic and nongyrotropic plasma distributions. It is shown that one class of such equilibria with the dipole-like boundary perturbation describes bifurcation of the near-Earth current sheet. Another class of weakly anisotropic equilibria with thin current sheets embedded into a thicker plasma sheet helps explain the formation of thin current sheets in a relatively distant tail, where such sheets can provide ion Landau dissipation for spontaneous magnetic reconnection. The free energy for spontaneous reconnection can be provided due to accumulation of the magnetic flux at the tailward end of the closed field line region. The corresponding hump in the normal magnetic field profile Bz(x,z = 0) creates a nonzero gradient along the tail. The resulting gradient of the equatorial magnetic field pressure is shown to be balanced by the pressure gradient and the magnetic tension force due to the higher-order correction of the latter in the asymptotic expansion of the tail equilibrium in the ratio of the characteristic tail current sheet variations across and along the tail.

  6. New method to determine proton trajectories in the equatorial plane of a dipole magnetic field.

    PubMed

    Ioanoviciu, Damaschin

    2015-01-01

    A parametric description of proton trajectories in the equatorial plane of Earth's dipole magnetic field has been derived. The exact expression of the angular coordinate contains an integral to be performed numerically. The radial coordinate results from the initial conditions by basic mathematical operations and by using trigonometric functions. With the approximate angular coordinate formula, applicable for a wide variety of cases of protons trapped in Earth's radiation belts, no numerical integration is needed. The results of exact and approximate expressions were compared for a specific case and small differences were found.

  7. Small oscillations of a 3D electric dipole in the presence of a uniform magnetic field

    NASA Astrophysics Data System (ADS)

    del Pino, L. A.; Atenas, B.; Curilef, S.

    2016-05-01

    The classical behavior of a 3D electric dipole in the presence of a uniform magnetic field is studied in the small oscillations approximation. Using the Lagrangian formulation, the equations of motion are obtained, as well as their solutions and constants of motion. Normal modes of oscillation and their corresponding normal coordinates are obtained. Furthermore, the existence of a type of bound states without turning points, so-called trapped states conjectured by Troncoso and Curilef [Eur. J. Phys 27 (2006) 1315-1322], is investigated.

  8. How to introduce the magnetic dipole moment

    NASA Astrophysics Data System (ADS)

    Bezerra, M.; Kort-Kamp, W. J. M.; Cougo-Pinto, M. V.; Farina, C.

    2012-09-01

    We show how the concept of the magnetic dipole moment can be introduced in the same way as the concept of the electric dipole moment in introductory courses on electromagnetism. Considering a localized steady current distribution, we make a Taylor expansion directly in the Biot-Savart law to obtain, explicitly, the dominant contribution of the magnetic field at distant points, identifying the magnetic dipole moment of the distribution. We also present a simple but general demonstration of the torque exerted by a uniform magnetic field on a current loop of general form, not necessarily planar. For pedagogical reasons we start by reviewing briefly the concept of the electric dipole moment.

  9. Recent Test Results of the High Field Nb3Sn Dipole Magnet HD2

    SciTech Connect

    Ferracin, P.; Bingham, B.; Caspi, S.; Cheng, D. W.; Dietderich, D. R.; Felice, H.; Hafalia, A. R.; Hannaford, C. R.; Joseph, J.; Lietzke, A. F.; Lizarazo, J.; Sabbi, G.; Wang, X.

    2009-10-19

    The 1 m long Nb{sub 3}Sn dipole magnet HD2, fabricated and tested at Lawrence Berkeley National Laboratory, represents a step towards the development of block-type accelerator quality magnets operating in the range of 13-15 T. The magnet design features two coil modules composed of two layers wound around a titanium-alloy pole. The layer 1 pole includes a round cutout to provide room for a bore tube with a clear aperture of 36 mm. After a first series of tests where HD2 reached a maximum bore field of 13.8 T, corresponding to an estimated peak field on the conductor of 14.5 T, the magnet was disassembled and reloaded without the bore tube and with a clear aperture increased to 43 mm. We describe in this paper the magnet training observed in two consecutive tests after the removal of the bore tube, with a comparison of the quench performance with respect to the previous tests. An analysis of the voltage signals recorded before and after training quenches is then presented and discussed, and the results of coil visual inspections reported.

  10. Spherical Rare Earth Magnets And The Dipole-Dipole Interaction

    NASA Astrophysics Data System (ADS)

    Adams, Al J.

    2006-12-01

    Spherical rare earth magnets (SREMs) are useful for teaching fundamental concepts in introductory physics. These applications include kinematics, force and motion, energy, momentum, and their conservation, as well as the traditional areas of basic magnetism, the magnetic field of the earth, and magnetic interactions. One application for upper level undergraduate physics majors is the dipole-dipole interaction. Previous studies have confirmed the validity of the dipole approximation for SREMs. Their spherical shape allows them to combine in ways that readily demonstrate local minima in the potential energy interaction function for multiple dipoles. The potential energy function for the dipole-dipole interaction will be given and will be shown to predict several of the basic stable configurations for 2 and 3 SREM spheres. The relative stability of several of these local potential energy minima will be discussed and the results of tests for their reliability in predicting preferred configurations presented. The use of commercial mathematical analysis software for modeling the dipole-dipole interaction will also be demonstrated.

  11. Enabling automated magnetic resonance imaging-based targeting assessment during dipole field navigation

    NASA Astrophysics Data System (ADS)

    Latulippe, Maxime; Felfoul, Ouajdi; Dupont, Pierre E.; Martel, Sylvain

    2016-02-01

    The magnetic navigation of drugs in the vascular network promises to increase the efficacy and reduce the secondary toxicity of cancer treatments by targeting tumors directly. Recently, dipole field navigation (DFN) was proposed as the first method achieving both high field and high navigation gradient strengths for whole-body interventions in deep tissues. This is achieved by introducing large ferromagnetic cores around the patient inside a magnetic resonance imaging (MRI) scanner. However, doing so distorts the static field inside the scanner, which prevents imaging during the intervention. This limitation constrains DFN to open-loop navigation, thus exposing the risk of a harmful toxicity in case of a navigation failure. Here, we are interested in periodically assessing drug targeting efficiency using MRI even in the presence of a core. We demonstrate, using a clinical scanner, that it is in fact possible to acquire, in specific regions around a core, images of sufficient quality to perform this task. We show that the core can be moved inside the scanner to a position minimizing the distortion effect in the region of interest for imaging. Moving the core can be done automatically using the gradient coils of the scanner, which then also enables the core to be repositioned to perform navigation to additional targets. The feasibility and potential of the approach are validated in an in vitro experiment demonstrating navigation and assessment at two targets.

  12. Effect of a magnetic field on massive-star winds - I. Mass-loss and velocity for a dipole field

    NASA Astrophysics Data System (ADS)

    Bard, Christopher; Townsend, Richard H. D.

    2016-11-01

    We generalize the Rigid-Field Hydrodynamic equations to accommodate arbitrary magnetic field topologies, resulting in a new Arbitrary Rigid-Field Hydrodynamic (ARFHD) formalism. We undertake a critical point calculation of the steady-state ARFHD equations with a CAK-type radiative acceleration and determine the effects of a dipole magnetic field on the usual CAK mass-loss rate and velocity structure. Enforcing the proper optically thin limit for the radiative line-acceleration is found to decrease both the mass-loss and wind acceleration, while rotation boosts both properties. We define optically thin correction and rotation parameters to quantify these effects on the global mass-loss rate and develop scaling laws for the surface mass-flux as a function of surface colatitude. These scaling laws are found to agree with previous laws derived from magnetohydrodynamic simulations of magnetospheres. The dipole magnetosphere velocity structure is found to differ from a global beta-velocity law, which contradicts a central assumption of the previously developed XADM model of X-ray emission from magnetospheres.

  13. Measurement of a false electric dipole moment signal from 199Hg atoms exposed to an inhomogeneous magnetic field

    NASA Astrophysics Data System (ADS)

    Afach, S.; Baker, C. A.; Ban, G.; Bison, G.; Bodek, K.; Chowdhuri, Z.; Daum, M.; Fertl, M.; Franke, B.; Geltenbort, P.; Green, K.; van der Grinten, M. G. D.; Grujic, Z.; Harris, P. G.; Heil, W.; Hélaine, V.; Henneck, R.; Horras, M.; Iaydjiev, P.; Ivanov, S. N.; Kasprzak, M.; Kermaïdic, Y.; Kirch, K.; Knowles, P.; Koch, H.-C.; Komposch, S.; Kozela, A.; Krempel, J.; Lauss, B.; Lefort, T.; Lemière, Y.; Mtchedlishvili, A.; Naviliat-Cuncic, O.; Pendlebury, J. M.; Piegsa, F. M.; Pignol, G.; Prashant, P. N.; Quéméner, G.; Rebreyend, D.; Ries, D.; Roccia, S.; Schmidt-Wellenburg, P.; Severijns, N.; Weis, A.; Wursten, E.; Wyszynski, G.; Zejma, J.; Zenner, J.; Zsigmond, G.

    2015-10-01

    We report on the measurement of a Larmor frequency shift proportional to the electric-field strength for 199Hg atoms contained in a volume permeated with aligned magnetic and electric fields. This shift arises from the interplay between the inevitable magnetic field gradients and the motional magnetic field. The proportionality to electric-field strength makes it apparently similar to an electric dipole moment (EDM) signal, although unlike an EDM this effect is P- and T-conserving. We have used a neutron magnetic resonance EDM spectrometer, featuring a mercury co-magnetometer and an array of external cesium magnetometers, to measure the shift as a function of the applied magnetic field gradient. Our results are in good agreement with theoretical expectations.

  14. Construction of a 56 mm aperture high-field twin-aperture superconducting dipole model magnet

    SciTech Connect

    Ahlbaeck, J; Leroy, D.; Oberli, L.; Perini, D.; Salminen, J.; Savelainen, M.; Soini, J.; Spigo, G.

    1996-07-01

    A twin-aperture superconducting dipole model has been designed in collaboration with Finnish and Swedish Scientific Institutions within the framework of the LHC R and D program and has been built at CERN. Principal features of the magnet are 56 mm aperture, separate stainless steel collared coils, yoke closed after assembly at room temperature, and longitudinal prestressing of the coil ends. This paper recalls the main dipole design characteristics and presents some details of its fabrication including geometrical and mechanical measurements of the collared coil assembly.

  15. A CAMAC-resident microprocessor used for field control of a dipole magnet

    NASA Astrophysics Data System (ADS)

    Sharp, F. J.; Greiner, B. F.

    1990-08-01

    An inexpensive, self-contained microprocessor supporting an on-chip BASIC interpreter has been incorporated into a CAMAC auxiliary-crate controller, with an EEPROM and a terminal port. Used with an ASCII computer terminal, the intelligent auxiliary controller is a self-contained program-development system. One application for the intelligent auxiliary controller is closed-loop control of the analyzing dipoles at the negative-ion injector of the TASCC (tandem accelerator superconducting cyclotron) heavy-ion accelerators. A BASIC program stored in the EEPROM runs on power-up of the controller. The program reads control numbers from a CAMAC mailbox, converts the ASCII character string from a precision Hall-probe teslameter to a digital field reading, and writes a control number to the dipole controller. The program iterates until the dipole reaches the demand field, while updating another CAMAC mailbox with a field readback for the main control system.

  16. Magnetic dipole discharges. III. Instabilities

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.; Ionita, C.; Schrittwieser, R.

    2013-08-15

    Instabilities in a cross-field discharge around a permanent magnet have been investigated. The permanent magnet serves as a cold cathode and the chamber wall as an anode. The magnet is biased strongly negative and emits secondary electrons due to impact of energetic ions. The electrons outside the sheath are confined by the strong dipolar magnetic field and by the ion-rich sheath surrounding the magnet. The electron energy peaks in the equatorial plane where most ionization occurs and the ions are trapped in a negative potential well. The discharge mechanism is the same as that of cylindrical and planar magnetrons, but here extended to a 3-D cathode geometry using a single dipole magnet. While the basic properties of the discharge are presented in a companion paper, the present focus is on various observed instabilities. The first is an ion sheath instability which oscillates the plasma potential outside the sheath below the ion plasma frequency. It arises in ion-rich sheaths with low electron supply, which is the case for low secondary emission yields. Sheath oscillations modulate the discharge current creating oscillating magnetic fields. The second instability is current-driven ion sound turbulence due to counter-streaming electrons and ions. The fluctuations have a broad spectrum and short correlation lengths in all directions. The third type of fluctuations is spiky potential and current oscillations in high density discharges. These appear to be due to unstable emission properties of the magnetron cathode.

  17. Investigating the Effect of Line Dipole Magnetic Field on Hydrothermal Characteristics of a Temperature-Sensitive Magnetic Nanofluid Using Two-Phase Simulation

    NASA Astrophysics Data System (ADS)

    Bahiraei, Mehdi; Hangi, Morteza

    2016-10-01

    Hydrothermal characteristics of a temperature-sensitive magnetic nanofluid between two parallel plates are investigated in the presence of magnetic field produced by one or multiple line dipole(s) using the two-phase mixture model. As the nanofluid reaches the region where the magnetic field is applied, a rotation is developed due to the dependency of magnetization on temperature. This can lead to mixing in the flow and more uniform distribution of temperature due to the disturbance caused in the boundary layer, and consequently, enhancement in convective heat transfer. The results indicate that the disturbance in boundary layer adjacent to the lower wall is more significant than the upper wall. By application of the magnetic field, the convective heat transfer increases locally for both walls. Due to the intensified mixing, a sudden pressure drop occurs when the fluid reaches the region where the magnetic field is applied. For greater magnetic field strengths and lower Reynolds numbers, the improvement in convective heat transfer is more significant. For small magnetic field strengths, the effect of applying magnetic field on the upper wall is much smaller than that on the lower wall; however, this effect becomes almost the same for both walls at great magnetic field strengths.

  18. Assembly and Test of HD2, a 36 mm bore high field Nb3Sn Dipole Magnet

    SciTech Connect

    Ferracin, P.; Bingham, B.; Caspi, S.; Cheng, D. W,.; Dietderich, D. R.; Felice, H.; Godeke, A.; Hafalia, A. R.; Hannaford, C. R.; Joseph, J.; Lietzke, A. F.; Lizarazo, J.; Sabbi, G.; Trillaud, F.; Wang, X.

    2008-08-17

    We report on the fabrication, assembly, and test of the Nb{sub 3}Sn dipole magnet HD2. The magnet, aimed at demonstrating the application of Nb{sub 3}Sn superconductor in high field accelerator-type dipoles, features a 36 mm clear bore surrounded by block-type coils with tilted ends. The coil design is optimized to minimize geometric harmonics in the aperture and the magnetic peak field on the conductor in the coil ends. The target bore field of 15 T at 4.3 K is consistent with critical current measurements of extracted strands. The coils are horizontally pre-stressed during assembly using an external aluminum shell pre-tensioned with water-pressurized bladders. Axial pre-loading of the coil ends is accomplished through two end plates and four aluminum tension rods. The strain in coil, shell, and rods is monitored with strain gauges during assembly, cool-down and magnet excitation, and compared with 3D finite element computations. Magnet's training performance, quench locations, and ramp-rate dependence are then analyzed and discussed.

  19. Dynamic stabilization of the magnetic field surrounding the neutron electric dipole moment spectrometer at the Paul Scherrer Institute

    SciTech Connect

    Afach, S.; Fertl, M.; Franke, B. E-mail: bernhard.lauss@psi.ch; Kirch, K.; Bison, G.; Burri, F.; Chowdhuri, Z.; Daum, M.; Henneck, R.; Lauss, B. E-mail: bernhard.lauss@psi.ch; Meier, M.; Schmidt-Wellenburg, P.; Zsigmond, G.; Bodek, K.; Zejma, J.; Grujic, Z.; Kasprzak, M.; Weis, A.; Hélaine, V.; Koch, H.-C.; and others

    2014-08-28

    The Surrounding Field Compensation (SFC) system described in this work is installed around the four-layer Mu-metal magnetic shield of the neutron electric dipole moment spectrometer located at the Paul Scherrer Institute. The SFC system reduces the DC component of the external magnetic field by a factor of about 20. Within a control volume of approximately 2.5 m × 2.5 m × 3 m, disturbances of the magnetic field are attenuated by factors of 5–50 at a bandwidth from 10{sup −3} Hz up to 0.5 Hz, which corresponds to integration times longer than several hundreds of seconds and represent the important timescale for the neutron electric dipole moment measurement. These shielding factors apply to random environmental noise from arbitrary sources. This is achieved via a proportional-integral feedback stabilization system that includes a regularized pseudoinverse matrix of proportionality factors which correlates magnetic field changes at all sensor positions to current changes in the SFC coils.

  20. Bound states for an induced electric dipole in the presence of an azimuthal magnetic field and a disclination

    SciTech Connect

    Bakke, K.

    2010-09-15

    Based on the Wei-Han-Wei setup [H. Wei, R. Han, and X. Wei, Phys. Rev. Lett. 75, 2071 (1995)], where a neutral particle with an induced electric dipole moment interacts with a configuration of crossed electric and magnetic fields, in this paper we study the bound states that arise when we change the Wei-Han-Wei field configuration and consider a field configuration of crossed azimuthal magnetic field and a radial electric field. Moreover, we consider here a spin-half neutral particle and the presence of a linear topological defect called disclination. We obtain the bound states in two distinct cases: in the first case, we consider that the wave function of the neutral particle is well-behaved at the origin and vanishes at the asymptotic limit; in the second case, we consider the neutral particle confined to a parabolic potential like a quantum dot.

  1. The influence of differential rotation on the equatorial component of the sun's magnetic dipole field

    NASA Technical Reports Server (NTRS)

    Sheeley, N. R., Jr.

    1981-01-01

    This paper examines the effect that solar differential rotation would have on a hypothetical large-scale equatorial dipole field. The evolving large-scale field pattern is expressed as a series of non-axisymmetric moments. As time increases, power is transferred to progressively higher order moments. In the 27d rotating coordinate system, each moment undergoes a small retrograde drift which remains nearly uniform until that mode begins to fade. The synodic rotation periods of the first few moments are comparable to the observed 28.5d period of the sun's large-scale field near sunspot maximum. Differential rotation may be the source of this 28.5d period, but the eruption of new flux is necessary to keep the pattern going.

  2. Magnetic dipole interactions in crystals

    NASA Astrophysics Data System (ADS)

    Johnston, David C.

    2016-01-01

    The influence of magnetic dipole interactions (MDIs) on the magnetic properties of local-moment Heisenberg spin systems is investigated. A general formulation is presented for calculating the eigenvalues λ and eigenvectors μ ̂ of the MDI tensor of the magnetic dipoles in a line (one dimension, 1D), within a circle (2D) or a sphere (3D) of radius r surrounding a given moment μ⃗i for given magnetic propagation vectors k for collinear and coplanar noncollinear magnetic structures on both Bravais and non-Bravais spin lattices. Results are calculated for collinear ordering on 1D chains, 2D square and simple-hexagonal (triangular) Bravais lattices, 2D honeycomb and kagomé non-Bravais lattices, and 3D cubic Bravais lattices. The λ and μ ̂ values are compared with previously reported results. Calculations for collinear ordering on 3D simple tetragonal, body-centered tetragonal, and stacked triangular and honeycomb lattices are presented for c /a ratios from 0.5 to 3 in both graphical and tabular form to facilitate comparison of experimentally determined easy axes of ordering on these Bravais lattices with the predictions for MDIs. Comparisons with the easy axes measured for several illustrative collinear antiferromagnets (AFMs) are given. The calculations are extended to the cycloidal noncollinear 120∘ AFM ordering on the triangular lattice where λ is found to be the same as for collinear AFM ordering with the same k. The angular orientation of the ordered moments in the noncollinear coplanar AFM structure of GdB4 with a distorted stacked 3D Shastry-Sutherland spin-lattice geometry is calculated and found to be in disagreement with experimental observations, indicating the presence of another source of anisotropy. Similar calculations for the undistorted 2D and stacked 3D Shastry-Sutherland lattices are reported. The thermodynamics of dipolar magnets are calculated using the Weiss molecular field theory for quantum spins, including the magnetic transition

  3. Magnetic dipole interactions in crystals

    DOE PAGESBeta

    Johnston, David

    2016-01-13

    The influence of magnetic dipole interactions (MDIs) on the magnetic properties of local-moment Heisenberg spin systems is investigated. A general formulation is presented for calculating the eigenvalues λ and eigenvectors μ ˆ of the MDI tensor of the magnetic dipoles in a line (one dimension, 1D), within a circle (2D) or a sphere (3D) of radius r surrounding a given moment μ → i for given magnetic propagation vectors k for collinear and coplanar noncollinear magnetic structures on both Bravais and non-Bravais spin lattices. Results are calculated for collinear ordering on 1D chains, 2D square and simple-hexagonal (triangular) Bravais lattices,more » 2D honeycomb and kagomé non-Bravais lattices, and 3D cubic Bravais lattices. The λ and μ ˆ values are compared with previously reported results. Calculations for collinear ordering on 3D simple tetragonal, body-centered tetragonal, and stacked triangular and honeycomb lattices are presented for c/a ratios from 0.5 to 3 in both graphical and tabular form to facilitate comparison of experimentally determined easy axes of ordering on these Bravais lattices with the predictions for MDIs. Comparisons with the easy axes measured for several illustrative collinear antiferromagnets (AFMs) are given. The calculations are extended to the cycloidal noncollinear 120 ° AFM ordering on the triangular lattice where λ is found to be the same as for collinear AFM ordering with the same k. The angular orientation of the ordered moments in the noncollinear coplanar AFM structure of GdB 4 with a distorted stacked 3D Shastry-Sutherland spin-lattice geometry is calculated and found to be in disagreement with experimental observations, indicating the presence of another source of anisotropy. Similar calculations for the undistorted 2D and stacked 3D Shastry-Sutherland lattices are reported. The thermodynamics of dipolar magnets are calculated using the Weiss molecular field theory for quantum spins, including the magnetic

  4. BMAP dipole magnetic field analysis and orbit tracking/calculations of energy deposition in GaAs WHEBY detectors

    NASA Astrophysics Data System (ADS)

    Humphries, S., Jr.; Baltrusaitis, R. M.; Ekdahl, C.; Young, C.; Warn, C.

    This report contains two separate papers. The first paper discusses BMAP which is a versatile program for field analysis and orbit tracking in dipole magnets. The program was created to aid the design of charged-particle magnetic spectrometers. BMAP is written in Pascal and runs on any IBM-PC computer or compatible. The second paper covers a study on energy deposition in GaAS WHEBY detectors. The study was done for two purposes: (1) to set up a three-dimensional electron-photon transport problem using the ACCEPT computer code; and (2) to calculate energy deposition in GaAs detectors in the WHEBY for a given flux of electrons.

  5. Transient particle acceleration in strongly magnetized neutron stars. II - Effects due to a dipole field geometry

    NASA Technical Reports Server (NTRS)

    Fatuzzo, Marco; Melia, Fulvio

    1991-01-01

    Sheared Alfven waves generated by nonradial crustal disturbances above the polar cap of a strongly magnetized neutron star induce an electric field component parallel to B. An attempt is made to determine the manner in which the strong radial dependence of B affects the propagation of these sheared Alfven waves, and whether this MHD process is still an effective particle accelerator. It is found that although the general field equation is quite complicated, a simple wavelike solution can still be obtained under the conditions of interest for which the Alfven phase velocity decouples from the wave equation. The results may be applicable to gamma-ray burst sources.

  6. Trapped field internal dipole superconducting motor generator

    DOEpatents

    Hull, John R.

    2001-01-01

    A motor generator including a high temperature superconductor rotor and an internally disposed coil assembly. The motor generator superconductor rotor is constructed of a plurality of superconductor elements magnetized to produce a dipole field. The coil assembly can be either a conventional conductor or a high temperature superconductor. The superconductor rotor elements include a magnetization direction and c-axis for the crystals of the elements and which is oriented along the magnetization direction.

  7. Precipitation of low energy electrons at high latitudes: Effects of substorms, interplanetary magnetic field and dipole tilt angle

    NASA Technical Reports Server (NTRS)

    Burch, J. L.

    1972-01-01

    Data from the auroral particles experiment on OGO-4 were used to study effects of substorm activity, interplanetary magnetic field latitutde, and dipole tilt angle on high-latitude precipitation of 700 eV electrons. It was found that: (1) The high-latitude zone of 700 eV electron precipitation in late evening and early morning hours moves equatorward by 5 to 10 deg during substorms. (2) The low-latitude boundary of polar cusp electron precipitation at 9 to 15 hours MLT also moves equatorward by several degrees during substorms and, in the absence of significant substorm activity, after a period of southward interplanetary magnetic field. (3) With times containing substorm activity or a southward interplanetary magnetic field eliminated, the low-latitude boundary of polar cusp electron precipitation is found to move by approximately 4 deg over the total yearly range of tilt angles. At maximum winter and summer conditions the invariant latitude of the boundary is shown to shift by approximately -3 deg and +1 deg respectively from its equinox location.

  8. Magnetisation and field quality of a cosine-theta dipole magnet wound with coated conductors for rotating gantry for hadron cancer therapy

    NASA Astrophysics Data System (ADS)

    Amemiya, Naoyuki; Sogabe, Yusuke; Sakashita, Masaki; Iwata, Yoshiyuki; Noda, Koji; Ogitsu, Toru; Ishii, Yusuke; Kurusu, Tsutomu

    2016-02-01

    Electromagnetic field analyses were carried out to study the influence of coated-conductor magnetisation, i.e. the screening (shielding) current, on the field quality of a dipole magnet in a rotating gantry for hadron cancer therapy. The analyses were made on the cross section of a cosine-theta dipole magnet in a rotating gantry for carbon ions, which generated 2.90 T of magnetic field. The temporal profile (temporal variation) of the magnet current was determined based on the actual excitation schemes of the magnets in the rotating gantry. The experimentally determined superconducting property of a coated conductor was considered, and we calculated the temporal evolutions of the current-density distributions in all the turns of coated conductors in the magnet. From the obtained current-density distributions, we calculated the multipole components of the magnetic field and evaluated the field quality of the magnet. The deviation in the dipole component from its designed value was up to approximately 25 mT, which was approximately 1% of the designed maximum dipole component. Its variation between repeated excitations was approximately 0.03%, and it drifted approximately 0.06% in 10 s. Some compensation schemes might be required to counteract such influence of magnetisation on the dipole component. Meanwhile, the higher multipole components were small, stable, and sufficiently reproducible for a magnet in rotating gantries, i.e. |b 3| ˜ 1.1 × 10-3 and |Δb 3| ˜ 0.2 × 10-3 in 10 s.

  9. Bent Solenoids with Superimposed Dipole Fields

    SciTech Connect

    Meinke, Rainer, B.; Goodzeit, Carl, L.

    2000-03-21

    A conceptual design and manufacturing technique were developed for a superconducting bent solenoid magnet with a superimposed dipole field that would be used as a dispersion device in the cooling channel of a future Muon Collider. The considered bent solenoid is equivalent to a 180° section of a toroid with a major radius of ~610 mm and a coil aperture of ~416 mm. The required field components of this magnet are 4 tesla for the solenoid field and 1 tesla for the superimposed dipole field. A magnet of this size and shape, operating at these field levels, has to sustain large Lorentz forces resulting in a maximum magnetic pressure of about 2,000 psi. A flexible round mini-cable with 37 strands of Cu-NbTi was selected as the superconductor. Detailed magnetic analysis showed that it is possible to obtain the required superimposed dipole field by tilting the winding planes of the solenoid by ~25°. A complete structural analysis of the coil support system and the helium containment vessel under thermal, pressure, and Lorentz force loads was carried out using 3D finite element models of the structures. The main technical issues were studied and solutions were worked out so that a highly reliable magnet of this type can be produced at an affordable cost.

  10. Effects of dipole magnet inhomogeneities on the beam ellipsoid

    SciTech Connect

    Tsoupas, N.; Colman, J.; Levine, M.; McKenzie-Wilson, R.; Ward, T.; Grand, P.

    1986-01-01

    The RAYTRACE computer code has been modified to accept magnetic fields measured in the median plane of a dipole magnet. This modification allows one to study the effects of a non-ideal dipole magnet on the beam ellipsoid (as defined by the TRANSPORT code manual). The effects on the beam ellipsoid are due to: field inhomogeneities in the interior region of the dipole, and discrepancies from design conditions of the magnetic field values in the fringe field region. The results of the RAYTRACE code calculations based on experimentally measured fields will be compared with the results derived using both an ideal (no inhomogeneities) dipole with SCOFF boundaries and an ideal dipole with perfect (according to design) fringe fields.

  11. A Three-Dimensional MHD Simulation of the Solar Wind for a Tilted-Dipole Magnetic Field on the Sun

    NASA Technical Reports Server (NTRS)

    Goldstein, Melvyn L.

    2007-01-01

    Using a three-dimensional MHD model, we simulate the global steady-state structure of the solar corona and solar wind for a dipole magnetic field on the Sun inclined by 30 degrees to the solar rotation axis. This represents the solar conditions typical for a declining phase of solar cycle. The computations can extend from the coronal base out to 100-AU and at large heliospheric distances includes the effects of interstellar neutral hydrogen and their interaction with solar wind protons. The simulations can model the formation of corotating interaction regions and the heliospheric current sheet. The simulations are also capable of describing very strong rarefaction regions that include embedded sub-Alfvenic regions that form on the trailing edge of a fast flows.

  12. Novel Design of Superconducting Helical Dipole Magnet

    NASA Astrophysics Data System (ADS)

    Meinke, R.; Senti, M.; Stelzer, G.

    1997-05-01

    Superconducting helical dipole magnets with a nominal field of 4 Tesla are needed for the spin physics program at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. The magnets are required to operate at a relatively low current of 400 A since many of these magnets have to be independently controlled. The Advanced Magnet Lab, Inc., in Palm Bay, FL has designed and built two prototype magnets using advanced computer controlled coil winding technology. The AML design is extremely cost effective since it avoids magnet specific tooling despite the required complex coil pattern and any precision machined inserts or spacers. It is the first time an accelerator magnet of this technology has reached a field above 4 Tesla. Results from the prototype testing at BNL are presented.

  13. Investigation of the magnetic dipole field at the atomic scale in quasi-one-dimensional paramagnetic conductor Li0.9Mo6O17.

    PubMed

    Wu, Guoqing; Ye, Xiao-shan; Zeng, Xianghua; Wu, Bing; Clark, W G

    2016-01-13

    We report magnetic dipole field investigation at the atomic scale in a single crystal of quasi-one-dimensional (Q1D) paramagnetic conductor Li0.9Mo6O17, using a paramagnetic electron model and (7)Li-NMR spectroscopy measurements with an externally applied magnetic field B 0  =  9 T. We find that the magnetic dipole field component ([Formula: see text]) parallel to B 0 at the Li site from the Mo electrons has no lattice axial symmetry; it is small around the middle between the lattice a and c axes in the ac-plane with the minimum at the field orientation angle [Formula: see text], while the [Formula: see text] maximum is at [Formula: see text] when B 0 is applied perpendicular to b ([Formula: see text]), where [Formula: see text] represents the direction of [Formula: see text]. Further estimation indicates that [Formula: see text] has a maximum value of 0.35 G at B 0  =  9 T. By minimizing the potential magnetic contributions to the NMR spectra satellites with the NMR spectroscopy measurements at the direction where the value of the magnetic dipole field component [Formula: see text] is  ∼0, the behavior of the electron charge statics is exhibited. This work demonstrates that the magnetic dipole field of the Mo electrons is the dominant source of the local magnetic fields at the Li site, and suggests that the unknown metal-'insulator' crossover at low temperatures is not a charge effect. The work also reveals valuable local electric and magnetic field information for further NMR investigation as recently suggested (2012 Phys. Rev. B 85 235128) regarding the unusual properties of the material.

  14. Electric field control of magnetic states in isolated and dipole-coupled FeGa nanomagnets delineated on a PMN-PT substrate.

    PubMed

    Ahmad, Hasnain; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2015-10-01

    We report observation of a 'non-volatile' converse magneto-electric effect in elliptical FeGa nanomagnets delineated on a piezoelectric PMN-PT substrate. The nanomagnets are first magnetized with a magnetic field directed along their nominal major axes. Subsequent application of a strong electric field across the piezoelectric substrate generates strain in the substrate, which is partially transferred to the nanomagnets and rotates the magnetizations of some of them away from their initial orientations. The rotated magnetizations remain in their new orientations after the field is removed, resulting in 'non-volatility'. In isolated nanomagnets, the magnetization rotates by <90° upon application of the electric field, but in a dipole-coupled pair consisting of one 'hard' and one 'soft' nanomagnet, which are both initially magnetized in the same direction by the magnetic field, the soft nanomagnet's magnetization rotates by [Formula: see text] upon application of the electric field because of the dipole influence of the hard nanomagnet. This effect can be utilized for a nanomagnetic NOT logic gate. PMID:26373868

  15. Electric field control of magnetic states in isolated and dipole-coupled FeGa nanomagnets delineated on a PMN-PT substrate

    NASA Astrophysics Data System (ADS)

    Ahmad, Hasnain; Atulasimha, Jayasimha; Bandyopadhyay, Supriyo

    2015-10-01

    We report observation of a ‘non-volatile’ converse magneto-electric effect in elliptical FeGa nanomagnets delineated on a piezoelectric PMN-PT substrate. The nanomagnets are first magnetized with a magnetic field directed along their nominal major axes. Subsequent application of a strong electric field across the piezoelectric substrate generates strain in the substrate, which is partially transferred to the nanomagnets and rotates the magnetizations of some of them away from their initial orientations. The rotated magnetizations remain in their new orientations after the field is removed, resulting in ‘non-volatility’. In isolated nanomagnets, the magnetization rotates by \\lt 90^\\circ upon application of the electric field, but in a dipole-coupled pair consisting of one ‘hard’ and one ‘soft’ nanomagnet, which are both initially magnetized in the same direction by the magnetic field, the soft nanomagnet’s magnetization rotates by \\gt 90^\\circ upon application of the electric field because of the dipole influence of the hard nanomagnet. This effect can be utilized for a nanomagnetic NOT logic gate.

  16. Simulation of Whistler Chorus in a Compressed Dipole Field

    NASA Astrophysics Data System (ADS)

    Wu, S.; Denton, R. E.; Hudson, M.

    2015-12-01

    Earth's dipole magnetic field is constantly compressed by the solar wind and the compression is enhanced during magnetic storm. We simulate whistler chorus in a compressed dipole field using a hybrid code. The hybrid code uses the particle-in-cell technique in generalized orthogonal coordinates. In the hybrid code, a small fraction of electrons are treated as particles with anisotropic temperature that leads to the whistler instability. Other electrons are treated as a cold fluid without mass. The density of the fluid electrons is large such that the plasma frequency exceeds the electron gyro frequency. Ions serve as a fixed background. We model the compressed dipole field by adding a constant magnetic field component to the dipole field. The direction of the compressed component is the same as that of the dipole field at the equator. This model of the compressed dipole field yields a magnetic field with off-equator minima and smaller inhomogeneity than the dipole field near the equator. The distribution of hot anisotropic electrons along the magnetic field is a function of adiabatic invariants that satisfies MHD force balance. In the compressed dipole field, the hot electron anisotropy, hot electron density and plasma beta in the direction parallel to the background magnetic field are the maximum at the minimum magnetic field. In our simulation, whistler chorus are generated at the minimum magnetic field with a peak frequency in agreement with the prediction by WHAMP, a local dispersion relation solver. The waves propagate in both directions along the magnetic field. Waves that propagate to higher magnetic latitude are damped at the boundary by the artificial resistive layers, while waves that propagate to lower latitude towards the equator continue to grow.

  17. Generation of squeezing: magnetic dipoles on cantilevers

    NASA Astrophysics Data System (ADS)

    Seok, Hyojun; Singh, Swati; Steinke, Steven; Meystre, Pierre

    2011-05-01

    We investigate the generation of motional squeezed states in a nano-mechanical cantilever. Our model system consists of a nanoscale cantilever - whose center-of-mass motion is initially cooled to its quantum mechanical ground state - magnetically coupled a classically driven mechanical tuning fork. We show that the magnetic dipole-dipole interaction can produce significant phonon squeezing of the center-of-mass motion of the cantilever, and evaluate the effect of various dissipation channels, including the coupling of the cantilever to a heat bath and phase and amplitude fluctuations in the oscillating field driving the tuning fork. US National Science Foundation, the US Army Research Office, DARPA ORCHID program through a grant from AFOSR.

  18. Analysis and design of short, iron-free dipole magnets

    SciTech Connect

    Harvey, A.R.

    1981-10-21

    Iron-free, dipole magnets are used extensively as steering magnets to correct for the bending, induced by extraneous magnetic fields, of particle beams that are being transported in vacuum. Generally, the dipoles are long enough that the space occupied by the end conductors is small compared to the overall magnet length. In a recent application, however, this criteria did not apply. This has motivated a reanalysis of the characteristics of a system of small aspect ratio (length/diameter) dipoles that are spaced at relatively large axial distances.

  19. Dual aperture dipole magnet with second harmonic component

    DOEpatents

    Praeg, Walter F.

    1985-01-01

    An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

  20. Dual aperture dipole magnet with second harmonic component

    DOEpatents

    Praeg, W.F.

    1983-08-31

    An improved dual aperture dipole electromagnet includes a second-harmonic frequency magnetic guide field winding which surrounds first harmonic frequency magnetic guide field windings associated with each aperture. The second harmonic winding and the first harmonic windings cooperate to produce resultant magnetic waveforms in the apertures which have extended acceleration and shortened reset portions of electromagnet operation.

  1. Development of Cellular Magnetic Dipoles in Magnetotactic Bacteria

    PubMed Central

    Faivre, Damien; Fischer, Anna; Garcia-Rubio, Inés; Mastrogiacomo, Giovanni; Gehring, Andreas U.

    2010-01-01

    Magnetotactic bacteria benefit from their ability to form cellular magnetic dipoles by assembling stable single-domain ferromagnetic particles in chains as a means to navigate along Earth's magnetic field lines on their way to favorable habitats. We studied the assembly of nanosized membrane-encapsulated magnetite particles (magnetosomes) by ferromagnetic resonance spectroscopy using Magnetospirillum gryphiswaldense cultured in a time-resolved experimental setting. The spectroscopic data show that 1), magnetic particle growth is not synchronized; 2), the increase in particle numbers is insufficient to build up cellular magnetic dipoles; and 3), dipoles of assembled magnetosome blocks occur when the first magnetite particles reach a stable single-domain state. These stable single-domain particles can act as magnetic docks to stabilize the remaining and/or newly nucleated superparamagnetic particles in their adjacencies. We postulate that docking is a key mechanism for building the functional cellular magnetic dipole, which in turn is required for magnetotaxis in bacteria. PMID:20713012

  2. Modeling and analysis of optical properties of a gold nanoring based on electric and magnetic dipoles.

    PubMed

    Safaee, S M R; Janipour, M; Karami, M A

    2015-10-01

    The optical behavior of a plane-wave excited gold nanoring (NR), originated from localized surface plasmon resonance is modeled by two coupled electric- and magnetic-point dipoles. Considering the extinction cross-section spectrum, it is found that the electric-dipole effect is dominant in comparison with the magnetic-dipole effect although the magnetic-dipole signature is observable in the near-field response of the NR. In addition, the far-field electromagnetic radiation pattern of the NR verifies the corresponding radiation pattern of the point dipoles. The numerical simulation near-field results are in agreement with the proposed electric- and magnetic-dipole theory.

  3. Dipole relaxation in an electric field

    NASA Astrophysics Data System (ADS)

    Neumann, Richard M.

    1980-07-01

    From Boltzmann's equation, S=k lnΩ, an expression for the orientational entropy, S of a rigid rod (electric dipole) is derived. The free energy of the dipole in an electric field is then calculated as a function of both the dipole's average orientation and the field strength. Application of the equilibrium criterion to the free energy yields the field dependence of the entropy of the dipole. Irreversible thermodynamics is used to derive the general form of the equation of motion of the dipole's average orientation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium.

  4. Classical states of an electric dipole in an external magnetic field: Complete solution for the center of mass and trapped states

    SciTech Connect

    Atenas, Boris; Pino, Luis A. del; Curilef, Sergio

    2014-11-15

    We study the classical behavior of an electric dipole in the presence of a uniform magnetic field. Using the Lagrangian formulation, we obtain the equations of motion, whose solutions are represented in terms of Jacobi functions. We also identify two constants of motion, namely, the energy E and a pseudomomentumC{sup →}. We obtain a relation between the constants that allows us to suggest the existence of a type of bound states without turning points, which are called trapped states. These results are consistent with and complementary to previous results. - Highlights: • Bound states without turning points. • Lagrangian Formulation for an electric dipole in a magnetic field. • Motion of the center of mass and trapped states. • Constants of motion: pseudomomentum and energy.

  5. Magnetic dipole discharges. I. Basic properties

    SciTech Connect

    Stenzel, R. L.; Urrutia, J. M.; Teodorescu-Soare, C. T.; Ionita, C.; Schrittwieser, R.

    2013-08-15

    A simple discharge is described which uses a permanent magnet as a cold cathode and the metallic chamber wall as an anode. The magnet's equator is biased strongly negative, which produces secondary electrons due to the impact of energetic ions. The emitted electrons are highly confined by the strong dipolar magnetic field and the negative potential in the equatorial plane of the magnet. The emitted electrons ionize near the sheath and produce further electrons, which drift across field lines to the anode while the nearly unmagnetized ions are accelerated back to the magnet. A steady state discharge is maintained at neutral pressures above 10{sup −3} mbar. This is the principle of magnetron discharges, which commonly use cylindrical and planar cathodes rather than magnetic dipoles as cathodes. The discharge properties have been investigated in steady state and pulsed mode. Different magnets and geometries have been employed. The role of a background plasma has been investigated. Various types of instabilities have been observed such as sheath oscillations, current-driven turbulence, relaxation instabilities due to ionization, and high frequency oscillations created by sputtering impulses, which are described in more detail in companion papers. The discharge has also been operated in reactive gases and shown to be useful for sputtering applications.

  6. Concentric Titled Double-Helix Dipole Magnets

    SciTech Connect

    Rainer Meinke, Ph.D; Carl Goodzeit; Millicent Ball, Ph.D

    2003-09-05

    The high magnetic fields required for future accelerator magnets can only be achieved with Nb3Sn, other A15 or HTS type conductors, which are brittle and sensitive to mechanical strain. The traditional ''cosine-theta'' dipole configuration has intrinsic drawbacks that make it difficult and expensive to employ such conductors in these designs. Some of these problems involve (1) difficulty in applying enough pre-stress to counteract Lorentz forces without compromising conductor performance; (2) small minimum bend radii of the conductor necessitating the intricate wind-and-react coil fabrication; (3) complex spacers in particular for coil ends and expensive tooling for coil fabrication; (4) typically only 2/3 of the coil aperture can be used with achievable field uniformity.

  7. Helical Dipole Magnets for Polarized Protons in RHIC

    NASA Astrophysics Data System (ADS)

    Syphers, M.; Courant, E.; Fischer, W.; Luccio, A.; Mariam, F.; Peggs, S.; Pilat, F.; Roser, T.; Tepikian, S.; Tsoupas, N.; Willen, E.; Katayama, T.; Hatanaka, K.; Kawaguchi, T.; Okamura, M.; Tominaka, T.; Wu, H.; Ptitsin, V.; Shatunov, Y.

    1997-05-01

    The Brookhaven Relativistic Heavy Ion Collider (RHIC) will be able to support experiments using polarized proton beams. Siberian Snakes are used to maintain polarization in this high energy superconducting collider. To make efficient use of available space while taking advantage of high field superconducting magnets, 4 Tesla helical dipole magnets will be used. These magnets generate a central dipole field in which the field direction rotates through 360^circ about the longitudinal axis over the length of the device. An arrangement of four such magnets can produce the desired change in the spin direction while keeping the proton orbit outside of the ``Snake'' unaltered. Similar magnet arrangements will be used to produce longitudinal polarization at the two major interaction points in RHIC. The basic requirements and layout of these magnets are described, as well as tolerances on field quality and integrated field strengths. First results of tests of prototype helical magnets will be discussed.

  8. How to Introduce the Magnetic Dipole Moment

    ERIC Educational Resources Information Center

    Bezerra, M.; Kort-Kamp, W. J. M.; Cougo-Pinto, M. V.; Farina, C.

    2012-01-01

    We show how the concept of the magnetic dipole moment can be introduced in the same way as the concept of the electric dipole moment in introductory courses on electromagnetism. Considering a localized steady current distribution, we make a Taylor expansion directly in the Biot-Savart law to obtain, explicitly, the dominant contribution of the…

  9. Gyre-driven decay of the Earth's magnetic dipole.

    PubMed

    Finlay, Christopher C; Aubert, Julien; Gillet, Nicolas

    2016-01-01

    Direct observations indicate that the magnitude of the Earth's magnetic axial dipole has decreased over the past 175 years; it is now 9% weaker than it was in 1840. Here we show how the rate of dipole decay may be controlled by a planetary-scale gyre in the liquid metal outer core. The gyre's meridional limbs on average transport normal polarity magnetic flux equatorward and reverse polarity flux poleward. Asymmetry in the geomagnetic field, due to the South Atlantic Anomaly, is essential to the proposed mechanism. We find that meridional flux advection accounts for the majority of the dipole decay since 1840, especially during times of rapid decline, with magnetic diffusion making an almost steady contribution generally of smaller magnitude. Based on the morphology of the present field, and the persistent nature of the gyre, the current episode of dipole decay looks set to continue, at least for the next few decades. PMID:26814368

  10. Gyre-driven decay of the Earth's magnetic dipole

    PubMed Central

    Finlay, Christopher C.; Aubert, Julien; Gillet, Nicolas

    2016-01-01

    Direct observations indicate that the magnitude of the Earth's magnetic axial dipole has decreased over the past 175 years; it is now 9% weaker than it was in 1840. Here we show how the rate of dipole decay may be controlled by a planetary-scale gyre in the liquid metal outer core. The gyre's meridional limbs on average transport normal polarity magnetic flux equatorward and reverse polarity flux poleward. Asymmetry in the geomagnetic field, due to the South Atlantic Anomaly, is essential to the proposed mechanism. We find that meridional flux advection accounts for the majority of the dipole decay since 1840, especially during times of rapid decline, with magnetic diffusion making an almost steady contribution generally of smaller magnitude. Based on the morphology of the present field, and the persistent nature of the gyre, the current episode of dipole decay looks set to continue, at least for the next few decades. PMID:26814368

  11. Gyre-driven decay of the Earth's magnetic dipole

    NASA Astrophysics Data System (ADS)

    Finlay, Christopher C.; Aubert, Julien; Gillet, Nicolas

    2016-01-01

    Direct observations indicate that the magnitude of the Earth's magnetic axial dipole has decreased over the past 175 years; it is now 9% weaker than it was in 1840. Here we show how the rate of dipole decay may be controlled by a planetary-scale gyre in the liquid metal outer core. The gyre's meridional limbs on average transport normal polarity magnetic flux equatorward and reverse polarity flux poleward. Asymmetry in the geomagnetic field, due to the South Atlantic Anomaly, is essential to the proposed mechanism. We find that meridional flux advection accounts for the majority of the dipole decay since 1840, especially during times of rapid decline, with magnetic diffusion making an almost steady contribution generally of smaller magnitude. Based on the morphology of the present field, and the persistent nature of the gyre, the current episode of dipole decay looks set to continue, at least for the next few decades.

  12. Properties of the superconductor in accelerator dipole magnets

    NASA Astrophysics Data System (ADS)

    Teravest, Derk

    Several aspects of the application of superconductors to high field dipole magnets for particle accelerators are discussed. The attention is focused on the 10 tesla (1 m model) magnet that is envisaged for the future Large Hadron Collider (LHC) accelerator. The basic motivation behind the study is the intention of employing superconductors to their utmost performance. An overview of practical supercomputers, their applications and their impact on high field dipole magnets used for particle accelerators, is presented. The LHC reference design for the dipole magnets is outlined. Several models were used to study the influence of a number of factors in the shape and in particular, the deviation from the shape that is due to the flux flow state. For the investigated extrinsic and intrinsic factors, a classification can be made with respect to the effect on the shape of the characteristic of a multifilamentary wire. The optimization of the coil structure for high field dipole magnets, with respect to the field quality is described. An analytical model for solid and hollow filaments, to calculate the effect of filament magnetization in the quality of the dipole field, is presented.

  13. The radiofrequency magnetic dipole discharge

    NASA Astrophysics Data System (ADS)

    Martines, E.; Zuin, M.; Marcante, M.; Cavazzana, R.; Fassina, A.; Spolaore, M.

    2016-05-01

    This paper describes a novel and simple concept of plasma source, which is able to produce a radiofrequency magnetized discharge with minimal power requirements. The source is based on the magnetron concept and uses a permanent magnet as an active electrode. The dipolar field produced by the magnet confines the electrons, which cause further ionization, thus producing a toroidally shaped plasma in the equatorial region around the electrode. A plasma can be ignited with such scheme with power levels as low as 5 W. Paschen curves have been built for four different working gases, showing that in Helium or Neon, plasma breakdown is easily obtained also at atmospheric pressure. The plasma properties have been measured using a balanced Langmuir probe, showing that the electron temperature is around 3-4 eV and higher in the cathode proximity. Plasma densities of the order of 1016 m-3 have been obtained, with a good positive scaling with applied power. Overall, the electron pressure appears to be strongly correlated with the magnetic field magnitude in the measurement point.

  14. Classical states of an electric dipole in an external magnetic field: Complete solution for the center of mass and trapped states

    NASA Astrophysics Data System (ADS)

    Atenas, Boris; del Pino, Luis A.; Curilef, Sergio

    2014-11-01

    We study the classical behavior of an electric dipole in the presence of a uniform magnetic field. Using the Lagrangian formulation, we obtain the equations of motion, whose solutions are represented in terms of Jacobi functions. We also identify two constants of motion, namely, the energy E and a pseudomomentum C →. We obtain a relation between the constants that allows us to suggest the existence of a type of bound states without turning points, which are called trapped states. These results are consistent with and complementary to previous results.

  15. Magnetic dipoles at topological defects in the Meissner state of a nanostructured superconductor

    NASA Astrophysics Data System (ADS)

    Ge, Jun-Yi; Gladilin, Vladimir N.; Xue, Cun; Tempere, Jacques; Devreese, Jozef T.; Van de Vondel, Joris; Zhou, Youhe; Moshchalkov, Victor V.

    2016-06-01

    In a magnetic field, superconductivity is manifested by total magnetic field expulsion (Meissner effect) or by the penetration of integer multiples of the flux quantum Φ0. Here we present experimental results revealing magnetic dipoles formed by Meissner current flowing around artificially introduced topological defects (lattice of antidots). By using scanning Hall probe microscopy, we have detected ordered magnetic dipole lattice generated at spatially periodic antidots in a Pb superconducting film. While the conventional homogeneous Meissner state breaks down, the total magnetic flux of the magnetic dipoles remains quantized and is equal to zero. The observed magnetic dipoles strongly depend on the intensity and direction of the locally flowing Meissner current, making the magnetic dipoles an effective way to monitor the local supercurrent. We have also investigated the first step of the vortex depinning process, where, due to the generation of magnetic dipoles, the pinned Abrikosov vortices are deformed and shifted from their original pinning sites.

  16. Magnetic dipole localization based on magnetic gradient tensor data at a single point

    NASA Astrophysics Data System (ADS)

    Gang, Yin; Yingtang, Zhang; Hongbo, Fan; Zhining, Li

    2014-01-01

    Magnetic dipole localization methods that rely on measurement of the magnetic field vector are compromised by the relatively strong background geomagnetic field. A localization method that uses only magnetic gradient tensor data is proposed. The localization equations are established by transforming Euler's equation of degree -3 into degree -4 and using the orthogonality of the intermediate eigenvector of the magnetic gradient tensor that is produced by a magnetic dipole and the source-sensor displacement vector. To measure the quantities required in the localization equations, we designed a magnetic gradient tensor system in which finite differences are used to approximate the first- and second-order spatial gradients of magnetic field components. Numerical simulations show that the proposed method can accurately and uniquely solve for the location of a magnetic dipole in the presence of the geomagnetic field, and the experimental results show the superiority and the practicability of the proposed method.

  17. Evolution of the dipole geomagnetic field. Observations and models

    NASA Astrophysics Data System (ADS)

    Reshetnyak, M. Yu.; Pavlov, V. E.

    2016-01-01

    The works on paleomagnetic observations of the dipole geomagnetic field, its variations, and reversals in the last 3.5 billion years have been reviewed. It was noted that characteristic field variations are related to the evolution of the convection processes in the liquid core due to the effect of magnetic convection and solid core growth. Works on the geochemistry and energy budget of the Earth's core, the effect of the solid core on convection and the generation of the magnetic field, dynamo models are also considered. We consider how core growth affects the magnetic dipole generation and variations, as well as the possibility of magnetic field generation up to the appearance of the solid core. We also pay attention to the fact that not only the magnetic field but also its configuration and time variations, which are caused by the convection evolution in the core on geological timescales, are important factors for the biosphere.

  18. Strongly magnetized rotating dipole in general relativity

    NASA Astrophysics Data System (ADS)

    Pétri, J.

    2016-10-01

    Context. Electromagnetic waves arise in many areas of physics. Solutions are difficult to find in the general case. Aims: We numerically integrate Maxwell equations in a 3D spherical polar coordinate system. Methods: Straightforward finite difference methods would lead to a coordinate singularity along the polar axis. Spectral methods are better suited for such artificial singularities that are related to the choice of a coordinate system. When the radiating object rotates like a star, for example, special classes of solutions to Maxwell equations are worthwhile to study, such as quasi-stationary regimes. Moreover, in high-energy astrophysics, strong gravitational and magnetic fields are present especially around rotating neutron stars. Results: To study such systems, we designed an algorithm to solve the time-dependent Maxwell equations in spherical polar coordinates including general relativity and quantum electrodynamical corrections to leading order. As a diagnostic, we computed the spin-down luminosity expected for these stars and compared it to the classical or non-relativistic and non-quantum mechanical results. Conclusions: Quantum electrodynamics leads to an irrelevant change in the spin-down luminosity even for a magnetic field of about the critical value of 4.4 × 109 T. Therefore the braking index remains close to its value for a point dipole in vacuum, namely n = 3. The same conclusion holds for a general-relativistic quantum electrodynamically corrected force-free magnetosphere.

  19. Longitudinal Gradient Dipole Magnet Prototype for APS at ANL

    DOE PAGESBeta

    Kashikhin, V. S.; Borland, M.; Chlachidze, G.; Decker, G.; Dejus, R.; DiMarco, J.; Doose, C. L.; Gardner, T. J.; Harding, D. J.; Jaski, M. S.; et al

    2016-01-26

    We planned an upgrade of the Advanced Photon Source at Argonne National Laboratory (ANL). The main goal of the upgrade is to improve the storage ring performance based on more advanced optics. One of the key magnet system elements is bending dipole magnets having a field strength change along the electron beam path. Moreover, a prototype of one such longitudinal gradient dipole magnet has been designed, built, and measured in a collaborative effort of ANL and Fermilab. Our paper discusses various magnetic design options, the selected magnet design, and the fabrication technology. The prototype magnet has been measured by rotationalmore » coils, a stretched wire, and a Hall probe. Measurement results are discussed and compared with simulations.« less

  20. Singular Behaviour of the Electrodynamic Fields of an Oscillating Dipole

    ERIC Educational Resources Information Center

    Leung, P. T.

    2008-01-01

    The singularity of the exact electromagnetic fields is derived to include the "source terms" for harmonically oscillating electric (and magnetic) dipoles, so that the fields will be consistent with the full Maxwell equations with a source. It is shown explicitly, as somewhat expected, that the same [delta]-function terms for the case of static…

  1. The Case of the Disappearing Magnetic Dipole

    ERIC Educational Resources Information Center

    Gough, W.

    2008-01-01

    The problem of an oscillating magnetic dipole at the centre of a lossless dielectric spherical shell is considered. For simplicity, the free-space wavelength is taken to be much greater than the shell radii, but the relative permittivity [epsilon][subscript r] of the shell is taken as much greater than unity, so the wavelength in the shell could…

  2. Cost of high-field Nb/sub 3/Sn and NbTi accelerator dipole magnets

    SciTech Connect

    Hassenzahl, W.V.

    1982-11-01

    Future high-energy proton accelerators will likely require very high magnetic fields if the size of the accelerator and associated experimental areas are to be limited to dimensions that can be accomodated by the terrain at convenient sites. Two commercially available superconductors can be used to produce magnetic fields of 10T or more. The first is Nb/sub 3/Sn, which can operate in pool boiling helium at 4.4 K. The second is NbTi, which must be cooled to about 1.9 K in superfluid helium. In this paper the costs of 5-cm-bore, 6-m-long magnets made of these materials and operating at fields from 5 to 11 T are compared. At 10 T the capital cost of a NbTi coil operating in superfluid helium is 35% less than the cost of a Nb/sub 3/Sn coil. The cost of the NbTi coil is still 10% less after the differential operating costs that will be incurred over the life of the accelerator are included. The results presented here are a summary of a detailed analysis of these costs given in a separate report.

  3. Circular current loops, magnetic dipoles and spherical harmonic analysis.

    USGS Publications Warehouse

    Alldredge, L.R.

    1980-01-01

    Spherical harmonic analysis (SHA) is the most used method of describing the Earth's magnetic field, even though spherical harmonic coefficients (SHC) almost completely defy interpretation in terms of real sources. Some moderately successful efforts have been made to represent the field in terms of dipoles placed in the core in an effort to have the model come closer to representing real sources. Dipole sources are only a first approximation to the real sources which are thought to be a very complicated network of electrical currents in the core of the Earth. -Author

  4. Dipole-exchange spin waves in magnetic nanomaterials

    NASA Astrophysics Data System (ADS)

    Nguyen, Thi Hoa

    The aim of this thesis is to investigate the dipole-exchange spin waves in several low-dimensional ferromagnetic nanosystems. A microscopic theory is employed based on a Hamiltonian approach and a discrete lattice model. The Hamiltonian includes both the exchange and the magnetic dipole-dipole interactions, as well as the single-ion anisotropy and a Zeeman term for an externally applied magnetic field. Some of the advantages of this microscopic theory over the macroscopic methods are that it is convenient for describing the dynamical properties of samples where the magnetization may be spatially inhomogeneous, and it does not require the specification of phenomenological boundary conditions at the sample surfaces. The spin wave frequencies are obtained by employing a boson operator method with a diagonalization procedure. The spectral intensity, spin wave amplitudes and effective pinning are also studied within a Green function theory. The spin wave properties are first studied for ultrathin ferromagnetic films with simple cubic, body-centered cubic and face-centered cubic lattice structures. Results are deduced for the spin wave frequencies as a function of the in-plane wave vector, the magnetic field applied either parallel or perpendicular to the film surfaces, and the material parameters. The spin wave properties are shown to depend sensitively on the lattice structures in certain wave-vector regimes. Next we carry out spin wave calculations for individual (non-interacting) ferromagnetic stripes or wires. The numerical results are compared with the macroscopic theories and with the experimental data, where available. Then we examine the role of the long-range dipole-dipole interactions between stripes on the spin waves for two different types of stripe arrays. The coupling is found to depend on the array geometry and the direction of the applied field. Comparison of our results with experimental data (e.g., for Permalloy) shows a good agreement, confirming the

  5. The case of the disappearing magnetic dipole

    NASA Astrophysics Data System (ADS)

    Gough, W.

    2008-03-01

    The problem of an oscillating magnetic dipole at the centre of a lossless dielectric spherical shell is considered. For simplicity, the free-space wavelength is taken to be much greater than the shell radii, but the relative permittivity ɛr of the shell is taken as much greater than unity, so the wavelength in the shell could be comparable with its dimensions. The vector potential in all regions is found. Under certain conditions, involving the shell radii, the frequency and ɛr, the vector potential outside the shell appears to be infinite. This is impossible, so one must conclude that the dipole moment vanishes. This result, a 'disappearing dipole', although strange, can be justified. Although this paper is aimed primarily at readers with a strong interest in fundamental physics, it could be introduced as an interesting result in an undergraduate course on electromagnetism.

  6. MAGNETIC MODELING VS MEASUREMENTS OF THE DIPOLES FOR THE JLAB 10 KW FREE ELECTRON LASER UPGRADE

    SciTech Connect

    David Douglas; Robin Wines; Tom Hiatt; George Biallas; Kenneth Baggett; T.J. Schultheiss; V.A. Christina; J.W. Rathke; A. Smirnov; D. Newsham; Y. Luo; D. Yu

    2003-05-01

    Magnetic measurements of the six families of dipoles for the infrared Free Electron Laser Upgrade at the Thomas Jefferson National Accelerator Facility (Jlab) are compared to the magnetic models on which their design is based. The magnets were designed in parallel by three organizations. They used ANSYS, Radia or Opera 3D as a 3D magnetic modeling program. Comparison of the discrepancies between model and magnet measurement is presented along with analysis of their potential causes. These dipoles operate in two field ranges. The Injector/ Extractor Dipoles operate around 0.05 T and the Arc Dipoles and Optical Chicane Dipoles operate between 0.22 to 0.71 T. All magnets are required to meet core field and field integral flatness to parts in 104 over their good field region.

  7. Two-dimensional PIC simulations of double layers in the upward current region of the aurora with quasi-dipole magnetic fields

    NASA Astrophysics Data System (ADS)

    Nishikawa, Kenichi; Almomany, Abedalmohdi; Wells, Buren

    2016-04-01

    The results of applying two-dimensional particle-in-cell code to study the development of potential structures in the upward current region of an auroral plasma where quasi-dipole magnetic fields are applied is investigated. Within the resulting simulations a double layer (DL) forms in the auroral potential structure in the couterstreaming expansion area of cold plasma from bottom (ionospheric side) and hot plasma from top (magnetospheric side). A V-shaped potential structure is generated within the expanding plasmas with transversely non-uniform converging perpendicular electric field. Due to the inclusion of the more realistic magnetic fields in the auroal region (stronger in the ionospheric side) this V-shaped potential structure is very evident. We have observed the following dynamical evolutions: (1) recurring formation of the DL, (2) downward motion of the DL over the distance of thousands of Debye lengths, and (3) collapse of the existing double layer shortly after a new DL has formed near the top of the simulation region in the hot magmnetospheric plasma. The evolution of the DL and electron hole formation correlates well to data obtained through satellite observation.

  8. Dipole-dipole interaction and its concentration dependence of magnetic fluid evaluated by alternating current hysteresis measurement

    NASA Astrophysics Data System (ADS)

    Ota, Satoshi; Yamada, Tsutomu; Takemura, Yasushi

    2015-05-01

    Magnetic nanoparticles (MNPs) are used as therapeutic and diagnostic tools, such as for treating hyperthermia and in magnetic particle imaging, respectively. Magnetic relaxation is one of the heating mechanisms of MNPs. Brownian and Néel relaxation times are calculated conventional theories; however, the influence of dipole-dipole interactions has not been considered in conventional models. In this study, water-dispersed MNPs of different concentrations and MNPs fixed with an epoxy bond were prepared. dc and ac hysteresis loops for each sample were measured. With respect to both dc and ac hysteresis loops, magnetization decreased with the increase in MNP concentration because of inhibition of magnetic moment rotation due to dipole-dipole interactions. Moreover, intrinsic loss power (ILP) was estimated from the areas of the ac hysteresis loops. The dependence of ILP on the frequency of the magnetic field was evaluated for each MNP concentration. The peak frequency of ILP increased with the decrease in MNP concentration. These peaks were due to Brownian relaxation, as they were not seen with the fixed sample. This indicates that the Brownian relaxation time became shorter with lower MNP concentration, because the weaker dipole-dipole interactions with lower concentrations suggested that the magnetic moments could rotate more freely.

  9. The protons and electrons trapped in the Jovian dipole magnetic field region and their interaction with Io

    NASA Technical Reports Server (NTRS)

    Simpson, J. A.; Hamilton, D. C.; Mckibben, R. B.; Mogro-Campero, A.; Pyle, K. R.; Tuzzolino, A. J.

    1974-01-01

    Detailed analysis of electrons equal to or greater than 3 MeV and of protons 0.5 to 1.8 MeV and equal to or greater than 35 MeV for both the inbound and the outbound passes of the Pioneer 10 spacecraft. Conclusive evidence is obtained that the trapped radiation in Jupiter's inner magnetosphere is maintained and supplied by inward diffusion from the outer regions of the trapped radiation zone. It is shown that the time required for isotropization of an anisotropic flux by pitch angle scattering inside L approximately equal to 6 is long in comparison with the time required for particles to diffuse inward from L approximately equal to 6 to L approximately equal to 3, that the high-energy protons were not injected at high energies by the Crand (cosmic ray albedo neutron decay) process but were accelerated in the magnetosphere of Jupiter, and that the main conclusions of this analysis are unaffected by use of either the D sub 1 or the D sub 2 magnetic field models. Theoretical studies of the capture of trapped electrons and protons by Io have been carried out, and it is found that the probability of capture by Io depends strongly upon the particle species and kinetic energy.

  10. Magnetic dipole-dipole sensing at atomic scale using electron spin resonance STM

    NASA Astrophysics Data System (ADS)

    Choi, T.; Paul, W.; Rolf-Pissarczyk, S.; MacDonald, A.; Yang, K.; Natterer, F. D.; Lutz, C. P.; Heinrich, A. J.

    Magnetometry having both high magnetic field sensitivity and atomic resolution has been an important goal for applications in diverse fields covering physics, material science, and biomedical science. Recent development of electron spin resonance STM (ESR-STM) promises coherent manipulation of spins and studies on magnetic interaction of artificially built nanostructures, leading toward quantum computation, simulation, and sensors In ESR-STM experiments, we find that the ESR signal from an Fe atom underneath a STM tip splits into two different frequencies when we position an additional Fe atom nearby. We measure an ESR energy splitting that decays as 1/r3 (r is the separation of the two Fe atoms), indicating that the atoms are coupled through magnetic dipole-dipole interaction. This energy and distance relation enables us to determine magnetic moments of atoms and molecules on a surface with high precision in energy. Unique and advantageous aspects of ESR-STM are the atom manipulation capabilities, which allow us to build atomically precise nanostructures and examine their interactions. For instance, we construct a dice cinque arrangement of five Fe atoms, and probe their interaction and energy degeneracy. We demonstrate the ESR-STM technique can be utilized for quantum magnetic sensors.

  11. Magnetic Dipole Interaction on a Square Lattice

    NASA Astrophysics Data System (ADS)

    Zabel, Hartmut; Ewerlin, Melanie; Demirbas, Derya; Bruessing, Frank; Kronast, Florian

    2013-03-01

    We have studied interactions and phase transitions of circular magnetic islands with dipole character on a square lattice. By lithographic means we have prepared square patterns of periodicity 300 nm decorated with circular islands of 150 nm diameter using Pd0.87Fe0.13 as magnetic alloy. Below the Curie temperature of 260 K each island is in a ferromagnetic, single domain state with dipolar character and zero in-plane anisotropy. Below a second transition temperature the dipoles start to interact. MOKE measurements show a characteristic change in the magnetic hysteresis for temperatures below 160 K with increasing coercivity for decreasing temperatures. Furthermore, below the second transition the in-plane hysteresis becomes anisotropic, having an easy axis along [10] direction and a hard axis along [11] direction. SPEEM experiments at BESSY II of the HZB with circularly polarized incident photons tuned to the Fe L3 - edge show clearly the development of dipolar chains below the second phase transition that increase in length with decreasing temperature. Neighbouring chains are found to be oriented parallel as well as antiparallel. This work was supported by DFG-SFB 491 and BMBF under contracts 05K10PC2 and 05ES3xBA/5

  12. Decomposing the electromagnetic response of magnetic dipoles to determine the geometric parameters of a dipole conductor

    NASA Astrophysics Data System (ADS)

    Desmarais, Jacques K.; Smith, Richard S.

    2016-03-01

    A novel automatic data interpretation algorithm is presented for modelling airborne electromagnetic (AEM) data acquired over resistive environments, using a single-component (vertical) transmitter, where the position and orientation of a dipole conductor is allowed to vary in three dimensions. The algorithm assumes that the magnetic fields produced from compact vortex currents are expressed as a linear combinations of the fields arising from dipoles in the subsurface oriented parallel to the [1, 0, 0], [0, 1, 0], and [0, 0, 1], unit vectors. In this manner, AEM responses can be represented as 12 terms. The relative size of each term in the decomposition can be used to determine geometrical information about the orientation of the subsurface conductivity structure. The geometrical parameters of the dipole (location, depth, dip, strike) are estimated using a combination of a look-up table and a matrix inverted in a least-squares sense. Tests on 703 synthetic models show that the algorithm is capable of extracting most of the correct geometrical parameters of a dipole conductor when three-component receiver data is included in the interpretation procedure. The algorithm is unstable when the target is perfectly horizontal, as the strike is undefined. Ambiguities may occur in predicting the orientation of the dipole conductor if y-component data is excluded from the analysis. Application of our approach to an anomaly on line 15 of the Reid Mahaffy test site yields geometrical parameters in reasonable agreement with previous authors. However, our algorithm provides additional information on the strike and offset from the traverse line of the conductor. Disparities in the values of predicted dip and depth are within the range of numerical precision. The index of fit was better when strike and offset were included in the interpretation procedure. Tests on the data from line 15701 of the Chibougamau MEGATEM survey shows that the algorithm is applicable to situations where

  13. Free induction decay caused by a dipole field

    NASA Astrophysics Data System (ADS)

    Ziener, C. H.; Kurz, F. T.; Kampf, T.

    2015-03-01

    We analyze the free induction decay of nuclear spins under the influence of restricted diffusion in a magnetic dipole field around cylindrical objects. In contrast to previous publications no restrictions or simplifications concerning the diffusion process are made. By directly solving the Bloch-Torrey equation, analytical expressions for the magnetization are given in terms of an eigenfunction expansion. The field strength-dependent complex nature of the eigenvalue spectrum significantly influences the shape of the free induction decay. As the dipole field is the lowest order of the multipole expansion, the obtained results are important for understanding fundamental mechanisms of spin dephasing in many other applied fields of nuclear magnetic resonance such as biophysics or material science. The analytical methods are applied to interpret the spin dephasing in the free induction decay in cardiac muscle and skeletal muscle. A simple expression for the relevant transverse relaxation time is found in terms of the underlying microscopic parameters of the muscle tissue. The analytical results are in agreement with experimental data. These findings are important for the correct interpretation of magnetic resonance images for clinical diagnosis at all magnetic field strengths and therapy of cardiovascular diseases.

  14. Free induction decay caused by a dipole field.

    PubMed

    Ziener, C H; Kurz, F T; Kampf, T

    2015-03-01

    We analyze the free induction decay of nuclear spins under the influence of restricted diffusion in a magnetic dipole field around cylindrical objects. In contrast to previous publications no restrictions or simplifications concerning the diffusion process are made. By directly solving the Bloch-Torrey equation, analytical expressions for the magnetization are given in terms of an eigenfunction expansion. The field strength-dependent complex nature of the eigenvalue spectrum significantly influences the shape of the free induction decay. As the dipole field is the lowest order of the multipole expansion, the obtained results are important for understanding fundamental mechanisms of spin dephasing in many other applied fields of nuclear magnetic resonance such as biophysics or material science. The analytical methods are applied to interpret the spin dephasing in the free induction decay in cardiac muscle and skeletal muscle. A simple expression for the relevant transverse relaxation time is found in terms of the underlying microscopic parameters of the muscle tissue. The analytical results are in agreement with experimental data. These findings are important for the correct interpretation of magnetic resonance images for clinical diagnosis at all magnetic field strengths and therapy of cardiovascular diseases.

  15. Magnetic fields at uranus.

    PubMed

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

    1986-07-01

    The magnetic field experiment on the Voyager 2 spacecraft revealed a strong planetary magnetic field of Uranus and an associated magnetosphere and fully developed bipolar masnetic tail. The detached bow shock wave in the solar wind supersonic flow was observed upstream at 23.7 Uranus radii (1 R(U) = 25,600 km) and the magnetopause boundary at 18.0 R(U), near the planet-sun line. A miaximum magnetic field of 413 nanotesla was observed at 4.19 R(U ), just before closest approach. Initial analyses reveal that the planetary magnetic field is well represented by that of a dipole offset from the center of the planet by 0.3 R(U). The angle between Uranus' angular momentum vector and the dipole moment vector has the surprisingly large value of 60 degrees. Thus, in an astrophysical context, the field of Uranus may be described as that of an oblique rotator. The dipole moment of 0.23 gauss R(3)(U), combined with the large spatial offset, leads to minimum and maximum magnetic fields on the surface of the planet of approximately 0.1 and 1.1 gauss, respectively. The rotation period of the magnetic field and hence that of the interior of the planet is estimated to be 17.29+/- 0.10 hours; the magnetotail rotates about the planet-sun line with the same period. Thelarge offset and tilt lead to auroral zones far from the planetary rotation axis poles. The rings and the moons are embedded deep within the magnetosphere, and, because of the large dipole tilt, they will have a profound and diurnally varying influence as absorbers of the trapped radiation belt particles.

  16. Field quality aspects of CBA superconducting magnets

    SciTech Connect

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

    1983-01-01

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

  17. Nb3Sn accelerator magnet technology scale up using cos-theta dipole coils

    SciTech Connect

    Nobrega, F.; Andreev, N.; Ambrosio, G.; Barzi, E.; Bossert, R.; Carcagno, R.; Chlachidze, G.; Feher, S.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.J.; /Fermilab

    2007-06-01

    Fermilab is working on the development of Nb{sub 3}Sn accelerator magnets using shell-type dipole coils and the wind-and-react method. As a part of the first phase of technology development, Fermilab built and tested six 1 m long dipole model magnets and several dipole mirror configurations. The last three dipoles and two mirrors reached their design fields of 10-11 T. The technology scale up phase has started by building 2 m and 4 m dipole coils and testing them in a mirror configuration in which one of the two coils is replaced by a half-cylinder made of low carbon steel. This approach allows for shorter fabrication times and extensive instrumentation preserving almost the same level of magnetic field and Lorentz forces in the coils as in a complete dipole model magnet. This paper presents details on the 2 m (HFDM07) and 4 m long (HFDM08) Nb{sub 3}Sn dipole mirror magnet design and fabrication technology, as well as the magnet test results which are compared with 1 m long models.

  18. Effect of dipole-dipole interaction on self-control magnetization oscillation in double-domain nanomagnets

    NASA Astrophysics Data System (ADS)

    Gao, Y. J.; Guo, Y. J.; Liu, J.-M.

    2012-03-01

    A double-domain model with long-range dipole-dipole interaction is proposed to investigate the self-oscillation of magnetization in nano-magnetic systems driven by self-controlled spin-polarized current. The dynamic behavior of magnetization oscillation is calculated by a modified Landau-Lifshitz-Gilbert equation in order to evaluate the effects of the long-range dipole-dipole interaction. While the self-oscillation of magnetization can be maintained substantially, several self-oscillation regions are experienced as the dipole-dipole interaction increases gradually.

  19. Breakdown of the dipole approximation in strong-field ionization.

    PubMed

    Ludwig, A; Maurer, J; Mayer, B W; Phillips, C R; Gallmann, L; Keller, U

    2014-12-12

    We report the breakdown of the electric dipole approximation in the long-wavelength limit in strong-field ionization with linearly polarized few-cycle mid-infrared laser pulses at intensities on the order of 10¹³ W/cm². Photoelectron momentum distributions were recorded by velocity map imaging and projected onto the beam propagation axis. We observe an increasing shift of the peak of this projection opposite to the beam propagation direction with increasing laser intensities. From a comparison with semiclassical simulations, we identify the combined action of the magnetic field of the laser pulse and the Coulomb potential as the origin of our observations. PMID:25541770

  20. Dynamics of the magnetic moments for chain of dipoles in domain wall

    NASA Astrophysics Data System (ADS)

    Shutyıˇ, Anatoliy M.; Sementsov, Dmitriy I.

    2016-03-01

    We report on the dynamics of the magnetic moment numerically simulated for a chain of the magnetic nanodots coupled through the dipole-dipole interaction and in the presence of the magnetic anisotropy of various types. It is shown that a static field applied to the system causes specific fluctuations of the transverse components of the magnetic moment leading to a sequence of the oscillation trains observed in the domain wall. Various oscillation modes governed by the external alternating field are revealed. The influence of the unidirectional and uniaxial anisotropy ("easy-plane" and "easy axis" anisotropy) on the system behavior is described.

  1. 6. 4 Tesla dipole magnet for the SSC

    SciTech Connect

    Taylor, C.E.; Caspi, S.; Gilbert, W.; Meuser, R.; Mirk, K.; Peters, C.; Scanlan, R.; Dahl, P.; Cottingham, J.; Hassenzahl, W.

    1985-05-01

    A design is presented for a dipole magnet suitable for the proposed SSC facility. Test results are given for model magnets of this design 1 m long and 4.5 m long. Flattened wedge-shaped cables (''keystoned'') are used in a graded, two-layer ''cos theta'' configuration with three wedges to provide sufficient field uniformity and mechanical rigidity. Stainless steel collars 15 mm wide, fastened with rectangular keys, provide structural support, and there is a ''cold'' iron flux return. The outer-layer cable has 30 strands of 0.0255 in. dia NbTi multifilamentary wire with Cu/S.C. = 1.8, and the inner has 23 strands of .0318 in. dia wire with Cu/S.C. = 1.3. Performance data is given including training behavior, winding stresses, collar deformation, and field uniformity.

  2. Fast computation of a gated dipole field.

    PubMed

    Mengov, George; Georgiev, Kalin; Pulov, Stefan; Trifonov, Trifon; Atanassov, Krassimir

    2006-12-01

    We address the need to develop efficient algorithms for numerical simulation of models, based in part or entirely on adaptive resonance theory. We introduce modifications that speed up the computation of the gated dipole field (GDF) in the Exact ART neural network. The speed increase of our solution amounts to at least an order of magnitude for fields with more than 100 gated dipoles. We adopt a 'divide and rule' approach towards the original GDF differential equations by grouping them into three categories, and modify each category in a separate way. We decouple the slow-dynamics part - the neurotransmitters from the rest of system, solve their equations analytically, and adapt the solution to the remaining fast-dynamics processes. Part of the node activations are integrated by an unsophisticated numerical procedure switched on and off according to rules. The remaining activations are calculated at equilibrium. We implement this logic in a Generalized Net (GN) - a tool for parallel processes simulation which enables a fresh look at developing efficient models. Our software implementation of generalized nets appears to add little computational overhead.

  3. MAGNETIC MEASUREMENT OF THE 10 KW, IR FEL 180 DEGREE DIPOLE

    SciTech Connect

    Kenneth Baggett; George Biallas; Donald Bullard; Jeffery Dail; David Douglas; Tommy Hiatt; Michael Mccrea

    2003-05-01

    A family of large bending dipoles has been magnetically measured to support the 10 kW IR-FEL upgrade. This upgrade will allow for a wider wavelength range and an increase in the machine energy to operate between 80 MeV/c and 210 MeV/c. The dipole magnets allow the beam to bend 180 degrees over a 1 meter radius. The requirements for these magnets include varying field strengths, large horizontal apertures and parts in 10,000 field homogeneity as well as setability of core and integrated field. This paper will describe the process involved in measuring and achieving these requirements.

  4. Many particle magnetic dipole-dipole and hydrodynamic interactions in magnetizable stent assisted magnetic drug targeting

    NASA Astrophysics Data System (ADS)

    Cregg, P. J.; Murphy, Kieran; Mardinoglu, Adil; Prina-Mello, Adriele

    2010-08-01

    The implant assisted magnetic targeted drug delivery system of Avilés, Ebner and Ritter is considered both experimentally ( in vitro) and theoretically. The results of a 2D mathematical model are compared with 3D experimental results for a magnetizable wire stent. In this experiment a ferromagnetic, coiled wire stent is implanted to aid collection of particles which consist of single domain magnetic nanoparticles (radius ≈10 nm). In order to model the agglomeration of particles known to occur in this system, the magnetic dipole-dipole and hydrodynamic interactions for multiple particles are included. Simulations based on this mathematical model were performed using open source C++ code. Different initial positions are considered and the system performance is assessed in terms of collection efficiency. The results of this model show closer agreement with the measured in vitro experimental results and with the literature. The implications in nanotechnology and nanomedicine are based on the prediction of the particle efficiency, in conjunction with the magnetizable stent, for targeted drug delivery.

  5. Regular and chaotic dynamics of a chain of magnetic dipoles with moments of inertia

    SciTech Connect

    Shutyi, A. M.

    2009-05-15

    The nonlinear dynamic modes of a chain of coupled spherical bodies having dipole magnetic moments that are excited by a homogeneous ac magnetic field are studied using numerical analysis. Bifurcation diagrams are constructed and used to find conditions for the presence of several types of regular, chaotic, and quasi-periodic oscillations. The effect of the coupling of dipoles on the excited dynamics of the system is revealed. The specific features of the Poincare time sections are considered for the cases of synchronous chaos with antiphase synchronization and asynchronous chaos. The spectrum of Lyapunov exponents is calculated for the dynamic modes of an individual dipole.

  6. Full kinetic simulations of plasma flow interactions with meso- and microscale magnetic dipoles

    SciTech Connect

    Ashida, Y.; Yamakawa, H.; Usui, H.; Miyake, Y.; Shinohara, I.; Funaki, I.; Nakamura, M.

    2014-12-15

    We examined the plasma flow response to meso- and microscale magnetic dipoles by performing three-dimensional full particle-in-cell simulations. We particularly focused on the formation of a magnetosphere and its dependence on the intensity of the magnetic moment. The size of a magnetic dipole immersed in a plasma flow can be characterized by a distance L from the dipole center to the position where the pressure of the local magnetic field becomes equal to the dynamic pressure of the plasma flow under the magnetohydrodynamics (MHD) approximation. In this study, we are interested in a magnetic dipole whose L is smaller than the Larmor radius of ions r{sub iL} calculated with the unperturbed dipole field at the distance L from the center. In the simulation results, we confirmed the clear formation of a magnetosphere consisting of a magnetopause and a tail region in the density profile, although the spatial scale is much smaller than the MHD scale. One of the important findings in this study is that the spatial profiles of the plasma density as well as the current flows are remarkably affected by the finite Larmor radius effect of the plasma flow, which is different from the Earth's magnetosphere. The magnetopause found in the upstream region is located at a position much closer to the dipole center than L. In the equatorial plane, we also found an asymmetric density profile with respect to the plasma flow direction, which is caused by plasma gyration in the dipole field region. The ion current layers are created in the inner region of the dipole field, and the electron current also flows in the region beyond the ion current layer because ions with a large inertia can closely approach the dipole center. Unlike the ring current structure of the Earth's magnetosphere, the current layers in the microscale dipole fields are not circularly closed around the dipole center. Since the major current is caused by the particle gyrations, the current is independently determined

  7. Entangled quantum state of magnetic dipoles.

    PubMed

    Ghosh, S; Rosenbaum, T F; Aeppli, G; Coppersmith, S N

    2003-09-01

    Free magnetic moments usually manifest themselves in Curie laws, where weak external magnetic fields produce magnetizations that vary as the reciprocal of the temperature (1/T). For a variety of materials that do not display static magnetism, including doped semiconductors and certain rare-earth intermetallics, the 1/T law is replaced by a power law T(-alpha) with alpha < 1. Here we show that a much simpler material system-namely, the insulating magnetic salt LiHo(x)Y(1-x)F(4)-can also display such a power law. Moreover, by comparing the results of numerical simulations of this system with susceptibility and specific-heat data, we show that both energy-level splitting and quantum entanglement are crucial to describing its behaviour. The second of these quantum mechanical effects-entanglement, where the wavefunction of a system with several degrees of freedom cannot be written as a product of wavefunctions for each degree of freedom-becomes visible for remarkably small tunnelling terms, and is activated well before tunnelling has visible effects on the spectrum. This finding is significant because it shows that entanglement, rather than energy-level redistribution, can underlie the magnetic behaviour of a simple insulating quantum spin system. PMID:12955135

  8. Matched dipole probe for precise electron density measurements in magnetized and non-magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Rafalskyi, Dmytro; Aanesland, Ane

    2015-09-01

    We present a plasma diagnostics method based on impedance measurements of a short matched dipole placed in the plasma. This allows measuring the local electron density in the range from 1012-1015 m-3 with a magnetic field of at least 0-50 mT. The magnetic field strength is not directly influencing the data analysis and requires only that the dipole probe is oriented perpendicularly to the magnetic field. As a result, the magnetic field can be non-homogeneous or even non-defined within the probe length without any effect on the final tolerance of the measurements. The method can be applied to plasmas of relatively small dimensions (< 10 cm) and doesn't require any special boundary conditions. The high sensitivity of the impedance measurements is achieved by using a miniature matching system installed close to the probe tip, which also allows to suppress sheath resonance effects. We experimentally show here that the tolerance of the electron density measurements reaches values lower than 1%, both with and without the magnetic field. The method is successfully validated by both analytical modeling and experimental comparison with Langmuir probes. The validation experiments are conducted in a low pressure (1 mTorr) Ar discharge sustained in a 10 cm size plasma chamber with and without a transversal magnetic field of about 20 mT. This work was supported by a Marie Curie International Incoming Fellowships within FP7 (NEPTUNE PIIF-GA-2012-326054).

  9. Detailed discussion of a linear electric field frequency shift induced in confined gases by a magnetic field gradient: Implications for neutron electric-dipole-moment experiments

    NASA Astrophysics Data System (ADS)

    Lamoreaux, S. K.; Golub, R.

    2005-03-01

    The search for particle electric dipole moments (EDM’s) is one of the best places to look for physics beyond the standard model of electroweak interaction because the size of time reversal violation predicted by the standard model is incompatible with present ideas concerning the creation of the baryon-antibaryon asymmetry. As the sensitivity of these EDM searches increases more subtle systematic effects become important. We develop a general analytical approach to describe a systematic effect recently observed in an electric dipole moment experiment using stored particles [J. M. Pendlebury , Phys. Rev. A 70, 032102 (2004)]. Our approach is based on the relationship between the systematic frequency shift and the velocity autocorrelation function of the resonating particles. Our results, when applied to well-known limiting forms of the correlation function, are in good agreement with both the limiting cases studied in recent work that employed a numerical and heuristic analysis. Our general approach explains some of the surprising results observed in that work and displays the rich behavior of the shift for intermediate frequencies, which has not been studied previously.

  10. Magnetic levitation for effective loading of cold cesium atoms in a crossed dipole trap

    NASA Astrophysics Data System (ADS)

    Li, Yuqing; Feng, Guosheng; Xu, Rundong; Wang, Xiaofeng; Wu, Jizhou; Chen, Gang; Dai, Xingcan; Ma, Jie; Xiao, Liantuan; Jia, Suotang

    2015-05-01

    We report a detailed study of effective magnetically levitated loading of cold atoms in a crossed dipole trap: an appropriate magnetic field gradient precisely compensates for the destructive gravitational force of the atoms and an additional bias field simultaneously eliminates the antitrapping potential induced by the magnetic field gradient. The magnetic levitation is required for a large-volume crossed dipole trap to form a shallow but very effective loading potential, making it a promising method for loading and trapping more cold atoms. For cold cesium atoms in the F =3 , m F =3 state prepared by three-dimensional degenerated Raman sideband cooling, a large number of atoms ˜3.2 ×106 have been loaded into a large-volume crossed dipole trap with the help of the magnetic levitation technique. The dependence of the number of atoms loaded and trapped in the dipole trap on the magnetic field gradient and bias field, respectively, is in good agreement with the theoretical analysis. The optimum magnetic field gradient of 31.13 G/cm matches the theoretical value of 31.3 G/cm well. This method can be used to obtain more cold atoms or a large number of Bose-Einstein condensation atoms for many atomic species in high-field seeking states.

  11. Comparison of electric dipole and magnetic loop antennas for exciting whistler modes

    NASA Astrophysics Data System (ADS)

    Stenzel, R. L.; Urrutia, J. M.

    2016-08-01

    The excitation of low frequency whistler modes from different antennas has been investigated experimentally in a large laboratory plasma. One antenna consists of a linear electric dipole oriented across the uniform ambient magnetic field B0. The other antenna is an elongated loop with dipole moment parallel to B0. Both antennas are driven by the same rf generator which produces a rf burst well below the electron cyclotron frequency. The antenna currents as well as the wave magnetic fields from each antenna are measured. Both the antenna currents and the wave fields of the loop antenna exceed that of the electric dipole by two orders of magnitude. The conclusion is that loop antennas are far superior to dipole antennas for exciting large amplitude whistler modes, a result important for active wave experiments in space plasmas.

  12. Comparative anatomy of dipole magnets or the magnet designer's coloring book

    SciTech Connect

    Meuser, R.B.

    1983-04-01

    A collection of dipole magnet cross sections is presented together with an indication of how they are related geometrically. The relationships indicated do not necessarily imply the actual path of evolutionary development. Brief consideration is given to magnets of higher multipole order, i.e., quadrupole magnets, etc.). The magnets under consideration have currents parallel to the axis except at the ends, and are long. The relationship between current distribution and magnetic field is essentially two-dimensional. The coils are usually surrounded by an iron yoke, but the emphasis is on conductor-dominated configurations capable of producing a rather uniform magnetic field in the aperture; the iron usually has a small effect.

  13. ANALYTICAL CALCULATION OF STOKES PROFILES OF ROTATING STELLAR MAGNETIC DIPOLE

    SciTech Connect

    Martinez Gonzalez, M. J.

    2012-08-20

    The observation of the polarization emerging from a rotating star at different phases opens up the possibility to map the magnetic field in the stellar surface thanks to the well-known Zeeman-Doppler imaging. When the magnetic field is sufficiently weak, the circular and linear polarization profiles locally in each point of the star are proportional to the first and second derivatives of the unperturbed intensity profile, respectively. We show that the weak-field approximation (for weak lines in the case of linear polarization) can be generalized to the case of a rotating star including the Doppler effect and taking into account the integration on the stellar surface. The Stokes profiles are written as a linear combination of wavelength-dependent terms expressed as series expansions in terms of Hermite polynomials. These terms contain the surface-integrated magnetic field and velocity components. The direct numerical evaluation of these quantities is limited to rotation velocities not larger than eight times the Doppler width of the local absorption profiles. Additionally, we demonstrate that in a rotating star, the circular polarization flux depends on the derivative of the intensity flux with respect to the wavelength and also on the profile itself. Likewise, the linear polarization depends on the profile and on its first and second derivatives with respect to the wavelength. We particularize the general expressions to a rotating dipole.

  14. 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.

  15. Dipole Relaxation in an Electric Field.

    ERIC Educational Resources Information Center

    Neumann, Richard M.

    1980-01-01

    Derives an expression for the orientational entropy of a rigid rod (electric dipole) from Boltzmann's equation. Subsequent application of Newton's second law of motion produces Debye's classical expression for the relaxation of an electric dipole in a viscous medium. (Author/GS)

  16. Second generation superconducting super collider dipole magnet cryostat design

    SciTech Connect

    Niemann, R.C.; Bossert, R.C.; Carson, J.A.; Engler, N.H.; Gonczy, J.D.; Larson, E.T.; Nicol, T.H.; Ohmori, T.

    1988-12-01

    The SSC Magnet Development Program is developing accelerator dipole magnets in successive iterations. The initial iteration is complete with six full length model magnets and a thermal model having been built and tested. This initial experience along with the evolving SSC Magnet System Requirements have resulted in the second generation magnet cryostat design. It is this configuration that will be employed for the near term ongoing magnetic, thermal, string and accelerated life testing and will be the design considered for Phase I; i.e., Technology Orientation, of the SSC Magnet Industrialization Program. 5 refs., 7 figs., 1 tab.

  17. Ramp-rate sensitivity of SSC dipole magnet prototypes

    SciTech Connect

    Devred, A.; Ogitsu, T.

    1994-07-01

    One of the major achievements of the magnet R&D program for the Superconducting Super Collider (SSC) is the fabrication and test of a series of 20 5-cm aperture, 15-m long dipole magnet prototypes. The ramp rate sensitivity of these magnets appears to fall in at least two categories that can be correlated to the manufacturer and production batch of the strands used for the inner-coil cables. The first category, referred to as type-A, is characterized by a strong quench current degradation at high ramp rates, usually accompanied by large distortions of the multipole fields and large energy losses. The second category, referred to as type-B, is characterized by a sudden drop of quench current at low ramp rates, followed by a much milder degradation at larger rates. The multipole fields of the type-B magnets show little ramp-rate sensitivity, and the energy losses are smaller than for the type-A magnets. The behavior of the Type-A magnets can be explained in terms of inter-strand eddy currents arising from low and non-uniform resistances at the crossovers between the strands of the two-layer Rutherford-type cable. Anomalies in the transport-current repartition among the cable strands are suggested as a possible cause for the type-B behavior. The origins of these anomalies have not yet been clearly identified. The SSC project was canceled by decision of the United States Congress on October 21, 1994.

  18. Dipole-exchange modes in transversely magnetized ferromagnetic stripes

    NASA Astrophysics Data System (ADS)

    Arias, Rodrigo; Duan, Zheng; Krivorotov, Ilya

    2014-03-01

    We present a theory of dipole-exchange modes in transversely magnetized ferromagnetic stripes of rectangular cross sections: a comparison is made with experimental results on Permalloy stripes. The model applies to very thin stripes (of the order of the exchange length): the magnetization is considered uniform over their thickness, and we consider modes of long wavelength along the longitudinal direction of the stripes. An applied magnetic field saturates the stripes along the transverse direction, and we also consider the effect of the exchange and dipolar fields. Under these assumptions we obtain the frequencies and shapes of the modes either considering free or pinned boundary conditions. We obtain good agreement with measurements of the frequency spectra in Permalloy nano wires of several rectangular cross sections: this happens for modes with appreciable amplitude throughout the samples. There is frequency disagreement for edge modes due to limitations of the model, since the effects of roughness, corners and imperfections at the edges of the samples are quite relevant in this case. This work was supported by the NSF Materials World Network Program Grant No. DMR-1210850 and by DOE grant DE-FG02-84ER45083. Also, supported by ``Proyecto ICM FP10-061-F-FIC'', and ``Proyecto FONDECYT 1130192, Conicyt, Chile''.

  19. 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.

  20. Diamagnetic repulsion, the method of magnetic images & suitability of the solenoid and dipole models

    NASA Astrophysics Data System (ADS)

    Yin, Ming; Zhang, Huaizhou; Datta, Timir

    2012-02-01

    The repulsion of a permanent magnet from a diamagnetic region was investigated. A magnet of moment m can be described by two models (i) solenoid - a circulating current of appropriate value; second (ii) a magnetic dipole comprising of a pair of north and south poles of separated by a distance.The magnetic field (B) of a permanent magnet was measured. The magnet was modeled as a solenoid with a circulating surface current. The Biot-Savart law field (B) was of computed in Matlab. The experimental data of was in excellent agreement with the Matlab results. However, for computing the repulsion force (F) between the magnet and its diamagnetic image by the direct integration of the current-current interaction require detailed knowledge of the two current densities. However such knowledge is not essential if image is modeled as a dipole. When the magnet is a distance z above the diamagnetic interface then the image current I2 gives rise to a image dipole m2 and the F ˜ m2div B, where the div of the holding field is computed at the distance 2z below the magnet. In this model F is directly proportional to both m' and the derivative of the field and a negative slope indicates repulsion, all three were confirmed.

  1. Design, fabrication and testing of a dipole magnet made with 2G HTS wire

    NASA Astrophysics Data System (ADS)

    Bogdanov, I. V.; Kozub, S. S.; Sytnik, V. V.; Terskiy, I. S.; Tkachenko, L. M.; Trusov, O. V.; Shirshov, L. S.; Smirnov, V. M.; Shuvalov, V. I.; Shcherbakov, P. A.; Molodyk, A. A.; Lee, S. R.; Samoilenkov, S. V.

    2016-10-01

    An HTS dipole magnet with a 1 T (at 77 K) central magnetic field in a 40 × 80 mm2 aperture has been designed, fabricated and tested. The magnet coils were wound with SuperOx 2G HTS wire. The paper describes the magnet design, properties of the magnet materials, and results of calculations and measurements. The central field in the dipole reached 1.12 T at 77 K and 1.66 T at 65 K. In a liquid helium bath the maximum input current of 847 A was limited by the capacity of the power supply, and in that case the central field was 3.03 T. The measurement data were in good agreement with the calculation results.

  2. Electromagnetic braking revisited with a magnetic point dipole model

    NASA Astrophysics Data System (ADS)

    Land, Sara; McGuire, Patrick; Bumb, Nikhil; Mann, Brian P.; Yellen, Benjamin B.

    2016-04-01

    A theoretical model is developed to predict the trajectory of magnetized spheres falling through a copper pipe. The derive magnetic point dipole model agrees well with the experimental trajectories for NdFeB spherical magnets of varying diameter, which are embedded inside 3D printed shells with fixed outer dimensions. This demonstration of electrodynamic phenomena and Lenz's law serves as a good laboratory exercise for physics, electromagnetics, and dynamics classes at the undergraduate level.

  3. Splitting of magnetic dipole modes in anisotropic TiO 2 micro-spheres: Splitting of magnetic dipole modes in anisotropic TiO 2 micro-spheres

    DOE PAGESBeta

    Khromova, Irina; Kužel, Petr; Brener, Igal; Reno, John L.; Chung Seu, U-Chan; Elissalde, Catherine; Maglione, Mario; Mounaix, Patrick; Mitrofanov, Oleg

    2016-06-27

    Monocrystalline titanium dioxide (TiO2) micro-spheres support two orthogonal magnetic dipole modes at terahertz (THz) frequencies due to strong dielectric anisotropy. For the first time, we experimentally detected the splitting of the first Mie mode in spheres of radii inline imagem through near-field time-domain THz spectroscopy. By fitting the Fano lineshape model to the experimentally obtained spectra of the electric field detected by the sub-wavelength aperture probe, we found that the magnetic dipole resonances in TiO2 spheres have narrow linewidths of only tens of gigahertz. Lastly, anisotropic TiO2 micro-resonators can be used to enhance the interplay of magnetic and electric dipolemore » resonances in the emerging THz all-dielectric metamaterial technology.« less

  4. Construction of block-coil high-field model dipoles for future hadron colliders

    SciTech Connect

    Blackburn, Raymond; Elliott, Tim; Henchel, William; McInturff, Al; McIntyre, Peter; Sattarov, Akhdior

    2002-08-04

    A family of high-field dipoles is being developed at Texas A&M University, as part of the program to improve the cost-effectiveness of superconducting magnet technology for future hadron colliders. The TAMU technology employs stress management, flux-plate control of persistent-current multipoles, conductor optimization using mixed-strand cable, and metal-filled bladders to provide pre-load and surface compliance. Construction details and status of the latest model dipole will be presented.

  5. Design and Test of a Nb3Sn Subscale Dipole Magnet for Training Studies

    SciTech Connect

    Felice, Helene; Caspi, Shlomo; Dietderich, Daniel R.; Felice, Helene; Ferracin, Paolo; Gourlay, Steve A.; Hafalia, Aurelo R.; Lietzke, Alan F.; Mailfert, Alain; Sabbi, GainLuca; Vedrine, Pierre

    2007-06-01

    As part of a collaboration between CEA/Saclay and the Superconducting Magnet Group at LBNL, a subscale dipole structure has been developed to study training in Nb3Sn coils under variable pre-stress conditions. This design is derived from the LBNL Subscale Magnet and relies on the use of identical Nb{sub 3}Sn racetrack coils. Whereas the original LBNL subscale magnet was in a dual bore 'common-coil' configuration, the new subscale dipole magnet (SD) is assembled as a single bore dipole made of two superposed racetrack coils. The dipole is supported by a new mechanical structure developed to withstand the horizontal and axial Lorentz forces and capable of applying variable vertical, horizontal and axial preload. The magnet was tested at LBNL as part of a series of training studies aiming at understanding of the relation between pre-stress and magnet performance. Particular attention is given to the coil ends where the magnetic field peaks and stress conditions are the least understood. After a description of SD design, assembly, cool-down and tests results are reported and compared with the computations of the OPERA3D and ANSYS magnetic and mechanical models.

  6. An update on passive correctors for the SSC dipole magnets

    SciTech Connect

    Green, M.A.

    1991-05-01

    The concept of correction of the magnetization sextupole became a topic of discussion as soon as it was realized that superconductor magnetization could have a serious effect on the SSC beam during injection. Several methods of correction were proposed. These included (1) correction with active bore tube windings like those on the HERA machine which correct out magnetization sextupole and the sextupole due to iron saturation, (2) correction with persistent sextupole windings mounted on the bore tube (3) correction using passive superconductor (4) correction using ferromagnetic material, and (5) correction using oriented magnetized materials. This report deals with the use of passive superconductor to correct the magnetization sextupole. Two basic methods are explored in this report: (1) One can correct the magnetization sextupole by changing the diameter of the superconductor filaments in one or more blocks of the SSC dipole. (2) One can correct the magnetization sextupole and decapole by mounting passive superconducting wires on the inside of the SSC dipole coil bore. In addition, an assessment of the contribution of each conductor in the dipole to the magnetization sextupole and decapole is shown. 38 refs, 25 figs., 15 tabs.

  7. Magnetic field measurements in tokamak plasmas

    SciTech Connect

    Feldman, U.; Seely, J.F.; Sheeley,Jr., N.R.; Suckewer, S.; Title, A.M.

    1984-11-01

    The measurement of the poloidal magnetic field in a tokamak plasma from the Zeeman splitting and polarization of the magnetic dipole radiation from heavy ions is discussed. When viewed from a direction perpendicular to the toroidal field, the effect of the poloidal field on the circularly polarized radiation is detectable using a photoelectric polarimeter. The Zeeman splittings for a number of magnetic dipole transitions with wavelengths in the range 2300--9300 A are presented. An imaging polarimeter is proposed that can measure the poloidal magnetic field with space and time resolution.

  8. Dipole pulse theory: Maximizing the field amplitude from 4π focused laser pulses

    NASA Astrophysics Data System (ADS)

    Gonoskov, Ivan; Aiello, Andrea; Heugel, Simon; Leuchs, Gerd

    2012-11-01

    We present a class of exact nonstationary solutions of Maxwell equations in vacuum from dipole pulse theory: electric and magnetic dipole pulses. These solutions can provide for a very efficient focusing of electromagnetic field and can be generated by 4π focusing systems, such as parabolic mirrors, by using radially polarized laser pulses with a suitable amplitude profile. The particular cases of a monochromatic dipole wave and a short dipole pulse with either quasi-Gaussian or Gaussian envelopes in the far-field region are analyzed and compared in detail. As a result, we propose how to increase the maximum field amplitude in the focus by properly shaping the temporal profile of the input laser pulses with given main wavelength and peak power.

  9. MEASUREMENTS OF THE FIELD QUALITY IN SUPERCONDUCTING DIPOLES AT HIGH RAMP RATES.

    SciTech Connect

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

    2006-09-18

    Several recent applications of superconducting magnets require the magnets to be operated at high ramp rates and at frequencies of several Hertz. Brookhaven National Laboratory (BNL) has recently designed and built prototypes of superconducting dipole magnets that can be ramped at a fairly high rate (1 T/s or more). For accelerator applications, it is also crucial that the magnets maintain good field quality even at high ramp rates. In order to characterize the field quality of magnets at high ramp rates, a measurement system consisting of 16 printed circuit tangential coils has been developed. The coil system is held stationary while the magnet is ramped. This paper describes the techniques used for the measurements and data analysis, and presents the results of measurements at ramp rates of up to 4 T/s in a prototype dipole built at BNL for GSI.

  10. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    SciTech Connect

    Córsico, A.H.; Althaus, L.G.; García-Berro, E. E-mail: althaus@fcaglp.unlp.edu.ar E-mail: kepler@if.ufrgs.br

    2014-08-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment (μ{sub ν}) using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. We employ state-of-the-art evolutionary and pulsational codes which allow us to perform a detailed asteroseismological period fit based on fully DB white dwarf evolutionary sequences. Plasmon neutrino emission is the dominant cooling mechanism for this class of hot pulsating white dwarfs, and so it is the main contributor to the rate of change of period with time (Pidot) for the DBV class. Thus, the inclusion of an anomalous neutrino emission through a non-vanishing magnetic dipole moment in these sequences notably influences the evolutionary timescales, and also the expected pulsational properties of the DBV stars. By comparing the theoretical Pidot value with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment with an upper limit of μ{sub ν} ∼< 10{sup -11} μ{sub B}. This bound is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.

  11. Location and depth estimation of point-dipole and line of dipoles using analytic signals of the magnetic gradient tensor and magnitude of vector components

    NASA Astrophysics Data System (ADS)

    Oruç, Bülent

    2010-01-01

    The magnetic gradient tensor (MGT) provides gradient components of potential fields with mathematical properties which allow processing techniques e.g. analytic signal techniques. With MGT emerging as a new tool for geophysical exploration, the mathematical modelling of gradient tensor fields is necessary for interpretation of magnetic field measurements. The point-dipole and line of dipoles are used to approximate various magnetic objects. I investigate the maxima of the magnitude of magnetic vector components (MMVC) and analytic signals of magnetic gradient tensor (ASMGT) resulting from point-dipole and line of dipoles sources in determining horizontal locations. I also present a method in which depths of these sources are estimated from the ratio of the maximum of MMVC to the maximum of ASMGT. Theoretical examples have been carried out to test the feasibility of the method in obtaining source locations and depths. The method has been applied to the MMVC and ASMGT computed from the total field data over a basic/ultrabasic body at the emerald deposit of Socotó, Bahia, Brazil and buried water supply pipe near Jadaguda Township, India. In both field examples, the method produces good correlations with previous interpretations.

  12. 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.

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

    SciTech Connect

    Mauel, M; Ryutov, D; Kesner, J

    2003-12-02

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

  14. Patterned time-orbiting potentials for the confinement and assembly of magnetic dipoles

    PubMed Central

    Chen, A.; Sooryakumar, R.

    2013-01-01

    We present an all-magnetic scheme for the assembly and study of magnetic dipoles within designed confinement profiles that are activated on micro-patterned permalloy films through a precessing magnetic field. Independent control over the confinement and dipolar interactions is achieved by tuning the strength and orientation of the revolving field. The technique is demonstrated with superparamagnetic microspheres field-driven to assemble into closely packed lattice sheets, quasi-1D and other planar structures expandable into dipolar arrays that mirror the patterned surface motifs. PMID:24185093

  15. Tests of a 3 meter curved superconducting beam transport dipole magnet

    SciTech Connect

    Allinger, J E; Carroll, A S; Danby, G T; DeVito, B; Jackson, J W; Leonhardt, W J; Prodell, A G; Weisenbloom, J

    1981-01-01

    Initial tests of one of the curved 3 m long superconducting dipole magnets intended to generate 6.0 T and produce a 20.4/sup 0/ bend in the primary proton beam to a new D-target station at the Brookhaven National Laboratory AGS have been completed. Although this magnet, whose window frame design generally follows that of the successful 8/sup 0/ and Model T superconducting dipoles, demonstrates many of the desirable characteristics of these earlier magnets such as excellent quench propagation and good ramping properties, it has only reached a disappointingly low magnetic field of 3.5 to 4.0 T. Because of the great interest in superconducting magnet technology, this report will describe the diagnostic tests performed and plans for future modifications.

  16. Superconducting super collider second generation dipole magnet cryostat design

    SciTech Connect

    Niemann, R.C.; Bossert, R.C.; Carson, J.A.; Engler, N.H.; Gonczy, J.D.; Larson, E.T.; Nicol, T.H.; Ohmori, T.

    1989-03-01

    The Superconducting Super Collider, a planned colliding beam particle physics research facility, requires --10,000 superconducting devices for the control of high energy particle beams. The --7,500 collider ring superconducting dipole magnets require cryostats that are functional, cryogenically efficient, mass producible and cost effective. A second generation cryostat design has been developed utilizing the experiences gained during the construction, installation and operation of several full length first generation dipole magnet models. The nature of the cryostat improvements is presented. Considered are the connections between the magnet cold mass and its supports, cryogenic supports, cold mass axial anchor, thermal shields, insulation, vacuum vessel and interconnections. The details of the improvements are enumerated and the abstracted results of available component and system evaluations are presented.

  17. Superconducting super collider second generation dipole magnet cryostat design

    SciTech Connect

    Niemann, R.C.; Bossert, R.C.; Carson, J.A.; Engler, N.H.; Gonczy, J.D.; Larson, E.T.; Nicol, T.H.; Ohmori, T.

    1988-12-01

    The Superconducting Super Collider, a planned colliding beam particle physics research facility, requires /approximately/10,000 superconducting devices for the control of high energy particle beams. The /approximately/7,500 collider ring superconducting dipole magnets require cryostats that are functional, cryogenically efficient, mass producible and cost effective. A second generation cryostat design has been developed utilizing the experiences gained during the construction, installation and operation of several full length first generation dipole magnet models. The nature of the cryostat improvements is presented. Considered are the connections between the magnet cold mass and its supports, cryogenic supports, cold mass axial anchor, thermal shields, insulation, vacuum vessel and interconnections. The details of the improvements are enumerated and the abstracted results of available component and system evaluations are presented. 8 refs., 11 figs.

  18. Observation of Centrifugally Driven Interchange Instabilities in a Plasma Confined by a Magnetic Dipole

    SciTech Connect

    Levitt, B.; Maslovsky, D.; Mauel, M.E.

    2005-05-06

    Centrifugally driven interchange instabilities are observed in a laboratory plasma confined by a dipole magnetic field. The instabilities appear when an equatorial mesh is biased to drive a radial current that causes rapid axisymmetric plasma rotation. The observed instabilities are quasicoherent in the laboratory frame of reference; they have global radial mode structures and low azimuthal mode numbers, and they are modified by the presence of energetic, magnetically confined electrons. Results from a self-consistent nonlinear simulation reproduce the measured mode structures.

  19. Nondestructive evaluation using dipole model analysis with a scan type magnetic camera

    NASA Astrophysics Data System (ADS)

    Lee, Jinyi; Hwang, Jiseong

    2005-12-01

    Large structures such as nuclear power, thermal power, chemical and petroleum refining plants are drawing interest with regard to the economic aspect of extending component life in respect to the poor environment created by high pressure, high temperature, and fatigue, securing safety from corrosion and exceeding their designated life span. Therefore, technology that accurately calculates and predicts degradation and defects of aging materials is extremely important. Among different methods available, nondestructive testing using magnetic methods is effective in predicting and evaluating defects on the surface of or surrounding ferromagnetic structures. It is important to estimate the distribution of magnetic field intensity for applicable magnetic methods relating to industrial nondestructive evaluation. A magnetic camera provides distribution of a quantitative magnetic field with a homogeneous lift-off and spatial resolution. It is possible to interpret the distribution of magnetic field when the dipole model was introduced. This study proposed an algorithm for nondestructive evaluation using dipole model analysis with a scan type magnetic camera. The numerical and experimental considerations of the quantitative evaluation of several sizes and shapes of cracks using magnetic field images of the magnetic camera were examined.

  20. Construction techniques for short iron-free dipole magnets

    SciTech Connect

    Harvey, A.R.

    1983-11-08

    A method was developed for economically fabricating short, wire-wound, steering magnets with maximum length, cosine-distributed, axial elements. This method utilizes multifunctional tooling to precisely flat-wind two-layer dipole halves that are subsequently reformed and encapsulated into semicylindrical form with confinement of the end turns into thin, half discs normal to the magnet axis. This paper addresses the magnet fabrication in detail, highlighting the inherent quality control features of the tooling, overall construction costs, and contemplated manufacturing enhancements.

  1. Full length SSC R and D dipole magnet test results

    SciTech Connect

    Strait, J.; Bleadon, M.; Brown, B.C.; Hanft, R.; Kuchnir, M.; Lamm, M.; Mantsch, P.; Mazur, P.O.; Orris, D.; Peoples, J.

    1989-03-01

    Four full scale SSC development dipole magnets have been tested for mechanical and quench behavior. Two are of a design similar to previous magnets but contain a number of improvements, including more uniform coil size, higher pre-stress and a redesigned inner-outer coil splice. One exceeds the SSC operating current on the second quench but the other appears to be limited by damaged superconductor to a lower current. The other two magnets are of alternate designs. One trains erratically and fails to reach a plateau and the other reaches plateau after four quenches. 12 refs., 4 figs.

  2. Performance of dipole magnets in helium II

    SciTech Connect

    Althaus, R.; Caspi, S.; Gilbert, W.S.; Hassenzahl, W.; Meuser, R.; Rechen, J.; Taylor, C.; Warren, R.

    1981-03-01

    Data from tests in He II of four 1-meter-long magnets are presented. The maximum quench current is increased up to 30 percent, compared with tests in He I. Data from calorimetric measurements of heat generated during cyclic operation are presented. Quenches were induced by heaters placed near the conductor, and the energy required to induce quenches in He II and in He I are compared.

  3. Modeling Barkhausen Noise in magnetic glasses with dipole-dipole interactions

    NASA Astrophysics Data System (ADS)

    Dubey, Awadhesh K.; Hentschel, H. George E.; Jaiswal, Prabhat K.; Mondal, Chandana; Procaccia, Itamar; Gupta, Bhaskar Sen

    2015-10-01

    Long-ranged dipole-dipole interactions in magnetic glasses give rise to magnetic domains having labyrinthine patterns on the scale of about 1 micron. Barkhausen Noise then results from the movement of domain boundaries which is modeled by the motion of elastic membranes with random pinning. Here we propose that on the nanoscale new sources of Barkhausen Noise can arise. We propose an atomistic model of magnetic glasses in which we measure the Barkhausen Noise which results from the creation of new domains and the movement of domain boundaries on the nanoscale. The statistics of the Barkhausen Noise found in our simulations is in striking disagreement with the expectations in the literature. In fact we find exponential statistics without any power law, stressing the fact that Barkhausen Noise can belong to very different universality classes. In the present model the essence of the phenomenon is the fact that the spin response Green's function is decaying too rapidly for having sufficiently large magnetic jumps. A theory is offered in excellent agreement with the measured data without any free parameter.

  4. Driven assembly with multiaxial fields: Creating a soft mode in assemblies of anisometric induced dipoles

    DOE PAGESBeta

    Martin, James E.; Swol, Frank Van

    2015-07-10

    We show that multiaxial fields can induce time-averaged, noncentrosymmetric interactions between particles having polarization anisotropy, yet the multiaxial field itself does not exert either a force or a torque on an isolated particle. These induced interactions lead to particle assemblies whose energy is strongly dependent on both the translational and orientational degrees of freedom of the system. The situation is similar to a collection of permanent dipoles, but the symmetry of the time-averaged interaction is quite distinct, and the scale of the system energy can be dynamically controlled by the magnitude of the applied multiaxial field. In our paper, themore » case of polarizable rods is considered in detail, and it is suggested that collections of rods embedded in spheres can be used to create a material with a dynamically tunable magnetic permeability or dielectric permittivity. We report on Monte Carlo simulations performed to investigate the behavior of assemblies of both multiaxial-field induced dipoles and permanent dipoles arranged onto two-dimensional lattices. Lastly, the ground state of the induced dipoles is an orientational soft mode of aligned dipoles, whereas that of the permanent dipoles is a vortex state.« less

  5. Energy transport in the near field of an electric dipole near a layer of material

    NASA Astrophysics Data System (ADS)

    Arnoldus, Henk F.; Berg, Matthew J.

    2015-02-01

    We consider an oscillating electric dipole, embedded in a uniform medium with relative permittivity ? and relative permeability ?. The dipole is located near an interface with a layer with uniform material parameters ? and ?, and the second interface borders a uniform medium with parameters ? and ?. We have obtained the solutions for the electric and magnetic fields in the various regions, without any restrictions on the parameters and for any state of oscillation of the dipole (elliptical, in general). The solution involves a set of auxiliary functions, which are given as integral representations containing the Fresnel coefficients for plane waves. With this solution, the field lines of energy flow can be obtained, and we have considered the flow pattern for the simple case of a dipole oscillating perpendicular to the interface. When the material of the layer is optically thicker than the embedding medium of the dipole, energy flows more or less along straight lines. At an interface, the field lines refract, similar to optical rays. When the layer material is optically thinner, the energy flow lines curve. A portion of the energy that propagates toward the interface bends away from it before reaching the interface. Other field lines of energy flow cross the interface, but then return to the area of the dipole by crossing the interface again. This leads to an oscillation of energy back and forth through the interface. In the neighborhood of this oscillation, a concentric set of vortex tori appears.

  6. Driven assembly with multiaxial fields: Creating a soft mode in assemblies of anisometric induced dipoles

    SciTech Connect

    Martin, James E.; Swol, Frank Van

    2015-07-10

    We show that multiaxial fields can induce time-averaged, noncentrosymmetric interactions between particles having polarization anisotropy, yet the multiaxial field itself does not exert either a force or a torque on an isolated particle. These induced interactions lead to particle assemblies whose energy is strongly dependent on both the translational and orientational degrees of freedom of the system. The situation is similar to a collection of permanent dipoles, but the symmetry of the time-averaged interaction is quite distinct, and the scale of the system energy can be dynamically controlled by the magnitude of the applied multiaxial field. In our paper, the case of polarizable rods is considered in detail, and it is suggested that collections of rods embedded in spheres can be used to create a material with a dynamically tunable magnetic permeability or dielectric permittivity. We report on Monte Carlo simulations performed to investigate the behavior of assemblies of both multiaxial-field induced dipoles and permanent dipoles arranged onto two-dimensional lattices. Lastly, the ground state of the induced dipoles is an orientational soft mode of aligned dipoles, whereas that of the permanent dipoles is a vortex state.

  7. The Fermilab main injector dipole construction techniques and prototype magnet measurements

    SciTech Connect

    Bleadon, M.; Brown, B.; Chester, N.; Desavouret, E.; Garvey, J.; Glass, H.; Harding, D.; Harfoush, F.; Holmes, S.; Humbert, J.; Kerby, J.; Knauf, A.; Kobliska, G.; Lipski, A.; Martin, P.; Mazur, P.; Orris, D.; Ostiguy, J.; Peggs, S.; Pachnik, J.; Pewitt, E.; Satti, J.; Schmidt, E.; Sim, J.; Snowdon, S.; Walbridge, D.

    1991-09-01

    The Fermilab Main Injector Project will provide 120--150 GeV Proton and Antiproton Beams for Fermilab Fixed Target Physics and Colliding Beams Physics use. A dipole magnet has been designed and prototypes constructed for the principal bending magnets of this new accelerator. The design considerations and fabrication techniques are described. Measurement results on prototypes are reported, emphasizing the field uniformity achieved in both body field and end field at excitation levels from injection at 0.1 T to full field of 1.7 T. 6 refs., 5 figs., 3 tabs.

  8. Matched dipole probe for magnetized low electron density laboratory plasma diagnostics

    SciTech Connect

    Rafalskyi, Dmytro; Aanesland, Ane

    2015-07-15

    In this paper, a diagnostic method for magnetized and unmagnetized laboratory plasma is proposed, based on impedance measurements of a short matched dipole. The range of the measured electron densities is limited to low density plasmas (10{sup 12}–10{sup 15 }m{sup −3}), where other diagnostic methods have strong limitations on the magnetic field strength and topology, plasma dimensions, and boundary conditions. The method is designed for use in both large- and small-dimension plasma (<10 cm) without or with strong non-homogeneous magnetic field, which can be undefined within the probe size. The design of a matched dipole probe allows to suppress the sheath resonance effects and to reach high sensitivity at relatively small probe dimensions. Validation experiments are conducted in both magnetized (B ∼ 170 G) and unmagnetized (B = 0) low density (7 × 10{sup 12 }m{sup −3}–7 × 10{sup 13 }m{sup −3}) low pressure (1 mTorr) 10 cm scale plasmas. The experimentally measured data show very good agreement with an analytical theory both for a non-magnetized and a magnetized case. The electron density measured by the matched dipole and Langmuir probes in the range of 7 × 10{sup 12 }m{sup −3}–7 × 10{sup 13 }m{sup −3} show less than 30% difference. An experimentally measured tolerance/uncertainty of the dipole probe method is estimated to ±1% for plasma densities above 2 × 10{sup 13 }m{sup −3}. A spatial resolution is estimated from the experiments to be about 3d, where d is the dipole diameter. The diagnostic method is also validated by comparing the measured plasma impedance curves with results of analytical modelling.

  9. Matched dipole probe for magnetized low electron density laboratory plasma diagnostics

    NASA Astrophysics Data System (ADS)

    Rafalskyi, Dmytro; Aanesland, Ane

    2015-07-01

    In this paper, a diagnostic method for magnetized and unmagnetized laboratory plasma is proposed, based on impedance measurements of a short matched dipole. The range of the measured electron densities is limited to low density plasmas (1012-1015 m-3), where other diagnostic methods have strong limitations on the magnetic field strength and topology, plasma dimensions, and boundary conditions. The method is designed for use in both large- and small-dimension plasma (<10 cm) without or with strong non-homogeneous magnetic field, which can be undefined within the probe size. The design of a matched dipole probe allows to suppress the sheath resonance effects and to reach high sensitivity at relatively small probe dimensions. Validation experiments are conducted in both magnetized (B ˜ 170 G) and unmagnetized (B = 0) low density (7 × 1012 m-3-7 × 1013 m-3) low pressure (1 mTorr) 10 cm scale plasmas. The experimentally measured data show very good agreement with an analytical theory both for a non-magnetized and a magnetized case. The electron density measured by the matched dipole and Langmuir probes in the range of 7 × 1012 m-3-7 × 1013 m-3 show less than 30% difference. An experimentally measured tolerance/uncertainty of the dipole probe method is estimated to ±1% for plasma densities above 2 × 1013 m-3. A spatial resolution is estimated from the experiments to be about 3d, where d is the dipole diameter. The diagnostic method is also validated by comparing the measured plasma impedance curves with results of analytical modelling.

  10. Electron electric-dipole-moment experiment using electric-field quantized slow cesium atoms

    SciTech Connect

    Amini, Jason M.; Munger, Charles T. Jr.; Gould, Harvey

    2007-06-15

    A proof-of-principle electron electric-dipole-moment (e-EDM) experiment using slow cesium atoms, nulled magnetic fields, and electric-field quantization has been performed. With the ambient magnetic fields seen by the atoms reduced to less than 200 pT, an electric field of 6 MV/m lifts the degeneracy between states of unequal |m{sub F}| and, along with the low ({approx_equal}3 m/s) velocity, suppresses the systematic effect from the motional magnetic field. The low velocity and small residual magnetic field have made it possible to induce transitions between states and to perform state preparation, analysis, and detection in regions free of applied static magnetic and electric fields. This experiment demonstrates techniques that may be used to improve the e-EDM limit by two orders of magnitude, but it is not in itself a sensitive e-EDM search, mostly due to limitations of the laser system.

  11. Quench calculations for the superconducting dipole magnet of CBM experiment at FAIR

    NASA Astrophysics Data System (ADS)

    Kurilkin, P.; Akishin, P.; Bychkov, A.; Floch, E.; Gusakov, Yu.; Ladygin, V.; Malakhov, A.; Moritz, G.; Ramakers, H.; Senger, P.; Shabunov, A.; Szwangruber, P.; Toral, F.

    2016-08-01

    The scientific mission of the Compressed Baryonic Matter (CBM) experiment is the study of the nuclear matter properties at the high baryon densities in heavy ion collisions at the Facility of Antiproton and Ion Research (FAIR) in Darmstadt. The 5.15 MJ superconducting dipole magnet will be used in the silicon tracking system of the CBM detector. It will provide a magnetic field integral of 1 Tm which is required to obtain a momentum resolution of 1% for the track reconstruction. This paper presents quench modeling and evaluation of candidate protection schemes for the CBM dipole magnet. Two quench programs based on finite-difference method were used in simulation. One of them is currently used at GSI, and the other based on CIEMAT (Madrid, Spain) was modified to perform quench calculation for the CBM magnet.

  12. SSC dipole magnet measurement and alignment using laser technology

    SciTech Connect

    Lipski, A.; Carson, J.A.; Robotham, W.F.

    1990-06-01

    Advancing into the prototype production stage of the SSC dipole magnets has introduced the need for a reliable, readily available, accurate alignment measuring system which gives results in real time. Components and subassemblies such as the cold mass and vacuum vessel are being measured for various geometric conditions such as straightness and twist. Variations from nominal dimensions are also being recorded so they can be compensated for during the final assembly process. Precision laser alignment takes specific advantages of the greatest accuracy. When combined with an optically produced perpendicular plane, this results in a system of geometric references of unparalleled accuracy. This paper describes the geometric requirements for SSC dipole magnet components, sub and final assemblies as well as the use of laser technology for surveying as part of the assembly process.

  13. Dipole corrector magnets for the LBNE beam line

    SciTech Connect

    Yu, M.; Velev, G.; Harding, D.; /Fermilab

    2011-03-01

    The conceptual design of a new dipole corrector magnet has been thoroughly studied. The planned Long-Baseline Neutrino Experiment (LBNE) beam line will require correctors capable of greater range and linearity than existing correctors, so a new design is proposed based on the horizontal trim dipole correctors built for the Main Injector synchrotron at Fermilab. The gap, pole shape, length, and number of conductor turns remain the same. To allow operation over a wider range of excitations without overheating, the conductor size is increased, and to maintain better linearity, the back leg thickness is increased. The magnetic simulation was done using ANSYS to optimize the shape and the size of the yoke. The thermal performance was also modeled and analyzed.

  14. A theoretical analysis of the observed variability of the geomagnetic dipole field

    NASA Astrophysics Data System (ADS)

    Hoyng, P.; Schmitt, D.; Ossendrijver, M. A. J. H.

    2002-04-01

    We present a detailed analysis of the Sint-800 virtual axial dipole moment (VADM) data in terms of an αΩ mean field model of the geodynamo that features a non-steady generation of poloidal from toroidal magnetic field. The result is a variable excitation of the dipole mode and the overtones, and there are occasional dipole reversals. The model permits a theoretical evaluation of the statistical properties of the dipole mode. We show that the model correctly predicts the distribution of the VADM and the autocorrelation function inferred from the Sint-800 data. The autocorrelation technique allows us to determine the turbulent diffusion time τd= R2/ β of the geodynamo. We find that τd is about 10-15 kyr. The model is able to reproduce the observed secular variation of the dipole mode, and the mean time between successive dipole reversals. On the other hand, the duration of a reversal is a factor ˜2 too long. This could be due to imperfections in the model or to unknown systematics in the Sint-800 data. The use of mean field theory is shown to be selfconsistent.

  15. Magnetic dipole excitations of the 163Dy nucleus

    NASA Astrophysics Data System (ADS)

    Zenginerler, Zemine; Tabar, Emre; Yakut, Hakan; Kuliev, Ali Akbar; Guliyev, Ekber

    2014-03-01

    In this study some properties of the magnetic dipole excitations of the deformed odd mass 163Dy nucleus were studied by using Quasiparticle-phonon nuclear model (QPNM). The several of the ground-state and low-lying magnetic dipole (M1) mode characteristics were calculated for deformed odd-mass nuclei using a separable Hamiltonian within the QPNM. The M1 excited states, reduced transition probabilities B(M1), the ground-state magnetic properties such as magnetic moment (μ), intrinsic magnetic moment (gK) , effective spin factor (gseff.) are the fundamental characteristics of the odd-mass nucleus and provide key information to understand nuclear structure. The theoretical results were compared with the available experimental data and other theoretical approaches. Calculations show that the spin-spin interaction in this isotopes leads to polarization effect influencing the magnetic moments. Furthermore we found a strong fragmentation of the M1 strength in 163Dy nucleus which was in qualitative agreement with the experimental data. Sakarya University, Project Number: 2012-50-02-007 and Z.Zenginerler acknowledge to TUBITAK-TURKEY 2013, fellowship No: 2219.

  16. Field quality issues in iron-dominated dipoles at low fields

    SciTech Connect

    Brown, B.C.

    1996-10-01

    In order to help assess the usable dynamic range of iron-dominated dipoles, field shape data at low field on several Fermi-lab accelerator dipole designs are presented. Emphasis is placed on the systematic and random values of the low field sextupole since it is the first ``allowed`` field error. The Main Injector dipoles provide four times smaller sextupole and more than 20 times less sextupole hysteresis than earlier designs for the Main Ring.

  17. Magnetic dipole sequences in {sup 83}Rb

    SciTech Connect

    Schwengner, R.; Schnare, H.; Wagner, A.; Doenau, F.; Rainovski, G.; Frauendorf, S.; Jungclaus, A.; Hausmann, M.; Lieb, K. P.; Yordanov, O.; Napoli, D. R.; De Angelis, G.; Axiotis, M.; Marginean, N.; Brandolini, F.; Alvarez, C. Rossi

    2009-10-15

    High-spin states in {sup 83}Rb were populated in the reaction {sup 11}B+{sup 76}Ge at beam energies of 45 and 50 MeV. {gamma} rays were detected with the spectrometer GASP. The level scheme of {sup 83}Rb was extended up to 13.9 MeV. Mean lifetimes of 23 levels were determined using the Doppler-shift-attenuation method. Among the bands newly established is a sequence comprising intense M1 transitions and crossover E2 transitions. This sequence turns out to be irregular and thus shows that magnetic rotation as observed in the neighboring odd-odd isotopes is not realized in this odd-even nuclide. Excited states in {sup 83}Rb were interpreted in terms of the shell model using the model space {pi}(0f{sub 5/2},1p{sub 3/2},1p{sub 1/2},0g{sub 9/2}) {nu}(1p{sub 1/2},0g{sub 9/2}). The configurations predicted for the negative-parity M1 sequence reproduce the M1 transition strengths fairly well.

  18. General magnetic transition dipole moments for electron paramagnetic resonance.

    PubMed

    Nehrkorn, Joscha; Schnegg, Alexander; Holldack, Karsten; Stoll, Stefan

    2015-01-01

    We present general expressions for the magnetic transition rates in electron paramagnetic resonance (EPR) experiments of anisotropic spin systems in the solid state. The expressions apply to general spin centers and arbitrary excitation geometry (Voigt, Faraday, and intermediate). They work for linear and circular polarized as well as unpolarized excitation, and for crystals and powders. The expressions are based on the concept of the (complex) magnetic transition dipole moment vector. Using the new theory, we determine the parities of ground and excited spin states of high-spin (S=5/2) Fe(III) in hemin from the polarization dependence of experimental EPR line intensities.

  19. MAGNETIC FIELD MEASUREMENTS FOR FAST-CHANGING MAGNETIC FIELDS.

    SciTech Connect

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

    2004-10-03

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

  20. Preliminary analysis of coil wedge dimensional variation in SSC Prototype Dipole Magnets

    SciTech Connect

    Pollock, D.; Brown, G.; Dwyer, S.; Gattu, R.; Warner, D.

    1993-05-01

    The wedges used in SSC Prototype Dipole Magnets determine the relative position of conductor blocks within magnet coils. They serve to compensate partially for the less than full keystoning of the superconductor cable and to adjust current distribution with azimuth to determine the magnetic field shape. The ability to control the size and uniformity of wedges therefore is an important factor influencing magnet quality. This paper presents preliminary results of a Statistical Quality Control study of wedge dimensional variation and predicted field quality. Dimensions of samples from outer wedges for magnet DCA102 have been measured using a programmable optical comparator. The data is used to evaluate wedge manufacturing process capability, wedge uniformity, and to predict changes in conductor block position due to wedge deviation. Expected multipole variation attributable to observed wedge variation is discussed. This work focuses on a Prototype Dipole Magnet being built at the SSCL Magnet Development Laboratory (SSCL MDL) in Waxahachie, Texas. The magnet is of the same design as the DCA3xx series magnets built at Fermi National Accelerator Laboratory (FNAL) in 1991--92 and later used in the 1992 Accelerator Systems String Test (ASST).

  1. Dynamics of dipoles and vortices in nonlinearly coupled three-dimensional field oscillators.

    PubMed

    Driben, R; Konotop, V V; Malomed, B A; Meier, T

    2016-07-01

    The dynamics of a pair of harmonic oscillators represented by three-dimensional fields coupled with a repulsive cubic nonlinearity is investigated through direct simulations of the respective field equations and with the help of the finite-mode Galerkin approximation (GA), which represents the two interacting fields by a superposition of 3+3 harmonic-oscillator p-wave eigenfunctions with orbital and magnetic quantum numbers l=1 and m=1, 0, -1. The system can be implemented in binary Bose-Einstein condensates, demonstrating the potential of the atomic condensates to emulate various complex modes predicted by classical field theories. First, the GA very accurately predicts a broadly degenerate set of the system's ground states in the p-wave manifold, in the form of complexes built of a dipole coaxial with another dipole or vortex, as well as complexes built of mutually orthogonal dipoles. Next, pairs of noncoaxial vortices and/or dipoles, including pairs of mutually perpendicular vortices, develop remarkably stable dynamical regimes, which feature periodic exchange of the angular momentum and periodic switching between dipoles and vortices. For a moderately strong nonlinearity, simulations of the coupled-field equations agree very well with results produced by the GA, demonstrating that the dynamics is accurately spanned by the set of six modes limited to l=1. PMID:27575123

  2. Dynamics of dipoles and vortices in nonlinearly coupled three-dimensional field oscillators

    NASA Astrophysics Data System (ADS)

    Driben, R.; Konotop, V. V.; Malomed, B. A.; Meier, T.

    2016-07-01

    The dynamics of a pair of harmonic oscillators represented by three-dimensional fields coupled with a repulsive cubic nonlinearity is investigated through direct simulations of the respective field equations and with the help of the finite-mode Galerkin approximation (GA), which represents the two interacting fields by a superposition of 3 +3 harmonic-oscillator p -wave eigenfunctions with orbital and magnetic quantum numbers l =1 and m =1 , 0, -1 . The system can be implemented in binary Bose-Einstein condensates, demonstrating the potential of the atomic condensates to emulate various complex modes predicted by classical field theories. First, the GA very accurately predicts a broadly degenerate set of the system's ground states in the p -wave manifold, in the form of complexes built of a dipole coaxial with another dipole or vortex, as well as complexes built of mutually orthogonal dipoles. Next, pairs of noncoaxial vortices and/or dipoles, including pairs of mutually perpendicular vortices, develop remarkably stable dynamical regimes, which feature periodic exchange of the angular momentum and periodic switching between dipoles and vortices. For a moderately strong nonlinearity, simulations of the coupled-field equations agree very well with results produced by the GA, demonstrating that the dynamics is accurately spanned by the set of six modes limited to l =1 .

  3. Dynamics of dipoles and vortices in nonlinearly coupled three-dimensional field oscillators.

    PubMed

    Driben, R; Konotop, V V; Malomed, B A; Meier, T

    2016-07-01

    The dynamics of a pair of harmonic oscillators represented by three-dimensional fields coupled with a repulsive cubic nonlinearity is investigated through direct simulations of the respective field equations and with the help of the finite-mode Galerkin approximation (GA), which represents the two interacting fields by a superposition of 3+3 harmonic-oscillator p-wave eigenfunctions with orbital and magnetic quantum numbers l=1 and m=1, 0, -1. The system can be implemented in binary Bose-Einstein condensates, demonstrating the potential of the atomic condensates to emulate various complex modes predicted by classical field theories. First, the GA very accurately predicts a broadly degenerate set of the system's ground states in the p-wave manifold, in the form of complexes built of a dipole coaxial with another dipole or vortex, as well as complexes built of mutually orthogonal dipoles. Next, pairs of noncoaxial vortices and/or dipoles, including pairs of mutually perpendicular vortices, develop remarkably stable dynamical regimes, which feature periodic exchange of the angular momentum and periodic switching between dipoles and vortices. For a moderately strong nonlinearity, simulations of the coupled-field equations agree very well with results produced by the GA, demonstrating that the dynamics is accurately spanned by the set of six modes limited to l=1.

  4. Influence of the dipole interaction on the direction of the magnetization in thin ferromagnetic films

    NASA Astrophysics Data System (ADS)

    Moschel, A.; Usadel, K. D.

    1994-11-01

    The magnetization of thin films depends in a very sensitive way on surface anisotropy fields which often favor a perpendicular orientation and on the dipole interaction which favors an in-plane magnetization. A temperature driven transition from one to the other orientation has been observed experimentally. In order to understand this behavior theoretically we performed detailed calculations of the magnetization of very thin films (thickness of up to 5 layers) within a quantum mechanical mean field approach. A surface anisotropy that favors a perpendicular orientation and a long range dipole interaction were taken into account. It is shown that these competing interactions for certain values of the parameters may result in a temperature driven switching transition from an out-of plane to an in-plane ordered state. Varying the strength of the dipole interaction we found that the switching temperature is a very sensitive function of the ratio of these two competing interactions. A perpendicular ground state magnetization of the firm is only found for values of the surface anisotropy which are larger than a critical surface anisotropy value. The reorientation of the magnetization vector has its physical origin in an entropy increase of the system when going from a perpendicular to an in-plan ordered state.

  5. On the electrodynamics of moving permanent dipoles in external electromagnetic fields

    NASA Astrophysics Data System (ADS)

    Mansuripur, Masud

    2014-09-01

    The classical theory of electrodynamics is built upon Maxwell's equations and the concepts of electromagnetic field, force, energy and momentum, which are intimately tied together by Poynting's theorem and the Lorentz force law. Whereas Maxwell's macroscopic equations relate the electric and magnetic fields to their material sources (i.e., charge, current, polarization and magnetization), Poynting's theorem governs the flow of electromagnetic energy and its exchange between fields and material media, while the Lorentz law regulates the back-and-forth transfer of momentum between the media and the fields. The close association of momentum with energy thus demands that the Poynting theorem and the Lorentz law remain consistent with each other, while, at the same time, ensuring compliance with the conservation laws of energy, linear momentum, and angular momentum. This paper shows how a consistent application of the aforementioned laws of electrodynamics to moving permanent dipoles (both electric and magnetic) brings into play the rest-mass of the dipoles. The rest mass must vary in response to external electromagnetic fields if the overall energy of the system is to be conserved. The physical basis for the inferred variations of the rest-mass appears to be an interference between the internal fields of the dipoles and the externally applied fields. We use two different formulations of the classical theory in which energy and momentum relate differently to the fields, yet we find identical behavior for the restmass in both formulations.

  6. Long-term dipole-dipole resistivity monitoring at the Cerro Prieto geothermal field

    SciTech Connect

    Wilt, M.; Goldstein, N.E.; Sasaki, Y.

    1984-04-01

    Dipole-dipole resistivity measurements for the combined purposes of reservoir delineation and reservoir monitoring were first made at Cerro Prieto in 1978 and have continued on approximately an annual basis since then. Two 20 km-long dipole-dipole lines with permanently emplaced electrodes at 1-km spacings were established over the field area. Resistivity remeasurements have been made on one line at 6- to 18-month intervals using a 25 kW generator capable of up to 80A output and a microprocessor-controlled signal-averaging receiver. This high-power, low-noise system provides highly accurate measurements even at large transmitter receiver separations. Standard error calculations for collected data indicate errors less than 5% for all points. Results from four years of monitoring (1979-1983) indicate a 5% average annual increase in apparent resistivity over the present production area, and larger decreases in apparent resistivity in the region to the east. The increase in resistivity in the production zone is most likely due to dilution of reservoir fluids with fresher water, as evidenced by a drop in chloride content of produced waters. The area of decreasing resistivity east of the reservoir is associated with a steeply dipping conductive body, a zone of higher thermal gradients and an increase in shale thickness in the section. Decreasing resistivity in this area may be caused by an influx of high temperature, saline water from depths of 3/sup +/ km through a sandy gap in the shales.

  7. Rotating dipole and quadrupole field for a multiple cathode system

    SciTech Connect

    Chang, X.; Ben-Zvi, I.; Kewisch, J.; Litvinenko, V.; Meng, W.; Pikin, A.; Ptitsyn, V.; Rao, T.; Sheehy, B.; Skarita, J.; Wang, E.; Wu, Q.; Xin, T.

    2011-03-28

    A multiple cathode system has been designed to provide the high average current polarized electron bunches for the future electron-ion collider eRHIC [1]. One of the key research topics in this design is the technique to generate a combined dipole and quadrupole rotating field at high frequency (700 kHz). This type of field is necessary for combining bunches from different cathodes to the same axis with minimum emittance growth. Our simulations and the prototype test results to achieve this will be presented. The future eRHIC project, next upgrade of EHIC, will be the first electron-heavy ion collider in the world. For polarized-electron and polarized proton collisions, it requires a polarized electron source with high average current ({approx}50 mA), short bunch ({approx}3 mm), emittance of about 20 {micro}m and energy spread of {approx}1% at 10 MeV. The state-of-art polarized electron cathode can generate average current of about more than 1 mA, but much less than 50 mA. The current is limited by the quantum efficiency, lifetime, space charge and ultra-high vacuum requirement of the polarized cathode. A possible approach to achieve the 50 mA beam is to employ multiple cathodes, such as 20 cathodes, and combine the multiple bunched beams from cathodes to the same axis. We name it as 'Gatling gun' because its operations bear similarity to a multi-barrel Gatling gun. The electron spin direction is not affected by electric field but will follow to the direction of the magnetic bending. This requires that, to preserve the spin polarization from cathode, the fixed bending field after the solenoid and the rotating bending field in combiner must be either a pair of electric bendings or a pair of magnetic bendings. We choose the scheme with a pair of magnetic bendings because it is much easier than the scheme with a pair of electric bendings at our 200 keV electron energy level.

  8. Time-reversal symmetry breaking and spontaneous Hall effect without magnetic dipole order.

    PubMed

    Machida, Yo; Nakatsuji, Satoru; Onoda, Shigeki; Tayama, Takashi; Sakakibara, Toshiro

    2010-01-14

    Spin liquids are magnetically frustrated systems, in which spins are prevented from ordering or freezing, owing to quantum or thermal fluctuations among degenerate states induced by the frustration. Chiral spin liquids are a hypothetical class of spin liquids in which the time-reversal symmetry is macroscopically broken in the absence of an applied magnetic field or any magnetic dipole long-range order. Even though such chiral spin-liquid states were proposed more than two decades ago, an experimental realization and observation of such states has remained a challenge. One of the characteristic order parameters in such systems is a macroscopic average of the scalar spin chirality, a solid angle subtended by three nearby spins. In previous experimental reports, however, the spin chirality was only parasitic to the non-coplanar spin structure associated with a magnetic dipole long-range order or induced by the applied magnetic field, and thus the chiral spin-liquid state has never been found. Here, we report empirical evidence that the time-reversal symmetry can be broken spontaneously on a macroscopic scale in the absence of magnetic dipole long-range order. In particular, we employ the anomalous Hall effect to directly probe the broken time-reversal symmetry for the metallic frustrated magnet Pr(2)Ir(2)O(7). An onset of the Hall effect is observed at zero field in the absence of uniform magnetization, within the experimental accuracy, suggesting an emergence of a chiral spin liquid. The origin of this spontaneous Hall effect is ascribed to chiral spin textures, which are inferred from the magnetic measurements indicating the spin ice-rule formation. PMID:20010605

  9. Space propulsion by fusion in a magnetic dipole

    SciTech Connect

    Teller, E.; Glass, A.J.; Fowler, T.K. ); Hasegawa, A. ); Santarius, J.F. . Fusion Technology Inst.)

    1991-07-15

    The unique advantages of fusion rocket propulsion systems for distant missions are explored using the magnetic dipole configurations as an example. The dipole is found to have features well suited to space applications. Parameters are presented for a system producing a specific power of kW/kg, capable of interplanetary flights to Mars in 90 days and to Jupiter in a year, and of extra-solar-system flights to 1000 astronomical units (the Tau mission) in 20 years. This is about 10 times better specific power performance than nuclear electric fission systems. Possibilities to further increase the specific power toward 10 kW/kg are discussed, as is an approach to implementing the concept through proof-testing on the moon. 20 refs., 14 figs., 2 tabs.

  10. Space propulsion by fusion in a magnetic dipole

    SciTech Connect

    Teller, E.; Glass, A.J.; Fowler, T.K. ); Hasegawa, A. ); Santarius, J.F. . Fusion Technology Inst.)

    1991-04-12

    A conceptual design is discussed for a fusion rocket propulsion system based on the magnetic dipole configuration. The dipole is found to have features well suited to space applications. Example parameters are presented for a system producing a specific power of 1 kW/kg, capable of interplanetary flights to Mars in 90 days and to Jupiter in a year, and of extra-solar-system flights to 1000 astronomical units (the Tau mission) in 20 years. This is about 10 times better specific power toward 10 kW/kg are discussed, as in an approach to implementing the concept through proof-testing on the moon. 21 refs., 14 figs., 2 tabs.

  11. Coronal magnetic fields produced by photospheric shear

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  12. Dynamic dipoles

    NASA Astrophysics Data System (ADS)

    Griffiths, David J.

    2011-08-01

    We study stationary but time-dependent ideal (point) electric and magnetic dipoles, both the conventional type consisting of electric charges and currents and the hypothetical kind composed of magnetic monopoles and their currents. We derive their potentials and fields, and calculate the energy, momentum, and angular momentum they radiate.

  13. Magnetic field structure of Mercury

    NASA Astrophysics Data System (ADS)

    Hiremath, K. M.

    2012-04-01

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

  14. Dual AC Dipole Excitation for the Measurement of Magnetic Multipole Strength from Beam Position Monitor Data

    SciTech Connect

    M. Spata, G.A. Krafft

    2011-09-01

    An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a technique for characterizing the nonlinear fields of the beam transport system. Two air-core dipole magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the electron beam. Fourier decomposition of beam position monitor data was then used to measure the amplitude of these frequencies at different positions along the beamline. For a purely linear transport system one expects to find solely the frequencies that were applied to the dipoles with amplitudes that depend on the phase advance of the lattice. In the presence of nonlinear fields one expects to also find harmonics of the driving frequencies that depend on the order of the nonlinearity. The technique was calibrated using one of the sextupole magnets in a CEBAF beamline and then applied to a dipole to measure the sextupole and octupole strength of the magnet. A comparison is made between the beam-based measurements, results from TOSCA and data from our Magnet Measurement Facility.

  15. The Electromagnetic Dipole Radiation Field through the Hamiltonian Approach

    ERIC Educational Resources Information Center

    Likar, A.; Razpet, N.

    2009-01-01

    The dipole radiation from an oscillating charge is treated using the Hamiltonian approach to electrodynamics where the concept of cavity modes plays a central role. We show that the calculation of the radiation field can be obtained in a closed form within this approach by emphasizing the role of coherence between the cavity modes, which is…

  16. Correction of magnetization sextupole and decapole in a 5 centimeter bore SSC dipole using passive superconductor

    SciTech Connect

    Green, M.A.

    1991-05-01

    Higher multipoles due to magnetization of the superconductor in four and five centimeter bore Superconducting Super Collider (SSC) superconducting dipole magnets have been observed. The use of passive superconductor to correct out the magnetization sextupole has been demonstrated on two dipoles built by the Lawrence Berkeley Laboratory (LBL). This reports shows how passive correction can be applied to the five centimeter SSC dipoles to remove sextupole and decapole caused by magnetization of the dipole superconductor. Two passive superconductor corrector options will be presented. The change in magnetization sextupole and decapole due to flux creep decay of the superconductor during injection can be partially compensated for using the passive superconductor. 9 refs; 5 figs.

  17. Design and development of Nb{sub 3}Sn single-layer common coil dipole magnet for VLHC

    SciTech Connect

    Giorgio Ambrosio et al.

    2001-07-30

    Common coil dipole magnets based on Nb{sub 3}Sn conductor and the React and Wind technology are a promising option for the next generation of hadron colliders. The react and wind technology has potential cost benefits in terms of cable insulation, structural materials and magnet fabrication. A common coil design allows the use of pre-reacted Nb{sub 3}Sn superconductor with low critical current degradation after bending. Fermilab in collaboration with LBNL is involved in the development of a single-layer common-coil dipole magnet with maximum field of 11 T and 40-50 mm aperture, for a future VLHC. The current magnetic and mechanical designs of the dipole model, magnet parameters along with the status of the program, are reported in this paper.

  18. Polarization of Magnetic Dipole Emission and Spinning Dust Emission from Magnetic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Hoang, Thiem; Lazarian, Alex

    2016-04-01

    Magnetic dipole emission (MDE) from interstellar magnetic nanoparticles is potentially an important Galactic foreground in the microwave frequencies, and its polarization level may pose great challenges for achieving reliable measurements of cosmic microwave background B-mode signal. To obtain realistic predictions for the polarization of MDE, we first compute the degree of alignment of big silicate grains incorporated with magnetic inclusions. We find that thermally rotating big grains with magnetic inclusions are weakly aligned and can achieve alignment saturation when the magnetic alignment rate becomes much faster than the rotational damping rate. We then compute the degree of alignment for free-flying magnetic nanoparticles, taking into account various interaction processes of grains with the ambient gas and radiation field, including neutral collisions, ion collisions, and infrared emission. We find that the rotational damping by infrared emission can significantly decrease the degree of alignment of small particles from the saturation level, whereas the excitation by ion collisions can enhance the alignment of ultrasmall particles. Using the computed degrees of alignment, we predict the polarization level of MDE from free-flying magnetic nanoparticles to be rather low. Such a polarization level is within the upper limits measured for anomalous microwave emission (AME), which indicates that MDE from free-flying iron particles may not be ruled out as a source of AME. We also quantify rotational emission from free-flying iron nanoparticles with permanent magnetic moments and find that its emissivity is about one order of magnitude lower than that from spinning polycyclic aromatic hydrocarbons.

  19. Hydromagnetic waves in a compressed-dipole field via field-aligned Klein-Gordon equations

    NASA Astrophysics Data System (ADS)

    Zheng, Jinlei; Hu, Qiang; Webb, Gary M.; McKenzie, James F.

    2016-05-01

    Hydromagnetic waves, especially those of frequencies in the range of a few millihertz to a few hertz observed in the Earth's magnetosphere, are categorized as ultra low-frequency (ULF) waves or pulsations. They have been extensively studied due to their importance in the interaction with radiation belt particles and in probing the structures of the magnetosphere. We developed an approach to examining the toroidal standing Aflvén waves in a background magnetic field by recasting the wave equation into a Klein-Gordon (KG) form along individual field lines. The eigenvalue solutions to the system are characteristic of a propagation type when the corresponding eigenfrequency is greater than a critical frequency and a decaying type otherwise. We apply the approach to a compressed-dipole magnetic field model of the inner magnetosphere and obtain the spatial profiles of relevant parameters and the spatial wave forms of harmonic oscillations. We further extend the approach to poloidal-mode standing Alfvén waves along field lines. In particular, we present a quantitative comparison with a recent spacecraft observation of a poloidal standing Alfvén wave in the Earth's magnetosphere. Our analysis based on the KG equation yields consistent results which agree with the spacecraft measurements of the wave period and the amplitude ratio between the magnetic field and electric field perturbations.

  20. Photoexcitation of magnetic and electric dipole transitions in heavy nuclei

    NASA Astrophysics Data System (ADS)

    Kneissl, U.; Margraf, J.; Pitz, H. H.; Von Brentano, P.; Herzberg, R.-D.; Zilges, A.

    Systematic nuclear resonance fluorescence (NRF) experiments have been performed at the bremsstrahlung facility of the 4 MV Stuttgart Dynamitron to investigate the distributions of magnetic and electric dipole excitations in heavy nuclei. Precise excitation energies, transition strengths, spins and decay branching ratios were deduced for numerous low lying dipole excitations in heavy spherical and deformed nuclei. Measurements of the linear polarization of resonantly scattered photons using a Compton polarimeter enabled model independent parity assignments. Recent results are presented concerning: the systematics and fragmentation of the M1 “ Scissors Mode” in even-even Rare Earth nuclei, the existence of the “ Scissors Mode” in odd deformed nuclei, 2 + ⊗ 3 - two-phonon E1 excitations in N=82 isotones and Z=50 isotopes, 2 + ⊗ 3 - ⊗ particle multiplets in odd nuclei around N=82, low lying ΔK=0 electric dipole excitations in deformed nuclei, and E1 excitations around 2.6 MeV in deformed nuclei, which are interpreted as candidates for novel two-phonon excitations (coupling of the K=1 octupole and K=2, γ-vibrations).

  1. Production and study of high-beta plasma confined by a superconducting dipole magnet

    SciTech Connect

    Garnier, D.T.; Hansen, A.; Mauel, M.E.; Ortiz, E.; Boxer, A.C.; Ellsworth, J.; Karim, I.; Kesner, J.; Mahar, S.; Roach, A.

    2006-05-15

    The Levitated Dipole Experiment (LDX) [J. Kesner et al., in Fusion Energy 1998, 1165 (1999)] is a new research facility that is exploring the confinement and stability of plasma created within the dipole field produced by a strong superconducting magnet. Unlike other configurations in which stability depends on curvature and magnetic shear, magnetohydrodynamic stability of a dipole derives from plasma compressibility. Theoretically, the dipole magnetic geometry can stabilize a centrally peaked plasma pressure that exceeds the local magnetic pressure ({beta}>1), and the absence of magnetic shear allows particle and energy confinement to decouple. In initial experiments, long-pulse, quasi-steady-state microwave discharges lasting more than 10 s have been produced that are consistent with equilibria having peak beta values of 20%. Detailed measurements have been made of discharge evolution, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition profiles, and plasma boundary shape. In these initial experiments, the high-field superconducting floating coil was supported by three thin supports. The plasma is created by multifrequency electron cyclotron resonance heating at 2.45 and 6.4 GHz, and a population of energetic electrons, with mean energies above 50 keV, dominates the plasma pressure. Creation of high-pressure, high-beta plasma is possible only when intense hot electron interchange instabilities are stabilized by sufficiently high background plasma density. A dramatic transition from a low-density, low-beta regime to a more quiescent, high-beta regime is observed when the plasma fueling rate and confinement time become sufficiently large.

  2. Saturn's Magnetic Field and Magnetosphere.

    PubMed

    Smith, E J; Davis, L; Jones, D E; Coleman, P J; Colburn, D S; Dyal, P; Sonett, C P

    1980-01-25

    The Pioneer Saturn vector helium magnetometer has detected a bow shock and magnetopause at Saturn and has provided an accurate characterization of the planetary field. The equatorial surface field is 0.20 gauss, a factor of 3 to 5 times smaller than anticipated on the basis of attempted scalings from Earth and Jupiter. The tilt angle between the magnetic dipole axis and Saturn's rotation axis is < 1 degrees , a surprisingly small value. Spherical harmonic analysis of the measurements shows that the ratio of quadrupole to dipole moments is < 10 percent, indicating that the field is more uniform than those of the Earth or Jupiter and consistent with Saturn having a relatively small core. The field in the outer magnetosphere shows systematic departures from the dipole field, principally a compression of the field near noon and an equatorial orientation associated with a current sheet near dawn. A hydromagnetic wake resulting from the interaction of Titan with the rotating magnetosphere appears to have been observed.

  3. Magnetic field sensor

    NASA Astrophysics Data System (ADS)

    Silva, Nicolas

    2012-09-01

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

  4. A superferric dipole magnet proposed for use in the superconducting super collider

    NASA Astrophysics Data System (ADS)

    Schmidt, W.

    1985-05-01

    A dipole magnet employing superferric technology has been designed at the Texas Accelerator Center for use in the SSC. This magnet has a maximum central field of 3.0 T and the multipole components are of the order of one part in 10000. Because of the relatively low peak field the forces exerted on the conductors are correspondingly low and the problem of maintaining the conductor placement at high field is minimized. Since the steel provides approximately 1.7 T, the magnet is also fairly insensitive to small errors in the placement of the conductors. These factors contribute to making a magnet which can be mass produced at a relatively low cost.

  5. Atomic electric dipole moment induced by the nuclear electric dipole moment: The magnetic moment effect

    SciTech Connect

    Porsev, S. G.; Ginges, J. S. M.; Flambaum, V. V.

    2011-04-15

    We have considered a mechanism for inducing a time-reversal violating electric dipole moment (EDM) in atoms through the interaction of a nuclear EDM d{sub N} with the hyperfine interaction, the ''magnetic moment effect''. We have derived the operator for this interaction and presented analytical formulas for the matrix elements between atomic states. Induced EDMs in the diamagnetic atoms {sup 129}Xe, {sup 171}Yb, {sup 199}Hg, {sup 211}Rn, and {sup 225}Ra have been calculated numerically. From the experimental limits on the atomic EDMs of {sup 129}Xe and {sup 199}Hg we have placed the following constraints on the nuclear EDMs, |d{sub N}({sup 129}Xe)|<1.1x10{sup -21}|e|cm and |d{sub N}({sup 199}Hg)|<2.8x10{sup -24}|e|cm.

  6. Preliminary results from a study of collar lamination variation in SSC Prototype Dipole Magnets

    SciTech Connect

    Gattu, R.; Brown, G.M.; Pollock, D.

    1993-04-01

    The collar laminations used in SSC Prototype Collider Dipole Magnets determine the volume within which the magnet coils are constrained after collaring and keying. The uniformity and symmetry of the inside volume of the collars along the length of the magnet may have a significant influence on the field quality of the finished assembly. This paper describes an on-going Statistical Quality Control study of collar lamination dimensional variation being performed by SSCL Magnet Systems Division Quality Assurance. Samples of collars have been measured using a coordinate measuring machine evaluate manufacturing process capability as well as the overall uniformity of the inventory population of collar laminations. The collar data will be used to predict variation in the coil assembly center and radius for inner and outer top-bottom, left-right coil combinations well as pole angles. Collar results will be combined with azimuthal coil size measurements part of a manufacturing cause and effect model for predicting axial geometric multipoles based on the observed mechanical variation. This work focuses on Prototype Collider Dipole Magnet DCA 102 currently being built at the SSCL MDL in Waxahachie, Texas. This magnet is being made on the same coil curing and collaring mold cavities that were used for the DCA 300 series magnets built at FNAL in 1991--1992 and which were later used in the 1992 Accelerator Systems String Test (ASST). The collars are part of the same procurement used for the DCA300 series magnets.

  7. Electric and magnetic dipoles in the Lorentz and Einstein-Laub formulations of classical electrodynamics

    NASA Astrophysics Data System (ADS)

    Mansuripur, Masud

    2015-01-01

    The classical theory of electrodynamics cannot explain the existence and structure of electric and magnetic dipoles, yet it incorporates such dipoles into its fundamental equations, simply by postulating their existence and properties, just as it postulates the existence and properties of electric charges and currents. Maxwell's macroscopic equations are mathematically exact and self-consistent differential equations that relate the electromagnetic (EM) field to its sources, namely, electric charge-density 𝜌𝜌free, electric current-density 𝑱𝑱free, polarization 𝑷𝑷, and magnetization 𝑴𝑴. At the level of Maxwell's macroscopic equations, there is no need for models of electric and magnetic dipoles. For example, whether a magnetic dipole is an Amperian current-loop or a Gilbertian pair of north and south magnetic monopoles has no effect on the solution of Maxwell's equations. Electromagnetic fields carry energy as well as linear and angular momenta, which they can exchange with material media—the seat of the sources of the EM field—thereby exerting force and torque on these media. In the Lorentz formulation of classical electrodynamics, the electric and magnetic fields, 𝑬𝑬 and 𝑩𝑩, exert forces and torques on electric charge and current distributions. An electric dipole is then modeled as a pair of electric charges on a stick (or spring), and a magnetic dipole is modeled as an Amperian current loop, so that the Lorentz force law can be applied to the corresponding (bound) charges and (bound) currents of these dipoles. In contrast, the Einstein-Laub formulation circumvents the need for specific models of the dipoles by simply providing a recipe for calculating the force- and torque-densities exerted by the 𝑬𝑬 and 𝑯𝑯 fields on charge, current, polarization and magnetization. The two formulations, while similar in many respects, have significant

  8. Design and Fabrication of a 14 T, Nb3Sn Superconducting Racetrack Dipole Magnet

    SciTech Connect

    Gourlay, S.A.; Bish, P.; Caspi, S.; Chow, K.; Dietderich, D.R.; Gupta, R.; Hannaford, R.; Harnden, W.; Higley, H.; Lietzke, A.; Liggins, N.; McInturff, A.D.; Millos, G.A.; Morrison, L. Morrison M.; Scanlan, R.M.

    1999-09-01

    Most accelerator magnets for applications in the field range up to 10 T utilize NbTi superconductor and a cosine theta coil design. For fields above 10 T, it is necessary to use Nb{sub 3}Sn or other strain sensitive superconductors land other coil geometries that are more compatible with these materials. This paper describes our recent efforts to design a series of racetrack coil magnets that will provide experimental verification of an alternative magnet design philosophy, with the near-term goal of reaching a field level of approximately 14 T. The conductor and fabrication issues relevant to building high field, racetrack dipoles utilizing Nb{sub 3}Sn superconductor and a wind and react approach will also be discussed.

  9. The dipole corrector magnets for the RHIC fast global orbit feedback system

    SciTech Connect

    Thieberger, P.; Arnold, L.; Folz, C.; Hulsart, R.; Jain, A.; Karl, R.; Mahler, G.; Meng, W.; Mernick, K.; Michnoff, R.; Minty, M.; Montag, C.; Ptitsyn, V.; Ritter, J.; Smart, L.; Tuozzolo, J.; White, J.

    2011-03-28

    The recently completed RHIC fast global orbit feedback system uses 24 small 'window-frame' horizontal dipole correctors. Space limitations dictated a very compact design. The magnetic design and modelling of these laminated yoke magnets is described as well as the mechanical implementation, coil winding, vacuum impregnation, etc. Test procedures to determine the field quality and frequency response are described. The results of these measurements are presented and discussed. A small fringe field from each magnet, overlapping the opposite RHIC ring, is compensated by a correction winding placed on the opposite ring's magnet and connected in series with the main winding of the first one. Results from measurements of this compensation scheme are shown and discussed.

  10. Mechanical Analysis of the Nb3Sn Dipole Magnet HD1

    SciTech Connect

    Ferracin, Paolo; Bartlett, Scott E.; Caspi, Shlomo; Dietderich, Daniel R.; Gourlay, Steve A.; Hannaford, Charles R.; Hafalia, Aurelio R.; Lietzke, Alan F.; Mattafirri, Sara; Sabbi, Gianluca

    2005-06-01

    The Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL) has recently fabricated and tested HD1, a Nb3Sn dipole magnet. The magnet reached a 16 T field, and exhibited training quenches in the end regions and in the straight section. After the test, HD1 was disassembled and inspected, and a detailed 3D finite element mechanical analysis was done to investigate for possible quench triggers. The study led to minor modifications to mechanical structure and assembly procedure, which were verified in a second test (HD1b). This paper presents the results of the mechanical analysis, including strain gauge measurements and coil visual inspection. The adjustments implemented in the magnet structure are reported and their effect on magnet training discussed.

  11. Mechanical analysis of the Nb3Sn dipole magnet HD1

    SciTech Connect

    Ferracin, Paolo; Bartlett, Scott E.; Caspi, Shlomo; Dietderich,Daniel R.; Gourlay, Steve A.; Hannaford, Carles R.; Hafalia, Aurelio R.; Lietzke, Alan F.; Mattafirri, Sara; Sabbi, Gianluca

    2005-04-14

    The Superconducting Magnet Group at Lawrence Berkeley National Laboratory (LBNL) has recently fabricated and tested HD1, a Nb{sub 3}Sn dipole magnet. The magnet reached a 16 T field, and exhibited training quenches in the end regions and in the straight section. After the test, HD1 was disassembled and inspected, and a detailed 3D finite element mechanical analysis was done to investigate for possible quench triggers. The study led to minor modifications to mechanical structure and assembly procedure, which were verified in a second test (HD1b). This paper presents the results of the mechanical analysis, including strain gauge measurements and coil visual inspection. The adjustments implemented in the magnet structure are reported and their effect on magnet training discussed.

  12. The design and manufacture of the Fermilab Main Injector Dipole Magnet

    SciTech Connect

    Brown, B.C.; Chester, N.S.; Harding, D.J.; Martin, P.S.

    1992-03-01

    Fermilab`s new Main Injector Ring (MIR) will replace the currently operating Main Ring to provide 150 GeV Proton and Antiproton beams for Tevetron injection, and rapid cycling, high intensity, 120 GeV Proton beams for Antiproton production. To produce and maintain the required high beam quality, high intensity, and high repetition rate, conventional dipole magnets with laminated iron core and water cooled copper conductor were chosen as the bending magnet. A new magnet design having low inductance, large copper cross section, and field uniformity sufficient for high intensity injection and efficient slow resonant extraction, is required to obtain the needed geometric aperture, dynamic aperture, and operational reliability. The current Main Injector Ring lattice design requires the use of 344 of these magnets. 216 of these magnets are to be 6 m long, and 128 are to be 4 m long.

  13. The design and manufacture of the Fermilab Main Injector Dipole Magnet

    SciTech Connect

    Brown, B.C.; Chester, N.S.; Harding, D.J.; Martin, P.S.

    1992-03-01

    Fermilab's new Main Injector Ring (MIR) will replace the currently operating Main Ring to provide 150 GeV Proton and Antiproton beams for Tevetron injection, and rapid cycling, high intensity, 120 GeV Proton beams for Antiproton production. To produce and maintain the required high beam quality, high intensity, and high repetition rate, conventional dipole magnets with laminated iron core and water cooled copper conductor were chosen as the bending magnet. A new magnet design having low inductance, large copper cross section, and field uniformity sufficient for high intensity injection and efficient slow resonant extraction, is required to obtain the needed geometric aperture, dynamic aperture, and operational reliability. The current Main Injector Ring lattice design requires the use of 344 of these magnets. 216 of these magnets are to be 6 m long, and 128 are to be 4 m long.

  14. Superconducting Sphere in an External Magnetic Field Revisited

    ERIC Educational Resources Information Center

    Sazonov, Sergey N.

    2013-01-01

    The purpose of this article is to give the intelligible procedure for undergraduate students to grasp proof of the fact that the magnetic field outside the hollow superconducting sphere (superconducting shell) coincides with the field of a point magnetic dipole both when an uniform external magnetic field is applied as when a ferromagnetic sphere…

  15. A dipole probe for electric field measurements in the LVPD

    NASA Astrophysics Data System (ADS)

    Srivastava, P. K.; Awasthi, L. M.; Ravi, G.; Kumar, Sunil; Mattoo, S. K.

    2016-01-01

    This paper describes the design, construction, and calibration of an electric dipole probe and demonstrates its capability by presenting results on the measurement of electric field excited by a ring electrode in the Large Volume Plasma Device (LVPD). It measures the electric field in vacuum and plasma conditions in a frequency range lying between 1-10 \\text{MHz} . The results show that it measures electric field ≥slant 2 mV cm-1 for frequency ≤slant 10 \\text{MHz} . The developed dipole probe works on the principle of amplitude modulation. The probe signal is transmitted through a carrier of 418 MHz, a much higher frequency than the available sources of noise present in the surrounding environment. The amplitude modulation concept of signal transmission is used to make the measurement; it is qualitatively better and less corrupted as it is not affected by the errors introduced by ac pickups. The probe is capable of measuring a variety of electric fields, namely (1) space charge field, (2) time varying field, (3) inductive field and (4) a mixed field containing both space charge and inductive fields. This makes it a useful tool for measuring electric fields in laboratory plasma devices.

  16. The field of the vertical electric dipole immersed in the heterogeneous half-space

    NASA Astrophysics Data System (ADS)

    Barsukov, P. O.; Fainberg, E. B.

    2014-07-01

    The field of the vertical electric dipole (VED) immersed in the heterogeneous conductive halfspace (sea) is analyzed in time domain. In the near field of the source, the amplitudes of the electric and magnetic components of the field are proportional to power 3/2 and power 5/2 of the conductivity of the medium, respectively. After termination of the transmitter pulse, all the VED components decay with time as ˜1/ t 5/2. The possibility of applying the VED field for estimating the electrical properties of the offshore geological sections is demonstrated.

  17. Field shape measurements of prototype Main Injector dipole endpacks

    SciTech Connect

    Glass, H.D.; Brown, B.C.; Harding, D.J.

    1993-01-06

    Measurements of the transverse dependence of the flux on the symmetry plane were obtained on a series of endpacks mounted on a Main Injector prototype dipole. From these flux measurements, we determined the endfield shape, expressed in terms of normal harmonics, up to 14-pole. We describe the measurement and analysis procedure, and present the results for all endpacks that were tested. The final endpack (number 10) has a sextupole, normalized to the body, of +0.167 [plus minus] .072 units, and the relative field shape deviates by [lt] 1.2 units relative to the on-axis field strength over the range [vert bar]x[vert bar] [lt] 2.0[double prime]. These measurements indicate that Endpack 10 meets the requirements for the Main Injector dipole.

  18. Experimental determination of the magnetic dipole moment of candidate magnetoreceptor cells in trout

    NASA Astrophysics Data System (ADS)

    Winklhofer, M.; Eder, S.; Cadioiu, H.; McNaughton, P. A.; Kirschvink, J. L.

    2011-12-01

    Based on histological, physiological, and physical evidence, Walker et al (1997) and Diebel et al (2000) have identified distinctive cells in the olfactory epithelium of the rainbow trout (Onchorynchus mykiss) that contain magnetite and are closely associated with neurons that respond to changes in magnetic field. To put biophysical constraints on the possible transduction mechanism of magnetic signals, and in particular, to find out if the intracellular magnet is free to rotate or rather firmly anchored within the cell body, we have studied the magneto-mechanical response of isolated candidate receptor cells in suspension using a light microscope equipped with two pairs of Helmholtz coils. From the characteristic re-orientation time of suspended cells after a change in magnetic field direction, we have determined the magnitude of the magnetic dipole moment of the cells in function of the external field strength (0.4 mT to 3.2 mT) in order to find out whether or not the natural magnetic moment is remanence-based or induced (i.e., single-domain vs. superparamagnetic/multi-domain). Results: 1) The mechanical response of isolated cells to a change in magnetic field direction was always immediate, irrespective of the direction of change, which implies that the intracellular magnet is not free to rotate in the cell, but rather rigidly attached, probably to the plasma membrane, which is also suggested by our confocal fluorescence-microscope studies. 2) The cellular dipole moment turned out to be independent of the external field strength. Thus, the natural magnetic dipole moment is based on magnetic remanence, which points to single-domain particles and corroborates the results by Diebel et al (2000), who obtained switching fields consistent with single-domain magnetite. 3). The magnetic dipole moment is found to be of the order of several tens of fAm2, which greatly exceeds previous estimates (0.5 fAm2), and thus is similar to values reported for the most strongly

  19. Design, Fabrication, and Test of a Superconducting Dipole Magnet Based on Tilted Solenoids

    SciTech Connect

    Caspi, S.; Dietderich, D. R.; Ferracin, P.; Finney, N. R.; Fuery, M. J.; Gourlay, S. A.; Hafalia, A. R.

    2007-06-01

    It can be shown that, by superposing two solenoid-like thin windings that are oppositely skewed (tilted) with respect to the bore axis, the combined current density on the surface is 'cos-theta' like and the resulting magnetic field in the bore is a pure dipole. As a proof of principle, such a magnet was designed, built and tested as part of a summer undergraduate intern project. The measured field in the 25mm bore, 4 single strand layers using NbTi superconductor, exceeded 1 T. The simplicity of this high field quality design, void of typical wedges end-spacers and coil assembly, is especially suitable for insert-coils using High Temperature Superconducting wire as well as for low cost superconducting accelerator magnets for High Energy Physics. Details of the design, construction and test are reported.

  20. Dipole-dipole resistivity monitoring at the Cerro Prieto geothermal field

    SciTech Connect

    Wilt, M.J.; Goldstein, N.E.

    1983-03-01

    Two 20 km-long dipole-dipole lines with permanently emplaced electronics at 1-km spacings were established over the field area; one of these lines is remeasured annually. Resistivity measurements are taken using a 25 kW generator capable of up to 80A output and a microprocessor-controlled signal-averaging receiver; this high power-low noise system is capable of highly accurate measurements even at large transmitter-receiver separations. Standard error calculations for collected data indicate errors less than 5% for all points, but 95% confidence intervals show error limits about 2 to 4 times higher. Data indicate little change of apparent resistivity within the upper 300 m over the field. However, apparent resistivity increases are observed over the producing zone at depths of 1 km and greater. Large zones of decreasing apparent resistivity are observed flanking the zone of increases on both sides. To explain the resistivity changes observed, simple two-dimensional reservoir simulations were performed in which cooler, less saline recharge water enters the reservoir from above through a leaky caprock and laterally through a more permeable vertical boundary. The calculated magnitude of a resistivity change after 3 years of simulated production fits the observed data, but the anomaly shapes differ. It is concluded that the rapidly moving hydraulic front produces a salinity change large enough to explain the resistivity increase, but that our recharge assumptions were probably oversimplified.

  1. 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.

  2. An explanation for both the large inclination and eccentricity of the dipole-like field of Uranus and Neptune

    NASA Technical Reports Server (NTRS)

    Akasofu, S.-I.; Lee, L.-H.; Saito, T.

    1991-01-01

    It is shown that the offset tilted dipole model of Uranus and Neptune, deduced from the spherical harmonic analysis of the Voyager magnetic field observation, can be represented fairly well by the combined field of an axial and an auxiliary dipole; the latter is roughly oriented in the east-west direction and is located near the surface of the core in low latitude. The present dynamo theories of planetary magnetism consider an axial dipolar field as an essential element, since the planetary rotation plays a vital role in the dynamo process. On the other hand, the auxiliary dipoles may be a result of leakage of the toroidal field, like a pair of sunspots on the photosphere, which is also an essential part of the dynamo process.

  3. Effect of core polarization on magnetic dipole moments in deformed odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Bonneau, L.; Minkov, N.; Duc, Dao Duy; Quentin, P.; Bartel, J.

    2015-05-01

    Magnetic properties of deformed odd-mass nuclei are studied within a nonrelativistic mean-field-plus-pairing approach, namely the Skyrme-Hartree-Fock-BCS approach with self-consistent blocking. For an odd number of nucleons these approaches lead to the breaking of the time-reversal invariance. The deviation from the Schmidt values of the isoscalar magnetic dipole moment is known to result from a subtle balance between core-polarization effects and meson-exchange current effects. However, the former are usually calculated in the random phase approximation without time-reversal symmetry breaking at the mean-field level. In this work we show that if one takes into account this symmetry breaking already in the mean-field solution, the correction from core polarization yields a significant contribution to the empirical quenching of the spin gyromagnetic ratios as compared to the free values in deformed odd-mass nuclei. Moreover, we calculate magnetic dipole moments in the Bohr and Mottelson unified-model description with self-consistent blocked mean-field intrinsic states. The obtained results in the A ˜100 and A ˜180 mass regions as well as for three actinide nuclei compare favorably with experimental data.

  4. Facility Measures Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Honess, Shawn B.; Narvaez, Pablo; Mcauley, James M.

    1991-01-01

    Partly automated facility measures and computes steady near magnetic field produced by object. Designed to determine magnetic fields of equipment to be installed on spacecraft including sensitive magnetometers, with view toward application of compensating fields to reduce interfernece with spacecraft-magnetometer readings. Because of its convenient operating features and sensitivity of its measurements, facility serves as prototype for similar facilities devoted to magnetic characterization of medical equipment, magnets for high-energy particle accelerators, and magnetic materials.

  5. A new estimate of average dipole field strength for the last five million years

    NASA Astrophysics Data System (ADS)

    Cromwell, G.; Tauxe, L.; Halldorsson, S. A.

    2013-12-01

    The Earth's ancient magnetic field can be approximated by a geocentric axial dipole (GAD) where the average field intensity is twice as strong at the poles than at the equator. The present day geomagnetic field, and some global paleointensity datasets, support the GAD hypothesis with a virtual axial dipole moment (VADM) of about 80 ZAm2. Significant departures from GAD for 0-5 Ma are found in Antarctica and Iceland where paleointensity experiments on massive flows (Antarctica) (1) and volcanic glasses (Iceland) produce average VADM estimates of 41.4 ZAm2 and 59.5 ZAm2, respectively. These combined intensities are much closer to a lower estimate for long-term dipole field strength, 50 ZAm2 (2), and some other estimates of average VADM based on paleointensities strictly from volcanic glasses. Proposed explanations for the observed non-GAD behavior, from otherwise high-quality paleointensity results, include incomplete temporal sampling, effects from the tangent cylinder, and hemispheric asymmetry. Differences in estimates of average magnetic field strength likely arise from inconsistent selection protocols and experiment methodologies. We address these possible biases and estimate the average dipole field strength for the last five million years by compiling measurement level data of IZZI-modified paleointensity experiments from lava flows around the globe (including new results from Iceland and the HSDP-2 Hawaii drill core). We use the Thellier Gui paleointensity interpreter (3) in order to apply objective criteria to all specimens, ensuring consistency between sites. Specimen level selection criteria are determined from a recent paleointensity investigation of modern Hawaiian lava flows where the expected magnetic field strength was accurately recovered when following certain selection parameters. Our new estimate of average dipole field strength for the last five million years incorporates multiple paleointensity studies on lava flows with diverse global and

  6. Electric Dipole Moment Experiment Systematic from Electric Field Discharge Current

    NASA Astrophysics Data System (ADS)

    Feinberg, B.; Gould, Harvey

    2014-09-01

    A magnetic field, in the direction of the electric field and synchronous with the electric field reversal, will mimic an EDM signal. One might expect a discharge across the electric field plates to produce magnetic fields with only small or vanishing components parallel to the electric field, minimizing its systematic effect. Our experimental model, using simulated discharge currents, found otherwise: the discharge current may be at an angle to the normal, and thus generate a normal magnetic field. Comparison of data from the experimental model with the results from calculations will be presented, along with estimates of the time-averaged normal magnetic field seen by atoms in an electron EDM experiment using a fountain of laser-cooled francium, as a function of discharge current.

  7. Temperature dependence of magnetic moments of nanoparticles and their dipole interaction in magnetic fluids

    NASA Astrophysics Data System (ADS)

    Lebedev, A. V.

    2015-01-01

    Magnetic susceptibility measurements were carried out for magnetite-based fluids over a wide temperature range. The fluids were stabilized with commonly used surfactants (fatty acids) and new surfactants (polypropylene glycol and tallow acids). The coefficients of temperature dependence of the particle magnetic moments were determined by fitting of the measured and calculated values of magnetic susceptibility. The influence of the inter-particle dipole-dipole interaction on the susceptibility was taken into account in the framework of A.O. Ivanov's model. The corrections for thermal expansion were determined by density measurements of the carrier fluid. The obtained values of temperature coefficients correlate to the solidification temperature of the fluid samples. For fluids with a low solidification temperature the value of the temperature coefficient of particle magnetization coincides with its value for bulk magnetite.

  8. Magnetic field mapper

    NASA Technical Reports Server (NTRS)

    Masters, R. M.; Stenger, F. J.

    1969-01-01

    Magnetic field mapper locates imperfections in cadmium sulphide solar cells by detecting and displaying the variations of the normal component of the magnetic field resulting from current density variations. It can also inspect for nonuniformities in other electrically conductive materials.

  9. Visualizing Special Relativity: The Field of An Electric Dipole Moving at Relativistic Speed

    ERIC Educational Resources Information Center

    Smith, Glenn S.

    2011-01-01

    The electromagnetic field is determined for a time-varying electric dipole moving with a constant velocity that is parallel to its moment. Graphics are used to visualize this field in the rest frame of the dipole and in the laboratory frame when the dipole is moving at relativistic speed. Various phenomena from special relativity are clearly…

  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. The magnetic field and magnetospheric configuration of Uranus

    NASA Technical Reports Server (NTRS)

    Ness, Norman F.; Connerney, John E. P.; Lepping, Ronald P.; Schulz, Michael; Voigt, Gerd-Hannes

    1991-01-01

    A significant and unique planetary magnetic field discovered by Voyager 2 is presented. A large tilt of 58.6 deg of the magnetic-dipole axis from the rotation axis was found. Combined with a large offset of 0.3 RU of the magnetic dipole from the center of the planet, the moment of 0.23 gauss-RU3 leads to field magnitudes at the surface which vary widely between 0.1 and 1.0 gauss. A simple diagram illustrating the offset tilted dipole of Uranus and some field lines is shown. A more exact and accurate spherical-harmonic model of the planetary field, which includes both dipole and quadrupole moments, is derived. There exists a well-developed bipolar magnetic tail on the night side of the planet which rotates daily about the extended planet-sunline with Uranus because of the large obliquity of the Uranian rotation axis.

  12. Test Results of HD2, A High Field Nb3Sn Dipole with A 36 MM Bore

    SciTech Connect

    Ferracin, Paolo

    2008-05-19

    The Superconducting Magnet Program at Lawrence Berkeley National Laboratory (LBNL) has developed the 1 m long Nb{sub 3}Sn dipole magnet HD2. With tilted (flared) ends to avoid obstructing a 36 mm clear bore, HD2 represents a step towards the use of block-type coils in high-field accelerator magnets. The coil design has been optimized to minimize geometric harmonics and reduce the conductor peak field in the end region, resulting in an expected short sample dipole field of 15 T. The support structure is composed by an external aluminum shell pre-tensioned with pressurized bladders and interference keys, and by two stainless steel end plates compressing the coil ends through four aluminum axial rods. We report on magnet design, assembly, and test results, including training performance, quench locations, and strain gauge measurements.

  13. Permanent dipole magnets for the 8 GeV transfer line at FNAL

    SciTech Connect

    Glass, H.D.; Brown, B.C.; Foster, G.W.; Fowler, W.B.; Haggard, J.E.

    1997-06-01

    The transfer line that will serve to transport 8 GeV protons from the Booster to the new Fermilab Main Injector has been built using permanent magnets. A total of 46 horizontal bend dipoles and 5 vertical bend dipoles were built for this beamline; 67 gradient magnets were also built. The magnets were built using magnetized strontium ferrite bricks. Thermal compensation of these bricks was effected by use of a nickel-iron alloy. The dipole magnets were built with a mean integrated strength of 0.56954 T-m, and an rms spread of 0.06%. The magnets were thermally cycled from 20{degrees}C to 0{degrees}C to condition the ferrite against irreversible thermal losses, and the compensation was measured with a flipcoil. The magnet strength was adjusted by varying the number of bricks installed at the magnet ends. Details of the assembly process and a summary of magnetic measurements are presented here.

  14. (129) Xe and (131) Xe nuclear magnetic dipole moments from gas phase NMR spectra.

    PubMed

    Makulski, Włodzimierz

    2015-04-01

    (3) He, (129) Xe and (131) Xe NMR measurements of resonance frequencies in the magnetic field B0=11.7586 T in different gas phase mixtures have been reported. Precise radiofrequency values were extrapolated to the zero gas pressure limit. These results combined with new quantum chemical values of helium and xenon nuclear magnetic shielding constants were used to determine new accurate nuclear magnetic moments of (129) Xe and (131) Xe in terms of that of the (3) He nucleus. They are as follows: μ((129) Xe) = -0.7779607(158)μN and μ((131) Xe) = +0.6918451(70)μN . By this means, the new 'helium method' for estimations of nuclear dipole moments was successfully tested. Gas phase NMR spectra demonstrate the weak intermolecular interactions observed on the (3) He and (129) Xe and (131) Xe shielding in the gaseous mixtures with Xe, CO2 and SF6 .

  15. 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

  16. The symmetry properties of planetary magnetic fields

    NASA Technical Reports Server (NTRS)

    Raedler, Karl-Heinz; Ness, Norman F.

    1990-01-01

    This paper provides a comparative study of the geometrical structures of the magnetic fields of earth, Jupiter, Saturn, and Uranus, starting from the traditional multipolar representations of these fields. For earth, Jupiter, and Saturn, the centered dipole, quadrupole, and octupole contributions are included, while at Uranus only the dipole and quadrupole contributions are considered. It is found that there are a number of common features of the magnetic fields of earth and Jupiter. Compared to earth and Jupiter, the Saturnian field exhibits not only a high degree of symmetry about the rotation axis but also a high degree of antisymmetry about the equatorial plane. The Uranian field shows strong deviations from both such symmetries. Nevertheless, there remain features common to all four planets.

  17. 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.

  18. Extending the radial diffusion model of Falthammar to non-dipole background field

    SciTech Connect

    Cunningham, Gregory Scott

    2015-05-26

    A model for radial diffusion caused by electromagnetic disturbances was published by Falthammar (1965) using a two-parameter model of the disturbance perturbing a background dipole magnetic field. Schulz and Lanzerotti (1974) extended this model by recognizing the two parameter perturbation as the leading (non--dipole) terms of the Mead Williams magnetic field model. They emphasized that the magnetic perturbation in such a model induces an electric ield that can be calculated from the motion of field lines on which the particles are ‘frozen’. Roederer and Zhang (2014) describe how the field lines on which the particles are frozen can be calculated by tracing the unperturbed field lines from the minimum-B location to the ionospheric footpoint, and then tracing the perturbed field (which shares the same ionospheric footpoint due to the frozen -in condition) from the ionospheric footpoint back to a perturbed minimum B location. The instantaneous change n Roederer L*, dL*/dt, can then be computed as the product (dL*/dphi)*(dphi/dt). dL*/Dphi is linearly dependent on the perturbation parameters (to first order) and is obtained by computing the drift across L*-labeled perturbed field lines, while dphi/dt is related to the bounce-averaged gradient-curvature drift velocity. The advantage of assuming a dipole background magnetic field, as in these previous studies, is that the instantaneous dL*/dt can be computed analytically (with some approximations), as can the DLL that results from integrating dL*/dt over time and computing the expected value of (dL*)^2. The approach can also be applied to complex background magnetic field models like T89 or TS04, on top of which the small perturbations are added, but an analytical solution is not possible and so a numerical solution must be implemented. In this talk, I discuss our progress in implementing a numerical solution to the calculation of DL*L* using arbitrary background field models with simple electromagnetic

  19. Polarity reversals and tilt of the Earth's magnetic dipole

    NASA Technical Reports Server (NTRS)

    Dolginov, A. Z.

    1993-01-01

    There is evidence that the terrestrial magnetic field is connected with the Earth's mantle: (1) there are magnetic anomalies that do not take part in the westward drift of the main field, but are fixed with respect to the mantle; (2) the geomagnetic pole position flips in a particular way by preferred meridional paths during a reversal; and (3) magnetic polarity reversals are correlated with the activations of geological processes. These facts may be explained if we take into account that a significant horizontal temperature gradient can exist in the top levels of the liquid core because of the different thermoconductivity of the different areas of the core-mantle boundary. These temperature inhomogeneities can penetrate the core because fluxes along the core boundary (the thermal wind) can be strongly suppressed by a small redistribution of the chemical composition in the top of the core. The nonparallel gradients of the temperature, density, and composition on the top of the core create a curled electric field that produces a current and a magnetic field. This seed-field can be amplified by motions in the core. The resulting field does not forget the seed-field distribution and in this way the field on the Earth surface (that can be created only in regions with high conductivity, i.e. in the core) is connected with the core-mantle boundary. Contrary to the usual approach to the dynamo problem, we will take into account that the seed field of thermoelectric origin is acting not only at some initial moment of time but permanently.

  20. 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.

  1. Near-field dipole radiation dynamics through FDTD modeling

    NASA Astrophysics Data System (ADS)

    Radzevicius, Stanley J.; Chen, Chi-Chih; Peters, Leon; Daniels, Jeffrey J.

    2003-02-01

    We use finite-difference time-domain (FDTD) numerical simulations to study horizontal dipole radiation mechanisms and patterns near half-space interfaces. Time snapshots illustrating propagation of wavefronts at an instance in time are included with antenna patterns to provide a visualization tool for understanding antenna radiation properties. Near-field radiation patterns are compared with far-field asymptotic solutions and the effects of electrical properties, antenna height, and observation distance are investigated through numerical simulations. Numerical simulations show excellent agreement with measured data collected over a water-filled tank. Near-field H-plane radiation patterns are broader and contain radiation maxima beyond the critical angle predicted by far-field solutions. A large amplitude E-plane radiation lobe is located directly below the antenna in all simulations, while the two large amplitude sidelobes are less distinct and occur at larger incidence angles than predicted by far-field solutions. Radiation patterns resemble far-field solutions by a distance of 10 wavelengths, except near the critical angle where H-plane radiation maxima and E-plane sidelobes occur at larger incidence angles than predicted by far-field solutions.

  2. The somatosensory evoked magnetic fields.

    PubMed

    Kakigi, R; Hoshiyama, M; Shimojo, M; Naka, D; Yamasaki, H; Watanabe, S; Xiang, J; Maeda, K; Lam, K; Itomi, K; Nakamura, A

    2000-08-01

    Averaged magnetoencephalography (MEG) following somatosensory stimulation, somatosensory evoked magnetic field(s) (SEF), in humans are reviewed. The equivalent current dipole(s) (ECD) of the primary and the following middle-latency components of SEF following electrical stimulation within 80-100 ms are estimated in area 3b of the primary somatosensory cortex (SI), the posterior bank of the central sulcus, in the hemisphere contralateral to the stimulated site. Their sites are generally compatible with the homunculus which was reported by Penfield using direct cortical stimulation during surgery. SEF to passive finger movement is generated in area 3a or 2 of SI, unlike with electrical stimulation. Long-latency components with peaks of approximately 80-120 ms are recorded in the bilateral hemispheres and their ECD are estimated in the secondary somatosensory cortex (SII) in the bilateral hemispheres. We also summarized (1) the gating effects on SEF by interference tactile stimulation or movement applied to the stimulus site, (2) clinical applications of SEF in the fields of neurosurgery and neurology and (3) cortical plasticity (reorganization) of the SI. SEF specific to painful stimulation is also recorded following painful stimulation by CO(2) laser beam. Pain-specific components are recorded over 150 ms after the stimulus and their ECD are estimated in the bilateral SII and the limbic system. We introduced a newly-developed multi (12)-channel gradiometer system with the smallest and highest quality superconducting quantum interference device (micro-SQUID) available to non-invasively detect the magnetic fields of a human peripheral nerve. Clear nerve action fields (NAFs) were consistently recorded from all subjects.

  3. New constraints on historical dipole field decay: Four centuries of archaeointensity from Cape Town, South Africa.

    NASA Astrophysics Data System (ADS)

    Hare, V. J.; Gallet, Y.; Genevey, A.

    2015-12-01

    Current global geomagnetic field models suffer from strong bias towards Northern Hemisphere data. Absolute intensity measurements from the Southern Hemisphere are key to understanding the evolution of the field over the historical era, especially recent strengthening of non-dipole contributions, and the appearance of the South Atlantic Magnetic Anomaly (SAMA). I present the first archaeointensity data for locally-fired historical bricks from several well-dated sites (1660-2009 AD) in Cape Town, South Africa. These data constitute the first archaeomagnetic intensity variation curve for southern Africa for the past few centuries. The ages of the sites are tightly constrained by historical and archaeological considerations. Archaeointensity data obtained by the Thellier and Thellier method (modified by Coe), are corrected for both TRM anisotropy and cooling rate dependence of TRM acquisition. Analysis of magnetic mineralogy was performed to aid selection of fragments. Reliable archaeointensity determinations were obtained for 48 of 80 specimens, and 45 were retained in the final analysis. Intensity results vary from 24.3 ± 0.6 μT (modern brick) to 40.7 ± 0.8 μT (1660 AD), corresponding to Virtual Axial Dipole Moments (VADMs) between 6.1 ± 0.2 and 10.2 ± 0.2 נ1022 Am2. Results are generally not in agreement with current field models, but are coherent with other archaeomagnetic datasets from the Southern Hemisphere. The possible reasons for this are discussed, as well as implications for the historical evolution of the field.

  4. What we have learned about the magnetic field of Mars

    NASA Technical Reports Server (NTRS)

    Dolginov, S. S.

    1985-01-01

    Sufficient and unambiguous evidences of the intrinsic martian magnetic field are: (1) the independence of the field polarity in Maritan magnetic tail from interplanetary magnetic fields (IMF) polarity inversion, established with the help of Mars-5 data; and (2) the incongruity between the sign of the radial component of the field measured in Martian tail (Mars-2) and that of the draped model with IMF data measured simultaneously (Mars-3) on February 23-24, 1972. Mar's dipole magnetic moment is within the limits (1.5 to 2.2) x 10 to e 22 G cc. The dipole axis is deflected from that of rotation on the angle I 15 deg. The North magnetic pole is located in the South Hemisphere. In the frame of the precession-dinamo model the magnetic fields of the planets Mars and Earth are similar. The Martian magnetic field is the real obstacle for the solar wind near the planet.

  5. What we have learned about the magnetic field of Mars

    NASA Astrophysics Data System (ADS)

    Dolginov, S. S.

    Sufficient and unambiguous evidences of the intrinsic martian magnetic field are: (1) the independence of the field polarity in Maritan magnetic tail from interplanetary magnetic fields (IMF) polarity inversion, established with the help of Mars-5 data; and (2) the incongruity between the sign of the radial component of the field measured in Martian tail (Mars-2) and that of the draped model with IMF data measured simultaneously (Mars-3) on February 23-24, 1972. Mar's dipole magnetic moment is within the limits (1.5 to 2.2) x 10 to e 22 G cc. The dipole axis is deflected from that of rotation on the angle I 15 deg. The North magnetic pole is located in the South Hemisphere. In the frame of the precession-dinamo model the magnetic fields of the planets Mars and Earth are similar. The Martian magnetic field is the real obstacle for the solar wind near the planet.

  6. Effect of manufacturing errors on field quality of the LBL SSC dipoles

    SciTech Connect

    Meuser, R.B.

    1984-01-01

    A method is developed for determining the field aberrations resulting from specific kinds of manufacturing errors. This method is applied to the 40-mm i.d. dipoles under consideration at LBL, and also to similar ones with 30 and 50 mm i.d. The method is also applied to the CBA and Doubler/Saver magnets and the results compared with the measurements. The results obtained by this method are also compared with those obtained by assigning identical errors to the positions of the edges of all the coil sectors.

  7. Classical electrodynamics in material media and relativistic transformation of magnetic dipole moment

    NASA Astrophysics Data System (ADS)

    Kholmetskii, A. L.; Missevitch, O. V.; Yarman, T.

    2016-09-01

    We consider the relativistic transformation of the magnetic dipole moment and disclose its physical meaning, shedding light on the related difficulties in the physical interpretation of classical electrodynamics in material media.

  8. Heat leak testing of a superconducting RHIC dipole magnet at Brookhaven National Laboratory

    SciTech Connect

    DeLalio, J.T.; Brown, D.P.; Sondericker, J.H.

    1993-09-01

    Brookhaven National Laboratory is currently performing heat load tests on a superconducting dipole magnet. The magnet is a prototype of the 360, 8 cm bore, arc dipole magnets that will be used in the Relativistic Heavy Ion Collider (RMC). An accurate measurement of the heat load is needed to eliminate cumulative errors when determining the REUC cryogenic system load requirements. The test setup consists of a dipole positioned between two quadrupoles in a common vacuum tank and heat shield. Piping and instrumentation are arranged to facilitate measurement of the heat load on the primary 4.6 K magnet load and the secondary 55 K heat shield load. Initial results suggest that the primary heat load is well below design allowances. The secondary load was found to be higher than estimated, but remained close to the budgeted amount. Overall, the dipole performed to specifications.

  9. The magnetic fields of Mercury, Mars, and moon

    NASA Technical Reports Server (NTRS)

    Ness, N. F.

    1979-01-01

    Mariner observations have shown a significant global magnetic field at Mercury with a dipole moment at a tilt of 14 + or - 5 deg relative to the normal of the orbit plane. A presently active dynamo is the most likely origin for the planet's magnetic field. Limited evidence for an intrinsic magnetic field on Mars was obtained by USSR spacecraft in 1971 and 1974. The Martian magnetic field, if it exists, may result from either remanent magnetism or an active dynamo. On the moon, local magnetic fields have been detected by the Apollo and Lunokhod missions, but no global correlation of the steady state values has been noted.

  10. Measurements of beam pipe eddy current effects in Main Injector dipole magnets

    SciTech Connect

    Walbridge, D.G.C.; Bleadon, M.E.; Brown, B.C.; Glass, H.D.; Harding, D.J.; Mazur, P.O.; Sim, J.W.

    1992-08-01

    The dipole magnets for the proposed Main Injector project at Fermilab are designed to ramp to maximum field (1.7 T) at rates over 2.5 T/s. These ramp rates will produce eddy current effects which degrade overall field quality. A harmonics probe was constructed for the purpose of measuring eddy current field components during the ramp cycle. Three separate ramp rates were employed ranging from 1.3 T/s to 2.7 T/s. Tests were performed using beam pipes with two different resistivities. The dominant multipole contribution resulting from eddy current effects in each beam pipe was sextupole. The sextupole component closely matched the calculated prediction.

  11. Enhanced second-harmonic generation driven from magnetic dipole resonance in AlGaAs nanoantennas

    NASA Astrophysics Data System (ADS)

    Carletti, Luca; Rocco, Davide; Locatelli, Andrea; Gili, Valerio; Leo, Giuseppe; De Angelis, Costantino

    2016-04-01

    We model the linear and nonlinear optical response of disk-shaped AlGaAs nanoantennas. We design nanoantennas with a magnetic dipole resonant mode in the near-infrared wavelength range, and we analyze volume second-harmonic generation driven by a magnetic dipole resonance by predicting a conversion efficiency exceeding 10-3 with 1 GW/cm2 of pump intensity.

  12. Opening the cusp. [using magnetic field topology

    NASA Technical Reports Server (NTRS)

    Crooker, N. U.; Toffoletto, F. R.; Gussenhoven, M. S.

    1991-01-01

    This paper discusses the magnetic field topology (determined by the superposition of dipole, image, and uniform fields) for mapping the cusp to the ionosphere. The model results are compared to both new and published observations and are then used to map the footprint of a flux transfer event caused by a time variation in the merging rate. It is shown that the cusp geometry distorts the field lines mapped from the magnetopause to yield footprints with dawn and dusk protrusions into the region of closed magnetic flux.

  13. Test Results for HD1, a 16 Tesla Nb3Sn Dipole Magnet

    SciTech Connect

    Lietzke, A.F.; Bartlett, S.; Bish, P.; Caspi, S.; Chiesa, L.; Dietderich, D.; Ferracin, P.; Gourlay, S.A.; Goli, M.; Hafalia, R.R.; Higley, H.; Hannaford, R.; Lau, W.; Liggens, N.; Mattafirri, S.; McInturff, A.; Nyman, M.; Sabbi, G.; Scanlan, R.; Swanson, J.

    2003-10-01

    The Superconducting Magnet Group at Lawrence Berkeley National Laboratory has been developing the technology for using brittle superconductor in high-field accelerator magnets. HD1, the latest in a series of magnets, contains two, double-layer Nb{sub 3}Sn flat racetrack coils. This single-bore dipole configuration, using the highest performance conductor available, was designed and assembled for a 16 tesla conductor/structure/pre-stress proof-of-principle. With the combination of brittle conductor and high Lorentz stress, considerable care was taken to predict the magnet's mechanical responses to pre-stress, cool-down, and excitation. Subsequent cold testing satisfied expectations: Training started at 13.6 T, 83% of 'short-sample', achieved 90% in 10 quenches, and reached its peak bore field (16 T) after 19 quenches. The average plateau, {approx}92% of 'short-sample', appeared to be limited by 'stick-slip' conductor motions, consistent with the 16.2 T conductor 'lift-off' pre-stress that was chosen for this first test. Some lessons learned and some implications for future conductor and magnet technology development are presented and discussed.

  14. Novel epoxy-free construction method for fabricating dipole magnets and test results

    SciTech Connect

    Taylor, C.; Althaus, R.; Caspi, S.; Gilbert, W.S.; Hassenzahl, W.; Meuser, R.; Rechen, J.; Warren, R.

    1981-01-01

    Three model superconducting dipole magnets, lm length and having a bore diameter of 76mm, fabricated without epoxy resins or other adhesives, have been built and the first two have been tested in He I and He II. The conductor is the 23-strand Rutherford-type cable used in the Fermilab Doubler/Saver magnets, and is insulated with Mylar and Kapton. The two-layer winding is highly compessed by a system of structural support rings and tapered collets. Little training was required. Quench currents greater than 95% of short sample were obtained in He I with rise-times of 15 to 20 seconds to a central field of 4.6 T; 6.0 T in Helium II.

  15. Low-degree Structure in Mercury's Planetary Magnetic Field

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  16. Magnetic-Field-Assisted Assembly of Anisotropic Superstructures by Iron Oxide Nanoparticles and Their Enhanced Magnetism.

    PubMed

    Jiang, Chengpeng; Leung, Chi Wah; Pong, Philip W T

    2016-12-01

    Magnetic nanoparticle superstructures with controlled magnetic alignment and desired structural anisotropy hold promise for applications in data storage and energy storage. Assembly of monodisperse magnetic nanoparticles under a magnetic field could lead to highly ordered superstructures, providing distinctive magnetic properties. In this work, a low-cost fabrication technique was demonstrated to assemble sub-20-nm iron oxide nanoparticles into crystalline superstructures under an in-plane magnetic field. The gradient of the applied magnetic field contributes to the anisotropic formation of micron-sized superstructures. The magnitude of the applied magnetic field promotes the alignment of magnetic moments of the nanoparticles. The strong dipole-dipole interactions between the neighboring nanoparticles lead to a close-packed pattern as an energetically favorable configuration. Rod-shaped and spindle-shaped superstructures with uniform size and controlled spacing were obtained using spherical and polyhedral nanoparticles, respectively. The arrangement and alignment of the superstructures can be tuned by changing the experimental conditions. The two types of superstructures both show enhancement of coercivity and saturation magnetization along the applied field direction, which is presumably associated with the magnetic anisotropy and magnetic dipole interactions of the constituent nanoparticles and the increased shape anisotropy of the superstructures. Our results show that the magnetic-field-assisted assembly technique could be used for fabricating nanomaterial-based structures with controlled geometric dimensions and enhanced magnetic properties for magnetic and energy storage applications.

  17. Magnetohydrodynamic simulations of hypersonic flow over a cylinder using axial- and transverse-oriented magnetic dipoles.

    PubMed

    Guarendi, Andrew N; Chandy, Abhilash J

    2013-01-01

    Numerical simulations of magnetohydrodynamic (MHD) hypersonic flow over a cylinder are presented for axial- and transverse-oriented dipoles with different strengths. ANSYS CFX is used to carry out calculations for steady, laminar flows at a Mach number of 6.1, with a model for electrical conductivity as a function of temperature and pressure. The low magnetic Reynolds number (<1) calculated based on the velocity and length scales in this problem justifies the quasistatic approximation, which assumes negligible effect of velocity on magnetic fields. Therefore, the governing equations employed in the simulations are the compressible Navier-Stokes and the energy equations with MHD-related source terms such as Lorentz force and Joule dissipation. The results demonstrate the ability of the magnetic field to affect the flowfield around the cylinder, which results in an increase in shock stand-off distance and reduction in overall temperature. Also, it is observed that there is a noticeable decrease in drag with the addition of the magnetic field. PMID:24307870

  18. Magnetohydrodynamic simulations of hypersonic flow over a cylinder using axial- and transverse-oriented magnetic dipoles.

    PubMed

    Guarendi, Andrew N; Chandy, Abhilash J

    2013-01-01

    Numerical simulations of magnetohydrodynamic (MHD) hypersonic flow over a cylinder are presented for axial- and transverse-oriented dipoles with different strengths. ANSYS CFX is used to carry out calculations for steady, laminar flows at a Mach number of 6.1, with a model for electrical conductivity as a function of temperature and pressure. The low magnetic Reynolds number (<1) calculated based on the velocity and length scales in this problem justifies the quasistatic approximation, which assumes negligible effect of velocity on magnetic fields. Therefore, the governing equations employed in the simulations are the compressible Navier-Stokes and the energy equations with MHD-related source terms such as Lorentz force and Joule dissipation. The results demonstrate the ability of the magnetic field to affect the flowfield around the cylinder, which results in an increase in shock stand-off distance and reduction in overall temperature. Also, it is observed that there is a noticeable decrease in drag with the addition of the magnetic field.

  19. Magnetohydrodynamic Simulations of Hypersonic Flow over a Cylinder Using Axial- and Transverse-Oriented Magnetic Dipoles

    PubMed Central

    Guarendi, Andrew N.; Chandy, Abhilash J.

    2013-01-01

    Numerical simulations of magnetohydrodynamic (MHD) hypersonic flow over a cylinder are presented for axial- and transverse-oriented dipoles with different strengths. ANSYS CFX is used to carry out calculations for steady, laminar flows at a Mach number of 6.1, with a model for electrical conductivity as a function of temperature and pressure. The low magnetic Reynolds number (≪1) calculated based on the velocity and length scales in this problem justifies the quasistatic approximation, which assumes negligible effect of velocity on magnetic fields. Therefore, the governing equations employed in the simulations are the compressible Navier-Stokes and the energy equations with MHD-related source terms such as Lorentz force and Joule dissipation. The results demonstrate the ability of the magnetic field to affect the flowfield around the cylinder, which results in an increase in shock stand-off distance and reduction in overall temperature. Also, it is observed that there is a noticeable decrease in drag with the addition of the magnetic field. PMID:24307870

  20. Critical behavior of isotropic three-dimensional systems with dipole-dipole interactions

    SciTech Connect

    Belim, S. M.

    2013-06-15

    The critical behavior of Heisenberg magnets with dipole-dipole interactions near the line of second-order phase transitions directly in three-dimensional space is investigated in terms of a field-theoretic approach. The dependences of critical exponents on the dipole-dipole interaction parameter are derived. Comparison with experimental facts is made.

  1. Thomson scattering in magnetic fields. [of white dwarf stars

    NASA Technical Reports Server (NTRS)

    Whitney, Barbara

    1989-01-01

    The equation of transfer in Thomson scattering atmospheres with magnetic fields is solved using Monte Carlo methods. Two cases, a plane parallel atmosphere with a magnetic field perpendicular to the atmosphere, and a dipole star, are investigated. The wavelength dependence of polarization from plane-parallel atmosphere is qualitatively similar to that observed in the magnetic white dwarf Grw+70 deg 8247, and the field strength determined by the calculation, 320 MG, is quantitatively similar to that determined from the line spectrum. The dipole model does not resemble the data as well as the single plane-parallel atmosphere.

  2. Classical Magnetic Dipole Moments for the Simulation of Vibrational Circular Dichroism by ab Initio Molecular Dynamics.

    PubMed

    Thomas, Martin; Kirchner, Barbara

    2016-02-01

    We present a new approach for calculating vibrational circular dichroism spectra by ab initio molecular dynamics. In the context of molecular dynamics, these spectra are given by the Fourier transform of the cross-correlation function of magnetic dipole moment and electric dipole moment. We obtain the magnetic dipole moment from the electric current density according to the classical definition. The electric current density is computed by solving a partial differential equation derived from the continuity equation and the condition that eddy currents should be absent. In combination with a radical Voronoi tessellation, this yields an individual magnetic dipole moment for each molecule in a bulk phase simulation. Using the chiral alcohol 2-butanol as an example, we show that experimental spectra are reproduced very well. Our approach requires knowing only the electron density in each simulation step, and it is not restricted to any particular electronic structure method. PMID:26771403

  3. Ground State of Magnetic Dipoles on a Two-Dimensional Lattice: Structural Phases in Complex Plasmas

    SciTech Connect

    Feldmann, J. D.; Kalman, G. J.; Hartmann, P.; Rosenberg, M.

    2008-02-29

    We study analytically and by molecular dynamics simulations the ground state configuration of a system of magnetic dipoles fixed on a two-dimensional lattice. We find different phases, in close agreement with previous results. Building on this result and on the minimum energy requirement we determine the equilibrium lattice configuration, the magnetic order (ferromagnetic versus antiferromagnetic), and the magnetic polarization direction of a system of charged mesoscopic particles with magnetic dipole moments, in the domain where the strong electrostatic coupling leads to a crystalline ground state. Orders of magnitudes of the parameters of the system relevant to possible future dusty plasma experiments are discussed.

  4. Cryostat design for the superconducting super collider 50mm aperture dipole magnet

    SciTech Connect

    Nicol, T.H. ); Tsavalas, Y.P. )

    1991-03-01

    The cryostat of an SSC dipole magnet consists of all magnet components except the cold mass assembly. It serves to support the cold mass accurately and reliably within the vacuum vessel, provide all required cryogenic piping, and to insulate the cold mass from heat radiated and conducted from the environment. It must function reliably during storage, shipping and handling, normal magnet operation, quenches, and seismic excitations and must be manufacturable at low cost. This paper describes the design of the current SSC collider dipole magnet cryostat and includes discussions on the thermal, structural, and dynamic considerations involved in the development of each of the major systems.

  5. Measurements of passive correction of magnetization higher multipoles in one meter long dipoles

    SciTech Connect

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

    1990-09-01

    The use of passive superconductor to correct the magnetization sextupole and decapole in SSC dipoles appears to be promising. This paper presents the results of a series of experiments of passive superconductor correctors in one meter long dipole magnets. Reduction of the magnetization sextupole by a factor of five to ten has been achieved using the passive superconductor correctors. The magnetization decapole was also reduced. The passive superconductor correctors reduced the sextupole temperature sensitivity by an order of magnitude. Flux creep decay was partially compensated for by the correctors. 13 refs., 7 figs.

  6. Magnetic Field Measurements near Mars.

    PubMed

    Smith, E J; Davis, L; Coleman, P J; Jones, D E

    1965-09-10

    During the encounter between Mariner IV and Mars on 14-15 July, no magnetic effect that could be definitely associated with the planet was evident in the magnetometer data. This observation implies that the Martian magnetic dipole moment is, at most, 3 x 10(-4) times that of the earth.

  7. Effect of a magnetic field on sonoluminescence.

    PubMed

    Yasui, K

    1999-08-01

    The effect of a magnetic field on single-bubble sonoluminescence in water reported experimentally by Young, Schmiedel, and Kang [Phys. Rev. Lett. 77, 4816 (1996)] is studied theoretically. It is suggested that bubble dynamics is affected by the magnetic field because moving water molecules of the liquid suffer torque due to the Lorentz force acting on their electrical dipole moment, which results in the transformation of some of the kinetic energy into heat. It is shown that the magnetic field acts as if the ambient pressure of the liquid were increased. It is suggested that the effect increases as the amount of the liquid water increases. It is predicted that nonpolar liquid such as dodecane exhibits no effect of the magnetic field. PMID:11969959

  8. Evolution of calculations of the virtual dipole moment of the Earth for reconstructing the oceanic inversion magnetic layer's parameters

    NASA Astrophysics Data System (ADS)

    Schreider, A. A.; Ignatova, A. A.; Schreider, Al. A.; Sajneva, A. E.; Varga, P.; Denis, C.

    2016-05-01

    The VDM (virtual dipole moment) is one of the most significant characteristics describing the behavior of the time evolution of the terrestrial magnetic field. However, we have revealed that the formulas with which VDM calculations are performed often do not coincide with each other in various literature sources. Hence, results are obtained from these calculations that cannot be identical. Their correctness is verified by comparing the dimension and obtained results with the known value of the VDM for our time.

  9. SCALING LAW FOR THE IMPACT OF MAGNET FRINGE FIELDS.

    SciTech Connect

    WEI,J.; PAPAPHILIPPOU,Y.; TALMAN,R.

    2000-06-30

    A general scaling law can be derived for the relative momentum deflection produced on a particle beam by fringe fields, to leading order. The formalism is applied to two concrete examples, for magnets having dipole and quadrupole symmetry. During recent years, the impact of magnet fringe fields is becoming increasingly important for rings of relatively small circumference but large acceptance. A few years ago, following some heuristic arguments, a scaling law was proposed [1], for the relative deflection of particles passing through a magnet fringe-field. In fact, after appropriate expansion of the magnetic fields in Cartesian coordinates, which generalizes the expansions of Steffen [2], one can show that this scaling law is true for any multipole magnet, at leading order in the transverse coefficients [3]. This paper intends to provide the scaling law to estimate the impact of fringe fields in the special cases of magnets with dipole and quadrupole symmetry.

  10. Fast electromagnetic modeling in cylindrically layered media excited by eccentred magnetic dipole

    NASA Astrophysics Data System (ADS)

    Nikitenko, Marina; Itskovich, Gregory B.; Seryakov, Alexander

    2016-06-01

    We developed a fast algorithm to calculate a response of cylindrically layered media excited by the vertical magnetic dipole eccentred with respect to the axis of symmetry. The algorithm calculates response in the range of frequencies typical for induction and dielectric logging. The media conductivity and dielectric constant are described by piecewise-constant functions. The corresponding boundary value problem is solved by method of separation of variables. Fourier transform is applied to Maxwell equations and boundary conditions to express field components through Fourier transforms of vertical components of an electrical and magnetic field. In addition, an expansion of vertical components into an infinite series with respect to angular harmonics is used to reduce the original problem to a series of 1-D problems that only depend on the radial coordinate. The solution to each 1-D radial problem for the angular harmonics is presented as a linear combination of modified Bessel functions. Finally, inverse Fourier transformation is applied to the angular harmonics of vertical components to derive electrical and magnetic field of the original boundary value problem. We provide detailed discussion on the elements that are critical for the numerical implementation of the algorithm: a proper normalization, convergence, and integration. Specifically, we show how to perform integration in the complex plane by avoiding intersection of the integration pass with the cuts located on the Riemann surface. Numerical results show the usefulness of the algorithm for solving inverse problems and for studying the effect of eccentricity in induction and dielectric logging.

  11. ARTEMIS Low Altitude Magnetic Field Measurements

    NASA Astrophysics Data System (ADS)

    Glassmeier, Karl-Heinz; Constantinescu, Dragos; Auster, Hans-Ulrich

    2016-10-01

    Since 2011, two spacecraft of the five THEMIS mission spacecraft are in orbit around the Moon. These two ARTEMIS probes provide for very interesting observations of plasma physical properties of the lunar environment. In particular, the very low periselene of the ARTEMIS probes allows for the detection of crustal magnetic features of our terrestrial companion. Repeated low passes over the same region are used to confirm the crustal origin of the measured magnetic field variations. Using a model for the decay of the magnetic field intensity and measurements at several altitudes, we estimate the magnetic moment and the depth of the equivalent dipole. Some of these magnetic anomalies are strong enough to produce upstream waves due to the interaction with the solar wind with the anomaly driven mini-magnetospheres.

  12. Spontaneous Demagnetization of a Dipolar Spinor Bose Gas in an Ultralow Magnetic Field

    SciTech Connect

    Pasquiou, B.; Marechal, E.; Bismut, G.; Pedri, P.; Vernac, L.; Gorceix, O.; Laburthe-Tolra, B.

    2011-06-24

    We study the spinor properties of S=3 {sup 52}Cr condensates, in which dipole-dipole interactions allow changes in magnetization. We observe a demagnetization of the Bose-Einstein condensate (BEC) when the magnetic field is quenched below a critical value corresponding to a phase transition between a ferromagnetic and a nonpolarized ground state, which occurs when spin-dependent contact interactions overwhelm the linear Zeeman effect. The critical field is increased when the density is raised by loading the BEC in a deep 2D optical lattice. The magnetization dynamics is set by dipole-dipole interactions.

  13. Venus internal magnetic field and its interaction with the interplanetary magnetic field

    NASA Technical Reports Server (NTRS)

    Knudsen, W. C.

    1992-01-01

    In a previous study, Knudsen et al. suggested that Venus has a weak internal magnetic dipole field of the order of 7 x 10 + 20 G cm(exp -3) that is manifested in the form of magnetic flux tubes threading the ionospheric holes in the Venus nightside ionosphere. They pointed out that any internal field of Venus, dipole or multipole, would be weakened in the subsolar region and concentrated in the antisolar region of the planet by the supersonic transterminator convection of the dayside ionosphere into the nightside hemisphere. The inferred magnitude of the dipole field does not violate the upper limit for an internal magnetic field established by the Pioneer Venus magnetometer experiment. The most compelling objection to the model suggested by Knudsen et al. has been the fact that it does not explain the observed interplanetary magnetic field (IMF) control of the polarity of the ionospheric hole flux tubes. In this presentation I suggest that a magnetic reconnection process analogous to that occurring at earth is occurring at Venus between the IMF and a weak internal dipole field. At Venus in the subsolar region, the reconnection occurs within the ionosphere. At Earth it occurs at the magnetopause. Reconnection will occur only when the IMF has an appropriate orientation relative to that of the weak internal field. Thus, reconnection provides a process for the IMF to control the flux tube polarity. The reconnection in the subsolar region takes place in the ionosphere as the barrier magnetic field is transported downward into the lower ionosphere by downward convection of ionospheric plasma and approaches the oppositely directed internal magnetic field that is diffusing upward. The reconnected flux tubes are then transported anti-Sunward by the anti-Sunward convecting ionospheric plasma as well as by the anti-Sunward-flowing solar wind. Reconnection will also occur in the Venus magnetic tail region, somewhat analogously to the reconnection that occurs in the

  14. 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

  15. The symmetry properties of planetary magnetic fields

    SciTech Connect

    Raedler, K.H. ); Ness, N.F. )

    1990-03-01

    This paper provides a comparative study of the geometrical structures of the magnetic fields of Earth, Jupiter, Saturn, and Uranus, starting from the traditional multipolar representations of these fields. For Earth, Jupiter, and Saturn the centered dipole, quadrupole, and octupole contributions are included, while at Uranus, only the dipole and quadrupole contributoins are considered. The magnetic fields are analyzed by decomposing them into those parts which have simple symmetry properties with respect to the rotation axis and the equatorial plane. It is found that there are a number of common features of the magnetic fields of Earth and Jupiter. Compared to Earth and Jupiter, the Saturnian field exhibits not only a high degree of symmetry about the rotation axis, by now rather well known, but also a high degree of antisymmetry about the equatorial plane. The Uranian field shows strong deviations from both such symmetries. Nevertheless, there remain features common to all four planets. The implications of these results for dynamo models are discussed. With a vgiew to Cowling's theorem the symmetry of the fields is investigated with respect to not only the rotation axis but also to other axes intersecting the plaentary center. Surprisingly, the high degree of asymmetry of the Uranian field that is observed with respect to the rotation axis reduces considerably to being compare to that for Earth or Jupiter when the appropriate axis is employed.

  16. 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.

  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 measurement system for harmonic analysis of LBL SSC (Superconducting Super Collider) model dipoles and quadrupoles

    SciTech Connect

    Green, M.I.; Barale, P.J.; Gilbert, W.S.; Hassenzahl, W.V.; Nelson, D.H.; Taylor, C.E.; Travis, N.J.; Van Dyke, D.A.

    1987-09-01

    Specialized hardware and software have been developed to facilitate harmonic error analysis measurements of one-meter-long Superconducting Super Collider (SSC) model dipole and quadrupole magnets. Cold bore measurements feature cryogenic search-coil arrays with high bucking ratios that also have sufficient sensitivity to make room-temperature measurements at the low magnet currents of approx.10 A. Three sets of search coils allow measurements of the center, either end, and/or the axially integrated field. Signals from the search coils are digitally integrated by means of a voltage-to-frequency converter feeding an up-down counter. The data are drift corrected, Fourier analyzed, converted to physical quantities, and printed and plotted. A cycle of measurements including data acquisition, processing, and the generation of tabular and graphic output requires 80 seconds. The vast amount of data generated (several hundred measurement cycles for each magnet) has led to the development of postprocessing programs and procedures. Spreadsheets allow easy manipulation and comparison of results within a test series and between magnets. 8 refs., 4 figs., 1 tab.

  19. Test Results of HD1b, an upgraded 16 Tesla Nb3Sn DipoleMagnet

    SciTech Connect

    Lietzke, A.F.; Bartlett, S.E.; Bish, P.; Caspi, S.; Dietderich,D.; Ferracin, P.; Gourlay, S.; Hafalia, A.R.; Hannaford, C.R.; Higley,H.; Lau, W.; Liggins, N.; Mattafirri, S.; Nyman, M.; Sabbi, G.; Scanlan,R.; Swanson, J.

    2005-04-16

    The Superconducting Magnet Group at Lawrence Berkeley National Laboratory has been developing high-field, brittle-superconductor, accelerator magnet technology, in which the conductor's support system can significantly impact conductor performance (as well as magnet training). A recent H-dipole coil test (HD1) achieved a peak bore-field of 16 Tesla, using two, flat-racetrack, double-layer Nb{sub 3}Sn coils. However, its 4.5 K training was slow, with an erratic plateau at {approx}92% of its un-degraded ''short-sample'' expectation ({approx}16.6 T). Quench-origins correlated with regions where low conductor pre-stress had been expected (3-D FEM predictions and variations in 300 K coil-size). The coils were re-assembled with minor coil-support changes and re-tested as ''HD1b'', with a 185 MPa average pre-stress (30 MPa higher than HD1, with a 15-20 MPa pole-turn margin expected at 17 T). Training started higher (15.1 T), and quickly reached a stable, negligibly higher plateau at 16 T. After a thermal cycle, training started at 15.4 T, but peaked at 15.8 T, on the third attempt, before degrading to a 15.7 T plateau. The temperature dependence of this plateau was explored in a sub-atmospheric LHe bath to 3.0 K. Magnet performance data for both thermal cycles is presented and discussed, along with issues for future high-field accelerator magnet development.

  20. Dipole Field Effects on Ion Ejections from a Paul Ion Trap

    NASA Technical Reports Server (NTRS)

    MacAskill, J. A.; Chutjian, A.

    2011-01-01

    Attempts at improving the quality of mass spectra obtained from a Paul trap mass spectrometer prompted an investigation of the effects of additional fields to supplement the primary rf quadrupole trapping field. Reported here are the results of the first in a series of tests that focuses on the application of a single dipole field to augment the trapping and subsequent ejections of ions stored within a Paul trap. Measurements are presented for a fixed quadrupole frequency with varying dipole frequencies. The presence of the dipole field during the quadrupole trapping phase causes ion ejections of single m/z species at discrete dipole frequencies. During the mass analysis phase, the varying dipole frequency produces a complex set of resonant structures that impact ejection time (mass range), as well as mass spectral peak intensity and width

  1. Concentric transmon qubit featuring fast tunability and an anisotropic magnetic dipole moment

    NASA Astrophysics Data System (ADS)

    Braumüller, Jochen; Sandberg, Martin; Vissers, Michael R.; Schneider, Andre; Schlör, Steffen; Grünhaupt, Lukas; Rotzinger, Hannes; Marthaler, Michael; Lukashenko, Alexander; Dieter, Amadeus; Ustinov, Alexey V.; Weides, Martin; Pappas, David P.

    2016-01-01

    We present a planar qubit design based on a superconducting circuit that we call concentric transmon. While employing a straightforward fabrication process using Al evaporation and lift-off lithography, we observe qubit lifetimes and coherence times in the order of 10 μ s . We systematically characterize loss channels such as incoherent dielectric loss, Purcell decay and radiative losses. The implementation of a gradiometric SQUID loop allows for a fast tuning of the qubit transition frequency and therefore for full tomographic control of the quantum circuit. Due to the large loop size, the presented qubit architecture features a strongly increased magnetic dipole moment as compared to conventional transmon designs. This renders the concentric transmon a promising candidate to establish a site-selective passive direct Z ̂ coupling between neighboring qubits, being a pending quest in the field of quantum simulation.

  2. 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.

  3. Strong CP violation in external magnetic fields

    SciTech Connect

    Millo, R.; Faccioli, P.

    2008-03-15

    We study the response of the QCD vacuum to an external magnetic field, in the presence of strong CP violation. Using chiral perturbation theory and large N{sub c} expansion, we show that the external field would polarize quantum fluctuations and induce an electric dipole moment of the vacuum along the direction of the magnetic field. We estimate the magnitude of this effect in different physical scenarios. In particular, we find that the polarization induced by the magnetic field of a magnetar could accelerate electric charges up to energies of the order {approx}{theta}10{sup 3} TeV. We also suggest a connection with the possible existence of ''hot-spots'' on the surface of neutron stars.

  4. Braking index of isolated pulsars. II. A novel two-dipole model of pulsar magnetism

    NASA Astrophysics Data System (ADS)

    Hamil, O.; Stone, N. J.; Stone, J. R.

    2016-09-01

    The magnetic dipole radiation model is currently the best approach we have to explain pulsar radiation. However, a most characteristic parameter of the observed radiation, the braking index nobs , shows deviations for all the eight best studied isolated pulsars, from the simple model prediction ndip=3 . The index depends upon the rotational frequency and its first and second time derivatives but also on the assumption that the magnetic dipole moment and inclination angle and the moment of inertia of the pulsar are constant in time. In a recent paper [Phys. Rev. D 91, 063007 (2015)], we showed conclusively that changes in the moment of inertia with frequency alone cannot explain the observed braking indices. Possible observational evidence for the magnetic dipole moment migrating away from the rotational axis at a rate α ˙ ˜0.6 ° per 100 years over the lifetime of the Crab pulsar has been recently suggested by Lyne et al. In this paper, we explore the magnetic dipole radiation model with constant moment of inertia and magnetic dipole moment but variable inclination angle α . We first discuss the effect of the variation of α on the observed braking indices and show they all can be understood. However, no explanation for the origin of the change in α is provided. After discussion of the possible source(s) of magnetism in pulsars, we propose a simple mechanism for the change in α based on a toy model in which the magnetic structure in pulsars consists of two interacting dipoles. We show that such a system can explain the Crab observation and the measured braking indices.

  5. Changes in earth's dipole.

    PubMed

    Olson, Peter; Amit, Hagay

    2006-11-01

    The dipole moment of Earth's magnetic field has decreased by nearly 9% over the past 150 years and by about 30% over the past 2,000 years according to archeomagnetic measurements. Here, we explore the causes and the implications of this rapid change. Maps of the geomagnetic field on the core-mantle boundary derived from ground-based and satellite measurements reveal that most of the present episode of dipole moment decrease originates in the southern hemisphere. Weakening and equatorward advection of normal polarity magnetic field by the core flow, combined with proliferation and growth of regions where the magnetic polarity is reversed, are reducing the dipole moment on the core-mantle boundary. Growth of these reversed flux regions has occurred over the past century or longer and is associated with the expansion of the South Atlantic Anomaly, a low-intensity region in the geomagnetic field that presents a radiation hazard at satellite altitudes. We address the speculation that the present episode of dipole moment decrease is a precursor to the next geomagnetic polarity reversal. The paleomagnetic record contains a broad spectrum of dipole moment fluctuations with polarity reversals typically occurring during dipole moment lows. However, the dipole moment is stronger today than its long time average, indicating that polarity reversal is not likely unless the current episode of moment decrease continues for a thousand years or more. PMID:16915369

  6. Maximum field capability of Energy-Saver superconducting magnets

    SciTech Connect

    Turkot, F.; Cooper, W.E.; Hanft, R.; McInturff, A.

    1983-03-01

    At an energy of 1 TeV, the superconducting cable in the Energy Saver dipole magnets will be operating at approx. 96% of its nominal short sample limit; the corresponding number in the quadrupole magnets is 81%. All magnets for the Saver are individually tested for maximum current capability under two modes of operation; some 900 dipoles and 275 quadrupoles have now been measured. The dipole winding is composed of four individually wound coils. In general, the cable in the four coils comes from four different reels of cable. As part of magnet fabrication quality control, a short piece of cable from both ends of each reel has its critical current (rho = 1 x 10/sup -12/'..cap omega..-cm) measured at 5T and 4.3/sup 0/K. We present the statistical results of the maximum field tests on Saver magnets and explore the correlation with cable critical current.

  7. Coronal Magnetic Field

    NASA Astrophysics Data System (ADS)

    Lin, Haosheng

    2007-05-01

    Centuries after the birth of modern solar astronomy, the Sun's corona still keeps many of its secrets: How is it heated to a million-degree temperature? How does it harbor the cool and dense prominence gas amid the tenuous and hot atmosphere? How does it drive the energetic events that eject particles into interplanetary space with speed exceeding 1% of the speed of light? We have greatly improved our knowledge of the solar corona with decades of space X-ray and EUV coronal observations, and many theories and models were put forward to address these problems. In our current understanding, magnetic fields are undoubtedly the most important fields in the corona, shaping its structure and driving its dynamics. It is clear that the resolution of these important questions all hinge on a better understanding of the organization, evolution, and interaction of the coronal magnetic field. However, as the direct measurement of coronal magnetic field is a very challenging observational problem, most of our theories and models were not experimentally verified. Nevertheless, we have finally overcome the experimental difficulties and can now directly measure the coronal magnetic field with great accuracy. This new capability can now be used to study the static magnetic structure of the corona, and offers hope that we will, in the near future, be able to directly observe the evolution of the coronal magnetic field of energetic solar events. More importantly, it finally allows us to conduct vigorous observational tests of our theories and models. In this lecture, I will review current research activities related to the observation, interpretation, and modeling of the coronal magnetic field, and discuss how they can help us resolve some of the long standing mysteries of the solar corona.

  8. Magnetic Field Solver

    NASA Technical Reports Server (NTRS)

    Ilin, Andrew V.

    2006-01-01

    The Magnetic Field Solver computer program calculates the magnetic field generated by a group of collinear, cylindrical axisymmetric electromagnet coils. Given the current flowing in, and the number of turns, axial position, and axial and radial dimensions of each coil, the program calculates matrix coefficients for a finite-difference system of equations that approximates a two-dimensional partial differential equation for the magnetic potential contributed by the coil. The program iteratively solves these finite-difference equations by use of the modified incomplete Cholesky preconditioned-conjugate-gradient method. The total magnetic potential as a function of axial (z) and radial (r) position is then calculated as a sum of the magnetic potentials of the individual coils, using a high-accuracy interpolation scheme. Then the r and z components of the magnetic field as functions of r and z are calculated from the total magnetic potential by use of a high-accuracy finite-difference scheme. Notably, for the finite-difference calculations, the program generates nonuniform two-dimensional computational meshes from nonuniform one-dimensional meshes. Each mesh is generated in such a way as to minimize the numerical error for a benchmark one-dimensional magnetostatic problem.

  9. Molecules in intense laser fields: Beyond the dipole approximation

    SciTech Connect

    Bandrauk, A. D.; Lu, H. Z.

    2006-01-15

    The time-dependent Schroedinger equation is solved for a Born-Oppenheimer (static nuclei) three-dimensional H{sub 2}{sup +} in super intense laser fields (I=4x10{sup 18}, 10{sup 19}, and 4x10{sup 19} W/cm{sup 2}) at wavelength {lambda}{sub L}=45 nm and 25 nm to assess the influence of nondipolar (magnetic) effects on high order harmonic generation spectra in molecules. It is found that even harmonics appear due to the magnetic field component direction perpendicular to the electric field polarization with intensities about two orders of magnitude less than the odd harmonics emitted along the electric field polarization. The even harmonics exhibit plateaus with cutoffs which exceed in intensity the odd harmonic plateaus and maximum energies predicted by semiclassical electron recollision models. Although the spectra are weak, the wavelength of the recollision electron in the maximum energy regions correspond to subatomic dimensions and the corresponding emitted photons have subnanometer wavelengths.

  10. Dynamically fluctuating electric dipole moments in fullerene-based magnets

    PubMed Central

    Kambe, Takashi; Oshima, Kokichi

    2014-01-01

    We report here the direct evidence of the existence of a permanent electric dipole moment in both crystal phases of a fullerene-based magnet—the ferromagnetic α-phase and the antiferromagnetic α′-phase of tetra-kis-(dimethylamino)-ethylene-C60 (TDAE-C60)—as determined by dielectric measurements. We propose that the permanent electric dipole originates from the pairing of a TDAE molecule with surrounding C60 molecules. The two polymorphs exhibit clear differences in their dielectric responses at room temperature and during the freezing process with dynamically fluctuating electric dipole moments, although no difference in their room-temperature structures has been previously observed. This result implies that two polymorphs have different local environment around the molecules. In particular, the ferromagnetism of the α-phase is founded on the homogeneous molecule displacement and orientational ordering. The formation of the different phases with respect to the different rotational states in the Jahn–Teller distorted C60s is also discussed. PMID:25236361

  11. Whistler modes with wave magnetic fields exceeding the ambient field.

    PubMed

    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.

  12. Kinetic and thermodynamic properties of a convecting plasma in a two-dimensional dipole field

    NASA Technical Reports Server (NTRS)

    Huang, T. S.; Birmingham, T. J.

    1994-01-01

    Charged particle guiding center motion is considered in the magnetic field of a two-dimensional ('line') dipole on which is superimposed a small, static, perpendicular electric field. The parallel equation of motion is that of a simple harmonic oscillator for cos theta, the cosine of magnetic colatitude theta. Equations for the perpendicular electric and magnetic drifts are derived as well as their bounce-averaged forms. The latter are solved to yield a bounce-averaged guiding center trajectory, which is the same as that obtained from conversation of magnetic moment mu, longitudinal invariant J, and total (kinetic plus electrostatic) energy K. The algebraic simplicity of the trajectory equations is also manifest in the forms of the invariants. An interesting result is that guiding centers drift in such a way that they preserve the values of their equatorial pitch angles and (equivalently) mirror latitudes. The most general Maxwellian form of the equilibrium one-particle distribution function f is constructed from the invariants, and spatially varying density and pressure moments, parallel and perpendicular to the magnetic field, are identified. Much of the paper deals with the more restricted problem in which f is specified as a bi-Maxwellian over a straight line of finite length in the equatorial plane of the dipole and perpendicular to field lines. This might be thought of as specifying a cross-tail ion injection source; our formalism then describes the subsequent spatial development. The distribution away from the source is a scaled bi-Maxwellian but one that is cut off at large and small kinetic energies, which depend on position. Density and pressure components are reduced from the values they would have if the total content of individual flux tubes convected intact. The equatorial and meridional variations of density and pressure components are examined and compared systematically for the isotropic and highly anisotropic situations. There appears to be little

  13. NMR absolute shielding scale and nuclear magnetic dipole moment of (207)Pb.

    PubMed

    Adrjan, Bożena; Makulski, Włodzimierz; Jackowski, Karol; Demissie, Taye B; Ruud, Kenneth; Antušek, Andrej; Jaszuński, Michał

    2016-06-28

    An absolute shielding scale is proposed for (207)Pb nuclear magnetic resonance (NMR) spectroscopy. It is based on ab initio calculations performed on an isolated tetramethyllead Pb(CH3)4 molecule and the assignment of the experimental resonance frequency from the gas-phase NMR spectra of Pb(CH3)4, extrapolated to zero density of the buffer gas to obtain the result for an isolated molecule. The computed (207)Pb shielding constant is 10 790 ppm for the isolated molecule, leading to a shielding of 10799.7 ppm for liquid Pb(CH3)4 which is the accepted reference standard for (207)Pb NMR spectra. The new experimental and theoretical data are used to determine μ((207)Pb), the nuclear magnetic dipole moment of (207)Pb, by applying the standard relationship between NMR frequencies, shielding constants and nuclear moments of two nuclei in the same external magnetic field. Using the gas-phase (207)Pb and (reference) proton results and the theoretical value of the Pb shielding in Pb(CH3)4, we find μ((207)Pb) = 0.59064 μN. The analysis of new experimental and theoretical data obtained for the Pb(2+) ion in water solutions provides similar values of μ((207)Pb), in the range of 0.59000-0.59131 μN. PMID:27265668

  14. Suppression of Secondary Electron Emission using Triangular Grooved Surface in the ILC Dipole and Wiggler Magnets

    SciTech Connect

    Wang, L.; Bane, K.; Chen, C.; Himel, T.; Munro, M.; Pivi, M.; Raubenheimer, T.; Stupakov, G.; /SLAC

    2007-07-06

    The development of an electron cloud in the vacuum chambers of high intensity positron and proton storage rings may limit machine performance. The suppression of electrons in a magnet is a challenge for the positron damping ring of the International Linear Collider (ILC) as well as the Large Hadron Collider. Simulation show that grooved surfaces can significantly reduce the electron yield in a magnet. Some of the secondary electrons emitted from the grooved surface return to the surface within a few gyrations, resulting in a low effective secondary electron yield (SEY) of below 1.0 A triangular surface is an effective, technologically attractive mitigation with a low SEY and a weak dependence on the scale of the corrugations and the external magnetic field. A chamber with triangular grooved surface is proposed for the dipole and wiggler sections of the ILC and will be tested in KEKB in 2007. The strategy of electron cloud control in ILC and the optimization of the grooved chamber such as the SEY, impedance as well as the manufacturing of the chamber, are also discussed.

  15. Electrically silent magnetic fields.

    PubMed Central

    Roth, B J; Wikswo, J P

    1986-01-01

    There has been a significant controversy over the past decade regarding the relative information content of bioelectric and biomagnetic signals. In this paper we present a new, theoretical example of an electrically-silent magnetic field, based on a bidomain model of a cylindrical strand of tissue generalized to include off-diagonal components in the conductivity tensors. The physical interpretation of the off-diagonal components is explained, and analytic expressions for the electrical potential and the magnetic field are found. These expressions show that information not obtainable from electrical potential measurements can be obtained from measurements of the magnetic field in systems with conductivity tensors more complicated than those previously examined. PMID:3779008

  16. Ultrafast time domain demonstration of bulk magnetization precession at zero magnetic field ferromagnetic resonance induced by terahertz magnetic field.

    PubMed

    Nakajima, M; Namai, A; Ohkoshi, S; Suemoto, T

    2010-08-16

    We report the first observation of sub-terahertz bulk-magnetization precession, using terahertz time-domain spectroscopy. The magnetization precession in gallium-substituted epsilon-iron oxide nano-ferromagnets under zero magnetic field is induced by the impulsive magnetic field of the THz wave through the gyromagnetic effect. Just at the resonance frequency, the linear to circular polarized wave conversion is realized. This is understood as the free induction decay signal radiated from a rotating magnetic dipole corresponding to the natural resonance. Furthermore, this demonstration reveals that the series of gallium-substituted epsilon-iron oxide nano-ferromagnets is very prospective for magneto-optic devices, which work at room temperature without external magnetic field, in next-generation wireless communication.

  17. Excitation of the centrifugally driven interchange instability in a plasma confined by a magnetic dipole

    SciTech Connect

    Levitt, B.; Maslovsky, D.; Mauel, M.E.; Waksman, J.

    2005-05-15

    The centrifugally driven electrostatic interchange instability is excited for the first time in a laboratory magnetoplasma. The plasma is confined by a dipole magnetic field, and the instability is excited when an equatorial mesh is biased to induce a radial current that creates rapid axisymmetric plasma rotation. The observed instabilities appear quasicoherent in the lab frame of reference; they have global radial mode structures and low azimuthal mode numbers, and they are modified by the presence of energetic, magnetically confined electrons. The mode structure is measured using a multiprobe correlation technique as well as a novel 96-point polar imaging diagnostic which measures particle flux along field lines that map to the pole. Interchange instabilities caused by hot electron pressure are simultaneously observed at the hot electron drift frequency. Adjusting the hot electron fraction {alpha} modifies the stability as well as the structures of the centrifugally driven modes. In the presence of larger fractions of energetic electrons, m=1 is observed to be the dominant mode. For faster rotating plasmas containing fewer energetic electrons, m=2 dominates. Results from a self-consistent nonlinear simulation reproduce the measured mode structures in both regimes. The low azimuthal mode numbers seen in the experiment and simulation can also be interpreted with a local, linear dispersion relation of the electrostatic interchange instability. Drift resonant hot electrons give the instability a real frequency, inducing stabilizing ion polarization currents that preferentially suppress high-m modes.

  18. Fabrication and Test Results of a Nb3Sn Superconducting Racetrack Dipole Magnet

    SciTech Connect

    Chow, K.; Dietderich, D.R.; Gourlay, S.A.; Gupta, R.; Harnden, W.; Lietzke, A. F.; McInturff, A.D.; Millos, G.A.; Morrison, L.; Morrison, M.; Scanlan, R.M.

    2000-02-06

    A 'proof-of-principle' Nb{sub 3}Sn superconducting dual-bore dipole magnet was built from racetrack coils, as a first step in a program to develop an economical, 15 Tesla, accelerator-quality magnet. The mechanical design and magnet fabrication procedures are discussed. No training was required to achieve temperature-dependent plateau currents, despite several thermal cycles that involved partial magnet disassembly and substantial pre-load variations. Subsequent magnets are expected to approach 15 Tesla with substantially improved conductor.

  19. 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

  20. Design of a 10-T superconducting dipole magnet using niobium-tin conductor

    SciTech Connect

    Taylor, C.; Meuser, R.; Caspi, S.; Gilbert, W.; Hassenzahl, W.; Peters, C.; Schafer, R.; Wolgast, R.

    1982-11-01

    In order to minimize the size and cost of conventional facilities - land, tunneling, shielding, cryogenic and vacuum system - the dipole magnets for the next generation of particle accelerators must produce as strong a magnetic field as possible. Ten tesla seems to be a reasonable goal, and can be attained by using either niobium-tin conductor at 4.2 K or niobium-titanium at 1.8 K. The beam diameter in a multi-TeV accelerator, can in principle, be quite small, say 20 mm, depending on the design of the injection and extraction systems, and on beam-cooling technology. Magnet cost is strongly dependent on bore diameter, so there is a strong incentive to minimize that. We believe that a 40-mm bore diameter - about 60-mm winding inside diameter is feasible and is a reasonable goal for initial research and development. For such a high field and small bore, there is an incentive to achieve a high overall current density in order to minimize the amount of superconductor. Our design is based on an overall current density of 400 A/sq mm. LBL has undertaken the development of a magnet using niobium-tin conductor intended to meet the above specifications. The conductor is a Rutherford-type cable consisting of twelve strands of 1.71-mm-dia wire. Dimensions of the uninsulated cable are 11.0 x 3.0 mm. The configuration chosen consists of flat race-track layers - four per pole - with the ends bent up and down to clear the bore. Two coils are wound from a single piece of cable with a cross-over at the inside: the familiar double pancake arrangement.

  1. Strongly magnetized antihydrogen and its field ionization.

    PubMed

    Vrinceanu, D; Granger, B E; Parrott, R; Sadeghpour, H R; Cederbaum, L; Mody, A; Tan, J; Gabrielse, G

    2004-04-01

    Internal orbits of experimentally analyzed antihydrogen (H) atoms depend as much on an external magnetic field as on the Coulomb force. A circular "guiding center atom" model is used to understand their field ionization. This useful model, assumed in the theory of three-body H recombination so far, ignores the important coupling between internal and center-of-mass motion. A conserved pseudomomentum, effective potential, saddle point analysis, and numerical simulation show where the simple model is valid and classify the features of the general case, including "giant dipole states."

  2. Sodium in a strong magnetic field

    NASA Astrophysics Data System (ADS)

    González-Férez, R.; Schmelcher, P.

    2003-05-01

    We investigate the effects of a magnetic field with low to intermediate strength on several spectroscopic properties of the sodium atom. A model potential is used to describe the core of sodium, reducing the study of the system to an effective one-particle problem. All states with principal quantum numbers n = 3, 4, 5, 6 and 7 are studied and analysed. A grid of twenty values for the field strength in the complete regime B = 0 - 0.02 a.u. is employed. Ionisation energies, transition wavelengths and their dipole oscillator strengths are presented.

  3. How do galaxies get their magnetic fields?

    NASA Astrophysics Data System (ADS)

    Beck, Alexander M.

    2016-06-01

    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 μG 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

  4. 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.

  5. Experimental demonstration of acoustic wave induced magnetization switching in dipole coupled magnetostrictive nanomagnets for ultralow power computing

    NASA Astrophysics Data System (ADS)

    Sampath, Vimal; D'Souza, Noel; Atkinson, Gary M.; Bandyopadhyay, Supriyo; Atulasimha, Jayasimha

    2016-09-01

    Dipole-coupled cobalt nanomagnet pairs of elliptical shape (with their major axes parallel) are delineated on 128° Y-cut lithium niobate. Each pair is initially magnetized along the major axis with a magnetic field forming the (↑↑) state. When an acoustic wave (AW) is launched in the substrate from interdigitated electrodes, the softer nanomagnet in the pair flips to produce the (↑↓) state since the AW modulates the stress anisotropy. This executes the logical NOT operation because the output bit encoded in the magnetization state of the softer nanomagnet becomes the logic complement of the input bit encoded in the magnetization of the harder one. The AW acts as a clock to trigger the NOT operation and the energy dissipated is a few tens of aJ. Such AW clocking can be utilized to flip nanomagnets in a chain sequentially to steer logic bits unidirectionally along a nanomagnetic logic wire with miniscule energy dissipation.

  6. Heliomagnetic latitude dependence of the heliospheric magnetic field

    NASA Astrophysics Data System (ADS)

    Burton, M. E.; Smith, E. J.; Balogh, A.; Murphy, N.

    1996-07-01

    ICE and IMP-8 magnetic field data from 1984-1988 have been analyzed in a magnetic coordinate system defined by the orientation of the solar magnetic dipole. The heliomagnetic latitude dependence of the radial component of the magnetic field (Br) has then been investigated in a wide range of magnetic latitudes above and below the heliospheric current sheet (HCS). Br reverses sign abruptly across the current sheet, consistent with the solar magnetic field models of Pneuman and Kopp [1971] and Wolfson [1985] but inconsistent with the source surface models [Hoeksema, 1986]. No evidence is found for an asymmetry in the magnetic field suggested by earlier studies of interplanetary magnetic field data [Luhmann, 1987, Burton, 1990]. A slight (~.03 nT per degree) latitude gradient has been found which is consistent with the MHD model of Pneuman and Kopp and the recent model of Zhao and Hoeksema [1995].

  7. Magnetic fields of Jupiter and Saturn

    SciTech Connect

    Ness, N.F.

    1981-01-01

    The magnetic fields of Jupiter and Saturn and the characteristics of their magnetospheres, formed by interaction with the solar wind, are discussed. The origins of both magnetic fields are associated with a dynamo process deep in the planetary interior. The Jovian magnetosphere is analogous to that of a pulsar magnetosphere: a massive central body with a rapid rotation and an associated intense magnetic field. Its most distinctive feature is its magnetodisk of concentrated plasma and particle flux, and reduced magnetic field intensity. The magnetopause near the subsolar point has been observed at radial distances ranging over 50 to 100 Jovian radii, implying a relatively compressible obstacle to solar wind flow. The composition of an embedded current sheet within the magnetic tail is believed to be influenced by volcanic eruptions and emissions from Io. Spectral troughs of the Jovian radiation belts have been interpreted as possible ring particles. The Saturnian magnetosphere appears to be more like the earth in its topology. It is mainly characterized by a dipole axis parallel to the rotational axis of the planet and a magnetic field intensity much less than expected.

  8. The magnetic fields of Jupiter and Saturn

    NASA Astrophysics Data System (ADS)

    Ness, N. F.

    The magnetic fields of Jupiter and Saturn and the characteristics of their magnetospheres, formed by interaction with the solar wind, are discussed. The origins of both magnetic fields are associated with a dynamo process deep in the planetary interior. The Jovian magnetosphere is analogous to that of a pulsar magnetosphere: a massive central body with a rapid rotation and an associated intense magnetic field. Its most distinctive feature is its magnetodisk of concentrated plasma and particle flux, and reduced magnetic field intensity. The magnetopause near the subsolar point has been observed at radial distances ranging over 50 to 100 Jovian radii, implying a relatively compressible obstacle to solar wind flow. The composition of an embedded current sheet within the magnetic tail is believed to be influenced by volcanic eruptions and emissions from Io. Spectral troughs of the Jovian radiation belts have been interpreted as possible ring particles. The Saturnian magnetosphere appears to be more like the earth in its topology. It is mainly characterized by a dipole axis parallel to the rotational axis of the planet and a magnetic field intensity much less than expected.

  9. Different Paths to Some Fundamental Physical Laws: Relativistic Polarization of a Moving Magnetic Dipole

    ERIC Educational Resources Information Center

    Kholmetskii, Alexander L.; Yarman, T.

    2010-01-01

    In this paper we consider the relativistic polarization of a moving magnetic dipole and show that this effect can be understood via the relativistic generalization of Kirchhoff's first law to a moving closed circuit with a steady current. This approach allows us to better understand the law of relativistic transformation of four-current density…

  10. The Magnetic Dipole as an Attractive Fusion Reactor

    NASA Astrophysics Data System (ADS)

    Dawson, John M.

    1997-11-01

    Stability for low β plasma confined by closed B field lines is PV^γ = C_0, P = pressure, V = flux tube volume, γ is c_p/cv = 5/3. Kesner(J. Kesner, Innovative Confinement Concepts Workshop, Mar. 3-6, 1997) proposed a levitated current ring with the plasma stabilized by this condition as an alternate fusion reactor. Such a reactor has many attractive features; at radii large compared to the ring radius, V goes like r^4; the stability condition is Pr^20/3 = C_1. If nr^4 = C_2, then interchanges keep the density constant. The temperature can drop according to Tr^8/3 = C_3. If the chamber is ten times the ring radius, the density can drop from 10^14 near the ring to 10^10 at the edge and the temperature can drop from 50 keV near the ring to 100 eV at the edge. This plasma should present no problems for a divertor. Reacting plasma near the ring will heat it, upsetting the stability relation and cause convection to carry burnt plasma out; it will cool as it expands. At the same time the convection will bring in fresh fuel from the outside which will be compressed and heated to ignition. A super conducting ring design that can float in reacting D-He^3 for 16 hours exists(J.M. Dawson, FUSION, edited by Edward Teller, Vol. 1, Magnetic Confinement, Part, Ch. 16, Academic Press, 1981).

  11. Electric and Magnetic Dipole States in ^238U

    NASA Astrophysics Data System (ADS)

    Hammond, S. L.; Adekola, A.; Angell, C. T.; Karwowski, H. J.; Howell, C. R.; Kwan, E.; Rusev, G.; Tonchev, A. P.; Tornow, W.; Kelley, J. H.

    2010-11-01

    An investigation of dipole states in ^238U is important for the fundamental understanding of its structure. Precise experimental information on the distribution of M1 and E1 transitions in ^238U has been obtained using the nuclear resonance fluorescence technique at the High-Intensity γ-ray Source at the Triangle Universities Nuclear Laboratory. Using 100% linearly-polarized, monoenergetic γ-ray beams between incident energies of 2.0 - 5.5 MeV, the spin, parity, width, and γ-strength of the ground-state deexcitations were determined. These measurements will form a unique data set that can be used for comparison with theoretical models of collective excitations in heavy, deformed nuclei. The data can also provide isotope-specific signatures to search for special nuclear materials.

  12. Field quality measurements of a 2-Tesla transmission line magnet

    SciTech Connect

    Velev, G.V.; Foster, W.; Kashikhin, V.; Mazur, P.; Oleck, A.; Piekarz, H.; Schlabach, P.; Sylvester, C.; Wake, M.; /KEK, Tsukuba

    2005-09-01

    A prototype 2-Tesla superconducting transmission line magnet for future hadron colliders was designed, built and tested at Fermilab. The 1.5 m long, combined-function gradient-dipole magnet has a vertical pole aperture of 20 mm. To measure the magnetic field quality in such a small magnet aperture, a specialized rotating coil of 15.2 mm diameter, 0.69 m long was fabricated. Using this probe, a program of magnetic field quality measurements was successfully performed. Results of the measurements are presented and discussed.

  13. Measurement of homonuclear magnetic dipole-dipole interactions in multiple 1/2-spin systems using constant-time DQ-DRENAR NMR

    NASA Astrophysics Data System (ADS)

    Ren, Jinjun; Eckert, Hellmut

    2015-11-01

    A new pulse sequence entitled DQ-DRENAR (Double-Quantum based Dipolar Recoupling Effects Nuclear Alignment Reduction) was recently described for the quantitative measurement of magnetic dipole-dipole interactions in homonuclear spin-1/2 systems involving multiple nuclei. As described in the present manuscript, the efficiency and performance of this sequence can be significantly improved, if the measurement is done in the constant-time mode. We describe both the theoretical analysis of this method and its experimental validation of a number of crystalline model compounds, considering both symmetry-based and back-to-back (BABA) DQ-coherence excitation schemes. Based on the combination of theoretical analysis and experimental results we discuss the effect of experimental parameters such as the chemical shift anisotropy (CSA), the spinning rate, and the radio frequency field inhomogeneity upon its performance. Our results indicate that constant-time (CT-) DRENAR is a method of high efficiency and accuracy for compounds with multiple homonuclear spin systems with particular promise for the analysis of stronger-coupled and short T2 spin systems.

  14. The response of longitudinal and transverse pickup coils to a misaligned magnetic dipole

    SciTech Connect

    Miller, L.L.

    1996-09-01

    The responses of magnetic pickup coils to various orientations and positions of a point dipole are considered. General solutions which describe the response functions are derived and analyses of the results are presented. The apparent magnetic moment, as determined from these functions, contain significant errors when the dipole is misaligned radially or directionally. The errors fall into three categories: radial off-centering of a correctly oriented dipole, angular misalignment of a centered dipole, and angular misalignment of a radially off-centered dipole. One simple experimental test with a commercial magnetometer showed a 34{percent} error in the apparent moment due to radial off-centering. Practical error correction and minimization involve sample centering and rotational orientation about {ital {cflx z}} for transverse measurements, and include an additional adjustable parameter in the fitting function. Modest attention to these factors will reduce errors from {approx_equal}100{percent} difference to {le}1{percent}. The general nature of the calculations indicate that such effects exist for any type of inductive magnetometer. {copyright} {ital 1996 American Institute of Physics.}

  15. Magnetic Dipole Inflation with Cascaded ARC and Applications to Mini-Magnetospheric Plasma Propulsion

    NASA Technical Reports Server (NTRS)

    Giersch, L.; Winglee, R.; Slough, J.; Ziemba, T.; Euripides, P.

    2003-01-01

    Mini-Magnetospheric Plasma Propulsion (M2P2) seeks to create a plasma-inflated magnetic bubble capable of intercepting significant thrust from the solar wind for the purposes of high speed, high efficiency spacecraft propulsion. Previous laboratory experiments into the M2P2 concept have primarily used helicon plasma sources to inflate the dipole magnetic field. The work presented here uses an alternative plasma source, the cascaded arc, in a geometry similar to that used in previous helicon experiments. Time resolved measurements of the equatorial plasma density have been conducted and the results are discussed. The equatorial plasma density transitions from an initially asymmetric configuration early in the shot to a quasisymmetric configuration during plasma production, and then returns to an asymmetric configuration when the source is shut off. The exact reasons for these changes in configuration are unknown, but convection of the loaded flux tube is suspected. The diffusion time was found to be an order of magnitude longer than the Bohm diffusion time for the period of time after the plasma source was shut off. The data collected indicate the plasma has an electron temperature of approximately 11 eV, an order of magnitude hotter than plasmas generated by cascaded arcs operating under different conditions. In addition, indirect evidence suggests that the plasma has a beta of order unity in the source region.

  16. Structural performance of the first SSC (Superconducting Super Collider) Design B dipole magnet

    SciTech Connect

    Nicol, T.H.

    1989-09-01

    The first Design B Superconducting Super Collider (SSC) dipole magnet has been successfully tested. This magnet was heavily instrumented with temperature and strain gage sensors in order to evaluate its adherence to design constraints and design calculations. The instrumentation and associated data acquisition system allowed monitoring of the magnet during cooldown, warmup, and quench testing. This paper will focus on the results obtained from structural measurements on the suspension system during normal and rapid cooldowns and during quench studies at full magnet current. 4 refs., 9 figs.

  17. A deep dynamo generating Mercury's magnetic field.

    PubMed

    Christensen, Ulrich R

    2006-12-21

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

  18. 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

  19. Crustal Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Taylor, Patrick T.; Ravat, D.; Frawley, James J.

    1999-01-01

    Cosmos 49, Polar Orbit Geophysical Observatory (POGO) (Orbiting Geophysical Observatory (OGO-2, 4 and 6)) and Magsat have been the only low-earth orbiting satellites to measure the crustal magnetic field on a global scale. These missions revealed the presence of long- wavelength (> 500 km) crustal anomalies predominantly located over continents. Ground based methods were, for the most part, unable to record these very large-scale features; no doubt due to the problems of assembling continental scale maps from numerous smaller surveys acquired over many years. Questions arose as to the source and nature of these long-wave length anomalies. As a result there was a great stimulant given to the study of the magnetic properties of the lower crust and upper mantle. Some indication as to the nature of these deep sources has been provided by the recent results from the deep crustal drilling programs. In addition, the mechanism of magnetization, induced or remanent, was largely unknown. For computational ease these anomalies were considered to result solely from induced magnetization. However, recent results from Mars Orbiter Laser Altimeter (MOLA), a magnetometer-bearing mission to Mars, have revealed crustal anomalies with dimensions similar to the largest anomalies on Earth. These Martian features could only have been produced by remanent magnetization, since Mars lacks an inducing field. The origin of long-wavelength crustal anomalies, however, has not been completely determined. Several large crustal magnetic anomalies (e.g., Bangui, Kursk, Kiruna and Central Europe) will be discussed and the role of future satellite magnetometer missions (Orsted, SUNSAT and Champ) in their interpretation evaluated.

  20. Collinear laser spectroscopy of atomic cadmium. Extraction of nuclear magnetic dipole and electric quadrupole moments

    NASA Astrophysics Data System (ADS)

    Frömmgen, Nadja; Balabanski, Dimiter L.; Bissell, Mark L.; Bieroń, Jacek; Blaum, Klaus; Cheal, Bradley; Flanagan, Kieran; Fritzsche, Stephan; Geppert, Christopher; Hammen, Michael; Kowalska, Magdalena; Kreim, Kim; Krieger, Andreas; Neugart, Rainer; Neyens, Gerda; Rajabali, Mustafa M.; Nörtershäuser, Wilfried; Papuga, Jasna; Yordanov, Deyan T.

    2015-06-01

    Hyperfine structure A and B factors of the atomic 5 s5 p 3P2 → 5 s6 s 3S1 transition are determined from collinear laser spectroscopy data of 107-123Cd and 111 m-123 m Cd. Nuclear magnetic moments and electric quadrupole moments are extracted using reference dipole moments and calculated electric field gradients, respectively. The hyperfine structure anomaly for isotopes with s 1/2 and d 5/2 nuclear ground states and isomeric h 11/2 states is evaluated and a linear relationship is observed for all nuclear states except s 1/2. This corresponds to the Moskowitz-Lombardi rule that was established in the mercury region of the nuclear chart but in the case of cadmium the slope is distinctively smaller than for mercury. In total four atomic and ionic levels were analyzed and all of them exhibit a similar behaviour. The electric field gradient for the atomic 5 s5 p 3P2 level is derived from multi-configuration Dirac-Hartree-Fock calculations in order to evaluate the spectroscopic nuclear quadrupole moments. The results are consistent with those obtained in an ionic transition and based on a similar calculation.

  1. Dipole antennas for ultrahigh-field body imaging: a comparison with loop coils.

    PubMed

    Raaijmakers, A J E; Luijten, P R; van den Berg, C A T

    2016-09-01

    Although the potential of dipole antennas for ultrahigh-field (UHF) MRI is largely recognized, they are still relatively unknown to the larger part of the MRI community. This article intends to provide electromagnetic insight into the general operating principles of dipole antennas by numerical simulations. The major part focuses on a comparison study of dipole antennas and loop coils at frequencies of 128, 298 and 400 MHz. This study shows that dipole antennas are only efficient radiofrequency (RF) coils in the presence of a dielectric and/or conducting load. In addition, the conservative electric fields (E-fields) at the ends of a dipole are negligible in comparison with the induced E-fields in the center. Like loop coils, long dipole antennas perform better than short dipoles for deeply located imaging targets and vice versa. When the optimal element is chosen for each depth, loop coils have higher B1 (+) efficiency for shallow depths, whereas dipole antennas have higher B1 (+) efficiency for large depths. The cross-over point depth decreases with increasing frequency: 11.6, 6.2 and 5.0 cm for 128, 298 and 400 MHz, respectively. For single elements, loop coils demonstrate a better B1 (+) /√SARmax ratio for any target depth and any frequency. However, one example study shows that, in an array setup with loop coil overlap for decoupling, this relationship is not straightforward. The overlapping loop coils may generate increased specific absorption rate (SAR) levels under the overlapping parts of the loops, depending on the drive phase settings. Copyright © 2015 John Wiley & Sons, Ltd.

  2. Field Quality Study of a 1-m-Long Single-Aperture 11-T Nb$_3$Sn Dipole Model for LHC Upgrades

    SciTech Connect

    Chlachidze, G.; DiMarco, J.; Andreev, N.; Apollinari, G.; Auchmann, B.; Barzi, E.; Bossert, R.; Fiscarelli, L.; Karppinen, M.; Nobrega, F.; Novitski, I.; Rossi, L.; Smekens, D.; Turrioni, D.; Velev, G. V.; Zlobin, A. V.

    2014-01-01

    FNAL and CERN are carrying out a joint R&D program with the goal of building a 5.5-m-long twin-aperture 11-T Nb_3Sn dipole prototype that is suitable for installation in the LHC. An important part of the program is the development and test of a series of short single-aperture and twin-aperture dipole models with a nominal field of 11 T at the LHC operation current of 11.85 kA and 20% margin. This paper presents the results of magnetic measurements of a 1-m-long single-aperture Nb_3Sn dipole model fabricated and tested recently at FNAL, including geometrical field harmonics and effects of coil magnetization and iron yoke saturation.

  3. Inner-shell magnetic dipole transition in Tm atoms: A candidate for optical lattice clocks

    NASA Astrophysics Data System (ADS)

    Sukachev, D.; Fedorov, S.; Tolstikhina, I.; Tregubov, D.; Kalganova, E.; Vishnyakova, G.; Golovizin, A.; Kolachevsky, N.; Khabarova, K.; Sorokin, V.

    2016-08-01

    We consider a narrow magneto-dipole transition in the 169Tm atom at the wavelength of 1.14 μ m as a candidate for a two-dimensional-optical lattice clock. Calculating dynamic polarizabilities of the two clock levels [Xe] 4 f136 s2(J =7 /2 ) and [Xe] 4 f136 s2(J =5 /2 ) in the spectral range from 250 to 1200 nm, we find a "magic" wavelength for the optical lattice at 807 nm. Frequency shifts due to black-body radiation (BBR), the van der Waals interaction, the magnetic dipole-dipole interaction, and other effects which can perturb the transition frequency are calculated. The transition at 1.14 μ m demonstrates low sensitivity to the BBR shift corresponding to 8 ×10-17 in fractional units at room temperature which makes it an interesting candidate for high-performance optical clocks. The total estimated frequency uncertainty is less than 5 ×10-18 in fractional units. By direct excitation of the 1.14 μ m transition in Tm atoms loaded into an optical dipole trap, we set the lower limit for the lifetime of the upper clock level [Xe] 4 f136 s2(J =5 /2 ) of 112 ms which corresponds to a natural spectral linewidth narrower than 1.4 Hz. The polarizability of the Tm ground state was measured by the excitation of parametric resonances in the optical dipole trap at 532 nm.

  4. Survey of high field superconducting material for accelerator magnets

    SciTech Connect

    Scahlan, R.; Greene, A.F.; Suenaga, M.

    1986-05-01

    The high field superconductors which could be used in accelerator dipole magnets are surveyed, ranking these candidates with respect to ease of fabrication and cost as well as superconducting properties. Emphasis is on Nb/sub 3/Sn and NbTi. 27 refs., 2 figs. (LEW)

  5. Direct measurement of the plasma loss width in an optimized, high ionization fraction, magnetic multi-dipole ring cusp

    NASA Astrophysics Data System (ADS)

    Cooper, C. M.; Weisberg, D. B.; Khalzov, I.; Milhone, J.; Flanagan, K.; Peterson, E.; Wahl, C.; Forest, C. B.

    2016-10-01

    The loss width of plasma in the WiPAL multi-dipole magnetic ring cusp [Cooper et al., Phys. Plasmas 21, 13505 (2014); Forest et al., J. Plasma Phys. 81, 345810501 (2015)] has been directly measured using a novel array of probes embedded in the insulating plasma limiters. The large plasma volume ( ˜10 m3), small loss area associated with strong rare earth permanent magnets ( Bo˜2.23 kG at face), and large heating power ( ≤200 kW) produces a broad range of electron temperatures ( 2 magnetic fields, differs from previous devices: the cusp loss width is much larger than the Debye length and electron gyroradius and comparable to the collision length. Plasma parameters measured at the surface of ceramic limiter tiles covering the magnets and along radial chords in the cusp magnetic field indicate that electron density and temperature are nearly constant on magnetic field lines and that the mirror forces play little role in confining the plasma other than to constrict the loss area. Particle balance modeling is used to determine the cross field diffusion coefficient base on the measured losses to the limiters. The experimentally determined cross field diffusion coefficient (which determines the cusp loss width) is consistent with ambipolar diffusion across five orders of magnitude. The ambipolar diffusion across a given field line is set primarily by the electron-neutral collisions in the region where the magnetic field is the weakest, even though these plasmas can have ionization fractions near 1.

  6. Ground state magnetic dipole moment of {sup 35}K

    SciTech Connect

    Mertzimekis, T.J.; Mantica, P.F.; Liddick, S.N.; Tomlin, B.E.; Davies, A.D.

    2006-02-15

    The ground state magnetic moment of {sup 35}K has been measured using the technique of nuclear magnetic resonance on {beta}-emitting nuclei. The short-lived {sup 35}K nuclei were produced following the reaction of a {sup 36}Ar primary beam of energy 150 MeV/nucleon incident on a Be target. The spin polarization of the {sup 35}K nuclei produced at 2 deg. relative to the normal primary beam axis was confirmed. Together with the mirror nucleus {sup 35}S, the measurement represents the heaviest T=3/2 mirror pair for which the spin expectation value has been obtained. A linear behavior of g{sub p} vs g{sub n} has been demonstrated for the T=3/2 known mirror moments and the slope and intercept are consistent with the previous analysis of T=1/2 mirror pairs.

  7. 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.

  8. Magnetic Field Topology in Jets

    NASA Technical Reports Server (NTRS)

    Gardiner, T. A.; Frank, A.

    2000-01-01

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

  9. Torsional oscillations of neutron stars with highly tangled magnetic fields

    NASA Astrophysics Data System (ADS)

    Sotani, Hajime

    2015-11-01

    To determine the frequencies of magnetic oscillations in neutron stars with highly tangled magnetic fields, we derive the perturbation equations. We assume that the field strength of the global magnetic structure is so small that such fields are negligible compared with tangled fields, which may still be far from a realistic configuration. Then, we systematically examine the spectra of the magnetic oscillations, as varying the magnetic field strength and stellar mass. The frequencies without crust elasticity are completely proportional to the strength of the magnetic field, whose proportionality constant depends strongly on the stellar mass. On the other hand, the oscillation spectra with crust elasticity become more complicated, where the frequencies even for weak magnetic fields are different from the crustal torsional oscillations without magnetic fields. For discussing spectra, the critical field strength can play an important role, and it is determined in such a way that the shear velocity is equivalent to the Alfvén velocity at the crust basis. Additionally, we find that the effect of the crust elasticity can be seen strongly in the fundamental oscillations with a lower harmonic index, ℓ. Unlike the stellar models with a pure dipole magnetic field, we also find that the spectra with highly tangled magnetic fields become discrete, where one can expect many of the eigenfrequencies. Maybe these frequencies could be detected after the violent phenomena breaking the global magnetic field structure.

  10. 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.

  11. The Martian magnetic field

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1979-01-01

    The paper presents an overview of the Martian magnetic field measurements and the criticisms made of them. The measurements of the Mars 2, 3, and 5 spacecraft were interpreted by Dolginov et al. (1976, 1978) to be consistent with an intrinsic planetary magnetic moment of 2.5 times 10 to the 22nd power gauss cu cm, basing this result on the apparent size of the obstacle responsible for deflecting the solar wind and an apparent encounter of the spacecraft with the planetary field. It is shown that if the dependence of the Martian magnetic moment on the rotation rate was linear, the estimate of the moment would be far larger than reported by Dolginov et al. An upper limit of 250 km is calculated for the dynamo radius using the similarity law, compared with 500 km obtained by Dolginov et al. It is concluded that the possible strength of a Martian dynamo is below expectations, and it is likely that the Mars dynamo is not presently operative.

  12. Magnetic field switchable dry adhesives.

    PubMed

    Krahn, Jeffrey; Bovero, Enrico; Menon, Carlo

    2015-02-01

    A magnetic field controllable dry adhesive device is manufactured. The normal adhesion force can be increased or decreased depending on the presence of an applied magnetic field. If the magnetic field is present during the entire normal adhesion test cycle which includes both applying a preloading force and measuring the pulloff pressure, a decrease in adhesion is observed when compared to when there is no applied magnetic field. Similarly, if the magnetic field is present only during the preload portion of the normal adhesion test cycle, a decrease in adhesion is observed because of an increased stiffness of the magnetically controlled dry adhesive device. When the applied magnetic field is present during only the pulloff portion of the normal adhesion test cycle, either an increase or a decrease in normal adhesion is observed depending on the direction of the applied magnetic field.

  13. 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.

  14. Electric dipole moment searches: Effect of linear electric field frequency shifts induced in confined gases

    SciTech Connect

    Barabanov, A. L.; Golub, R.; Lamoreaux, S. K.

    2006-11-15

    The search for particle electric dipole moments (EDM's) represents a most promising way to search for physics beyond the standard model. A number of groups are planning a new generation of experiments using stored gases of various kinds. In order to achieve the target sensitivities it will be necessary to deal with the systematic error resulting from the interaction of the well-known v-vectorxE-vector field with magnetic field gradients which is often referred to as the geometric phase effect [E. D. Commins, Am. J. Phys. 59, 1077 (1991); J. M. Pendlebury et al., Phys. Rev. A 70, 032102 (2004)]. This interaction produces a frequency shift linear in the electric field, mimicking an EDM. In this work we introduce an analytic form for the velocity autocorrelation function which determines the velocity-position correlation function which in turn determines the behavior of the frequency shift [S. K. Lamoreaux and R. Golub, Phys. Rev A 71, 032104 (2005)] and show how it depends on the operating conditions of the experiment. We also discuss some additional issues.

  15. Imaging of magnetic colloids under the influence of magnetic field by cryogenic transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Wu, Jinsong; Aslam, M.; Dravid, Vinayak P.

    2008-08-01

    The application of superparamagnetic nanoparticles for in vivo magnetic resonance imaging (MRI) under external ac magnetic field has attracted considerable research efforts in recent years. However, it is unclear how superparamagnetic nanostructures arrange themselves in fluidic environment under external magnetic field. Here, we report direct visualization of the effect of applied magnetic field to the ferrofluids (about 6 nm superparamagnetic magnetite (Fe3O4) nanoparticle "colloidal" suspension) using the cryogenic transmission electron microscopy (cryo-TEM). While long dipole chains (up to millimeter range) of the magnetite along the magnetic lines are found in samples dried inside the magnetic field, only short dipole chains (within tens of nanometer scale) with random orientations are observed in the wet sample observed by cryo-TEM. In the wet sample, aggregations of medium-length dipole chains (up to hundreds of nanometer) can be observed at the areas where the nanoparticles are "solidified" when phase separation occurs. In situ formation of flux-closure rings is observed at the edge where vitreous ice sublimes due to high-energy electron radiation that leaves magnetite nanoparticles isolated in the vacuum. Such observations may help elucidate the nature of magnetic field-induced assembly in fluidic environment as in the physiological aqueous conditions in MRI and related applications.

  16. Accurate Predictions of Mean Geomagnetic Dipole Excursion and Reversal Frequencies, Mean Paleomagnetic Field Intensity, and the Radius of Earth's Core Using McLeod's Rule

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.; Conrad, Joy

    1996-01-01

    The geomagnetic spatial power spectrum R(sub n)(r) is the mean square magnetic induction represented by degree n spherical harmonic coefficients of the internal scalar potential averaged over the geocentric sphere of radius r. McLeod's Rule for the magnetic field generated by Earth's core geodynamo says that the expected core surface power spectrum (R(sub nc)(c)) is inversely proportional to (2n + 1) for 1 less than n less than or equal to N(sub E). McLeod's Rule is verified by locating Earth's core with main field models of Magsat data; the estimated core radius of 3485 kn is close to the seismologic value for c of 3480 km. McLeod's Rule and similar forms are then calibrated with the model values of R(sub n) for 3 less than or = n less than or = 12. Extrapolation to the degree 1 dipole predicts the expectation value of Earth's dipole moment to be about 5.89 x 10(exp 22) Am(exp 2)rms (74.5% of the 1980 value) and the expected geomagnetic intensity to be about 35.6 (mu)T rms at Earth's surface. Archeo- and paleomagnetic field intensity data show these and related predictions to be reasonably accurate. The probability distribution chi(exp 2) with 2n+1 degrees of freedom is assigned to (2n + 1)R(sub nc)/(R(sub nc). Extending this to the dipole implies that an exceptionally weak absolute dipole moment (less than or = 20% of the 1980 value) will exist during 2.5% of geologic time. The mean duration for such major geomagnetic dipole power excursions, one quarter of which feature durable axial dipole reversal, is estimated from the modern dipole power time-scale and the statistical model of excursions. The resulting mean excursion duration of 2767 years forces us to predict an average of 9.04 excursions per million years, 2.26 axial dipole reversals per million years, and a mean reversal duration of 5533 years. Paleomagnetic data show these predictions to be quite accurate. McLeod's Rule led to accurate predictions of Earth's core radius, mean paleomagnetic field

  17. Planetary science. Low-altitude magnetic field measurements by MESSENGER reveal Mercury's ancient crustal field.

    PubMed

    Johnson, Catherine L; Phillips, Roger J; Purucker, Michael E; Anderson, Brian J; Byrne, Paul K; Denevi, Brett W; Feinberg, Joshua M; Hauck, Steven A; Head, James W; Korth, Haje; James, Peter B; Mazarico, Erwan; Neumann, Gregory A; Philpott, Lydia C; Siegler, Matthew A; Tsyganenko, Nikolai A; Solomon, Sean C

    2015-05-22

    Magnetized rocks can record the history of the magnetic field of a planet, a key constraint for understanding its evolution. From orbital vector magnetic field measurements of Mercury taken by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft at altitudes below 150 kilometers, we have detected remanent magnetization in Mercury's crust. We infer a lower bound on the average age of magnetization of 3.7 to 3.9 billion years. Our findings indicate that a global magnetic field driven by dynamo processes in the fluid outer core operated early in Mercury's history. Ancient field strengths that range from those similar to Mercury's present dipole field to Earth-like values are consistent with the magnetic field observations and with the low iron content of Mercury's crust inferred from MESSENGER elemental composition data. PMID:25953822

  18. Planetary science. Low-altitude magnetic field measurements by MESSENGER reveal Mercury's ancient crustal field.

    PubMed

    Johnson, Catherine L; Phillips, Roger J; Purucker, Michael E; Anderson, Brian J; Byrne, Paul K; Denevi, Brett W; Feinberg, Joshua M; Hauck, Steven A; Head, James W; Korth, Haje; James, Peter B; Mazarico, Erwan; Neumann, Gregory A; Philpott, Lydia C; Siegler, Matthew A; Tsyganenko, Nikolai A; Solomon, Sean C

    2015-05-22

    Magnetized rocks can record the history of the magnetic field of a planet, a key constraint for understanding its evolution. From orbital vector magnetic field measurements of Mercury taken by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft at altitudes below 150 kilometers, we have detected remanent magnetization in Mercury's crust. We infer a lower bound on the average age of magnetization of 3.7 to 3.9 billion years. Our findings indicate that a global magnetic field driven by dynamo processes in the fluid outer core operated early in Mercury's history. Ancient field strengths that range from those similar to Mercury's present dipole field to Earth-like values are consistent with the magnetic field observations and with the low iron content of Mercury's crust inferred from MESSENGER elemental composition data.

  19. Somatosensory evoked magnetic fields in patients with stroke.

    PubMed

    Maclin, E L; Rose, D F; Knight, J E; Orrison, W W; Davis, L E

    1994-12-01

    We used magnetoencephalography to evaluate areas of sensory cortex in patients with ischemic strokes involving the somatomotor system. We measured somatosensory evoked magnetic fields using a 7-channel neuromagnetometer and estimated the location of cortical responses to median nerve stimulation in 5 patients with cortical or subcortical strokes involving the somatomotor system. All patients underwent quantitative neurological examinations and a high resolution volumetric magnetic resonance imaging. The estimated current dipoles were localized onto the patient's own MRI scan in all patients with measurable responses. The location of the estimated dipole was always in non-infarcted tissue in the anatomical region of the somatosensory cortex. In 1 patient the somatosensory dipole localized to a peninsula of cortex flanked by infarcted tissue. Single photon emission computed tomography found the localized area of cortex to have significant blood flow. The estimated current dipole strengths of somatosensory evoked fields from median nerve stimulation correlated significantly (r = 0.95, P < 0.02) with the patient's ability to recognize numbers written on the involved palm (graphesthesia). The combination of evoked magnetic field recording and magnetic resonance imaging is a promising non-invasive technology for studying brain function in patients with cerebrovascular disease.

  20. Fast superconducting magnetic field switch

    SciTech Connect

    Goren, Y.; Mahale, N.K.

    1995-12-31

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

  1. Magnetic Fields in Early Protostellar Disk Formation

    NASA Astrophysics Data System (ADS)

    González-Casanova, Diego F.; Lazarian, Alexander; Santos-Lima, Reinaldo

    2016-03-01

    We consider formation of accretion disks from a realistically turbulent molecular gas using 3D MHD simulations. In particular, we analyze the effect of the fast turbulent reconnection described by the Lazarian & Vishniac model for the removal of magnetic flux from a disk. With our numerical simulations we demonstrate how the fast reconnection enables protostellar disk formation resolving the so-called “magnetic braking catastrophe.” In particular, we provide a detailed study of the dynamics of a 0.5 M⊙ protostar and the formation of its disk for up to several thousands years. We measure the evolution of the mass, angular momentum, magnetic field, and turbulence around the star. We consider effects of two processes that strongly affect the magnetic transfer of angular momentum, both of which are based on turbulent reconnection: the first, “reconnection diffusion,” removes the magnetic flux from the disk; the other involves the change of the magnetic field's topology, but does not change the absolute value of the magnetic flux through the disk. We demonstrate that for the first mechanism, turbulence causes a magnetic flux transport outward from the inner disk to the ambient medium, thus decreasing the coupling of the disk to the ambient material. A similar effect is achieved through the change of the magnetic field's topology from a split monopole configuration to a dipole configuration. We explore how both mechanisms prevent the catastrophic loss of disk angular momentum and compare both above turbulent reconnection mechanisms with alternative mechanisms from the literature.

  2. Magnetic-dipole transitions in tungsten and other heavy elements observed with the NIST EBIT

    NASA Astrophysics Data System (ADS)

    Reader, J.; Gillaspy, J. D.; Osin, D.; Ralchenko, Yu.

    2012-05-01

    We describe recent observations with the electron beam ion trap (EBIT) at the National Institute of Standards and Technology (NIST) in which we observed large numbers of magnetic dipole (M1) transitions within the 3dn ground configurations of the highly-ionized heavy metals Hf, Ta, W, and Au. The data are interpreted by means of collisional-radiative modeling of the EBIT plasma.

  3. Design study of 15-Tesla RHQT Nb3Al block type dipole magnet

    SciTech Connect

    Yamada, R.; Ambrosio, G.; Barzi, E.; Kashikin, V.; Kikuchi, A.; Novitski, I.; Takeuchi, T.; Wake, M.; Zlobin, A.; /Fermilab /NIMC, Tsukuba /KEK, Tsukuba

    2005-09-01

    The design study of the block type 15-Tesla RHQT Nb{sub 3}Al dipole magnet, and its merits over Nb{sub 3}Sn magnets are presented. The copper stabilized RHQT Nb{sub 3}Al strand is now becoming commercially available for the application to the accelerator magnets. A 1 mm diameter RHQT Nb{sub 3}Al strand with filament size about 50 {mu}, non-copper Jc about 1000 A/mm{sup 2} at 15 Tesla at 4.2K, copper ratio of 50%, can now be produced over several hundred meters. The stress and strain characteristics of the Nb{sub 3}Al strand are superior to the Nb{sub 3}Sn strand. Another advantage is that it can tolerate a longitudinal strain up to 0.55%. The RHQT Nb{sub 3}Al Rutherford cable will have less chance of contamination of the stabilizer, compared to Nb{sub 3}Sn cable. These characteristics of the RHQT Nb{sub 3}Al will be beneficial for designing and producing 15-Tesla dipole magnets. An example 15-Tesla magnet cross section, utilizing the RHQT Nb{sub 3}Sn strand is presented. A systematic investigation on RHQT Nb{sub 3}Al strands, its Rutherford cables, and building a small racetrack magnet for cable testing are proposed.

  4. Cryostat design for the Superconducting Super Collider 50mm aperture dipole magnet

    SciTech Connect

    Nicol, T.H. ); Tsavalas, Y.P. . Medical Systems)

    1990-09-01

    The cryostat of an SSC dipole magnet consists of all magnet components except the cold mass assembly. It serves to support the cold mass accurately and reliably within the vacuum vessel, provide all required cryogenic piping, and to insulate the cold mass from heat radiated and conducted from the environment. It must function reliably during storage, shipping and handling, normal magnet operation, quenches, and seismic excitations and must be manufacturable at low cost. The major components of the cryostat are the vacuum vessel, thermal shields, multilayer insulation (MLI) system, cryogenic piping, interconnections, and suspension system. The overall design of a cryostat for superconducting accelerator magnets requires consideration of fluid flow, proper selection of materials for their thermal and structural performance at both ambient and operating temperature, and knowledge of the environment to which the magnets will be subjected over the course their 25 year expected life. This paper describes the design of the current SSC collider dipole magnet cryostat and includes discussions on the thermal, structural, and dynamic considerations involved in the development of each of the major systems. 7 refs., 1 fig., 2 tabs.

  5. 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.

  6. 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.

  7. Classical dynamics of a charged particle in a laser field beyond the dipole approximation

    NASA Astrophysics Data System (ADS)

    Jameson, Paul; Khvedelidze, Arsen

    2008-05-01

    The classical dynamics of a charged particle traveling in a laser field modeled by an elliptically polarized monochromatic electromagnetic plane wave is discussed within the time reparametrization invariant form of the nonrelativistic Hamilton-Jacobi theory. The exact parametric representation for a particle’s orbit in an arbitrary plane wave background beyond the dipole approximation and including effect of the magnetic field is derived. For an elliptically polarized monochromatic plane wave the particle’s trajectory, as an explicit function of the laboratory frame’s time, is given in terms of the Jacobian elliptic functions, whose modulus is proportional to the laser’s intensity and depends on the polarization of radiation. It is shown that the system exposes the intensity duality, correspondence between the motion in the backgrounds with various intensities. In virtue of the modular properties of the Jacobian functions, by starting with the representative “fundamental solution” and applying a certain modular transformation one can obtain the particle’s orbit in the monochromatic plane wave background with arbitrarily prescribed characteristics.

  8. Field errors introduced by eddy currents in Fermilab main injector magnets

    SciTech Connect

    Walbridge, D.G.C.; Brown, B.C.; Dinanco, J.B.; Sharoran, S.A.; Sim, J.W.

    1997-10-01

    The Fermilab Main Injector ramps from 8 GeV to 120 GeV in about half a second. The rapidly changing magnetic field induces eddy currents in the stainless steel vacuum tubes, which in turn produce error fields that can affect the beam. Field calculations and measurements are presented for the dipole and quadrupole magnets.

  9. Thermodynamic Properties of the Superconducting Dipole Magnet of the SIS100 Synchrotron

    NASA Astrophysics Data System (ADS)

    Bleile, A.; Fischer, E.; Freisleben, W.; Mierau, A.; Schnizer, P.; Szwangruber, P.

    The Heavy Ion Synchrotron SIS100 is the core facility of the international FAIR project at GSI in Darmstadt. The magnet system of the synchrotron will operate with a high cycle frequency up to 1 Hz. The magnet coils are made of a hollow NbTi composite cable cooled by forced flow of two phase helium. The dynamic heat losses in the magnets caused by fast ramping provide the major part of the heat load to the cryogenic system of SIS100. Recently the first series dipole magnet was produced and is being intensively tested at the cryogenic magnet test facility at GSI. We present the status of these tests together with the obtained opera- tion characteristics like a cool down and training behaviour, dynamic heat release and mass flow rates.

  10. Particle flocculation and filtration by high-gradient magnetic fields

    SciTech Connect

    Tsouris, C.; Yiacoumi, S.

    1997-01-01

    Flocculation and filtration of micrometer-sized particles in a high-gradient magnetic field (HGMF) were investigated. Experiments were conducted using a cryogenic magnet of 6 Tesla maximum strength. Hematite particles were used for flocculation and filtration experiments. A new approach of using magnetic fields to enhance separation of weakly magnetic particles was also investigated. This approach is based on magnetic seeding which involves flocculation of existing non-magnetic particles with injected paramagnetic particles. A particle-flocculation model was developed based on trajectory analysis. External forces due to gravity and magnetism, and interparticle forces such as electrostatic, hydrodynamic, magnetic dipole, and van der Waals forces, were taken into consideration in these models.

  11. Magnetic dipole excitations in nuclei: Elementary modes of nucleonic motion

    NASA Astrophysics Data System (ADS)

    Heyde, Kris; von Neumann-Cosel, Peter; Richter, Achim

    2010-07-01

    The nucleus is one of the most multifaceted many-body systems in the Universe. It exhibits a multitude of responses depending on the way one “probes” it. With increasing technical advancements of beams at the various accelerators and of detection systems the nucleus has, over and over again, surprised us by expressing always new ways of “organized” structures and layers of complexity. Nuclear magnetism is one of those fascinating faces of the atomic nucleus discussed in the present review. We shall not just limit ourselves to presenting the by now large data set that has been obtained in the past two decades using various probes, electromagnetic and hadronic alike and that presents ample evidence for a low-lying orbital scissors mode around 3MeV , albeit fragmented over an energy interval of the order of 1.5MeV , and higher-lying spin-flip strength in the energy region 5-9MeV in deformed nuclei nor to the presently discovered evidence for low-lying proton-neutron isovector quadrupole excitations in spherical nuclei. To the contrary, the experimental evidence is put in the perspectives of understanding the atomic nucleus and its various structures of well-organized modes of motion and thus enlarges the discussion to more general fermion and bosonic many-body systems.

  12. 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)

  13. Magnetic field therapy: a review.

    PubMed

    Markov, Marko S

    2007-01-01

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

  14. Equivalent source mapping of lunar magnetic field

    NASA Astrophysics Data System (ADS)

    Toyoshima, M.; Shibuya, H.

    2007-12-01

    JAXA (Japan Aerospace Exploration Agency) shall launch the SELENE (SELenological and ENgineering Explorer) spacecraft this autumn. Amongst many instruments, it has a magnetometer (LMAG: Lunar MAGnetomter) which will measure the magnetic field on the orbit around the Moon. The nominal orbit of the SELENE is about 100km in altitudes for 1 year observation. Although the extended mission is still not determined, LMAG team is requesting a low altitude (less than 50km) observation, if the remaining fuel allows. We are preparing data processing software for the mission. Here, we report an objective scheme for mapping the lunar crustal magnetic field from the orbital measurement data of unequal altitudes. In this study, the magnetic field is restored by solving a linear inverse-problem determining the sources distributed on the lunar surface to satisfy the observational data, which is known as the equivalent source method. Our scheme has three features improving the method: First, the source calculation is performed simultaneously with detrending. Second, magnetic charges (magnetic monopoles) are used as the equivalent sources. It reduces the density of the sources for the same smoothness in produced field, comparing to the dipole sauces. Third, the number of sources is taken large enough to avoid the problem of configuration of the sources, instead the damped least square assuming the strength of each charge is similar to the next one, and the smoothness factor is determined by minimizing Akaike's Bayesian Information Criterion (ABIC). It guarantees the objectivity of the calculation, in other words, there is no adjustable parameter which may depend of the researcher dealing the data analyses. For testing the scheme, we apply this method to the Lunar Prospector magnetometer data, and provide magnetic field map in the region centered at several regions of strong crustal field including the Reiner Gamma anomaly. The stability of the method and the resolution of the anomaly

  15. Polarity tuning of single-walled carbon nanotube by dipole field of ferroelectric polymer for thermoelectric conversion

    NASA Astrophysics Data System (ADS)

    Horike, Shohei; Misaki, Masahiro; Koshiba, Yasuko; Morimoto, Masahiro; Saito, Takeshi; Ishida, Kenji

    2016-08-01

    The tuning of the Seebeck coefficient of a single-walled carbon nanotube (SWCNT) film was achieved by using the dipole field of a ferroelectric polymer. The Seebeck coefficient was positive under an up-poling dipole field, but negative under a down-poling dipole field, whereas the control remained positive. This tunable behavior can be explained by selective carrier injection and accumulation, which was confirmed by the temperature dependence of electrical conductivity. Connecting p- and n-type SWCNT films tuned by dipole fields to create a π module resulted in a significant improvement in output voltage owing to the temperature difference between the two.

  16. Atoms and molecules in intense attosecond fields: beyond the dipole approximation

    NASA Astrophysics Data System (ADS)

    Førre, M.; Hansen, J. P.; Kocbach, L.; Selstø, S.; Kjeldsen, T. K.; Madsen, L. B.

    2007-11-01

    The exact non-dipole minimal-coupling Hamiltonian for an atomic system interacting with an explicitly time- and space-dependent laser field is transformed into the rest frame of a classical free electron in the laser field, i.e., into the Kramers-Henneberger frame. The new form of the Hamiltonian has been used to study the non-dipole dynamics of atoms and molecules in intense XUV laser pulses. The time-dependent Schrödinger equation is solved without any simplifications.

  17. Anisotropic LMN dielectronic resonances from ratios of magnetic-dipole lines

    NASA Astrophysics Data System (ADS)

    Ralchenko, Yu.; Gillaspy, J. D.

    2013-07-01

    Signatures of multi-keV LMN dielectronic resonances in highly charged 3dn ions of tungsten were detected in the intensity ratios of extreme-ultraviolet magnetic-dipole lines within ground configurations. The measurements were performed with an electron beam ion trap at beam energies of about 6 keV. Large-scale collisional-radiative modeling incorporating magnetic sublevels of autoionizing levels showed the significance of anisotropy effects due to the monodirectional propagation of the electron beam. The observation method allows simultaneous resolved registration of dielectronic resonances from several ions.

  18. A. C. losses in the SSC high energy booster dipole magnets

    SciTech Connect

    Jayakumar, R.; Kovachev, V.; Snitchler, G.; Orrell, D.

    1991-06-01

    The baseline design for the SSC High Energy Booster (HEB) has dipole bending magnets with a 50 mm aperture. An analysis of the cryogenic heat load due to A.C. losses generated in the HEB ramp cycle are reported for this magnet. Included in this analysis are losses from superconductor hysteresis, yoke hysteresis, strand eddy currents, and cable eddy currents. The A.C. loss impact of 2.5 {mu}m vs. 6 {mu}m filament conductor is presented. A 60 mm aperture design is also investigated. 8 refs., 3 tabs.

  19. 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.

  20. 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.

  1. Levitation and lateral forces between a point magnetic dipole and a superconducting sphere

    NASA Astrophysics Data System (ADS)

    H, M. Al-Khateeb; M, K. Alqadi; F, Y. Alzoubi; B, Albiss; M, K. Hasan (Qaseer; N, Y. Ayoub

    2016-05-01

    The dipole–dipole interaction model is employed to investigate the angular dependence of the levitation and lateral forces acting on a small magnet in an anti-symmetric magnet/superconducting sphere system. Breaking the symmetry of the system enables us to study the lateral force which is important in the stability of the magnet above a superconducting sphere in the Meissner state. Under the assumption that the lateral displacement of the magnet is small compared to the physical dimensions of our proposed system, analytical expressions are obtained for the levitation and lateral forces as a function of the geometrical parameters of the superconductor as well as the height, the lateral displacement, and the orientation of the magnetic moment of the magnet. The dependence of the levitation force on the height of the levitating magnet is similar to that in the symmetric magnet/superconducting sphere system within the range of proposed lateral displacements. It is found that the levitation force is linearly dependent on the lateral displacement whereas the lateral force is independent of this displacement. A sinusoidal variation of both forces as a function of the polar and azimuthal angles specifying the orientation of the magnetic moment is observed. The relationship between the stability and the orientation of the magnetic moment is discussed for different orientations.

  2. A Possible Mechanism for Generating Galactic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Davies, George; Widrow, Lawrence M.

    2000-09-01

    We demonstrate that the Biermann battery mechanism for the creation of large-scale magnetic fields can arise in a simple model protogalaxy. Analytic calculations and numerical simulations follow explicitly the generation of vorticity (and hence magnetic field) at the outward-moving shock that develops as the protogalactic perturbation collapses. Shear angular momentum then distorts this field into a dipole-like configuration. The magnitude of the field created in the fully formed disk galaxy is estimated to be 10-17 G, approximately what is needed as a seed for the galactic dynamo.

  3. INFLATION OF A DIPOLE FIELD IN LABORATORY EXPERIMENTS: TOWARD AN UNDERSTANDING OF MAGNETODISK FORMATION IN THE MAGNETOSPHERE OF A HOT JUPITER

    SciTech Connect

    Antonov, V. M.; Boyarinsev, E. L.; Boyko, A. A.; Zakharov, Yu. P.; Melekhov, A. V.; Ponomarenko, A. G.; Posukh, V. G.; Shaikhislamov, I. F.; Khodachenko, M. L.; Lammer, H.

    2013-05-20

    Giant exoplanets at close orbits, or so-called hot Jupiters, are supposed to have an intensive escape of upper atmospheric material heated and ionized by the radiation of a host star. An interaction between outflowing atmospheric plasma and the intrinsic planetary magnetic dipole field leads to the formation of a crucial feature of a hot Jupiter's magnetosphere-an equatorial current-carrying magnetodisk. The presence of a magnetodisk has been shown to influence the topology of a hot Jupiter's magnetosphere and to change a standoff distance of the magnetopause. In this paper, the basic features of the formation of a hot Jupiter's magnetodisk are studied by means of a laboratory experiment. A localized central source produces plasma that expands outward from the surface of the dipole and inflates the magnetic field. The observed structure of magnetic fields, electric currents, and plasma density indicates the formation of a relatively thin current disk extending beyond the Alfvenic point. At the edge of the current disk, an induced magnetic field was found to be several times larger than the field of the initial dipole.

  4. Cyclical magnetic field flow fractionation

    NASA Astrophysics Data System (ADS)

    Tasci, T. O.; Johnson, W. P.; Gale, B. K.

    2012-04-01

    In this study, a new magnetic field flow fractionation (FFF) system was designed and modeled by using finite element simulations. Other than current magnetic FFF systems, which use static magnetic fields, our system uses cyclical magnetic fields. Results of the simulations show that our cyclical magnetic FFF system can be used effectively for the separation of magnetic nanoparticles. Cyclical magnetic FFF system is composed of a microfluidic channel (length = 5 cm, height = 30 μm) and 2 coils. Square wave currents of 1 Hz (with 90 deg of phase difference) were applied to the coils. By using Comsol Multiphysics 3.5a, magnetic field profile and corresponding magnetic force exerted on the magnetite nanoparticles were calculated. The magnetic force data were exported from Comsol to Matlab. In Matlab, a parabolic flow profile with maximum flow speed of 0.4 mL/h was defined. Particle trajectories were obtained by the calculation of the particle speeds resulted from both magnetic and hydrodynamic forces. Particle trajectories of the particles with sizes ranging from 10 to 50 nm were simulated and elution times of the particles were calculated. Results show that there is a significant difference between the elution times of the particles so that baseline separation of the particles can be obtained. In this work, it is shown that by the application of cyclical magnetic fields, the separation of magnetic nanoparticles can be done efficiently.

  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 fields and fish behavior].

    PubMed

    Krylov, V V; Iziumov, Iu G; Izvekov, E I; Nepomniashchikh, V A

    2013-01-01

    In the review, contemporary data on the influence of natural and artificial magnetic fields on fish behavior are considered. In this regard, elasmobranchs and teleosts appear to be studied most exhaustively. Elasmobranchs and some teleosts are able to perceive magnetic fields via electroreceptors. A number of teleosts can sense magnetic fields via sensory cells containing crystals of biogenic magnetite. Laboratory experiments and field observations indicate the influence of magnetic fields on fish locomotor activity and spatial distribution. The geomagnetic field can be used by fish for navigation. Besides, artificial magnetic fields and natural fluctuations of the geomagnetic field can affect fish embryos leading to alterations in their development. It is suggested that, afterwards, these alterations can have an effect on fish behavior.

  7. [Magnetic fields and fish behavior].

    PubMed

    Krylov, V V; Iziumov, Iu G; Izvekov, E I; Nepomniashchikh, V A

    2013-01-01

    In the review, contemporary data on the influence of natural and artificial magnetic fields on fish behavior are considered. In this regard, elasmobranchs and teleosts appear to be studied most exhaustively. Elasmobranchs and some teleosts are able to perceive magnetic fields via electroreceptors. A number of teleosts can sense magnetic fields via sensory cells containing crystals of biogenic magnetite. Laboratory experiments and field observations indicate the influence of magnetic fields on fish locomotor activity and spatial distribution. The geomagnetic field can be used by fish for navigation. Besides, artificial magnetic fields and natural fluctuations of the geomagnetic field can affect fish embryos leading to alterations in their development. It is suggested that, afterwards, these alterations can have an effect on fish behavior. PMID:25438567

  8. [Magnetic fields and fish behavior].

    PubMed

    2013-01-01

    In the review, contemporary data on the influence of natural and artificial magnetic fields on fish behavior are considered. In this regard, elasmobranchs and teleosts appear to be studied most exhaustively. Elasmobranchs and some teleosts are able to perceive magnetic fields via electroreceptors. A number of teleosts can sense magnetic fields via sensory cells containing crystals of biogenic magnetite. Laboratory experiments and field observations indicate the influence of magnetic fields on fish locomotor activity and spatial distribution. The geomagnetic field can be used by fish for navigation. Besides, artificial magnetic fields and natural fluctuations of the geomagnetic field can affect fish embryos leading to alterations in their development. It is suggested that, afterwards, these alterations can have an effect on fish behavior. PMID:25508098

  9. Magnetic fields in the cosmos

    NASA Astrophysics Data System (ADS)

    Parker, E. N.

    1983-08-01

    Descriptive models for the dynamo processes that generate magnetic fields around celestial objects are reviewed. Magnetic fields are produced, along with an electric current, when a conductor is moved perpendicularly through a magnetic field, so long as the resulting current is fed back into the conductor to amplify the current and field. In MHD theory, the lines of force of the magnetic field travel with the conducting fluid. A weak current or field must be present initially to generate the field. Planets have molten cores and stars have ionized gases to act as the conductors, and all space has sufficient gas with free electrons. The rotations of the planets, stars, and galaxy enhance the magnetic fields. Convective patterns have been characterized in the earth's molten core because of anomalies observed in the magnetic field at the surface. It has been shown that the faster a planet rotates, the more powerful its magnetic field is. However, fluid motions will produce fields only if the fluid motion is helical. The exact mechanism in stars could be primordial magnetism trapped during formation. However, in galaxies, the Biermann battery effect, wherein free electrons move along the surfaces of stars, could create enough of a field for the amplification process to proceed.

  10. Magnetic-field-dosimetry system

    SciTech Connect

    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.

  11. Electrical dipole-dipole interaction effects on magnetocurrent in organic phosphorescent materials

    NASA Astrophysics Data System (ADS)

    Shao, Ming; Dai, Yanfeng; Ma, Dongge; Hu, Bin

    2011-08-01

    This letter reports the experimental studies on electrical dipole-dipole interaction effects on magnetocurrent (MC) and magneto-electroluminescence (MFEEL) based on two phosphorescent dyes: heavy-metal complex Ir(ppy)3 and Ir(ppy)2(acac) with strong spin-orbital coupling but different electrical dipole moments. We find that the Ir(ppy)3 with strong electrical dipole moment shows negligible MC and MFEEL. However, the Ir(ppy)2(acac) with weak dipole moment exhibits appreciable MC and MFEEL. The experimental results suggest that the electrical dipole-dipole interaction can change the MC and MFEEL from capture-based regime, where charge carriers are captured through spin-dependent process at short distance, to intersystem crossing-based regime, where charge carriers are captured through spin random process at long distance. As a result, changing electrical dipole-dipole interaction presents a new pathway to tune magnetic field effects in organic semiconductors.

  12. Mars Observer magnetic fields investigation

    NASA Technical Reports Server (NTRS)

    Acuna, M. H.; Connerney, J. E. P.; Wasilewski, P.; Lin, R. P.; Anderson, K. A.; Carlson, C. W.; Mcfadden, J.; Curtis, D. W.; Reme, H.; Cros, A.

    1992-01-01

    The magnetic fields experiment designed for the Mars Observer mission will provide definitive measurements of the Martian magnetic field from the transition and mapping orbits planned for the Mars Observer. The paper describes the instruments (which include a classical magnetometer and an electron reflection magnetometer) and techniques designed to investigate the nature of the Martian magnetic field and the Mars-solar wind interaction, the mapping of crustal magnetic fields, and studies of the Martian ionosphere, which are activities included in the Mars Observer mission objectives. Attention is also given to the flight software incorporated in the on-board data processor, and the procedures of data processing and analysis.

  13. Distributed magnetic field positioning system using code division multiple access

    NASA Technical Reports Server (NTRS)

    Prigge, Eric A. (Inventor)

    2003-01-01

    An apparatus and methods for a magnetic field positioning system use a fundamentally different, and advantageous, signal structure and multiple access method, known as Code Division Multiple Access (CDMA). This signal architecture, when combined with processing methods, leads to advantages over the existing technologies, especially when applied to a system with a large number of magnetic field generators (beacons). Beacons at known positions generate coded magnetic fields, and a magnetic sensor measures a sum field and decomposes it into component fields to determine the sensor position and orientation. The apparatus and methods can have a large `building-sized` coverage area. The system allows for numerous beacons to be distributed throughout an area at a number of different locations. A method to estimate position and attitude, with no prior knowledge, uses dipole fields produced by these beacons in different locations.

  14. 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."

  15. Magnetic Field of Mars

    NASA Astrophysics Data System (ADS)

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

    2000-07-01

    bodies combined with later absolute dating of Martian geologic units could lead to a quantitative constraint on the thermal history of the planet, i.e. the time when convective dynamo generation ceased in the core. Determination of directions of magnetization of anomaly sources as a function of age combined with the expectation that the Martian dynamo field was roughly aligned with the rotation axis would lead to a means of investigating polar wandering for Mars. Preliminary analysis of two magnetic anomalies in the northern polar region has yielded paleomagnetic pole positions near 50 N, 135 W, about 30 degrees north of Olympus Mons. This location is roughly consistent with the orientation of the planet expected theoretically prior to the formation of the Tharsis region. In the future, more accurate observations of the vector field at the lowest possible altitudes would significantly improve our understanding of Martian thermal history, polar wandering, and upper crustal evolution. Mapping potential resources (e.g., iron-rich source bodies) for future practical use would also be a side benefit. Additional information is contained in the original abstract.

  16. 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

  17. 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.

  18. Status of 4-cm-aperture, 17-m-long SSC dipole magnet R D program at BNL

    SciTech Connect

    Devred, A.; Bush, T.; Coombes, R.; DiMarco, J.; Goodzeit, C.; Kuzminski, J.; Puglisi, M.; Radusewicz, P.; Sanger, P.; Schermer, R.; Spigo, G.; Tompkins, J.; Turner, J.; Wolf, Z.; Yu, Y.; Zheng, H. ); Ogitsu, T. National Lab. for High Energy Physics, Tsukuba, Ibaraki ); Anarella,

    1991-06-01

    Over the last year-and-a-half, several 4-cm-aperture, 17-m-long dipole magnet prototypes were built by Brookhaven National Laboratory (BNL) under contract with the Superconducting Super Collider (SSC) Laboratory. These prototypes are the last phase of a half-decade-long R D program, carried out in collaboration with Fermi National Accelerator Laboratory and Lawrence Berkeley Laboratory, and aimed at demonstrating the feasibility of the SSC main ring dipole magnets. They also prepare the way of the 5-cm-aperture dipole magnet program to be started soon. In this paper, we analyze the mechanical behavior of the BNL prototypes during cool-down and excitation, and we attempt to relate this behavior to the magnet features. The data reveal that the mechanical behavior is sensitive to the vertical collar-yoke interference, and that the magnets exhibited somewhat erratic changes in coil end-loading during cool-down. 9 refs., 6 figs.

  19. Far-field Fano resonance in nanoring lattices modeled from extracted, point dipole polarizability

    NASA Astrophysics Data System (ADS)

    DeJarnette, Drew; Blake, Phillip; Forcherio, Gregory T.; Keith Roper, D.

    2014-01-01

    Coupling and extinction of light among particles representable as point dipoles can be characterized using the coupled dipole approximation (CDA). The analytic form for dipole polarizability of spheroidal particles supports rapid electrodynamic analysis of nanoparticle lattices using CDA. However, computational expense increases for complex shapes with non-analytical polarizabilities which require discrete dipole (DDA) or higher order approximations. This work shows fast CDA analysis of assembled nanorings is possible using a single dipole nanoring polarizability extrapolated from a DDA calculation by summing contributions from individual polarizable volume elements. Plasmon resonance wavelengths of nanorings obtained using extracted polarizabilities blueshift as wall dimensions-to-inner radius aspect ratio increases, consistent with published theory and experiment. Calculated far-field Fano resonance energy maximum and minimum wavelengths were within 1% of full volume element results. Considering polarizability allows a more complete physical picture of predicting plasmon resonance location than metal dielectric alone. This method reduces time required for calculation of diffractive coupling more than 40 000-fold in ordered nanoring systems for 400-1400 nm incident wavelengths. Extension of this technique beyond nanorings is possible for more complex shapes that exhibit dipolar or quadrupole radiation patterns.

  20. Dipole-field sums and Lorentz factors for orthorhombic lattices, and implications for polarizable molecules

    NASA Technical Reports Server (NTRS)

    Purvis, C. K.; Taylor, P. L.

    1982-01-01

    A method for computing the Lorentz tensor components in single crystals via rapidly convergent sums of Bessels functions is developed using the relationship between dipole-field sums and the tensor components. The Lorentz factors for simple, body-centered, and base-centered orthorhombic lattices are computed using this method, and the derivative Lorentz factors for simple orthorhombic lattices are also determined. Both the Lorentz factors and their derivatives are shown to be very sensitive to a lattice structure. The equivalent of the Clausius-Mossotti relation for general orthorhombic lattices is derived using the Lorentz-factor formalism, and the permanent molecular dipole moment is related to crystal polarization for the case of a ferroelectric of polarizable point dipoles. It is concluded that the polarization enhancement due to self-polarization familiar from classical theory may actually be a reduction in consequences of negative Lorentz factors in one or two lattice directions for noncubic crystals.

  1. 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.

  2. Magnetic field generation in the cores of terrestrial bodies

    NASA Technical Reports Server (NTRS)

    Runcorn, S. K.

    1985-01-01

    Efforts to find some scaling law for the dipole moments of planets seem illusory for, although dynamo theory is still in a rudimentary state, once the critical magnetic Reynolds Number is exceeded it appears that the field strength is determined by the energy source, it it is permissible to treat the core as a heat engine. For this reason the lunar magnetic field is of special significance as the paleomagnetic evidence strongly suggests that the surface field was about 1 G 3.9 by diminishing exponentially to about .02 G 3.2 by ago and completely disappearing some time later.

  3. Multipole and field uniformity tailoring of a 750 MHz rf dipole

    SciTech Connect

    Delayen, Jean R.; Castillo, Alejandro

    2014-12-01

    In recent years great interest has been shown in developing rf structures for beam separation, correction of geometrical degradation on luminosity, and diagnostic applications in both lepton and hadron machines. The rf dipole being a very promising one among all of them. The rf dipole has been tested and proven to have attractive properties that include high shunt impedance, low and balance surface fields, absence of lower order modes and far-spaced higher order modes that simplify their damping scheme. As well as to be a compact and versatile design in a considerable range of frequencies, its fairly simple geometry dependency is suitable both for fabrication and surface treatment. The rf dipole geometry can also be optimized for lowering multipacting risk and multipole tailoring to meet machine specific field uniformity tolerances. In the present work a survey of field uniformities, and multipole contents for a set of 750 MHz rf dipole designs is presented as both a qualitative and quantitative analysis of the inherent flexibility of the structure and its limitations.

  4. A fiber optic strain measurement and quench localization system for use in superconducting accelerator dipole magnets

    SciTech Connect

    van Oort, J.M.; Scanlan, R.M.; ten Kate, H.H.J.

    1994-10-17

    A novel fiber-optic measurement system for superconducting accelerator magnets is described. The principal component is an extrinsic Fabry-Perot Interferometer to determine localized strain and stress in coil windings. The system can be used either as a sensitive relative strain measurement system or as an absolute strain detector. Combined, one can monitor the mechanical behaviour of the magnet system over time during construction, long time storage and operation. The sensing mechanism is described, together with various tests in laboratory environments. The test results of a multichannel test matrix to be incorporated first in the dummy coils and then in the final version of a 13T Nb{sub 3}Sn accelerator dipole magnet are presented. Finally, the possible use of this system as a quench localization system is proposed.

  5. 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

  6. 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.

  7. Structure of magnetic field lines

    NASA Astrophysics Data System (ADS)

    Golmankhaneh, Ali Khalili; Golmankhaneh, Alireza Khalili; Jazayeri, Seyed Masud; Baleanu, Dumitru

    2012-02-01

    In this paper the Hamiltonian structure of magnetic lines is studied in many ways. First it is used vector analysis for defining the Poisson bracket and Casimir variable for this system. Second it is derived Pfaffian equations for magnetic field lines. Third, Lie derivative and derivative of Poisson bracket is used to show structure of this system. Finally, it is shown Nambu structure of the magnetic field lines.

  8. 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.

  9. 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.

  10. 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.

  11. Electromagnetic vacuum of complex media: Dipole emission versus light propagation, vacuum energy, and local field factors

    SciTech Connect

    Donaire, M.

    2011-02-15

    We offer a unified approach to several phenomena related to the electromagnetic vacuum of a complex medium made of point electric dipoles. To this aim, we apply the linear response theory to the computation of the polarization field propagator and study the spectrum of vacuum fluctuations. The physical distinction among the local density of states which enter the spectra of light propagation, total dipole emission, coherent emission, total vacuum energy, and Schwinger-bulk energy is made clear. Analytical expressions for the spectrum of dipole emission and for the vacuum energy are derived. Their respective relations with the spectrum of external light and with the Schwinger-bulk energy are found. The light spectrum and the Schwinger-bulk energy are determined by the Dyson propagator. The emission spectrum and the total vacuum energy are determined by the polarization propagator. An exact relationship of proportionality between both propagators is found in terms of local field factors. A study of the nature of stimulated emission from a single dipole is carried out. Regarding coherent emission, it contains two components. A direct one which is transferred radiatively and directly from the emitter into the medium and whose spectrum is that of external light. And an indirect one which is radiated by induced dipoles. The induction is mediated by one (and only one) local field factor. Regarding the vacuum energy, we find that in addition to the Schwinger-bulk energy the vacuum energy of an effective medium contains local field contributions proportional to the resonant frequency and to the spectral line width.

  12. Material Procurement Report for the FNAL pp Forward Detector's Toroids and Cos8 Dipole Magnets

    SciTech Connect

    Cline, D.; Morse, R.; Orosz, I.; Thomas, L.C.

    1980-10-27

    We outline the possibilities of starting construction of the {bar p}p forward detector toroids and cos{theta} dipole magnets described in CDP Note 64 as soon as possible using material that already exists on the FNAL site. Personal inspection of the steel supplies indicates that as much as 2000 tons of steel or over 50% of all the steel needed for the toroids is now available at the FNAL boneyard. Copper inventories indicate that there is enough copper on the FNAL site to construct both the toroid magnets and the cos{theta} dipole magnets. A construction schedule of one toroid in FY81, two toroids in FY82, and the final toroid in FY83 is shown to be feasible. Floor space and loading requirements for the IR Hall housing the forward detector are examined and finally, budgets for the initial FY8l phase and the completed project are given. The FY81 costs are $393K and to-completion costs are $1506K.

  13. Stochastic reversal dynamics of two interacting magnetic dipoles: A simple model experiment.

    PubMed

    Plihon, Nicolas; Miralles, Sophie; Bourgoin, Mickael; Pinton, Jean-François

    2016-07-01

    We report an experimental study of the dynamics of two coupled magnetic dipoles. The experiment consists in two coplanar permanent disk magnets separated by a distance d, each allowed to rotate on a fixed parallel axis-each magnet's axis being perpendicular to its dipolar moment vector. A torque of adjustable strength can be externally applied to one of the magnets, the other magnet being free. The driving torque may be time-independent or temporally fluctuating. We study the influence of the parameters of the driving torque on the dynamics of the coupled system, in particular the emergence of dynamical regimes such as stochastic reversals. We report transitions between stationary and stochastic reversal regimes. All the observed features can be understood by a simple mechanical dynamical model. The transition between statistically stationary regimes and reversals is explained introducing an effective potential energy incorporating both the coupling between magnets and the external driving. Relations between this simple experimental model with macroscopic models of magnetic spin coupling, as well as with chaotic reversals of turbulent dynamos, are discussed. PMID:27575140

  14. Temperature-dependent terahertz magnetic dipole radiation from antiferromagnetic GdFeO{sub 3} ceramics

    SciTech Connect

    Fu, Xiaojian; Xi, Xiaoqing; Bi, Ke; Zhou, Ji

    2013-11-18

    Temperature-dependent terahertz magnetic dipole radiation in antiferromagnetic GdFeO{sub 3} ceramic is investigated both theoretically and experimentally in this work. A two-level quantum transition mechanism is introduced to describe the excitation-radiation process, and radiative lifetime is derived analytically from the change of spin state density during this process. Terahertz spectral measurements demonstrate that the radiative frequency exhibits a red-shift and lifetime shortens as temperature increases, which is in good agreement with theoretical predictions. The temperature-sensitive radiative frequency and excellent terahertz emission mean that the antiferromagnetic ceramics show potential for application in terahertz sensors and frequency-tunable terahertz lasers.

  15. Lowest four-quasiparticle magnetic dipole band in {sup 128}Ba

    SciTech Connect

    Vogel, O.; Dewald, A.; von Brentano, P.; Gableske, J.; Kruecken, R.; Nicolay, N.; Gelberg, A.; Petkov, P.; Gizon, A.; Gizon, J.; Bazzacco, D.; Rossi Alvarez, C.; Pavan, P.; Lunardi, S.; Napoli, D.R.; Frauendorf, S.; Doenau, F.

    1997-09-01

    The four-quasiparticle magnetic dipole band in {sup 128}Ba has been investigated with the {sup 96}Zr({sup 36}S,4n){sup 128}Ba reaction at the GASP spectrometer of the Laboratori Nazionali di Legnaro. Linking transitions to the previously known positive parity states have been observed for the first time in this mass region and new transitions on top of the band have been found. The experimental results are compared to previously made tilted axis cranking calculations. {copyright} {ital 1997} {ital The American Physical Society}

  16. Clues for genesis of magnetic field structure of Mercury

    NASA Astrophysics Data System (ADS)

    Hiremath, K. M.

    2012-07-01

    Recent space observations suggest that Mercury inherits a weak and predominantly large-scale steady dipole like magnetic field structure. Present popular paradigm is to invoke most promising geodynamo like phenomenon that requires the main ingredients such as either a full or partial convection of the interior and fast rotation such that magnetic (Lorentz) and Coriolis forces are of similar order of magnitudes. Hence, the ratio of Lorentz to Coriolis force, called the Elsasser number Λ, must be order of unity. Contrary to the expectation, Mercury rotates so slow that Elsasser number turns out to be << 1. There are also other alternative models to explain genesis of magnetic field structure of Mercury. With the observed constraint of Mercury's atmospheric magnetic field structure, internal magnetic field structure is obtained as a solution of magnetic diffusion equation in the core and a combined multipolar (dipole and quadrupole like magnetic field structures embedded in the uniform field) solution of a current free like magnetic field structure in the mantle and in the atmosphere. Magnetic diffusion time scales are estimated to be ˜ billion years suggesting that present day magnetic field structure might be of primordial origin. In order to reconcile with the experimental fact that, as temperature of Mercury's iron core is above Curie temperature and primordial magnetic field structure must be non-existent, it is proposed that permanency of such a large-scale magnetic field structure of the planet is attained during Mercury's early evolutionary history of heavy bombardments by the asteroids and comets leaving their imprints as craters on this planet. That means the solar system bodies that have heavy bombardments with high density craters during the early epochs of such catastrophic events should have strong magnetic field structures. Is this hypothesis universal? Can this hypothesis gives some clues regarding presence or absence of magnetic field structure of

  17. Magnetic space-based field measurements

    NASA Technical Reports Server (NTRS)

    Langel, R. A.

    1981-01-01

    Because the near Earth magnetic field is a complex combination of fields from outside the Earth of fields from its core and of fields from its crust, measurements from space prove to be the only practical way to obtain timely, global surveys. Due to difficulty in making accurate vector measurements, early satellites such as Sputnik and Vanguard measured only the magnitude survey. The attitude accuracy was 20 arc sec. Both the Earth's core fields and the fields arising from its crust were mapped from satellite data. The standard model of the core consists of a scalar potential represented by a spherical harmonics series. Models of the crustal field are relatively new. Mathematical representation is achieved in localized areas by arrays of dipoles appropriately located in the Earth's crust. Measurements of the Earth's field are used in navigation, to map charged particles in the magnetosphere, to study fluid properties in the Earth's core, to infer conductivity of the upper mantels, and to delineate regional scale geological features.

  18. Fabrication and Test Results of a Prototype, Nb3Sn Superconducting Racetrack Dipole Magnet

    SciTech Connect

    Gourlay, S. A.; Chow, K.; Dietderich, D.R.; Gupta, R.; Hannaford, R.; Harnden, W.; Lietzke, A.; McInturff, A.D.; Millos, G.A.; Morrison, L.; Morrison, M.; Scanlan, R.M.

    1998-09-01

    A prototype, Nb{sub 3}Sn superconducting magnet, utilizing a racetrack coil design has been built and tested. This magnet represents the first step in a recently implemented program to develop a high field, accelerator quality magnet. This magnet was constructed with coils wound from conductor developed for the ITER project, limiting the magnet to a field of 6-7 Tesla. Subsequent magnets in the program will utilize improved conductor, culminating in a magnet design capable of producing fields approaching 15 Tesla. The simple geometry is more suitable for the use of brittle superconductors necessary to eventually reach high field levels. In addition, fewer and simpler parts are used in fabricating these coils compared with the more conventional cosine theta cross section coils. The general fabrication steps, mechanical design and quench performance are discussed.

  19. Nb$_3$Sn High Field Magnets for the High Luminosity LHC Upgrade Project

    SciTech Connect

    Ambrosio, Giorgio

    2015-01-01

    The High Luminosity upgrade of the Large Hadron Collider at CERN requires a new generation of high field superconducting magnets. High field large aperture quadrupoles (MQXF) are needed for the low-beta triplets close to the ATLAS and CMS detectors, and high field two-in-one dipoles (11 T dipoles) are needed to make room for additional collimation. The MQXF quadrupoles, with a field gradient of 140 T/m in 150 mm aperture, have a peak coil field of 12.1 T at nominal current. The 11 T dipoles, with an aperture of 60 mm, have a peak coil field of 11.6 T at nominal current. Both magnets require Nb3Sn conductor and are the first applications of this superconductor to actual accelerator magnets.

  20. Repetitive Adjustment to Estimate the Electric Current Sources in a Nerve Fiber with Magnetic Field Measurement

    NASA Astrophysics Data System (ADS)

    Hayami, Takehito; Mishima, Yukuo; Hiwaki, Osamu

    Magnetic field measuring equipment provides us the way to examine the active position of a peripheral nerve without contact or invasion. To develop a process to estimate the position precisely, simulation study of the magnetic field induced by a myelinated nerve fiber was executed. The electric current sources around the active position of a nerve fiber can be approximated as a pair of electric current dipoles, which represent depolarization and repolarization respectively. Therefore the current sources to estimate from the detected pattern of the magnetic field were modeled as a pair of electric current dipoles. A repetitive adjustment process was proposed as an effective method to find the appropriate positions of the dipoles as the sources of the magnetic fields.

  1. Magnetic field synthesis for microwave magnetics

    NASA Astrophysics Data System (ADS)

    Morgenthaler, F. R.

    1982-04-01

    The Microwave and Quantum Magnetics Group of the M.I.T. Department of Electrical Engineering and Computer Science undertook a two-year research program directed at developing synthesis procedures that allow magnetostatic and/or magnetoelastic modes to be specially tailored for microwave signal processing applications that include magnetically tunable filters and limiters as well as delay lines that are either linearly dispersive or nondispersive over prescribed bandwidths. Special emphasis was given to devices employing thin films of yttrium iron garnet (YIG) that are blessed with spatially nonuniform dc magnetic fields.

  2. Magnetic field structure evolution in rotating magnetic field plasmas

    SciTech Connect

    Petrov, Yuri; Yang Xiaokang; Huang, T.-S.

    2008-07-15

    A study of magnetic field structure evolution during 40-ms plasma discharge has been performed in a new device with 80 cm long/40 cm diameter cylindrical chamber, in which a plasma current I{sub p}{approx_equal}2 kA was driven and sustained by a rotating magnetic field. The main focus of the experiments is on how the changes in externally applied magnetic field affect the current profile and magnetic field in plasma. During plasma discharge, a pulse current was briefly fed to a magnetic coil located at the midplane (middle coil). The magnetic field in cross section of plasma was scanned with pickup probes. Two regimes were studied: without and with an external toroidal field (TF) produced by axial I{sub z} current. With a relatively small current (I{sub m} {<=} 600 A) in the middle coil, the plasma current is boosted up to 5 kA. The magnetic flux surfaces become extended along the axial Z direction, sometimes with the formation of doublet shape plasma. The regime without TF appears to be less stable, presumably due to the reversal of plasma current in central area of plasma column.

  3. Oscillating dynamo in the presence of a fossil magnetic field - The solar cycle

    NASA Technical Reports Server (NTRS)

    Levy, E. H.; Boyer, D.

    1982-01-01

    Hydromagnetic dynamo generation of oscillating magnetic fields in the presence of an external, ambient magnetic field introduces a marked polarity asymmetry between the two halves of the magnetic cycle. The principle of oscillating dynamo interaction with external fields is developed, and a tentative application to the sun is described. In the sun a dipole moment associated with the stable fluid beneath the convection zone would produce an asymmetrical solar cycle.

  4. 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.

  5. Anomalous anisotropies of cosmic rays from turbulent magnetic fields.

    PubMed

    Ahlers, Markus

    2014-01-17

    The propagation of cosmic rays (CRs) in turbulent interstellar magnetic fields is typically described as a spatial diffusion process. This formalism predicts only a small deviation from an isotropic CR distribution in the form of a dipole in the direction of the CR density gradient or relative background flow. We show that the existence of a global CR dipole moment necessarily generates a spectrum of higher multipole moments in the local CR distribution. These anomalous anisotropies are a direct consequence of Liouville's theorem in the presence of a local turbulent magnetic field. We show that the predictions of this model are in excellent agreement with the observed power spectrum of multi-TeV CRs.

  6. 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.

  7. Precession of Uranus and Neptune and their magnetic field

    NASA Technical Reports Server (NTRS)

    Dolginov, Sh. SH.

    1993-01-01

    The strength of the dipole magnetic field of a planet, H(sub p), can be estimated relative to that of the Earth at the epoch of the observation. The generation of magnetic fields in Uranus and Neptune occurs at very different depths for different values of sigma. This assertion is confirmed by the estimation of the Reynolds number (R(sub m)) and agrees with the difference of the contributions of the Joule heat losses into the observed heat fluxes of Uranus and Neptune.

  8. Hindered magnetic dipole transitions between P-wave bottomonia and coupled-channel effects

    NASA Astrophysics Data System (ADS)

    Guo, Feng-Kun; Meißner, Ulf-G.; Yang, Zhi

    2016-09-01

    In the hindered magnetic dipole transitions of heavy quarkonia, the coupled-channel effects originating from the coupling of quarkonia to a pair of heavy and anti-heavy mesons can play a dominant role. Here, we study the hindered magnetic dipole transitions between two P-wave bottomonia, χb (nP) and hb (n‧ P), with n ≠n‧. In these processes the coupled-channel effects are expected to lead to partial widths much larger than the quark model predictions. We estimate these partial widths which, however, are very sensitive to unknown coupling constants related to the vertices χb0 (nP) B B bar . A measurement of the hindered M1 transitions can shed light on the coupled-channel dynamics in these transitions and hence on the size of the coupling constants. We also suggest to check the coupled-channel effects by comparing results from quenched and fully dynamical lattice QCD calculations.

  9. Possible shape coexistence and magnetic dipole transitions in {sup 17}C and {sup 21}Ne

    SciTech Connect

    Sagawa, H.; Zhou, X. R.; Suzuki, Toshio; Yoshida, N.

    2008-10-15

    Magnetic dipole (M1) transitions of N=11 nuclei {sup 17}C and {sup 21}Ne are investigated by using shell model and deformed Skyrme Hartree-Fock + blocked BCS wave functions. Shell model calculations predict well observed energy spectra and magnetic dipole transitions in {sup 21}Ne, while the results are rather poor to predict these observables in {sup 17}C. In the deformed HF calculations, the ground states of the two nuclei are shown to have large prolate deformations close to {beta}{sub 2}=0.4. It is also pointed out that the first K{sup {pi}}=1/2{sup +} state in {sup 21}Ne is prolately deformed, while the first K{sup {pi}}=1/2{sup +} state in {sup 17}C is predicted to have a large oblate deformation close to the ground state in energy, We point out that the experimentally observed large hindrance of the M1 transition between I{sup {pi}}=1/2{sup +} and 3/2{sup +} in {sup 17}C can be attributed to a shape coexistence near the ground state of {sup 17}C.

  10. Nuclear Magnetic Dipole and Electric Quadrupole Moments: Their Measurement and Tabulation as Accessible Data

    SciTech Connect

    Stone, N. J.

    2015-09-15

    The most recent tabulations of nuclear magnetic dipole and electric quadrupole moments have been prepared and published by the Nuclear Data Section of the IAEA, Vienna [N. J. Stone, Report No. INDC(NDS)-0650 (2013); Report No. INDC(NDS)-0658 (2014)]. The first of these is a table of recommended quadrupole moments for all isotopes in which all experimental results are made consistent with a limited number of adopted standards for each element; the second is a combined listing of all measurements of both moments. Both tables cover all isotopes and energy levels. In this paper, the considerations relevant to the preparation of both tables are described, together with observations as to the importance and (where appropriate) application of necessary corrections to achieve the “best” values. Some discussion of experimental methods is included with emphasis on their precision. The aim of the published quadrupole moment table is to provide a standard reference in which the value given for each moment is the best available and for which full provenance is given. A table of recommended magnetic dipole moments is in preparation, with the same objective in view.

  11. Selective Plasmonic Enhancement of Electric- and Magnetic-Dipole Radiations of Er Ions.

    PubMed

    Choi, Bongseok; Iwanaga, Masanobu; Sugimoto, Yoshimasa; Sakoda, Kazuaki; Miyazaki, Hideki T

    2016-08-10

    Lanthanoid series are unique in atomic elements. One reason is because they have 4f electronic states forbidding electric-dipole (ED) transitions in vacuum and another reason is because they are very useful in current-day optical technologies such as lasers and fiber-based telecommunications. Trivalent Er ions are well-known as a key atomic element supporting 1.5 μm band optical technologies and also as complex photoluminescence (PL) band deeply mixing ED and magnetic-dipole (MD) transitions. Here we show large and selective enhancement of ED and MD radiations up to 83- and 26-fold for a reference bulk state, respectively, in experiments employing plasmonic nanocavity arrays. We achieved the marked PL enhancement by use of an optimal design for electromagnetic (EM) local density of states (LDOS) and by Er-ion doping in deep subwavelength precision. We moreover clarify the quantitative contribution of ED and MD radiations to the PL band, and the magnetic Purcell effect in the PL-decay temporal measurement. This study experimentally demonstrates a new scheme of EM-LDOS engineering in plasmon-enhanced photonics, which will be a key technique to develop loss-compensated and active plasmonic devices. PMID:27436631

  12. Correlation of superparamagnetic relaxation with magnetic dipole interaction in capped iron-oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Landers, J.; Stromberg, F.; Darbandi, M.; Schöppner, C.; Keune, W.; Wende, H.

    2015-01-01

    Six nanometer sized iron-oxide nanoparticles capped with an organic surfactant and/or silica shell of various thicknesses have been synthesized by a microemulsion method to enable controllable contributions of interparticle magnetic dipole interaction via tunable interparticle distances. Bare particles with direct surface contact were used as a reference to distinguish between interparticle interaction and surface effects by use of Mössbauer spectroscopy. Superparamagnetic relaxation behaviour was analyzed by SQUID-magnetometry techniques, showing a decrease of the blocking temperature with decreasing interparticle interaction energies kBT0 obtained by AC susceptibility. A many-state relaxation model enabled us to describe experimental Mössbauer spectra, leading to an effective anisotropy constant Keff ≈ 45 kJm-3 in case of weakly interacting particles, consistent with results from ferromagnetic resonance. Our unique multi-technique approach, spanning a huge regime of characteristic time windows from about 10 s to 5 ns, provides a concise picture of the correlation of superparamagnetic relaxation with interparticle magnetic dipole interaction.

  13. Resonant magnetic fields from inflation

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. Uranus' magnetic field and particle drifts in its inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Gao, Shan; Ho, C. Wing; Huang, Tian-Sen; Alexander, Claudia J.

    1998-09-01

    Both the Q3 model (dipole and quadrupole) and OCT model (Q3 plus octupole) of Uranus' magnetic field within 5 RU are expressed in α and β (Euler potentials) coordinate systems. By using the α and β coordinates of magnetic fields, we calculate the drift paths and velocities for the zero second invariant (J=0) charged particles with different total energies. Many aspects of Uranus' magnetic field are similar to those of Neptune [Ho et al., 1997], such as a warped zero magnetic scalar potential surface and a region of local distorted magnetic field lines that gives rise to a large ``open'' area on the planetary surface when the field lines are mapped from this region. It is found that the OCT model gives a map of magnetic field coordinates on the planetary surface that better explains the Voyager 2 ultraviolet spectrometer (UVS) data of Herbert and Sandel [1994] than the Q3 model. The grossly distorted α and β contours on the planetary surface may explain the incomplete aurora circles around both magnetic poles, and weak UV emissions are found lying along a belt that coincides remarkably well with the OCT magnetic equator. In addition, tracing of drift paths of J=0 charged particles shows that the weak emission along the magnetic equator is due to the precipitation of J=0 particles, or particles with a large equatorial pitch angle. In particular, the low-energy J=0 particles tend to drift toward a planet in three concentrated regions where UV emissions are observed.

  19. Chain-induced effects in the Faraday instability on ferrofluids in a horizontal magnetic field

    NASA Astrophysics Data System (ADS)

    Mekhonoshin, V. V.; Lange, Adrian

    2004-04-01

    The linear stability analysis of the Faraday instability on a viscous ferrofluid in a horizontal magnetic field is performed. Strong dipole-dipole interactions lead to the formation of chains elongated in the field direction. The formation of chains results in a qualitative new behavior of the ferrofluid. This new behavior is characterized by a neutral stability curve similar to that observed earlier for Maxwell viscoelastic liquids and causes a significant weakening of the energy dissipation at high frequencies. In the case of a ferrofluid with chains in a horizontal magnetic field, the effective viscosity is anisotropic and depends on the field strength as well as on the wave frequency.

  20. Magnetic field evolution in white dwarfs: The hall effect and complexity of the field

    NASA Technical Reports Server (NTRS)

    Muslimov, A. G.; Van Horn, H. M.; Wood, M. A.

    1995-01-01

    We calculate the evolution of the magnetic fields in white dwarfs, taking into account the Hall effect. Because this effect depends nonlinearly upon the magnetic field strength B, the time dependences of the various multipole field components are coupled. The evolution of the field is thus significantly more complicated than has been indicated by previous investigations. Our calculations employ recent white dwarf evolutionary sequences computed for stars with masses 0.4, 0.6, 0.8, and 1.0 solar mass. We show that in the presence of a strong (up to approximately 10(exp 9) G) internal toroidal magnetic field; the evolution of even the lowest order poloidal modes can be substantially changed by the Hall effect. As an example, we compute the evolution of an initially weak quadrupole component, which we take arbitrarily to be approximately 0.1%-1% of the strength of a dominant dipole field. We find that coupling provided by the Hall effect can produce growth of the ratio of the quadrupole to the dipole component of the surface value of the magnetic field strength by more than a factor of 10 over the 10(exp 9) to 10(exp 10) year cooling lifetime of the white dwarf. Some consequences of these results for the process of magnetic-field evolution in white dwarfs are briefly discussed.

  1. Magnetic fields during galaxy mergers

    NASA Astrophysics Data System (ADS)

    Rodenbeck, Kai; Schleicher, Dominik R. G.

    2016-09-01

    Galaxy mergers are expected to play a central role for the evolution of galaxies and may have a strong effect on their magnetic fields. We present the first grid-based 3D magnetohydrodynamical simulations investigating the evolution of magnetic fields during merger events. For this purpose, we employed a simplified model considering the merger event of magnetized gaseous disks in the absence of stellar feedback and without a stellar or dark matter component. We show that our model naturally leads to the production of two peaks in the evolution of the average magnetic field strength within 5 kpc, within 25 kpc, and on scales in between 5 and 25 kpc. The latter is consistent with the peak in the magnetic field strength previously reported in a merger sequence of observed galaxies. We show that the peak on the galactic scale and in the outer regions is most likely due to geometrical effects, as the core of one galaxy enters the outskirts of the other one. In addition, the magnetic field within the central ~5 kpc is physically enhanced, which reflects the enhancement in density that is due to efficient angular momentum transport. We conclude that high-resolution observations of the central regions will be particularly relevant for probing the evolution of magnetic field structures during merger events.

  2. Bioluminescence under static magnetic fields

    NASA Astrophysics Data System (ADS)

    Iwasaka, M.; Ueno, S.

    1998-06-01

    In the present study, the effect of magnetic fields on the emission of light by a living system was studied. The fireflies Hotaria parvula and Luciola cruciata were used as the bioluminescence systems. The firefly light organ was fixed at the edge of an optical fiber. The emitted light was introduced into a single-channel photon-counting system using an optical fiber. We measured both the spectrum of a constant light emission and, the time course of bioluminescence pulses. Two horizontal-type superconducting magnets, which produced 8 and 14 T magnetic fields at their center, were used as the magnetic-field generators. We also carried out an in vitro study of bioluminescence. The enzymatic activity of luciferase was measured under a 14 T magnetic field. We measured emission spectra of bioluminescence over the interval 500-600 nm at 25 °C in a stable emission state. It was observed that the peak wavelength around 550 nm shifted to 560 nm under a 14 T magnetic field. However, the effects of magnetic fields were not significant. Also, we measured the time course of emissions at 550 nm in a transient emission state. The rate in the light intensity under a 14 T magnetic field increased compared to the control. There is a possibility that the change in the emission intensities under a magnetic field is related to a change in the biochemical systems of the firefly, such as the enzymatic process of luciferase and the excited singlet state with subsequent light emission.

  3. The permanent electric dipole moments and magnetic g(e)-factors of praseodymium monoxide (PrO).

    PubMed

    Wang, Hailing; Linton, Colan; Ma, Tongmei; Steimle, Timothy C

    2009-11-26

    The R(4.5) and P(6.5) branch features of the XX (0, 0) band of praseodymium monoxide (PrO) have been studied at a resolution of approximately 50 MHz field free and in the presence of static electric and magnetic fields. The permanent electric dipole moments, mu(el), of 3.01(6) D and 4.72(5) D for the X(2) (Omega = 4.5) and [18.1] (Omega = 5.5) states, respectively, were determined from the analysis of the Stark spectra. The magnetic g(e)-factors of 4.48(8) and 5.73(6) for the X(2) (Omega = 4.5) and [18.1] (Omega = 5.5) states, respectively, were determined from the analysis of the Zeeman spectra. The g(e)-factors are compared with those computed using wave functions predicted from ligand field theory and ab initio calculations. The mu(el) value for the X(2) (Omega = 4.5) state is compared to ab initio and density functional predicted values and with the experimental values of other lanthanide monoxides.

  4. The magnetic fields of Mercury, Venus and Mars

    NASA Technical Reports Server (NTRS)

    Russell, C. T.

    1981-01-01

    Just as clearly as Mariner 10 established that Mercury has an intrinsic magnetic field, the Pioneer Venus orbiter has established that Venus has no significant intrinsic field. This is perhaps the opposite of what might be expected. Mercury, a small planet, might be expected to cool rapidly and its internal dynamo to cease, while Venus, which is almost as large as the earth, should not have lost much heat. On the contrary the source of energy of the Mercury dynamo appears to be extant whereas that of Venus appears to be extinct. The existence of a Martian magnetic field is controversial. No unambiguous signature of a Martian magnetic field has been reported. If the field on the nightside of Mars is of planetary rather than solar origin the Russian Mars spacecraft observations indicate the Martian dipole lies near the planetary equator rather than its pole.

  5. 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)

  6. Dynamics of Magnetotactic Bacteria in a Rotating Magnetic Field

    PubMed Central

    Ērglis, Kaspars; Wen, Qi; Ose, Velta; Zeltins, Andris; Sharipo, Anatolijs; Janmey, Paul A.; Cēbers, Andrejs

    2007-01-01

    The dynamics of the motile magnetotactic bacterium Magnetospirillum gryphiswaldense in a rotating magnetic field is investigated experimentally and analyzed by a theoretical model. These elongated bacteria are propelled by single flagella at each bacterial end and contain a magnetic filament formed by a linear assembly of ∼40 ferromagnetic nanoparticles. The movements of the bacteria in suspension are analyzed by consideration of the orientation of their magnetic dipoles in the field, the hydrodynamic resistance of the bacteria, and the propulsive force of the flagella. Several novel features found in experiments include a velocity reversal during motion in the rotating field and an interesting diffusive wandering of the trajectory curvature centers. A new method to measure the magnetic moment of an individual bacterium is proposed based on the theory developed. PMID:17526564

  7. Magnetic fields of Mars and Venus - Solar wind interactions

    NASA Technical Reports Server (NTRS)

    Ness, N. F.

    1974-01-01

    Recent USSR studies of the magnetic field and solar wind flow in the vicinity of Mars and Venus confirm earlier U.S. reports of a bow shock wave developed as the solar wind interacts with these planets. Mars 2 and 3 magnetometer experiments report the existence of an intrinsic planetary magnetic field, sufficiently strong to form a magnetopause, deflecting the solar wind around the planet and its ionosphere. This is in contrast to the case for Venus, where it is assumed to be the ionosphere and processes therein which are responsible for the solar wind deflection. An empirical relationship appears to exist between planetary dipole magnetic moments and their angular momentum for the Moon, Mars, Venus, Earth, and Jupiter. Implications for the magnetic fields of Mercury and Saturn are discussed.

  8. 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.

  9. Optical force on toroidal nanostructures: Toroidal dipole versus renormalized electric dipole

    NASA Astrophysics Data System (ADS)

    Zhang, Xu-Lin; Wang, S. B.; Lin, Zhifang; Sun, Hong-Bo; Chan, C. T.

    2015-10-01

    We study the optical forces acting on toroidal nanostructures. A great enhancement of optical force is unambiguously identified as originating from the toroidal dipole resonance based on the source representation, where the distribution of the induced charges and currents is characterized by the three families of electric, magnetic, and toroidal multipoles. On the other hand, the resonant optical force can also be completely attributed to an electric dipole resonance in the alternative field representation, where the electromagnetic fields in the source-free region are expressed by two sets of electric and magnetic multipole fields based on symmetry. The confusion is resolved by conceptually introducing the irreducible electric dipole, toroidal dipole, and renormalized electric dipole. We demonstrate that the optical force is a powerful tool to identify toroidal response even when its scattering intensity is dwarfed by the conventional electric and magnetic multipoles.

  10. No contact terms for the magnetic field in Lorentz- and CPT-violating electrodynamics

    NASA Astrophysics Data System (ADS)

    Schober, Karl; Altschul, Brett

    2016-09-01

    In a Lorentz- and CPT-violating modification of electrodynamics, the fields of a moving charge are known to have unusual singularities. This raises the question of whether the singular behavior may include δ-function contact terms, similar to those that appear in the fields of idealized dipoles. However, by calculating the magnetic field of an infinite straight wire in this theory, we demonstrate that there are no such contact terms in the magnetic field of a moving point charge.

  11. Molecular near-field antenna effect in resonance hyper-Raman scattering: Intermolecular vibronic intensity borrowing of solvent from solute through dipole-dipole and dipole-quadrupole interactions

    NASA Astrophysics Data System (ADS)

    Shimada, Rintaro; Hamaguchi, Hiro-o.

    2014-05-01

    We quantitatively interpret the recently discovered intriguing phenomenon related to resonance Hyper-Raman (HR) scattering. In resonance HR spectra of all-trans-β-carotene (β-carotene) in solution, vibrations of proximate solvent molecules are observed concomitantly with the solute β-carotene HR bands. It has been shown that these solvent bands are subject to marked intensity enhancements by more than 5 orders of magnitude under the presence of β-carotene. We have called this phenomenon the molecular-near field effect. Resonance HR spectra of β-carotene in benzene, deuterated benzene, cyclohexane, and deuterated cyclohexane have been measured precisely for a quantitative analysis of this effect. The assignments of the observed peaks are made by referring to the infrared, Raman, and HR spectra of neat solvents. It has been revealed that infrared active and some Raman active vibrations are active in the HR molecular near-field effect. The observed spectra in the form of difference spectra (between benzene/deuterated benzene and cyclohexane/deuterated cyclohexane) are quantitatively analyzed on the basis of the extended vibronic theory of resonance HR scattering. The theory incorporates the coupling of excited electronic states of β-carotene with the vibrations of a proximate solvent molecule through solute-solvent dipole-dipole and dipole-quadrupole interactions. It is shown that the infrared active modes arise from the dipole-dipole interaction, whereas Raman active modes from the dipole-quadrupole interaction. It is also shown that vibrations that give strongly polarized Raman bands are weak in the HR molecular near-field effect. The observed solvent HR spectra are simulated with the help of quantum chemical calculations for various orientations and distances of a solvent molecule with respect to the solute. The observed spectra are best simulated with random orientations of the solvent molecule at an intermolecular distance of 10 Å.

  12. Characterization of magnetic nanoparticles using programmed quadrupole magnetic field-flow fractionation

    PubMed Central

    Williams, P. Stephen; Carpino, Francesca; Zborowski, Maciej

    2010-01-01

    Quadrupole magnetic field-flow fractionation is a relatively new technique for the separation and characterization of magnetic nanoparticles. Magnetic nanoparticles are often of composite nature having a magnetic component, which may be a very finely divided material, and a polymeric or other material coating that incorporates this magnetic material and stabilizes the particles in suspension. There may be other components such as antibodies on the surface for specific binding to biological cells, or chemotherapeutic drugs for magnetic drug delivery. Magnetic field-flow fractionation (MgFFF) has the potential for determining the distribution of the magnetic material among the particles in a given sample. MgFFF differs from most other forms of field-flow fractionation in that the magnetic field that brings about particle separation induces magnetic dipole moments in the nanoparticles, and these potentially can interact with one another and perturb the separation. This aspect is examined in the present work. Samples of magnetic nanoparticles were analysed under different experimental conditions to determine the sensitivity of the method to variation of conditions. The results are shown to be consistent and insensitive to conditions, although magnetite content appeared to be somewhat higher than expected. PMID:20732895

  13. Characterization of magnetic nanoparticles using programmed quadrupole magnetic field-flow fractionation.

    PubMed

    Williams, P Stephen; Carpino, Francesca; Zborowski, Maciej

    2010-09-28

    Quadrupole magnetic field-flow fractionation is a relatively new technique for the separation and characterization of magnetic nanoparticles. Magnetic nanoparticles are often of composite nature having a magnetic component, which may be a very finely divided material, and a polymeric or other material coating that incorporates this magnetic material and stabilizes the particles in suspension. There may be other components such as antibodies on the surface for specific binding to biological cells, or chemotherapeutic drugs for magnetic drug delivery. Magnetic field-flow fractionation (MgFFF) has the potential for determining the distribution of the magnetic material among the particles in a given sample. MgFFF differs from most other forms of field-flow fractionation in that the magnetic field that brings about particle separation induces magnetic dipole moments in the nanoparticles, and these potentially can interact with one another and perturb the separation. This aspect is examined in the present work. Samples of magnetic nanoparticles were analysed under different experimental conditions to determine the sensitivity of the method to variation of conditions. The results are shown to be consistent and insensitive to conditions, although magnetite content appeared to be somewhat higher than expected.

  14. Multidirectional colloidal assembly in concurrent electric and magnetic fields.

    PubMed

    Bharti, Bhuvnesh; Kogler, Florian; Hall, Carol K; Klapp, Sabine H L; Velev, Orlin D

    2016-10-01

    Dipolar interactions between nano- and micron sized colloids lead to their assembly into domains with well-defined local order. The particles with a single dipole induced by an external field assemble into linear chains and clusters. However, to achieve the formation of multidirectionally organized nano- or microassemblies with tunable physical characteristics, more sophisticated interaction tools are needed. Here we demonstrate that such complex interactions can be introduced in the form of two independent, non-interacting dipoles (double-dipoles) within a microparticle. We show how this can be achieved by the simultaneous application of alternating current (AC)-electric field and uniform magnetic field to dispersions of superparamagnetic microspheres. Depending on their timing and intensity, concurrent electric and magnetic fields lead to the formation of bidirectional particle chains, colloidal networks, and discrete crystals. We investigate the mechanistic details of the assembly process, and identify and classify the non-equilibrium states formed. The morphologies of different experimental states are in excellent correlation with our theoretical predictions based on Brownian dynamics simulations combined with a structural analysis based on local energy parameters. This novel methodology of introducing and interpreting double-dipolar particle interactions may assist in the assembly of colloidal coatings, dynamically reconfigurable particle networks, and bidirectional active structures.

  15. Multidirectional colloidal assembly in concurrent electric and magnetic fields.

    PubMed

    Bharti, Bhuvnesh; Kogler, Florian; Hall, Carol K; Klapp, Sabine H L; Velev, Orlin D

    2016-10-01

    Dipolar interactions between nano- and micron sized colloids lead to their assembly into domains with well-defined local order. The particles with a single dipole induced by an external field assemble into linear chains and clusters. However, to achieve the formation of multidirectionally organized nano- or microassemblies with tunable physical characteristics, more sophisticated interaction tools are needed. Here we demonstrate that such complex interactions can be introduced in the form of two independent, non-interacting dipoles (double-dipoles) within a microparticle. We show how this can be achieved by the simultaneous application of alternating current (AC)-electric field and uniform magnetic field to dispersions of superparamagnetic microspheres. Depending on their timing and intensity, concurrent electric and magnetic fields lead to the formation of bidirectional particle chains, colloidal networks, and discrete crystals. We investigate the mechanistic details of the assembly process, and identify and classify the non-equilibrium states formed. The morphologies of different experimental states are in excellent correlation with our theoretical predictions based on Brownian dynamics simulations combined with a structural analysis based on local energy parameters. This novel methodology of introducing and interpreting double-dipolar particle interactions may assist in the assembly of colloidal coatings, dynamically reconfigurable particle networks, and bidirectional active structures. PMID:27537850

  16. Dynamos and cosmic magnetic fields.

    NASA Astrophysics Data System (ADS)

    Kulsrud, R.; Cowley, S. C.; Gruzinov, A. V.; Sudan, R. N.

    1997-04-01

    This paper discusses the origin of the galactic magnetic field. The theory of the mean field dynamo in the interstellar medium is reviewed and shown to be flawed because it ignores the strong amplification of small-scale magnetic fields. An alternative origin is offered. It is proposed that the galactic fields are created in the protogalaxy by protogalactic turbulence. It is shown that they are first created from zero by the turbulence through the Biermann battery mechanism. The resulting weak seed fields are then amplified by the dynamo action of the protogalactic turbulence up to a field strength adequate for a primordial field origin of the galactic magnetic field. It is suggested that the amplification of the small-scale fields, that are a problem for the interstellar origin, are suppressed in the protogalaxy by collisionless processes that act on scales smaller than the mean free path. Since the relative size of the mean free path is quite large in the protogalaxy, the dynamo would generate only large-scale fields. After compression this field could become the galactic field. It is possible that no further amplification of it need occur in the interstellar medium.

  17. Limits on the possible intrinsic magnetic field of Venus

    NASA Technical Reports Server (NTRS)

    Russell, C. T.; Elphic, R. C.; Slavin, J. A.

    1980-01-01

    Magnetic field measurements obtained by the Pioneer Venus orbiter at low altitudes in the solar wind wake region are examined for possible surface-correlated features and any possible intrinsic magnetic moment. The field variations observed in the wake do not resemble those expected for a solar wind interaction with even a weak intrinsic magnetic field. Little orbit-to-orbit persistence of features is found in the magnetic records. The magnetic field measurements in the wake are averaged in 10 deg x 10 deg bins to minimize the effects of external field sources. In these 37 bins, the average fields appear to be randomly oriented and consistent with zero mean in the region mapped. Using these 37 averaged vector fields, a maximum intrinsic magnetic dipole moment is obtained of 4.3 + or - 2.0 x 10 to the 21st G cu cm, approximately an order of magnitude less than previous estimates. It is noted that a more conservative estimate of the probable error of the mean is 5.5 x 10 to the 21st G cu cm. The Pioneer Venus measurements are thus consistent with zero planetary moment. The present measurements are found to be far below estimates made on the basis of angular momentum, the so-called magnetic Bode's law, and far below the dynamo scaling law of Busse.

  18. Extremely large extinction efficiency and field enhancement in terahertz resonant dipole nanoantennas.

    PubMed

    Razzari, Luca; Toma, Andrea; Shalaby, Mostafa; Clerici, Matteo; Zaccaria, Remo Proietti; Liberale, Carlo; Marras, Sergio; Al-Naib, Ibraheem A I; Das, Gobind; De Angelis, Francesco; Peccianti, Marco; Falqui, Andrea; Ozaki, Tsuneyuki; Morandotti, Roberto; Di Fabrizio, Enzo

    2011-12-19

    The distinctive ability of nanometallic structures to manipulate light at the nanoscale has recently promoted their use for a spectacular set of applications in a wide range of areas of research including artificial optical materials, nano-imaging, biosensing, and nonlinear optics. Here we transfer this concept to the terahertz spectral region, demonstrating a metal nanostructure in shape of a dipole nanoantenna, which can efficiently resonate at terahertz frequencies, showing an effective cross section >100 times larger than its geometrical area, and a field enhancement factor of ~280, confined on a lateral section of ~λ/1,000. These results lead to immediate applications in terahertz artificial materials exhibiting giant dichroism, suggest the use of dipole nanoantennas in nanostructure-based terahertz metamaterials, and pave the way for nanoantenna-enhanced terahertz few-molecule spectroscopy and localized terahertz nonlinear optics.

  19. The Galilean satellites and the Jovian magnetic field

    NASA Technical Reports Server (NTRS)

    Freeman, J. W.

    1978-01-01

    Alfven and Arrhenius (1974, 1976) have proposed that satellites may be formed by the condensation of plasma in partial corrotation in the dipole magnetic field of the central body. They conclude that the final orbit distance of the condensed material will be two-thirds of the orbit distance of the plasma. Since the Jovian field is strongly distorted beyond about 40 Jupiter radii, it is expected (assuming that plasma and magnetic field conditions have not changed significantly with time) that the first Galilean satellites would appear at about two-thirds 40 Jupiter radii or about 27 Jupiter radii. In fact Callisto, the outermost Galilean satellite, is found at 26.47 Jupiter radii. This generally supports the Alfven-Arrhenius hypothesis that the central-body dipolar magnetic field plays a role in major satellite formation and, more, specifically, that the two-thirds law has validity.

  20. 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

  1. Dipolar polaritons in microcavity-embedded coupled quantum wells in electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Wilkes, J.; Muljarov, E. A.

    2016-09-01

    We present a microscopic calculation of spatially indirect exciton states in semiconductor coupled quantum wells and polaritons formed from their coupling to the optical mode of a microcavity. We include the presence of electric and magnetic fields applied perpendicular to the quantum well plane. Our model predicts the existence of polaritons that are in the strong-coupling regime and at the same time possess a large static dipole moment. We demonstrate, in particular, that a magnetic field can compensate for the reduction in light-matter coupling that occurs when an electric field impresses a dipole moment on the polariton.

  2. Systematics of magnetic dipole strength in the stable even-mass Mo isotopes

    NASA Astrophysics Data System (ADS)

    Rusev, G.; Schwengner, R.; Dönau, F.; Erhard, M.; Frauendorf, S.; Grosse, E.; Junghans, A. R.; Käubler, L.; Kosev, K.; Kostov, L. K.; Mallion, S.; Schilling, K. D.; Wagner, A.; Garrel, H. Von; Kneissl, U.; Kohstall, C.; Kreutz, M.; Pitz, H. H.; Scheck, M.; Stedile, F.; Brentano, P. Von; Fransen, C.; Jolie, J.; Linnemann, A.; Pietralla, N.; Werner, V.

    2006-04-01

    The nuclides Mo92, Mo98, and Mo100 have been studied in photon-scattering experiments by using bremsstrahlung produced at an electron energy of 6 MeV at the ELBE accelerator of the Forschungszentrum Rossendorf and at electron energies from 3.2 to 3.8 MeV at the Dynamitron accelerator at the University of Stuttgart. Six dipole transitions in Mo98 and 19 in Mo100 were observed for the first time in the energy range from 2 to 4 MeV. The experimental results are compared with predictions of the shell model and with predictions of the quasiparticle random-phase approximation (QRPA) in a deformed basis. The latter show significant contributions of isovector-orbital and isovector-spin vibrations. The change of the magnetic dipole strength in the isotopic chain of the even-mass isotopes from Mo92 to Mo100 is discussed. The calculations within the QRPA are extrapolated to the particle-separation energies to estimate the possible influence of M1 strength on the stability of the nuclides against photodissociation in cosmic scenarios.

  3. Hyperfine-induced electric dipole contributions to the electric octupole and magnetic quadrupole atomic clock transitions

    NASA Astrophysics Data System (ADS)

    Dzuba, V. A.; Flambaum, V. V.

    2016-05-01

    Hyperfine-induced electric dipole contributions may significantly increase probabilities of otherwise very weak electric octupole and magnetic quadrupole atomic clock transitions (e.g., transitions between s and f electron orbitals). These transitions can be used for exceptionally accurate atomic clocks, quantum information processing, and the search for dark matter. They are very sensitive to new physics beyond the standard model, such as temporal variation of the fine-structure constant, the Lorentz invariance, and Einstein equivalence principle violation. We formulate conditions under which the hyperfine-induced electric dipole contribution dominates and perform calculations of the hyperfine structure and E3, M2 and the hyperfine-induced E1 transition rates for a large number of atoms and ions of experimental interest. Due to the hyperfine quenching the electric octupole clock transition in +173Yb is 2 orders of magnitude stronger than that in currently used +171Yb. Some enhancement is found in 13+143Nd, 14+149Pm, 14+147Sm, and 15+147Sm ions.

  4. Magnetic fields in ring galaxies

    NASA Astrophysics Data System (ADS)

    Moss, D.; Mikhailov, E.; Silchenko, O.; Sokoloff, D.; Horellou, C.; Beck, R.

    2016-07-01

    Context. Many galaxies contain magnetic fields supported by galactic dynamo action. The investigation of these magnetic fields can be helpful for understanding galactic evolution; however, nothing definitive is known about magnetic fields in ring galaxies. Aims: Here we investigate large-scale magnetic fields in a previously unexplored context, namely ring galaxies, and concentrate our efforts on the structures that appear most promising for galactic dynamo action, i.e. outer star-forming rings in visually unbarred galaxies. Methods: We use tested methods for modelling α-Ω galactic dynamos, taking into account the available observational information concerning ionized interstellar matter in ring galaxies. Results: Our main result is that dynamo drivers in ring galaxies are strong enough to excite large-scale magnetic fields in the ring galaxies studied. The variety of dynamo driven magnetic configurations in ring galaxies obtained in our modelling is much richer than that found in classical spiral galaxies. In particular, various long-lived transients are possible. An especially interesting case is that of NGC 4513, where the ring counter-rotates with respect to the disc. Strong shear in the region between the disc and the ring is associated with unusually strong dynamo drivers in such counter-rotators. The effect of the strong drivers is found to be unexpectedly moderate. With counter-rotation in the disc, a generic model shows that a steady mixed parity magnetic configuration that is unknown for classical spiral galaxies, may be excited, although we do not specifically model NGC 4513. Conclusions: We deduce that ring galaxies constitute a morphological class of galaxies in which identification of large-scale magnetic fields from observations of polarized radio emission, as well as dynamo modelling, may be possible. Such studies have the potential to throw additional light on the physical nature of rings, their lifetimes, and evolution.

  5. Field quality measurements of Fermilab Nb(3)Sn common coil dipole model

    SciTech Connect

    Kashikhin, V.S.; Andreev, N.; Dimarco, J.; Feher, S.; Kashikhin, V.V.; Lamm, M.; Novitski, I.; Orris, D.; Schlabach, P.; Sylvester, C.; Tartaglia, M.; Velev, G.; Zlobin, A.V.; Fermilab

    2003-11-01

    A short model of single-layer Nb{sub 3}Sn common coil magnet has been fabricated and is being tested at Fermilab. This paper summarizes results of magnetic measurements in this model. The geometrical harmonics, coil magnetization and iron saturation effects, ramp-rate dependence, field decay and the ''snap-back'' effect at injection are presented.

  6. Magnetic fields in spiral galaxies

    SciTech Connect

    Beck, R. )

    1990-02-01

    Radio polarization observations have revealed large-scale magnetic fields in spiral galaxies. The average total field strength most probably increases with the rate of star formation. The uniform field generally follows the orientation of the optical spiral arms, but is often strongest {ital outside} the arms. Long magnetic-field filaments are seen, sometimes up to a 30 kpc length. The field seems to be anchored in large gas clouds and is inflated out of the disk; e.g., by a galactic wind. The field in radio halos around galaxies is highly uniform in limited regions, resembling the structure of the solar corona. The detection of Faraday rotation in spiral galaxies excludes the existence of large amounts of antimatter. The distribution of Faraday rotation in the disks shows two different large-scale structures of the interstellar field: Axisymmetric-spiral and bisymmetric-spiral, which are interpreted as two modes of the galactic dynamo driven by differential rotation.

  7. 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.

  8. Measurement of untruncated nuclear spin interactions via zero- to ultralow-field nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Blanchard, J. W.; Sjolander, T. F.; King, J. P.; Ledbetter, M. P.; Levine, E. H.; Bajaj, V. S.; Budker, D.; Pines, A.

    2015-12-01

    Zero- to ultralow-field nuclear magnetic resonance (ZULF NMR) provides a new regime for the measurement of nuclear spin-spin interactions free from the effects of large magnetic fields, such as truncation of terms that do not commute with the Zeeman Hamiltonian. One such interaction, the magnetic dipole-dipole coupling, is a valuable source of spatial information in NMR, though many terms are unobservable in high-field NMR, and the coupling averages to zero under isotropic molecular tumbling. Under partial alignment, this information is retained in the form of so-called residual dipolar couplings. We report zero- to ultralow-field NMR measurements of residual dipolar couplings in acetonitrile-2-13C aligned in stretched polyvinyl acetate gels. This permits the investigation of dipolar couplings as a perturbation on the indirect spin-spin J coupling in the absence of an applied magnetic field. As a consequence of working at zero magnetic field, we observe terms of the dipole-dipole coupling Hamiltonian that are invisible in conventional high-field NMR. This technique expands the capabilities of zero- to ultralow-field NMR and has potential applications in precision measurement of subtle physical interactions, chemical analysis, and characterization of local mesoscale structure in materials.

  9. Mercury's Internal Magnetic Field: Results from MESSENGER's Search for Remanent Crustal Magnetization Associated with Impact Basins

    NASA Astrophysics Data System (ADS)

    Purucker, M. E.; Johnson, C. L.; Nicholas, J. B.; Philpott, L. C.; Korth, H.; Anderson, B. J.; Head, J. W., III; Phillips, R. J.; Solomon, S. C.

    2014-12-01

    Magnetic field measurements obtained by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft in orbit around Mercury have entered a new phase since April 2014, with periapsis altitudes below 200 km. MESSENGER is now obtaining magnetic profiles across large impact features at altitudes less than the horizontal scale of those features. We use data from this latest phase to investigate evidence for remanent crustal magnetization specifically associated with impact basins and large craters. The spatial resolution of magnetic field measurements for investigating crustal magnetization is approximately equal to the altitude of the observations. We focus on large impact features because their relative ages provide a powerful chronological tool for interpreting any associated magnetic signatures. We examine profiles across large impact basins such as Caloris, Shakespeare, Budh-Sobkou and Goethe. For example, coverage over Caloris during the last year of the mission will be largely at night and will comprise 18 profiles with altitudes between 125 and 200 km and 12 profiles with altitudes between 50 and 125 km over the northern part of the basin. We use large-scale magnetospheric models developed with MESSENGER data to remove contributions from the offset axial dipole, magnetopause, and magnetotail. The residual magnetic fields above 200 km are still dominated by poorly understood magnetospheric fields such as those from the cusp and from Birkeland currents. We empirically average, or exclude observations from these local times, in order to search for repeatable internal field signals. We use local basis functions such as equivalent source dipoles, applied with regularization tools, in order to map the altitude-normalized magnetic field from internal sources. These internal sources may comprise both crustal and core contributions, and we use the information from the along-track magnetic gradient in order to separate these contributions.

  10. Dipole Well Location

    1998-08-03

    The problem here is to model the three-dimensional response of an electromagnetic logging tool to a practical situation which is often encountered in oil and gas exploration. The DWELL code provide the electromagnetic fields on the axis of a borehole due to either an electric or a magnetic dipole located on the same axis. The borehole is cylindrical, and is located within a stratified formation in which the bedding planes are not horizontal. The anglemore » between the normal to the bedding planes and the axis of the borehole may assume any value, or in other words, the borehole axis may be tilted with respect to the bedding planes. Additionally, all of the formation layers may have invasive zones of drilling mud. The operating frequency of the source dipole(s) extends from a few Hertz to hundreds of Megahertz.« less

  11. Magnetic fields and coronal heating

    NASA Technical Reports Server (NTRS)

    Golub, L.; Maxson, C.; Rosner, R.; Vaiana, G. S.; Serio, S.

    1980-01-01

    General considerations concerning the scaling properties of magnetic-field-related coronal heating mechanisms are used to build a two-parameter model for the heating of closed coronal regions. The model predicts the way in which coronal temperature and electron density are related to photospheric magnetic field strength and the size of the region, using the additional constraint provided by the scaling law of Rosner, Tucker, and Vaiana. The model duplicates the observed scaling of total thermal energy content with total longitudinal flux; it also predicts a relation between the coronal energy density (or pressure) and the longitudinal field strength modified by the region scale size.

  12. External dc bias field effects in the nonlinear ac stationary response of permanent dipoles in a uniaxial potential

    NASA Astrophysics Data System (ADS)

    Wei, Nijun; Coffey, William T.; Déjardin, Pirre-Michel; Kalmykov, Yuri P.

    External dc bias field effects on the nonlinear dielectric relaxation and dynamic Kerr effect of a system of permanent dipoles in a uniaxial mean field potential are studied via the rotational Brownian motion model. Postulated in terms of the infinite hierarchy of differential-recurrence equations for the statistical moments (the expectation value of the Legendre polynomials), the dielectric and Kerr effect ac stationary responses may be evaluated for arbitrary dc bias field strength via perturbation theory in the ac field. We have given two complementary approaches for treating the nonlinear effects. The first is based on perturbation theory allowing one to calculate the nonlinear ac stationary responses using powerful matrix methods. The second approach based on the accurate two-mode approximation [D.A. Garanin, Phys. Rev. E. 54, 3250 (1996)] effectively generalizes the existing results for dipolar systems in superimposed ac and dc fields to a mean field potential. The results apply both to nonlinear dielectric relaxation and dynamic Kerr effect of nematics and to magnetic birefringence relaxation of ferrofluids. Furthermore, the given methods of the solution of infinite hierarchies of multi-term recurrence relations are quite general and can be applied to analogous nonlinear response problems.

  13. Electric and magnetic dipole excitations to bound states in 70,72,74,76Ge

    NASA Astrophysics Data System (ADS)

    Jung, A.; Lindenstruth, S.; Schacht, H.; Starck, B.; Stock, R.; Wesselborg, C.; Heil, R. D.; Kneissl, U.; Margraf, J.; Pitz, H. H.; Steiper, F.

    1995-02-01

    The nuclei 70,72,74,76Ge were studied by nuclear resonance fluorescence (NRF) experiments. Partially linearly polarized and unpolarized bremsstrahlung of 9 to 14 MeV endpoint energy was used at the Giessen 65 MeV electron linear accelerator; unpolarized bremsstrahlung of 4 MeV endpoint energy was used at the Stuttgart Dynamitron. The scattered photons were detected by Ge γ-ray spectrometers with high energy resolution. Multipolarities were determined by measuring the angular correlations between the beam and the scattered γ rays at different scattering angles. Precise excitation energies and ground-state decay widths of numerous (> 120) previously unknown spin-1 states were extracted. For 65 ground-state transitions (20 M1 transitions, 45 E1 transitions) parities were assigned, in a model-independent way, by polarized bremsstrahlung. A detailed distribution of electric and magnetic dipole strength in the even Ge isotopes was established.

  14. Magnetic-dipole transitions in highly charged ions as a basis of ultraprecise optical clocks.

    PubMed

    Yudin, V I; Taichenachev, A V; Derevianko, A

    2014-12-01

    We evaluate the feasibility of using magnetic-dipole (M1) transitions in highly charged ions as a basis of an optical atomic clockwork of exceptional accuracy. We consider a range of possibilities, including M1 transitions between clock levels of the same fine-structure and hyperfine-structure manifolds. In highly charged ions these transitions lie in the optical part of the spectra and can be probed with lasers. The most direct advantage of our proposal comes from the low degeneracy of clock levels and the simplicity of atomic structure in combination with negligible quadrupolar shift. We demonstrate that such clocks can have projected fractional accuracies below the 10^{-20}-10^{-21} level for all common systematic effects, such as blackbody radiation, Zeeman, ac-Stark, and quadrupolar shifts.

  15. Alternate manufacturing processes and materials for the SSC dipole magnet coil end parts

    SciTech Connect

    Lipski, A.; Bossert, R.; Brandt, J.; Hoffman, J.; Kobliska, G.; Zweibohmer, J.; Higinbotham, W.; Shields, R.; Sims, R.

    1992-04-01

    Modern magnet designs such as the SSC dipole utilize smaller bore diameter and wider superconducting cable. Challenging winding techniques place greater emphasis on the role of the coil end parts. Their complex configuration is derived from their function of confining the conductors to a consistent given shape and location. Present end parts, made of G-10 composite, are manufactured utilizing complex and expensive 5-axis machining techniques. Several alternate manufacturing processes and materials described in this paper will result in a substantial cost reduction for mass producing the end parts. The alternate processes are divided into two major groups. The composite group consists of Resin Transfer Molding (RAM), Compound Transfer Mold (CAM), Injection Molded Composite (IMP) and Compression Molded Composite (CC). The base metal coated group consists of Chemical Vapor Deposition (CAD) dip coating and hard coatings/anodizing. The paper will provide an overview of the various processes and compare test performance and cost to that of the process currently used.

  16. Magnetic-dipole transitions in highly charged ions as a basis of ultraprecise optical clocks.

    PubMed

    Yudin, V I; Taichenachev, A V; Derevianko, A

    2014-12-01

    We evaluate the feasibility of using magnetic-dipole (M1) transitions in highly charged ions as a basis of an optical atomic clockwork of exceptional accuracy. We consider a range of possibilities, including M1 transitions between clock levels of the same fine-structure and hyperfine-structure manifolds. In highly charged ions these transitions lie in the optical part of the spectra and can be probed with lasers. The most direct advantage of our proposal comes from the low degeneracy of clock levels and the simplicity of atomic structure in combination with negligible quadrupolar shift. We demonstrate that such clocks can have projected fractional accuracies below the 10^{-20}-10^{-21} level for all common systematic effects, such as blackbody radiation, Zeeman, ac-Stark, and quadrupolar shifts. PMID:25526127

  17. Correlation of superconductor strand, cable and dipole critical currents in ISABELLE magnets

    SciTech Connect

    Tannenbaum, M.J.; Garber, M.; Sampson, W.B.

    1982-01-01

    A calibration between vendor critical current data for 0.0268'' diameter superconductor strand supplied to Fermilab, and the BNL 10/sup -12/ OMEGA cm critical current specification is presented. Vendor critical current data for over 400 Fermilab type billets are shown, both as supplied by the vendor and converted to BNL units. Predictions of cable critical current are made using the sum of the critical currents of the 23 strands, where all strands from the same half billet are assigned the same critical current. The measured cable critical current shows excellent correlation to the predicted value and is approximately 14 +- 2% below it. ISABELLE full length dipoles reach the conductor critical current limit, essentially without training. Magnet performance is predictable from the measured critical current of a short sample of cable to within 2%.

  18. Modeling Earth's magnetic field variation

    NASA Astrophysics Data System (ADS)

    Wardinski, I.

    2012-12-01

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

  19. Magnetic field studies by voyager 2: preliminary results at saturn.

    PubMed

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

    1982-01-29

    Further studies of the Saturnian magnetosphere and planetary magnetic field by Voyager 2 have substantiated the earlier results derived from Voyager 1 observations in 1980. The magnetic field is primarily that of a centered dipole (moment = 0.21 gauss-RS(3); where one Saturn radius, RS, is 60,330 kilometers) tilted approximately 0.8 degrees from the rotation axis. Near closest approach to Saturn, Voyager 2 traversed a kronographic longitude and latitude range that was complementary to that of Voyager 1. Somewhat surprisingly, no evidence was found in the data or the analysis for any large-scale magnetic anomaly in the northern hemisphere which could be associated with the periodic modulation of Saturnian kilometric radiation radio emissions. Voyager 2 crossed the magnetopause of a relatively compressed Saturnian magnetosphere at 18.5 RS while inbound near the noon meridian. Outbound, near the dawn meridian, the magnetosphere had expanded considerably and the magnetopause boundary was not observed until the spacecraft reached 48.4 to 50.9 RS and possibly beyond. Throughout the outbound magnetosphere passage, a period of 46 hours (4.5 Saturn rotations), the field was relatively steady and smooth showing no evidence for any azimuthal asymmetry or magnetic anomaly in the planetary field. We are thus left with a rather enigmatic situation to understand the basic source of Saturnian kilometric radiation modulation, other than the small dipole tilt.

  20. Alkali-vapor magnetic resonance driven by fictitious radiofrequency fields

    SciTech Connect

    Zhivun, Elena; Wickenbrock, Arne; Patton, Brian; Budker, Dmitry

    2014-11-10

    We demonstrate an all-optical {sup 133}Cs scalar magnetometer, operating in nonzero magnetic field, in which the magnetic resonance is driven by an effective oscillating magnetic field provided by the AC Stark shift of an intensity-modulated laser beam. We achieve a projected shot-noise-limited sensitivity of 1.7fT/√(Hz) and measure a technical noise floor of 40fT/√(Hz). These results are essentially identical to a coil-driven scalar magnetometer using the same setup. This all-optical scheme offers advantages over traditional coil-driven magnetometers for use in arrays and in magnetically sensitive fundamental physics experiments, e.g., searches for a permanent electric dipole moment of the neutron.

  1. Magnetic field of the planet Uranus: predictions, measurements, and interpretation

    SciTech Connect

    Dolginov, S.S.

    1987-09-01

    The magnitude and tilt of the eccentric dipole of Uranus are examined in the framework of a processing dynamo model. It is shown that the unique parameters of the magnetic field of Uranus are connected with the fact that, unlike the other planets, the magnetic field of Uranus is generated in two bordering regions whose highly conducting materials differ sharply in density: the density anti rho = 12 g x cm/sup -3/ in a core with an upper boundary r = 0.3R/sub U/, and anti rho = 3.1 g x cm/sup -3/ in an ocean with an upper boundary r = 0.6R/sub U/. The upper boundary of the magnetically active region in the ocean is determined by the magnetic pressure P = 1.9 Mbar, at which the ocean material is metallized.

  2. Magnetic Field Generation and Zonal Flows in the Gas Giants

    NASA Astrophysics Data System (ADS)

    Duarte, L.; Wicht, J.; Gastine, T.

    2013-12-01

    The surface dynamics of Jupiter and Saturn is dominated by a banded system of fierce zonal winds. The depth of these winds remains unclear but they are thought to be confined to the very outer envelopes where hydrogen remains molecular and the electrical conductivity is negligible. The dynamo responsible for the dipole dominated magnetic fields of both Gas Giants, on the other hand, likely operates in the deeper interior where hydrogen assumes a metallic state. We present numerical simulations that attempt to model both the zonal winds and the interior dynamo action in an integrated approach. Using the anelastic version of the MHD code MagIC, we explore the effects of density stratification and radial electrical conductivity variations. The electrical conductivity is assumed to remain constant in the thicker inner metallic region and decays exponentially towards the outer boundary throughout the molecular envelope. Our results show that the combination of stronger density stratification (Δρ≈55) and a weaker conducting outer layer is essential for reconciling dipole dominated dynamo action and a fierce equatorial zonal jet. Previous simulations with homogeneous electrical conductivity show that both are mutually exclusive, with solutions either having strong zonal winds and multipolar magnetic fields or weak zonal winds and dipole dominated magnetic fields. The particular setup explored here allows the equatorial jet to remain confined to the weaker conducting region where is does not interfere with the deeper seated dynamo action. The equatorial jet can afford to remain geostrophic and reaches throughout the whole shell. This is not an option for the additional mid to higher latitude jets, however. In dipole dominated dynamo solutions, appropriate for the Gas Giants, zonal flows remain very faint in the deeper dynamo region but increase in amplitude in the weakly conducting outer layer in some of our simulations. This suggests that the mid to high latitude jets

  3. Low-temperature magnetization dynamics of magnetic molecular solids in a swept field

    SciTech Connect

    Lenferink, Erik; Vijayaraghavan, Avinash; Garg, Anupam

    2015-05-15

    The swept-field experiments on magnetic molecular solids such as Fe{sub 8} are studied using Monte Carlo simulations, and a kinetic equation developed to understand collective magnetization phenomena in such solids, where the collective aspects arise from dipole–dipole interactions between different molecules. Because of these interactions, the classic Landau–Zener–Stückelberg theory proves inadequate, as does another widely used model constructed by Kayanuma. It is found that the simulations provide a quantitatively accurate account of the experiments. The kinetic equation provides a similarly accurate account except at very low sweep velocities, where it fails modestly. This failure is attributed to the neglect of short-range correlations between the dipolar magnetic fields seen by the molecular spins. The simulations and the kinetic equation both provide a good understanding of the distribution of these dipolar fields, although analytic expressions for the final magnetization remain elusive.

  4. Magnetic dipole bands in {sup 82}Rb, {sup 83}Rb and {sup 84}Rb

    SciTech Connect

    Schwengner, R.; Schnare, H.; Frauendorf, S.; Doenau, F.; Kaeubler, L.; Prade, H.; Grosse, E.; Jungclaus, A.; Lieb, K. P.; Lingk, C.; Skoda, S.; Eberth, J.; De Angelis, G.; Gadea, A.; Farnea, E.; Napoli, D. R.; Ur, C. A.; Lo Bianco, G.

    1998-12-21

    We have studied the isotopes {sup 82}Rb{sub 45}, {sup 83}Rb{sub 46} and {sup 84}Rb{sub 47} to search for magnetic rotation which is predicted in the tilted-axis cranking model for a certain mass region around A=80. Excited states in these nuclei were populated via the reaction {sup 11}B+{sup 76}Ge with E=50 MeV at the XTU tandem accelerator of the LNL Legnaro. Based on a {gamma}-coincidence experiment using the spectrometer GASP we have found magnetic dipole bands in each studied nuclide. The regular M1 bands observed in the odd-odd nuclei {sup 82}Rb and {sup 84}Rb include B(M1)/B(E2) ratios decreasing smoothly with increasing spin in a range of 13{sup -}{<=}J{sup {pi}}{<=}16{sup -}. These bands are interpreted in the tilted-axis cranking model on the basis of four-quasiparticle configurations of the type {pi}(fp){pi}g{sub 9/2}{sup 2}{nu}g{sub 9/2}. This is the first evidence of magnetic rotation in the A{approx_equal}80 region. In contrast, the M1 sequences in the odd-even nucleus {sup 83}Rb are not regular, and the B(M1)/B(E2) ratios show a pronounced staggering.

  5. Collaborative Simulation and Testing of the Superconducting Dipole Prototype Magnet for the FAIR Project

    NASA Astrophysics Data System (ADS)

    Zhu, Yinfeng; Zhu, Zhe; Xu, Houchang; Wu, Weiyue

    2012-08-01

    The superconducting dipole prototype magnet of the collector ring for the Facility for Antiproton and Ion Research (FAIR) is an international cooperation project. The collaborative simulation and testing of the developed prototype magnet is presented in this paper. To evaluate the mechanical strength of the coil case during quench, a 3-dimensional (3D) electromagnetic (EM) model was developed based on the solid97 magnetic vector element in the ANSYS commercial software, which includes the air region, coil and yoke. EM analysis was carried out with a peak operating current at 278 A. Then, the solid97 element was transferred into the solid185 element, the coupled analysis was switched from electromagnetic to structural, and the finite element model for the coil case and glass-fiber reinforced composite (G10) spacers was established by the ANSYS Parametric Design Language based on the 3D model from the CATIA V5 software. However, to simulate the friction characteristics inside the coil case, the conta173 surface-to-surface contact element was established. The results for the coil case and G10 spacers show that they are safe and have sufficient strength, on the basis of testing in discharge and quench scenarios.

  6. Design and realization of a two-dimensional spatial magnetic field mapping apparatus to measure magnetic fields of metamaterials

    NASA Astrophysics Data System (ADS)

    Jiang, Quan; Zhou, Xiao Yang; Chin, Jessie Yao; Cui, Tie Jun

    2011-07-01

    The two-dimensional (2D) spatial electric-field mapping apparatus [Opt. Express 14, 8694 (2006)] plays an important role in experiments involving metamaterials, such as the verification of free-space and ground-plane invisibility cloaks. However, such an apparatus is valid only for the transverse-electric (TE) mode and is invalid for the transverse-magnetic (TM) mode, as it requires perfectly magnetic conducting (PMC) planes, which do not exist in nature. In this paper, we propose a 2D spatial magnetic-field mapping apparatus based on artificial magnetic conductor (AMC) plates. The AMC structure is designed using periodically perfectly electrical conducting patches with a sub-wavelength size on a dielectric substrate backed with the ground plane, which can simulate a PMC plane. Using two parallel PMC plates to form a TM-wave planar waveguide, we realize the 2D spatial magnetic-field mapping apparatus in order to measure the external and internal magnetic fields of metamaterials. Two types of excitations, a plane-wave source and a magnetic dipole, are used to feed the system. In order to validate the performance of the magnetic-field mapper, two gradient-index metamaterial lenses are measured, and the experimental results are in good agreement with the full-wave simulations.

  7. 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

  8. Analysis of the structure of Saturn's magnetic field using charged particle absorption signatures

    SciTech Connect

    Chenette, D.L.; Davis, L. Jr.

    1982-07-01

    A new technique is derived for determining the structure of Saturn's magnetic field. This technique uses the observed positions of charged particle absorption signatures due to the satellites and rings of Saturn to determine the parameters of an axially symmetric, spherical harmonic model of the magnetic field using the method of least squares. Absorption signatures observed along the Pioneer 11, Voyager 1, and Voyager 2 spacecraft trajectories are used to derive values for the orientation of the magnetic symmetry axis relative to Saturn's axis of rotation, the axial displacement of the center of the magnetic dipole from the center of Saturn, and the magnitude of the external field component. Comparing these results with the magnetic field model parameters deduced from analyses of magnetometer data leads us to prefer models that incorporate a northward offset of the dipole center by about 0.05 R/sub s/.

  9. An analysis of the structure of Saturn's magnetic field using charged particle absorption signatures

    SciTech Connect

    Chenette, D.L.; Davis, L. Jr.

    1983-06-01

    A technique is derived for determining the structure of Saturn's magnetic field. This technique uses the observed positions of charged particle absorption signatures due to the satellites and rings of Saturn to determine the parameters of an axially symmetric, spherical harmonic model of the magnetic field using the method of least squares. Absorption signatures observed along the Pioneer 11, Voyager 1, and Voyager 2 spacecraft trajectories are used to derive values for the orientation of the magnetic symmetry axis relative to Saturn's axis of rotation, the axial displacement of the center of the magnetic dipole from the center of Saturn, and the magnitude of the external field component. A comparison of these results with the magnetic field model parameters deduced from analyses of magnetometer data supports models which incorporate a northward offset of the dipole center by about 0.05 R(3).

  10. Effects of electric field on structures and dynamics in a two-dimensional dust dipole particle system

    NASA Astrophysics Data System (ADS)

    Hou, X. N.; Liu, Y. H.; Huang, F.; Jiang, S. Z.; Chen, Z. Y.; Zhang, R. Y.

    2016-09-01

    Effects of radial electric field on the structures and dynamics of dust dipoles are studied by molecular dynamics simulations. The dipoles' configuration and mean distance to the system center are used to illustrate the structures of the whole system. It is shown that the dipole particles can arrange themselves into ring-like structures in the absence of external electric field, which can gradually transform to vortex, and then to radial arrangement with the increase of the strength of electric field. The trajectories, mean square displacement, and the mean speed in radial and tangential directions of dipoles are investigated to depict the effects of the radial electric filed on the collective motion of dust dipolar particles, which are closely associated with the growth of dust particle, especially for the formation of rod-like and some other complex fractal dust particles.

  11. The effect of surface dipoles and of the field generated by a polarization gradient on the repulsive force.

    PubMed

    Huang, Haohao; Manciu, Marian; Ruckenstein, Eli

    2003-07-01

    Double-layer and hydration interactions have been coupled into a single set of equations because both are dependent on the polarization of the water molecules. The coupled equations involve the electric fields generated by the surface charge and surface dipoles, as well as the field due to the neighboring dipoles in water. The dipoles on the surface are generated through the counterions' binding to sites of opposite charge. The equations obtained were employed to explain the restabilization observed experimentally at large ionic strengths for colloidal particles on which protein molecules were adsorbed. Polar molecules adsorbed on a charged surface of colloidal particle can generate a field either in the same direction as that generated by the charge or in the opposite direction. The effect of the sign of the dipole of the adsorbed polar molecules on the interaction between surfaces was also examined.

  12. Quasistatic dipole in magnetized plasma in resonance frequency band. Response of the receiving antenna, and charge distribution on the antenna wire

    NASA Astrophysics Data System (ADS)

    Chugunov, Yu. V.; Shirokov, E. A.

    2016-05-01

    The paper discusses issues related to the radiation and reception of quasi-electrostatic waves by short antennas in resonance conditions (in the whistler range) in magnetized plasma. First, the response of the receiving antenna on the incident field of slow quasipotential waves is analyzed. It made it possible to explain in detail the results of the two-point rocket experiment OEDIPUS-C in the Earth's ionosphere. Second, the problem of the charge distribution along the short transmission (reception) dipole antenna is considered. The corresponding integral equation is obtained and solved analytically. The impedance of the antenna is found. It is shown that in the majority of cases, charge distribution along the dipole length can be considered constant.

  13. 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.

  14. 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.

  15. 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.

  16. Magnetic field studies by voyager 1: preliminary results at saturn.

    PubMed

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

    1981-04-10

    Magnetic field studies by Voyager 1 have confirmed and refined certain general features of the Saturnian magnetosphere and planetary magnetic field established by Pioneer 11 in 1979. The main field of Saturn is well represented by a dipole of moment 0.21 +/- 0.005 gauss-R(s)(3) (where 1 Saturn radius, R(s), is 60,330 kilometers), tilted 0.7 degrees +/- 0.35 degrees from the rotation axis and located within 0.02 R(s) of the center of the planet. The radius of the magnetopause at the subsolar point was observed to be 23 R(s) on the average, rather than 17 R(s). Voyager 1 discovered a magnetic tail of Saturn with a diameter of approximately 80 R(s). This tail extends away from the Sun and is similar to type II comet tails and the terrestrial and Jovian magnetic tails. Data from the very close flyby at Titan (located within the Saturnian magnetosphere) at a local time of 1330, showed an absence of any substantial intrinsic satellite magnetic field. However, the results did indicate a very well developed, induced magnetosphere with a bipolar magnetic tail. The upper limit to any possible internal satellite magnetic moment is 5 x 10(21) gauss-cubic centimeter, equivalent to a 30-nanotesla equatorial surface field.

  17. Constraints on exotic dipole-dipole couplings between electrons at the micron scale

    NASA Astrophysics Data System (ADS)

    Kotler, Shlomi; Ozeri, Roee; Jackson Kimball, Derek

    2015-05-01

    Until recently, the magnetic dipole-dipole coupling between electrons had not been directly observed experimentally. This is because at the atomic scale dipole-dipole coupling is dominated by the exchange interaction and at larger distances the dipole-dipole coupling is overwhelmed by ambient magnetic field noise. In spite of these challenges, the magnetic dipole-dipole interaction between two electron spins separated by 2.4 microns was recently measured using the valence electrons of trapped Strontium ions [S. Kotler, N. Akerman, N. Navon, Y. Glickman, and R. Ozeri, Nature 510, 376 (2014)]. We have used this measurement to directly constrain exotic dipole-dipole interactions between electrons at the micron scale. For light bosons (mass 0.1 eV), we find that coupling constants describing pseudoscalar and axial-vector mediated interactions must be | gPegPe/4 πℏc | <= 1 . 5 × 10-3 and | gAegAe/4 πℏc | <= 1 . 2 × 10-17 , respectively, at the 90% confidence level. These bounds significantly improve on previous constraints in this mass range: for example, the constraints on axial-vector interactions are six orders of magnitude stronger than electron-positron constraints based on positronium spectroscopy. Supported by the National Science Foundation, I-Core: the Israeli excellence center, and the European Research Council.

  18. The Effects of Ion heating in Martian Magnetic Crustal Fields: Particle Tracing and Ion Distributions

    NASA Astrophysics Data System (ADS)

    Fowler, C. M.; Andersson, L.

    2014-12-01

    Ion heating is a process that may allow low energy ions within the Martian ionosphere to be accelerated and escape. Ion heating can be especially efficient if the ions stay in the heating region for long time durations. With this in mind, the magnetic crustal field regions on Mars are particularly interesting. We focus on ions present within these regions, where changes in magnetic field strength and direction can heat these ions. Since crustal magnetic fields can maintain a trapped particle population it is unclear how efficiently plasma can be built up that can later escape to space. We investigate here two drivers: rotation of the planet and the solar wind pressure. As crustal fields rotate from the wake of the planet to the sub solar point and back, they experience compression and expansion over time scales of ~24 hours. The solar wind pressure on the other hand can cause variations over much shorter time scales (minutes). The effect of these two drivers using a particle tracing simulation that solves the Lorentz force is presented. O+ ions are seeded within the simulation box. The magnetic environment is a linear sum of a dipole field and a solar wind magnetic field. The dipole field represents the magnetic crustal field and the dipole strength is chosen to be consistent with MGS magnetometer observations of Martian crustal field regions. By increasing the solar wind strength the magnetic dipole is compressed. Decreasing solar wind strength allows the dipole to expand. Small magnitude, short time scale variations can be imposed over the top of this larger variation to represent short time scale solar wind variations. Since the purpose of this analysis is to understand the changes of the ion distribution inside the crustal field, simplistic assumptions of the field outside the crustal field can be made. Initial results are presented, with the focus on two main questions: (a) can low energy ions be heated and escape the closed dipole field lines as a result of

  19. Detecting and modelling the magnetic field of the β Cephei star V 2052 Ophiuchi

    NASA Astrophysics Data System (ADS)

    Neiner, C.; Alecian, E.; Briquet, M.; Floquet, M.; Frémat, Y.; Martayan, C.; Thizy, O.; Mimes Collaboration

    2012-01-01

    Aims: Following the indirect detection of a magnetic field in the β Cephei star V 2052 Oph by Neiner and collaborators in 2003 with the Musicos spectropolarimeter, we remeasured the magnetic field of this star to attempt to directly confirm the detection of a magnetic field and study its configuration in greater detail. Methods: We used the Narval spectropolarimeter installed at TBL (Pic du Midi, France), which is about 20 times more efficient than the Musicos spectropolarimeter. We applied the least-squares deconvolution (LSD) technique to various groups of lines to measure the circular polarisation of the light coming from V 2052 Oph. We synthesized the measured Stokes V profiles with a centred and off-centred dipole model. Results: For the first time, we clearly detect the Zeeman signature in the Stokes V profiles of V 2052 Oph and thus directly prove the presence of a magnetic field in this star. The modulation with the rotation period is also confirmed and reflects an oblique dipole field. Thanks to the small error bars on the measurements, we are able to study the behaviour of different groups of lines and the centring of the dipole in the star. We find that the dipole is most likely off-centred along the magnetic axis and that He spots are present at the surface next to the magnetic axis. Conclusions: We conclude that V 2052 Oph is a magnetic He-strong β Cep star, with a dipole field, probably off-centred, with Bpol ~ 400 G and He patches close to the magnetic poles. Based on observations obtained with the Narval spectropolarimeter at the Télescope Bernard Lyot, Observatoire du Pic du Midi, France.

  20. CesrTA Retarding Field Analyzer Measurements in Drifts, Dipoles, Quadrupoles and Wigglers

    SciTech Connect

    Calvey, J.R.; Li, Y.; Livezey, J.A.; Makita, J.; Meller, R.E.; Palmer, M.A.; Schwartz, R.M.; Strohman, C.R.; Harkay, K.; Calatroni, S.; Rumolo, G.; Kanazawa, K.; Suetsugu, Y.; Pivi, M.; Wang, L.; /SLAC

    2010-06-15

    Over the course of the CesrTA program, the Cornell Electron Storage Ring (CESR) has been instrumented with several retarding field analyzers (RFAs), which measure the local density and energy distribution of the electron cloud. These RFAs have been installed in drifts, dipoles, quadrupoles, and wigglers; and data have been taken in a variety of beam conditions and bunch configurations. This paper will provide an overview of these results, and give a preliminary evaluation of the efficacy of cloud mitigation techniques implemented in the instrumented vacuum chambers.

  1. Asteroseismology can reveal strong internal magnetic fields in red giant stars.

    PubMed

    Fuller, Jim; Cantiello, Matteo; Stello, Dennis; Garcia, Rafael A; Bildsten, Lars

    2015-10-23

    Internal stellar magnetic fields are inaccessible to direct observations, and little is known about their amplitude, geometry, and evolution. We demonstrate that strong magnetic fields in the cores of red giant stars can be identified with asteroseismology. The fields can manifest themselves via depressed dipole stellar oscillation modes, arising from a magnetic greenhouse effect that scatters and traps oscillation-mode energy within the core of the star. The Kepler satellite has observed a few dozen red giants with depressed dipole modes, which we interpret as stars with strongly magnetized cores. We find that field strengths larger than ~10(5) gauss may produce the observed depression, and in one case we infer a minimum core field strength of ≈10(7) gauss. PMID:26494754

  2. Asteroseismology can reveal strong internal magnetic fields in red giant stars.

    PubMed

    Fuller, Jim; Cantiello, Matteo; Stello, Dennis; Garcia, Rafael A; Bildsten, Lars

    2015-10-23

    Internal stellar magnetic fields are inaccessible to direct observations, and little is known about their amplitude, geometry, and evolution. We demonstrate that strong magnetic fields in the cores of red giant stars can be identified with asteroseismology. The fields can manifest themselves via depressed dipole stellar oscillation modes, arising from a magnetic greenhouse effect that scatters and traps oscillation-mode energy within the core of the star. The Kepler satellite has observed a few dozen red giants with depressed dipole modes, which we interpret as stars with strongly magnetized cores. We find that field strengths larger than ~10(5) gauss may produce the observed depression, and in one case we infer a minimum core field strength of ≈10(7) gauss.

  3. Gas-phase NMR measurements, absolute shielding scales, and magnetic dipole moments of 29Si and 73Ge nuclei.

    PubMed

    Makulski, W; Jackowski, K; Antusek, A; Jaszuński, M

    2006-10-12

    New gas-phase NMR measurements of the shielding constants of 29Si, 73Ge, and 1H nuclei in SiH4 and GeH4 are reported. The results, extrapolated to zero density, provide accurate isolated molecule values, best suited for comparison with theoretical calculations. Using the recent ab initio results for these molecules and the measured chemical shifts, we determine the absolute shielding scales for 29Si and 73Ge. This allows us to provide new values of the nuclear magnetic dipole moments for these two nuclei; in addition, we examine the dipole moments of 13C and 119Sn.

  4. Modeling the Jovian magnetic field and its secular variation using all available magnetic field observations

    NASA Astrophysics Data System (ADS)

    Ridley, Victoria A.; Holme, Richard

    2016-03-01

    We present new models of Jupiter's internal magnetic field and secular variation from all available direct measurements from three decades of spacecraft observation. A regularized minimum norm approach allows the creation of smooth, numerically stable models displaying a high degree of structure. External field from the magnetodisk is modeled iteratively for each orbit. Jupiter's inner magnetosphere is highly stable with time, with no evidence for variation with solar activity. We compare two spherical harmonic models, one assuming a field constant in time and a second allowing for linear time variation. Including secular variation improves data fit with fewer additional parameters than increasing field complexity. Our favored solution indicates a ˜0.012% yr-1 increase in Jupiter's dipole magnetic moment from 1973 to 2003; this value is roughly one quarter of that for Earth. Inaccuracies in determination of the planetary reference frame cannot explain all the observed secular variation. Should more structure be allowed in the solutions, we find the northern hemispherical configuration resembles recent models based on satellite auroral footprint locations, and there is also evidence of a possible patch of reversed polar flux seen at the expected depth of the dynamo region, resembling that found at Earth and with implications for the Jovian interior. Finally, using our preferred model, we infer flow dynamics at the top of Jupiter's dynamo source. Though highly speculative, the results produce several gyres with some symmetry about the equator, similar to those seen at Earth's core-mantle boundary, suggesting motion on cylinders aligned with the rotation axis.

  5. The design and construction of high field-uniformity permanent magnet system for MRI

    SciTech Connect

    Feng, Z.X.; Jiang, X.H.; Han, S. )

    1992-01-01

    This paper reports that the permanent magnet system used for MRI has some advantages: the lower cost/field ratio in the range of magnetic field 1.5-3.0 kG; no need power supply and cryogenic equipment. So, the MRI device with a permanent magnet system has marketable value. The MRI device requires a high field-uniformity magnet system. The necessary field-uniformity is better than several tens of ppm in a 30 cm diameter spherical volume. Generally, the shim coils can be used for correcting the magnetic field in working area, but the authors developed a passive method to correct the field-uniformity. First, the specially designed ferromagnetic pole pieces are disposed onto the surfaces of the main permanent magnet poles to improve the field-uniformity preliminarily. Then, the necessary field-uniformity will be obtained by using the magneto-dipoles which are suitably placed in the field domain.

  6. A comparison of least squares linear regression and measurement error modeling of warm/cold multipole correlation in SSC prototype dipole magnets

    SciTech Connect

    Pollock, D.; Kim, K.; Gunst, R.; Schucany, W.

    1993-05-01

    Linear estimation of cold magnetic field quality based on warm multipole measurements is being considered as a quality control method for SSC production magnet acceptance. To investigate prediction uncertainties associated with such an approach, axial-scan (Z-scan) magnetic measurements from SSC Prototype Collider Dipole Magnets (CDM`s) have been studied. This paper presents a preliminary evaluation of the explanatory ability of warm measurement multipole variation on the prediction of cold magnet multipoles. Two linear estimation methods are presented: least-squares regression, which uses the assumption of fixed independent variable (xi) observations, and the measurement error model, which includes measurement error in the xi`s. The influence of warm multipole measurement errors on predicted cold magnet multipole averages is considered. MSD QA is studying warm/cold correlation to answer several magnet quality control questions. How well do warm measurements predict cold (2kA) multipoles? Does sampling error significantly influence estimates of the linear coefficients (slope, intercept and residual standard error)? Is estimation error for the predicted cold magnet average small compared to typical variation along the Z-Axis? What fraction of the multipole RMS tolerance is accounted for by individual magnet prediction uncertainty?

  7. 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.

  8. Analysis of Electric Field Induced by ELF Magnetic Field Utilizing Generalized Equivalent Multipole-Moment Method

    NASA Astrophysics Data System (ADS)

    Hamada, Shoji; Yamamoto, Osamu; Kobayashi, Tetsuo

    This paper presents a generalized equivalent multipole-moment method for calculating three-dimensional Laplacian fields in multi-spherical system. The Greengard & Rokhlin's M2M, M2L, and L2L formulae enable the multipole-moment method to calculate the fields in general arrangement of multi-spheres, which involve exclusive and multi-layered spherical arrangement. We applied this method to electric field calculation in biological structures induced by ELF magnetic fields. The induced electric fields in a three eccentric and exclusive spheres system, which models human head with two eyeballs, are calculated under the application of homogeneous and magnetic-dipole fields. The validity of this method is successfully confirmed by comparing the calculated fields with those by the fast-multipole surface-charge-simulation method.

  9. Terahertz radiation-induced sub-cycle field electron emission across a split-gap dipole antenna

    NASA Astrophysics Data System (ADS)

    Zhang, Jingdi; Zhao, Xiaoguang; Fan, Kebin; Wang, Xiaoning; Zhang, Gu-Feng; Geng, Kun; Zhang, Xin; Averitt, Richard D.

    2015-12-01

    We use intense terahertz pulses to excite the resonant mode (0.6 THz) of a micro-fabricated dipole antenna with a vacuum gap. The dipole antenna structure enhances the peak amplitude of the in-gap THz electric field by a factor of ˜170. Above an in-gap E-field threshold amplitude of ˜10 MV/cm-1, THz-induced field electron emission is observed as indicated by the field-induced electric current across the dipole antenna gap. Field emission occurs within a fraction of the driving THz period. Our analysis of the current (I) and incident electric field (E) is in agreement with a Millikan-Lauritsen analysis where log (I) exhibits a linear dependence on 1/E. Numerical estimates indicate that the electrons are accelerated to a value of approximately one tenth of the speed of light.

  10. Terahertz radiation-induced sub-cycle field electron emission across a split-gap dipole antenna

    SciTech Connect

    Zhang, Jingdi; Averitt, Richard D. E-mail: raveritt@ucsd.edu; Zhao, Xiaoguang; Fan, Kebin; Wang, Xiaoning; Zhang, Xin E-mail: raveritt@ucsd.edu; Zhang, Gu-Feng; Geng, Kun

    2015-12-07

    We use intense terahertz pulses to excite the resonant mode (0.6 THz) of a micro-fabricated dipole antenna with a vacuum gap. The dipole antenna structure enhances the peak amplitude of the in-gap THz electric field by a factor of ∼170. Above an in-gap E-field threshold amplitude of ∼10 MV/cm{sup −1}, THz-induced field electron emission is observed as indicated by the field-induced electric current across the dipole antenna gap. Field emission occurs within a fraction of the driving THz period. Our analysis of the current (I) and incident electric field (E) is in agreement with a Millikan-Lauritsen analysis where log (I) exhibits a linear dependence on 1/E. Numerical estimates indicate that the electrons are accelerated to a value of approximately one tenth of the speed of light.

  11. Influences of different parameters on the microstructure of magnetic-field-induced self-assembled film

    NASA Astrophysics Data System (ADS)

    Dan, X.; Yang, J. J.

    2016-07-01

    Self-assembled films with needle-like microarrays were fabricated using a mixture of cobalt and fluorocarbon resin under a magnetic field. The various influences of magnetic powder content, viscosity and size distribution on the structure of the self-assembled films were investigated. The self-assembled film morphologies were characterized by stereomicroscope and scanning electron microscopy. Experimental results indicate that an increase in magnetic powder content results in greater unit height and diameter, and that a reduction in viscosity results in increasing array density and decreasing unit width. Additionally, particles with narrow size distribution were able to attain more regular microarray structures. The structural alterations were closely related to numerous effects such as van der Waals forces, dipole-dipole interactions, and external-dipole interactions. The self-assembled film demonstrated magnetic anisotropy, as identified by vibrating sample magnetometry (VSM).

  12. Magnetic-dipole transition probabilities in B-like and Be-like ions

    SciTech Connect

    Tupitsyn, I. I.; Glazov, D. A.; Volotka, A. V.; Shabaev, V. M.; Plunien, G.; Crespo Lopez-Urrutia, J. R.; Lapierre, A.; Ullrich, J.

    2005-12-15

    The magnetic-dipole transition probabilities between the fine-structure levels (1s{sup 2}2s{sup 2}2p) {sup 2}P{sub 1/2}-{sup 2}P{sub 3/2} for B-like ions and (1s{sup 2}2s2p) {sup 3}P{sub 1}-{sup 3}P{sub 2} for Be-like ions are calculated. The configuration-interaction method in the Dirac-Fock-Sturm basis is employed for the evaluation of the interelectronic-interaction correction with negative-continuum spectrum being taken into account. The 1/Z interelectronic-interaction contribution is derived within a rigorous QED approach employing the two-time Green function method. The one-electron QED correction is evaluated within framework of the anomalous magnetic-moment approximation. A comparison with the theoretical results of other authors and with available experimental data is presented.

  13. 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.

  14. A 25 T dipole pulsed magnet to study the magnetic birefringence of vacuum: the BMV project

    NASA Astrophysics Data System (ADS)

    Askenazy, S.; Billette, J.; Dupré, P.; Ganau, P.; Mackowski, J.; Marquez, J.; Pinard, L.; Portugall, O.; Ricard, D.; Rikken, G. L. J. A.; Rizzo, C.; Trenec, G.; Vigué, J.

    2001-04-01

    The existence of a magnetic birefringence of vacuum is one of the most important predictions of quantum electrodynamics, which has not yet been verified. In this contribution, we present a new project, the BMV (Biréfringence Magnétique du Vide) project, a collaboration between different Grenoble, Lyon and Toulouse institutes. The proposed experimental set-up, compared to previous attempts, should improve the signal level by about two orders of magnitude. Keystones of the proposed set-up are a very sensitive ellipsometer and a specially designed 1.5 m long 25 T pulsed magnet, which is under development in Toulouse, France.

  15. DEVELOPMENT OF A PRECISE MAGNETIC FIELD MEASUREMENT SYSTEM FOR FAST-CHANGING MAGNETIC FIELDS.

    SciTech Connect

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

    2003-06-15

    Several recent applications for fast ramped magnets have been found that require precise measurement of the time-dependent fields. In one instance, accelerator dipoles will be ramped at 1 T/sec, with measurements needed to the typical level of accuracy for accelerators, {Delta} B/B better than 0.01%. To meet this need, we have begun development of a system containing 16 stationary pickup windings that will be sampled at a high rate. It is hoped that harmonics through the decapole can be measured with this system. Precise measurement of the time-dependent harmonics requires that both the pickup windings and the voltmeters be nearly identical. To minimize costs, printed circuit boards are being used for the pickup windings and a combination of amplifiers and ADC's for voltmeters. In addition, new software must be developed for the analysis. The paper will present a status report on this work.

  16. 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.

  17. Transverse Magnetic Field Propellant Isolator

    NASA Technical Reports Server (NTRS)

    Foster, John E.

    2000-01-01

    An alternative high voltage isolator for electric propulsion and ground-based ion source applications has been designed and tested. This design employs a transverse magnetic field that increases the breakdown voltage. The design can greatly enhance the operating range of laboratory isolators used for high voltage applications.

  18. Two-dimensional colloidal mixtures in magnetic and gravitational fields

    NASA Astrophysics Data System (ADS)

    Löwen, H.; Horn, T.; Neuhaus, T.; ten Hagen, B.

    2013-11-01

    This mini-review is concerned with two-dimensional colloidal mixtures exposed to various kinds of external fields. By a magnetic field perpendicular to the plane, dipole moments are induced in paramagnetic particles which give rise to repulsive interactions leading to complex crystalline alloys in the composition-asymmetry diagram. A quench in the magnetic field induces complex crystal nucleation scenarios. If exposed to a gravitational field, these mixtures exhibit a brazil-nut effect and show a boundary layering which is explained in terms of a depletion bubble picture. The latter persists for time-dependent gravity ("colloidal shaking"). Finally, we summarize crystallization effects when the second species is frozen in a disordered matrix which provides obstacles for the crystallizing component.

  19. Mercury's Surface Magnetic Field Determined from Proton-Reflection Magnetometry

    NASA Technical Reports Server (NTRS)

    Winslow, Reka M.; Johnson, Catherine L.; Anderson, Brian J.; Gershman, Daniel J.; Raines, Jim M.; Lillis, Robert J.; Korth, Haje; Slavin, James A.; Solomon, Sean C.; Zurbuchen, Thomas H.; Zuber, Maria T.

    2014-01-01

    Solar wind protons observed by the MESSENGER spacecraft in orbit about Mercury exhibit signatures of precipitation loss to Mercury's surface. We apply proton-reflection magnetometry to sense Mercury's surface magnetic field intensity in the planet's northern and southern hemispheres. The results are consistent with a dipole field offset to the north and show that the technique may be used to resolve regional-scale fields at the surface. The proton loss cones indicate persistent ion precipitation to the surface in the northern magnetospheric cusp region and in the southern hemisphere at low nightside latitudes. The latter observation implies that most of the surface in Mercury's southern hemisphere is continuously bombarded by plasma, in contrast with the premise that the global magnetic field largely protects the planetary surface from the solar wind.

  20. Formation of electric dipoles in pea stem tissue due to an electric field

    NASA Astrophysics Data System (ADS)

    Ahmadi, Fatemeh; Farahani, Elham

    2016-07-01

    For examining the effect of an electrical field (DC) on pea seed, we exposed the pea seeds to electric fields with intensities 1, 4 and 7 kV/cm for 30, 230, 430 and 630 seconds. The tests were repeated three times, and each iteration had 5 seeds. Then, the seeds were moved to packaged plates. Finally, microscopic observation of the pea stem tissue showed that the application of a DC electrical field caused a deformation in the pea stem tissue. The results led us to examine the deformation of the tissue theoretically and to address that deformation as an electrostatic problem. In this regard, we modeled the pea stem based on the formation of electric dipoles. Then, theoretically, we calculated the force acting on each xylem section by coding, and the results were consistent with the experimental data.